/ ( I m [.lULV 25, 18S4.] i CONDUCTED BY RICHARD A. PROCTOR. •TOP " Let Knowledge grow from more to more." — Tennyson. TOLUME T. JANUARY TO JUNE. 1884. LONDON: WYMAN & SONS, 74-76, GEEAT QUEEN STREET, LINCOLN'S-IXX FIELDS, W.C. 1S81. ^ Ky ^, c 'D July 25, 1SS4. ♦ KNOWLEDGE INDEX TO VOLUME Y. GENERAI,. Address to readers, 102 Adelaide Eveniners, Mr. liVilliam, and the management of his journal, 463 Cheltenhum Examiner, the, and Mr. Proctor, 355 Chemistrv of cookery, the, 18, 49, 81, 123, 156, 196, 238, 301, 342, 406, 4t7 Chess column, remarks on arrangement of, 209 •Chess column: book, 15 ; observations, 32; gambits of the king, 43 ; an unsound but amusing game, 154; abit of Morphy, 174; blind-fold chess on the Stock Exchange, 194; a singular ending, 315; Scotch gambit attack, 215; easy notes on the openings, 254, 2!i9, 339; home chess play, 331; John Ruskin on chess, 446 ; observations on chess- players, 467 ; see also 62, 73, 92, 106, 120, 134, 235, 273, 319, 361, 404, 426 Christmas car[r]ol[l] on the endowment of research, a, 23 Christmas happiness, 10 Clevenger, Dr., theory of, as to man's erect position. 313 Clodd, Edward : among the Indians of Guiana (review) , 45, 139 ; dreams, their place in the growth of primitive belief (introductory), 384, 429, 469 Coincidences and superstitions, 195, 237, 230, 326, 367 College eight -oared races at (Cambridge, 207 Collisions, astronomical, 2 Collisions of ocean steamers, and how to avert them. 354 ' Common newt, the, 321 Constellations, map of (illustrated), 347 Cookery, the chemistry of, 18, 49, 81, 123, 156, 196, 338, 3tH. 342, 416, «7 Cook, Robert B. : causes of the glacial period, 38, 108, 193. 258 Copyright in lectures, 305 Corona of the sun, the latest scientific discoyeries concerning the, 257 Corpulence, the tUirst-cure for, 386 Creation, vestiges of (review), 329 Cremation Bill and Colonel King-HanuoD, 332; see also 346 Cricket, observations on, 397 Cricket, the uncertainty of, 374 Cycling and cycles, 266 Dancixg to death, 21 Day-sign for February, the (illustrated) , 87: for March (illustrated), 207 Deaf-mutism and a belief in a Supreme Being, 332 Death, dancing to, 21 Dickens, story of, left half-told ("Edwin Drood"),478 Discovery of prehistoric remains in Lincolnshire, the, 333 Divided skirt, the. 428 Domestic instinct in the cat, permanence of the, 243 Double personality, 5 Double stars (illustrated), -108 Drawbaugh, Daniel, reference to, as an alleged inventor of the telephone, 128 Drawing the planets (illustrated), 85 Dreams, their place in the {;^owth of primitiye beliefs (introductory), 334, 429, 469 Dress reform (ladies'), 419 Drink, how we (illustrated), 223 Dust envelope of the earth, SO Dynamite outrages, the, 413 Eabth, path of, round the sun (illostrated), 41 Earthquake, the, 301 Easter, observations on, 273 Edinburgh fft>pi>icand the Speneerian philosophy, the, 63, 33; Mr, Spencer's first principles, 147 Education electrical, 437 Edwards, Amelia B.: the migrations of birds, 41 Effect of marriage on life, 17, 33 Effects of the glacial period, inorganic effects, 193 ; organic period, 258 Electrical education, 4.37 Electrician, the amateur (batteries), 4, 353, 411 Electric projectors on board yachts, 473 Electro-plating, 161, 201, 243," 307, 365, 459 Emotions, in infants, the, 67 Encyclopsedia, the American (review), 84 Endowment of research, a Christmas Car^rloiril on the, 23 - J - -> Entomology of a pond, the (illustrated), 373, 414, 449, Evidences of the glacial period, 6 Evolution, 260 Evolution of flowers, the (illustrated) : the starting point, 64 ; first steps, 114; integration begins, 137 ; side branches, 175 ; true lilies, 220 ; tulip and fritillary, 290 ; lilies and rushes, 386 Extinction of species, the, 427 Extraordinary sunsets, the, 155, 177 Face of the sky: January 4 to January 18, 13; January 18 to February 1, 46 ; February 1 to February 15, 75 ; February 15 to February 29 103 ■ February 29 to March 14,"131; March 14 to March 33, 167 : March 28 to April 11, 210; April 11 to April 25, 243 ; April 25 to May 9, 294 ; Mav 9 to May 23, 333 ; May 23 to June 6, 370 ; June 6 to June 20, 421 ; June 30 to July 4, 462 February, the ni^ht-sign for (illustrated), 70; the day-signs for (illustraTfd), 87 Few Saturnal observations, a (illustrated), 185, 202 Flat earth and her moulder, the, 213 Flies, ichneumon (illustrated), 344, 237 Flowers, the evolution of (illustrated) : the starting point. 64; first steps, 114 ; integration begins, 137; side branches, 175 ; true lilies, 220 ; tulip and fritillary, 296 ; lilies and rushes, 336 Flying-mjtchines, notes on, 221, 470 Foster, Thomas : Christmas happiness, 10 ; the morality of happiness— self r. others, 47, 69 ; care for self as a duty, 95, 122,163,204; care for others as a duty, 240, 233, 34.3, 391, 452 Foster, Thomas : Dickens's story left half-told, 478 Foucault, pendulum experiments of (illustrated), 413 Gamblixg superstitions, 11, 19, 50, 79, 107, 136 Ghosts and goblins, 65, 94, 131, 178, 217 G;ant sun, the movement? of a, 405 Glacial period, evidences of the, 6; causes of, 39,108; effects of, 193; organic effects, 3>3 Goblins and ghosts. 65, 94, 121, 173, 217 Goethe ; hymn on the universe, 267 Grand Canon district, the (illustrated) , 458 Gratacap, L. P. : the omithorhynchus (illustrated). Gravity, the mystery of, 176 Great £astem, the, and her destiny, 166 Great novelists, remarks on, 272 Greek fire, 35 Greenwood, H., M.A. : copyright in lectures, 305 Guiana, among the Indians of (review), 45, 139 Gulf Stream, the, 393 Happctess, Christmas, 10 Happiness, the morality of: self r. others, 37, 69; care for self as a duty, 95, 122, 163, 20*; care of others as a duty, 241, 476 Hints on rowing, 219 How to choose a tricycle, 22, 54 How to get strong, 135 ; the muscles of the waist, 158 ; to strengthen the muscles of the luius, 200,243; the muscles of the legs, 379; the muscles of the upper thigh, 323 ; from knee to toes, 366 How to make useful star-maps (illustrated), 5, 36, 110, 146 How to select a life assurance office, 265, 303 How we drink (illustrated), 223 Hydrophobia, cure for, by M. Pasteur, 374 Hymn on the xmiverse, 267 ICHiTEriiox-FLrES (illustrated), 244, 237 India as a source of food-supply, 453 Indianapolis, danger of Mr. Proctor when lecturing at, through defective lime-light arrangements, 203 Indians of Guiana, among the, 139 Infants, the emotions in, 67 Intelligence in a pointer, 183 International Health Exhibition, the (introductory), 337, 415, 434, 454, 476 Irving, Mr. Henry, in America, 190 Irving, Mr., on actors, 355 Jeffebibs, Richard : sea-clouds, 475 " Jerry Mander," meaning of a, 117 Joule, the scientific papers of Dr. (review), 245 Jupiter in a three-inch telescope (illustrated), 101, 126 KiKG, Helen Atixilium : Let knowledge grow from more to more (poetry), 138 KxowLBDGB, proposal for enlargement of, 102 Krakatoa dust-cloud, spread of the, 261 Lanb, river action on, 270 Langley, Prof. S. P. : our earth's dust envelope, 80 Lectures, copyright in, 305 Lessons, almanack (illustrated), 23 Let knowledge grow from more to more (poetry), 188 Life assurance office, how to select a, 365, 308 Life in Mars, 303, 343 Life, the effect of marriage on, 17, 33 Lime-light apparatus, explosion of, 308 Mapping, notes on, 133 Marmoset, a tame, 443 Marriage, the effect of, on life, 17, 33 ; marriage and madness, 137 ^lars in a three-inch telescope (illustrated) , 140 Mars, the planet (illustrated), 8, 3S1 ; Mars in oppo- sition, 70 ; calculation of the rotation period of, 208, 369 ; life in, 303, 343 ; the satellites of, 335 Marsk, Professor: evolution, 260 Mathematical column : hints on the solution geometrical problems, 31 ; Achilles and the tortoise, 60; easy riders on Euclid's first bool^ IV ♦ KNOWLEDGE ♦ [July 25, 1884. Genfral — pnittinuf.d. 172, 19J, 'iM, 25-1, 276 318. 30O, A^l, -125. 48S ; easy lessons in co-ordinat'* gcoroetry (illastrated), 172, V13. 253. 2i)-i, 339, 379, 435; easy less-^n* on Kuclid'a ttrst book, Zl4, 425; notes on Euclid's firtt l.nuk (illustrated), 153, 192, 234, 370, 31a, 359. 403. 441., 4S8 Mesnierin infl^ieiiees, demonstration of cause of, 1S9 Metric system, the, '157 Microscope, pleasant hours with the fillu«»trated), 20, 61, 82, 109, 141, 182, 2-40, 282, 330,371,430, 472 Migrations of birds, 1, 41 _ Misreprpseu'ationa concerning Mr. Richard A. Prnctor, 439 Morality of hiippiness, the: self v. others, 37, 69; oare for self as a dutv, 95, 122, 103. 204; care of others as a duty. 2W, 283, 315, 391, 452 Moved from afar : the emotions. 3i8, the will, 395 ; the seDfations, 4'^8 ; the intellect, 4:i6 Movemenrs of a tjiant sun, the, 4^)5 Muscle-reading and thought -reading, 3S3 Mystery of gravity, the, 176 Xatubai, phenomena and "signs" in olden times, 356 Nature, the unity of (review), 163 Xewspuper-i anJ the boat-race, 273 Kew btorm-cluud, Mr. Ruskin on a, 81 !Newt, the common, 331 New year, the, 10 Xiagdra, a cantilever bridge over (illustrate!), 227 !Night-sit:n for February, the (illustrated), 70, 331 >oah, the rainbow o'', -i-W) Noble, William: the recent extraordinary sunrises and sunsets, 418 Notes on books, 59 Notes on living-machines, 221, 470 Notes on mapping, lai OcciTLTATioxs in a three-inch telescope (illnstrated), 267 Opposition. Mars in (illustrated), 70 Optk-al recreations (illustrated), 3i5, 351, 399, 433, 480 Optics without mathematics (review) (illustrated), 74 Ornithorhvnchus, the (illustrated), 269 Our earth^s dust envelope, 30 Oiygen and hydrogen as explosive gases, 208 Oxyhydrogen lamp, ordinary form of an, 208 Paradox column, our: lightning, 118; the flat earth and her moulder, 213, 233 ; reference to pro- ceedings against Mr. H. Ossipotf Wolfson, 253 ; the flat earth and its flattener, 275 *' Parallax." references to character of, 313 Paateur, M., and hydrophobia, 374 Patent Act <>f iS83, the. 324. 36*^, -109 Patience and courage for the truth, 93 Payn, Air., literary reminiscenees of, 313 Payne, Professor : the satellites of Mars, 3S5 Pendulum experiments, Foueault's (illustrated). 413 Permanence of domestic instinct in the cat, 2-13 Personality, dnuble. 5 Pigeons, tumbler, 55 Planet Mars, the (illustrated), 8. 281 Planetarv movements (illustrated), 310 Planets, drawing the (illustrated), 85 Pleasant hours uith the microscope (illustrated), 20, 51, 83, 109, 141, 182, 240, 232, 330, 371, 430, 472 *' Polyglot *': the Patent Act of 1883, 324. 3(», 109 Pond", the entomology of a (illustrated), 372, 414, 419, . 474 Pointer, intelligence in a, 183 Porcupine, the Canadian (illustrated), 55 Prehistoric remains, discovery of, in Lincolnshire, 333 Problematic satellite of Venus, 452 Proctor, Richard A. ; how to make useful star-maps (illu&tratedj, 5, 36, 110, 110; the universe of suns (illustratcdj, 9, 25, 34, 56, 68, 96, 113, 1S6, 234, 281, 323,431; gambling superstitions, 11,19,50, 79, 107, 136; centrifugal force (review), 13; almanack lessons (illustrated), 23, 2u6 ; hints on the solution of geometrical problems, 31 ; zodiacal star-map for January, 40, 2^7. 395, -180 ; Achilles and the t rtoise, fiO; the Edinburgh Jtevietc and the Spencerianphilosophv, 83; ghosts and goblins, 65,91'. 121, 17S, 217; Mars in opposition (illus- trated), 70; notes on Euclid's first book (illus- trated). 152, 192, 234. 276, 318, 359, 402, 411, 483 ; easy rulers on Euclid's first book, 173, 193, 214, 264", 276. 313, 360, 402, 425, 493 : easy lessons in co-ordinate geometry (illustrated, 172, 213, 253, 298, 333, 379, 425, 466: notes on mapping, 183; coincidences and superstitions, 195, 237, 280, 336, 367; the poetry of science, 209; map of con- stellations (illustrated), 317 ; easy notes on chess op^nini.'^, 254, 299, 339; s tlar surroundings, 257; the thirst-cure for corpulence, 236; the earthquake, 301 : life in M^rs, 303, 313 ; vestiges of creation (review). 329; odd coincidences, 332; sent to the bottom. 311, 363, 389, 411 ; cremation, 346; home chess plav. 331 ; thought-reading and muscle- reading, 383 ; the movements of a giant sun, 4<15 ; Foucault's pendulum experiments, 413; the dyoamite outrages, 418; pyramid prophecies, 450: notes on flymg and ilying-machines, 470 Projectile, Mr. Proctor on the flight of a, and the Adelaide Evenbtg Journal, 293 Pyramid prophecies. 450 Rastaed. A. Cowper: (he extraordinary sunsets, 155, 177 ; the spread of the Krakatoa dunt-cIoud, 261 Reade, Charles, remarks on the late, 273 Rebuking an iiudience, 116 Recent extraordinary sunrises and simaets, the, 418 Recent lava flow on the Uinkaret, 458 Recreation in skill, 7 Recreations, optical (illustrated), 305, 351,339, 436, 480 Red after-ulow, the, 166 Red deer (review), 58 Rees, J. K. A. M. : standard time, 319 River action on land, 270 Rotation period of Mars, the, 208, 369 Kove-beellea (illuptratcd), 26 Rowing, hints on, 219 liuskin, Mr., on a new storm-cloud, 81 ; alleged inacu- racies of. 1 16 Bussell, Percy : India as a source of food-supply, 453 Sagacity and morality of plants, the (review) , 482 Sala, Mr., and his critic-*, 166; references to, 189 Satellites of Mar*, the, 335 Saturnine observations, a few (illustrated), 185, 202 Sciutilhition (illustrated), 180 Sea-clouds, 475 Sent to the bottom, 3J1, 363, 389, 411 Skill, recreaHon in, 7 Skipjacks nnd wire-worms (illustrated), 327 Sky, the face of the, from Jan. 4 to Jan. )8. 13; Jan. ' 18 to Feb. 1. 16: Fob. 1 to Feb. 15, 75; Feb. 15 to Feb. 39 103; Feb. 29 to March 14. 131 ; March 14 to March 28, 167; March 2H to April 11, 210; Apriin to April35,2l8; April 25 to Mar 9, 291; Mav 9 to May 33, 333; May 23 to June 6, 370; June 6 to June XO, 421 ; June 20 to July 4, -103 Slack, Henry J., F.G.S. : pleasant hour* with the mi- croscope (illustrated), 20, 51, 82, 109, 141, 182, 210, 282,33), :;71, 13 '. 172 Blingo. "W. : who invented the telephone? (illustrated) 128; electroplating, 161, 201, 243, 307, 365. 459; the telegraph in a gale, 263 ; electrical education, 437 Solar surroundings, 257 Song and spc-ch (review) 85 Sp»-cies, the extinction of, 427 Speech ami song (review) 85 Spencer, Mr., and the Kdinburqh TieTiev, 83, 147 ; Salience and courage of, for the truth, 93; Mr. [erbert Spencer, 332 Spenceiian philosophy and the Edinburvh Seview, the, 63 Spider-life wonders, 418 Spread of the Krakatoa dust-cload, 261 St. George's chess club, Mr. Richard A. Proctor and the, "116 Stainforth, John W. : a year's weather forecasts (the wiud). 112, 159 Standard time, 319 Star-maps, how to make them (illastrated), 5, 36, 110, 146 Stafe of Florida and the Pouema, the collision between the, 351 Strong, how to get, 135 ; the muscles of the waist, 15^ ; to strengthen the muscles of the loins, 20^, 242; the muscles of the legs, 279; the muscles of the upper thigh, 322; from knee to toes, 366 Sun, path of the earth round the (illustrated), 41 Sun, the atmosphere of the, 313 Suns, the universe of (illustrated), 9, 25, 34 56, 68, 96, 113, 186. '^2.1, 284, 323, 431 Sunrises and sunsets, the recent extraordinary, 418 Sunsets, the extraordinary, 155, 177 Superstitions and coincidences, 195. 237, 280, 326, 367 Superstitions, gambling, 11, 19, 50, 79, 107, 136 Tame marmoset, a, 419 Telegraph in a gale, the, 263 Telephone, who invented the (illustrated), 123 Tight -lacing, obser^'ations on, 293 Theory of visions, a, 43 Thirst cure for corpulence, the, 286 Thought-reading and muscle-reading, 333, 463 Three-inch telescope, Jupiter in a (illustrated), 101, 126; Mars in a, IW; occultations in a, 267; Uranus and Neptune in a, 199 Tricycle, how to choose a, 22, 54 Tricycles in 1881, 97, 142; the Tricycle Exhibition in the Agricultural Hall, 183; thetrialof the Stirling, 225 ; trying the Tandem, 238 Tricycles, trying them (illustrated), 72 Truth, patience and courage for the, 93 Tumbler pigeons, 55 Tyndall, Professor, and the Spectator^ 166 UsiTT of nature, the (review), 162 Universe, hymn on the, 267 Universe of suns (illustrated), 9,25, 34, 56, 68. 96,143 186. 224, 3^, 333, 431 Uranus and Neptune in a three-inch telescope (illus- trated), 199 Useful star-maps and how to make (illustrated), 5 Tahiatto?.' in animal?, .54 Venus, the problematic satellite of, 452 Testiges of creation (renew), 339; and Mr. Robert Chambers, 313 Visions, a theory of, 43 Weatheb forecasts for a year (the wind), 112 ; the weather, 159 Weevils (illustrated). 160, 205 Weston, allusion to the walk of, 189 Whist column : a game from »he Westminster papers, 16 ; late signals, 61 ; whist endings, 91 ; notes and' inferences, 91, 119, 193; a whiet gem, 153; skill at whist, 173; illustrative game by Mr. Lewji, 216 ; a whist-plaver's wail, 236, 255, 277 ; an illuB- trative game, 34(5; anamu^iing hand, 320 ; synopsia of the leads in plain Kuit:i, :i62 ; average players, 392 ; whist torture, 403; wonderful luck at whist, 445 ; home whist, 467 ; see also 32, 46, 77, 105,. 3J0, 489 White, C.A. : the permanence of the domestic instinct in the cat, 243 Who invented the telephone? (illustrated), 128 Woofson, H. Ossipotf : the flat earth and her moulder^ 213, 233 ; and the zetetic astronomy, 355 World-life (review),. 53 Wild bees (illustrated), 52, 99, 134 WiUiams, W. Mattieu : the chemistry of cookery, 18, 49, 81, 123, 156. 196, 23s, 301, 312, 406, 447; the- sun's atmosphere, 218 Wilson, Dr. Andrew, reference to lectures of, 189 Wire- worms and skipjacks (illustrated), 337 Yachting and coaching as pleasures, 332 Yachts, electric projectors on board, 473 Y:ite:^, Mr., and Mr. Wilson, 374 Year, the new. 10; the wind, 112 ; forecasts for a year (the weather), 139 Young, Prof. C. A. : astronomical collisions, 2 Zodiacal map for January (iUustrated), 40;^ zodiacal sign for February, with the path of Uranus for 1831 (illustrated),' 165 ; see also 287, 3if4, 395 COEEESPONDENCE. APTKa-GLOW, the, 14: eiamination of, 29 ; in Cheshire-, 47; seeaNoeO, 90, 117 America, red skies in, 15 ; the afler-glow in, 90 American bacon, 275 Animal, alleged attempt of, at suicide, 465 Apparitions. 249, 295. 331 Australia, strange sunsets in, 47 xaminatioD 356, 376, 4')l, 423, 443, 4S5 Colour of the sun, 29 Collection of dust from snow, the, 15 Coloured hyacinth, the effect produced by growing one in cUrkness, 311 Comet, the (illustrated), 60 Conser\ation of energy and the planetary motions, 233 (booking cheese, 3 '5 Corn-crake, the, 400 Cribbage problem, 60, 104, 378 Cube, perspective of a, 400 Curious stones found in Switzerland, on, 170 Cycling, 30 Cyclists and foot passengers, 336 CygQUB, variable and red stars in, 14 Dabs appearance of Jupiter's satellite IV., 233- Day-glow around the sun, 210 Day, the science of the, 29 Deluge year, log of the, 461 Diascope, the, 359 ; the teaching of the, 463 Divided skirt, the. 486 Division by seven. 399 Dogs and cats, 357 Double stars in Tauros and Orion (illastrated), 14 Dream, a strange, 170; remarkable fulfilment of a, 250 Dust, 358 Dust envelope of the earth, the, 190 Dust from snow, the collection of, 15 Duality of the brain, 422 Eablt emotions, 118 Earthj dust envelope of the, 190 July 25, 1S84.] * KNOWLEDGE Corre^pondpnce— roH'ixMtft/. Earthquake, the, 3U liarthqvmkfs from thedisturbance of the subterranean water distribution, 357 Earth, the rotundity of the, 336 Earth-tremors, 335 Edinhurtih lievietc, the, and Sir, Spencer, 167 Eflfett produced by urowiog a coloured hyacinth in darkaesi), the, 211 Examination of the after-glow, the, 29 Extraordinarily low barometer, the, 90 False alarm, a, 331 False perspettive, 357 False suns (illustrated), 133, 170 Falsifving history, 375 Fear of the unfarailiur, 117 Fellowship of learned so< ioties, the, 89, 168 Figure conjuring, 3'.t0 First iuventtir of the telephone, the, 153, 170, 191 Flesh and vegetttble food. 33G Flight ofa missile, the, 1!U Flint-folk'3 flood, the, 4S3 Fretful pjrcuj iue, the, 210 Front-steerini,' tricycle, 464 Fruit-trees in Ireland, 251, 273 Ghostly garments, 212 Ghostly visitants, 151. 212 Ghosts and goblins, 33i Glacial period, man in the. 251, 306 Glow, spectrum of the, 335 Goodwin Sands, the. and Tenterden steeple, 296, 378 Grace, soectrosoope bv, 117 Grand Caiion, the, 376 Gravity, the mystery of. 357, 423 Green sun, the, 29j in Hankow, 191 Hatlstoxes, organisms in (illustrated), 423 Hankow, the green sun in. 191 Happiness, the morality of, 211 Heights above ami the depths below, the, 90 Herschel, Sir J., and the comet of 1862, 314 IsiAGnTAKT false perspective (illustrated), -123 Impression of tricycle tvres. 296 Infants, the senses in, 77. 211 Infinitr, 211, 274 ; transformation of an old poem on, 335 Insects, the preservation of, 422 Invention of the telephone, the, 170, IRl Ireland, the real enemies of, 132 ; fruit-trees in, 251, 273 ; see also 399 Japaxbsb carving, specimen of, 353 Japanese figures, 358 Japanese superstitions, 400 KiST>LT thought, a, 191 Krakatoa and the coffee-plant, 210 Lat>t-bikds. 77 Large meteor, the, 30 Large scale, perpetual motion on the, 47 Learned societies, the, fellowships of, 89, 168 Light, the polarisation of, 77 Lightning, s-ilent, 47 Log of the Deluge year, 46t Mas. brain of, 413, 4(i3 Man in the glacial period, 251, 316 Meal-worms. 275 Meteor, the large, 33 (illustrated), 151 Meteoric dust. 190 Migration, 151 Migration of birds, the, 47, 91 Missile, flight of a, 191 Mock moons and mock suns, 171 Moon, a page from the past history of the, 250 Morality of happiness, the. 211 Morality, scientific, 251, 3lti, 353 Mystery of gravity, the, 357, 423 Xatioxal tricycles, the, 296 Xests in cages, 47 New Prineipia, the, 132, 150. 163 Noah, the rainbow of, 410. 434, 485 Notes on spectroscopic observations of comet Pons, 296 Numbers, property of, 424 OccuLTATiox of Veuus. the, 314 Odd coineidenc?. an. 334 Odds, question in, 30 On curious stones found in Switzerland, 170 Optical illusion, a singular (illustrated), 170, 191 Optical phenomenon, 251 Organisms in hailstones (illustrated), 423 Orthopic (true-visionl, 295 Otto tricycle, the. 487 Owen, Mr., and the Bach incident, 294 Pagk from the past historv of the moon, a, 250 Parks, tricvclists and the/232 Patent Act', the. 423, 164 Pease-pudding. 488 Perpetual motion on the large scale, 29, 47 Perspective ot a cube, 400 ; see also 469 Phenomenal voice, a, 359, 377 Phenomenon, strange, 30, 60, 170, 171, 232 Planetary curiosity, a, 77 Planetiirv motions and the coDservation of enei^, 232 Polarisation of light, the, 77 Pons, eomet of, 76, 335 Ponsbrook, the comet of, 14 Porcupine, the fretful, 210 Potato in Ireland, the, 315 ; and fruit-trees in, 335 Presentiments and strange dreams, 219 Preserving inserts, 122 Prineipia, the New, 132. 150, 163 Properlv of numbers, 42J *' Puir"*Dogirie, 376, 40 J Pyramid, the Great, 169 QcBSTioN in odds, 30 Rainbow of Noah, the, 410, 431, 485 Ked glare, 104, lol Rel skies in America, 15 Red skv-glow, the, 76 Red sunsets at the Cape. 231 Recalled impressions. 39S Recent earthquake, the, 4-13 Remarkable fulfilment of a dream, 350 Remarkable sunsets, the. li Rotundity of the earth, the, 336 Ruskin, Mr., on modern storm-clouds, 104 Saturn, 14 Savage chromatics, 487 Schmidt, lunar map by, 357 Science of the dav, the, 29 Scientific morality. 251. 31B. 358 Senses in infants, the. 77, 211 Sent to the lx)ttom, 463 Severed head, ihe, can it think ? 357 ; see also 496 Silent li,'^htning. 47 Singular and sad coincidence. 37" Singular optical illusion, a (illustrated), 170 Skv-glow, the. 47, 117 Solar spots, 274 Solution of cribba^e problems, the, 91 Sound, the transmission of, 4'TO Sparkbrook, National, the. 191 Spectroscope by Grace, 117 Spectroscopic observations of comet Pons, notes on. 296 Spectrum of the glow, 335 Spencer, Mr., and the Edinburgh Beviev^ 167 Sporting problem, a, 359 Squinting. 424 Strange coincidence, a. 30 ; s<*e also 212, 293, 315, S34, 356, 376, 401, 422, 44.'?, 485 Strange dream, a, 170; abstract of, 170: see also 232, 249, 393 Strange fish. 211 Strange incident, a, 336 Strange phenomenon, 30. 60. 170, 171, 232 Strange re>uscitation, 118. 231 Strange sunsets in Australia. 47 Sun, day-glow around the, 210 Sun, the colour of the, 29 Sun, the green, 29 Sunset-glow. 29. 335 Sun-spot (illustrated), 421 Sunsets, extraordinary, the, 14 Supematuralism. 249 Super-position, 399 Switzerland, on curious stones found in, 170 Tamf, unconfined robins, 101 Taurus and Orion, double stars in (illustrated), 14 Telephone, the first inventor of the, 152. 170. 191 Tenterden steeple and Goodwin Sands, 296, 378 Thumb weakness, 353 Tricycle, catching a ball, a, 378 Tricvcle problem, an unsolved, 252, 357 : see also 290 336 Tricycles, two-track machines, 393 Tricycle wheels. 60 Tricycling uphill, 113 Tricyclists and the parks. 232 Transmission of sound, the, 400 "Twinkle, twinkle, littl.* star" (authorship of the lines commencing), 296; see also 335, 373, 421 Tyres, impression of tricycle, 296 rsTAiriLiAR, fear of the, 117 Unsolved tricycle problem, an, 252 VALrE of the pieces at chess, 232 Variable and red stars in Cvgnus, 14 Vegetable and flesh food, 336 Vegetable diet, 211 Venns, the occultation of, 314 Vision, 232, 295, 357 Wild fuchsia. 191 Winter, bicvcles in. 30 Wolfson r. Birley, 317 Works on botany, 150, 400 REVIEWS. AuBA Dynamica : concerning force, impulse, ani energy. By John O'Toole. Hodges, Figgis, & Co., Dublin, 351 Art of soap -making, the. Bv Alexander Watt. Crosby. Lockvrood, & Co., London, 312 Among the Indians of Guiana : being sketches, chiefly anthropologic, from the interior of British Guiana. By Everardim Thurn, M.A.,Oion. Kegan, Paul, Trench & Co., London, 45 Aids to physiology. By B. Thompson Lowney, F.R.C.S. Bailliere, Tindall, & Cox. London, 231 Aids to botany. By Armand Semple. Bailliere, Tindall. &, Co., London, 1883, 420 About photography and photograpliers, &c. By H. Baden Pritchard, F.C.S. Piper & Carter, London, 371 BiOGB^. A speculation on the origin and nature of life. By Professor Elliott Cones. Triibner i Co_ London, 370 Biographies of working men. By Grant Allen, B.A. Society for Promoting Christian Knowledge, London, 461 "^ Book-keeping no mystery. Crosby, Lockwood, & Co., London, 74 Botanical micro-chemistry. By V. A. Poulsenv Translated by William Trelease. Triibner & Co., London, 231 Breeding horses for use. By F, Ram. Civil Service Printing Company, London, 113 Capital for working boys. By J- E. M'Conaughy. Hodder & Stoughton, Londo'n, 292 Celestial motions. A handy book of astronomy By W. T. Lynn, B.A. E'dward Stanford. London^ 433 * * Chapter of science, a. By J. Stuart, M.A. Society for Promotmg Christian Knowledge, London, Chemical analysis. By A. H. Scott- White, 74 Children, the diseases of. By Armand Semple B A M.R.C.P., 113 f > ■ -i- Civil Senice English Grammar, the. By W. V Yates CM. Crosby. Lockwood, & Co., London, 483 ' Civil Service History of England, the. By F. A, White, B.A. Revised and enlarged bv H. aT Dobson. Crosby, Lockwood, &. Co.. L^indon, 433 Cleopatra, the needle of. By the Rev. J. King. Th& Religious Tract Society, London, 59 Comic poetry. W. Kent & Co., London, 75 Copy-books. Moffat t & Page, London, 75 County atlas of England and Wales. J. Heywood„ Manchester and London, 74 Dr. Cobpus's class. Wyman & Sons, London, 59 Eablt days of Christianity, the. By F W Farrar*- D.D. Cassell & Co., London, 420 Early days of the human race, the. By T Frederick J^ Blaker, M.R.C.S. H. Jt C.Treacher, Brighton, Earth and the solar system, the. Moffatt & Page London, 59 ^ ' Earth, earliest ages of the. By G. H. Pecber, M A. Hodder & Stoughton, London, 461 Electrician, directory of ihe. with handbook for 1354, The Electrician OlEce, London, 420 Elementary conic sections. Bv H. G. Willis M.A. Bell & Co., London and Cambridge 75 * Elementary physiology. By G. T. Bettanv MA Bemrose &. Sons, London, 462 Encyclopaedia Americana: a supplemental dictionary of arts, sciences, and general literature lllus- trated. Vol. 1, A-Cen. J. M. Stoddart, New York, 84 End of the world, prophecies and speculations res- pectmg the. By the Rev. B. W. Savile. Houlston & Sons, London, 113 English language, the : its sources, growth, and literature. By Thomas Page. Moffatt & Pag?, London, 420 Experimental proofs of chemical theory for beginners By Wm. Ramsay. Macmillan & Co., London) Facts around us : simple readings m inorganic science, with experiments. Bv C. Llovd Mor^^an, F.G.S, Edward Stanford, London, 312 * Fernery and aquarium, a hand-book to the Bv J H Martin and James "Weston. T. Fisher "Cnwin London, 420 First lessons in health. By J. Bemers Macmillan Jt Co., London, 74 Fuel and water: a manual for users of steam and water. From the German of Franz Schwacthofey Edited by Walter R. Browne, M.A, Chas. Griffen & Co., London, 420 Gbobgb Birkbeck, the pioneer of popular education. By J. G. Godard. Bemrose & Sons, London 230 German conversation grammar. By I. Sydon W Kent &. Co., London, 230 j • » Great Industries of Great Britain. Cassell & Co London, 420 '* VI ♦ KNOWLEDGE ♦ [Jdly 25, 1884. Greek and Roman coins, handbook of. By H. V. Head. \V. Swan Sonnenschein & Co., "London, 59 Guiana, among the Indians of ; beinfj Bketchee chipfly anthropologic, from the interior of British Guiana. By Everard im Thum, M.A.Oxon. Kej^an Paul, Trench, & Co., London, 45 ^uiid of good life, the. By Benjamin Ward Hit:hard- Bon, M.D. Society for Promoting Christian Knowledge, London, 461 Handbook of competitive eTaminations for admission to every department of Her Majesty's service. By W. J. Chetwode Crawley, LL.D. "Longmans, Green, & Co., London. 433 Heath, the fern portfolio of, 129 Hints to house-hunters and householders. By Ernest Turner. T. Batsford, London, 351 History readers. Motfatt &, Paige, London, 74 House of Lords, the. Bv Sir John Bennett. London, 371 Is God unknown and unknowable? By the Rev. C. E. Beeby. Wyman & Sons, London, 351 Kashgabia, Translated friTu the Russian of Col. A. K". Kuropatldn. By Major W. E. Gowan, W. Thacker & Co., London, 5i) LiFK— function— health: studies for young men. By W. Sinclair Paterson, Hodder & Stoughton, London, 461 Lives worth living. I. Sir John Herschel. By the Rev. Timothy Harley, F.R.A.S. Aleiandor & Sliepheard, London, 31) Lump of iron, a. From the mine to magnet. By Alexander Watt. A. Johnston, London, 370 Magnetic survey o( North-west Canada. By Lieut. (now Gen. Su- J. H.J Lefroy. Longmans & Co., London, 75 3Ianual of taiidermv. Bv C. J. Maynard. Triibner &, Co.. London, 292 Medical fashions in the ninete(*nth centurv. By Edward T. Tibbits, M.D. H. K. Lewis, London, 231 Mineralogy, systematic and descriptive. By' J. H. Collins, F.G.S. William Collins & Co., London and Glasgow, 230 Modern hou^^ehold medicine. By Chas. Rob. Fleury, M.D. Second edition. E. Goulds Son, London- US Natubat, history of the mammalia of India and Cey lon . By Robert A. Sterndale, F.R.G.S. W. Thacker & Co., London, 401 Natural philosophy. Translated from M. Ganot's Coitr$ EUmentairede Pht/sigiie by Prof. Atkinson. Long- mans &. Co., London, 75 ^^avigation. Bv John Merrifield, LL.D. Longmans & Co., London, 113 New Atlantis, the; or, idoals, old and ne^v. By a disciple uf Buckle. WilUams & Norgate Lon- don, 350 New Principia, the. By Mr. Newton Crosland. Triibner & Co., London, 12, 350 Notes of lessons on moral subjects. By F. W. Hack- wood. T. Nelson & Sons, London, 29^' Notes on school management. By Geor"e Collins MofiFatt Jt Page. London, 231 Notes on the New Principia. By Newton Crosland, Optics without mathematics (illustpated) . By the Rev Thos. W. Webb. M.A. Published by the Society tor Promotmg Christian Knowledge, London and New York, 74 Oriental carpets. By Herbert Coion. T Fisher 0nwin, London, 230 t^ABALLEL roads of Glenroy,the. Bv Jas. Macfadzean. J. Menzies & Co., Edinburgh,!131 Periodic law, the. By John A. R. Newlands. E. & F. N. Spon, London, 370 Photography. By J. H. T. EUerbeck. D.H.Cussons & Co., Liverpool, 59 Physiography. Advanced course. Br Andrew Find- later, M.A. W. A; R. Cbambers.London, 312 Populartreatiseon modern photographv, a. By George Dawson, M.A. George Maaon & Co., Glasgow, 371 Practical guide to photography. By Marion & Co Marion & Co., London, 4S3 Practice of medicine. By M. Chateris, M.D. Third edition. J. &. A. Churchill, London, 113 Prophecies and speculations respecting ttie end of the world. By the Rev. B, W. Savile. Houlston & Sons, London, 113 QUALiTATiTB analysis, notes on. By H. J. H. Fenton, M.A. University Press. Cambridge, 113 Bed deer. By Richard Jefferies. Longmans, Green, & Co., London, 58. fiAGACrrr and morality of plants : a sketch of the life and conduct of the vegetable kingdom. By J E _ Taylor, Ph.D. Chattu Jc Windus, London,* 482 Science gleanings in many fields: studies in natural history. By John Gibson. T. Nelson & Sons, London, 12(J Science in the nursery; or, children's toys and what they teach. Griffiths & Farran, London, 371 Scientitic papers of .Isimes Prescott Joule, D.C.L. (Oxitn.). Published by the Physical Society of London. Taylor & Francis, London, 24-* Sele<'tit)ns from previous works, with remarks on Mr. G. J. Romanes's " Mental evolution in animals," and a p.salra of Montreal. By SamUel Butler. Triibner & Co., London, 216 Sir Lyon PJayfair taken to pieces, likewise Sir Charles Dilke. Bart. E. AV. AUen, London, 311 Soap-making, the art of. By Alexander Watt. Crossby, Lockwood, & Co., London, 312 Solar physics and earthquake commotions. By A. H. Swinton, 74 Strains on girdira, arches, and trusses; with a sup- plementary essay on economy in suspension bridges. By K. W, Young. Macmillan & Co., London, 4^2 Tait*8 improved arithmometer. Charles & Edward Laytoii, London, 421 Thrift and independence. By the Rev. William L. Blackley, M.A. Society for Promoting Christian Knowledge, London, 4G1 Transit instruments, the. By Latimer Clark. E. & F. N. Spon, London, 59 True and false issues between Christianity and science. By the Rev. T. Blackburn. W. Skeffington & Sons, London, 59 UscLAiitBD money: a handy book lor heirs at law, next of kin, &"c. Bv E.'Preaton. E. W. AUen, London, 292 Unity of nature, the. By the Duke of Argyll. Alex. dtrahan, London, 162 Universal attraction ; its relation to the chemical elements. Bv W. H. Sbarp. E. Jt S. Livingstone, Edinburgh, 230 Vbstigbs of the natural history of creation. By Robert Chambers, with an introduction relating to the authorship of the work by Alexander Ireland. W. & R. Chambers, London and Edin- burgh, 320 Vignettes from invisible life. By John Badcock, F.R.M.S. Cassell & Co., London, 292 Voice, song, and speech : a practical guide for singers and speakers, from the combined view of vo'ca! surgeon and voice trainer. Bv Lennox Browne, F.R.C.S., and Emil Behnke. Sampson Low, Marston, &. Rivington, London, 85 Watch and clock makers' handbook. By F. J. Britten. W. Kent & Co., London, 230 Weather of 1883, the, as observed in thfe neighbour- hood of London. By Edward Mawley, F.R.Met.S. Edward !>tanford, London, 420 Weights and measures. By John Morrison. William Kidd, Dundee, 113 "Whence? what? where? By Dr. James E. Nichola. Triibner A: Co., London, 74 AVhen did life begin? By G. Hilton Scribner. Charles Scribner, New York, 113 "Where shall I educate my son ? By C. E. Fascoe. Houlston & Sons, London, 59 "Uliist. By J. R. W. Warne & Co., London, 153 Wholesome houses. By E. G. Banner, C.E. Edward Stanford, London, 351 Workshop appUances. By C. P. B. Shelley. Long- mans, Green, & Co., London, 292 Workshop receipts. Third series. Bv C. G. Wam- ford Lock. E. & F. N. Spon, London, lS3t, -483 World-life; or, comparative geology. By Professor Alexander Wincnell, LL.D. "Triibner & Co., London, 58 Wiesen as a health-resort. By Dr. A. T. Tucker. Bailliere, Tindall, A; Cox, London, 59 YocxG collectors* handbook of British birds, of shells, of orders of insects, of butterflies, of beetles, and of postage-stamps. By various aiitliors. W. Swan Soinienschein & Co., London, 420 MISCELLANEOUS. Abtssinxa, travelling in, 375 Accident from electric lighting, 300 Accidents on the railways of the United Kingdom, 331 Air, velocity of sound in, 490 Alpha Draconis, statement referring to the, 130 Alphabet, remarks on a proposed reform of, by Mr. Pitman, 297 Amateur photography, 440 America, the telepnone in, 462 Anatomy and physiology, lectures on, by Dr. Andrew Wilson, lt> Ancient map-makers, 131 Anglesey, methods of spelling, 130 Arizona, lopper from, 30 Art, the duty on works of, 24«S Asbestos paint at the International Health Exhibition, 391) As original as an Englishman, remarks on the phrase, 229 Astronomy and the telescope, 4fi Atmosphere of the sun, 160 Australian beliefs, 131 Automatic lighting of beacons, 460 Bells in the clock-tower of the Law Courts, 320 Bethnal Green Free Museum, patents department of, 190 Billion, trillion, &c., meaning of, in England, America, and on the Continent, 297 Britain, the future of, 4*) British Association, the, 166 British Museum, the, 163 Brazil, telephone wires in, 460 Broken elass, cement for repairing, 28 Brush Electric Company, a compliment to the, 13 Canada, telegraph offices in, 199 Canadian telegraphs, 193 Car-wheels in the United States, 388 Cement for repairing glass, receipt for a, 28 Cheyne, Mr. Watson, demonstration of pathogenic micro-organisms by, 252 China, the telegraph in, 2-4S Coal-mines, number in operation io England and Wales in 1883, 320 Coal, output of, in the United Kingdom, 148 Coal, the production of, 33S Cold, rippara'us for the continuous production of, 228 Colliers. stutiHtic.<( of, in the United Kingdom, 330 Combining colours, 487 Congre-4^ on electrical units, decision of the, regarding length of a column of mer'uri-, 415 Condu't of lil'Gbr of overhead wires, the, 13 Destruction of telegraph ^rire, 40^ Diamond, the matrix of the, 222 Distilled water : where to procure it, 31 Divers, the telephone for, 265 Duty on works of art, the, 243 Eabth : ia it advancing nearer the snn? 297 Eastward Ho: reference to the new magazine of that name, 273 Edison light on the Continent, the, 89 Electrical congre-is, the, 312 Electric lighting at lIuU, 4-15, 462 ; accident from, 300 Electric tramway incident, an, 309 Elephantiasis and electricity, 165 Elephant that reads, an, 226 England and Scotland, telegraphic communication between, 209 Expensive railway, an, H Floods in the Ohio, 460 Florida, a projected canal across, 59 Foreign trade of India in ls82-3, the, 8 Foster, Mr. Thomas, and correspondents on the morality of happiness, 149 France, underground mres in, 73 French railways, the telephone on, 5 French subterranean telegraphy, 421 Future of Britain, the, 4U Gas in Paris, 367 Gases, the liquefaction of, 312 Geological society, the, 477 Geneva, the Rhone at. 462 German steam navigation, 410 Gilchrist penny science lectures, the, 235 Globe lightning, 479 Glow, the morning, 89 Great East em, proposal to make a floating hotel of the, 103, 169 Gulchen Electric Light Company, installation of the, Gutia-percha, reference to, 133 Herschbl. Col., reference to, 348 Highways in England, average expenditure on, 132 Horse, sagacitv of the, 246 Hull, electric fighting at. 4*5 Human body, electrical resistance of the, 294 iLLrMiXATrr, a new, 222 Importance of trifles in science, the, 44 India, the foreign trade of. in 1S82-3, 8 Indian population of the Cnited States, the, 131 Industnal use for electricity, an, 354 Injustice as immorality, 379 Instinct, 23 Interesting discovery, an. 314 International Health Exhibition, the, 411 Iron and steel, the world's production of, 75 JoHX Bull's neighbour in her true light, 119 July 25, 1884.] • KNOWLEDGE • Vll Miscellaneous — confin ued. Kettle, tht> explosiuii of an open, iift Knowledge, references to ulteratioua Id, 129, 130 Lake Superior, copper-mines of, lilft Langenboe Church untl the recent earthquake, 3iO Lost railway oars, 'i'6'i Lead, production of, in Spain, 320 Lighthouse, a line example of a, :JH9 Lighting of railway carnages, the, 190 Lightning-rod, the. Mil Liquid tire-proof eyanito, the, 354 Liquefaction of gaaes, the, 312 Loieette, Professor, system of memory -teachiag by, 59 Long-distance telephony, 119 Lucifer match manufactory in Sweden, a, 28 Lunacy Law Reform Association, report of the, 479 Luiotype, the, "ti Macqcabie light (Port .Tiiclcson, Australia), 30'J Man, sense of direction in, 22 Manganese, black oxide of, in Jamaica, 21-1 Marine losses of the world during 1883, 228 Matrix of the diamond, the, 222 Metropolitan Railway, issue of tickets by the, 391 Mineral statistics ot"the United Kingdom, the, 273 Moisture on glass, 297 Montigny, M. Ch., spectrometer of, 4S9 Morality of happiness, the : care for self aa a duty, 20^1 Morning-glow, tne, 39 National Health Society, the, 173 Negative thermometer, a, 131 New illuminant, a, '2.21 Norfolk, the Duke of, and the Sheffield Technical School. 4G'i Northern Pacific Railway, opening of, amusing allusion to, 76 North Pole, the secret of the, 103 Ocean" Collieries, electric light inatallatlon at the, 135 Ohio, floods in the, 460 Ohio railways, statistics of the, 309 Opinions, remarks on, 130 Ordnance Depattment, the, and Lieut.-ColonelHope, 454 Our portrait, 42 Overhead wires, the danger of, 13 j see also 393 Panama Canal, the, 372 Paper-making statistics, 419 Paris, gas in, 367 Pathogenic micro-organisms, demonstration of, by Mr. "Watson Cheyne, 252 Phenomenon, a curious, 58 Photographic Society of London, the, 374 Physical pain alle\n:ited by mathematical studies, 133 Pintsch gas apparatus, the. 3S2 Pintsch, Mr. Julius, the death of. 103 Platinum wire of extreme thinness, 463 Poetry of science, 209 Portrush electric tramway, singular accident on the, 228 Primitive man, lectures on, 36 Production of coal, the, 33S Punch, a criticism of, 149 Rails, production of, 190 Reading elephant, a, 220 Refraction of waves, the, 396 Rhone at Geneva, the, 462 Siachuelo (ironclad built for the Brazilian Govern- ment), account of the, 300 Rogers, J. B., Electric Light and Power Companv. 354 Rotating the plane of polarisation of light, 396 Rowing in the university boats, newspaper criticisms of. 229 Royal Victoria Coffee-hall, the, 233, 291, 454 Rusldn, Professor, remarks on, 337 Safety lamps, 60 Sagacity of the horse, 246 Science, the importance of trifles in, 44 Science, the poetry of, 209 Scientitic societies and elections thereto, 229 Secret of the North Pole, the, 103 Sense of direction in man, L'2 Shaw, Captain, on the liquid fire-proof eyanite, 354 Shooting stars, 102 Skertchley, Sydney J. B., F.G.S., lectures on primi- tive man by, 36 Sleeping accommodation on the Great Southern and "Western Railway Company, Ireland, 456 Solid carbonic acid, 312 Sound, velocity of, in air, 490 Sparkbrook National tricycle, the, and Mr, Richard A. Proctor, 293 Speed of waves in water, 202 Steam, use of, to extinguish fire, 248 Storms and telegraphic conmiunication, 190 Subterranean fish, 373 Successful advertising, 214 Suicide, a singular, 312 Sun, the atmosphere of the, 166 Swedenborg Society, meeting of the, 477 Technical education, 440 Telegraphic communication between England and Scotland, 2U9 Telegraphic wires in New York, 375 Telegraph, ludicrous explanation of the working of the, in China, 248 Telegraph messages, number of, in England during 1883, 304 Telegraph offices in Canada, 199 Telegraph wire, destruction of, 408 Telephone on French railways, the, 5; for divers, 265; wires underground, 320; wires in Brazil, 460 ; in America, 462 Telephonic communication between moving vessels, 76 Telescope, the, and astronomy, 46 Thermometer, a negative, 131 Tide, observations on thy, 2o2 Time-corrector, a, 166 Travelling in Abyssinia, 375 Trifles in science, the importance of, 44 Undeegbound wires in France, 73 United States, the Indian population of the, 131 A'blocity of sound in air, the, 490 Ventilators of the Metropolitan District Railway, re- moval of two of the, 112 Vertical steam boiler, bursting of a, 318 "Water in Anstralia, 137 "Waves, speed of, in water, 202; the refraction of, 398 Well-earned praise, 22 Wilson, Dr. Andrew, lectures on anatomy and physiology by, 16, 28 "Wire fence telegraph, a, 209 Wonderful bicycle ride, a, 398 ILLUSTRATIOKS. Afeica, sketch-map of, 184 Alisma plantago, the, ti4 Alisma ranunculoides, the, 114; the alisma natans, 115 AmiL'ba, diagram of an, 110 Aphyllanthes Montpeheueis, 386 Asbasia trichopora, specimens of, under the micro- scope, 143 Aspirator, diagram of an (a contrivance for collecting dust for microscopic purposes), 51 Baboubteb, a, in relation to a spectroscopic examina- tion of sunrises and sunsets, 169 Boer aerating machine, a, 416 Bees, diagrams showing fore-wing and tongues of, 53 Borage flower, portiou of, 430 Bunsen cells, diagram of, 353 Butomus umbellatus, the, 176 Canadian porcupine, the, 56 Click-beetle {oyriotes ohscurus), 328 Clustering region of the Milky Way in Cygnus, the, 144 Comet, the, of 1834, 60 Comfrey petal, segment of, 430 Constellations, map of, 247 Corn-weevil, a, 206 Cube, perspective of a, 35S Cuckoo-bee parasite, ^iew of a, lOO DAMASomrM stellatnm, the, 133 Day-sign for March, 207 ; for the month, 286, 394, 480 Diurnal course of the sun, map illustrative of the, 21; Double stars, diagram of, 408 Doultun, pavilion of Messrs., 435 Doulton sanitary ware, figures of, 476, 477 Doulton ware stoves, 454, 455 Drawing the planets, diagrams illustrating methods for, 86 Drink curve, diagram of the 223 Dust on an object-glass, diagram of, 358 Dytiscus, heaa of, 474; hind leg of, 475 Earth, path of, round the sun, diagram of, 41 Electrical battery, diagram of one introduced by Messrs. Warren de la Rue and Hugo Miller, 412 Eicelsior bott ling-machine, the, for aerated water, 417 False suns, diagram explanatory of, 133 Female flower of the thuja aurea, 182 Firetail, or golden wasp, view of, 100 Fish-scales, diagrams of, 2S2, 283 FritUlaria melea gris, 291 Gagea lutea (field lily), 220 Galaxy and its fellow star sj'stems, Wright's theory of the, 9 Gerris lacustris, figure of, 373 Glypta luguorina, 245 Gyrmus natator, and side view of head of, 414 Haibs on a wasp's wing. 372 Hazel pollen (magnified), 182 Heads of dytiscus and hvdrophilus, 474 Herschel, Sir AVilliam, diagrams illustrating views and observations of, as to the universe of suns in 1784 and in 1785, 57 Herschel, view of, regarding the Milky Way, 145 H.tw to make useJul atar-nuips, diaixrams of, 5, 6 Hydrometra staguorum, figure of, 373 Ichneumon, fore-wing of the, 245 Ixodes marginatus, rostrum and one mandible of, 473; network in stigma of, i73 JuNcrs communis, 387 Jupiter in a three-inch telescope, 126; eclipses of satellites of, 127 Jupiter, view of, during January, 1884, 101 Keplee, idea of the universe of Lambbet, map showing theory by, of our stellar system, a5 Lateral amphitheatre of the second order in th© Grand Cation, 450 Leaf-cutter bee, a (mff/arhlle centuJicufaris), 125 Lloydia serotina (a lily verging towards a tulip), 291 Maes as seen in a three-inch telescope, 140 Mars, the path of, relatively to the earth during the- opposition period of lfiS4, 8 Mars, the planet in relation to the earth, diagrams of, 71,72 Meteor, diagram of the course of a, 151 Microscopic objects, groups of, 52 Alilky Way, the, clustering region of, in Cygnus, 144 Naucobis cimicoides, 450 Niagara, a cantilever bridge over, 227 *'>'iagara" condenser, the, for the aeration of 80da and other waters, 417 Xight-sign for the month, the, 237, 331, 395, 481 Nut-weevii, head of, 160 Occultation of the moon, 269 Ophideres, probosces of, 330 Optical illusion, diagrini of an. 170 Optical recreations, figures illustrative of, 306, 39C^, 391,436, 4;}7, 480 Organisms in a hailstone, 423 Ornithorhynchus, figure and skeleton of, 269 Oscillations of light, diagrams of, 352 Oiyhydrogen lamp, diagram of two forms of, 209 Paths of Mars, Earth, Venus, and Mercury, 310; ef Xeptune, Uranus, Saturn, and Jupiter, 311 Pendulum experiments (Foucault's), diagrams illus^ trative of, 413 Perspective, diagrams of imaginary false, 422 Pezomachus transfuga, figure of (ichneumon), 28S Plastering-bee, the tongue of a, 125 Polarisation, diagrams illustrative of, 74 Porcupine, the Canadian, 56 Ror£-B£ETLB5, four figures illustrative of, 27 Saccharomtces cerevisife (the yeast-plant), 415 Sagittaria sagittifolia, the, 175 Saturn, a view of, 185 Scintillometer, a, 180, 181 Sitones Uneatus, figure of, 160 Star-maps, diagrams of, 36, 37, 111. 146, 147 Stylops, view of a male species of, 100 Sunspot, diagram of a, 4^1 Tausus and Orion, diagram showing double stars lo, 14 Telephone, figures illustrative of the, 12S, 129 Thuja aurea, female flower of the, 182 Trachelomonad. diagram of, 110 Trichiui^, two figures of, under the microscope, one showing cyst \r\ih coiled-up worm and the other the worm out of cyst and uncoiled, 21 Tricycle accident, representation of, 73 Tri^lochin palustre. the, 138 Tulipa gesneriana (the garden tulip), 290 Univbese of suns, the, diagram referring to, 96, 432 Uranus, view of, March 16, 1884, 199 Usnea barbata, section of a slender branch of, aa seea under the microscope, 83 Velia currena, figure of, 414 Wibewobm:, a (magnified), 327 Zelb teataceator, fore-wing of, 288 Zodiacal signs for February, with the paths of Mars and Jupiter in 1834, 70, 87, with the path of Uranus in 1384, 165 '^Jvty 4, 1884.] KNOWLEDGE ♦ AN ILLUSTRATED _^ AGAZINE OF SCIENCE ^MnLYWORDED -EXACTLYDESCmm LONJJOiX: t'lUDAY, JULY \, 1884. Contents of No. 140. PAGB Chemistry of Cookery. XXXTII. By W. M. Williams 1 Notes on Flying and Flying-Ma- chines. Bv Richard A. Proctor... 2 Electro-plating. A'll. By W. Shngo 4 Comet Families of the Giant Planets. Uy liicbard A. Proctor 5 Photographing a Flash of Light- ning. (Jllm.) ..._ „, 6 The Antarctic Regions By R. A. Proctor 6 International Health Exhibition.— VI, Water and Water Supplies ... 7 10 PAOB On Peculiarities of Sight and Opti- cal Illusions. By N. E. Green ... 0 The Evolution of Flowers. (Illus.) By Grant Allen Conceit (for Self and Family) . By R. A. Proctor 11 Reviews 12 Editorial Gossip 13 The Face of the Sky. By P.K.A.S. 14 Correspondence 14 Our Piiradta Column 17 Our Mathematical Column 18 Our Whifit Column 19 Our Chess Column 30 THE CHEMISTRY OF COOKERY. By W. Mattieu Williams. XXXYII.— COUXT RUMFOED AND THE BAVARIAN BEGGAKS. I MUST not leave the subject of vegetable cookery without describing Count Eumford's achievements in feeding the paupers, rogues, and vagabonds of Munich. An account of tliis is the more desirable from the fact that the " soup " which formed the basis of his dietary is still misunderstood in this country, for reasons that I shall presently state. After reorganising the Bavarian army, not only as regards military discipline, but in the feeding, clothing, education, and useful employment of the men, in order to make them good citizens as well as good soldiers, he attacked a still more difficult problem — that of removing from Bavaria the scandal and burden of the hordes of beggars and thieves which had become intolerable. He tells us that " the number of itinerant beggars of both sexes, and all ages, as well foreigners as natives, who strolled about the country in all directions, levying con- tributions from the industrious inhabitants, stealing and robbing, and leading a life of indolence and most shameless debauchery, was quite incredible," and, further, that " these detestable vermin swarmed every- where, and not only their impudence and clamorous importunity were without any bounds, but they had recourse to the most diabolical acts, and most horrid crimes, in the jjrosecution of their infamous trade. Young children were stolen from their parents by these wretches, and their eyes put out, or their tender limbs broken and distorted, in order, by exposing them thus maimed, to excite the pity and commiseration of tlie public." He gives further particulars of their trading upon the misery of their own children, and their organisa- tion to obtain alms by systematic intimidation. Previous attempts to cure the evil had failed, and the public had lost all faith in further projects, and therefore no support was to be expected for Eumford's scheme. " Aware of this," he says, " I took my measures accordingly. To con- vince the public that the scheme was feasible, I determined first, by a great exertion, to carry it into complete execu- tion, and then to ask them to support it." He describes the military organisation by which he dis- tributed the army throughout the country districts to capture all the strolling provincial beggars, and how, on Jan. 1, 1790, he bagged all the beggars of Munich in less than an hour by means of a well-organised civil and mili- tary battue, the New Year's Day being the great festival when all the beggars went abroad to enforce their customary black-mail upon the industrious section of the population. Though very interesting, I must not enter upon these de- tails, but cannot help stepping a little aside from my proper subject to quote his weighty words on the ethical principles upon which he proceeded. He says that " with persons of this description, it is easy to be conceived that precepts, admonitions, and punishments would be of little avail. But where precepts fail, habits maj' sometimes be successful. To make vicious and abandoned people happy, it has generally been supposed necessary, Jirst, to make them virtuous. But why not reverse this order ? Why not make them first happy and then virtuous 1 If happi- ness and \artue be inseparable, the end will as certainly be attained by one method as by the other ; and it is most undoubtedly much easier to contribute to the happiness and comfort of persons in a state of poverty and misery than, by admonitions and punishments, to improve their morals." He applied these principles to his miserable material with complete success, and referring to the result exclaims, " Would to God that my success might encourage others to follow my example ! " Further examination of his pro- ceedings shows that in order to follow such example, a knowledge of first principles and a determination to carry them out in bold defiance of vulgar ignorance, general prejudice, and polite sneering, is necessary. Having captured the beggars thus cleverly, he proceeded to carry out the above stated principle, by taking them to a large building already prepared, and where "everything was done that could be devised to make them really com- fortable.^' The first condition of such comfort, he maintains, is cleanliness, and his dissertation on this, though written so long ago, might be inscribed in letters of gold over the portals of our Health Exhibition of to-day. Describing how he carried out his principles, he says of the prisoners thus captured : — " Most of them had been used to living in the most miserable hovels, in the midst of vermin and every kind of filthiness, or to sleep in the streets, and under the hedges, half naked and exposed to all the inclemencies of the seasons. A large and commo- dious building, fitted up in the neatest and most comfort- able manner, was now pro^^ded for their reception. In this agreeable retreat they found spacious and elegant apartments, kept with the most scrupulous neatness ; well warmed in winter, and well lighted ; a good, warm dinner every day, gratis, cooked and served up with all possible attention to order and cleanliness ; materials and utensils for those that were able to work ; masters gratis for those who required instruction ; the most generous pay, in money, for all the labour performed ; and the kindest usage from every person, from the highest to the lowest, belonging to the establishment. Here in this asylum for the indigent and unfortunate no ill-usage, no harsh language is per- mitted. During five years that the establishment has existed, not a blow has been given to any one, not even to a child by his instructor." This appears like the very expensive scheme of a bene- volent Utopian ; but, to set my readers at rest on this point, I will anticipate a little by stating that, although at ♦ KNOWLEDGE ♦ [July 4, 1884. first some expense was incurred, all this was finally repaid, and, at the end of six years, there remained a nett profit of 100,000 florins " after expenses of every kind, salaries, wages, repairs, ic, had been deducted." I must not dwell upon his devices for gradually in- veigling the lazy creatures into habits of industry, for he understood human nature too well to adopt the gaoler's theory, which assumes that every able-bodied man can do a day's work daily, in spite of previous habits. Rumford's patients became industrious ultimately, but were not made so at once. This development of industry was one of the elements of financial and moral success, and the next in importance was the economy of the commissariat, which depended on Rumford's skilful cookery of the cheapest viands, rendering them digestible, nutritious, and palatable. Had he adopted the dietary of an English workhouse or an English prison, his financial success would have been impossible, and his patients would have been no better fed, nor better able to work. The staple food was what he calls a " soup," but I find, on following out his instructions for making it, that I obtain a porridge rather than a soup. He made many experiments, and says : " I constantly found that the rich- ness or quality of a soup depended more upon a proper choice of the ingredients, and a proper management of the fire in the combination of these ingredients, than upon the quantity of solid nutritious matter employed ; — much more upon the art and .skill of the cook than upon the sum laid out in the market." Our vegetarian friends will be interested in learning that at first he used meat in the soup provided for the beggars, but gradually omitted it, and the change was un- noticed by those who ate, and no difierence was observable as regards its nutritive value. In 1790 little, or rather nothing, was known of the che- mistry of food. Oxygen had been discovered only sixteen years before, and chemical analysis, as now understood, was an unknown art. In spite of this, Rumford selected as the basis of his soup just that proximate element which we now know to contain, bulk for bulk, more nutritive matter ■than any other that exists either in the animal or vege- table kingdom, viz., casein. He not only selected this, but he combined it with those other constituents of food which our highest refinements of modern practical, che- mistry, and physiology have proved to be exactly what are reqxiired to supplement the casein and constitute a com- plete dietary. By selecting the cheapest form of casein and the cheapest sources of the other constituents, he succeeded in supplying the beggars with good hot dinners daily at the cost of one halfpenny each. The cost of the mess for the Bavarian soldiers under his command was rather jnore, viz., twopence daily, three farthings of this being devoted to pure luxuries, such as beer, ic. The details of the means by which he achieved these notable results will be stated in my next. Apropos of the great enthusiasm at present existing on the sub- ject of photography, and the number of distinguished amateurs who practise the art, it may interest our readers to know that among them may be included H.E.H. Due de Chartres, who has just favoured Messrs. Watson & Sons, of 313, High Holborn, with an order for complete outfits to take pictures up to 18 by 16 inches. The members of the Harleian Society have received during the week the " Visitation of London, 1633-4," Vol. II., edited by Dr. J. J. Howard. The " Registers of St. Antholin, Budge Row." had previously been issued to subscribers by Messrs. Mitchell & Hughes. The " Visitation of Gloucestershire in 1623," edited by Sir John Maclean and W. C. Heane, Esq., will also be ready for members this year; likewise Vol. I. of the " Registers of St. James, Clerken- well," edited by Robert Hoveuden, Esq. XOTES ON FLYING AND FLYING- MACHINES. By RicH.iRD A. Proctor. (Continued from page 472.) TT/^E come next to a much more important point, namely, V\ extent of supporting surface. We are to consider the air now, not with regard to its density, the quality which enables a balloon, filled with rarer gas, to float in air, but with reference to its power of resisting downward motion through it; that is, of resisting the effects of gravity. We have to inquire what extent of surface, spread either in the form of wings or as in parachutes, -n-ill sufiice to support a man or a flying-machine. It is here that the researches recently made seem to bear most significantly upon the question of the possibility of flight. The history of the parachute afibrds some insight into the supporting power of the air — some, but not much. The parachute has been commonly [suffered to fall from beneath the car of a balloon. .Suspended thus, in the lee, so to speak, of the balloon's mass, and with its supporting surface unexpanded, the parachute descends under highly unfavourable conditions. A great velocity of descent is acquired before the parachute is fully expanded, and thus the parachute has to resist a greater down-drawing force than would be the case if the machine were open, and surrounded on all sides by free air, at starting. The conse- quence is a great and sudden strain upon all parts of the parachute, as well as a degree of oscillation which seriously risks its structure, besides impairing its supporting power — since this power would obviously act most effectively if the span of the parachute remained horizontal throughout the descent. The following account of Garnerin's descent, in 1797, illustrates the foregoing remarks : — " In 1797," says Mr. Manley Hopkins, "Garnerin constructed a parachute, by which he descended from a balloon, at an elevation of 2,000 feet. The descent was perilous, for the parachute failed, for a time, to expand ; and after it had opened, and the immediate fears of the immense concourse which had assembled in Paris to witness the attempt had been removed, the oscillations of the car, in which Garnerin was seated, were so violent as to threaten either to throw him out, or, on arriving at the gi-ound, to dash him out with violence. He escaped, however ! " We notice the same circumstances in the narrative of poor Cocking's disastrous attempt in 1837. "When the cords which sustained the parachute were cut, it descended with dangerous rapidity, oscillating fearfully, and at last the car broke away from the parachute, and Mr. Cocking was precipitated to the ground, from a height of about one hundred feet" But apart from these considerations, the parachute affords no evidence whatever of the increased sustaining power of the air on bodies which traverse it rapidly in a more or less horizontal directioo. The parachute descends, and descends quickly': we have to inquire whether the air may not resist descent so strongly that with comparatively small eftbrt a horizontal or even ascending motion may be effected. A familiar illustration of this supporting power of the atmosphere is given in the flight of an oyster-shell or piece of thin slate, deftly thrown from a schoolboy's practised hand. Such a missile, instead of following the parabolic path traversed by an ordinary projectile, is seen to skim along almost like a bird on resting piuions. It will some- times even ascend (after the projectile force has ceased to act in raising it), as though in utter disobedience to the laws of gravitation. July 4, 1884.] • KNO\A/'LEDGE ♦ The fact appears to be that wlien a horizontal plane traverses the air in a horizontal direction, the supporting power of the air is increased in proportion as the plane moves more quickly, or in proportion to the actual quan- tity of air it glides over, so to speak. Indeed, we have clear evidence to this effect in the beliaviour of the comniou toy-kite, the supporting power of which is in- creased in proportion to the force of the wind. For a kite held by a string in a strong horizontal current of air, cor- responds exactly to an inclined plane surface drawn swiftly in a horizontal direction during a calm. The same sup- porting power which results from the rapid passage of the air under the kite will be obtained during the rapid passage of the kite over still air. When we study the flight of birds we are confirmed in the opinion that velocity of horizontal motion is a point of extreme importance as respects the power of flying. For though there are some birds which seem to rise almost straight from the ground, yet nearly all, and especially the larger and heavier birds, have to acquire a considerable horizontal velocity before they can take long flights. Even many of those birds which seem, when taking flight, to trust rather to the upward and downward motion of their wings than to swift horizontal motion, will be found, when carefully observed, to move their wings up and down in such sort as to secure a rapid forward motion. I have been much struck by the singularly rapid for- ward motion which pigeons acquire by what appears like a simple beating of their wings. A pigeon which is about to fly from level ground may be seen to beat its wings quickly and with great power ; and yet instead of rising with each downward stroke, the bird is seen to move quite horizontally, — as though the wings acted like screw- propellers. I believe, in fact, that the wings during this action do really act, both in the upward and downward motion, in a manner resembling either screw-propulsion or the action by which seamen urge a boat forward by means of a single oar over the stern.* The action of a fish's tail is not dissimilar ; and as the fish, by what seems like a simple beating of its tail from side to side, is able to dart swiftly forwards, so the bird, by what seems like a beating of its wings up and down, is able — when occasion requires — to acquire a swift forward motion. At the same time it must be understood that I am not questioning the un- doubted fact that the downward beat of a bird's wing is also capable of giving an upward motion to the bird's body. The point to be specially noticed is that when a bird is taking flight from level ground, the wings are so used that the downward stroke gives no perceptible up- ward motion. But since a horizontal velocity is thus effective, we might be led to infer that the larger flying creatures, which, co'teris paribus, travel more swiftly through the air than the smaller, would require a smaller relative extent of supporting surface. We are thus led to the consideration of that point which has always been regarded as the great, or rather the insuperable difiiculty, in the way of man's attempts at flight, — his capacity or incapacity to carry the requisite extent of supporting surface. We are led to inquire whether a smaller extent of supporting surface than has hitherto been deemed necessary may not suffice in the case of a man, and a fortiori in the case of a large and powerful flying-machine. The inference to which we have thus been led, is found to accord perfectly with the observations which have been * Sailors call this sculling, a term more commonly applied to the propulsion of a boat by a single oarsman using a pair of oars, or sculls. made upon flying creatures of different dimensions. It has been found that the supporting surface of these crea- tures,— whether insects, birds, or bats, — by no means varies in proportion to their weight. This is one of the most important results to which the recent inquiries into the problem of flight have led ; and I believe that my readers cannot fail to be interested by an account of the relations which have been observed to hold between the weight and the supporting surface of different winged creatures. We owe to M. de Lucy, of Paris, the results of the first actual experiments carried out in this direction. The following account of his observations (made in the years 18G8, 18G9) is taken from a paper by Mr. Brearey, the Honorary Secretary to the Aeronautical Society. " M. de Lucy asserts," says Mr. Brearey, " that there is an unchangeable law, to which he has never found any exception, amougst the considerable number of birds and insects whose weights and measurements he has taken, viz., that the smaller and lighter the winged animal is, the greater is the conijiarative extent of supporting surface. Thus in comparing insects with one another — the gnat, which weighs 460 times less than the stag-beetle, has four- teen times greater relative surface. The ladybird, which weighs 150 times less than the stag-beetle, possesses five times more relative surface, &c. It is the same with birds. The sparrow, which weighs about ten times less than the pigeon, has twice as much relative surface. The pigeon, which weighs about eight times less than the stork, has twice as much relative surface. The sparrow, which weighs .339 times less than the Australian crane, possesses seven times more relative surface, &c. If we now compare the insects and the birds, the gradation will become even more striking. The gnat, for exam])Ie, which weighs 97,000 times less than the pigeon, has forty times more relative surface ; it weighs .3,000,000 times less than the crane of Australia, and possesses relatively 140 times more sur- face than this latter, which is the heaviest bird M. de Lucy had weighed, and was that also which had the smallest amount of surface, the weight being nearly 21 lb. ; and the supporting surface 139 inches per kilogramme (2 lb. 3J oz ). Yet of all travelling birds the Australian cranes undertake the longest and most remote journeys, and, with the exception of the eagles, elevate themselves the highest, and maintain flight the longest." M. de Lucy does not seem to have noticed the law to which these numbers point. It is exceedingly simple, and amounts in fact merely to this, that instead of the wing- surface of a flying creature being proportioned to the weight, it should be proportioned to the surface of the body (or technically, that instead of being proportioned to the cube, it should be proportioned to the square of the linear dimen- sions). Thus, suppose that of two flying creatures one is 7 times as tall as the other, the proportions of their bodies being similar, then the body surface of the larger will be 49 times (or 7 times 7) that of the other, and the weight 343 times (or 7 times 7 times 7) that of the other. But instead of the extent of wing-surface being 343 times as great, it is but 49 times as great. In other words, relatively to its weight the smaller will have a wing-surface 7 times greater than that of the larger. How closely this agrees with what is observed in nature, will be seen, by the case of the sparrow as compared with the Australian crane; for M. de Lucy's experiments show that the sparrow weighs 339 times less than the Australian crane, but has a relative wing- surface 7 times greater. It follows, in fact, from M. de Lucy's experiments, that, as we see in nature, birds of similar shape should have wings , similarly jiroportioned, and not wings corresponding to the ♦ KNOWLEDGE ♦ [July 4, 1884. relative weight of the birds. The same remark applies to insects ; and we see, in fact, that the bee, the bluebottle, and the common fly — insects not unlike in their proportions — have wings proportioned to their surface dimensions ; the same holding amongst long-bodied insects, like the gnat and the dragon-fly, and the same also among the different orders of flying beetles. So that, setting apart difl'erences of muscular capacity and adaptation, a man, in order to fly, would need wings bearing the same proportions to his body as we observe in the wings of the sparrow or the pigeon. In fact, the wings commonly assigned to angels by sculptors and painters would not be so disproportioned to the requirements of flight as has been commonly supposed, if only the muscular power of the human frame were well adapted to act upon wings so placed and shaped, and there were no actual infe- riority in the power of human muscles (cross-section for cross-section) as compared with those of birds. So far as the practicability of actual flight on man's part is concerned, these two points are, indeed, among the most important we have to consider. It was to Borelli's remarks on these points, in his famous treatise, De motu Animaiium, that the opinion so long entertained respecting the impracticability of flight must be referred. He com- pared the relative dimensions of the breast muscles of birds with those of the corresponding muscles in man, and thence argued that man's frame is altogether unadapted to the use of wings. He compared also the relative muscular energy of birds and men, that is, the power of muscles of equal size in the bird and the man ; and yet was further confirmed in the opinion that man can never be a flying animal. {To ie continued.) ELECTRO-PLATING. vir. By W. Slingo. THE copy, on being released from the mould, is gene- rally mDre or less brittle. It is, therefore, made red-hot in a clear fire or by means of a blow-pipe. When cool it is placed in a weak sulphuric acid solution to remove any scale or superficial impurities which may be present. After a few minutes' exposure it is removed into a vessel containing clean water, and subsequently taken out and dried. Any superfluous metal that still remains is now chipped off and the copy cut to form. The sur- face next requires polishing, which is accomplished ■with rotten -stone and oil, applied with a stiff brush. The particles of metal, &c., adhering to the copy are washed off with soap and boiling water, and the surface again polished, using this time moistened rouge and a soft brush. The finger, at this stage, becomes a very useful tool for brightening the smoother portions of the surface. When the copy is required to possess con- siderable substance, that is to say, when it is to be able to withstand rough or hard usage, as in the case of electro- types of wood engravings, &c., a backing of foreign and more easily fusible metal is and must be provided. It would be false economy, and, indeed, almost a practical impossibility, to take copies sufficiently stout to answer such purposes as above indicated. The process of " back- ing " should present no serious difliculties to the amateur. The copy should be laid face downwards and the back or inner surface moistened with killed spirits of salts, that is to say, hydrochloric acid which has been neutralised or killed by dropping in it small pieces of zinc. A small piece of pewter solder is then placed on the back of the copy and made to cover that surface. This is easily accomplished with a soldering iron or (holding the copy in the jaws of a pair of pliers, so as to be able to move it about) a V)lowpipe flame.* For want of better means, a good flame may be obtained fiom a gas-jet, and sometimes from a spirit-lamp, with the aid of a piece of non-combustible tubing, such as the stem of a clay tobacco-pipe. Care must be taken that the surface of the copper is fairly coated with solder. This is ensured by an eflScient application of the chloride of zinc solution. The coating of solder being obtained, lead is next poured in tDl the required thickness is obtained. The lead combines or adheres to the solder readily, but would not so adhere to the bare copper, hence the necessity for using the solder. Apart from the scientific or experi- mental interest pertaining to the various operations de- scribed, there are a vast number of practical applications fraught with the greatest importance. Not the least of these is the adaptation of the electrotyping process to printing on a large scale. Where a large number of im- pressions are required, more particularly of diagrams, pic- torial illustrations, newspaper headings, ic, the process is almost invariably resorted to. The Illustrated London News and such-like papers not only treat their illustrations in this way, but apply the process to their type as well The process is a simple one. A ball of gutta-percha is place on the centre of the type and worked outwards gra- dually so as to exclude every possible particle of air, and obtain a perfect negative copy of the type. A weight is placed on the percha, and left there until the latter has cooled down, When cool, the percha is well coated with plumbago, and immersed in the electrolytic bath for a few hours, when, a sufliciently thick deposit having been obtained, it is taken from the bath, the percha se- parated from the copper, and a substantial backing supplied. The backing being made level, it is screwed on to a wooden block, of a thickness suflicient to raise the electrotype to the same level or thickness as ordinary lead type. The advantage of such a process is evident. More especially is this so in the case of an en- graving, which would manifestly suffer very considerably were it used extensively. The durability of a wood en- gi'aving is not extraordinarily great, and once damaged the cost of replacing it is almost, if not quite, as great as the original cost ; whereas, by the adoption of the electro- typing process, additional equally good copies may be pro- cured at onlj-^ a trifling expense. The advantages offered by the process for the preservation of valuable and artistic engravings are too apparent to be further discussed. Some papers, it may be furthermore remarked, are very hard and unyielding, and in consequence they considerably injure the type or block, speedily rendering the impressions blurred and more or less trying to decipher. It is recorded that as many as 20,000,000 impressions have been taken from a single mould. Some typers use plaster of Paris instead of gutta-percha ; but although it is cheaper and sets more rapidly, it does not yield so perfect a copy, there being a want of clearness. There is, however, one great drawback to the adoption of the electrotyping process for books, viz., that in second or subsequent editions, errors, small, it may be, in the amount of type involved, but great in importance, cannot be rectified without sacrificing a page or so of the electrotype. On the other hand, there is * A soldering-iron in the bands of the amateur is often a dangerous weapon. He is apt to use it too heavily, and there ia a possibility of his pushing it through the electrotype. A spirit flame is, therefore, safer and equally effectual. July 4, 1884.] KNOWLEDGE ♦ to be coQsidered the fact that were it not for the compara- tively small expense involved in taking and 'warehousing electrotypes, many valuable but little saleable works could not bear the cost of a second edition. The amateur who aspires to produce good work even- tually is advised to be particular in every detail, and not to rest satisfied until every mould immersed in the bath is efficiently copied. In experimenting in electro metallurgy there is nothing to be apprehended of an unduly difficult or impracticable nature. Cleanliness is essential. Having satisfied himself with his proficiency in copying coins and such-like simple surfaces, the experimentalist may next proceed to more elaborate and more intricate work. To obtain a silvered or gilded copy of the skeleton of a leaf should not be too great a task for him ultimately, and what kind of work is there that is prettier or more interesting ? Supposing that, with the aid of the elastic mould, copies have been obtained of medals, >tc., more or less undercut, let us next direct our attention to plaster casts and other similar works of art. Small and simple busts, etc., should be attempted first. An interesting experiment is to coat a small bust with copper. This is easily effected by first saturating the plaster with bee's-wax or linseed oil — the former by preference — and then applying a good coat- ing of plumbago. Some unimportant portion of the bust has then attached to it the wire connected with the zinc pole of the battery. It is not difficult to imagine that any mould which is in deep relief, or considerably undercut, will, under ordinary circumstances, receive a very uneven deposit, that portion which lies in the immediate neighbour- hood of the connecting wire receiving the lion's share. To ob^date this, a few short pieces of fine wire are firmly attached to the wire from the zinc pole of the battery, and their free ends placed in the hollow and more remote parts of the mould. By this means a more eqxiable deposit is ensured. In the present experiment of copper-plating a bust, only a very thin deposit may be permitted, otherwise there will be a considerable want of definition, the finer lines, which are essential to the character of any work of art, being lost. I have had comjiaratively thick deposits in which the design is somewhat faithfully depicted on both sides of the copy, but such a result can only be looked for after considerable practice. As a rule, the thinner the film, the truer will be the design. COMET FAMILIES OF THE GIANT PLANETS. By Richard A. Proctor, THERE is a f\imily of comets every member of which travels iu an orbit passing near the orbit of Jupiter ; another family every member of which can be similarly associated with Saturn ; others depending in the same way on Uranus ; others on K'eptune : and in fact, so fully has this sort of relation been recognised, that the idea has even been thrown out that a planet travelling outside the orbit of Neptune but as yet unknown might be detected by the movements of a comet intersecting the great plane of plane- tary movement far beyond Neptune's orbit. It may be mentioned, indeed, in passing, that the comet of 1862, which has been associated with the meteors of Aug. 10 and 11, intersects the plane of planetary movements at a place about as far beyond the orbit of Neptune as that orbit is beyond that of Uranus, and that it has been held probable that at that distance an as yet undiscovered giant planet mav travel. This remarkable relation among the orbits of the comets which travel periodically around the sun has been inter- preted by supposing that all such comets were drawn in from outer space by the sun's attraction, and prevented from returning to outer space by the disturbing influence of one or other of the giant planets. If we suppose a comet, drawn sunwards past the orbit of Jupiter, to be so perturbed by the action of that planet as to lose a consider- able portion of its velocity, then that comet would travel thereafter on an orbit passing close to the point on Jupiter's orbit where it had been thus perturbed in such sort as to become an attendant on the sun. But in the first place the explanation requires that the original orbit of the comet should have passed near to the orbit of Jupiter, and a little consideration will show that there should be millions of comets for each thus travelling, — a numerical relation not found to exist among the cometic systems. And secondly, while the explanation would be valid enough were a comet a solid globe or very small, it fails utterly when we recognise that a comet is a flight of bodies occupying a very large extent of space. It can lie shown that supposing a comet's head to be but 10,000 miles in diameter, and formed of discrete meteoric masses, then if the comet came near enough to Jupiter for its centre to be disturbed in the way the theory requires, those meteoric masses nearest to Jupiter would be so much more disturbed as to be sent on very different orbits, while the new orbits of those masses farthest from Jupiter would be so much less disturbed that their orbits would also be entirely diffe- rent. The theory that such comets have been introduced from without fails utterly in the presence of observed facts, and would never indeed have obtained acceptance for an instant but for the carelessness with which such theories are too often dealt with, being presented as abstract ideas instead of being tested in measure and quantity. The existence of the comet families of the giant planets can scarcely be explained without assuming, what we have already in another way been led to recognise, — the ejection from the giant planets of masses of matter in eruptions akin to those which take place in the sun. Whether such eruptions take place now in the giant planets or not would be difficult to prove, for although we have evidence of tremendous disturbances, we have nothing to show con- clusively that these would suffice to eject matter for ever from within these planets' globes. Whether a careful study of the region outside the discs of Jupiter and Saturn would reveal aught throwing light on this matter, I am not prepared to say ; but I am certain the edges of the discs of the giant planets are worth much more careful study than they have yet received. Undoubtedly many of the comets of Jupiter's family must have been added to the solar cometic system hundreds of thousands, if not millions, of years ago. But quite possibly both Jupiter and Saturn still eject matter from time to time with such velocities from their interior that it passes away never to return to them. In this as in many other features Jupiter and Saturn resemble the sun. They may be regarded as telling us in some degree what was the past of our own earth, when she was full of the fiery vigour of planetary youth. But they tell us more clearly what will be the future of our sun when the glowing vapor.iising masses now surrounding him have lost their intense lustre, and ceasing to possess his present life-giving qualities he is approaching the condition of dark suns which exist already in immense numbers within our stellar system. Erkatum.— In the third line from the bottom of the paragraph on Liniacy Law Reform, on p. 470 of Vol. Y., "inanre" should be "imi:iu;e." ♦ KNOWLEDGE ♦ [JCLY 4, 1884. PHOTOGRAPHING A FLASH OF LIGHTNING. THE accompanying engraving was made directly from a iihotoLjraph sent to us by Mr. W. C. Gurley, of Marietta Observatory, who writes as follows : — " The reproduction of a flash of lightning by photography would, a few years since, have been deemed quite an impos- sibility, but the introduction of the rapid bromo-gelatine process has rendered it not only possible but comparatively easy of accomplishment. " The accompanying photograph is from a negative taken by myself during a thunderstorm which passed several miles south of the observatory on the evening of May 4. " Wheatstone has demonstrated by direct experiment that the duration of a single flash of lightning cannot possibly exceed a millionth of a second. That a photograph showing the detail of the one mentioned could be taken in this in- appreciably short time seems quite wonderful, not to say incredible. The plate employed was one of Cramer's extra rapid, and developed with strong pyrogallic developer. " It will be observed that the flash is not of the usually depicted zigzag form, and that it seems to be alteroately contracted and expanded in its passage through the atmosphere. " Taking the interval between the flash and the report, I estimated its distance from the camera to have been about five miles." — Scientific American. The report ou the composition and quality of daily samples of the water supplied to London, for the month ending May 31st, 1884, by William Crookes, F.K.S., William Odling, II.B,, F.R.S., F.R.C.P., and C. Meymott Tidy, M.B., F.C.S., says:— "Of these 189 samples of water, the whole were, without exception, clear, bright, and well filtered. The quality of the water supplied to the metropolis during the past month, as indicated by its state of aeration, and high degree of freedom from colour and excess of organic matter, was excellent. Its perfect filtration was shown by the absence of even a trace of suspended matter in any one of the numerous samples submitted to examination." THE ANTARCTIC REGIONS. Br RicHAKD A. Proctor. THERE are parts of our earth of which we know less than of the moon, or even of some of the planets. The eyes of the astronomer have looked upon the unattain- able .summits of the lunar mountain.^ : he has studied the arid wastes which lie within the lunar craters ; he has mfasured the light which these regions reflect — nay, even to the degree to which they are warmed under the blazing sun of the long lunar day. Passing beyond the moon, the astronomer has studied the lands and seas of a world which has justly been termed a miniature of our earth : he has watched the clouds which form over the continents and oceans of the planet Mars, and are dissipated even like our own by the solar rays ; he has determined the very con- stituents of that planet's atmosphere. But more than this, the astronomer has actually studied the condition of parts of Mars, where (if analogy can be trusted) the very inha- bitants of that world are unable to penetrate. The ruddy orl) which during the spring months was now conspicuous in our skies presents to the astronomer its Arctic and Antarctic wastes. He is able to watch the gradual increase of either region as winter prevails alternately over the northern and southern hemisphere of Mars ; he can measure their gradual reduction with the progress of the Martial summer ; aud he can infer from their aspect that even in the height of summer there still remain ice-covered regions so wide in their range as doubtless to defy the eflbrts of the Martialists to penetrate to the poles of the globe ou which they li\e. So that where most probaljly no living creature on Mars has ever penetrated, the astronomer can direct his survey ; and questions which no Maitial geographer can pretend to answer the terre-strial astronomer can discuss with a considerable degree of confidence. It is the same even with the more distant planets Jupiter and Saturn. Despite the vast spaces which separate us from these orbs, we yet know much respecting their physical habitvides ; and whereas our knowledge of our own earth is limited by certain barriers as yet unpassed, and probably impassable, there is no pait of the surface of either of the giant planets which has not come under the astronomer's scrutiny. These considerations suggest in turn the strange thought that possibly the unattained places of our earth have been viewed by beings which are not of this world. I say possibly, but I might almost say j^'^^'- hahhj. It seems in no degree unreasonable to sup- pose not merely that the earth's sister-planet Venus is inhabited, but that some creatures on Venus possess the reasoning powers and the insight into the secrets of Nature which have enabled the inhabitants of Earth to study the orbs which circle like herself around the sun. If this be the case— if there are telescopists in Venus as skilful as those inhabiting our earth — they are able to answer questions which hitherto have baffled our geographers. They may not, indeed, have the means of ascertaining details respecting the structure of our continents and oceans. They cannot know, for instance, whether the region to which Livingstone has penetrated is, as he supposes, the head of the river we terrestrials call the Nile, or, as others suppose, is in reality the head of the Congo. For certainly no tele- scopic powers possessed by our astronomers could give us information on such points, if our position were inter- changed with that of the inhabitants of Venus. But astronomers in Venus can, without excessive telescopic power, inform themselves whether our polar regions are JixY 4, 1884.] ♦ KNOWLEDGE ♦ like the corresponding regions in Mars — or whether, as many geographers suppose, the Arctic regions are occupied in summer by an open ocean, while in the Antarctic regions there is a large continent. A new interest was given to inquiries respecting the condition of Arctic and Antarctic regions by the circum- stance that the expedition of the Challenger is expected to bring us information respecting the latter regions, while application has been made for Government assistance to- waids an Arctic expedition. I propose to consider, now, some of the questions which are connected with Antarctic research, and in particular to discuss the probability of the existence of great continental lands within the Antarctic ■circle. Before proceeding to consider these points, however, I have a few remarks to make on the question of Govern- ment aid to this branch of geographical research. It should be remembered by those who discuss this sub- ject that the first exploration of the polar regions of our earth had a commercial origin. It was supposed that by finding a passage round the northern shores of the American continent communication with China and the £ast Indies would be facilitated. A way had been found round Cape Horn, but the way was long, and the storms which rage in Antarctic seas rendered the route uninviting to the contemporaries of Magellan. The natural supposi- tion in those days was, that voyagers from the great -maritime northern countries — from England, from Spain and Portugal, or from the Netherlands — would find their advantage in sailing northwards rather than southwards. Hence the long and persistent efforts made to discover a north-western passage. Nor were the more directly Arctic voyages of Hudson and Richardson conducted with any other primary purpose. It is indeed manifest, as any one will perceive on examining a terrestrial globe, that a north- -eastem course would avail nearly as well as a north- western for reaching eastern countries from Europe, and that a directly polar course would be better than either, if only (as Hudson hoped) a safe passage might be found through the Arctic seas. Gradually, as the hope of finding a north-western passage available for commerce died out, other circum- stances encouraged persistence in the etibrts which had been made to penetrate the regions lying to the north of the American continent. There was much, indeed, in the desire to accomplish what had foiled so many ; and it may be questioned whether this desire had not a good deal to do with the appeals which were made for Government assistance, as also with the ready response of Government to those appeals. Nevertheless, a real scientific interest had become associated with the search after a north-west passage. The magnetic pole of the earth was known to lie somewhere amid the dreary archipelago, with its ice- bound inlets and glacier-laden shores, through which our Arctic seamen had so long attempted to penetrate. There, also, lies one of the northern poles of cold ; while the con- figuration of the isothermal lines (or lines of equal tem- perature) in the neighbourhood, shows how some influence is at work carrying relative warmth from the Atlantic towards the North Pole, and leaving the regions on the west of that course exposed to a degree of cold greatly more intense. To these considerations others connected ■with the whaling trade were added, though I am not pre- pared to say that (so far as the question of Government assistance was concerned) these considerations had very great weight. It cannot be denied, however, that at a certain stage in the history of Arctic voyaging, the mere barren ambition to attain or approach the North Pole of the eaith, was set in advance of more practical considerations. We find, for instance, that in the case of Parry's " boat and sledge " expedition from Spitzbergen polewards, certain sums of money were set as a reward for reaching such and such northern latitudes, the sum of ten thousand pounds being the prize for attaining the North Pole itself. It would not be easy, perhaps, to assign any sufficient reason for the renewal, by a scientific expedition, of those arduous explorations in which Wilkes, d'XJrville, and (espe- cially) the younger Ross, discovered all that is known about the Antarctic ice-barrier. There was much, indeed, in the results obtained by Ross to invite curiosity on the one hand, and on the other to show that the Antarctic regions can be penetrated successfully in certain directions. It seems far from unlikely that other openings exist by which the southern pole may be approached, than that great bay, girt round by steep and lofty rocks, where Ross made his nearest approach to the southern magnetic pole. I shall presently indicate reasons for believing that the Antarctic as well as the Arctic regions are occupied by an archipelago — ice-bound, indeed, during the greater part of the year — but nevertheless not altogether impenetrable during the Antarctic summer. Yet there is little to encourage any attempts to explore this region otherwise than in ships specially constructed to encounter its dangers. THE (To he continued.) INTERXATIONAL EXHIBITION. HEALTH TI.— WATER AXD WATEE SUPPLIES. 4 PRELIMINARY inquiry into the nature of water i\ would more become a treatise on chemistry than the present pages ; yet, nevertheless, some definition must be given of this all-important matter to enable our readers to understand exactly what we have to deal with, and how intimately the subject is interwoven with all that concerns our healthy being. Pure water, as such, does not come within the scope of our ordinary life ; it only occupies a legitimate place in the laboratory of the experimental chemist, who defines it to be a combination of the elements hydrogen and oxvgen in the proportions of two volumes of the former to one of the latter, or graphically, H — O — H. For further information on the physical properties of pure water, and of its elemental com- ponents, we must refer the reader to the numerous text- books on chemistry now in circulation. A popular lucid account of the subject may be derived from a perusal of the excellent little handbook entitled " Water and Water Supplies," by Professor Attfield, and published under the direction of the Executive Council by Messrs. Clowes ife Sons, in the Exhibition buildings. Chemically, pure water, then, does not come within the field of our obser- vations as inquirers into the usefulness of that medium. What, then, have we to deal with 1 The water with which we are familiar may be defined as a compound of very variable character. Each sample would have to be analysed before we could pronounce with decision its distinctive attribute. In general, however, the term pure water may be taken to signify water which con- tains in solution and admixture various solids and gases, which, for domestic purposes, are not only harmless, but useful It thus resolves itself into a question of relative utility ; we say relative, because we speak of ourselves as human beings. Certain waters which are eminently suited to the propagation and nutrition of other living thinors, 8 ♦ KNOWLEDGE ♦ [July 4, 1884. •would be absolutely poisonous to Homo sapiens ; indeed, such deleterious waters are often so constantly associated ■with certain forms of life, both animal and vegetaVjle, that their presence is always sufficient to determine the character of the liquid as unsuitable to man. The question may here be raised that it is the ingestion of the living things •which produces the evil effects, and that is very true to a large extent; but besides the growth and multiplication within our bodies of disease-producing germs, the waters which they inhabit are chemically contaminated ; the fer- mentative action which they set up therein results in the elimination of non-living substances, which, apart from the oi'ganisms themselves, are highly poisonous. And we would here suggest that the first rapid, and in some cases almost instantaneous, phase in zymotic diseases may not be so much due to the growth and development of the germs themselves, as to the poisonous ferments which they create, and which are imbibed along with them. As instances of what we would here imply, we may point to the fermentative action of the yeast-plant (Sac- cJiaromyces cerevisi(e)*, which produces alcohol, and which, even after death through the administration of ether,t gives rise to a non-living soluble ferment, which transforms cane into grape-sugar. The alcohol and the glucogenic ferment retain their properties after the yeast-plant itself has ceased to exist. The butyric acid remains as butyric acid after the bacterium [Bacillum sublilc) has passed away. Foul gases and putrefactive fluids remain after the death of Bacterium termo ; and may we not with reason expect to find that the greater part of the mischief which ends in splenic disease, pulmonary tubercles, and leprous deforma- tions, is the immediate cause of the ferments produced by their respective bacteria {Bacillum anthracis, B. tuher- culosus, and B. leprcr) ; and that our physicians in their setiological studies might direct some of their ex]ieriments towards finding antidotes for these poisons ? Cannot a specific be found to neutralise the ferment of B. ttcher- culosits, and be applied so as to result in the reduction of tubercle in this way 1 We trust that the time has arrived when experimental inquiry shall partially turn from the inoculation of guinea-pigs and the preparation of micro- scopical slides from the tissues of the poor innocent victims, to the chemical side of the question, where the disease germs only shall be sacrificed at the altar of ^sculapius.l We are not digressing ; we are only trying to show by living examples how very much this aspect of the water question has been neglected. Pages of matter have been devoted by various authors to the consideration of the purifying processes of Nature, such as the open flows of water in rivers, aqueducts, down cataracts, and gullies, and its percolation through the soil, subsoil, and rock to wells of great depth, all the arguments for which are based upon the theory that, through oxidation of organic remains, the harmful azotised and carbonaceous matters are converted into useful nitrates and carbon dioxide, and the water thus fitted for domestic purposes. Now, all this is very true about dead forms of life, but what about the living 1 And, * In reply to an inquiry as to the average size of the yeast cell, we may state that our own measurements were taken from the larger variety of the plant known as " German," " dry," or " baker's " yeast, viz., 12 micromillimfetres, or about 1-2000 inch. Ordinary brewer's " barm," however, usually furnishes cells which measure only 8fi, or 1-3200 inch approximately. t Hoppe-Seyler, in " Watts' Dictionary of Chemistry," second Supplemeut, London, 1875, p. 522. t The prevention of zymotic diseases by a prior removal of the germs from food substances does not so much concern our medical brethren, as our purely chemical confreres, naturalists, and practical workers. We may leave the ^l^sclepiadm to cope mth Archseus and his emissaries after the mischief has been done. still more, what about the nascent living or germ ccmdi- tionl All Bacteria, but more particularly the forms termed Bacilli, are excessively minute bodies, chiefly of rod-like* shapes in their adult condition ; they are assigned to the group of ScMzomycetes amongst the lower Fungi, Micro- coccus is a rounded form, and averages about ^ ,^ ;, „ „ in. in diameter, or only 1 /i.t Bacterium termo, the active agent in putrefaction, is about 1 ^ in breadth by \-i> fx in length. The majority of Bacilli are infinitesimal in size ; in fact, in a specimen of the Bacillum of Oriental leprosy which recently came under our notice, it was difiicult to detect any signs of the germs with a magnifying power of even .500 dia- meters ; but with 1,000 diameters we were able to distinguish certain nests (stained methyl violet), in the substance of the fine connective tissue of the papill;e of the skin, which latter was tinged with Bismarck brown. On careful ex- amination, these nests were seen to be composed of copgeries of little rods, or Bacilli. So much, then, in proof of the minuteness of these disease-germs. The presence of oxygen and carbon dioxide given to the water can scarcely be held as destructive to such forms of life ; they would rather tend to an opposite result. However that may be, bacteria are most tenacious of their existence ; otherwise, how could they have survived the ill-treatment received at the hand of Dr. Bastian and other observers ? According to Eidami they are killed by a fourteen hours' exposure to a temperature of 40° C, or a three hours' exposure to 4.5° C. Their yrms when drt/ can resist 110" C, but suc- cumb when 120° C. is reached§. Tyndall|| also has shown that infusions with bacteria are not sterilised unless they are subjected to prolonged -boiling — about four hours. When moist, however, they are more easily destroyed ; and here is the bearing of the germ question upon the water supply : — The activity of the germs seems to be manifested only in the presence of moisture. Recent researches, especially those communicated to the Parisian Academy of Sciences, have shown that the air teems with these primitive forms ; they have been actually strained therefrom, and an ap- proximate estimation of their numbers in a given volume of the atmosphere at different seasons, places, and under specified conditions has been formulated. It has been shown that after a shower of rain the air is considerably purified of these organisms ; they are caiTied down by the water into the soil, and there they increase and multiply under favourable conditions to vitiate the air once more with their countless descendants. Their methods of reproduction have been ascertained through microscopical investigation ; and, so far as we are aware, they are propagated (a) by fission, or division of an adult into two individuals by constriction, and subsequent separation of the parts ; (/5) by a process closely allied to fission, called the zooglaa stage, in which division seems to be carried on in a passive state, embedded in a jelly-like surrounding ; and (y), as first shown by Koch,ir and verified by Ewart,** through elongation of the rods into filaments, the internal portion of which becomes subdivided into small, highly refractive particles or germs, which are liberated through the bursting of the parent envelope. * Bacterium, from the Gr. [iaxTpov, a rod or staff. BacHlum, dim. of Lat. haenlum, a little rod. + Here, as elsewhere, we shall denote the micTomilHmifre by the Greek letter /i. 1 /j =00000397 inch. X " Beitrage zur Biologie der Pflanzen," by Cohn, Vol. I., p. 223. § Sanderson and Ewart iu " Proc. Koy. Soc.," Vol. 28, p. -177. il " Trans. Roy. Soc," Vol. clxvii., pp. 140 et 177. ^ " Beitr. zur Biol. d. Pflanzen," by Cohn, Vol. ii., p. 3. ** " Proc. Roy. Soc," Vol. xxvii., p. 474. July 4, 1884.] ♦ KNOW^LEDGE ♦ 9 This last process has been termed multiplication by en- dogonidia ; and we cannot but fancy that it is to its potent agency that we are indebted for the myriads of germ forms which pollute the atmosphere. The inhalation of these germs, however, does not seem to be all-powerful in the spread of infections, as they are to a large measure in- tercepted by the natural filter, commonly known as the nostrils, and are further checked in their growth by the unfavourable secretions and gases given off by the glandu- lar organs of our bodies ; so that in the struggle for ex- istence they are compelled to succumb, and their harmful action is thus arrested, or reduced to a minimum. The "nervous" or other pathological condition of the individual, of course, opens the gates even to these dry germs ; but it is averred that persons in a normal state of health are able, at most times, to withstand their ravages. When, however, they gain access to their hotbed of water, their activity is so stimulated that the poor unfor- tunate who gives them a reception must inevitably become a prey to these poisonous parasites. It thus becomes in- cumbent on all those to whom the welfare of their fellow- beings is entrusted, to the heads of families, as much as to water-supply companies, to learn something about these matters, and to seek for remedies, such as may lie in their power, which shall effectually prevent the spread of disease and the increase of mortality. In this paper it has been our endeavour to show how seemingly insignificant yet subtle an influence, — an in- fluence which can baffle the chemical or even the practised microscopical detective, — is at work undermining the con- stitutions of thousands of healthy lives. We shall in continuation of this subject show how those evils might be remedied, and what has already been done by practical workers in this field of inquiry. Our next communication will deal with the phy.siographical aspect of the water- supply question, suitably illustrated. ON PECULIARITIES OF SIGHT, AND OPTICAL ILLUSIONS.* By Natii. E Greek. A MOST interesting and instructive paper might be written on the subject of optical illusions in connec- tion with astronomical observation. How many minute companions to stars, how many extra satellites of planets, how many strange appearances, have been seen by certain observers, and by them only. Yet those observers believed in their own sight, and were fully convinced of the actuality of the appearances reported. May not an ex- planation be found in the eccentricities of optics or in personalities of vision 1 The object of this paper is to draw attention to the subject, and by a few confessions to induce others to take it up, being assured that, although the individual may feel depressed, the great cause of truth will be advanced by the discussion. And first, with regard to minute points of light. The writer has experienced a difliculty when searching for faint ■somites, or the inner satellites of Saturn, in decermining which are real and which spurious points. The eye having a tendency to produce these where they do not exist, aud the real things being only seen by glimpses, it requires great patience, and frequent repetition of a point in the same position to be assured of its existence. A friend once re- * From the Astronomical Register. marked when searching for the satellites of Saturn, " How- many do you want me to see, for I can see as many as you like." Surely this optical illusion will account for the ap- pearance of many minute object?, that others have been unable to confirm. Another illusion is the persistence of an object on the retina after the eye has been withdrawn from the telescope. This has occurred after long observa- tion of Jupiter with an 18-in. reflector. On removing the eye from the instrument, to make a drawing of what has been observed, a clear, bright disc has so interfered between the eye and the pencil-point, that an effort was required to remove the illusion before the drawing could be made. May not this retention of an object on which the eye has long been fixed account for the appearance of a satellite through the limb of Jupiter, the image of the satellite being con- tinued on the retina after it had passed behind the planet ? * But what shall we say of the reported visibility of the unillumined portion of Venus % This phenomenon has been reported so frequently that it seems like heresy to doubt the fact. We are not referring to the fine ring of light that surrounds the disc just before immersion at a transit, or when Venus is very near the sun at inferior conjunction, but to those reported appearances, in full daylight, when the planet is at greatest elongation. The writer had a friend who could always see the dark side, even in the finder ; he has shown Venus to another unaccustomed to astronomical observation, when the planet was on the meridian and about half full. " How is it," said he, " that I see the whole of the round ? " And very recently, when friends were in the observatory, and viewing Venus, on putting the question, " Can you see the unillumined por- tion ?" the answer has been, " Now you mention it, I think I can." In all these cases, and many others, the writer has been unable to perceive that which others have seen. One more illusion, and we have done. When observing the ring of Saturn, and especially the outer ring, for evi- dences of division, a very distinct shadow of Saturn has appeared on the following portion of the sky — this is, of course, a simple optical defect, arising possibly from the same cause as the dark forms that are seen after looking at the sun. It is just possible that a similar effect follows Venus, and to some eyes appears like the dark portion of the planet against the sky. f There is a fine opportunity before us of testing some of these appearances, and the readers of this journal may be induced to record their experiences. DrRiXG the year 1883, Professor Simon Xewcomb, U.S.X., visited Europe, by order of the United States Government, for the purpose of collecting information respecting the most recent im- provements in astronomical instruments. His report to the Secre- tary of the Xavy contains a good deal of valuable information for the practical astronomer. He speaks highly of the definition of the enormous refractor at Vienna. He also commends the method of supporting mirrors devised by the Mil. Henry of Paris, adding, however, that it has, so far, not been employed with reflectors ex- ceeding 12 in. in aperture. He by no means speaks with unmixed admiration of the much beptiffed "Equatorial circle"; while he has little but praise for the Strasburg circle under construction by the Messrs. Eepaold. One of the most interesting things described by Professor Newcomb is the extremely shallow form of mer- cury basin employed for reflection - observations at Strasbnrg, Leyden, <&c. * This is, however, inconsistent with the accounts given by Mr. Todd, of Adelaide, and his assistants. — B. P. t This seems to me just impossible. The dark shade seen in this way is of the same shape as the luminous object, and similarly situated : the *' terminator " of Venus is not of the same shape as the outline of the unillumined part of the disc. — B. P. 10 • KNOWLEDGE • [July 4, 1884. THE EVOLUTION OF FLOWERS. By Grant Allen. some higher lilies. ALL the true lilies with which we have dealt so far have had bulbs to grow from, and have been, on the whole, very succulent and herbaceous in character. They have also persisted in the primitive lily habit of producing dry capsules, each of the three cells in which contained numerous seeds. There are, however, some higher types of lily, not very largely represented in our British flora, which differ con- siderably from the tulip, the frilillary, and the tiger-lilies in one or other of these central characteristics. I propose briefly glancing at two of these to-day, the common aspara- gus {Aspararjus officiimUn)a.odthe butcher's broom (Emeus aculeatus). They are our two English representatives of the sub-order of Liliacere known as Asparageie. Dismiss from your mind entirely the ordinary garden Fig. 1. — Asparagus Officinalis. notion of asparagus, as a thick, stumpy, succulent shoot, and try to realise the life of the wild plant itself as it grows by the sandy, tideless levels of the Mediterranean, or far more sparingly on a few isolated rocky headlands of our own Cornish or Irish coast Essentially a maritime weed, the wild asparagus has, instead of a bulb, a deep creeping root-stock, buried far out of harm's reach in the sand or the crannies ; and from this stock it sends up every spring a few soft, scaly, annual shoots, thin and wiry, which branch out afterwards into tufted feathery heads of minute foliage. In our gardens, we trench and manure the selected and cultivated variety, so that each year the annual stems grow very large, high, and bushy, and collect abundant material for the next spring's growth, which they conceal during the winter in the buried root-stock. Hence the young shoots in the garJen kind have become unnaturally large, thick, and luscious. But in the wild state, asparagus seldom attains more than one quarter the height of the Ijig, luxuriant, cultivated variety, and its spring shoots are far thinner, stringier, and more woody in texture. On the edible young stems of the garden asparagus, everybody must have noticed a few short, stumpy scales, generally of a faint mauve colour ; and these are almost the only true leaves the plant ever produces. When it grows older, the place of foliage is fulfilled by the fine clustered hair-like green points, which are, ia fact, very small branches, or, if you like to be extremely scientific, abortive pedicels (that is to say, flower-stalks whose buds and blossoms have never developed). Look very closely at the base of each such cluster — the full-grown garden asparagus will do quite as well for this purpose as its wild ancestor — and you will see that it is enclosed by very tiny dry scales, each of which is really a bract or leaf, s-imilar ta those on the spring shoots. From the axils or angles made by these bracts with the stem, the cluster of abortive pedicels springs, just as each separate blossom in a wild hyacinth or a common spotted orchis, springs from a small bract of a far more conspicuous character. One may say, in fact, that each cluster of so-called leaves in the asparagus answers to a whole head of flowers in the bluebell or orchis, only that the actual blossoms themselves are in this case never developed. Why the asparagus has thus taken to producing these innumerable pedicels instead of true leaves would be a long, and diflicult question to answer fully. It must suffice here to say briefly that in many plants of dry places (for example, in the stonecro])s) the stem and branches as well as the leaves are filled with chlorophyll, and help to perform the foliar functions. In others (for example, in the cactuses) the true leaves have dwindled away absolutely to nothing^ because the succulent stem performs their functions better under its own peculiar circumstances. In asparagus, the true leaves remain only as protective scales, but the work of foliage has been taken on by the stem and pedicels, simi)ly because they could do the work more conveniently. The flowers of the asparagus are small and greenish, and at first sight very inconspicuous. On looking closer, how- ever, you will see that they are perfect little lilies, each with six distinct perianth-pieces — that is to say, three sepals and three petals, the distinction being here well marked — and the usual six stamens and three-celled ovary. INIany of the flowers, however, have stamens only : others have pistils with abortive stamens : the plant is just beginnini; to separate the sexes in distinct blossoms. But the separation has not yet gone far ; none of the female flowers have as yet quite lost their stamens, though they are reduced to useless filaments bearing abortive anthers. Indeed, a few blossoms on each plant usually still retain both stamens and pistil. Unattractive as they are in colour, the aspa- ragus flowers have a delicate perfume, and secrete abundant honey ; hence they are visited and fertilised by hive bees- and a few other insects. But tlie most marked peculiarity about the asparagus, as distinguished from the other lilies we have hitherto ex- amined, is certainly the fact that it produces red berries, instead of dry green or brown capsules. This berry has, of course, been produced, like all others, by the interven- tion of birds, which thus distribute the seeds in the best possible situations. Accordingly, the plant is able to lessen the number of seeds in each cell to one only. To be sure, the flower has two ovules or young seeds in each cell of the ovary ; but as the fruit ripens, one of these usually becomes abortive. This is just the exact reversal of what we saw happen in an earlier stage of evolution ; and yet it is only July 4, 1884.] ♦ KNOWLEDGE ♦ 11 a further step in the same dii-ection, under a sliglit dis- guise. We noticed that the earliest monocotyledons, such as the alismas, had many carpels in every flower, each con- taining one seed. In the simpler lilies, such as the tulip and fiitillary, the number of carpels was reduced to three (united in a single capsule), while, by way of compensation, the seeds in each cell were increased to several. But in the asparagus, the improved mode of dispersion by the aid of birds enables the plant still further to simplify its plan by reducing the number of seeds in each cell to one. It thus effects the greatest possible saving both in fertilisation and in dispersion of seeds. The butcher's broom is a still more singular modification of the lily type, in which the foliar functions are performed by flattened, leaf-like branches, exactly simulating true leaves. It stands alone among Britisli monocotyledons in attaining a shrubby, woody, tree-like habit. The branches are so extremely like leaves in outward appearance that their true nature can only be discovered by reasoning and analogy. Most of them bear on their under surface (or rather on the upper side, which is so twisted as to turn Fig. 2. — Ruscus Acnleatus. downward) a single small, whitish lily flower, having six distinct perianth pieces, and either three stamens or a three- celled ovary, for the division of the sexes is here almost complete, though a few hermaphrodite blossoms occasionally occur. If you look very closely, however, you will see that each flower is borne on a small pedicel, united along its whole length with the leaf-like branch (well shown at b in the accompanying woodcut), and that a very tiny scale or bract lies under every blossom. Similar very small scales, the last relics of the true leaves, now abortive, are found beneath the leaf-like branches. The flowers and fruit seem accordingly to grow out of the middle of a leaf, a peculiarity which gives butcher's broom a very strange and uncanny appearance. In the immature ovary there are two ovules in each cell, but, as the fruit ripens, one in each cell always becomes abortive, so that at most there are but three seeds in the berry. More often, how- ever, only two perfect seeds are developed, and it is not uncommon to find berries with only one ; so that butcher's broom, in fact, carries all the tendencies of the asparagus just one stage further. The berries are bright red, and very attractive to birds, but the seeds are excessively hard and indigestible. Butcher's broom is a glossy evergreen, and the leaf-like branches are stirt' and prickly, effectually de- terring cattle from browzing oft' its tempting foliage. CONCEIT (FOR SELF AND FAMILY). By Eich.\rd a. Proctor. MY friend Mr. Foster has touched on the thought — a sound and suggestive one — that what is called patriotism is often only a wider development of selfishness. The least cultured among men are personally selfish, family- selfishness is less contemptible but yet contemptible enough, and the selfishness of so-called patriotism is by comparison, but by comparison only, almost respectable. (I say so-called patriotism, for real patriotism is as distinct from the quality in question as just self-regard is from pure selfishness.) But may we not in like manner recognise in false pa- triotism somethiog akin rather to self-conceit, and conceit of family, than to selfishness of the personal or of the- family kind 1 And may we not also distinguish between self-conceit and self-knowledge, precisely as we distinguish between selfishness and due self-regard t Self-conceit is so obviously a fault of the uncultured and ill-developed mind that it is hardly necessary to dwell on the evidence of inferiority which it attbrds. This is- curiously shown by the way in which this quality is manifested in children. Almost all children are more or less conceited, — generally more, — and grow out of their con- ceit (if it is in them to develope higher things) as they get older, just as they grow out of the monkeyhood of earlj- infaucy (often a very pretty monkeyhood) and the savagery of later childhood. Of course, many remain self- conceited to youth and manhood, or through life. Our less-developed classes are as inherently self-conceited through life as al) or nearly all men are in early childhood. That supreme self-conceit presented in Tennyson's fine picture of the- Northern Farmer, will be found, by any one who takes the trouble to search for it, in ninety-nine out of a hundred of' our peasantry and men of purely agricultural life, even when the age supposed to be full of wisdom and experience has been reached. It seems incredible, but talk to men of the class to which Tennyson's " Northern Farmer " be- longed and you will find many who doubt (at the bottom of their minds) whether Godamoighty quite knows their iuU value in the world. " Does Godamoighty knaw what a's^ doing a taakin o' me ? " asks the old pagan, and we smile at his amazing self-conceit ; yet it is common enough, and even outside those classes whose pursuits involve little calculated to raise the mind's level or to widen the ideas. Family conceit is less obviously a sign of incomplete development ; yet there can be little mistake about its real meaning when we rightly apprehend its nature. The child shows family conceit a little later than self-conceit, but the quality it, essentially one belonging to childhood either of the individual or of the race. The Northern Farmer^ though he had not passed much beyond the stage of self- conceit (" See bow quolity smoiles when they sees me a passin' by "), had some family conceit too, if we fully understand his reference to "Jones, as never mended a 12 ♦ KNOWLEDGE ♦ [July 4, 1884. fence," and " Robinson, as arn't a haporth o' sense." Doubt- less the Joneses and the Robinsons seemed to him to belong to an inferior race, besides being individually and personally contemptible. But family conceit is more widely spread (as well as a wider form of conceit) than conceit of self. We find it in races a grade higher than those which supply the chief developments of personal conceit. It yields more slowly before culture and knowledge. We see it in families which have every means of recognising the inherent absurdity of the feeling, who have before them as clearly the evidence of the insignificance of particular families as they have before them the evidence of the personal insignificance of the individual man. It ia indeed true that, among the worst developed races, family conceit is more prevalent than in races which have had better advantages. The Flanagans and Dohertys are naturally full of pride of family, and prepared by breaking heads after due coat-tail-treading to show the superiority of the race which may be has not produced in all time a single person above or even quite up to the average ; and in like manner in our own country we find a steady though dull form of family pride in the Noakeses and Styleses of remote and undeveloped country districts. But the failing is found outside such races as these. It can not only be recognised in families called noble and royal (it comes out amusingly for instance, so far as I can judge from extracts, in some royal books which have recently been published in this country) but it can be recognised also in those whose opportunities of culture and study should have taught them better. Nay, sometimes even that special study of biological laws wliich should show that each individual represents scores of families and has qualities which can no more be assigned to one family than the qualities of a river can be assigned to one out of its hundred sources, fails to correct this foolish feeling, which like others of our lower qualities is innate and scarce to be corrected by culture, reasoning, or acquired knowledge. What however can be much more absurd in reality than to find a family claiming for its members — or quietly assuming without claiming openly — superior qualities 1 We know that the very existence of family conceit is a mark of want of sense, a sign of inferior culture. But apart from this we know that every person born into the world shares multitudinous faculties and qualities inherited from hundreds, thousands, nay tens and hundreds of thousands of foregoers. When a man boasts " I am a Snillum or a Snobbig" he can really only mean that a thousandth part of his blood comes from some remote Snobbig or a Snillum, of presumably better qualities than they recognise in themselves— so that their family history has — by their own account — been one of descent. It is sad for them, but they ought to know best. Still the idea of a family strain is absurd on the face of it, and family conceit is only less contemptible than personal vanity. In a description of the mowing and reaping machine works of Mr. W. A. Wood the following occurs : — " Statement of materials ■we consumed in the manufactm-e of 45,0.32 machines, our produc- tion in 18S3. We give only the principal materials naed. Pig-iron, 10,500 tons; steel, 1,000 tons; wrought and cold rolled iron, 4,500 tons ; malleable iron, l,G0O tons ; coal, 7,000 tons ; coke, 1,000 tons ; moulding sand, 4,000 tons; grinding stones, 225 tons; painting material, 400,0001b.; spring wire, 00,000 lb. ; tacks and rivets, 120,0001b.; brass and composition, 120,0001b.; screws, 10,000 gross ; lubricating oils, 10,000 gallons ; lumber, 10,000,000 ft. ; cotton duck, 90,000 yards ; carriage and plough bolts, 3,000,000. As evidence of the magnitude that the use of self-binding machinery in harvesting grain has attained, we will state that we foi-nished our customers in 1883, 2,500 tons of twine." 3^ebittD2f* SOME BOOKS ON OUR TABLE. What is Art? By James Stanley Little. (London: W. Swan, Sonnenschein ear at her dark limb at 12h. 29m. p.m. at a vertical angle of 271'°. On July 15, the fourth mag. star o Piscium will disappear at the bright limb of the moon at 12h. 53m. p.m., at an angle from the vertex of 60°. It ■will re-appear at 51m. after 1 the next morning, at an angle of 264' from her vertex. Lastly, on the IGth, rather more than half-an- hour before the moon rises, she will have occulted 31 Arietis, a star of the sixth magnitude. Later, at llh. 55m. p.m., this star will re- appear at the moon's dark limb at a vertical angle of 246'. When our notes begin, the moon is in Libra ; but at two o'clock this after- noon she leaves it for the narrow northern strip of Scorpio. She takes until one o'clock to-morrow morning to cross this, and then enters Ophiuchus. This she quits at 10 p.m., on the 6th, for Sagit- tarius. Her passage through Sagittarius occupies until 11 a.m. on the 9th, at which hour she passes into Capricornus, the boundary between which and Aquarius she crosses at 5 a.m. on the 10th. About 3 a.m. on the 13th, she leaves Aquarius for Pisces, and ■continues to travel through that large and straggling constellation until she enters Aries, at 5 a.m., on the 16th. At 8 p.m., on the 17th, she moves into Taurus, which she is still traversing when tiese notes terminate. The "Researches on Astronomical Spectrum Photography" of the late lamented Professor Henry Draper have just been repub- lished, with au introduction and description of the apparatus by Professor C. A. Young, and measurements and description of the plates by Professor E. C. Pickering, together with reprints of Dr. Draper's various papers on the subject. Apart from its enduring importance as a record of a mass of valuable physical facts, and as containing a history of the infancy and youth of Stellar spectral research, this posthumous volume of the great American physicist possesses a high degree of interest, as showing what an enormous amount of scientific work of the highest value could be performed by an absolutely unsubsidised obser\-er. Professor Draper would have felt that he was inflicting as much degradation on science as he would have brought upon himself personally had he gone whining to Congress for " endowment." Like our own Faraday, though, he "had no time to get rich;" and his name will assuredly live in honour when those of the men whose idea of science is narrowed to that of their own pecuniary advancement will have long sunk into oblivion. ' Let Knowledge grow from more to more." — Alfred Tekxtsor. Only a small proportion of Letters received can possibly be in- serted. Correspondents must not le offended, therefore, shouid their letters not appear. All Editorial communications should le addressed to the Editor of Knowledge ; all Business communications to the Publishers, at the Office, 74, Qreat Queen-street, TT.C. If this is not attended to DELAYS ARISE FOR WHICH THE EDITOR IS NOT RESPONSIBLE. All Remittances, Cheques, and Post Office Orders should be made payable to Messrs. Wtuan & Sons. The Editor is not respomille for the opinions of corresponden'.s. No COMMUNICATIONS ABE ANSWERED BY POST, EVEN THOUGH 8TAHPBD AND DIRECTED ENVELOPE BE E^'CLOS£D, LARGE CELLS FOR ELECTRO DEPOSITION. [1322] — Mr. Slingo's last paper on "Electro-plating," in which he refers to the expense of rectangular baths made of pottery, re- minds me of my own experience in the early days of electrotyping (about 1845-6). I made two large tanks for depositing copper 4ft. long, 2 1 ft. wide, and 2 J ft. deep. They were of common deal, put together in the usual way, by dove-tailing; but were double. The outer tank was about 1 in. thick ; the inner tank was made of 1 in. wood, with outside dimensions i in. less all round than the inside dimensions of the outer trough. On the bottom of the out- side tank were a few small blocks about 1 in. square and i in. thick. Thus, when the inner or lining tank was put in its place, resting on these blocks there was a space on all sides and the bottom of J in. thickness between the inner and outer tank. To keep the lining accurately in the middle, I put temporary strips i in. thick down each side. This being arranged, I poured melted pitch into the i-inch space, only in sufficient quantity, at nrst, to flow over the bottom and rise a few inches above the sides, as I anticipated a floating up of the whole of the inner case if all the liquid were added at once. On the following day, after this first pouring had cooled and solidified, I poured more, suSicient to fill the ^-inch space completely, and then left the whole to solidify. Then followed a curious illustra- tion of the viscosity of the apparently solid pitch. The inner case gradually rose day by day, threatening to wreck the whole arrange- ment. I filled it "with water, and it gradually sunk until it rested on the cheek blocks, where it remained when subsequently filled with the copper solution. The second compound trough was similarly treated, and both were used by myself for two years without leakage, and long afterwards by my successor. The copper solution soaks through the porous wood of the inner lining, but is effectually resisted by the sur- rounding wall of pitch. I do not recommend this for silver solu- tions ; the cyanides are alkaline, and will act upon the pitch, and thus, in course of time, the solution will become polluted by a solu- tion of the pitch. This does not happen to the acid copper solution. Now that paraffin wax is obtainable for 6d. per pound, I recommend it as a substitute for the pitch, and have no doubt that cells thus constructed will be found available for all kinds of solutions that are used cold. W. Mattiec Williams. COLOUK-LANGCAGE. [1323]— The construction which Mr. Titchener (question 1320) puts on my sentence is justified by the wording, but so general a statement must be interpreted by the spirit and context, rather than solely by the letter. For it is not pretended that uncivilised folk can so discriminate between the subtle gradations of colour as to have words for every shade, but it is none the less certain that where terms are invented for colours, the concrete precedes the abstract. Mr. Titchener's question gives me the desired occasion to call attention to my friend Mr. Grant Allen's delightful book on the "Colour Sense" (Triibner & Co.), and especially to the last chapter " On the Growth of the Colour- Vocabulary," from which the following is quoted : — " The earliest names must be names of things, or of visible and Jdly 4, 1884.] - KNOWLEDGE • 15 auJiblc actions. . . When we wish to express a hitherto unnamed colour, the simplest way of dointj it is to taue an object which possesses that colour and apply its title as an adjective to the thing which we wish to describe. A particular shade of very light yellow has no distinctive name, but we must call it something for some special purpose, and so we thiuk of its nearest common representative, a primrose. Thenceforward the new name becomes an adjective, and we ask naturally for a yard of primrose ribbon. Now, what we see civilised men doing to-day under our own eyes, primitive men did centuries ago, when they framed the earliest colour names. It would seem at present as though the various terms for colours might be divided into two classes — the truly abstract, such as blue, green, yellow, and the concrete used abstractly, such as lilac, orange, pinlc. The former class a]>pears to have no other meaning than that of pure colour; while the latter class are clearly derived from the names of concrete objects. But in reality the difference between them is merely one of time. Abstract colour-terms are the names of concretes, whose original significa- tion has been forgotten" (pp. 252, 253). Edward Clodd. DIVISIBILITY BY SEVEN. 8 931 P24 026 oys 518 I 423 -123 [1324] — Mr. Askew, in 1274, May 30, asks for a proof of a method for ascertaining the divisibility of a numbei" by 7, which he states to have been discovered by Mr. Rickard, of Birmingham. Probably many have discovered it : my father did. for one, and taught it to me some thirty years ago. The test -number is equally xiseful for 7, 11, and 13. The method, as worked liy my father, gives, in the case of a number divisible by all three factors, the other factor as well, without further labour: and in this respect it has an advantage over that of Mr. Bickard. If a number, X, be marked off from the right-hand end in periods of three digits ; and if a, b, c, &c., be the periods ; and if M be the difference between the sums of the alternate periods; we have, writing r for 1000, Ts=a + br + cr' + dr^ + &c. M = a— i)-^c — d + &c. .•.N-M = b {r + l)+c(r'-l) t- <£()■» -i- 1) -H &c. and is divisible by (r-fl)j hence, if M be divisible by (r-H) or anv factor of it, so also is N. And in this case r + 1 = 1001 = 7 x 11 xi3. My father's rule was to set the right-hand period under the next, and subtract, setting the remainder under the next, and so on. In the last period, the subtraction is doicnwards if the lower number be the larger. In this instance, since we have 1 to carry into the last period, the 931 must be read as 932. The ultimate remainder, 024, is the test-nnmber ; and, since this is divisible by 7 and 11, so also is the whole number. If the test-number chanced to be zero, the second line would be the cpiotient produced by dividing the given number by 1001 ; i.e., it is the factor remaining after dividing out 7, 11, and 13. For let us call the second line " V; " writing three ciphers at the end, we get lOOOV ; and we know that, if this be deducted from the upper line, the remainder = V. Hence N = lOOlV = 7 x 11 x 13 x V. In the above example, if the left-hand period were 932 instead of 8, the test-number would be zero. If the periods be single digits, i.e., if 7- = 10, we get a test for divisibility by 11, and at the same time the G4372583 quotient after dividing out 11. The rule is to 05852053 set the last digit under the next, and subtract, setting the remainder under the next, and so on. In this instance the test-number =0; hence the given number = 11x5852053. With periods of two digits, we get a test for divisibility by 101 ; and so for four or more digits. C. L. Dodgsox. Ch. Ch., Oxford. P.S. — The sum of all the periods gives us, for periods of 1, 2, 3, &c., digits, a test for divisibility by 9, 99, 999 ( = 27 x 37), &c., or for any factors of these numbers. This method may also be worked by a rule analogous to that given above ; e.;;., to test for 999, mark off in periods of three, write 000 over the right-hand period, and subtract, writing the remainder over the next, and so on. Hence, also, if the test-number chanced to be zero, the upper line (omitting the 000) would be the quotient produced by dividing the given number by 999. Probably similar rules may be made for most primes. I have myself made fairly simple rules for 17 and for 19; but such pro- cesses are rather ctirions than useful. [1325] — Mr. Askew's rule is applicable not only, as he says, to the division 7 and 13, but also to 91. The reason is that both (1000 -t-l) and (1000--1) happen to be exactly multiples of these three numbers. Any number of over six figures may be expressed in the form a -I- lOOOt. -f lOOOV -H lOOO^a -f [A] where the letters a, b, &c., stand for the numbers expressed by the successive triplets of figures, beginning at the right hand. Now the quantitv (10UO-fl)!--t-(IO0O'-l)c-h(1000=-i-l)d-(- [B] must be a multiple of 7, 13, and 91. If therefore the quantity [A] be divisible by one of these numbers, so also will the difference between [A] and [B] — viz, a — b + c-d+ Henry Bradley. [A number which is divisible by two prime numbers must neces- sarily be divisible by their product. — K.P.j. (Answer to Letter 1274, page 399.) [1326] — " Point off the given number into periods of three figures. Add separately alternate periods, and find the difference of the sums thus obtained. If this difference is divisible by seven, the original number is so, and if not, not." The reason is as follows : — Adding the figures alternately, and taking the difference, gives the criterion of divisibility by eleven, since the successive powers of ten (1, 10, 100, 1,000, &c.) divided by eleven give remainders 1, 10, 1, 10, &c. ; similarly, adding them alternatelv in sets of two gives the criterion of divisibility by 101, since 1, I'OO, 10,000, 1,000,000, &c., divided by 101, give as re- mainders 1, 100, 1, 100, &c., and adding alternately in sets of three gives the criterion of divisibility by 1001, since 1, Iff", lO", 10', ic, give the remainders 1, 10', 1, 10', &c., when divided by 1001, and since 1001 is divisible by 7 and 13, the same method gives a criterion of divisibility for each of those numbers. This is only a special case of the law of divisibility in any scale of notation— viz., that adding the figures gives the criterion of divisibility by one les.-i than the radix of the scale, adding them alternately and finding the difference gives the criterion for one more than the radix. The radix in this case is 1,000. The number taken by Mr. Askew is 220,97-1,901. 220,000,000 = a multiple of 1,001 + 220 974,000 = „ ,, - 974 901 = „ „ + 901 .•. 220,974,901 = „ ,, + 147 and since 1,001 is divisible by 7 and 147 is divisible by 7, a multiple of 1,001 -rl47 is divible by 7. Also since 1,001 is divisible by 13 and 147 divided by 13 leaves remainder 4, a multiple of 1,001 + 147 must leave remainder 4. H. A. Nesbitt. PKOPEP>TY OF NUMBERS. [1327]— The problem proposed in article No. 1295 of your issue ©f 6th inst. presents no great difiiculty. The actual working- out, which is rather lengthy, I forward separately. The result may be given as follows : — Let a, b, c, and d be the remainders when a number N is divided by 3, 5, 7, and 11 respectively. Then N = lloSr -h 3S5a -H 231t) -f 330"c - 210d. The value of r must be taken to suit the conditions of the pro- blem, viz., N is to be a number of three digits. If this problem is to be given as a mode of figure-conjuring, the conjurer will find the figures involved rather long for mental calcu- lation. It would be better in that case to limit the problem thus :— - Tell a person to take any number not exceeding 100 (to say 105 might give a clue to the puzzle), to mentally divide the number by 3, bv 5, and by 7, and to announce the remainders. The would-be conjurer should then be able to announce the number thought of in a few seconds. The kev to the conjuring is as follows — S = i05r + 70a + 2lb-rloc r being taken as zero or a negative quantity to suit conditions of problem. A- H- B. E. P.S. — If another divisor, 13, be introduced and e be the remainder, then it can similarly be found that N = 15015)- f 5005a -i- 0006b + 10725c + \3God + -6930?. PROBLEM IX XDMBERS. [1328]— The following problem was given by a Moor at Gibraltar to a friend of mine ; — Divide any number by 3, 5, and 7 ; the remainders are a, b, and c, and the number of 100 "is d. With these data what is the number ? 16 ♦ KNOWLEDGE ♦ [July 4, 1884. Ansioer. — 70n +211 -4- 15c±7t x 105, n being each a nnmber as -will bring the result into the given number of 100. E.g. 421. Eemainders. 3)421 140 + 1x70= 70 5)421 84 + 1x21= 21 7)421 60 + 1x15= 15 106 + 105x3 = 315 421 It may interest your readers to discover the rule and prove it. How the Moor discovered it may be an interesting snbjeot to specu- late on. G. H. BoLLANn. A SHEETED GHOST. [1329] — I once saw a ghost — that is to say, as much of a ghost as I believe anyone ever saw (notwithstanding all one may read and hear) excepting, of course, nervous illusions. About the "year 1861, when I was eighteen, and serving my articles, I was in bed with the window-blind up, and the moon shining into the room and on to my bed. I half awoke and, to my surprise, saw standing on me and reaching beyond the ceiling, a tall figure, like that of a man or woman draped in white. I continued to look at the figure, and then not feeling comfortable, resolved to ascertain what it all meant. At this time I was still only half awake, as only a few seconds had elapsed. I raised myself, and lo ! my ghost vanished. But not quite ; for in a moment the optical illusion was apparent to me. Just in front of and close to my eyes had been a pointed fold of the upper sheet of the bedclothes, and upon this the moon shone. In my half-awake condition the effect was perfect, and apparently the figure stood there in all its height ; but when I moved I became more awake, and saw the ghost disappear into the pointed fold of the sheet. j. b. Williams. TRUE AND FALSE PERSPECTIVE. [1330]— Neither " Ros. Vansittart " [1276] nor " An Old Draughtsman " [1288] appears to me to have touched the diffi- culty felt by " R. Jones " [1244], which is one that I (as a teacher of drawing) have found very puzzling to learners, especially to those who Hke to know exactly the "why and wherefore" of the rules they are taught. The fact is that the usual method, illustrated ''7.".''^° *-"'' ^''^""•itsman," is a compromise between the impos- sibility of drawing a picture with a movable centre of vision and impractibility of drawing one on the inner surface of a sphere. The point of view for each picture must be rigidly fixed, and this necessitates the limiting of the field of view to a circle forming the base of a cone^ whose sides meet at the eye at an angle of not more than about 45° (some artists say not more than 30°). As soon as the eye is dii-ected towards any other point than the centre of the base of this cone, the point to which it is directed becomes at once the centre of the base of a new cone, and a new picture must be drawn upon that point as centre. This is the difficulty experienced by ' R. Jones," and over which so many students stumble. As long as the face of a cube is square to the direction of the observer's eye, it must be drawn square, although it may be on one side of the line of direction, for, as soon as he looks directly at it, he changes the position of the centre of vision, which then falls upon the cube itself, and the line of direction is no longer square to the same face of the cube. The only exact way of representing objects as they actually appear to the eye is by drawing them on the inner surface of a hollow sphere to be viewed with the eye at the centre. This, of course, is impracticable, and indeed is unnecessary, as the same effect is got in the usual way if the visual angle is not made too large. Each picture may be then considered as a circular segment of a sphere of which the line of direction is a radius, and if the seguieut be taken small enough it will be so nearly a plane as to be represented on a flat surface without undue distortion, and when viewed at the centre will give the exact effect of the real object. Wm. Field. LETTERS RECEIVED AND SHORT ANSWERS. John A. R. Newlands. Tou will find a sliort review of yonr book on page 370 of our fifth volume. — H. A. Nesbitt. Letters by the Rev. C. L. Dodgson and another correspondent were marked for insertion a fortnight ago. — Ignoeaxt. Your question is more diflicult to answer than it looks. I know of good books whence you may learn the various wild flowers, and cheap books having the same end ; but none rigidly answering both descriptions. " Familiar Wild Flowers," published by Cassell & Co., and Ann Pratt's " Wild Flowers," published by the Society for Promoting Christian Knowledge come under the former category. Of the lower-priced works Bettany's " First Lessons in Practical Botany," published by MacMillan for a shilling, is as good as any. — Geoege Hill wants to know how many feet of air can be compressed into an iron vessel one foot square ? Obviously this must depend npon the strength of the vessel ; 250 ft. it it is strong enough. Perhaps some aeronautical reader will answer your question. How long it takes to fill an ordinary balloon. — Feedekick Elgak. My personal experience with reference te strawberries differs widely from yonrs. I have eaten unnumbered gallons of there without developing either rheumatism or gout; albeit both my father and grandfather suffered from the last-named complaint. Should this meet the eye of Mr. Mattieu Williams he may, perhaps, give yon the benefit of his opinion. — JoHx Cha.nxon. While persistently declining to advertise trade articles in the Health Exhibition now open at South Kensington, I willingly call attention to your exhibit of a Brick Finial in Class 50, representative as it is of the style and quality of instruction imparted at the Technical College, Finsbury, where all the real work of the City and Guilds of London Institute will be done in the future, as it has been in the past. — The Yxiscedwyx Company send me a pamphlet to prove that London might be rendered practically smokeless by the use of anthracite, as is the case in New York. — John E. Svms defends the usual method of drawing a cube against "R. Jones " and " C. E. Bell " (letters 1,244 and 1,307). Perhaps I may suggest that each of the disputants should place a cube behind, and with one face parallel to, a sheet of plate-glass, and, keeping the eye rigidly fixed (say by applying it to a pin-hole in a fixed card) trace the outline he sees accurately on the glass, and communicate the result in as short a form as possible. It will be time enough to theorise when we are agreed as to our facts. — A. L. M. sends an account of an odd co- incidence. He is resident in the house of an old gentleman who is a keen flower-gardener. On the 19th nit., my correspondent was watching his landlord smarten up his beds, and after a little badinage, threatened to get up in the night and ride a donkey over them ! As a matter of fact, a donkej- did wander from its house that very night, get into the garden, and make an utter wreck of it ; and on seeing its hoof-marks the next morning, the unfortunate proprietor of the ruined flowers could at first scarcely be convinced that his lodger had not carried his curiously improbable jocular threat into execution. "Now," says my correspondent, "I ask, suppose that I had threatened to kill him instead, and he had been found dead in the morning, could I have escaped hanging?" — A. P. SiN.VETT. Premising that reviews in this journal are not written by its editor unless specially signed by him, but are penned by contributors supposed to possess special knowledge of the subjects of the books to which they relate, I regret that the writer of the notice to which you take exception should have employed a phrase in the slightest degree calculated to hurt yonr feelings ; but having myself read your book when it first appeared, I can only conceive that he said — with perhaps rather needless brusqne- ness — what every impartial reader of it m.ust have thought. Yonr cutting from Lijht is not worth the paper it is printed on, inas- much as the citation of many of the names it contains as those of Spiritu.alists is dislione-'t. Thackeray, for example, repudiated, both editorially and in his private capacity, the slightest belief in the cock-and-bull stories told by Robert Bell in Vol. II. of the Cornhill Magazine (vide Vol. VII. of that magazine, p. 706). Lord Brougham, again, publicly denied any belief in Spiritualism, and so on. Professor Hare was insane, and died, I believe, in an asylum. Nay, will you write to the very first man whose name heads your list, the Earl of Crawford and Balcarres, asking him whether he does or does not believe that so-called " Spiritual " phenomena are supernatural — and publish his reply ? Mr. Crookes's "Phenomena of t^piritualisra " lies on the table before me as 1 write. Finding, as I do, in it its author's testimony to the probity and the reality of the phenomena exhibited by Miss Florrie Cook (whom he took such elaborate pains not to find out), and knowing how this same Miss Cook's imposture was at once detected on Jan. 9, 1880, by Sir George Sitwell and Herr von Buch, what possible value can 1 attach to anything that Jlr. Crookes may testify or say on the subject of spiritualism? It is idle to t!k!k of "the frauds July 4, 1884.] ♦ KNOWLEDGE ♦ 17 sometimes perpetrated " by media. Can you give the name of one single ivell-known medium who has not been ultimately detected ? I refuse to suffer the precious space in these columns to bo wasted in connection with an imposture which can only be legitimately met by proceeding against media under 5th Geo. IV., c. 83, s. 4, and b}- placing their dupes in safe confinement. — Miss F. H. Wood. I have received your historical chart, and your description of your new adjustable geometrical ruler with which it was executed. The latter seems an ingenious instrument, but as I have not the smallest idea when I shall bo in town, I regret my inability to make an appointment to inspect it. — iliss Maegaret B. Aldeb opines that if " the abysmal depths of the oceans were laid bare .... the red clay, mth its incipient zeolites, feldspars, and iron oxides, and superfluous silica, would harden into basalt, granite, whinstone, trachyte, and other rocks said to be produced by former volcanic action" — in which I regret to differ from her. — Cbas. I know nothing about the books read for the London degree. The Hamil- touian system of interlinear translation will enable you to construe, but you will infallibly be tripped np in your examination if you do not study the grammatical structure of the sentences as well. — Geokge Chapman. Out satisfaction is mutual. — A. N. Professor Hughes was the real inventor of the microphone. I cannot spare the column which a descrip- tion of its construction would occupy. So far as I know it has not been used by any maker of car trumpets. — J. JIckrat. Send your communication to some other journal, with the offer of a handsome reward to any one who can make head or tail of it, — W. CosMox. Tour " puzzle " is as old as the hills. Everything depends upon the direction in whicli you sail round the world. A ship going from west to east gains a day, on going from east to west loses one, so that if they started simultaneously on their respective voyages, and met again at their conclusion, it might be Tuesday on board of one ship and Thursday on the other. The difficulty is insuper- able. There is no such a thing as a hora mundi. — C. E. Mabeiott sends a letter to the Editor (for Mr. Pillinger) stating that he encloses fifteen stamps — which he does not — for a timepiece ! My dear young friend, you must find out where Mr. P. lives, and write straight to him yourself. I am not his agent, and don't keep his timepieces here. — The Xatioxal He.\lth Society sends me an excellent little tract on vaccination, which can hardly be too widely circtdated. — Sir Daniel Coopee and E. Howell. Thanks for cards of invitations, which overwhelming pre-occupation only has prevented me from accepting. — X. Hopken, Ax Old Dracghtsmax, Rosalie Vaxsittart, and Ajithue A. West. See reply to " John E. Syms," above. — W. W. S. It is utterly beyond the province of Knowledge to recommend individual tradesmen, but of the names yon give the third is undoubtedly that of the most scientific artist. — A Scbsceibeb asks for the composition of some transparent medium for the crysto- lenm process, which will not spot. Can any of our photographic readers oblige him ? — R. RrssELL. Neither the names nor addresses of correspondents can be given without their special permission. — Gaxga Ram. Tour pamphlet, when received, will be read by an expert in the matter to which it relates. — Erxest (sic) Enquikee. As your facts are wrong, and your conclusions from them erroneous, I feel that I shall best comply with your request to " deal gently with " you by simply acknowledging the receipt of your letter. — W. Cave TH0^us. Tour original letter was already in type when the one you wished to be substituted for it arrived. — M. E. SlMp- sox. Tour communication shall be forwarded to the proper quarter. — J. The subject is being treated of from a scientific point of view, and from that alone ; but science is dumb in the presence of such considerations as those which you advance. — T. Commox. It seems probable, as you say, that Mr. A. McD. has misunderstood the passage you quote. I entirely agree with you that " Mr. Garbetc would probably get as much information with regsird to the flood from the ' Homo diluvii testis ' among the Salamanders in the British Museum as from Mount Ararat and Xoah's rainbow." — Watsox & Soxs. Received. The eighteen principal English railways have earned almost exactly a million a week for the twenty-fonr weeks of the present year. A Ship Struck by Lightxixg. — A despatch from Derry, dated 22nd ult., says: — "Captain M'Cann, master of the Derry barque Village Bell, arrived in port this evening from Baltimore. He reports having eight sailors on board belonging to the Spanish ship Angeleta, from New Orleans to Barcelona, which was struck by lightning and set on fire." The message states that the whole of the crew were rescued, and makes no mention of any casualty amongst them. The ship appears to have been burnt to the water's edge. 0m- ^3cira330)r Column. THE foolish fellow who mischievously threatened a universal storm some time since, publishes the following curious illustra- tion of paradoxical absurdity. We give it, heading and all, as it appeared in the Kew York Tribune : — WIGGINS'S DARK MOON. IS THE EARTH ACCOMPANIED BT TWO SATELLITES ? THE CAXADIAX WEATHEE-SEEE SAYS IT I.S AXD TELLS THE REASON' WHY. To the Editor of the Tribune. SiE, — For many years it has been my belief that our planet is accompanied by two satellites, a visible and a dark one, the dis- tance of the latter from the earth being probably double that of the former. The librations of the moon, the irregularity of her motions in her orbit, and the fact that her perigee seldom takes place immediately on the orbit of our earth in advance of the earth's course, are strong evidence of the disturbing influence of a sister satellite. The variation in the time and height of the tides, occasional tides of excessive height without apparent cause, and the frequent occm-rence of double tides, cannot be explained on the hypothesis that the earth is attended by only one secondary. Earthquakes which are cansed by unusual plane- tary attraction frequently occur when it would appear that the force which produced them had not yet reached its climax, and could not till after the moon's conjunction with the sun. The recent earthquake in England occurred two days before the moon was in conjunction with the solar orb, and before she was in perigee, showing that her attractive power must have joined with anotlier and very nearly equal force before she reached the line of her solar conjunction. This earthquake I predicted would return with increased violence on May 20. It did so, causing the destruc- tion of many villages and the death of hundreds of people. On the same day occurred the disastrous cyclone in British Burmah. The earthquake, however, did not appear in England, and I am convinced it was moved eastward by the infiuence of this dark planet. The recent cold wave which passed over America must have been due to this source, and as nearly the same conditions will exist on the 26th and 27th of the present month, the same cold wave would appear were it not for the changed position of this dark horse of the heavens. All great storms should occur after certain planetary conjunc- tions, whereas they frequently precede them, and it is for this reason that many meteorologists — among them Sir William Thomp- son (sic) — have denied that the moon has any influence whatever in producing storms on the surface of our globe. Tears before I published predictions I found that some of my storms would be delayed for several days, others would appear ahead of time, and frequently the heaviest would be annihilated altogether. There were no known planets which could possibly produce this effect, and I was at length forced to the conclusion, as I have said, that otir earth is accompanied by a dark satellite. It would further appear that the " dark days " of which frequent mention is made in history — so called because they could not be traced to an ordi- nary solar eclipse — were of such a character as to justify the belief that they were caused by an opaque body intervening between our globe and the sun, for the suddenness and brevity of the darkness could not be interpreted as due to smoke or vapour in the earth's atmosphere. I am confident that the moon and this dark satellite were in con- junction with the sun, or nearly so on March 9, 1883, which pro- duced the eruption of the great Java volcano, and caused the storm which I predicted would be — and the London Times says it was the greatest storm of the present century. On March 26, 1884, this planet was somewhere in the neighbourhood of her inferior or superior conjunction, and heightened the storm of the 28th of that month. Strange to add, I have jnst received letters from Michigan saying that a solar eclipse was visible in that State on May 16, 1884, at 7 o'clock in the evening, when fnUy one-third of the solar disc was in darkness. As the moon at that moment was twelve degrees south of the celestial equator, and the sun was as many degrees north of it, this phenomenon cotild not have been cansed by our visible satellite. Doubtless it was the passing of this dark planet across the sun's disc. I have little sympathy with Professor Proctor and others, who, with the prejudice of the old schoolmen, persist in declaring that our moon is a dead planet, and is not possessed of an atmosphere. Any one who wUl take the trouble to look when she is in quadra- ture, will see with the naked eye on a clear night the whole luminous 18 • KNOWLEDGE ♦ [Jdly 4, 1884. annnlus or ring of light that surrounds her orb, which is proof positive and complete that she is enveloped in an atmosphere similar to our own. The same arguments were used long ago by Dr. Dick and others to prove that Jupiter and other primaries are destitute of an atmosphere, while the very fact that they are visible, is evidence that they are endowed with atmospheres like that of our own globe, for surely no one is now antiquated enough to believe that light exists throughout space but only in the atmo- sphere of the planets. The non-existence of a second satellite to the earth is therefore not proved by reason of its invisibility. Its position can only be ascertained by noticing the sudden quenching of stars, and I trust that astronomers both in America and Europe will aid in obtaining the magnitude and motions of this lonely wanderer in the sideral heavens. E. Stone Wiggins. Ottawa, June 3, 18S4. To all which nonsense the Neiv Tori Tribune is at the pains somewhat gravely to reply. The closing words of the leader de- voted to this precious rubbish are neat however : — " Unfortu- nately," says the Tribune, "there is one view of Mr. Wiggins's discovery which he lias failed to take, to wit, the view that it may not be at all necessary. For between accepting a dark moon (save as an exercise of pure faith) and believing that the meteorological theories of Mr. Wiggins are nonsensical, the great majority of man- kind will, we fear, be very apt to find the second conclnsion the easier and simpler of the two." There is a series of illustrated notes on the Pons-Brooks Comet of 1883, by H. C. Wilson, in the Sidereal ilefseitrfer for June, which students of cometary physics will read with interest. Manganese in Animals and Plants. — Becent researches by M. Maumene have, says Engineering, shown that the metal manganese exists in wheat, rice, and a great variety of vegetables. Wheat contains from .jjj'^^ to tsj^^jj of its weight of the metal, which exists chiefly as a salt of an organic acid. It is also found in potatoes, beetroot, carrots, beans, peas, asparagus, apples, grapes, and so on. The leaves of the young vine are very rich in it ; so are the stones of apricots. The proportion in cacao is very great, as it is in coffee, tobacco, and especially in tea. In the 50 grammes of ashes left bj' a kilogramme of tea, there was found 5 grammes of metallic manganese. There are vegetables, how- ever, in which no manganese can be found, as, for example, oranges, lemons, onions, tfcc. Many medicinal plants contain it, as for example, cinchona, white mustard, and the lichen (Roccella tinctoria). Animal blood does not always contain it, but it is found in milk, bones, and even hair. M. Maumene regards its presence in the human body as an accident, and not of vital im- portance. He also suggests that doctors should cease to employ manganese as a succedaneum with iron, for while the latter is useful to the blood, the former is an intruder which is only tolerated in small traces, and rejected in larger quantities. Tea, coffee, and other vegetables require abundance of manganese in the soil for their proper cultivation, and the absence of it may account for the failure of many plantations. In connection with the series of lectures now and for some time past in course of delivery by some of our best -known scientific men, at the Royal Victoria Coffee Hall, a lecture was given on Tuesday week by Mr. Arthur Nicols, F.G.S., F.R.G.S., on " The Dog as the Friend of Man," illustrated by numerous large coloured pictures of the heads of the principal breeds, prepared specially from draw- ings by distinguished artists. The lecturer treated his subject from the point of view of the lover of dogs, rather than of the dog- fancier. He first gave a sketch of the origin of domestic dogs, which all competent naturalists are now agreed in considering as having been derived from some three or four wild species ; and pro- ceeded to consider in detail the senses — sight, hearing, and smell — by instances mainly derived from his own experiences at home and abroad, giving many illustrative examples and anecdotes of the utility of dogs. In more than one instance the lecturer showed how his life had been saved by the viligance of these faithful animals. He next described the characteristics of the principal breeds, com- mented on dog-shows, canine madness, &c., and gave instances in evidence of the intellect and moral character of dogs, concluding with remarks on the influence which association with the dog has exerted on man himself. The lecture was listened to throughout with great attention by a very considerable proportion of the audience, the conduct of the occupants of the gallery, however, leaving much to be desired. A hand-bill was previously distributed in the hall of notes, drawn up by Mr. Nicols, on " Mad Dogs : How to Know Them, and What to Do," with the object of diffusing useful information on this important subject. 0av iHatl)tmattraI Column. EAST LESSONS IN CO-ORDINATE GEOMETRY. By Richard A. Peoctoe. (Continued from p. 467.) PoLAB Co-OEDINATES. 45. Pbof. — To find the polar equation to a straight line in terms of the angle at tchich it is inclined to the initial line, and the intercept on the initial line. Let A B be a line meeting the initial line OX in A. LetOA = a, and /BAX = a. Take P any point on A B, and let the co-ordinates of P be r, 9. Join 0 P, then sin OAP 0 P = OA sin OP A ,, . . sin a that IS r = a ^ sin (a-e) the required equation, which may be written in the form r sin (9 — a) -l-a sin a = 0 (1.) We might have obtained (1) from the equation to A B in rectangtilar co-ordinates (O X the axis of X). For draw O K perpendicular to 0 X to meet A B in K, then O K = a tan a. Thus the equation to B K is — —r^- =1 a a tan a that is, since x = r cos 6, and y = r sin 0 T cos 0 r sin 0 cos a r sin (9- -1 = 0 a am a -a) + a sin a = 0 (1) the or as before. We can obtain the polar equation iu a more convenient form by determining the line in a different manner. 47. Pbop. — To find the polar equation to a line in terms of theper- pend icular on the line, and the an/jle at which this perpendicular is inclined to the initial line. Let A B be a straight line. Draw 0 Q perpendi- cular to A P, and suppose OQ=p and ZQ0A = a; let r. 9 be the co-ordinates of any point P in A B ; then 0PcosP0Q = OQ that is r cos (9 — a) =p the required equation. 47. If in (1) a = 0, equation becomes rsin (0-a)=O ie., sin (6 — a) = 0 Hence S = a or else 9 — a = Tr; that is 9 = a or a + jr; and it is obvious that either form expresses the same line. Hence the equation to a line through the pole inclined at an angle a to the initial line is 0 = a. 4S. And, vice i-ersS, an equation of the form 6=a constant, repre- sents a straight line through the pole ; for it is clear that such a line is the only curve for every point of which 9 is constant. 49. The polar equation of the straight line is of the form Ar cos0 + Br sin0-i-C=O (1) and we might easily prove, conversely, by an independent process that an equation of this form always represents a straight line. This is not necessary, however, since transforming to rectangular co-ordinates making the pole the origin and the initial line the axis- of X, (1) becomes AI-^Bl.;-^C=0 an equation which, as we have already seen, represents a straight line whose intercept on the axis of ^r (that is, on the initial line of C our polar equation) is — 5, and which is inclined to the same axis or B initial line at an angle whose tangent is — t- July 4, 1884.] ♦ KNOWi^EDGE ♦ 19 50. Tho following examples illustrate the method of drawing the lines represented by given polar equations. ^ Take first the equation 2rcos e + 3r sin 0-6 = 0 Put 6 = 0, giving 2r - 6 = 0 That is r = 3 (i) Again put 9=^,giving3r-G = 0 That is r=2 Thus the given equation represents the line AB in the figure, in which O A = 3, and 0 B = 2, 0 B being drawn at right angles to the initial line 0 X. 51. The following method is often more conveniently applicable. In (i) put as before 6 = 0, giving r = 3; that is, determining tho point A in which the given line cuts the initial line. Xow since -G r = 2 cos y + 3 sin 6 it is clear that if such a value be given to 6 that 2 cose + 3 sin 6=0. In other words, if we take 2 tan 6= —5 r becomes infinitely great. Hence if O C be drawn from 0 inclined 2 to 0 X at an angle whose trigonometrical tangent =_-, then O C must be parallel to the line represented by (i). Thus we must take 0 A = 3 and then draw through A the line DAB parallel to OC. Take as another illustration the equation 5r cos 9 — 2r siu 6-10 = 0 Here 6 = 0 gives r = 2, and to make r infinite we must take 5 cos 6-2 sin 0 = 0 „ 5 that is, tan 6 = ^ Thus if we take 0A = 2 and draw A B inclined to O X at an angle B A X whose tangent ,8 is-, AB 2 / / is the line repre- .sented by the given equation. (To be continued.) EASY KIDEES ON EUCLID'S FIRST BOOK. With Suggestions. Pkop. 33. 142. Two straight Hues A B and A C are drawn from a point A ; and two other straight lines D E and D F from a point D. A B is equal and parallel to DE, and AC is equal and parallel to D F. Show that B E is equal and parallel to C F. 143. If a quadrilateral have two of its sides parallel, and the other two equal but not parallel, any two of its opposite angles are equal to two right angles. 144. Two equal but not parallel lines make equal angles on the same side of a thii-d line which joins their extremities. Show that the straight line which joins their other extremities shall make equal angles with the two first lines and be parallel to the third. 145. In the figure to Euc. I. 5, G L drawn perpendicular as to B C produced, is produced to M so that L JI is equal to L G. Show that B L is equal and parallel to F C. Prop. 34. 14G. The diagonals of a parallelogram bisect each other. 147. If two straight lines bisect each other, the straight lines joining their extremities form a parallelogram. 148. No two straight lines dravm from the extremity of the base of a triangle to the opposite sides can possibly bisect each other. (To ie continued.) 4Buv mxin^t Column. By Five of Clubs. The Hands. , f H. K, 7. iC. A, 7. • H. Kn, 10, 0, G. P. A. Q |i, K, :i. 4, 3, 2. \ .> C. K. 1 D. A, Q, (.S. 8, 7, C Kn, 9, . J.-B.'< B Y r-z,3. Tr. 7/4 z 4, 5, A. 3, 8, 9. 2, G, 8, 10. 5, Kn, K. H. C. D. S. f II. Q, 8. {C. Q, Kn, 10, G, 5, 4, 2. S. 10, 9. ■^ D. 7, 4. i B '.^21 Z + * w V 7 <9 ^% vin by Kt B X Kt B X B P X P P X P B to Kt 2. Here White missed the right reply, and thus failed to reap the benefit of his brilliant play. White played P x B, to which Black replied with Kt to Kt4, and ultimately won the game. We think, however, that the issue would have been different had Black followed the obvious Mne of play and taken the two pieces ; in which case the following might have occurred : — P X Kt (ch) K X P P X B Mr. Blackburn. Black. Wkiti. Mr. Hirsch. Now we really do not see a satisfactory continuation for Black. Our informant, Mr. Frankenstein, is of opinion that White ought to win. We give a few possible variations, leaving to onr readers to determine whether Black had any valid defence. If, for example : — K takes P R to Kt sq (ch) KtoB3 R to R6 (ch) K to K2 R to B7 (ch) K to B sq B to Kt and wins (a). K toB sq R to R8 (ch) K to K2 R toR7 (ch) K to B sq (I) R to Kt sq B toR5 (ch) K takes P K to K2 ! R to Kt sq (ch)R to Kt sq K moves RtoB2 (ch) KtoK2 K toB7 (ch) and wins. K toQ2 B to B7 Q to Kt3 (c) R to B2 (d) (a) Black has no satisfactory move, as White threatens B to K6, if Black now plays K to Ksq, then B to R5, RtoK2. R to R8 (ch) and wins, or, if instead of R to Ksq, Black plays R to B2, White ought to win by winning the Queen by R to R8 (ch), and remaining with two minor pieces against a Rook. This, we think, is the best result that Black may hope to attain. (b) And the position is the same as before. If, instead of K to Bsq, Black now plays K to B3, then B to R5 wins. (c) Instead of this. Black may play R takes P. R takes K, K to B2. B to K6(ch), K to Kt3. R to R7, Q to Qsq. Kt to Q2, Q to B3. B to 84, and White must win by bringing his Kt well into play. The black Rook dare not move, and if either P advances, White pushes on. (rf) Again, it is difficult to see what to do for Black, as White threatens either B takes R, followed by E to B8 or B to K6, fol- lowed by R to B7. If now Q to Qsq, B to K6(ch), K to B2. R to B7(ch), K to Kt3. R to Q7, Q to B3. Kt to Q2 (threatening E to Bsq, followed by R takes P(ch) Ac), Q to R3, R takes P(ch), K to Kt2. R to Q7(ch), followed by B to B5, and White ought to win. We do not presume to have exhausted Black's chances of defence, at almost every move a variation of play may occur ; the above analysis is only intended to serve as a general indication of what might be attempted in this remarkable position. SOLUTION OP PROBLEM, p. 407. 1. R to Kt3, and mates accordingly. ANSWERS TO CORRESPONDENTS. Correct solutions received of A. W. Overton — George Gonge — Q. T. V. Senex wishes to find an opponent for correspondence games. E. Eidgeway. — If 1. B to K6, Kt takes P, and there is no mate. This problem has deceived a good many solvers. Contents op No. 139. PXGB Dreams. III. By Edward Clodd. 469 Notes on Flying and Flying Ma- chines. By R. A. Proctor 470 Pleasant Hours with the Micro- scope. (Illm.) By H. J. Slack. 472 Electric Projectors on Yachts 473 The Entomology of a Pond. {lihis.) By E, A. Butler 474 Sea-Clouds. By Eichard Jefferies.. 475 The International Health Exhibi- tion. V. (nius.) 476 Dieiens's Story Left Half Told. By Thomas Foster 478 Zodiacal Maps for the Month. By K. A. Proctor 4S) Optical Recreations. {Illat.) By F.R.A.S 480 Eeviews ; The Sagacity and Morality of Planets — Some Books on Oor Table 483 Correspondence : The Noachim Deluge — Coincidences — The Divided Skirt— Brain Weights.&c. 483 Our Mathematical Colnsm 4£d Our Whist Column 489 Our Chess Column 490 SPECIAL NOTICE. Part XSXII. (June, 1884), now ready, price Is., post-free. Is. 3d. Volume V.» compriaing the numbers published from January to Jane, 1884, will soon be ready, price 98., including parcels postage, Os. 6d. Binding Cases for all the Volumes published are to be had, price 28, each ; including parcel postage, 2s. 3d, Subscribers' numbers bound (inelnding title, index, and case) for 3s. each Volume ; including return journey per parcels post, 3s. 6d. Eemittances should in every case accompany parcels for binding. TERMS OF SUBSCRIPTION. The terms of Aimual Subscription to the weekly numbers of Ej^owlsdce are as follows: — S. d. To any address in the United Kinsdom 15 2 To the Continent, Australia. Xew Zealand, South Africa, & Cansda 17 4 To the United States of America 54.25 or 17 4 To the East Indies. China, &c (n'J Brindisi) 19 6 All subscriptions are payable in advance. OFFICE : 7-i-76, GREAT QUEEN STREET, LOXDOX, W.C. July 11, 1884.] KNOWLEDGE ♦ MAGAZINE OF SCIENCE Plainu Worded -exactlyDescribed LUJXDVS : iKlU.iY, JULY 11, 1S84. Contents op No. 141. PAOB Other Worlds than Ours. By M. de Fontenelle. With Notes by Richard A. Proctor 21 Dreams. IV. By Edward Clodd . 23 TheEntomology of aPond. (2Hii».) By E. A. Butler 24 A Novel Fire Escape, llltut.) 25 Notes on Flying aud Flying Ma- chines. By R. A. Proctor 25 The Tricycles of To-day. The "CheylesmoreClub." (Jlliu.) ... 2S The Electro-Magnet. By W. Slingo. (/Hi<».) 29 TAG! The Antarctic Regions. Bj R. A. Proctor '-^0 j Optical Recreations. (JU«.«.) By F.R.A.S 32 The International Health Exhibi- tion. VII. (/««,..) :« Reviews : Some Books on Our Table :W Miscellanea 37 ! Correspondence : Savage Names — ! Colours of Clouds— Acarina and OribatidiC, ic 3S Our Mathematical Coliunn -10 i Otir Chess Column 41 OTHER, WORLDS THAN OURS. A WEEK'S CONVERSATION ON THE PLURALITY OP WORLDS. By Mons. de Fontenelle. WITH notes by RICHARD A. PROCTOR. [I have received many inquiries in regard to the earliest history of the study of life in other worlds, and am sur- prised to find how little is known of the work of Huyjihens, Fontenelle, and others, in that direction. It has occurred to me, in particular, that the bright and graceful little treatise of Fontenelle, published early in the eighteenth century, (written as it was at a time when the Vortices of Descartes were in full vogue in his own countr}-, though beginning to be discredited in the country of the great Newton) would be interesting and new to thousands of our readers. I propose, therefore, to give an English version of the little book here, with such notes of my own as may seem necessary and desirable. The quaint old illustrations are given ; those illustrating the vortices are iudeed neces- sary to give an idea of the old notions resj^ecting these celestial whirlpools. — Eichard A. Proctor.] FONTENELLE'S PREFACE. IA?*I pretty much in the same case with Cicero, when he undertook to wu-ite of philosophical matters in the Latin tongue, there being, then, no books upon that subject but what were in Greek. He was told that such an attempt would be useless, because those who were lovei-s of philosophy would rather take the pains to search for it in Greek writers than make use of Latin ones, which treated of it, but at second hand ; and that those who had no relish for this science would never trouble their heads with either Greek er Latin. To these objectors, he answered, it would happen quite otherwise ; for, says he, the great ease people will find in reading Latin books will tempt those to be philosophers who are none, and they who already are philosophers by reading Greek books will be very glad to see how the subject is handled in Latin. Cicero might with good reason answer as he did, because the excellency of his genius and the great reputation he had acquired warranted the success of all he wrote ; but in a design not much unlike his I am far from having tlioE<> grounds of confidence which lie had. My purpose is to discourse of pliilosophy, but not directly in a philosophical manner, and to raise it to tuch a pitch that it shall net be too dry and insipid a subject to jilease gentlemen, nor too mean and trifling to entertain scholars. Should I bi- told (as Cicero was) that such a discour.-e as this would not jilease the learned, because it cannot teach them anything ; nor the illiterate, because they will have no mind to learn ; I will not answer as he did. It may be endeavouring to please everybody ; 1 have pleased nobody. Now, to keep a medium betwixt two extteams is so very difficult that I believe I shall never desire to put myself a second time to the like trouble. If I should acquaint those who are to read this book, and have any knowledge of natural philosophy, that I do not pretend to instruct, but only to divert ibem ; by pre- senting to their view, in a gay and pleasing dress, what they have already seen in a more grave and solid habit. Not but they to whom the subject is new may be botli diverted and instructed. The tirst will act contrary to my intention if they look for profit, and the la-st if they seek for nothing but jileasure. I have chosen that part of philosophy which is most likely to excite curiosity ; for I think nothing concerns us more than to enquire bow this world which we inhabit is made ; and whether there be any other worlds like it which are aUo inhabited as this is. But, after all, it is at every- body's discretion how far they will run their disquisitions. Those who have any thoughts to lose may throw them away upon such subjects as these, but I suppose such as can employ their time better will not be at so vain and fruitless an expense. In these discourses I have introduced a lady, to be in- structed in things of which she never heard ; and I have made use of this fiction to render the book the more ex- ceptable, and to give encouragement to gentlewomen by the example of one of their own sex, who, without any super- n.itural part^ or tincture of learning, understands what is said to her ; and, without any confusion, rightly apprehends what vortexes and other worlds are. And why may not there be a woman like this imaginary Marchioness, since her concejitions are no other than such as she could not chuse but have % To penetrate into things either obscure in themselves, or but darklv expressed, requires deep meditation, and an earnest apfilication of the mind ! but here, nothing more is requisite llian to read and imprint an idea of what is read 22 KNOWLEDGE . [JcLT 11, 1884. in the fancy, wliich will certainly be clear enough. I shall desire no more of the fair sex, than that they will peruse this system of jjliilosophy, with the same ap)jlication that they do a romance or novel, when they would retain the plot, or find out all its beauties. It is true, that the ideas of this are less familiar to most ladies than those of ro- mances, but they are not more obscure ; for at most, twice or thrice thinking, will render them very per.'^picuous. I have not composed an airy system, which has no founda- tion at all : I have made use of some true philosophical arguments, and of as many as I thought neoessaiy ; but it falls out very luckily in this .subject, that the physical ideas are in themselves very diverting; and as they convince and satisfy reason, so at the same time they present to the imagination a prospect which looks as if it were made on purpose to please it. When I meet with any fragments which are not of this kind, I put them into some [iretty strange dress : Virgil has done the like in his " Georgicks ; " when his subject is very dry, he adorns it with pleasant digressions : Ovid has done the same in his " Art of Love ; " and though his subject be of itself very pleasing, yet he thought it tedious to talk of nothing but love. My subject has more need of digressions than his, yet I have made use of them very sparingly, and of such only, as the natural liberty of con- versation allows: I have placed them only where I thought my readers would be pleased to meet with them ; the greatest part of them are in the beginning of the book, because the mind cannot at first be so well acquainted with the principal ideas which are presented to it; and, in a word, they are taken from the subject itself, or as near to it as is possible. I have related nothing concerning the inhabitants of the several worlds which may seem fabulous or chimerical ; but have said whatever may be reasonably thought of them ; and the visions which 1 have added have some real foun- dation ; what is true and what is false are mingled together, but so as to be easily distinguished. I will not undertake to justify so fantastical and odd a com])Osition, which is the principal jioiut of the work, and yet for which I can give no very good reason. There remains no more to be said in this place to a sort of people who, perhaps, will not be easily satisfied, though T have good reasons to give them ; but that the best which can be given will not satisfy them. These are the scrupu- lous persons who imagine that the placing inhabitants any- where but upon the earth will prove dangerous to religion. 1 know how excessively tender some are in religious mat- ters, and therefore I am very unwilling to give any oflence, in what 1 publish, to people whose opinion is contrary to that I maintain. But religion can receive no prejudice by my system, which fills an infinity of worlds with inha- bitants, if a little error of the imagination be but rectified. When it is said the moon is inhabited, some presently fancy that there are such men tliere as ourselves ; and priests, without any more ado, think him an Atheist who is of that opinion. None of Adam's posterity, cry they, ever tra- velled so far as the moon ; nor were any colonies ever planted in that region. I grant it. The men in the moon are not the sons of Adam. And here again theology would be puzzled if there should be men anywhere who never descended from him. To say no more, this is the great difliculty to which all others may be reduced ; to clear it by a larger explanation, I must make use of terms which deserve greater respect than to put into a treatise, so far from being serious as this is. But perhaps there is no need of answering the objection, for it concerns nobody but the men in the moon ; and 1 never yet affirmed there are men there. If any ask what the inhabitants are, if they be not men t all I can say is that I never saw them ; and it is not because I have seen them that I speak of them. Let none, however, think that I say there are no men in the moon purposely to avoid the objection made against me, for it appears it is impossible there should Vje any men there, according to the idea I have framed of that infinite diversity and variety, which is to be observed in the works of nature. This idea runs through the whole book, and cannot be contradicted by any jthilosopher. Nay, I believe I shall only hear this objection started by such as shall speak of these discourses without having read them. But is this a point to be depended on t No, on the contrary, I should more probably fear that the oVjjection might be made to me from many passages. FOSTENELLE. DREAMS: THEIR PLACE IN THE GROWTH OF PRIMITIVB BELIEFS Br Edward Clodd. iv. TTIHE artificial divisions which man in his pride of Ijirth X made between the several classes of phenomena in the inorganic world, and also between the inorganic and the organic, are being swept away before the Urger knowledge and insight of our time. Indeed, it would seem that the surest test we can apply to the worth of any kind of know- ledge is whether it adds to or takes from our growing con- ception of unity. If it does the former, we cannot over- throw it ; if it does the latter, then is it science " falsely so called." That notable doctrine known as the correlation of physical forces,' or the convertibility into one another of heat, light, electricity, chemical affinity, ic, each being a mode of manifestation of an unknown energy which " lives through all life, extends through all extent," has its counterpart in the correlation of spiritual forces. Varied as are the modes of expression of these, that variety is on the surface only. Deep down lies the one source that feeds them, the one heart to whose existence their pulsations witness. All primitive philosojihies, all reli- gions •■' that man did ever find," are but as the refractions of the same light dispersed through different media ; are the result of the speculations of the same subject, allow- ances being made for what the astronomers call ]iei'Sonal equation, upon like objects. And, therefore, in treating of the nature and limitations of man's early thought concerning his surroundings, whether these be the broad earth bathed in the sunshine, or swathed in the dark- ness, or the sounds that come from unseen agents, the sight of spectral visitants of whom he cannot have touch, and out of which are built uj* his theories of the invisible world ; the reader may find reference to the same condi- tions which were shown in former papers to give birth and sustenance to primitive myth. The same fantastic con- clusions, drawn from rude analysis and associations, and from seeming connections of cause and effect ; the same bewildering entanglement between things which we know can have nothing in common, meet us ; and the same scien- tific method by which is determined the necessary place of each in the advance of man to truth through illusion is applied. The illustrations of the vital connection which the savage assumes between himself and his name show how easy is the passage from belief in life inhering in every- thing, to belief in it as capable of power for good or evil. This can be shown by illustrations from more tangible July 11, 1884.] ♦ KNO\VLEDGE 23 things than namea The savage who is afraid to utter these, shrinks from having his likeness taken, in the feel- ing that some part of him is transferred, and at the mercy of the sorcerer and enemy. The Malemutes of North America refu.«ed to risk their lives before a jihotographic apparatus. They ^•aid that those who liad their likenesses, had their spirit, and they would not let these pass into the keeping of those who niiglit use them as instruments of torment. The Yanktons accused Catlin of causing a scarcity of buffaloes by putting a great many of them in his book, and refused to let him take their portraits. So with the Araucaniaiis, who ran away if any attempt was made to sketch them. Among such races, we find great care exercised lest cuttings of hair, pnrings of nails, saliva, refuse of food, water in which they had washed, Ac, should fall into unfriendly or mistrusted hands. The South Sea Island chiefs had servants following them with spittoons, that the saliva might be buried iu some hidden place. Among the Polynesians any one who fell ill attributed it to some sorcerer, who had got hold of refuse from the sick and was burning it, and the quiet of the night was often broken by the blowing of shi'll-trumpets, as signals for the sorcerer to stop until the gifts on their way to appease him could arrive. As with the name or the portrait, whoever possessed a part of the material substance possessed a part of the spiritual, and in this world-wide belief in a sympa thetic connection between things living and not livinglies the whole philosophy of sorcery, of charms, amulets, spells, and the general doctrine of luck surviving through the succes- sive stages of culture to this day. And he who wonld prevent anything from his person getting into hostile hands, naturally sought after things in which coveted qualities were believed to dwell, and avoided those of a reverse nature. So we find tiger's llesh eaten to give courage, and the eves of owls swallowed to give good sight in the dark. The Kaffirs prepare a powder made of the dried flesh of various wild beasts, the leopard, tiger, elephant, snake, etc., so as to absorb the several virtues of these creatures. The Tyrolese hunter wears his tuft of eagle's down to gain long sight and daring, and the Red Indian strings bears' claws round his neck to get Bruin's savage courage. The customs of scalping and, in some measure, of cannibalism, may be referred to the same notion, for the Red man will risk his life to prevent a tribesman's scalp being captured by the foe, and the New Zealander will swallow the eyes of his slain enem v to improve his sight. When a whaler died, the Eskimos distributed portions of his dried body among his friends, and rubbed the points of their lances with them, it being held that a weapon thus charmed would pierce a vital part in a whale, where another would fail. Sometimes the body was laid in a cave, and, before starting for the chase, the whalers would assemble, and, carrying it to a stream, plunge it in, and then drink the water. When the heroic Jesuit, Br^beuf, was tortured by the Iroquois, they were so astonished at his endurance, that they laid open his breast and came in a crowd to drink the blood of so valiant a foe, thinking to imbibe with it some portion of his courage. A chief tore out his heart and devoured it. Cannibalism, it may be remarked, en passant, is also found to have a religious significance, on the supposition, which has unsuspected survival among advanced races, that eating the body and drinking the blood communicates the spirit of the victim to the consumer. It is not always the most savage races who practise it ; for example, thei Australians, despite the scarcity of large animals for food: supply, rarely eat the flesh of man, whilst the Newi Zealanders, who rank far above them, and had not the like: excuse, were systematic feeders, op human flesh. :. . .. ! As examples of a reverse kind, but witnessing to the play of like beliefs in qualities passing from brutes and lifeless things, we finrl some races avoiding oil, lest the game slip thriiUgh their fingers, and abstaining from the flesh of deer, lest it engenders timidity, and of pigs and of tortoises, lest the eater has very small eyes. Dr. Tylor gives an a|iposite illustration of a kindred superstition in the He.ssian lad who thinks that he may escajie the conscription by carry- ing a baby-gii I's cap in his pocket, as a symbolical way of re- pudiating manhood. Among ourselves there was an old medical saw, "Hare-flesh engendereth melancholy bloude," and in Swift's " Polite Conversation " we have this reason assigned by Lady Answerall when asked to eat it ; whilst faith is not yet extinct in the " Doctrine of Signatures," or the notion that the appearance of a plant indicates the disease for which it is a remedy, as the " eyebright," the black-purple spot on the corolla of which was said to show that it was good for weak eyes. Ihand remarks* that the custom of giving infants coral to help in cutting the teeth, is said to be a survival of an old belief in it as an amulet ; and in English, Sicilian, and We.-t Indian folk-lore, we find the belief that it changes colour in sympathy with the pale or healthy look of the wearer. An old Latin author says : " It putteth of lighte- nynge, whirlewynde, tempeste, and stormes fro shyppes and houses that it is in." W^e are each of us hundreds of thousands of years old, and although our customs and beliefs have a far less venerable antiquity, their sources lie not less in primitive thought. Like the survival of the " casula " or " little house " or " .'jhelter " in the chasuble of the priest ; like the use of stone knives in circumcision long after the discovery of metals ; the general tends to become special ; the com- mon, its primitive need or service forgotten, to become sacred. Sumetimes the early idea abides ; the Crees, who carry about the bones of the dead carefully wrapped u]> as a fetish ; the Caribs, who think such relics can aaswer questions ; the Xomanes, who drink the powdered bones in water, that they may receive the spirit ; the Iroquois cited above ; represent the barbarous ancestry of higher races, whether of the Bacchanalians described by Arnobius, who thought that the fulness ,of the divine majesty was imparted to them when they tore and ate the struggling rams with mouths dripping with gore, or of the faithful who receive nutriment thrc iigh the symbols of the Cross. And the prayers of savage and civilised have this in common, that some advantage is thereby sought by the utterer ; their sacrifices are alike the giving up of one's goods or one's self to a deity who may be appeased or bribed thereby ; their fastings are cultivated as inducing the abnormal states in which their old men dream dreams and their young men see visions, spirits appearing as angels ascending and descending between earth and the abode of the blest ; their baptisms are the ancient lustrations, which water, as the cleansing element, suggested ; and their eastward position, over which jurists and ecclesiastics have fought, the undoubted relic of worship of the rising sun. In short, there is no rite or ceremony yet practised and revered amongst us which is not the lineal descendant of barbaric thought and usage, expressing a need which, were men less the slaves of creation and indolence, would long since have found loftier form than in genuflexion before shrine and reliquary. By an exercise of imagination not possible but for these being a felicitous " gesture language '' of the cries of human souls, a mass of heathen and' pagan rites have been transformed into those of the Christian i.:>*:>v,.' *"Pop. Ant.," II., 86. '•• 4}>*fif"'^ 24 * KNOWLEDGE [Jlly 11, 1884. faith. That they have coiue to be mistaken for the ideas symbolised; that with the lofiiest spiritual teaching there should remain commingled belief in miraculous power in fragments (mostly spurioue) of dead men and their clothes ; only shows the persistency of that notion of a vital connec- tion between the lifeless and the living which this jiaper has sought to illustrate. THE ENTOMOLOGY OF A POND. By E. a. Butler. THE MIDDLK DEPTHS {continited). THE larvw of these two great water-beetles are elongate, six-footed creatures, with powerful jaws (Fig. 1), presenting no sort of resemblance to the beetles themselves ; both are carnivorous and extremely voracious, dealing de- .struction to great numbers of their companions in pond- life. The ordinary spiracles being aborted, their respiration is conducted through certain projections at the tip of the tail, which are thrust above the surface to imbibe air. Having passed a comparatively short life in the larval con- dition, the insect quits the water, and, forming a cell in the damp margins of the pond, there effects its change to the pupal state. In due time the beetle is produced from this, Fig. 1. — I-.irva of Hydrophilna piceua. at first 6oft and pale, but acquiring, after a few days' expo- sure to the air, its normal colour and consistency. The female Hydrophilus forms a marvellous sac for the recep- tion of her eggs. It is composed of a gummy substance, the secretion of which is effected not in or near the mouth, but at the other end of the alimentary canal. A tough, papery bag is formed, which carries a long .spike, and is attached to subaqueous plants. The eggs, about fifty in number, are regularly placed side by side within this, and are thus protected from the attacks of such aquatic creatures as might feel disposed to try the taste of beetles' eggs. Another of the Philhydrida, a much smaller insect, of yellowish -brown colour, called Sperchevs emarginatus ( Fig. 2), which used to be found at Whittlesea Mere, and was supposed by many to have become extinct as a British species until recently rediscovered by Mr. T. R. Billups at a certain spot in the neighbourhood of South London, forms Fig. 3. — Spercheus emarginatus. a bag which the mother carries about on the under surface of her body. This insect, both in the larval and perfect state, is described by the Rev. W. W. Fowler, who has kept and watched the species, as having the peculiar habit of walking on the under-side of the surface of the water with its back downwards, after the fashion of a fly on a ceiling, a thin film of air contained between the body and the edges of the elytra seeming to act as a float ; the larva, too, is so completely permeated with air by means of its large trachea- as to be rendered quite buoyant, and to find, apparently, as much difliculty in sinking as a man with a cork jacket on ; so it needs no effort to maintain itself in its inverted position just below the surface. Water-beetles, as we have already .said, are not confined to the water, but at night frequently leave their native ponds and enjoy themselves in the air, or migrate to other quarters. >Jo collection of water is so small as not to prove attractive to them ; even cart-ruts that have been converted into so many miniature canals by a heavy rain may soon become tenanted. They cannot boast of any great brilliance of colouring. Yellows of no very con- spicuous hue, browns, greys and blacks, singly or inter- mixed, are the prevailing tints. Some few of the brighter yellow species are spotted with black, and so become rather pretty, and some of the Philhydrida are slightly adorned with spots and patches of a metallic tint something like that of " peacock copper ore," but with these few excep- tions they are a sombre set of insects, and their chief inte- rest certainly lies in the remarkable niodifications which fit them for aquatic life. We now pass to the Dipterous fauna of the middle depths. The Diptera, it will be remembered, are the two- winged flies, and none of these in the perfect state inhabit water ; some, however, are aquatic during their two earlier stages. Omitting a few very aberrant forms, there may be considered to be two very distinct types of tlies, one slender, with abnormally long and fragile legs, and with sintennje of moderate length, and frequently tufted or fringed with hairs ; the other stouter and more substantial, with much shorter legs, and antenn;e so inconspicuous as often to be unnoticed. It is to the former of these groups that most of the species whose larvse are aquatic belong. They consist of certain kinds of gnats, midges, and daddy-longlegs, insects whose names are as familiar as household words, though no very exact signification appears to be popularly attached — at any rate to the two former «i these, which are often vaguely used for any minute and delicate flying insect, of whatever nature. Very varied are the habits of the long-legged, long-horned flies : some of them are the causes of certain gall-like excrescences that occasionally disfigure plants, and inside which their larva' live ; the larva' of others, again, live in the earth, especially in damp places, and it is only a few members of the group that are aquatic, and that we have now to deal with. It may seem diflicult to conceive of a method by which 80 fragile a creature as a gnat, which would be irretrievably damaged by contact with the water, can manage safely to convey its eggs into such a position as will permit the larvae hatched from them at once to get into their proper element Most wonderful, indeed, is the plan adopted. Finding some floating shred of straw, stick, grass, or other such support, the expectant mother rests her two fore-legs on this, allows the next pair gently to touch the water, and crosses the third pair behind to form a sort of vice in which to hold the eggs as they are deposited. Then a long oval egg is lodged in the angle formed by the crossed legs, with its longer diameter vertical ; another, following it, is glued on to the side of the first in a similar position, and so on till some "200 or 300 are fastened into a sort of raft, or rather life-boat, as the mass is curved upwards at each end. Then the little vessel is abandoned to the mercy of winds and wavelets, and so floats about for a few days, benefiting by sun and air, till the growing embryos, finding their quarters too close, push open a kind of trap-door in the floor of the egg and take a dive at once into their watery home. They are qviaint-looking creatures, with a big head I July 11, 1884.] KNOWLEDGE 25 and thorax and long, tapering body, and tbey swim about head downwards. Near the tail, a straight bianch, carry- ing a number ot hairs at its tip, pi-qjccts at an angle with the body. This is a respiratory tube, and communicates both with the outer air at its tip, and with the tracheal system at its base. All that is necessary for breathing, therefore, is that the tip of this tube should be above the surface. Accordingly, when at rest, the larva takes up this position, while at other times it goes wriggling about through the water, being of sufficient buoyancy to rise without ettbrt to the surface when occasion demands. After several changes of skin the pupal stage is reached, and the last moult is accompanied by a remarkable alteration in the appearance of the insect. The head and thorax now appear as if thrown into one large mass, from which the body tapers away. But the most astonishing change of all is that which takes place in the respiratory system ; the entrance to this is now transfeiTed to the opposite end of the body, and appears as two small twisted horns projecting from the gigantic head. If now the insect were to retain its inverted position, there would obviously be no possibility of bringing these breathing horns nearer the air than a whole body's length ; therefore, it turns a somersault in the water, and henceforth goes about head uppermost, an attitude which, when it is at the surface, brings the organs in question just above the water. Though the creature is now a pupa, and can take no nourishment, it is possessed of almost as much freedom of motion as before, and jerks itself about by vigorous wrigglings of its awkward form. (To he continued.) A NOVEL FIRE-ESCAPE. THE sides of the block are united by four friction pins, arranged on two diagonal lines, and over which the rope or wire is passed (as clearly shown in the engi-aving). of the block runs a traveller, to which one end of a belt of leather or webbing is secured, the other end of the belt being provided with a hook to be passed over the rod. To use the e.'^cape, one end of the rope is hooked in the window-sill, and the other end thrown out of the window. The belt is passed round the body, and the hook clasped over the side rod. Then the person steps out ot the window and slides slowly down the rope, the friction pins in the block preventing a rapid descent. By means of the brake levers the appaiatus can be stopped at any time. When the block arrives at the ground, the person unfastens the belt, and the block is pulled up again to be used by another person, who throws the end of the rope that had been fastened in the room out of the window, and secures the opposite end. The device is portable, takes up a small space in a gripsack, and weighs but little. This invention has been patented by Messrs. David ^Yare and C. W. Richman, of Philadelphia, Pa. — Hcientijir American. The rope is also passed over pins at the top and bottom of the block. At each end of the block is pivoted a brake lever, the inner ends of which press the rope against the pins. On a rod secured to one of the outer side surfaces NOTES ON FLYING AND FLYING- MACHINES. By Rich.*rd a. Proctor. (Contimied from page 4.) BUT although the reasoning of Borelli suffices perfectly well to show that man can never fly by attaching pinions to his arms, and flapping these in imitation (how- ever close) of a bird's action in flying, it by no means follows that man must be unable to fly when the most powerful muscles of his body are called into action to move suitably-devised pinions. M. Besnier made a step in this direction (towards the close of the last century) when he employed, in his attemjits to fly, those powerful muscles of the arm which are used in supporting a weight over the shoulder (as when a bricklayer carries a hod, or when a countryman carries a load of hay with a pitchfork). But the way in which he employed the muscles of the leg was less satisfactory. In his method, a long rod passed over each shoulder, folding pinions being attached to both ends of each rod. When either end of a rod was drawn down, the descending pinion opened, the ascending pinion at the other end clo.sing ; and the two rods were worked by alter- nate downwaid pulls with the arms and legs. The down- ward pull with the arms was exceedingly etiective ; but the downward pull with the legs was altogether feeble. For the body lying horizontally, the muscles used in the downward pull with the legs were those by which the leg is carried forward in walking, and these muscles have very little strength, as any one will see who, standing upright on one leg, tries, without bending the knee of the other, to push forward any considerable weight with the front of this leg. Yet even with this imperfect contrivance Besnier achieved a partial success. His pinions did not, indeed, serve to raise him ii) the air ; but when, by a sharp run forward, he had brought that aerial supporting power into action of which we have spoken above, the pinions, sharply worked, so far sustained him as to allow him to cross a river of con- siderable width. It is not unlikely that, bad Besnier pro- vided fixed sustaining surfaces, in addition to the movable pinions, he might have increased the distance he could traverse. But, as regards flight, there was a further and much more serious defect in his apparatus. No means whatever were provided for propulsion. The wings tended to raise the body (this tendency only availing, however, to sustain it) : but they could give no forward motion. With 26 ♦ KNOWLEDGE . [Jlly 11, 1884. a slight modification, it is probable that Besnier's method would enable an active man to travel over ground with ex- treme rapidity, clearing impediments of considerable height, and taking tolerably wide rivers almost " in his stride " ; but 1 believe that the method could never enable men actually to fly. It may be remarked, indeed, that the art of flying, if it is ever attained, will probably be arrived at by means of attempts directed, in the first place, towards rapid passage along tp-red, the ingenuity of man is capable of contitructing machines in which these principles shall be carried out. Iron and steam have given man the power of surpassing the speed of the swiftest of four-footed creatures — the horse, the greyhound, and the antelope. We have full 28 • KNOWLEDGE . [Jdlt 11, 1884. confidence that the same useful servants place it in man's power to outvie in like manner the swiftest of winged creatures — the swallow, the pigeon, and the hawk. THE TRICYCLES OF TO-DAY. THE "CHKYLESMOKE CLUB." T " Cheylesmoie Club " is a very well-known type of double-driviug, rear-steering tricycle, and was, a season or two back, the general favourite of the London and large provincial clubs. It has, moreover, been largely supplied by the makers to many distinguished members of society. The frame is made of light steel tubing, and ball bearings are fitted to the driving and steering wheels, as well as the crank shaft, while the reputa- tion of the Coventry Machinists' Compsuy is a sufficient guarantee of the workmanship and high finish of the machine. The swan-like curved backbone, with little steering-wheel behind, gives it a very graceful appearance when in motion, causing it to contrast favourably with many front-steerers, which often put one so much in mind of perambulators and bath-chairs. The machine, however, of late ha.s lost some of i's original prestige, which is traceable to two jirincipal causes. The first reason uiay be readily accounted for by the great love of cycling novelty which is the inherent, ruling spirit of so many wheelmen, who are never satisfied unless they possess the " latest out," fancying, because there has re- cently been such a superabundance of animated discussion in numerous journals relating to improvements in tricycles, that the latest types of machines must of necessity po8se.ss great additional advantages over the older one?. The other reason, which has niilitiited to a very great extent against its continued popularity, has been the frequent warning raised on all hands — " Don't, my dear fellow, have a rear- steering tricycle unless you wish to break your neck ! " Now, undoubtedly the great majority of rearsteerers in the hands of careless or inexperienced riders are highly dangerous in descending hills, but the " Cheylesmore " is by no means to be classed in the same category. Not but what also there are other important exceptions of equally well-know rear-steerers which are in every way as safe as the " Cheylesmore," and with which I hope to deal in future papers. I may here state that I have ridden the " Cheylesmore " down e.icceedingly steep, stony, and rutty hills in Derbyshire, and on no single occasion have I come to grief. T remember quite well when first I rode the machine several friends of mine who ride front-steerers warned me to be very careful in descending hills, since the little wheel of rear-steerers was veiy apt to tip up, some- what after the fashion the rear-wheel serves bicycle learners. But my machine has never served me so, although its back- bone is several inches shorter than they are made this season, which alteration should certainly make them still steadier. The makers now attach when specially ordered a patent sliding-seat to the machine (see illustration), the position of which the rider can alter backwards or forward.s at plea- .sure, thus giving him the twofold advantage of being able to place his saddle directly over his pedals for hill climbing, or far back on the backbone when going down bank, in this manner preventing more than ever any slight tendency on the part of the machine either to swerve or tip up. To my mind, one of the most pleasureable features of the machine is the patent automatic clutch action. The clutch gear, which is exceedingly simple, and never liable to get out of order, is fitted to the pedal-cranks, being connected by cogs and chains to the driving-wheels. It consists of a small toothed box, through which the crank end passes without even coming into contact with it. The box, through which the crank passes, contains a small metal disc, which CS THE COVPriRrMACHIMIST PATENT SLIDING SEA' has four hollows cut in its circumference, round at one end and angular at the other. In each of these ca^-ities rides a small steel roller, which, on pedalling the crank forward, is jammed in the angular portion of the cavity, and thus pressed against the box, causing the wheel to rotate ; but on pedalling backwards the ball is released, and runs round freely in the circular portion of the cavity. Its action, however, will be clearly seen by a reference to the accompanying illustration. By means, therefore. of this simple contrivance the pedals remain perfectly stationary in descending hills, thus forming excellent footi-rests. It is decidedly advantageous to be able to use the pedals as foot-rests, since it enables the rider to cease pedalling on the smallest incline, his feet being ready for action when required, and no fear, as on other machines, of getting his ankles severally rapped in trying to replace his feet on swiftly-revolving pedals. It also empowers him to obtain a full leverage of the crank at any time he requires it, which proves very useful in climbing steep hills, by taking half-strokes. Some cyclists consider it a disadvantage, I know, at times not to be able to liack pedal ; but I have never found it so. The machine is supplied with an excellent spoon break, which is sufficiently powerful to bring the machine to a dead stop on almost any incline, while the steering arrange- ment is everything that can be desired. On a good level road there are but few machines which can pass it, and it is by no means a slow or bad hill-climber. In fact, take the July 11, 188t.] * KNOWLEDGE 29 " Cheylesmore " for all ia all, I consider it a cheap, safe, pretty, coiufortalile, and, in the hands of a good rider, a fairlj swift machine. F. THE ELECTRO-MAGNET. By W. Slisgo. PRESUMABLY most readers are acquainted with the general features of an electromagnet. It is, how- ever, an instrument or tool capable of performing such svonderful dexterities, and of affording such a valuable in- sight into the principles of electricity, that a few brief remarks upon its structure and its uses may, it is thought, be welcome. Electricity is not such a young science but that most people know the electro- magnet to consist primarily of a coil or helix of insulated wire and a piece of soft iron, and that a current of electricity, in traversing the wire, renders the iron a magnet. For the benefit of the uninitiated, and in order to present a more continuous series of exjieriiiients and illustrations, a few lines may be advantageously devoted to the simpler fundamental features pertaining to the subject prior to venturing upon that portion of it which will be kept more prominently in view — viz, the best form to be adopted for a parti- cular purpose, supplemented by directions for easily making and using the instrument. The two extremi- ties of au ordinary steel magnet exhibit a difference in their behaviour, and are therefore in themselves dif- ferent. Either end of a magnet attracts eqaally the same piece of unmagnetised iron, the difference being observable in the action of the ends or poles upon -each other. Two magnetised sewing needles suspended a few inches apart on water will, after a few second.% assume iparallel positions, the extremities pointing more or less north and south. If two of the similarly pointing ends be made to approach, repulsion ensues, while attraction results if the north-pointing eud of one needle is placed sufficiently near to the south-pointing end of the other. To magnetise the sewing-needles, they may be drawn a few times over one of the poles of a magnet, always drawing in one direction, either from eye to point, or point to eye. The end of the needle which last touches the magnet becomes of opposite polarity to that of the end of the magnet used. Thus, if the north end of a magnet be used, and a needle passed over it a few times, beginning at the ■ftye, then the |ioint viill be south (and the eye, of necessity, north). This follows as a matter of course, from the law that like polarities repel, and unlike attract, for we may ■easily conceive that the north makes itself evident at the ^e (the part most reniote from the magnet) in obedience to the repulsion by the north, and similarly that the point becomes south because of the closer proximity of the magnet-pole to the point than to the eye. Suppose now that above or below a copper wire capable of carrying a current of electricity from two or three cells we suspend an unmagnetised needle at right angles with the copper wire. On passing the current, the needle will become a more or less powerful magnet, particularly if the wire is placed east to west, so that the needle is north to south, when the inductive effect exerted by the current is aided by the magnetism of the earth, that magnetism which caused the suspended magnetised needles to poiiit north and south. If the needle be afterwards turned so as to point in some other direction, it will, when free, turn again to the north and south position, and will, in fact, .assume all the [iroperties of an ordinary magnet. Had the needle been an iron in'Stead of a steel one, a different result would have followed. The iron would have been magnetised on the passage of the current, just as the steel was, only more powerfully. On the cessation of the current, however, its effect upon the iron needle would have instantly ceased, although the needle would continue in obedience to inertia and to the feeble influence of terrestrial magnetism to point north and south. The difference between iron and steel is further seen on moving the former intu any other position than that of north and south. When this is done all trace of magnetisation is gone, and the iron exhibits no tendency to reassume the longitudinal direction. Had the iron been placed originally in any other than a north and south posi- tion it would not have felt, and, therefore, could not have retained the small effect produced by the magnetism of the earth. So far as the magnetisation due to the current is concerned, it is quite immaterial whether the previously unmagnetised needle be placed in a longitudinal or any other direction whatever, so long as the current is made to cross it at right angles. It follows, obviously, that if we encircle a needle by a ring or loop of copper-wire, and send a current through the wire, the electricity in any one part of the circle conspires with or aids the current in every other portion. A proportionate increase in the intensity of magnetism nattirally ensues. Carrying this jirinciple a little farther, if, instead of one circular loop we emjiloy several similar loops (wound round the needle in one con- stant direction, so that the current in traversing the wire is compelled to keep travelling from end to end without doubling back on itself) then the magnetising effect due to a single litie or loop is proportionably multiplied. Again, if we employ two or more concentric loops, such as we should get, for e.xample, by winding tie wire in a manner similar to that of a watch-spring, we shall produce a corre- sponding increase. It is apparent, then, how proportion- ately great must be the effect produced by a current passing through a long coil composed of several layers, as compared with that resulting from the passage of the same current through a single wire at right angles to the needle. The polarity which the needle assumes is dependent on the relative direction of the current. With a current pass- ing over the needle from, say, south to north, the eye or the point, whichever it may be that is in the west, assumes a north polarity, while that extremity of the needle which lies to the east of the wire becomes a south pole. Gene- rallv, to adopt an illustration of Ampere's, assuming a little man to be swimming in the wire in the same direction a.s the current, and to have his face turned constantly towards the needle, that end will become north which is on his left hand. The same principle is involved here as in the case of galvanometers, and demonstrates the multiplying power of coils of wire. When a soft iron wire is used instead of the steel needle, the effect produced by a current traversing the enveloping coil of wire ceases with the current, just as the effect pro- duced by a current in a single length of wire was no longer felt when the current disappeared. Of the relation sub- sisting between the effective power of a sii gle wire and a coil, more will be said presently. B.fore we can predetermine the polarity an iron wire or rod will assume in response to the inductive effect ex- erted by a coil of wire, we mast bear in mind that there are two ways of winding a coil, and that the electro- magnetic effects exerted by these two coils are opposite. This may be experimentally demonstrated with the aid of an iron rod such as, for want of something else, a clean poker, a yard or two of cotton-covered or other insulated wire (rather stout, say No. 16, B.W.G.), a magnetised sewing- 30 ♦ KNOWLEDGE ♦ [July 11, 1884. needle, and two or three cells of, say, a bichromate battery. First, float the needle on a glass of water by laying it on a small piece of paper or cork. (If the baud and the needle are dry, the film of air adherent to or surrounding the needle will, generally speaking, prevent it from sinking.) Then, holding the handle of the poker and one end of the wire in the left hand, held out from the body, proceed to wind the wiie over the other end of the poker with the riglit hand, moving the hand continuously in the same direction as that taken by the hands of a watch, as seen when lookiig at its face. In other words, taking the wire in the right hand, pas.s it from the upper side down the right side across the bottom, and back up the left side. In this way cover the square end of the poker with one layer or thickness of wire. Such a coil of wire is called a helix, and helices are divided into two class^es — called right- handed and left-handed (according to the direction of wind- ing). The helix just constructed and illustrated in Fig. 1 (depicting an iron rod, X S, inside of a piece of glass tubing, over which the wire is wound), is a left-handed one — a current on entering it at either end travelling through it in a direction opi osite to that of the hands of a watch. To secure a right-handed helix (Fig. 2), ^(2V^ Fig. 2. wind the wire round the ])oker from right to left, or move the hand in the oppo.site direction to that of the watch hands. The current in flowing through thi.s helix tr.avels in the opposite direction to that taken in the other, and, as we might anticipate, different causes produce different effects. (To ie contimied.) THE ANTARCTIC REGIONS. By R. a. Proctor. (Continued from page 7.) IT is singular how confidently geographers have spoken of the great Antarctic continent, when we remember that only an inconsiderable extent of coast line has even been seen by Anctarctic voyagers in any longitudes, except where Ross made his nearest approach to the South Pole. There is absolutely not a particle of evidence for believing that the ice-barriers which have been encountered — Sabine Land, Adelie Land, Victoria Land, and Graham Land — belong to one and the same land region. It is not, indeed, certain that all tlie mapped coast-line is correct — for it must not be forgotten that where Commodore Wilkes charted down a coast-line Ross found an open (or only ice-encum- bered) sea, and sailed there. Yet Dr. Jilek, in the "Text-book of Oceanography," in use in the Imperial Naval Academy of Vienna, writes thus confidently respecting the Antarctic continent : — " There is now no doubt," he says, " that around the South Pole there is extended a great continent, mainly within the polar circle, since, although we do not know it in its full extent, yet the portions with which we have become acquainted, and the investigations made, furnish sufficient evidence to infer the existence of such with certainty. This southera or Antarctic continent advances farthest in a peninsula S.S.E. of the southern end of Americu, reaching in Trinity Land almost to 62 degrees south latitude. Outwardly these lands exhibit a naked, rocky, partly volcanic desert, with high rocks, destitute of vegetation, always covered with ice and snow, and so surrounded with ice that it is difiicult or impossible to examine the coast very closely." A singular, and indeed fallacious, argument has been advanced by Captain JIaury in favour of the theory that the Antarctic regions are occupied by a great continent. " It seems to be a physical necessity," he argues, "that land- should not be antipodal to land. Except a small portion of South America and Asia, land is always opposite to water. Mr. Gardner has called attention to the fact that only one twenty-seventh part of the land is antipodal to land. The belief is, that on the polar side of 70 degrees- north we have mostly water, not land. This law of dis- tribution, so far as it applies, is in favour of land in the opposite zone." Surely a weaker argument has seldom been advanced on any subject of scientific speculation. Here is the syllogism : we have reason to believe (though we are by no means sure) that the Arctic regions are occupied by water ; land is very seldom found to be anti- podal to land ; therefore, probably, the Antarctic regions are occupied Viy land. But it is manifest that, apart from the weakness of the first premiss, the second has do bearing whatever on the subject at issue, if the jirst he admitted : for we have no observed fact tending to show that water is very seldom antipodal to water, which wouW be the sole law to guide us in forming an opinion as to the regions antipodal to the supposed Arctic water. On the contrary, we know that water is very commonly antipodal to water. We have only to combine what is known respecting the relative ])roportions of land and water on our globe with Mr. Gardner's statement that twenty-six out of twenty-seven parts of the land are anti- podal to water, to see that this must be so. There are about .51 millions of square miles of land and about 146 millions of square miles of ocean. Now about 49 millions of square miles of land are antipodal to water, accounting therefore for only 49 millions out of the 146 millions of square miles of ocean surface ; the remaining 97 millions of square miles of ocean are, therefore, not antipodal to land, but one half (any we please) antipodal to the other half. In fast, we have this rather singular result, that the ocean surface of the globe can be divided into three nearly equal parts, of which one is antipodal to land, while the other two parts are antipodal to each other. This ob\"iously doe.s not force upon us the conclusion that an unknown region must be land because a known region opposite to it is oceanic ; and still less can such a conclusion be insisted upon when the region opposite the unknown one is itself unknown.* * Whether the relation above-meutioned respecting Xand regions- is noteworthy may very well be questioned. It will be seen that Captain Maury regards it as seemingly a physical lore " that land should not be antipodal to land." Now this is by no means satis- factorily indicated. As a question of probability it is not certain that the present relation, by which twenty-six parts out of twenty- seven of the land are antipodal to water, can be rej^rded as antecedently an unlikely one, when nearly three-fourths of the whole surface are occupied by water, and when, also, the bulk of the land and water regions consist of such great surfaces as those we call continents and oceans. Granted these preliminary conditions, it would appear, indeed, that only by a very remarkable and, as it were, artificial arrangrtnent of land and water could any btit a small proportion of the land be antipodal to land. The stress laid by JIanry on the observed rela- tion seems to me, indeed, as unwarranted as that laid by Humboldt on the fact that the great southerly projections of the land lie nearly in the same longitude as the great northerly projectioms. July U, 1884.] KNOWLEDGE 31 So far, indeed, as the geographical evidence extends, it seems proltable that there exists within the Antarctic circle an ehrviited region bearing somewhat the same i elation to the grea^ promontories terminitled by Cape Hoin and the Cape of Good Hope, as well as to the relatively elevated region indicated by the islands to the south and south-east of Au-tralia, which the Hindoo Koosh bears to the great mountain-ranges of Asia. We seem to have in the An- tarctic high lands the great central elevation whence three great lines of elevation extend. That the great mountain range which forms the backbone of South America is con- tinued under water, rising again in the south Shetland Isles and Gralja«i's Land, would, indeed, seem altogether probable ; and it may be remarked as a coincidence of some importance that the mountains seen by Ross on the other side of the Antarctic Circle — Mounts Sabine, Crozier, Erebus, asid Ross — lie in a chain tending in the same directiMi. But although we might thus be led to regard the Antarctic regions as forming a great central region of elevatioa, it by no means follows that this region is of the nature of a table land. Meteorological considerations have been urged by ]\Iaury for the tl)«ory of Antarctic lands in large masses, " relieved by high mountains and lofty peaks." He considers that it is to such mountains (performing the part of condensers) that the st-eady flow of " brave " winds towards the South Pole is to be ascribed. " Mountain masses," he says, " ap- pear to perform in the chambers of the u])per air the office "whicii the jet of cold water discharges for the exhausted steam in the condenser of an engine. The presence of land, therefore, not water, about this south polar stopping- place is suggested." And he attaches considerable weight, in this connection, to the circumstance that the barometric pressure is singularly low over the whole Antarctic ■Ocean,* — as though there were here the vortex of a mighty but steady whirlwind. "We may contemplate the whole system of 'brave west winds,' circulating in the Antarctic regions, tn the light of an everlasting cyclone on a gigantic scale — the Antarctic continent in its vortex — about which the wind in the great atmospherical ocean all round the world, from the pole to the edge of the calm belt of Capri- corn, is revolving in spiral curves, continually going with the hands of a watch, and twisting from right to left." However, it would be unsafe to base the theory of an Antarctic continent on speculations such as these. And still less can we assume with Maury that Antarctic volcanoes play an important part in the economy of southern meteorological phenomena. There is no reason •for supposing that active volcanoes have any special action in determining atmospheric relations. Capt. Maiirj- sug- gests that we may, " without transcending the limits of legitimate speculation, invest the unexplored Antarctic land with numerous and active volcanoes," and this cer- tainly may be granted, for two volcanoes (one in action) have been seen there. But it would be unsafe to infer that such volcanoes are " sources of dynamical force suffi- cient to give that freshness and vigour to the atmospherical circulations which observations have abundantly shown to * This curioas circumstance cannot be explained, as Maury sup- poses, by the existence of upflowing currents of air, however occasioned. The total pressure of the air over any region is not affected by motions taking place within the air, any more than the total pressure of water upon the bottom of a tank is affected by motions taking place in the water. There are reasons for believing that the true explanation of the low Antarctic barometer lies in the fact that the ocean surface is in Antarctic regions aiove, and in Arctic regions beloiv, the mean level. The excess of ocean surface in the southern hemisphere indicates an overflow, as it were, of water southwai-ds, which must lead to such a relation. — See my 'Light Science for Leisure Hours," Second Series. be peculiar to the southern hemisphere." Volcanoes would need to be so numerous and so active, in order to produce the imagined effect, that the whole southern continent would be aglow like a gigantic furnace. A hundred Etnas would not produce the thousandth part of the indraught which Maury ascribes to Antarctic volcanoes. Assuredly, we may say with Maury, but more .significantly, that "volcanoes are not a meteorological necessity." "We cannot say that they are," he proceeds, "yet the force and regularity of the winds remind us that their pre.-ence there would not be inconsistent w'ith known laws." He believes, in fact, that the steady wuids may be partly formed as an indraught feeding volcanic fires. It is as well to remem- ber, when ideas so wild are mooted, that, as Maury himself remarks, " we know, ocularly, but little more of the topo- graphical features of Antarctic regions than we do of those of one of the planets." " If they be continental," as he proceeds, " we may indeed, without any unwarrantable stretch of the imagination, relieve the face of nature there with snow-clad mountains, and diversify the landscape with flaming volcanoes ; " but we must not forget that this is a work of imagination, not a theory which can be insisted upon as though it represented a geographical fact. While on this subject, however, I cannot refrain from quoting a very striking ))assage from a letter Viy Capt. Howes, of the Southern, Cross, because, although it relates ill reality to the phenomena of an Aurora Australis, it presents a scene such as we might conceive to accord with the conception of an Antarctic region covered with vol- canoes whose combined action made the whole continent at times as one vast furnace. Apart from fancies such as these, the description is full of interest : — " At about half- past one," he says, "on the second of last September, the rare phenomenon of the Aurora Australis manifested itself in a most magniticent manner. Our ship was off Cape Horn, in a violent gale, ))lunging furiously into a heavy sea, flooding her decks, aud sometimes burying her whole bows beneath the waves. The heavens were as black as death ; not a star was to be seen when the brilliant spec- tacle first appeared. I cannot describe the awful grandeur of the scene ; the heavens gradually changed from murky blackness till they became like livid fire, reflecting a lurid, glowing brilliancy over everything. The ocean appeared like a sea of vermilion lashed into fury by the storm ; the waves, dashing furiously over our side, ever and anon rushed to leeward in crimson torrents. Our whole ship — sails, spars, and all — seemed to partake of the same ruddy hues They were as if lighted up by some terrible con- flagration. Taking all together, the howling, shrieking storm, the noble ship plunging fearlessly beneath the crimson-crested waves, the furious squalls of hail, snow, and sleet driving over the vessel and falling to leeward in ruddy showers, the mysterious balls of electric fire resting on our mast-heads, yard-arms, &c., and above all the awful sublimity of the heavens, through which coruscations of auroral light would often shoot in spiral streaks and with meteoric brilliancy, altogether presented a scene of grandeur and sublimity surpassing the wildest dreams of fancy." {To he continued). Erratum. — In the paragraph at the bottom of second column, page 9 (last week's Knowledge) for "equatorial circle" read " equatorial coudee." The Western Union Telegraph Company at a meeting last month, declared the usual IJ per cent, quarterly dividend. The present quarter closes the fiscal year, which exhibits gross earnings of nearly 26,000,000 dols., about"500,000 dols. more than last year, but, on account of expenses during the strike, the net earnings will not be quite so large. The last and present quarters show an excess of net earnings over the corresponding quarters of last year. 32 • KNOWLEDGE [July 11, 1884. OPTICAL RECREATIONS. Bv A Fellow of the Royal Astrosojiical Society. (Continued from p. 482.) WE stated on p. 307 that light travels in straight lines, but we must now introduce a qualification into thi.s general statement, and add, as lonr/ as it is passing tliroucjh a homogeneous mndium — or one ofahsoluteJy uniform density throughout. This is the way we proceed in physical science. We first enunciate a law which we assume to be universal, and then we deal with what are — or seem to be — exceptions to it ; and ascertain and show whether they are really so, or whether both they and the facts on which our original asstimption was founded may not in reality be susceptible of inclusion in a higher and more general law still. Now while it is perfectly true, as we have just said, that the propagation of light is absolutely rectilinear (or io straight lines) in a medium of uniform density, when it passes from a rarer medium into a denser one, or rice-versA — save in a direction accurately square to the surface bounding such two media — it is bent from its original direction, or, to use the technical term, " refracted." This may be well shown, and an approximation made to the determination of the law of retraction, by the simjile apparatus depicted in Fig. U. It is nothing more than a clear glass (18oz ) physic bottle, on the front of which a piece of white pajier is pasted. Prior to stickin? the paper on, an accurate circle uiust be cut out of it ; and, when all is dry, two thick diametrical lines, P, P' H H', may be ruled in ink on the glass, the first vertical and the second truly square to it, of course horizon- tal. Or, if preferred, two pieces of stout filk cord may be gummed across the aperture. A piece of blackened card should be cut out to cover one of the narrower sides of the bottl?, and near the top of this a hole; or, perhajis, pre- ferably a horizontal slit should be cut. The slit must be a very narrow one. We must now fill our bottle exactly up to the line H, H' with water, j^lst coloured with a little milk, and, immediately before beginning our experiment, pufl" a mouthful of cigar smoke into the mouth of the bottle. We employ the milk and the smoke in order that we may see our lieam of light, for the student will recol- lect (p. 30G) that light passing in a direction across our line of sight is absolutely invisible. Very well, then, we have next to obtain our beam of light ; and, undoubtedly, for the majority of ojitical experiments, direct sunlight is the best. In the present case, though, this involves the use of a darkened loom with a narrow beatu. of sunlight admitteii through a hole in the shutter. If the reader has any apartment at his dis^posal which he can so employ, and which is sufficiently light-tight, so much the better ; if not, he may use a good kerosine lamp and a. buU'seye condenser, and conduct his investigation at night. Whichever source of light he employs, he must, by the aid of a looking-glass or otherwise, throw the beam proceeding from it through the slit in the blackened card at the side of the bottle, shifting the mirror about until the line of light strikes the surface of the water at C. Our puff of tobacco smoke will enable him to do this. Now trace the course of the light through the slightly tuibid water, and carefully note the path it takes. Is no longer preserves its original direction, but is bent towards PF ; in other words, its track becomes more upright. Bear in mind that, coming through the side of the bottle, it has originally struck the surface of the water obliquely. Had we sent it through the mouth of the bottle truly square to the surface of the water it would have preserved its perpendicular direction throughout — much in the same way (though, of course, in one sense, for a diffe- rent reason) that a perpendicular ray which falls on a mirror is reflected accurately back along the line by which it originally travelled. This by the way. To return to our experiment. Note where the beam of light cuts the semi- circle H, P, H', before entering the water ; as ako the point where it crosses the semicircle H, P', H', after having done so, and draw ink lines from these points to the perpen- dicular P, P', taking care that those lines are parallel to H, II'. If we measure these lines carefully with a [lair of compasses we shall find that the one above the water is — as nearly as may be — 1 J times the length of the lower one. And, what is particularly to be remarked, that while the length of these respective lines varies with the obliquity with which the light falls on the surface of the water, the proportion between them remains invariable. Before pro- ceeding to investigate the law of Refraction we may just remark incidentally that, as our exjjeriment has been so far conducted, evidently part of the light has been reflected from the surface of the water, the unreflected portion alone, of course, penetrating it. For our present purpose, how- ever, we may neglect this reflected part altogether, and consider that the whole incident beam enters the water, and is bent at the surface where it does so. By the aid of Fig. 1.3 we may now explain the law in virtue of which .1 Fig. 15. light follows a fixed and definite course rn passiag froED any medium into another of different density — a law dis- covered by Sriell during the first quarter erf the seventeenth July 11, 1884.] • KNOWLEDGE • 33 century. We have said above that had we sent our beam of light perjiendicularly into the water it would have pursued a rigidly rectilinear jiath throughout. If, though, light struck its surface at all obliquely, refraction would occur at once. As we have had ocular demonstration by the aid of 'our bottle, when light passes from a rarer medium into a denser one it is bent towards a perpendicular to the refracting surface. On the othfr hand, when it passes from a denser medium into a rarer one it is bent from the perpendicular. And this brings us to the incidental mention of the principle of reversibility. By whatever path light travels from air into water, by that same path will it return from water into air. So, again, in Figs. (!, 10, 11, the object and its reflected image may be regarded as interchangeable in their respective positions. We shall probably have occasion to reiterate and insist upon this law, lying as it does at the root of numerous optical jihenomena. Reverting, however, to our figure. The law discovered by Snell was this — that when light passes from any medium to another of different density the sine of the angle of incidence always bears a fixed and de- finite ratio (or proportion) to the sine of the angle of refrac- tion. The sine of an angle is defined in old niathematical books — in a way much more intelligible to the learner than that employed in more modern ones — as a line drawn from one extremity of an arc at right angles to the diameter from the other extremity. Thus, in Fig. 15, PiS is the sine of the angle R C P ; R' S' the sine of the angle R' C P ; m the sine of the angle rCP', and r's' the sine of the angle '/•' C P'. A little attention will show how these conform to the definition just given. Then, Snell's law says this : if (as we shall find to be the case) RS is 1 J times the length of r s, R' S' will be 1^ times the length of r' s', and so on for any angle of incidence we may select. Now, here we will pause to call attention to a very remarkable circum- stance. We have said that light passing from air into water will be refracted, if it do so, " at any angle of inci- dence ; " but, if the student has followed us attentively so far, he will see that the converse of this will not hold good, and that our choice of angles of incidence in the passage of light from vater to air is not unlimited. For it is easy to see that the angle of incidence might be so great that the sine of the angle of refraction being \\ times as large must be greater than CW, the radius of the circle, which is impossible ; or, to put it another way, he may select such an angle of incidence in water that the light must emerge parallel with the surface, and when we increase such angle the light cannot get out of the icater at all, and is totally reflected. The incidental angle at which the emergent ray is parallel to — or, rather, in — the surface of the water, is known technically as " the critical angle." Total reflection may be observed by looking obliquely upwards at the inner surface of the water in a clear glass tumbler at the image of a candle, a silver spoon, or other bright object held on the other side of the tumbler. It may also often be noticed in aquaria, such as the one at Brighton, in which the surface of the water seen at the proper angle from beneath reflects the fish near it, and shines like molten silver. Or, by turning our card, which covers the side of the bottle in Fig. 14, upside down, so that the slit in it is below the level of the water, we may reflect our beam of light upwards to its inner surface, and trace its reflection visibly. The " mirage " of the desert is believed to have its origin in total reflection from the sur- face formed by two adjacent strata of air of different tem- peratures and densities. We have spoken of the sine of the angle of incidence of a ray of light passing from air into water being 11 times the length of the fine of refraction. It is more accurately 1-336 times that length; and this number 1-33G is called " the index of refraction " of waterj The denser a body the higher its index of refraction. Thus it is I'.'iT") in flint glass, and sometimes as high as 2-75 in the diamond. Hence the incomparable lustre of this stone. Numerous illustrations of refraction will occur to the reader. One of the most familiar is none the less instructive. Let him get a pie-dish, and put a sixpence at the bottom of it. Now, let him walk back- wards until the side of the dish just hides the sixpence, and remain perfectly still while some one else pours water into the dish. The effect will be to bring the sixpence into view again. Fig. 1.") will show how the water bends the r.iys of light from the coin over the rim of the dish. Or he may vary the experiment by so placing a lamp that the side of the pie-dish casts a long shadow on the bottom of it when empty. Then, as before, on pouring in water, the shadow will be seen to shorten perceptibly, and to approach- the side casting it. So an oar or a stick partly immersed in water seems broken or bent at the surface ; and a fisher- man looking obliquely at the bottom of a clear lake from its bank sees it apparently only about three-quarters of its- real depth. Or, instead of water, we may employ a thick piece of plate-gla.ss to produce refraction ; and, hiding some writing behind the edge of a thin book lying flat on a table, as we did the sixpence with the edge of the pie dish, bring it into view again by placing our piece of plate-glass upon it. And the mention of jilateglass suggests to us here to investigate the course of a ray of light passing, through such a medium. In Fig. 16, G G is a sectioa Fig. IG. or edgeways view of a window-pane ; R P, a ray (suppose from a tree-top) incident on the outside of the glass at P. Then, as we have seen above, this ray will be bent towards the perpendicular in the glass. On reaching the other surface, however, at p, it will be bent from the perpendicular, and will follow the direction pE, parallel to RP, and will be seen by an eye at E as though it emanated from R', thus slightly raising our ima- ginary tree-top. Inasmuch, however, as the whole land- scape is equally raised, ybr the same obliquity of vision, no sensible distortion is apparent. Quite obviously, objects from which rays fall square on to the surface of the glass suffer no apparent change of position whatever. It must be pretty evident that the higher the refractive index of any sub- stance, the greater the displacement of a ray of light passing through it ; so that if we could conceive a window formed of sheets of diamond, and one pane to be left open, the landscape would be very notably raised as viewed through 34 ♦ KNOWLEDGE . [July 11, 1884. a closed pane contiguous to the open one. A most beau- tiful experiment, illustrating both refraction and total re- flection (for the idea of which we are indebted to a little book on " Light," by Mayer and Barnard, published by Macmillan ct Co.), will probably come in here most appro- priately. Fig. 17 is intended to illustrate it. Fig. 17. The reader should buy the biggest globular glass flask <;hat he can obtain, and have a hole drilled in its side at the shop where he buys it. Stopping this hole with a cork, the bottle must be filled with water, and a parallel 'beam of light from a kerosine lamp and a bull's-eye lens be projected on to the side of the flask, in the way illustrated by our figure. It must be so managed that the refraction shall bring the rays of light, of which the beam is composed, to a focus on the cork, and the lamp should be enclosed in a box, or otherwise so surrounded by opaque material, that the room would be dark but for the light passing into the bottle. This condition of things being secured, a pail may be placed on the floor, and the cork taken out of the side -of the bottle ; when a most beautiful etfect will be per- ceived. The light will be totally reflected from the inner surface of the issuing jet of water, which will appear like a stream of molten silver, and the interposition of coloured glasses between the source of light and the bottle will tinge this of their own hues. Of course, sunlight or the •electrical light will give even more brilliant results still. It was by the aid of the latter, projected in this way through variously-coloured media, that the so-called " Fairy Fountain " was managed which was exhibited at the ■defunct Panopticon in London. In our next paper we shall enter upon the subject of refraction through successive surfaces, which, unlike those ■of the window-pane spoken of above, are inclined to each other. The couvers.azioue of the Societj- of Tele/ set?erely : '* It is very rude, sir, to make any remarks. The fact is, sir, you are a professional player, and I shall not play with you any more." London player is given £5 to go home, and prominent player and supporter of the C C.A. wins sundry prizes. A Mr. Miller has stated in the press that Morphy could have given Zukertort a Knight. On his visit to Cincinnati, Zukertort meets this Miller at a large party, and plays with him ten games, winning every ganK\ Says the champion, within hearing of the com- pany : " A namesake of yours has declared that Morphy could give me a Knight ! do you think so ? " Collapse and discomfiture of Miller. We wonder whether this is the same Mr. Miller who has taken upon himself the inglorious task of reprinting the third edition of Cook's " Synopsis." Has ho asked the author's permission':' Besides, as a fourth edition of thu "Synopsis" is in the press, and Mr. Marriott has, likewise, a useful book all but printed, we would warn the American public against making a useless invest- ment, and keep their money for the fourth edition, which we hear will bo a great improvement on the third. A BRITLSir CHESS ASSOCIATION. In an ably-wi-ittcn leader in the Field, the writer advocates the establishment of a British Che.ss Association, to take the place of and supersede the Counties Chess Association. That which strikes mo as being the most important consideration seems to have been quite overlooked in the arguments in favour of the scheme ; for to attempt for one moment to draw comparison between Chess and other sports, is to assume, priiiui fai-ie, a false standjioint alto- gether. Although the number of devotees to the noblest and most fascinating of games is undoubtedly on the increase, the fact cannot be denied that all outdoor sports, inasmuch as they are easily appreciated by the masses, besides being healthy and ex- hilarating, will, as long as the world stands, command a far greater patronage than Chess. It is, therefore, open to doubt whether, even with the assistance of Royal patronage, the necessary constant supply of funds will always be fortlicoming for carrying out the annual tourneys and prize competitions projected. The consummation of the project, however, would, I am sure, be hailed with delight by all British Chess-players, amateur and pro- fessional alike. In the interest of the Koyal game, it is sincerely to be hoped that it will be a success. All players will then nndoubtedly welcome the Chess Editor of the Field as the "Mahdi" of Chess. Borealis. THE EDY LOPEZ (continued Srom page 419). If in this position White plays 5. P to Q4, Black can arrive at a position already dealt with : — Buck. 1 2 tit?' 1 t 1 lit •• ^' _ ^ '1 i 1 0 2 P- .^^ -; 5. PxP 6. Kt to K5 7. B to K2 8. Kt to B4 9. QPxB 0. Castles, 5. P to Q 1 6. P to K5 T. Castles 8. R to Ksq 9. B X Kt. 10. KtxP with a safe game. Should White play 5. Kt to QB3, Black may continue with ."). B to Kt5, followed by Castling, and the positions will be fairly equal. The strongest although the """"■ least attacking continuation is 5. P to Q.3. This move will be found in many games of the London Tournament. This move brings about a sti'uggle for position only, and is, therefore, more suited for match play than for ordinary practice. By P to Q3 White protects his own Pawn and threatens B X Kt, followed by Kt x P. Now the question is which way best to defend the KP. Q to K2 would, Hof course, not be a good move ; there remains, therefore, only 5. P to Q3. In this case, however. Black's KB will only liud development by way of P to KKt3, while the white KB will be well placed either on Kt3, or if P to QB3 has preceded, on B2. The disadvantage of Black's position is some- what similar to the Philidor defence. Having indicated the general principle of this opening, we do not think we need give any parti- cular variation, as White has nothing to do but to develop his game. It is a thoroughly reliable opening. No solution ha\'ing reached us of Mr. Carpenter's Problem, we 'defer the solution till next week. During Dr. Zukertort's stay in New Orleans, he contested altogether twenty-two games with Mr. Jas. McConnell, of which the doctor won fourteen, lost five, and drew three. The last game between the players during Dr. Zukertort's visit. at N'nw Orleans, May 12, 1881- : — PHILIDOK'S DEFENCE. Black. Dr. Zukertort. P to K4 P to Q3 Kt to QB3 (6) Wlite. Black. >Ir. .la?. M'Connell. Dr. Zukertort. 13. KtxQP B to Kt2 11. Castles (QR) P x P (3) 15. KttoKC(ch)!BxKt 16. Q X QP (eh) K to Ksq 17. B X B Kt to Q4 18. Q to Q7 (ch) K to Bsq 19. B X Kt (h) R to Qsq 20. Q X KtP Q to B5 (ch) 21. K to Ktsq BxKt 22. QxBP! BtoB3 23. BxP White. Mr. Jas. M'Connell 1. P to K4 2. Kt to KB3 3. B to Bi (a) 4. P to QR3 (c) P to KB4 5. P to Q3 Kt to KB3 6. B to KKt5 P to KR3 (d) 7. B X Kt Q X B 8. Kt to QB3 Kt to K2 9. KttoQKt5(e)KtoQsq 10. Q to Q2 P to QB3 11. Kt to B3 P to KKt4 12. P to Q4 P X QP (/) And Black resigns. NOTKS. (n) A continuation favoured by Mr. Boden, but generally held inferior to 3. P to Q4. Of late, however, some strong players, notable among them Mr. Blackbiime, we believe, have shown a predilection for the text move. {b) 3. ** B to K2, introduced by Harrwitz in his match with Loewenthal, is more usual and apparently stronger. (r) Evidently to provide a retreat for the Bishop, should'the adverse Knight attack from E4 ; but 4. P to Q4 se«me preferable either on this or White's next move. ((?) Here once again 6. •• B to K2 appears best. (c) A well-timed advance. White has now secured a marked advantage in position. (/) Would not 12. ** Kt to Kt3, instead, have been a much stronger reply ? (a) Too covetous by half, and seemingly quite unprepared for the pretty stroke of play with which his opponent at once replies, (h) Even 19. Kt x Kt wonld have been safe, for Black had nothing hot a few unavailing checks. Indeed, the latter's game lias been most seriously compromised, if not defenceless for some time past. — Times Democrat. The ANSWERS TO CORRESPONDENTS. •»* Please addrcDs Chess Editcr, The Owl. — We regret to say that Problems are not suitable. Problem cannot be done in two moves. Jlrs. H. W. — It is desirable that all variations should be given in a solution. Solution correct. A. W. Overton. — Solution of above Problem correct. Contents op Kg. 140. F16B Chemistrr of Cookery. XXSTII. By W.'M. Williams 1 Notes on Fl.vine and Flying-Ma- chinea. Bv Richard A. froctor... 2 Elect ro-platiiig. Til. By W. Slingo 4 Comet" Families of the Giant Planets. By Richard A. Proctor 5 Photographing a Flash of Light- ning. {Wits.) 6 The Antarctic Regions By R. A. Proctor 6 International Health Exhibition. — VI. Water and Water Supplies ... 7 Msa On Peculiarities of Siijht and Opti- cal Illusions. Bv N. E. Green ... ** The Evolution of Flowers. {lUtu.) By Grant Allen 10 Conceit (for Sell and Familj) . By R. A. Proctor 11 Reviews 13 Editorial Gossip l.'i The Face of the Skjr. By F.H.A.S. 14 Correspondence 14 Our Paradoi Column 17 Our Mathematical Coltmm 18 Our Whist Column 19 Our Chess Colmnn 20 SPECIAL NOTICE. Part XXXII. (June, 1884), now ready, price Is., post-free. Is. 3d. Yolurae T., comprising the numbers pablished from January to June, 18d4, will g(.>on be ready, price 9s., including parcels postage, Os. 6d. Binding Cases for all the Volumes published are to be had, price 28. each ; including parcel postage, 2s. 3d. Subscribers' numbers bound (including title, index, and case) for 3b. each Volume ; including return joumey per parcels post, 3a. 6d, Remittances should in every case accompany parcels for binding. TERMS OF subscription: The terms of Annual Subscription to the weekly numbers of KxOTyLBDGB are x^f follows : — 8. d. To any address in the United Kingdom 16 2 To the Continent, Australia. New Zealand, South Africa, & Canada 17 4 To the United States of America ^.25 or 17 4 To the East Indies. China, &c (rm Brindisi) 19 6 All subscriptions are parable in advance. OFFICE : 74-76, GREAT QUEEN STREET, LONDON, W.C- July 18, 1884.] ♦ KNOWLEDGE ♦ 43 MAGAZINE OF SCIENCE NLYWORDED-EXACTLYDESCRIBED LONDON: FRIDAY, JULY 18, 1884. Contents op Ko. 142. PAGB Other Worlds than Ours. By M. de Fontenelle. Wiih Notes by Richard A. Proftor {Contituud)... 13 Chemistry of Cookery. XXXVIII. ByW. M. Williams 41 Man and Nature 45 Optical Recreations. (lUas,) By F.K.A.S 46 Electro-plating. Till. By TV. Slineo 47 The Entomology of a Pond. By E. A. Butler 49 Superstition 50 International Health Exhibition, VIII. {Illus.) 60 British Seaside Resorts. I. By Percv Russell 52 Zodiacal Maps. (Itlus.) By R. A. Proctor 5i The Antarctic Kegions By R. A. Proctor 51 The Abeolute Capacity of a Con- denser 5S Reviews 66 The Face of the Sky. By F.R.A.S. 58 Design for Parlour Organ. {lUn-i.) i>8 Miscellanea 6S Correspondence 60 Our Mathematical Column 62 Our Chess Column 64 OTHER WORLDS THAN OUES. A WEEK'S COXYEHSATION OX THE PLUIiALIlY OF WORLDS. By Moxs. de Fostexelle, WITH SOTES BY RICHARD A, PROCTOR. To MoxsiEVR L. TO give you, Sir, a particular account how I pass'd my time in the country with the Marchioness of G . . . . , would amount to a volume ; and what is worse, a volume of philosophy. I know you expected entevtain- ment.s of other kinds, such as dancing, gaming, hunting, &c. Instead of which, you must take up with vortex's, planets, and new worlds ; these were the subject of our conversition. And by good luck, as you are a philosopher, it will be no great disappointment to you, but on the con- trary, I fancy, you will be pleas'd, that I have brought over the Marchioness to our party ; we could not have gain'd a more considerable person, for youth and beauty are ever inestimable : If wisdom would appear with success to man- kind, do you think she would do well to take upon her the person of the Countess^ And yet was her company but half so agreeable, all the world would run mad after ■wisdom. But tho' I tell you all the discourse I had with the lady, you must not expect miracles from me. It is impossible, without her wit, to express what she said, in the same manner she spake it : For my part, I think her very learned, from the great disposition she has to learning. It is not poring upon books alone that makes a man of understanding. I know many that have done nothing else, and yet I fancy are not one tittle the wiser. But per- haps you expect, befure I enter upon my subject, I should describe the lady's house, with its situation, E is called " the angle of deviation," and the greater the angle between the sides of our prism, or the greater the refracting power of the material it is composed of, the greater will this angle of deviation become. Note here particularly that in whatever position we place the prism, the emergent ray, p E, will deviate towards the thicker part, or base, of the prism B C. Now, everybody knows what a convex or magnifying-glass is, and if we suppose Fig. 19 to represent a section of such a glass, we shall see that, in effect, it consists of two prism?, ABC, D B C, placed base to base, and that parallel rays, R R R, &c., from a distant object will be so bent as all to unite at F, the principal focus of the lens, when they will form an image of the object, just as in the case of the concave mirror whose action was described and illustrated on p. 436. And here, again, we have an illustration of that law which can never be too often insisted on — viz., that rays of light go and return by the same route, for if we place a very small bright light at F, the rays diverging from it will be rendered parallel by the lens, and emerge in that condition on the other side of it. Suppose, though, that we remove our light to a point outside of the principal focus of the lens, then, instead of the rays issuing from its distal face being parallel, it will be seen that they will be convergent ; in fact, an image of the source of light will be formed on a screen held at a suitable distance on the other side of the lens. Conversely, if the light be shifted to the position occupied by tlie screen, its image will be formed at the point which it occupied before such shifting. These interchangeable points are called the " conjugate foci " of a lens. All this may be compared with the pro- perties of a concave mirror explained on p. 436. It ia evident that, if we obtain a lens whose focal length equals the width of the room shown in Fig. 2 (p. 306), and put this in the place of the simple hole in our shutter, we shall obtain a much more brilliant and distinct image of the external landscape on the wall ; in fact, we shall have con- structed a primitive form of the camera obscura. The form the camera takes, as arranged for public exhibition, is shown in Fig. 20. Fig. 20. Here we have a light-tight room, R, usually of octagonal or cylindrical shape, containing a table T covered with plaster of Paris or painted with dead-flat white paint. Above is a box turning in a ring containing the convex lens L placed vertically, and behind it the mirror M at an angle of 4.5°, the effect of this :\rrangement obviously being that the image formed by the lens is reflected down on to the table T, where the spectator sees a charming miniature view of the external landscape, with its drifting clouds, running water, and moving forms of animal life. One of the most familiar uses of a convex lens is that illustrated in Fig. 21. July 18, 1884.] ♦ KNOVs^LEDGE ♦ 47 We mean as a magnifying glass. Here the object (suppose a tiny arrow) k w is placed just wimin the principal focua of the lens, and the rays from it being cdusid to converge to the eye at E seem to come troiu a much larger arrow A W. The image thus perceived is, of course, a virtual one only, as contradistinguished from the real image formed by the camera obscura, as just described. It is needless to discuss tlie passage of light through a concave lens here, as we are not writing a treatise on optics. It may suffice to say that, mutatis mutandis, its action is comparable with that of a convex mirror (p. 437) — i.e., it renders rajs of light passing through it more divergent, just as is the action of a convex lens with the effect produced by a con- cave mirror, in causing them to converge more. A convex lens, too, fulfils another function — that of grasping a number of raysofliglit, which varies as the square of its aperture. A "burning-glass" illustrates this property admirably. Let us suppose that we have a convex lens of 3 in. in diameter and of 6 in. focus. Then the image of the sun formed in that focus will be only 00558 in. in diameter. But this image is formed by all the rays incident on the 3-inch aperture of the lens ; and, as we know that the area of circles vary as the squares of their diameters, we have only to divide 3- by 0-0558" to see at once how relatively enor- mous must be the concentration of light and its concomitant heat in the sun's image projected by a lens of our assumed size and focus. When such a lens is made of sufficient dimensions, its effect is astounding. Parker constructed a flint lens of 32 in. in diameter, of 6 ft. S iu. focus ; using together with it a second one of 13 in. diameter and 29 in. focus to further concentrate the converging rays. These lenses were so arranged that their combined focal length was 5 ft. 3 in. With this combination, 10 grains of slate were melted in 2 sec, and 10 grains of pure platinum in 3 sec. Nay, even so utterly refractory a substance as rottenstone disappeared in vapour in 1 min. 20 sec. under the inconceivable intensity of the heat thus generated ! Similar experiments were made a few years ago with a lens built up of segments, at the Crystal Palace, under which a halfpenny was vaporised in a comparatively few seconds. {To be continued.) ELECTRO-PLATING. VIII. By W. Slingo. AS was intimated a fortnight since, a deposit of copper, if it is allowed to assume any considerable thick- ness, loses very materially in definition, so far, that is, as concerns the outer or exposed surface. Although the deposit may often, under the most advantageous circum- stances, be made to retain the general features and beauties of the mould, such a result must not be habitually looked for ; but where plating is preferable to typing, the necessity for allowing only a tliiu deposit must not be overlooked. It is far better, where a good and substantial deposit is required, to obtain a type. Even, however, were it other- wise, the mere jiroduction is in itself interesting and in- structive, and is certainly a stepping-stone to higher and better achievements. It is in the nature of things that casts should be more or less undercut, and as it is my purpose here to deal with the problem of copying models in high relief, it will pro- balily be better for us to concentrate our attention upon sou:e particular form. Let us imagine that we desire a representation in copper of a small bust or statue, classical or otherwise. Now, it will be apparent on the briefest reflection that such a model cannot be copied in plaster or any other of the rigid materials used in making moulds from comparatively flat models such as coins or medals. Were our model a metal bust we could, of course, take a copy of it by enveloping it in a bath of wax or some other acid-proof substance, and then dissolve out the metal by means of acid, but that plan would rarely be desirable, more particularly if the metal were valuable, or of an obstinate nature, requiting nitric acid to dissolve it. A better way, by far, is to use what is known as an elastic mould. A brief reference was made to such a mate- rial in the fifth of this series of articles (Knowledge, No. 134). It was there said that such a mould could be made from glue and treacle. If the figure to be copied is smEill, two pounds of the finest glue is broken up into small pieces and soaked in cold water until it becomes quite soft. Any water that remains unabsorbed is poured off, and the gelatinous mass is then placed in a glue-pot with half-a- pound of treacle, and heated to nearly 100' C. (boiling point of water). To comply with this does not, of course, require a thermometer. A glue-pot, properly speaking, consists of two pots, one inside the other, the inner one containing the glue and the outer one containing water. The two so fitted are placed on the fire, and, as doubtless most people are aware, the most intense fire is incapable of raising the glue to a higher temperature than that of the water through which the heat is transmitted, and that water, as water, cannot, above the sea-level, be raised to a higher tempera- ture than 100° C. (or 212° F.), any heat passing into the water after such a temperature has been attained being absorbed in the conversion of the water into steam. So long, then, as there is water in the outer vessel, the tem- perature of the inner one cannot exceed the boiling-point of water. The mixture of glue and treacle during the process of heating should be thoroughly stirred, so as to ensure a uniform resultant compound. An ounce or so of beeswax may be added with advantage. Supposing, now, that the bust or figure to be copied is made of plaster, its surface must manifestly be well pre- pared so as to make it non-porous, otherwise the mixture will get into the interstices and render it impossible to eflfect a separation. The plaster, therefore, should be stood or laid in a shallow di.sh containing oil and thoroughly satu- rated. If a metal or other " solid " model, it requires well oiling to prevent the mixture adhering to it. A vessel, such as a jar, or a pail if the figure is a large one, is then procured and its interior well oiled. Presuming the model to be hollow, it is filled with sand, in order to increase its weight. It is then placed head downwards in the jar, a mark being made on the outside to indicate the position of the back of the figure. The mixture being warm, is then poured in, but not too rapidly to prevent the escape of any air bubbles that might collect in one or other of the various crevices of 48 ♦ KNOWLEDGE [July 18, 1884. the figure. The jar is filled up to an inch or two above the figure. Thus filled, the jar is placed aside for a couple of days or so, until, in fact, the mi.xture is thoroughly set. The jar is then turned upside down, and a tap or two releases the mixture from the sides of the jar, that is unless the shape is an unusual one, preventing the mould from slipping out. It is scarcely necessary to say that the best form of vessel is one that tapers slightly towards the bottam. The position of the back of the model being known (by the mark placed on the outside of the jar), a clean, thin sharp knife is inserted in the mould over the head of the model, and passed down its back, keeping close to the figure. The mixture which has cooled over the base of the model is also carefully removed. The mould, being highly elastic, may then be opened with the hands, and another pair of hands being called into requisition, the model may be removed. The mould, in virtue of its elasticity, springs back on being released, and we thus obtain a good negative representation of the figure. We may, if we so please, take our copy from this mould, but the task is rather a trouljlesome one, and the result often disappointing. The admixture of treacle with the glue prevents the shrinking which would otherwise take place on cooling, but it does not overcome the tendency to absorb water. Such an absorption would matter little were it not that it produces a considerable swelling, when the proportions of the figure would be entiiely lost. Nor would our troubles end here. The absorption may, however, be prevented by adding to the hot mixture of glue and treacle a small quantity of tannic acid to the extent of two per cent, of the quantity of glue when cold. Another modeof excluding water is to immerse the elastic mould in a weak solution of bichro- mate of potash and allow it to dry in the sun. A thin im- pervious film is thereby deposited. A good waterproof coating is that previously referred to as guttapercha varnish, made by dissolving the percha in bisulphide of carbon. This, ob\'iously, must not be applied to the interior of the mould, or we should get no deposit. The inner surface may, however, be well pi-otected by a thoroughly good coating of plumbago, which must be deposited, as facilities do not present themselves for rubbing the blacklead in. Of this, however, more anon. The mode of procuring the deposit must also be deferred for a few minutes. Whether the elastic mould is or is not used to receive the copper deposit, it should be bandaged up so as to prevent it falling out of form, as its elasticity would otherwise cause it to. When the deposit is not intended to be taken in the elastic mould, it may be placed back in the vessel in which it was moulded. A second mixture is then made by melting together 2 lb. of beeswax, 1 J lb. of resin, and a j lb. of tallow. During the heating the materials require to be well stirred so as to ensure an intimate mixture. The vessel containing the mixture should then be placed on one side for a short time, until it has nearly set. It is then poured gently into the cavity in the elastic mould until it is filled up. The jar thus filled is put aside for some hours until everything is quite cool, when it is inverted, and the elastic mould with the beeswax mould inside it slips out. The former may be again opened, and the latter withdrawn. Had the beeswax been poured in when warm it would most probably have melted, and maybe have united with the treacle mixture, and so have spoiled it. The beeswax mould thus obtained is obviously a copy of the model, and can hardly be used to ■obtain an electrotyped copy direct. It is, however, placed in the jar in a position akin to that occupied by the original (Sgure. A thin plaster of Paris paste is next prepared and poured steadily into the jar up to the level of the base of the mould. When the plaster is thoroughly dry, the bees- wax copy is melted out, and we have thus a plaster of Paris negative. It is evident that such a mould cannot have plumbago rubbed over its internal surface. To get a conducting sur- face the cavity is washed out two or three times with a solution composed of 32 grains of phosphorus to 480 grains (l^oz.) of bisulphide of carbon. After this it is washed- out with a solution of silver nitrate, one pennyweight of the nitrate being dissolved in a pint of distilled water. The plaster mould being prepared, it is placed in the bath, or it may, for the matter of that, form its own bath. The ca\-ity is filled with the bhie-stone solution, and, the conducting surface being conuected with the zinc pole of the battery, the copper pole is connected to the anode, which should consist of a mass of copper as near the general proportions of the figure as possible. It has previously been pointed out that a great deal depends upon the resistance in the bath, that is to say upon the relative distance between the anode and the mould. It is almost impossible to emphasise too strongly the necessity that really exists for keeping the anode as nearly parallel as possible with the various parts of the mould. When the substance to be coated is cylindrical, it is almost enveloped by two bent sheets of copper. When the mould is full of irregularities, it is placed at a consider- able distance from the anode so that the relative differences of resistance are reduced to a minimum. The resistance introduced by increasing the distance is compensated for by the addition of another cell, that is to say, by increasing the electro-motive force. Where there are a few cavities, the deposit is sometimes started in them first by using a small anode, and placing it in them. Another device is that of employing leading wires, as indicated a fortnight since. It is advisable, when coating a mould, such as the one in hand, to cause a current of the liquid to flow through it, otherwise the solution will degenerate. This is considerably facilitated by boring a small hole in the bottom of the mould, somewhere near or on the back of the head. Sometimes, more especially when the model is a large one, the mould is made in two, or perhaps a number of pieces. To make it in two, the model is embedded to half its depth in fine sand, the surrounding surface being made fairly level, two or more pegs are stuck in the sand, and then, a little thin plaster having been brushed rapidly into the crevices, a quantity of plaster is poured on. When it has set it is removed with the model. The level surface of the sand being spread over with oil, the reverse side of the model is moulded in a manner similar to that adopted with the first half. The plaster is then placed in a shallow tray containing stearine until it is well saturated, when it is taken out and thoroughly and carefully plumbagoed. The electrotype is taken in halves, and when both halves have attained a sufticient thickness they are trimmed, and the edges soldered together, the joint being carefully bronzed over. This process, however, cannot be adopted where there is any considerable undercut, such as would be met with, for example, in taking a copy of a figure recumbent on a base. The number of pieces would then have to be more numerous, unless the elastic mould process were resorted to. Very large objects are generally sacrificed, but of this more in my next. The Gas Company at Leipzig intends, says a contemporary, to ask the Mnnicipal Council of that town for a concession for lighting the streets and houses bv electric light. July 18, 1884.] ♦ KNOWLEDGE ♦ 4» THE ENTOMOLOGY OF A POND. By E. a. Butler. THE MIDDLE DEPTHS {continued). ABOUT a month after the hatching of the eggs, it is time for this aquatic life to close, and an existence less cross and far more ethereal now lies before the little creature, which has, however, by this time nearly completed the cycle of its mortal life, and so has but scant oppor- tunity left to enjoy the greater freedom and pleasures which the acquisition of superior powers will bring. Within that ugly, limbless pupa case has been formed a delicate, long-legged, feathery-horned, two-winged, sylph- like being, which, like the Prince iu the old story of " Beauty and the Beast," is but waiting the removal of its hideous disguise to appear in all its rightful elegance and grace. The moment of deliverance having at length arrived, the pupa tail is brought up level with the surface, a considerable part of the thorax being thereby caused to rise above the water. The skin then splits between the two horns, and the imprisoned fly begins to emerge at the opening. This is the most critical moment in its whole career, for with head and thorax released, but legs still encumbered by their encasement, the creature is perfectly helpless and, at the same time, rather top-heavy, so that a sudden gust of ■wind may in a moment capsize the tiny boat and dis- appoint the hopes of the half-liberated fly, which can then look forward to nothing but a miserable death by drown- ing. If, however, no such mishap occurs, the struggling insect gradually drags out first one pair of legs and then another, and then, leaning forward, rests them on the water and draws out the third pair : then making use of the empty pupa skin as a sort of canoe, it soon dries its wings and mounts aloft to join its companions, who every- where around are at the same time putting on their adult costume. In their society we will leave it for the present, hoping to meet it again later on. The larva' of the midges are called bloodworms, and are probably familiar to everyone who has kept a rain-water butt, for such receptacles often swarm with the wriggling, blood-red, worm-like things. They are also abxmdant in ponds, and, indeed, in any stag- nant water. The remarks made above concerning the life- history of the gnat apply in great measure to the present insects also. These red, worm-like things, however, must not be confounded with a certain red worm that also inhabits fresh water, forming vertical burrows in the mud of rivers ; they are gregarious, and crowd their tiny burrows close together, remaining with their bodies partly protruded, and thus forming large red patches upon the mud, and it is amusing to see the sudden disappearance of such a patch as they all sharply retreat into their holes on the approach of an intruder. These, however, are not insects at all, but true worms, or, as they are called in scientific language, annelids, and have reached, in this vermiform condition, the highest stage in their develop- ment. The fly, which is the parent of the red wrigglers of the water-butt and stagnant pond, is called Chironomus plumosus. The larva is rather more worm-like than that of the common gnat, and the pupa carries some elegant plumes of tine hairs on its ungainly thorax. There is a beautiful little creature, clear and transparent as crystal, that is the larva of another member of this group, and is noteworthy for the variety of curious appendages it carries on the fore-part of its body. Imagine an animal with a pair of arm-like bodies consisting of a stem with long bristles at the end, and used to lash the water, then a stout bundle of hairs movable en masse, then a pair of little saws, then a kind of policeman's truncheon, with bunches of hairs at the end, also capable of swaying backwards and forwards, and then a pair of jaws and a set of bristles, and you wUl see at once that Corethra ]jIu micornis, as it is called, must have enough to do to manage properly all these contrivances. Such is its transparency, that it may easily elude observation tiU its wriggling, jerky motions Ijetray its presence. This same transparency, however, aS'ords wonderful facilities to the microscopist for the study of its internal anatomy and phy- siology, for, by aid of the microscope, all that is going on in its interior is made plainly visible. It is, of course, a distinct advantage to be able to study the action of an animal's internal organisation without interfering with the free action of its parts, or placing it under abnormal con- ditions, as there is thus less chance of mistaking for essential peculiarities accidental ones, such as might be in- duced by the altered circumstances. It is not to be wondered at, therefore, that this creature has become classic by having been made the subject of elaborate investigation by more than one observer; and, indeed, there are few more entrancing occupations to those who have a desire to search out the secrets of nature than to watch, hour after hour, under a good microscope, the varied actions and vital processes of this and other minutiae of animal life. It must not be ignored, however, that the very transparency of parts tends also to introduce a certain element of difiiculty into the investigation ; for where several organs overlie one another it is not always easy to trace their relative position, and it becomes neces- sary to examine the object from diflerent points of view before such a matter can be settled. Through the transparent skin of Corethra can be seen, first the whole of the digestive apparatus, forming a long tube of varying diameter, stretching almost from one end of the body to the other ; then, on one side of this (the mouth side) can be traced the greater part of the nerve system, looking like a long stiing, with knots tied in it at tolerably regular intervals. Where it approaches the mouth, how- ever, the string divides, und sending one branch on each side of the throat tube, terminates on the opposite side of the digestive tract in a double mass of nervous matter, which is all the representative of brain the poor creature possesses. Then all down the liack (to be traced with a little more difficulty, on account of its extreme transparency)' is the " dorsal vessel," as it is called, which is an insect's equivalent of a heart. Those who have kept silkworms- or other pale, smooth-skinned caterpillars, will probably have noticed this apparatus as a dark line running along the back just underneath the skin, and alternately contracting and expanding from behind forwards at the rate of from forty to fifty pulsations per minute ; in the jiresent insect the pulsations are not so rapid, being only about twelve per minute. Then there can be seen the numerous oblique bands of muscles by which it is enabled to efiect its wriggling movements, as well as those strips by which the motions of its various appendages are controlled. Again, at each of two places, one near the head, the other much farther down, will be noticed a pair of black bags, which are air-receptacles connected with the system of breath- ing-tubes distributed over the body ; the tracing of these latter, however, is, on account of their extreme minuteness- a matter of much more difiiculty. At the tail there are two tufts of feathery hairs, one at the end, the other at the side •. small though they are, the hairs are hollow, and connected at their base with the tracheal system, and, whatever other function they discharge, they evidently take part in that of respiration. All these aquatic fly larv.-e are more or less transparent, but we have chosen the present for more de- 50 ♦ KNOWLEDGE * fJiLY 18, 1884. tailed reference, because its supprior transparency renders it best adapted for microscopical investigation. Like the rest of its brethren, it is carnivorous, and its favourite dish seems to be the quaint little creatures called, from their spasmodic, jerky movements, water fleas, though they are not fleas at all, nor, indeed, even insects, but belong to the group of animals of which crabs, lobsters, and shrimps are the most familiar representatives. These specks of crea- tion, which are considerably more minute than our house- hold fleas, are caught and crunched V)y Corethra in con- siderable numbers, and with great avidity. To facilitate the crushing of their hard horny skin, it is furnished with a pair of strong jaws, carrying stout, tooth-like projections. (To be continued). SUPERSTITION. IT is noteworthy how closely superstition and ignorance are allied. The dynamiters have shown us what a low and ignorant class of savages still exists in Ireland, and beyond a doubt most of the trouble which exists in Ireland, and is caused by the Irish lower classes wherever they make their abode, arises from the sheer ignorance of the race. There is no country in Europe, perhaps, unless it be in the more murderous parts of Italy, where superstitions of the stupidest sort are more prevalent than in Ireland among the ignorant members of the community. Con- sider, for instance, the edifying scene presented at a spot about 100 yards from the place where the Dublin Inviu- cibles were hanged. Here is a well called theWell of St. John, the foulness of whose waters, though to the eye they seem tolerably clear, has caused medicinal properties to be imputed to them, after the customary notion of the ignorant that the effectiveness of medicines is propor- tional to their loathsomeness of taste or smell, or both. But (probably because these waters become particularly offensive at midsummer) the ignorant of that region regard the water of this well as especially curative if taken thence on the eve of June 24, now St. John's day, though the tradition dates unquestionably from times long preceding the Christian era. This silly sujier- stition (amazingly silly in this age) is so firmly believed in by the ignorant, and there are so many ignorant folk round about Kilmainham, that, on June 23 last, quite 5,000 people assembled at the well, having made a pilgrimage thither from greater or less distances. It is regarded by these unfortunate idiots as essential that the water should lie drawn before daylight on St. John's eve, and the pilgrims oame provided with every class of vessel to bring away the precious fluid (precious stuflT). The well is in a recess under a wall, we are tuld, and candles had to be used to light the people down the steps, so that the scene presented was of a weird character. I have seen such iveird scenes, and most melancholy they are. Watch a detachment of the Salvation Army going along with the savage and silly noises in which they delight and note the degraded type of countenance of every single member of the procession. Imagine 5,000 persons of still stupidier and more animal type groping about with candles to gather foul water in dirty vessels, mumbling unmeaning incantations to strengthen its virtue — a scene weird enough for a Rembrandt to paint ; only, if he would not make it too utterly mslancholy for all who long to see the human race becoming better and wiser, he should let gloom and darkness hide all the worst features of the scene. Truly, a man must keep such scenes from his thoughts, even as lit must refrain from thinking of the squalor of our ill-fed and worse clothed poor, if he would believe that man is but a little lower than the angels, or else he must have strange ideas of the angels. Thinking of the ways of some who are closely akin to these super- stitious and ignorant beings — I mean the dynamiters — he might well conclude that man is but a little higher than the devils, according to accepted ideas as to these folk. — R. A. Proctor, in the Newcastle Weekly Chronicle. THE INTERNATIONAL EXHIBITION. HEALTH VIII.— WATEE AND WATER-SUPPLIES— (conKntMd). A RETROSPECTIVE inquiry into the statements made in our last communication would show that it is chiefly by the action of carbonic acid gas, oxygen, organic matter, and hydration, that water is enabled to act upon the substratum of our earth. By means of these reactions it is endowed with properties which it would otherwise never possess, and a little reflection would convince one that those attributes are wholly dependent upon the charac- ter of the formations through which it penetrates. Let us now proceed to trace the physical history of the water which saturates the earth's crust, and which is destined to play a most important part in the laboratory of Nature ; in doing so we shall be able to unravel the mysteries of the Plutonic region, and gain an insight into the principles which we shall have to bear in mind when we come to consider the practical aspect of the water question in its relation to man. The dry bones of natural philosophy are capable of being rendered highly delectable when the results of abstruse calculations are reduced to round numbers and put forth as astounding realities ; at least, so they seemed to us in our college days, when the learned professor laid aside the garb of austerity to discourse upon the wonders of the " unseen universe," and material creation, to his awe-stricken class of undergraduates. We were taught that in the far-off hazy annals of the world, at a time which is only so far definite as to allow of a licence of computation between twenty to forty millions of years ago, the earth was in the condition of the sun of our present era, and that through the radiation of the heat into space, it hlowly cooled down to become fitted for the habitation of living things. (On the authority of our University pedagogue, we may state that sufficient heat leaves the earth per annum to melt a film of ice one quarter of an inch thick, spread over its entire surface). It does not much matter to us whether that happy time was consummated six millions, or only six thousands of years ago ; suffice it to say that the only evidences we have of the former intense heat of the earth now are to be traced to the vestiges of internal temperature, which we are made aware of in our comparatively trivial borings, which show a rise of about PC. for every 100 feet of descent into a mine, and to those natural operations which manifest themselves in volcanic outbursts, fiery lakes, and thermal springs. The late Principal Forbes has shown that irrespective of the nature of the soil, the changes of tem- perature due to the rotation of the earth upon its axis, or that caused by day and night, is onl}- perceptible to a depth of one foot ; and that the seasons do not afl^ect the earth's crust, as far as temperature is concerned, to a greater deptk than from 28 to 30 feet. Water which penetrates into the earth, then, has to con- tend against tli'jso thermal sources ; by them it is endowed with solvent and other propertie.s, in addition to those July 18, 1884»] ♦ KNOWLEDGE ♦ 51 which it possesses as a chemical reagent. The densest rock and the stiftest clay are yet so porous as to give it ready access, and so great is the power of capillarity, in virtue of which it descends, that DaubrcJe's experiments* have proved concluNively that it is able to resist the great ettects of counter pressure of vapour and internal heat, and to establish itself in the form of a gas at the roots of volcanoes and far down in the depths of the earth ; liow far has not yet been ascertained. But, although stiff clays are permeable, they may be regarded as practically impervious ; they are only stiff clays because they hold, in intimate admixture, a large proportion of water. Suppose, then, that a stratum of clay aup})orts a sandy porous soil as at Fig IT), which represents ■the condition of things which obtain at Ilampstead Heath. The major portion of the rain-water is filtered by the sand, somewhat concave, or, it may be, altogether irregular on account of the differences of the rock textures through which the water is forced to pass, or because of their un- conformability. A boring sucli as that shown at v, Fig. 1 6, is called a well ; since t and c are at higher levels than ?'•, the water, in virtue of the law of hydrostatics, rises up the bore of the well to its outlet, and forms the kind of artificial spring called an Artesian well.* Thus far we have only taken into account springs and wells such as obtain in comparatively unbroken strata. In other regions, however, where seismic action has been rife, where numerous faults intersect the country, and where the rocks lie more or less out of their strict order of suc- cession, springs are to be soui^'ht for chiefly at escarpments and in the lino of faults. In Fig. 17 the water-bearing strata are shown in shaded bands, whilst the sandy beds are doited ; /,/, are the outlets of powerful springs which rise up the fissures due to faults. Fig. 15. — B., Bapshot eand ; I., water-beariog stratum; L., London clay ; s., spring ; ii'., well. and collects above the clay in a sort of water-bed. At certain parts the clay is laid bare by a cessation of the overlying sand, l>y a natural depression, as at s (Fig. 15), or by an artificial boring as at lo (Fig. 1.5) ; s gives forth a natural spring, v is called a well. Now, remove all the Bagshot clay and lay bare the London clay, as at Fig. 16, which depicts an hypothetical section across the London basin. The sandy strata, known as the Lower London Tertiaries, underlie the clay, and the whole rests upon the uppermost beds of the mesozoic age, termed the cretaceous or chalk formations. The London clay takes Fig. 16. — Hypothetical section across the London basin. L. London clay ; t., porous strata of the Lower London Tertiaries ; c, chalk; I., water-level; tc, well. in but little water ; the exposed surface of the sandy ter- tiaries at i and the chalk at c are saturated, and the water finds its way through both until it reaches the so-called water level (indicated by the dotted line in Fig. 16), or underground reservoir, which pervades the crust of the earth irregularly, and at depths which vary with the nature of the siiil, the seasons, and the external configuration of the surface.! Thus, under a plain, it is in reality toler- ably level ; beneath a hill it becomes convex ; in a valley * " Geologie Experimentale," p. 274; Tschermak, "Sitz. der Wiener Akademie," March, 1877; Reyer, " Beitr. zur Physik. der Eruptionen," § 1. + In the case of chalk formations, the surface waters which are absorbed by the upper strata find their way by capillary percolation and through fissures into the deeper portions, which then become saturated and simulate retentive clays. It is in this way that water- bearing strata are extemporised in chalk, and, as one would expect, they are often transitory. Fig. 17.—/,/, Powerful springs rising at faults; s, porous sandy beds; w, water-bearing strata. Thus it appears that the rain-water which penetrates the earth is not permanently removed from the surface, but rises again to well forth as springs, along joints and fissures, charged with substances in solution and suspension which are characteristic of the formations through which it passes. Some of the water, however, is absorbed, and other portions combine chemically with certain constituents in the rocks. Its underground course, moreover, is not confined to capillary percolation, but often assumes the character of subterranean streams and reservoirs,! which are the ex- teuded representatives of former crevices and fissures. These are so pronounced in some cases as to materially affect the water-supply of rivers— to drain or to swell them ; curious facts illustrative of this have been recorded by Desor,* and the occasional presence of plant-stems, leaves, and even of fish, in recently-made Artesian springs, are additional and interesting proofs of the underground circu- lation of water. The descent of rain-water into the depths of the earth to regions of peculiar mineral salts, aud their subsequent rise in the form of springs, provides us with the so-called natural mineral waters, for a detailed account of which we must refer the reader to Gairdner's exhaustive " Memoir."§ In like manner, thermal springs are the result of heat derived from the interior of the earth. If we attribute the heat thus gained by the water to the greath depth of its origin, then, by allowing 1° Fahr. for every GO feet of descent, when the surface temperature is about 50° Fahr., the springs of Bath, which average 120° Fahr., ought to come from a depth of at least 4,200 feet. Let us now turn to a consideration of the London * So-called after the village of Artois, in France. t A paper on " The Underground Waters of England and Wales" was read before the Geologists' Association on June 6, last, by Mx. C. E. De Ranee. X "Bull. Soc. Sci. Nat.," Neufchatel, 1864. § " Essay on the Nature, History, Drigin, and Medicinal Effect* of Mineral and Thermal Springs," Edinburgh, 1832. 52 ♦ KNOWLEDGE ♦ [Jdly 18, 1884. water supply as an example of special interest to the in- habitants of this vast metropolitan centre. The eight water companies, whose graceful pavilion in the Exhibition we shall visit ere long, derive their water almost wholly from the Thames district. Five of them draw upon the Thames and its tributaries directly, two have recourse to the river Lea, whilst the Kent company resort to deep wells in the chalk for its supply. The sixth report of the Rivers' Pollution Commissioners states that the " catchment basin " of the Thames is one of the finest which has ever come under their notice. Of an area of 6,000 square miles, more than one-half consists of cultivated porous soil, its yield of water being delivered chiefly through springs. The remaining impervious super- ficial strata consist chiefly of meadow and pasture lands, and from them the rain-water drains ofl' into the runnels which feed the river and its tributaries. The extreme western tributary of the Thames, called the Churn, arises in the " Seven Springs," situated about four miles from Cheltenham, on .the road to Cirencester. These springs rise from the clay beds of the Lias, the water having accumulated through the porous formations of the inferior oolitic limestones, which contain large underground reser- voirs ; they yield about 1.50,000 gallons of water daily. About four million gallons of water, which have passed through similar formations, are derived daily from the Syreford spring, at the head of the river Colne. Three million gallons are daily pumped up at the Thames' head, from a depth of 33 feet, to the level of the Thames and Severn canal ; this water passes through the lower oolitic formations, known as the Bath or the Great Oolite, to be stored by the marls and clays of the so-called beds of the Fuller's earth. Other springs of importance which originate in the Fuller's earth are those of Boxwell, Ewen, and Ampney. Minor tributaries of the Thames derive their supply from the Gault clays, which underlie the beds of the Upper Greensand, the jiorous collecting-ground of which consists of siliceous and calcareous sands, with green grains and chert nodules. With the exception of the river Loddon, which is supplied from the Bagshot sands resting on the London clay, nearly all the rest of the water of the Thames is derived from the chalk formations. Of this character are the supplies of the Kennet, wliich culls its waters from the downs near Marlborough and Hungerford, the Colne, and the so-called New River. In addition to all these sources, the Thames is largely fed by springs which arise in its own bed, the most famous examples of which are situated between Reading and Wallingford. From what has been stated it may be gathered that the water of the Thames is essentially a calcareous water, all its chief sources of supply being derived from limestones and calcareous sands, witb the single exception of the river Loddon, wliich flows through the ferruginous and other sands of the Bagshot series. The Kent Company's water, which is obtained from deep chalk wells, is even more calcareous than the Thames water ; so that we may here make the general statement that the most characteristic feature of the London water is its hardness. The class of workmen who have been actively employed in rail- road construction for the last few years have probably, suffered more from want of work than other classes (in America) during the comparative quiet that has lately existed in many industries. This has been especially the case with Italians and other foreigners who came to the country in large numbers during the flush labour times, but are now in large numbers without employment in Chicago and other large cities. Their want of knowledge of any other labour but railroad work tells against them. — Railway Review. (Chicago). BEITISH SEASIDE RESOETS, FROM AX UXCONVEN'ilOXAL POINT OF VIEW. By Percy Russell. I. IT was the favourite idea of the author of the " History of Civilisation " — that imposicg fragment of a grand conception — that a people would correspond psychologically to the nature of their immediate physical environment. The idea is in itself in no way new, and has been universally found to furnish the key to all the peculiarities of national temperament, and thence it may, I think — passing from the abstract to the concrete — be fairly assumed that the love of the sea in general will be found jiroportioned to the extent of coasts in any particular country, and very espe- cially in proportion to the sinuosities and general accessi- bility of the coast itself, while, of course, the question of average temperature and other meteorological conditions are necessarily important, and sometimes determining factor& in the creation of a general national fondness for "blue water." For one thing, it is diflicult for the average Eoglishmau to understand the utter indifterence of the mass of the inhabitants of Central Europe for the ocean in any of its aspects, and the njtion of a " seaside season," which is with ourselves a matter of course, would be an idea really impossible to convey adequately to the normal mind of a dweller in Central Europe. It may, perhaps, however, be news to some that the number of islands, great and small — many very small indeed — composing what is known as the group of the British Isles, exceeds five thousand. It is true, certainly, that many of these are mere shelves of rock, but still the fact remains that the geographical term, Great Britain and Islands, implies an archipelago of over five thovisand islands. Irre- spective, too, of the mass of the outlying islands, fi-om the Scilly group to the Orkney and Shetland Isles, the total length of the coast-line from Berwick to the South Foreland, thence to the Land's End, and from the Land's End to Berwick again, apjiroaches two thousand miles, taking bays, inlets, and harbours into account, and thus it is possible for the excursionists around our own shores to accomplish a distance equal to a fourth of the actual diameter of the entire globe ! These are very rudimentary facts indeed, but they escape many among us who are commonly reckoned, and probably justly so, as being well informed generally. They are, however, I think very suggestive facts, and, for one thing, unquestionably furnish the clue to the undoulitedly strong passion of Englishmen for the sea, which was, curiously enough, much more intense as a passion before the epoch of iron ships began. Whether or no our maritime character is becoming considerably modified by the various material influences and altered conditions of our present complex civilisation, it is not my business to inquire in this place, but it may be safely said that the normal Englishman, Englishwoman, and child are longing for the sea in summer, and directly the mercury rises in the thermometer to a certain point, that very large class known as the social " Everybody," begins to hasten coastwards, and the seaside season fairly sets in. It goes without saying that, as a general rule, English people are not remarkable for method or thought in their pleasures and recreative arrangements, and thence it is that, in general, comparatively a few water- ing-places are thronged and packed with visitors for a season, and a large proportion of people made very un- comfortable, and not a few exceedingly ill, simply because July 18, 1884.] ♦ KNOWLEDGE ♦ 63 the vast majority of heads of families deciding on a seaside holiday are led by names rather than things, and all flock off to comparatively a few places, -which most of them know a little better than their own neighbour- hoods, having had more leisure for the study ; and thus it follows that, to a great extent, the essential framework and normal conditions of town life are precipitated on tlie select and fashionable places of seaside resort, and a number of unsanitary conditions produced which ought never to exist, while the special pleasures which would be derived from the seaside, minus these conven- tional municipal features, are but rarely attained, and are even unknown to many who have, however, had the barren experience brought to them of very many annual seaside seasons. For one thing, the majority of persons are lamentably ignorant, I fear, as to the character of the coasts of their own country, beyond the few miles of it that they have actually seen at the very few watering- places they have visited. Thoy continue going, mechani- cally almost, to the same place, and thus continue to repro- duce in their recreative environments the very same viciously monotonous conditions which they are professedly seeking to escape when, with exhausted bodies and weary minds, they at last decide on a change. Many excellent and truly scientific* monographs now exist as to the thermal conditions and general meteorological aspect of the principal British coasts and surrounding seas, and any one desirous of such information can easily ascertain the exact character of the prevalent winds at any particular place, the chemical constituents of the air, and so forth. This, however, is the higher science of what may be called our seaside philosophy, and taking humbler and more easily practicable phases, I would first give a rapid sketch of the salient and picturesque features of the coasts of the British islands, and having noticed rapidly their principal picturesque features, I shall then proceed to give an outline, with all the needful practical particulars for guiding aright intending visitors, of sundry places of beauty and interest on our own coasts which are even now little known, and less frequented, by the mass of people as places of health-resort or recreative retirement. It is manifestly absurd for people to continue visiting the same places, or the same small group of familiar places, year after year, and then, as some do, proceed abroad on the plea that there is nothing fresh for them to see in their own country ! First, however, let me say a word as to the general features of the coasts of the United Kingdom. The western coast, broadly, then, is formed by four deep and very wide bays, divided by enormous buttresses of land thrust far out to sea. The scenery is wild and magnificent. Tremendous cliffs and masses of rocks fortify the shore, and generally tower above the sea with rugged, but grand, pro- files. These cliffs are mostly composed of exceedingly ancient and very hard rocks, and have for ages successfully resisted wind, frost, and even the insidious rain, and still present very much the same features seaward that they have done for the last two or three thousand years. As a natural effect of this formation we have here a very deep sea and remarkably powerful tides. Here, too, the waves may be studied in their might, and present an aspect under even a moderate gale which is altogether unlike anything ever to be seen on the south coast. On the east, in strong antithesis to the west, we find a rather monotonous coast, usually sloping away south-east, and having few or only comparatively unimportant head- lands and not much cliff. The bays, or rather their equiva- lents, are generally formed by rivers discharging into the * See " English Seaside Kesorts," Vol. II., pages 3, 18, 39, 91, 109, 102, 17C, 211, 306. sea, and such cliffs as exist are comparatively soft and continually wearing away. The outline of the coast here has been much modified by time and the sapping effects of the tides, although these last are generally gentler in both their ebb and flow, and century after century enormous quantities of material is accumulating off the coast, render- ing the ocean bed comparatively shallow. The southern coast, indeed, to some extent unites the characteristics both of the western and the eastern shores of these islands, and as we pass westward along the Channel the sea becomes deeper and its waves grow in magnitude until, at the Land's End, we find ourselves in view of verita'ile Atlantic billows. In truth, the whole of England, Wales, and, to some extent, Scotland, is an inclined plane, having its most elevated side on the west, and having there, too, its hardest rocks. Cardigan Bay is nearly useless for shipping, and generally speaking, with the exception of the Bristol Channel and the mouth of the Mersey, commerce is by no means the presiding genius of our great western coasts, where there may still be found innumerable beautiful nooks and unsurpassed vantages wherein to study the most picturesque aspects of the sea under unusually favourable conditions. Then, again, to revert to my original contention as to the capital and common blunder of recurring to a few familiar places only as seaside resorts year after year. While hundreds of thousands of regular seaside visitors know the Isle of Wight more or less thoroughly, how many are acquainted with the Seilly Islands, the Isle of Man, or, more interesting still, put up at the Isle of Anglesea, to say nothing of the Hebrides and other northern groups, which, when they are set for a brief period in summer seas, are in all senses places which repay the visitor a thousand- fold for the little extra trouble involved in getting thus far out of the beaten track 1 Then, again, while so many of us are familiar with Portsmouth Harbour, Southampton Water, and the very faint stretches of blue water off the south coast, how many, comparatively speaking, are fami- liar with the magnificent Bristol Channel, with Swansea Bay, Milford Haven, St. Bride's Bay, Morecambe Bay, and the splendid Solway Firth? How few, again, among the tens of thousands who throng the esplanades of the fashionable and popular south and east coast water- ing-places are acquainted with the formation of the Devonian heights which rear themselves in such stately beauty and culminate at last at a height of 1,700 feet, while on the north this lofty table-land falls grandly to the sea in precipitous cliffs'! Then there are the beau- tiful Cornish highlands, combining much of the romantic and stern beauty of North Britain with the softer graces and luxuriant vegetation of the sunny south. These re- markable hills, which commence on the lovely shores of Bideford Bay, contracting thence, form but a single line of remarkable heights — a kind of English Apennines — sloping abruptly to the sea on each side, and ending in the bold and splendid headland at the extremity of Cornwall, where may be studied the volcanic cliffs off Lizard Point, and where the Seilly Isles, far out at sea, remain mute but eloquent witnesses of the extent of this remarkable peninsula before some awful convulsion rent away its southern extremity and swallowed up what must have been in pre-historic times a kind of Italy attached to a group of islands, which seemed to some of the ancient Romans to be lost among the dreary snowstorms of the Ultima Thule. {To he continued.) As a protection against blow-fliea, the best thing is creosote. If placed in various positions near and around the meat, no fly will go near it. Pyroligueous acid has the same effect. 64 KNOWLEDGE ♦ [Jdlt 1^ 1884. Day Sign for the Month. ZODIACAL MAPS. By Richard A. Proctob. WE give this week both the day sign and the night sign for the month, one showing the zodiacal sign now high in the heavens at midnight, the other showing the region of the zodiac athwart which the sun pursues his course at this part of the year. THE ANTARCTIC REGIONS. By R. a. Proctor. (Contitmed from page 31.) THE enormous icebergs which come from out the Ant- arctic seas suggest interesting conclusions respecting regions as yet unexplored. This will be understood when it is remembered that all the larger and loftier icebergs have in reality had tbeir origin in immense glaciers. Vast masses of ice are formed, indeed, in the open sea. Each winter the seas which have been open during the summer months (December, January, and February) are covered over with ice of enormous thickness, and when summer returns the ice-fields ihus formed are broken up, and the fragments, borne a'jninst each other during storms, become piled into gigantic masses. But the agglomerations thus formed, vast though they are, are far exceeded in magni- tude by the true icebergs. " Among the drifting masses of flat sea-ice," says Tyndall, " vaster masses sail which spring from a totally different source. These are the ice- bergs of the polar seas. They rise sometimes to an eleva- tion of hundreds of feet above the water, while the height of ice submerged is about seven times that seen above." " What is their origin 1 " he proceeds, speaking of those met with in the northern seas. " The Arctic glaciers^ From the mountains in the interior the indurated snows slide into the valleys, and fill them with ice. The glaciers- thus formed move, like the Swiss ones, incessantly down- wards. But the Arctic glaciere reach the sea, and enter it, often ploughing up its bottom into submarine moraines. Undermined by the lapping of the waves, and unable to- resist the strain imposed by their own weight, they break across, and discharge vast masses into the ocean. Some o£ these run aground on the adjacent shores, and often main- tain themselves for years. Others escape, to be finally dissolved in the warm waters of the ocean." It is important to notice that the Antarctic icebergs are- vaster and more numerous than those formed in Arctic seas. How large these last are will be understood from the instance referred to by Tyndall, who, citing Sir Leopold. MacCliutock, describes an Arctic iceberg 250 ft. high, and aground in 500 ft. of water. But Captain Maury speaks of Antarctic icebergs in the open sea, hundreds of feet high and " miles in extent." '" The belt of ocean that en- circles this globe on the polar side of fifty-five degrees south latitude is never free from icebergs," he adds ; " they are formed in all parts of it all the year round. I have en- countered them myself as high as the parallel of thirty- seven degrees, . . . and navigators on the voyage from the July IS. 1RP4.1 * KNOWLEDGE o5 CAQUILAJ rMa:iaai!Ml a. •?! 1«- A*^5^ '5%.M- l^. CAPRI=^ -~ *^ [SAGITTARIUS. Aso^ im ^Night Sign for t'ae Jlonih. Cape of Good Hope to Melbourne, and from Melbourne to Cape Horn, scarcely ever venture, except while passing Cape Horn, to go on the polar side of hfty-five degrees." As he justly remarks, "the nursery for the bergs to fill such a field must be an immense one ; such a nursery can- not be ' n the sea, for icebergs require to be fastened firmly to the shore until they attain full size. They, therefore, in their mute way, are loud with evidence in favour of Antarctic shorelines of great extent, of deep bays where they may be formed, and of lofty cliffs whence they may be launched." It is remarkable, however, that Maury fails to notice that the evidence of these enormous icebergs is opposed to the theory of an Antarctic continent, or is, at least, by no means in favour of that theory. It might at once be objected, indeed, to the inferences derived by Maury from the Antarctic icebergs, that similar reasoning would show the unknown parts of the Arctic regions to be mainly occupied by land masses. But, apart from this, all that we know of glaciers teaches us to recognise the fact that they are furmed only in regions where vast mountain ranges exist, and where the lower levels are reached by ravines ai d valleys gradually diminishing in slope as they descend. Nnw, wherever this is the contour of the land, we have in the surrounding regions one or other of the three following conditions : — Either (i. ), flat land regions around the base of the mountain ranges ; or (ii.), inland seas upon which the valleys debouch ; or (iii., and lastly), open sea, in which the mountain ranges form islands or pinnacles complicated in figure. It is clear that only'^the third of these formations corresponds to the conditions indicated by the Antarctic icebergs. There must be a communication between Antarctic seas and the mountain- slopes of Antarctic lands, and this ccmmunicaticn must be by long and deep vallejs, descendirg to fiords, baje, and sulfs. It is thus as certain as such a matter can be until CI the eye of man has actually rested on these regions, that the Antarctic shore."; are extremely irregular ; and it setms altogether more probable that the land-masses of Antarctic regions consist of a number of large islands like those in the seas to the north of America, than that there is a great continental region, broken along its border, like the Scandinavian peninsula, into bays and fiords. But, strangely enough. Captain Maury actually recog- nises the necessity for a suitable region within which the icebergs are to be formed, but seems to feel bound (by the opinion of geographers respecting the unknown Antarctic regions) to reconcile the existence of such a region with the theory of a great Antarctic continent. "Fiords, deep bays, and capacious gulfs loom up," he tells us, " before the imagination, reminding us to sa^k the question, Is there not embosomed in the Antarctic continent a Mediterranear , the shores of which are favourable to the growth and tht; launching of icebergs of tremendous size? and is not tie entrance to this sea near the meridian of Cape Horn, perhaps to the west of it ?" But the condition of the Ant- arctic seas will not permit us to adopt such a view of the origin of southern icebergs. Even if the imagined Antarctic 56 ♦ KNOWLEDGE ♦ [July 18, 1884, Mediterranean were not icebound, it would be sufficiently difficult to conceive that the glaciers formed around its shores would pass out in stately procession through the imagined straits south and west of Cape Horn. How should currents sufficiently strong be generated to bear these glacial masses away ? How could collisions, blocking up the mouth of the strait, often for months together, be avoided ? And when the consideration is added that an Antarctic Mediterranean would almost certainly be frozen over the whole year through, the theory that it is within such a sea that Antarctic glaciers are formed becomes, in our opinion, altogether untenable. If such a sea exists, it must be blocked up with ice too completely for any con- siderable movements to take place within it. Even the glaciers on its borders must be unlike the glaciers known to us, because the downward motion of the ice-masses composing them must be so checked by the resistance of masses already accumulated, as to be scarcely perceptible even in long periods of time. (To he continued.) THE ABSOLUTE CAPACITY OF A CONDENSER. AT the last meeting of the Physical Society, Mr. R. T. Glazebrook, M.A., F.R.S., of Cambridge University, described some interesting experiments he had made to determine, in absolute measure, the electrical capacity of a condenser sent to him for the purpose by Messrs. Latimer Clark, Muirhead, & Co., the well-known makers. The general method employed by Mr. Glazebrook is that given by Clerk Maxwell in his treatise on "Electricity," vol. II., sec. 776. A commutator driven by a tuning-fork is fitted to the condenser in such a manner that the plates of the ■condenser are alternately connected to two points at dif- ferent electrical potentials, and then put into communication with each other. The condenser and commutator are inserted as one of the arms of a Wheatstone bridge, and Maxwell has shown that if the period of vibration be sufficiently slow, the combination is approximately equivalent to a resistance of . — where n is the frequency of the tuning-fork, and C the capacity of the condenser. Thus, if a be the resistance of the arm conjugate to the con- denser, c and d resistances of two other conjugate arms, we have the condition for a balance — = c d, or w C =: ?iC — -. Thus C can be found if a, c, d, and n be known. Mr. c a, J. J. Thomson has, however, shown ("Phil. Trans.," part iii., 1883) that Maxwell's formula is only approximate, and has given the correct formula. It was this which Mr. Crlazebrook used in his tests, and the arrangement of apparatus is shown in the figure. The condenser and commutator were placed on the bridge arm B D, and P is the moving piece commutator, which, when in contact with S, changes the condenser, and, when in contact with R, discharges it. The tuning- forks used had frequencies of 16, .32, 64, and 128 to the second, as determined by careful comparison with a clock by the method of Lord Rayleigh. The corresponding values of the capacity were, in terms of the legal ohm., •3336 mf. (microfarads), -3340 mf., -3335 mf., and -3337 mf., the mean being 3337 microfarads. The experiments do not show any variation in the capacity, as the time of charging is changed from 1-1 6th to 1-1 28th of a second. The formula also gives a ready and accurate means of determing the pitch of a tuning-fork, for if the capacity of the condenser used is known, the value of n can be deter- mined. Mr. Glazebrook has successfully used it for this purpose. A question arose at the meeting as to the effi- cacy of mercury contacts in such experiments, and Dr. W. li. Stone stated that he found mercury and iron con- tacts to be free from sticking. Whether this is an advan- tage or not in making a good contact is doubtful. Recent experiments within our knowledge would seem to point to a microphone action in such contact?. — Enfjineerin'j. ^rfaiehig* SOME BOOKS ON OUR TABLK Picfure-maHnff by Photograjihy. By H. P. RoBixsON. (London : Piper & Carter. 1884.) — Many a photographer whose technical manipulation is perfect, whose plates never fog, and the half-tones of whose negatives leave nothing to be desired, fails dismally in the production of anything re- sembling an ariistic picture. That it will not merely suffice to that end to stick up a camera in front of a view or group, and subsequently to expose and develop a plate, Mr. Robinson's excellent manual not only conclusively shows, but points out definitely why, in the plainest and most compre- hensilile manner. His little book should be in the hands of every one who is anxious to preserve the element of beauty in his reproductions of nature, and is not contented with a mere wooden and mechanical copy of the objects he depicts by the aid of the camera. The London Water Supply, its Past, Present, and Future. By G. Phillips Bevan, F.S.S. (London : Edward Stan- ford. 1884.) — Beginning with an account of the water supply of mediaeval London from the Thames, the Fleet, the Ty bourne, the Wallbrook, ic, Mr. Bevan carries us down to the existing provision for the metropolis, and gives full details with reference to the various water companies to which we are indebted for it, their plant, sources of supply, and profits ; concluding his book with an account of the various schemes which have been devised for a large increase in the amount of water to be furnished, by bringing it from distant sources, such as Wales and Cumberland. Considering how probably imminent legislation is on the subject of the water supply of London, and how vastly its 4,000,000 inhabitants are interested in the question of the purity and economy of such supply, Mr. Bevan's small work should address a very large public indeed. 2Vie A B C Guide to Physical GfoyrapJii/. (London : Thomas Young, 1884.) — The leading physical features of the earth's surface are set forth in this little book in a way calculated to give a fair rudimentary idea of them. After two perusals of it, we have come to the conclusion that the author means to be funny ; but we speak with some hesi- tation on this point. Gas-Burners, Old and Nev3. By Owen Merrimak. (London: Walter King. 1884.) Mr. Merriman gives us a complete history and description of gas-burners, from Murdock's original crude nipple, with its three perforations, through the bat's-wing and fish-tail forms down to the highly complicated and elaborate ones devised by Siemens, Clamond, and others ; and the more simple, but practically equally efficient, burners of Sugg, Bray, and Bronner. The work before us may well tend to dissipate a good deal of unreasoning prejudice against gas-lighting, and to indi- cate how — at all events for domestic purposes — it will hold its own against the electric light for many a long day yet. July 18, 1884.] ♦ KNOWLEDGE ♦ 67 Vivisection in its Scientific, Eeligio%is, and Moral Aspects. By E. D. GiRDLESTONE, B.A. (London : Simpkin, Mar- shall, it Co. 1884.) The Utility and Morality of Vivisec- tion. By G. Gore, LL.D., F.R.S. (London : J. W. Kolckmann. 1884.) — We have classed these two pam- phlets together, inasmuch as they have one common aim : to plead for our right t3 experiment (of course under due restrictions) on the lower animals, for the benefit of man- kind. Any impartial jiersou who will read these brochures through with the attention that they deserve, will be able to estimate at its true worth the cant of those who ride and drive horses which have been subjected to a mo=t painful form of " vivisection " (as probably as not by au ignorant country farrier), who eat veal that has been slowly bled to death, who will leave a pheasant with its thigh shattered by shot to die in a ditch, but who shriek with horror if a frog is decapitated, or the larynx of a dog opened, to obtain knowledge that may benefit thousands of suffering human beings. Vaccination, by Alexander Wheeler. (London : E. W. Allen. 1883.) — More anti-vaccination juggling with statistics ! Mr. Wheeler gets hold of one table of mortality and finds that ten years of least small-pox had more deaths than ten years of most small-pox ; and then of another, showing that ten years of most small-pox had more deaths than ten years of least small-pox ; but the}- all (according to him) prove the same thing I We all remember how Bret Harte took tlie number of people who were annually killed on railways and the number of those who died in their beds, showing conclusively that it was almost indefi- nitely safer to travel by rail than to go to bed. The anti- vaccinationists appear to us to deal with their statistics on a strictly cognate principle. Solar FJiysics. An Alnianack of the Christian Era, &c. By A. H. SwixTOX. (London : W. H. Allen i Co. 1883.) — After wearily wading through this curious muddle of science and non-science (or, more shortly, nonsense) in its gorgeous cover, whereon a sun like a gilt crumpet reposes on an azure ground, we found that it concluded with a " list of subscribers." This, at all events, sufficed to explain the otherwise incomprehensible fact of its ever having been published at all. Our idea, gathered from its perusal, is that the author is a perfectly sincere and conscientious fanatic, who has been patted on the back by what has been not too politely called " the sunspot ring," in this country, for the sake of the respectability shed upon their professed views by their proclamation by a disinterested person. At all events, he quotes from a contribution of his own to the organ devoted to the pecuniary advancement of the gently referred to. But he really ought to be right in his facts. To begin at the beginning, he sets down 1882 as the year of maximum sunspots, whereas the Astronomer Royal (on ]). 8 of his " Report to the Board of Visitors of the Royal Observatory Greenwich, read on June 7, 1884), says : — " The mean spotted area of the sun was slightly gi'eater in 1883 than during the preceding year." So, again, with his allegation (p. 46) that years of Sunspot Maxima are those of the greatest rainfall : Can his friend, Mr. Symons (p. 70), give him no information on the British rainfall during 1883 and 1884? The argument on pp. 61 and 62, however (if it can be dignified by that name), is perhaps as typical of our author's reasoning capacity as anything he advances. " Mr. F. Chambers," we are told, " has stated that when the sun is most spotty, then the mean yearly pressure on the barometer at Bombay is least ; whOe at St. Petersburg, from 1822 to 1871, the mean height of the barometer is said, contrariwise, to have accorded with the spottings of the sua .... Certainly the spots affect the barometer" (!) This "certainly" is delicious, and strongly suggests the dialogue in the immortal street drama of Punch. " About six weeks ago," says the original owner of Toby, " I lost this dog." " And," responds Mr. Punch, "about six weeks ago I found him." "Well," says his interlocutor, " tliat shows he's mine " " No," says Punch, " that shows he's mine." Is not the parallel perfect] The Student's Guide to Scientific Botany. By Robert Bextlet, F.L.S., ic. (London : J. i A. ChurchLlI, 1884.) — We have one fault to find with Mr. Bentley's excellent little book, and that is the absence of a glossary of botanical terminology from its pages. But for this, it would be as invaluable to the beginner as it now is to the advanced student. Under existing circumstances, the incipient botanist who was struggling to identify one of (say) the Lilia; might rather fail to ascertain whether the specimea under investigation had its " Authers introrse " and its " Fruit a loculicidal capsule," in the absence of any idea what " introrse " and loculicidal " could possibly mean 1 If, however, weconceive him to have mastered these and cognate terms, he could hardly possess a handier or more useful companion in his rambles in search of plants than the work before us. As the majority of the illustrations are taken from British medicinal plants, this small volume would seem to have been chiefly written as a text-book for the botanical examination of medical and pharmaceutical students ; but any one who, by the aid of Mr. Bentley's book, will honestly work through the various genera of plants he describes must assuredly obtain a sound and com- prehensive knowledge of the princip es of systematic botany, to whatever purpose he may ultimately apply it. Wonders of Plant Life under the Microscope. By Sophie Bledsoe Herrick. (London : W. H. Allen & Co., 1884.) — This pretty and pleasantly written volume deals with some of the more remarkable facts in structural and physiological botany, and is well calculated to create, or strengthen, an interest in plant^life, and to invite atten- tion to the marvels which it presents. We note one or two trivial errors in points of detail, but none of sufficient importance to detract from the value of a delightful book> Assuming that the object of its fair authoress has been to make the study of plants attractive, assuredly she has succeeded. Confessions of an English HacMsh-Eater. (London : George Redway, 1884.) — Accepting the recorded expe- riences of the author of this work as genuine, they pre- sent a certain amount of interest to the toxicologist and psychologist. By taking tincture of hemp be appears to have induced a sequence of wild waking dreams and night- mares, which he sets forth in somewhat rhapsodical language. Fortunately we find it hard to conceive that he will make many converts to his peculiar method of intoxi- cation— at all events, in this country. Ox page 8 of the " Report of the Astronomer Royal to the Boartl of Visitors of the Roral Observatorv at Greenwich," presented at the Annual Yisitation of the Eoyal Observatory, June 7, lSS-1, we read that " The mean spotted area of the sun was slightly greater in 1883 than during the preceding year." Hence it is pretty obvious that 1883 was the year of sun-spot maximum of the current cycle. Turning now to p. 34 of the " Results of the Meteorological and Magnetical Observations for 1883," at Stonyhurst College Observa- tory, we find Father Perry saying that " The rainfall for the year was nearly two inches below the average" (for the last thirty-six years). Certain members of a remarkable association at Brompton, known as " The Committee on Solar Physics," are now tired of assui-ing the uninstructed and unscientific public that years of maximum sun-spots are invariably those of maximum rainfall too; and that it is only necessary to pay sufficiently highly to have the one watched to enable the other to be predicted. It is as well that the real truth should be known in this matter before the National Exchequer is further called on to subsidise those who make such baseless assertions. 58 KNOWLEDGE [July 18, 1884. THE FACE OF THE SKY. From Jily ISth to August 1st. By F.R.A.S. SUN-SPOT activity, albeit somewhat subsiding at last, continues sufficiently to render the Sun an interesting object of daily examination. Map VII. of " The Stars in their Seasons" furnishes the present aspect of the night sky. Jlercnry is an evening star, but by no means well placed for the observer. Venus is a morning star, and may be seen before sunrise with the naked eye. To the student who possesses the means of directing a telescope on her during the daytime, she will appear as a lovely object. These are the two solitary planets now visible. The Moon will scarcely come nto view for the purpose of the ordinary observer until about the 27th, being New 54 minutes after noon on the 22nd, and travelling « luthward in the sky. One occultation of a star only will be visible fluring the period covered by these notes. It occurs on the 27th, ■when the 64th magnitude star, 15 A C 4,294, will disappear at the dark limb of the moon at 8h. lUm. p.m. at an angle from her vertex of 164^, and reappear at her bright limb at 8h. 50ra. p.m. at a vertical angle of 229". The Moon is in Taurus to-day at noon, and i-emains in that constellation until 6 a.m. on the 20th, when she passes into the northern part of Orion. This she traverses in, as nearly as may be, 12 hours, entering Gemini at G o'clock in the evening of the same day. She does not leave Gemini for Cancer until 6 a.m. on the 22nd, and, oddly, it is 6 p.m. on the 2.3rd when sbe crosses the boundary into Leo. At 9 p.m on the 24th she descends into Sextans, emerging into Leo again about 9h. 30m. the aiext morning. At 11 a.m. on the 2Gth she enters Virgo, a constel- lation which she does not quit for Libra until 7 p.m. on the 29th. She is crossing Libra until 9 o'clock at night on the 31st, at which instant she passes into the narrow northern strip of Scorpio. Her path over this is traversed by 7h. 30m. the next morning, when she emerges in Ophiuchus. There we leave her. DESIGN FOR PARLOUR ORGAN. OUR engraving shows a design of an organ made many years ago, in which all the pipes arc said to have been made of silver. We present it to our readers with the hope that it may so novel and popular a cliaracter that people must have it would be worth many thousands of dollars to the manufacturer who secured it. — Scientific American. serve as a suggestion leading to the production of something new and good in the form of musical keyed instruments. We are tired of the present stereotyned shapes of our pianos and organs. _ Will not somebody strike out in a new direction? A suitable design of iHiSrrllnnrn. The Koyal Microscopical Society, after carefal deliberation, have decided upon admitting ladies to all the privileges of fellowship, attendance at the ordinary meetings excepted. A COEEESPONDEXT, writing anent a paragraph which appeared in p. 37, says that there must be some mistake in it, inasmuch as both the astronomical Doctors Draper, father and son, are, unhappily, dead. To get rid of the smell of paint, plunge a handful of hay into a pail of water, and let it stand in any room newly painted. The smell will be greatly lessened. It is stated that the gas sold in the metropolis cortinnes to in- crease, the quantity in 1883 being more than 20,000 millions of cubic feet. The quantity is vast, and the consumption of coal is proportionate, the weight carbonised being more than 2,000,000 tons. An article on " Patent Medicines" appears in our contemporary the Lancet for July 5, which may be perused with advantage by all who labour under the delusion that the Government stamp affords the slightest security against even the poisoning of the purchaser of any advertised nostrnm. Ik 1882 the colony of A'ictoria was required by the courts to pay £120,000 to persons injured by accidents on the States railroads, of which it had 1,355 miles. The sum was 17 per cent, of the total net earnings of its railroads. Most of these accidents were on one comparatively short line, and the payments for injaries exceeded the net earnings of this line by about £25,000. The following quantities — in tons — of zinc were produced in 1883, by the different countries named : — The Rhine district and Belgium, 123,891; Silesia, 70,405; Great Britain, 27,661; France and Spain, 14,671 ; Poland, 3.783 ; Austria, 2,870; United States, 32,790 ; totals, 276,080. These figures all show increase on previous years, except as relates to France and Spain and to Poland, which show a decrease. Sir Loris Malet, late Under Secretary of State for India, Sir Evelyn Baring, late Minister of Finance in India, and Mr. West- land, Comptroller and Auditor-General to the Government of India, have addressed a letter to Mr. Henry Dunning Macleod to be forwarded to the Civil Service Commissioners, earnestly recom- mending that his works on Political Economy should be adopted in the Civil Service examinations. Some time since, Dr. Morris, of Birmingham, succeeded, as he believed, in photographing a third sort of blood corpuscle, which, being of the same colour and the same refractive index as the liquor sanguinis, was invisible to the eye. Grave doubt has been thrown on the objective existence of these corpuscles by Mr. St. George St. Clair, who, as the result of a series of experiments, has, he conceives, demonstrated that Dr. Morris's corpuscles are nothing but photographic ghosts. It is estimated that the total annual production of watches in Switzerland at the present day exceeds 1,600,000, with an aggre- gate value of 88,000,000 francs, the total number of workmen em- ployed averaging 40,000. A novel kind of watch has been recently invented by Mr. Paul Kramer, at Neuchatel. This watch is called M aiguilles nniverselles, and indicates simultaneously the times of different countries ; one, for example, shows the different times for Paris, Suez, Bombay and Hue, another for New York and San Francisco. The Anti-Vivisection .Society have lodged a protest against the crucial experiment by which M. Pasteur proposes t.^ demonstrate the efficiency of his vaccine for rabies. Mrs. Kingsford, M.D., who made herself prominent on this occasion, exclaimed that M. Pastetir was not justified in "torturing thousands of animals" with the object of abolishing so " very rare " a disease. The " thonsaads " when translated into the language of sober reason shrink to forty I As for the *' rarity," we must remember that twenty-one persons died of hydrophobia in the Department of the Seine within twelve months. — Medical Press and Circular. A DEPUTATION from the City Commissioners of Sewers visited Wimbledon recently to see the result of the experiments in elec- trical street lighting which have been conducted for some months past by Mr. Preece. From these it appears that 'be most efficient JoLY 11, 1884.] KNOWLEDGE ♦ 59 practical mode of distributing light for a main street, like that of Wimbledon, is by means of 50-candle lamps, fixed 20 ft. high, at intervals of 100 ft. The effects were admitted to be remarkably striking, and to furnish a capital example of efficient street light- ing. We hear that it is within the range of probabilit)' that similar experiments will, ere long, be tried in some of the busier City thoroughfares where arc lights, although not a failure, have apparently fallen short of their anticipated success. Electro-Magnktic Induction. — At the Physical Society recently Mr. C. V. Boys exhibited the phenomenon first observed by Fara- day, that a copper disc suspended bitilarly between the poles of an electro-magnet, so as to cross the lines of magnetic force at an angle, is suddenly kicked or twisted parallel with the lines of force when the magnet is excited. If the disc be perpendicular to the lines of force it is repelled by a pole when the magnet is made and attracted by the same pole when the magnet is unmade. Mr. Boys has investigated the phenomenon very fully, and points out tliat it offers a quick and ready means of measuring the intensity rivate lighting purposes on the payment of two and a half million francs, and its rights are guaranteed by the Government. At the meeting of the Geological Society, on June 25, the follow- ing communication was read : — " Additional Notes on the Jurassic Rocks which underlie London." By Professor John 'W. Judd, F.R.S., Sec. G.S. Since the reading of the former paper on the eubject (Feb. 6. 1881), the well-boring at Richmond has been carried to a depth of more than 1,360 ft. The point reached is, reckoning from Ordnance-datum line, 220 ft. lower than that attained by any other boring in the London basin. A temporary cessation of the work has permitted Mr. Collett Homersham to make a more exact determination of the underground tem- perature at Richmond. At a depth of 1,337 ft. from the surface, this was found to be 75^° Fahr., corresponding to a rise of temperature of 1° F. for every 5243 feet of descent. The bore is still being carried on in the same red sandstones and " marls," ex- liibiting much false-bedding, which were described in the previous communication. The Rev. H. H. Winwood, of Bath, has had the good fortune to find the original fossils obtained by the late Mr. C. Moore from the oolitic limestone in the boring at Meus's Brewery in 1878. A careful study of these proves that though less numerous and in a far less perfect state of preservation than the fossils from the RichmoTid well, they in many cases belong to the same species, and demonstrate the Great Oolite age of the strata in which they occtirred. The Destbuction of Wild Bikds in India. — Under the auspices of the East India Association, a meeting of naturalists, planters, sportsmen, and others interested in the affairs of India wes held on Friday, July 11, at the rooms of the Zoological Society, under the presidency of Professor Flower, LL.D., F.R.S. (Director of the British Museum Natural History Department, and President of the Zoological Society), for the purpose of urging the necessity of Government measures for the preservation of wild birds in India. The principal address was dehvered by Mr. Robert H. Elliot, some- time planter of Mysore, and a well-known writer upon Indian topics. He pointed out that every civilised Government, with the exception of that of India, has recognised the value of birds as insect eaters, and has adopted measures for their preservation ; and that the absence of legislation forebodes, where it has not yet presented, serious results to planters and agriculturists. As tlie most conve- nient season for the destruction of birds is during the fine weather that succeeds the heavy rains of the monsoons, and as this season is also the breeding time, the destruction of insect-eatiug birds proceeds at such a rate as must soon lead to almost absolute exter- mination, unless preservative measures are speedily adopted. There was a general agreement in the meeting that legislation on the subject is imperatively reqtiired, and it was resolved that a repre- sentation to that effect should be addressed to the Government of India. Birds Caught and Killed by the Electric Light. — A despatch from Winona, Minn., describes a very curious incident in connec- tion with the use of the electric light there. It says : — Every night this week thousands of migratory birds have gathered about the electric light on the stand-pipe in this city. Between the hours of one and two o'clock the birds were seen in swarms about the light, and hundreds fell to the ground. A few were caught alive, but the larger part were dead. Prof. Holzinger, of the normal school, reports the following species among those collected during the past two nights at the waterworks: — Catbirds, grossbeaks in variety, scarlet ranagers, golden crown thrushes, water thrushes, chestnnt- sided warblers, blackburnian warblers, Tennessee warblers, magnolia warblers, Carolina rails, yellow-throated vireos, black and white creepers, traels, fly-catchers, green-crested fly-catchers, Savannah sparrows, white-throated sparrows, Maryland yellon'-tbroats, black- billed cuckoos, helldivers, indigo birds, and yellow-bellied wood- peckers. On Tuesday night the grossbeaks predominated, and on AVednesday night the rails. Catbirds were numerous on both nights. The birds which breed in this locality were noticeably absent. S'aluable additions from these birds are being made to the museum of the Society of Arts and Science, and a set of duplicates of most of the varieties has been furnished by Prof. Holzinger ta the high school collection. Many of the birds which were caught alive may be seen in cages at the engine-house of the waterworks. — Electrical World (New York). It has been stated that the Times of June 14 is the largest pro- duction that has ever issued from the daily press with the excep- tion of the Times for Jane 21, 1861. We, therefore, have pleasure in drawing attention to the following : — The Times issued June 14 consisted of twenty-four pages, each containing six columns — 144 columns in all; the total length of which was 264 feet — 52 feet higher than the monument; and they contained enough matter to fill two volumes of 480 pages. Almost every week, at least one issue of the Daily Detroit Free Press consists of twenty-four pages of seven columns each. On June 2, 1878, it consisted of thirty-two pages of seven columns each. On June 8 this year, in cele- bration of its removal into the new Free Press Building, Detroit, and on or about its fifty-third birthday, The Daily Detroit Free Press consisted of thirty-six pages of seven columns each — the largest paper ever printed in the world, we believe. This gives 252 columns, whose total length is 420 feet — double the height of the Monument, and sixteen feet to spare. The paper used to print this edition, run off the reels in a straight line, would extend 108 miles ; while, spread out wide, it would, cover 25 acres ; piled sheet on sheet, as folded, it would tower up nearly three times the height of the Monument ; and, in book form, it would fill two volumes of 600 pages each. The mechanical work — composing, stereotyping, and printing — occupied 148 men ; and the literary matter, outside the reports of the Associated Press, was furnished by no less than thirty-five editors, reporters, and regular contributors attached to The Free Press staff, and forty-two correspondents in various parts of the world. The price was five cents, aa usual. Colouk-Blixdness. — There is every reason to believe that the new apparatus for combining colours, devised by Mr. Offert and by Lord I?ayleigh, will lead to a thoroughly scientific investigation of colour-blindness. Considering how common Daltonism is, and how essential it is that railway men and others working with coloured signals should be free from it, or at least know the extent to which they suffer from it, some simple means of investigating it is desirable. Lord Rayleigh's apparatus is based on double refraction, and the obtaining of two overlapping spectra, which the person under examination looks at, and describes as green, blue, or purple, what- ever it appears to his or her sight. Lord Rayleigh has, we believe, tested the vision of numerous friends, and is willing to extend his observations further. So far he has found that the majority of persons tried require only half as much red in the mixed spectra to turn a given yellow into green as he himself does. People vary from each other in matching colours, and there are grades of " colour- blindness." Ordinary colour-blindness is blindness to red, but the father of Mr. Stanley, the optician, was colour-blind to green. As an engineer, when engaged in colouring plans, he had to single out his green pigments by their names. To him they appeared a kind of brown. Lord Rayleigh has not, we understand, noticed any striking differences between the two eyes of the same person, except what is due to fatigue of one eye and freshness of the other. Dr. Guthrie, who is colour-blind to red, believes himself more than usually sensitive to blue ; and Lord Rayleigh has found persons abnormally sensitive to red, as well as abnormally insen- sitive to it. It would be interesting to discover whether such 60 • KNOAVLEDGE ♦ [July 18, 1884. persona can see further down the red end of the spectrum than is usual. Perh.apR the modification of Lord Eayleij^^h's apparatus, by Mr. Glazebrook, for measuring the distance on the spectrum, which any one can see, will answer this part of the inquiiy. — Encjineering. Fireplaces. — Now is the time to embellish the fireplaces. But what are we going to choose, floral decorations or paper ? Let us hope not the latter, for nothing shows the want of good taste so much as when one enters a room, and is immediately faced by an array of rod tinsel, or some such fiery stuff, to hide the empty grate. Therefore we will put paper out of our thoughts, and seek some other more suitable subject. Plants are exceedingly orna- namental, that is, when nicely arranged. But then the question arises, What have we got suitable ? Palms, grasses, dracsonas, ferns, are excellent, the point being to secure plants with neat and graceful foliage. Then we shall want a fair proportion of colour to light up the group. For this purpose the flowers should be choice as well as showy. A huge geranium or pelargonium placed in the centre of the grate is decidedly unsuit- able, because it betrays bad taste. A neat tuft of white Mar- guerites peeping out from amongst grassy leafage will be decidedly preferable to a large lumpy calceolaria or geranium. The plants will want renewing constantly, because it docs not look well to have sickly plants in such a prominent position. It is customary with many to fit a mirror to the entire opening of the fireplace, and then group the plants in front ; this produces a line effect when the plants are nicely arranged. It is necessary that the plants are cle.an and dry when placed in position, but the soil in the pots should be moist enough to last a few days. If the plants are not kept too long in the parlour, they will be none the worse for the change. — Amateur Gardening. Inteoduction of the Electric Light at Mk. J. F. Milnee's Flour Mill. — A short time ago, a description was given in the Guardian of the new system of grinding coni by the roller process introduced by Mr. J. F. Milner at his Woodsidc mill. Mr. Milncr has now introduced the method of electric lighting at his premises, so that the Woodside mill is now one of the most complete premises for corn grinding to be met with in the north of England. As the mill is run day and night, the introduction of electric lighting will, it is believed, prove to be an immense advantage in many ways. The experiment was tried for the first time on Thursday night, and was found to work admirably, the lamps giving out a clear, steady, and brilliant light. A brief description of the working will be of interest to many readers. The installation consists of one Crompton Burgin compound self-regulating dynamo-machine, and some seventy-six 20-candle power Swan incandescent lamps. The machine, however, is capable of supplying some ninety such lamps, and it is intended to add to the number on the completion of Mr. Miluer's new ofBceg. It is also intended that there shall be an arc lamp on each side of the mill, for loading purposes ; these will bo of the well-known Crompton Crabbe double differential type, of 2,000 actual candle-power. The Crompton Burgin machine is now so well-known that we need not again go into its details ; snflice it to say that any number of lamps can be turned out without affecting the remainder, and that the power absorbed is diminished iu proportion thereto. The Swan lamp, too, is noted for its durability and economy, and has long been recognised as one of the best in the market. The machine is placed on the top floor, where it is driven by a small separate engine, which, although intended to drive the hoist, answers admirably for driving the lights, as it can always be kept running if desired. It is driven by a countershaft, at a speed of 1,400 revolutions per minute. Xear the dynamo is a neatly - polished pitch pine switch - board, containing three main switches, which convey the current to the mill, warehouse, screens, &c., respectively. We may here remark that a very in- genious arrangement has been tried in regard to the staircase, whereby all the lights on the landings can be left burning when the others are turned out, thus enabling any one to see hjs way down the steps after turning out the lights in his own room. On the svritch-board are also a pair of fusible cut-outs (Hedge's patent) , which serve the same purpose as a fusible plug in a steam-boiler. There are also small cut-outs to each lamp, so as to prevent the possibility of fire from any cause whatever. The question of reducing fire-risk in corn-mills is especiallv interesting. The loss by fire in corn-mills has increased from £42"000 in 1877 to £154,000 iu 1883, and this has resulted in the insurance companies raising their rates of premium. The adoption of the electric-light, how- ever, will, it is believed, be a great step towards reducing this risk to a minimum, and it is hoped that ere many months have passed, the insurance companies will recognise its advantages, and reduce their present high rates. The work has been carried out under the superintendence of Mr. J. T. Baron, on behalf of Mr. Wilson Hartuell, electric-light contractor, of Leeds, who recently lighted up the new mill of Messrs. James Clay & Sons, Luddenden Foot. " Let Knowledge grow from more to more." — Alfred Temntson. Only a small proportion of Letters received can jiossiily he in- serted. Correspondents must not le offended, there/ore, should their letters not appear. All Hditorial communications should le addressed to the Editor o» Knowledge ; all Business communications to the Publisheks, at the Office, 74, Great Queen-street, Tr.C. If this is kot attended to delays aeise fob which the Editor is not eespo.nsible. All Rf'mittances, Cheques, and Post Office Orders should he made payaile to Messes. Wyman & Sons. The Editor is not responsible for the opinions of correspondents. No comuunications are answeeed by post, eten though stamped and dieected envelope be enclosed. " THE PEOPHET OF SAN PKANCISCO." [1339] — I fear I am asking more than I oaght to ask of your kind indulgence by begging you to insert such a letter as this, referring, as it doe.?, to a review you were so good as to give in your last number of my pamphlet — " The Unlimited Debt ; " but I cannot help feeling that some injustice has been done me by your calling me " a disciple of Mr. George's," without stating that 1 differ from him in a very important particular, by disapproving of confiscation. Secondly, you say that if rent took the place of taxes, " God help the cultivator of the soil ; " but the whole point of the question is this : — If private property in land is unjust, then that largest of all classes, the poor — including the poor of the towns and the labourers of the counti-y — are those whose case calls most for pity. If the land belonged to the State, they, as part of the State, would benefit by rent ; now they have none of it. As for the tenant, the object of your pity, it must not be for- gotten that he also has now no share of rent, and that he would under the State system have, in addition to his share of rent, the protection of a court of law corresponding exactly to the Irish Land Commission, which has, in fact, been called into existence owing to the necessity' of protecting him from the exactions of private otcners. It was obviously impossible for me to provide against all possible objections within the short compass of a tliree- penny pamphlet, I am therefore the more emboldened to beg the insertion of this letter. — I am, sir, your faithful servant, F. W. D. MncHELL. [I have yet to learn that the Irish Laud Commission has proved such a success as to invite its reproduction in any other country iu the civilised world. — Ed.] MEALWORMS. [1340] — In consequence of absence of home, I missed seeing the number of Knowledge containing F. M. Dnplock's inquiry as to mealworms, and only came across it for the first time a few hours ago, when looking through some back numbers. 1 trust Mr. Duplock will accept this explanation as my apology for the delay in replying to his courteous letter. I fear an article on mealworms is impracticable at present, but perhaps the following notes may be useful. Mealworms are the larva> of two kinds of elongate blackish beetles, Tenebrio molitor and T. ohsrurus, which are the only British representatives of the genus. They closely resemble one another in general appearance, but the latter, which is usually a little the larger of the two, may be at once distinguished by its duller appearance. It is said that the mealworms from the East-end of London are generally those of T. olscunis, and those from the West, T. molitor. The beetles may be found iu bakeries, flour-mills, granaries, &c., where they devour anything farinaceous they can get hold of. They are noted also for the depredations they commit on ship- biscuits. They occasionally fly to gas-lamps like moths. The larva; of the two species are also much alike, that of T. ohscurus being somewhat darker in colotir, and having the terminal seg- ment rather longer. They are said to live two years in the larval state, and then, without forming a cocoon, change to a pupa which displays the form of the future beetle, and is probably the July 18, 1884.] ♦ KNOWLEDGE • 61 "tiny ghost," and "corpse-like thing" referred to, thongh on this point we can scarcely speak definite!}* in the absence of a more accurate description. The pupa state usually lasts about six weeks, but its duration would be largely dependent upon temperature. The beetle, on emergence from the pupa, is soft and of a reddish colour, but, after a while, hardens and darkens. The query as to rariation in size and growth of perfect insects will be found answered in Knowledge, Xo. 138, p. 450. Sex and differences in quality and quantity of food are the principal factors in producing differences in size. Amongst beetles, this variation is greatest in those that feed on solid wood. E. A. BcTLER. 7, Turle-road, Tollington-park, N. TRUE AND FALSE PERSPECTIVE. [1341] — A perspective drawing of an object may be defined as any section of a sheaf of rays of light proceeding from that object to a given point, at which the eye may be placed. If the section be correctly made, the perspective drawing is absolutely true in all cases, and on the application of the eye to the apex {i.e., the given point) of the sheaf of rays the repre- sentation on the section has precisely the appearance of the object; or if the representation be made opaque it will exactly hide the object from the eye. If we decide on making a vertical plane sec- tion of the sheaf of rays parallel to the face of the object, that flecision becomes the governing element in the problem. Ground Plan. In the accompanying diagram 1, 2, 3 are ground plans of cubes. The spaces marked Al, A2 ; A3, A4; A5and A6, are eqaal to each other ; the sides A, B are also equal. To the point S lines are drawn from all the angles of the cubes, which would be seen on placing the eye at S. These lines may be called the leading lines of light from the objects to that point. The section line C, D is parallel to the object, as decided. The spaces on the section line mEirked al, a2 ; aS, ai ; and a5, a6 are equal to each other in the section as they are in the objects. It is evident that on placing the eye at S the space at al, a2 will exactly cover the space Al, A2. All the other spaces of the sec- tion will exactly cover all the corresponding spaces of the objects in like manner, and if we make them opaque they will hide the spaces of the ground-plan and stand for them. What has been demonstrated of a ground plan is equally tme of a vertical section. JoHX Bacox. STRAKGE SKY EFFECTS IN NEW ZEALAND. [1342] — I have just received a letter from a young niece in New Zealand, dated May 20. She writes from near Christehurch, Canterbury : — " We have been having the strangest weather lately, and such curious skies for some months past. The other morning, about 11 a.m., I looked out towards the east, and the sky was all golden and crimson as if it were stinset, as if the sun had made a mistake and was going to bed at the wrong time and in the wrong place. At night, we have the most lovely, rosy lights in the sky : bitt, beautiful as the skies are, and much as one admires them, they seem to give one a sort of uncanny feeling as if something were going to happen." Cosmopolitan. LETTERS RECEIVED AND SHORT ANSWERS. Seneca. If yon are going to try to teach yourself French, pro- bably the "French" in Prendergast's "Mastery Series" is as good a book as yon can get. — Foreigner disagrees with Delille's classi- fication of " mon," "ton," "son," with " le mien," " le tien," 4c. — W. Thanks; marked for insertion. — Edwin W. Morris and A. Mackay. I regret to say that I have been compelled to relinquish lecturing entirely — at all events for a considerable time to come. — M. B. Obviously a misprint, the figures being transposed. — H. G. has found some earwigs in strawberries ! Well, they are not pleasant to look upon ; but, doubtless, in the words of the poem, they are " uonrishing, very." W. C. B. demurs to the idea that a polluted river is necessarily unwholesome, as over and on the banks of one — "a mass of festering filth, chocolate in colour, molasses in consistency, and of stench simply indescribable" — many of his workpeople live hale and hearty, as did he and a large family for fifteen years. Moreover, twenty cows, always well and thriving, drink this filth in preference to pure spring water. Just so ; de gustilus nan est disputandum ! — F. W. D. Mitchell. Your pamphlet was reviewed on p. 36. — J. P. Bourne sends me a " Handy Assurance Guide," consisting of a tabular mass of statistics having reference to ninety-five of the principal in- surance offices in the kingdom. Intending assurers can gather the position and prospects of any one of them from it at a glance. — E. D. Wabeing saw his own ghost in bright sunshine in 1882, and wants to know whether the comet of that year had a disturbing effect upon light ? Unless comets make people light-headed, I should say, no. He further opines that the brain is affected by light, the heart by electricity, and the lungs by oxygen, and that the difference in the shape of light (!) would make the distinction between man and beast, &c. " I have written," says my corre- spondent, " all this very diffidently, feeling not quite sure whether you may not think it great nonsense." Which — in the most sacred confidence — I don't mind admitting to him that I do. — AKXHrE A. West. Having adopted my suggestion (on p. 16) as to drawing the outline of a cube placed behind, and with one face parallel to, a sheet of glass, finds that, under the prescribed conditions, " the top and bottom margins of the face are parallel." His two remain- ing figures I fail to understand, as one represents a sketch made "on glass facing the centre of the cube" (what is the visible centre of a cube ?), and the other " on glass placed facing away from the cube." This is delightfully vague. — W. A. Cooper. Yon may turn the telescope you wish to test upon the following objects : — Z Herculis, X Ophiuchi, r Ophiuchi, jr AquilEe, 4/ Cygni, 49 Cygni (2 ' south-west of f), S Cygni, in twilight only. The ring Nebula between )3 and y Librte, and see if you can see the small star close to and to the east of it. The com- panion to Vega, f' and i- Lyme, in connection with which try bow many stars you can see between the two principal pairs. If the instrument resolves all these tests satisfactorily, buy it. — H. A. Bi-LLEY. When "F.R.A.S." speaks of a planet as "visible," he means visible for the purpose of the observer with the telescope. Perhaps you wiU kindly look at Mars (subtending, as his diameter now does, an angle of less than 6"), and tell us how much detail is visible on his surface, and in what material respect— saving in the exhibition of a rather larger disc — his aspect differs from that of Antares. Mercury is a totally different object, because he is essentially a daylight star, and, under your supposititious con- ditions, would exhibit phases. — H. G. S. It is quite news to me that the erratic genius to whom you refer was an excellent mathematician. But even assuming this to be true, with my present tremendous amount of preoccupation, I certainly cannot spare the time to expose the fallacy of a mere assertion of his, so transparently erroneous, and, moreover, unsupported by the slightest attempt at demonstration. — M. E. Do you seriously expect me to wearily puzzle out the numerical value of 55 figures in succession, with the thermometer standing at 8-1-4 Fahr. in the shade? — Alfred Edward HtTNT. Everybody upon the earth, ex necessitate, partakes of the earth's motion, which affects it utterly irrespective of any other motion that may be impressed upon or imparted to it. The next time yon are in a railway train going 50 miles an hour, drop any object from a point immediately beneath the lamp-glass, and you will find that it will fall vertically beneath that glass on the floor of the carriage, although the carriage has meanwhile moved perceptibly forward. Read Tomhnson's " Rudimentary Mechanics " in Weale's Series. — J. A. E. Have I not said, over and over again, that I must rigidly exclude theology from these columns ? If I admit such a letter as yours, ancf (say) Dr. Aveling or Mr. Bradlaugh were to reply to it, upon what principle of justice could I refuse to insert their' answers ? — E. Jones, having made the experiment suggested on page 16, and finding the result in entire accordance witii the views he previously advanced, offers to forward a proof of 62 ♦ KNOWLEDGE ♦ [Jdly is, 1884. the truth of them to Rosah'e Vansittart and " An Old Draughts- man" privately, ehouldjthat lady and gentleman desii'e it. — An Old Draughtsman. Scarcely relevant to the general subject. — John Bacon. With the excisions rendered imperative by the wholly needless length of your letter, it has been marked for insertion. Thanks for your offer of an article ; but original matter is provided for some time to come. Besides, you must pardon me for saying that you have yet to learn the art of writing briefly and to the point only. — Jos. Lucas and Son. I strongly urge you not to pait with anything to the person yon name, who is certainly an impostor. No member of cur staff would be suffered (or, in fact, would condescend) to accept goods, that favourable notices of them might appear in the pages of Knowledge. — E. B. G. McDougall. Thanks, but none such of any importance reach me. — W. J. 0. suggests that the experiment should be tried of artificially extend- ing the wings of a dead bird and attempting to fly it like a boy's kite. — Maude Le Baille describes, at wholly inordinate lengh, how she succeeded in teaching a little girl to read who had previously defied the efforts of three or four governesses. Briefly she did so by first teaching her to write. The child was allowed to draw on her slate, as well as form letters and figures, the letters being later on com- bined into monosyll.abic words. At this stage, to her own surprise, she found herself capable of reading a page of " Mamma's Lessons." No one but an editor would believe that this is told on nine pages and a half (!) of exercise paper. — Willia.m Singer. As is so perpetually the case with correspondents, tlie length of your letter forbids its appearance. — Jas. Stanley Little intimates that the reviewer of his book (on p. ]2) was in error in supposing him (Mr. L.) to be an artist. He has never attempted to produce even the simplest drawing since he left school. — St. E. There are but few works on "animal" — as contradistinguished from human — physiology. Probably Shea's " Manual of Animal Physiology," published by Churchills, would be as good a book as you could obtain. — Rev. S. B. Handley, and many other correspondents. As stated in my reply to Messrs. Morris and Mackay above, I have entirely ceased lecturing. Should I ever resume it, due notice will be given. — G. C. I should be very sorry to sleep myself, and assuredly would not suffer a child of mine to sleep, in a bedstead placed in the position indicated in your diagram during a heavy thunderstorm. — P. MacLeod Yearslev sends an anecdote of a dog which, finding a piece of meat larger than it coidd eat, went to the very top of the house to fetch a lady down to cut it up. — Wm. Wil.son, M.A., LL.D. Your difficulty seems to arise from the omission by Colenso of the word " whole " before number. Other writers on arithmetic add this word. Of course, in one sense any number, whole or frac- tional, which divides two or more whole numbers exactly, is a common measure of them, and would be i-ightly so described. — The Secretary of the National Smoke Abatement Institution. I regret that absence from London prevented my attendance. — E. C. E. Atmospheric electricity presents to a great extent still an unsolved problem. It is, however, safe to assume that the electric force, which would otherwise cause a dispersion of the cloud particles, is feebler than the other forms of force which cause and maintain a condensation of the originally charged attenuated vapour particles. When the cloud charge attains a high potential, it doubtless experiences a strong tendency to approach the oppo- sitely-charged earth surface bodily. The intervention of the air prevents this, and acting with the electrical attractions, the cloud is broken up. Probably the attraction exerted by the opposite charge on the earth prevents the breaking of the clouds in those higher regions where, under ordinary circumstances, the discharge of rain would commence, and eventually the drops assume larger dimensions. — R. G. T. Madame Blavatzky's trick of causing a bell to sound in the air may be bought at Hamley's, the Noah's Ark, Holborn ; Bland's, New Oxford-street, or at any good shop where conjuring apparatus is sold ; under the title " Is your Watch a Re- peater ? " — Norwich. Many thanks for your kind and friendly letter. Gossip has been rather crowded out for a week or two. — Thos. Maclean. Believe me, I was not indebted to your sug- gestion for the idea of the gyroscope. It has been a familiar one to mo long enough. Alex. Gustafson sends me a little pamphlet on the " Medicine Stamp Tax," which well illustrates the evils arising from the quasi- Government sanction given to all sorts of quack remedies. In reply to numerous letters and communications addressed to tlie office of Knowledge, »'/.'( Editor hegs to aiinou7ice that he has now concluded his Lecturiuj Tour, and has, in fact, definitely ceased, to lecture altogether, iiliould he {which is very douhtfid) at any future time resume his lectures on Astronomy, due and ample notice will be given of such resumption in these coht mns. (3w iHatt)cmatiral Column. w EASY LESSONS IN CO-OEDINATE GEOMETKY. By Bicharo A. Proctob. {Canlinued from p. 19.) E shall now present two forms of the equation to a Btraigiit line which are often found useful. 52. Prop. — To find the equation to the >:traight line in terms of the perpendicular let fall from the pole upon the straight line, and the a iigle u-hich thin perpendicular makes with the axis of x. We have already seen (45) that the polar equation to the straight line in terms of p the perpendicular from the pole on the line and a the angle which this perpendicular makes with the initial line, is r cos {6 — a) =p (i) that is t* cos Q cos a + r sin Q sin a=p but transforming to rectilinear co-ordinates we have r cos 0 = £ and r sin i3 = y thus (i) becomes X cos a -Hy sin a=p the re()uired equation. .")3. On account of the importance of this form of the equation to a straight line we add an independent investigation. Let C A B be a straight line on which the perjiendiciJar O A is let fall from 0. Suppose OA=p, and ZAOB = a. From P any point in C B draw P M perpendicular to 0 X, and draw M K parallel to B C, and PN parallel to -\ K — that is, perpendicular to KM. Then OA = OK-^KA = OK-^PN = OMcosa■^PMsino; that is X cos a+ y sin a =p, as before. 51. As an illustration of the mode of obtaining any one form of the equation to a straight line from another form, we shall show how the equation just obtained may be deduced from the equation. X y a 0 ^ ' in tcnns of the intercepts a and b. In 53 (using the same figure) and o=OB=j) sec CI ; and 6 = 0 C=p cosec a ; substituting these values in (i) we get y = 1 p sec a p cosec a that is iT cos a + y sin a= p, as before. 55. Note. It is necessary that the student should carefnltv observe in what manner equations of the form just obtained are to be interpreted. And first of the perpendicular p and the angle a, it is to be noted that a positive distance p is to be measured along a line inclined to OX at an angle a (measured as described in former articles. The required line is then to be drawn at right angles to the line thus obtained, through its extremity. Thus in the equation a: cos a + II sin a — p = 0 p is invariably a positive quantity. 5t>. To put the general equation A.T-I- B(/-hC = 0 (i) into the form just obtained, proceed as follows : — Divide each term by v^A- + B" Ki'''''B that sign to the radical which w^ill makp the constant term C negative. Thus (i) becomes JOLY IS, 1884.] ♦ KNOWLEDGE ♦ 63 A ■ :- v'a ]!v \'' A-VB + B' iu which the last term IS IICL' ilive since / A ^ , _ :=0 v/A' + B^ This is of the required form B = 1 57. — The student will find it a useful exercise to trans)iose an equation to a fixed, straight lino into the different forms we have been examining. He will find that when proper attention is paid to the directions in which lines and ann;les are measured, no difficulty can occur in interpretinff the constants which appear in different forms of the equation. On one point comment ia neces- sary. The angle which a straight linn makes with either axis is not necessarily the acute angle between the line and that axis. Thus the line B C (B on O X. C on O V) makes with 0 X is not the angle C B O but the angle C B X. since this is the angle through which a line coincident with O X would have to revolve in the positive direction, about the point B, to become coincident with C B. We might also say that the line C B is inclined to <) X at a negative angle C B 0. i(o 7 equal parts, and join C with the division nearest to B, the division nearest to C with the next division from B and so on. It will then be easy, in the inanner nf the preceding example, to show that any one of the 8 parts into tt'hich the diagonal is thus divided is equal to any other part — or, in other words, that the diagonal is dividf^d into 8 equal parts. 178. In the straight line A B C, A B is equal to BC. Show that perpendiculars drawn from the points A, B, and C upon any straight line mset it in eqni-distant points. (i.) When the line passes between A and C. (ii.) When the line does not pass between A and C. 179. In case (ii.) of Example 178, show that the perpendicular from A and C are together double of the perpendicular from B. 180. Incase (i.) of Example 178, show that the difference of the perpendiculars from A and C is double of the perpendicular from B. 181. If straight lines be drawn from the angles of any parallelo- gram perpendicular to a straight line which is outside the paral- lelogram, the sum of those from one pair of opposite ano-les is equal to the sum of those from the other pair of opposite angles. 182 Determine a point in the base of a triangle from which lines drawn parallel to the sides, to meet them, are equal. 183. If an hexagonal figure admits of division into three paral- lelograms each pair of opposite sides are equal and parallel. Siiow that in general such an hexagonal figure admits of beino- divided into three parnllelograms in two different ways. 184. If each pair of opposite sides of a hexagon are parallel, and one pair equal, the other pairs are also equal. 185. If each pair of opposite sides of a hexagon be equal and parallel, the three straight lines joining opposite angles will meet in a point. ISO. If each pair of opposite sides of a rectilinear figure havin"- an even number of sides be equal and parallel, all the lines joining opposite angles meet in a point. 187. Describe a rhombus within a given parallelogram, so that one of the angular points may occupy a given point on the peri- meter of the parallelogram. 188. Describe a rectangle within a given parallelogram, so that one of the angular points may occupy a given point on the peri- meter of the parallelogram. In examples 187 and 189 if suffices that the angles of the con- structed figures should lie on the sides or the sides produced of the parallelogram. Prei-ious examples shoio the relations which hold tvhen a parallelogram is a rhombus or rectangular, and these icill be found sufficient for the solution of Examples 1S7 and 180. 189. The three sides of a triangle are together less than the three lines drawn from the angles to the bisections of the opposite sides. Complete a parallelogram having two sides of the triangle as adja- cent sides. Then show that these sides are together greater than the diagonal which passes through the bisection of the 6a.se, ^c. 64 ♦ KNOWLEDGE ♦ [July 18, 1884. ©uv Cfiesisi Column* By Mephisto. JLAYED July 9 in the Handicap at the Divan. King's Bishop's Pawn. Wlite. Mundell. 1. P to Kl 2. B to Bi (a) Kt to QB3 Pto Q3 B to Kt3 Black. Gunsberg. P toQ3 Kt to KB3 P toKJ. Kt to B3 Kt to Q5 QKt to K2 (!)) Kt X B RP X Kt P to KB4 9. Kt X P 10. Kt to B3 11. Castles 12. B to K3 ((■) 13. B to Q2 14. P to Q4 15. PtoB3 16. R to K s(i. 17. Kt to E5 ((I) 18. P to E3 19. Kt X Kt 20. K to R st(. 21. P to QKt4 Bto K2 P X P Castles P toB3 P to KR3 Kt to Kt5 B to B3 Q to Kt3 R to K sc|. B toQ2 Bi;oK2 Kt to B3 B X Kt Q to Kt4 Q to KR4 (e) Position after Black's 21st move. "Whitb. White. Mundell. 2fi. Kt to Q3 27. P to KKtl 28. Rto K3 (i) 29. Q to K2 30. R to KB sq. K to R2 (it) R to B2 (0 R X B R (Q3) to B3 R X B 36. QtoK5 37. ]' X Q 38. R X R 39. R to Bo 40. R to B6 41. R to 06 Remove Black's Black. Gunsberg. B X P Q to B3 B to B2 0) B to Kt3 B to K5 (ch) R to KB sq. B X Kt (m) B to Q3 B X B Q to Q3 Q X Q R X R R to K sq. P to Kt3 K to Kt2 K to B2 (n) Position after Black's 41st move. Whitb. r .•- r ' ■ ■- it 1 .^: ,1 a 22. B to B4 23. P to K5 24. P to KB (<7) 25. Kt to K5 (;i) B to K2 (/) PtoQ4 QB to B sq. Q to B4 ■\ t il s Black. 42. Bto Q7(ch)(o)R to K2 43. R X R K X R 44. P to KKto (p) P to KR4 (q) 45. K to Kt3 46. K to B4 47. P to Kt3 48. P to B4 49. P X P (r) 50. P to B5 K toK3 P to Kt3 P toR3 P X P PtoR4 Resigns (s) XOTES. (a) This can hardly be considered as good as 2. P to Q4. (b) To disengage his Queen's side, and make both Knight's available for attack on the K's side. (c) This move gives Black time to develope his pieces. (d) If P to R3, then Kt to K4. Black has brought his pieces vrell into play. (e) A very useful flank movement. The Queen now occupies a good position. (/) With a view to playing R to B sq., which might give a chance for B x RP. (3) Although tempting, this is weak, as the P will sooner or later be captured. (h) If Black plays Q x Q. 26. QR x Q, B x P. 27. Kt x P. (j) To guard against Q to R5, also to double his Rook on the K's ae. (j) To bring the B into good play. (k) K to Kt sq. was the proper move. (I) To guard against P to KKt4. (m) Black now brings about the exchange of four pieces, re- maining with a superior end position. (?i) If R X P White could equalise the game by playing R to Q7 (ch), followed by R x P aud R to B7, &c. (o) This is playing Black's game. White ought to have played R to B6 (ch), driving the K back agtiin. (p) A good move. It would be dangerous to take, as by K to Kt3 and Kt4 White would gain a decisive advantage. (9) Now, of course, the game i."; virtually over, as White has but the one square on B4 to defend his KP, and when short of a move he will have to move his K. ()•) Now comes the most extraordinary part of the game, which Whitb. should serve as a warning ihat a game is never won until check- mate is given. By playing P to B4 Black wins, as the Hook's Pawn becomes free to advance whether White replies with P x P or P to Kto. Instead of winning the game on the move Black lost it on the move by ha.'itily advancing the wrong Pawn without examining the conse- ((uences. Besides losing the well- earned victory in a hard fought game. Black loses all chance to play for first and second prize, although this is the only game lost out of eight games played. (•') The game is not to be saved if Black plays P to R5 then P X P, P to R6. P to Kt7 (it would be quite useless to plav the K on account of P to KG) P to R7. P to KtS (Q), P to R8'(Q). Q to QC (ch), K to B2. P to K6 (ch), K to Ki sq. Q to KtS (ch), K to R2. Q to B7 (ch), K to Kt sq. Q to B7 (ch), K to R Bq. Q to B6 (ch) and wins. Buck. SOLUTIOX OF PROBLEM, p. 490. Q to K4 (threatening Kt to Kt3(ch) and Kt to Q7 mate) Q toKt4 Kt mates accordingly. 1. Kt to KB3(best> 2. Any. ANSWERS TO CORRESPONDENTS. »*» Please address Chess Editor. Correct solutions received from C. T. Grey and Eugene Hamburger. Paired for correspondence play, Senex v. Clarence. TuE EuMo.vi) Beds of BK.iziL. — The diamond beds of Bahia aucj Minas Geraes, in Brazil, are very similar in character as regards the minerals composing them and their plateau form, or situation on watercourses. A new bed has been recently opened on the Rio Purdo in Bahia, which presents some differences to those hitherto known in Brazil. The country around is low and marshy, and covered with forests. The working of these forests has led to the discovery of the diamonds, which are found in a white clay along with beds of decomposed leaves. The deposit appears of modem formation. The minerals of the clay accompanying the diamond are, according to JI. Gorceux, quartz, silex, monazite, zircon, dis- thene, staurotede, grenat almandine, corindon, and some oxides of iron. There are no oxides of titanium, or tourmalines, as is fre- quently the case in diamond beds. The clay appears to be from its character and situation the dthris of the granite mountains bordering on the Bahia coasts. — Engineering. Contents op No. 141. PAGB Other Worlds than Oars. By M. de Fontenelle. With Notes by Richard A, Proctor 21 Dreams. IT. By Edward Clodd . 22 The Entomology of a Pond. {Illits.) By E. A. Butler 24 A Novel Fire Escape, illbis.) 25 Notes on Flying and Flying Ma- chines. By R, A. Proctor 25 The Tricvcfes of To-dav. The " Cheyle'smore Club." (/Him.) ... 28 TheElectro.Magnet. ByW. Slingo. (I«iM.) 29 The .Antarctic Regions. By R. A. Proctor 30 Optical Becreationa. {Illut.) By F.R.A.S 32 The International Health Xibibi- tion. VII. (/«■«.) 34 Reviews : Some Books on Our Table 36 Miscellanea 37 Correspondence : Savage Names — Colours of Clouds — Acarisa and Orjbatidie, &c 38 Our Mathematical Colomn -lO- Our Chass Colomn 41 SPECIAL NOTICE. Part XXSII. (June, 188-1), now ready, price Is., post-free, 1b. 3(1. Tolome V., compriaing the numbers published from January to Jane, 188-J, will soon be ready, price Ss., including parcele postage, Vs. 6d. Binding Cases for all the Volumes published are to be had, price 2s. each ; including parcel postage, 28. 3d. Subscribers* numbers bound (inelnding title, index, and case) for Ss. each Yoliune ; including return journey per parcels post, 3a. 6d. Bemittances should in every case accompany parcels for binding. OFFICE : 74-76, GREAT QUEEN STREET, LON'DOX, W.C July 25, 1884.1 * KNO^AALEDGE • 65 11 AN ILLUSTRATED ^^J^T __ MAGAZINE OF SCIENCE ^AINLYWORDED -exactlyDescribed LONDON: FRIDAY, JULY ^T^, 1884. Contents op No. 143. PAGE Dreams. Y. By Edward Clodd .,, 00 The Antarctic Hegions. By R. A. Vroclor t^ti Sensation in a Severed Head 67 The Electro -Magnet. By W. SUngo. illlu*.) 63 Other Worlds than Ours. By M. de FonteneUe. With Notes by Richard A. Proctor 60 Novel Tricycles. By John Browning 70 ?A6B The International Health Eihibi* tion. IX. (Itlitx.) 71 Thunderstorms... 73 Reviews 75 Miscellanea 76 Correspondence : Dickens's Story Left Half Told (No. 139)— The Solar Glow, &c 77 Oar Mathematical Coluam 79 Our Chesa Golonm SO DREAMS : THEIR PLACE IX THE GROWTH OP PRIMITIVE BELIEFS. By Edward Clodd. \. THE confusion in the barbaric mind between the objec- tive and the subjective, and between the name and the person or thing, which has been illustrated in the fore- going chapters, will enable us to see more clearly how the like confusion must enter into the interpretation of such occult and compound phenomena as dreams, and all their kind. They supply the conditions for exciting and sustaining that feeling of mystery -which attends man's endeavour to get at the meaning of his surroundings. The phantasies which have detiled through the brain in coherent order, or danced in mazy whirl about its siuuous passages when com- plete sleep was lacking, leave their footprints on the memory, and they are strong of head and heart, true pep- ticiaiis, like the countryman cited by Carlyle, who, "for his part, had no system," whose composure on awaking is not affected by the harmonious or discordant, the pleasant or disagreeable illusions -which have made up their dreams. In the felicitous words of Luci'etius, " when sleep has chained down our limbs in sweet slumber, and the whole body is sunk in profound repose, yet then -we seem to our- selves to be awake and to be moving our limbs, and amid the thick darkness of night we think we see the sun and the daylight ; and though in a confined room, we seem to be passing to new climates, seas, rivers, mountains, and to be ^crossing plains on foot, and to hear voices, though the austere silence of night prevails all round, and to be utter- ing speech, though qnite silent. Many are the other things of this marvellous sort we see, -which all seek to shake, as it -were, the credit of the senses : quite in vain, since the greatest part of these cases cheat us on account of the mental suppositions which we add of ourselves, taking those things as seen -which have not been seen by the senses. For nothing is harder than to separate manifest facts from doubtful, -which the mind without hesitation adds on of itself."* *De rerum Natura, B. IV. U. 453-468. While for us dreams fill an empty moment in the telling, albeit now and again nurturing such remains of superstition as cling to the m.ijority of people, they are to the untrained intdligcnce, unable to distinguish fact from fiction, or to fullow any sequence of ideas, as solid as the experiences of -waking u.oments. As a Zulu, well expressing the limits of savage thought, said to Bishop Callanay, " Our knowledge does not urge us to search out the roots of it, we do not try to see them, if anyone thinks ever so little, he soon gives it up, and passes on to what he sees with his eyes ; and he does not understand the real state of even what he sees." Kor does his language clear the confusion within when he tells what he has seen and heard and felt, where he has been and what he has done, for the speech cannot transcend the thought, and therefore can represent neither to himself nor to his hearers the difference between the illusions of the night and the realities of the day. The dead relatives and fiiends who appear in dreams and live their old life, with whom he joins in the battle, the chase, and the feast, the foes with whom he struggles, the wild beasts from whom he flees, or in whose clutches he feels himself, and with shrieks awakens his squaw, the long distances he travels to sunnier climes lit by a light that never was on land or sea, are all real, and no " baseless fabric of a vision." That now and again he should have walked in his sleep, would confirm the seeming reality ; still more so would the inten>ified form of dreaming called " nightmare," (or night>spirit) when hideous spectres sit upon the breast, stopping breath and paralysing motion, and to which is largely due the creation of the vast army of nocturnal demons that fill the folk-lore of the world, and that, under infinite variety of repellent form, have had place in the hierarchy of religions. Dreams are in the main referred by the savage either to the entrance into him of some outside .spirit — as among the Fijians, who believe that the spirit of a living man will leave the body to trouble sleeping folk — or to the real doings of himself. When the Cireenlander dreams of hunting, or fishing, or courting, he believes that the soul quits the body ; the Dyaks of Borneo think that during sleep the soul some- times remains in the body or travels far a-\vay, being en- dowed, whether present or absent, with conditions which in -naking moments are lacking. Wherever we find a low state of mental development the like belief exists. In Mr. im Thurn's elaborate work on the Indians of Guiana, already reviewed in this journal, we have corroborative evidence, the more valuable because of its freshness. He tells us that the dreams which come to the Indian are to him as real as any of the events of his waking life. To him dream-acts and waking acts difler only in one respect — namely, that the former are done only by the spirit, the latter are done by the spirit in its body. Seeing other men asleep, and afterwards hearing from them the things which they suppose themselves to have done when asleep, the Indian has no difliculty in reconciling that which he hears with the fact that the bodies of the sleepers v.cre in his sif;ht and motionless throughout the time of supposed action, because he never question that the spirits, leaving the sleepers, played their part in di'eam-adventures. Mr. im Thurn illustrates the complete belief of the Indian in the unbroken continuity of his dream life and waking-life by incidents which came under his own notice, and which are quoted as serving the argument of this paper better than any theorising. " One morning when it was important to me to get away from a camp on the Es.sequibo River, at which I had been detained for some days by the illness of some of my Indian companion?, I found that one of the invalids, a young 66 ♦ KNOWLEDGE . [July 25, 1884. Macusi, though better in health, was so enraged against me that he refused to stir, for he declared that, with great want of consideration for his weak liealth, I had taken him out during the night and had made him haul the canoe up a series of difficult cataracts. Nothing could persuade him that this was but a dream, and it was some time before he was so far pacified as to throw himself sulkily into the bottom of the canoe. At that time we were all suffering from a great scarcity of food, and, hunger having its usual effect in producing vivid dreams, similar events frequently occurred. More than once, the men declared in the morn- ing that some absent man, whom they named, had come daring the night, and had Ijeaten, or otherwise maltreated them ; and they insisted on much rubbing of the bruised parts of their bodies. Another instance was amusing. In the middle of one night I was awakened by an Arawak named Sam, the captain or head-man of the Indians who were with me, only to be told the bewildering words, ' George speak me very bad, boss ; you cut his bits ! ' It was some time before I could collect my senses sufficiently to remember that 'bits,' or fourpenny- pieces, are the units in which, among Creoles and semi- civilised Indians, calculation of money, and consequently of wages, is made ; that to cut bits means to reduce the number of bits, or wages, given ; and to understand that Captain Sam, having dreamed that his subordinate George had spoken insolently to him, the former, with a fine sense of the dignity of his office, now insisted that the culprit should be punished in real life. One more incident, of which the same Sam was the hero, may be told for the sake of the humour, though it did not happen within my personal experience, but was told me by a friend. This friend, in whose employ Sam was at the time, told his man, as they sat round the tire one night, of the Zulu or some other African war which was then in progress, and in so doing inadvertently made frequent use of the expression, ' to punish the niggers.' That night, after all in camp had been asleep for some time, they were raised by loud cries for help. Sam, who was one of the most powerful Indians I ever saw, was ' punishing a nigger ' who happened to be one of the party ; with one hand he had firmly grasped the back of the breeches-band of the black man, and had twisted this round so tightly that the poor wretch was almost cut in two. Sam sturdily maintained that he had received orders from his master for this outrageous conduct, and on inquiry, it turned out that he had dreamed this."* * Taking an illustration from nearer home, although from a more remote time, we have in the Scandinavian Tatns- dajla Saga a curious account of three Finns who were shut up in a hut for three nights, and ordered by Ingimund, a Norwegian chief, to visit Iceland, and inform him of the line of the country where he was to settle. Their bodies became rigid, and they sent their souls on their errand, and, on their awaking at the end of three days, gave an accurate account of the Vatnsdal, in which Ingimund ultimately dwelt. No wonder that in media-val times, when witches swept the air and harried the cattle, swooning and other forms of insensibility were adduced in support of the theory of soul-absence, or that we find among savages — as the Tajals of the Luzon islands — objections to waking a sleeper lest the soul happens to be out of the body. As a corollary to this belief in soul-absence, fear arises lest it be prolonged to the peril of the owner, and hence a rough and ready theory of the cause of disease is framed, for savages rarely die in their beds. That disease is a derangement of functions interrupting their natural action, and carrying attendant pain as its • " Among the Indians of Guiana," pp. 3i4-346. indication, could not enter the head of the uncivilised; and, indeed, among ourselves a cold or a fever is commonly thought of as an entity in th« body which has stolen in, and, having been caught, must be somehow expelled. With the universal primitive belief in spiritual agencies every- where inhaled with the breath or swallowed with the food or drink, all diseases were regarded as their work, whether, as remarked above, through undue absence of the rightful spirit or subtle entrance of some hostile one. If these be the causes to which sicknesses are due, obviously the only cure is to get rid of them, and hence the sorcerer and the medicine-man find their services in request in casting out the demon by force, or enticing him by cajolery, or in bringing back the truant soul. THE ANTARCTIC REGIONS. By Richard A. Pkoctor. (Continued from p. 56.) IF we consider the nature of the Antarctic Seas, and particularly the circumstance that the Antarctic summer is far colder than the Arctic summer, it will appear most probable that within the Antarctic regions land and water are so distributed that, while the shore-lines are of great extent, there is very free communication with the open Antarctic Ocean. In other words, it seems reason- able to conclude that there are many large islands within the Antarctic circle, that these islands are separated from each other by wide passages, and not by straits readily blocked up and encumbered with ice in such sort as to impede the outward passage of the great icebergs. And nothing which has been ascertained by Antarctic voyagers is opposed to this conclusion. It is, indeed, very easy to fall into the mistake of inferring otherwise from the study of an ordinary chart of the Antarctic seas. If, for example, we look at the chart in ]^Iaury's " Physical Geography of the Sea," we are apt to imagine that the boundary line indicating the limits of Antarctic explorations points to the existence of a continuous barrier of ice, the advanced line of defence, as it were, behind which lies as continuous a barrier of precipitous shore-line. But a very slight study of the records of Antarctic voyages will suffice to show how erroneous is such an impression. We find that long before coast-lines have been seen, the hardy voyagers have found themselves impeded and often surrounded by masses of floating ice. Wilkes, Ross, and D'Urville, when struggling to advance towards the southern pole, were repeatedly com- pelled to retreat without seeing any signs of land. Land has not been seen, indeed, along more than one-sixth part of the circuit of the Antarctic barrier, and it has only been in the neighbourhood of Victoria Land that a continuous coast-line of any considerable extent has been discovered. Wherever land has been seen, it has been mountainous and rugged — a circumstance which suggests great irregularity of outline in the land-regions, and the high probability that these regions are broken up into islands resembling those in the north-polar seas. Certainly, there is much in what has been learned or may be inferred respecting the Antarctic regions, to suggest the wish that further explorations may one day be undertaken. When we consider what has been done with sailing-ships, it seems by no means unlikely that with steamships suitably constructed the Antarctic seas might be successfully ex- plored. I would not encourage the idle ambition to pene- trate so many miles farther southward than has hitherto been found practicable. But there are many and legitimate July 25, 1884.] ♦ KNOWLEDGE 67 considerations in favour of further exploration. " Within the periphery of the Antarctic circle," says Captain Maury, " is included an area equal in extent to one-sixth part of the entire land surface of our planet. Most of this immense area is as unknown to the inhabitants of the earth as the interior of one of Jupiter's satellites. With the appliances of steam to aid us, with the lights of science to guide us, it -would be a reproach to the world to permit such a large portion of its surface any longer to remain unex- plored. For the last 200 years, the Arctic Ocean has been a theatre for exjiloration ; but as for the Antarctic, no e.xpedition has attempted to make any persistent exploration, or even to winter there. England, through Cook and Ross ; Russia, through Billingshausen ; France, through D'Urville ; and the United States, through Wilkes, have sent expeditions to the South Sea, They sighted and sailed along the icy barrier, but none of them spent the winter, or essayed to travel across and look beyond the first impediment. The expeditions which have been sent to explore unknown seas have contributed largely to the stock of human knowledge, and they have added renown to nations, lustre to diadems. Navies are not all for war. Peace has its conquests, science its glories ; and no navy can boast of brighter honours than those which have been gathered in the fields of geographical exploration or physical research." It does not appear that Antarctic voyages would be attended with any excessive degree of danger. Ko ship has hitherto been lost, I believe, in explorations beyond the Antarctic circle. It may be said, indeed, that such attempts are rather arduous than dangerous. It may even be found that the Antarctic barriers are impenetrable, but this has certainly not as yet been demonstrated. And it is far from being improbable that, if success could be achieved, an important field of commercial enterprise would be opened. The Antarctic regions are not mere desert wastes. The seamen under Ross found Possession Island covered by penguins standing in ranks like soldiers, and too little familiar with the ways of man to attempt escape. More valuable animals live and thrive, however, in Antarctic seas. Whales and seals exist there in abundance, and, as Captain Maury has well remarked, " of all the industrial pursuits of the sea, the whale fishery is the most valuable." In Arctic fisheries, he tells us, three thousand American vessels are engaged, and " if to these we add the Dutch, French, and English, we shall have a grand total of perhaps not less than six or eight thousand, of all sizes and flags, engaged in this one pursuit." There are reisons for believing that whale-fisheries in Antarctic regions would afford a richer, as they would certainly aflbrd a far wider, field for maritime enterprise. SENSATION IN A SEVERED HEAD. DURING the murderous horrors of the great Revolution stories were current of heads retaining consciousness and sensibility after the guillotine had separated them from the bodies of the victims, and it has been a question of interest to physiologists and philanthropists how soon absolute death supervenes upon decapitation. A curious case is mentioned in our issue for June 27, but later observations and experiments have been published. On the 30th April la^t, a criminal, whose real name was not revealed, but who went under that of Campi, was executed in Paris, and arrangements were made by M. Laborde to experiment with his remains. A curious custom prevented the doctor from receiving his sub- ject until a funeral service had been performed at a cemeterj', and thus an hour and twenty minutes elapsed between the fall of the knife and the beginning of the experiments, of whicli a full account will be found in the Revue Scientijlqiie for the 21st of June. While assistants were connecting the carotid artery of a dog with the severed artery of the head in order to supply it with the stimulus of freshly-circulating blood, JI. Laborde endeavoured to excite the spinal marrow by electric shocks, but without effect, whether he operated upon the portion connected with the trunk, or upon that of the head. The muscular system res^ponded to the electric excitation, but the nervous system was impassive — it had become totally and irrecoverably insensible an hour and a half after the decapitation. M. Laborde's conclusion was that " the nervous tissue in general is the first to lose its power when the circulation is stopped, and that the head is the first part of it to be dispossessed of its functions.' " In order," he said, " to restore to tliis organ perception and consciousness, it would be necessary not only to replace experimentally its conditions of circulation, but to do so as quickly as possible, before there was time for a definite and irremediable loss of functional power." But, however interesting to science, both humanity and morality would be shocked if any wretched victim of the law were recalled to even momentary life and suffering. The failure of the experiments with Campi led to an abominable trial with a dog, subjected to decapitation and transfii&iou of blood, when the animal is reported to have recognised a familiar voice by a smiling motion of its mouth. More lately, M. Petitgand has contributed to these inquiries observations he made in 1875, when wit- nessing the execution of an Annamite at Saigon. Ac- cording to his account in the Revue Scientifique for July -5, the execution took place on the sandy Plain of the Tombs, the cemetery for the Annamites and Chinese. Four pirates, captured in arms, were the sufferers. Their chief was a strong man in the prime of life, and meeting his fate with calm courage, the doctor determined to keep his eyes fixed upon him. According to the local mode of execution, the pri- soner has his hands tied behind him and fastened to a post. He has then to kneel down and bend his head, so as to stretch the intervertebral substance as much as possible, and if the victim shrinks, an assistant holds him in the right position by his long hair. In this case no such aid was required. The executioner marked the spot he wished to strike with betel juice, and then, with the sweep of a long, broad, and thin sabre, effected his business at one stroke. M. Petitgand remarks that, when decapitation is skilfully performed in this manner, there is no contusion of the spinal marrow, which occurs with the guillotine, unless it happens to cut neatly through an intervertebral disk. When the head is roughly severed, as in Campi's case, he supposes the shock so stupefies the nervous centres as to render any subsequent manifestation of function of the brain quite impossible. In the Aunam case he did not for an instant lose sight of the condemned man, but addressed some words concern- ing him to the oiiicer superintending the execution, in a loud voice. He noticed, also, that the patient examined him with the most lively attention. When the prepara- tions were finished, the doctor retired a couple of metres, and the victim, before bowing his head, exchanged glances with him. The head fell less than two metres from him, and did not roll as usual, but stood upright on the sand, which reduced the h.-emorrhage to a minimum. " At this moment," exclaims the doctor, " I was alarmed to see the eyes of the victim fixed upon mine. Hesitating to believe this a manifestation of consciousness, I moved quickly in a quarter-circle round the head, and I can affirm that the 68 ♦ KNOWLEDGE • [July 25, 1884. eyes followed me. I then returned to my first position, moving more slowly. The eyes still followed for a very brief moment, and then suddenly left me. The face, at this instant, expressed manifest anguish — the poignant agony of a person suffering acute asphyxia. The mouth opened visibly, as if struggling for air ; the head then lost its balance and rolled on one side, the contraction of the maxillary muscles being the last sign of life. From fifteen to twenty seconds had expired." M. Petitgand considers that when a head is separated from a bod}', and the loss of blood does not exceed certain limits, and it contains suflioient oxygen to stimulate the nervous function, sensation may last for possibly half a minute. Thus, in certain cases, beheading may be a bar- barous punishment, and " the patient may be conscious some time after his execution ; but, in a great majority of cases, fears of such a survival are chimerical. It is almost impossible that the vertebral column, struck obliquely by the knife of the guillotine, should not occasion a shock sufficient to suspend all the cerebral functions." In the case of the Annamite, the heart made twelve or fifteen pul- sations after the severance of the head. It may be concluded from these observations of M. Petitgand that the hanging of criminals in the manner now practised in this country must produce immediate insen- sibility, as the dislocation of the spine must occasion the violent shock which he believes instantly paralyses the nervous system. S. THE ELECTRO-MAGNET. By W. Slingo. (Continued from p. 30.) A LITTLE careful study of the two small diagrams (Figs. 1 and 2) which ajipeared in the previous article (and which are here reproduced for the sake of reference) will have made clear the diotinction between a Figa. 1 and 2. right and a left handed helix. The idea is perhaps more easily grasped by a reference to the accompanying addi- tional illustration (Fig. 3), where both modes of winding Fig. 3. are applied to a single coil. The winding commencing at N, the first half of the coil, NS, is a left-handed helix, while the second half, S N', is a right-handed helix. It will be seen that at S the wire is turned back on itself, and the direction of winding reversed. Now for the polarity induced. The arrows in each case indicate the direction taken by the current. Thus in Fig. 1 the current enters at the end marked N, and passes round the glass in the opposite direction to that taken by the hands of a clock. Kemembering, however, what was said about the little man swimming with the current, that is, that when facing the iron or the axis of the coil, the north pole would be on his left hand, we can easily deter- mine the polarity of the ht-li.ic and the iion embraced by it. Thus, if we imagine the little man to be in the upper portion of the first ring or loop, he must, to follow out the conditions referred to, lie face downward with his head in the direction of the retreating current (or away from the reader's eye). Clearly his left hand will be towards X, and his right hand towards S. Supposing the miniature man to be in any other portion of the ring, he willstill have his left hand N-wards, and consequently every ring or every fraction of a ring helps to increase the intensity of magnetisation. It may, however, be observed that the rings are not perfect, but that in passing from one ring to the next there is a slight longitudinal deviation. The sum total of these devia- tions, s'lpposing the iron rod to be covered from end to end, is equal, evidently, to a single wire the length of the coil, or of its iron core. The effect of such a wire would be exerted at right angles to that of the series of rings ; but inasmuch as the single wire Ls materially less etTectual than the rings, and for other reasons which need not here be dwelt upon, such an antagonistic tendency as that exerted by the wire is so infinitessimal as to be lost sight of. Thus, then, in a left-handed helix the end where the current enters becomes a north pole, the other end becoming a south pole. Conversely it will be seen that in Fig. 2, where there Ls illustrated a right-handed helix, the arrows indicate that the current pursues the same direction as the watch-hands (viewed from the end at which the current enters), and that to comply with Ampere's conditions the little man in the upper portion of any loop or ring must lie face downwards, with his head towards the reader, when his left hand will be extended towards the extremity of the iron rod marked N, or in the opposite direction to that indicated in the previous figure. The polarity of the iron rod is therefore reversed, and it may be well to note that with a right- handed helix the point of entry becomes a south pole, the other end becoming consequently a north pole. But now the interesting question presents itself : What is the efiiect of changing the heliacal direction, or the direction of winding around one and the same core 1 To take the simplest case, we may place a left and a right- handed helix end to end on a common core, and then, joining them together, we shall get a result resembling the accom- panying illustration (Fig. 3). Here the current enters a left-handed helix at N, but at S it leaves the lefthanded and enters a right-handed helix, through which it passes, emerging at N'. In this case, the coil and its core have three poles, one south and two norths, and a little reflection or re-perusal of what has been previously said will make clear the appearance of a south polarity at S, due in the first place to the current emerging from a left-handed helix, and strengthened by the current entering a right-handed helix. In both cases the tendency is to create this south pole. Similarly, the two extremities of the core become north poles on account of the current at N entering a left- handed helix, and at N' leaving a right-handed helix. It may be as well to point out here that, although we may maintain that the two magnetic conditions are equal in every magnet, it does not follow that every magnet contains or possesses only two poles at the extremities separated in the centre by a neutral line or zone. This idea is more prevalent than most people imagine, and it is on this account that the point is here referred to. We may introduce as many extra or " consequent " poles (as they are styled) as we please, bearing in mind, however, that every two north or every two south poles will be separated by a south or a north pole, as the case may be, and that July lij, 1884.] KNOWLEDGE 69 between every two poles there is a region of neutrality — neutral, not in consequence of the absence of magnetism, but because the two poles are opposite and equal. We are furthermore accustomed to say, and that truly, that the two polarities in any magnet are equal, and for this, if for no other reason, neiiher of the north poliuitics (Fig. 3) can equal the south polarity. Were we able to eliminate every modifying influence, we should tind that the sitigle south pole equalled in strength the sum of the two norths. These effects may be easily and efl'ectively obtained by coiling a little wire around a knitting-needle and sending a current through it. The needle being steel, it will retain the magnetism induced, and by placing its various parts in in the neighbourhood of one or other of the poles of a sus- pended or floating magnet, experimental confirmation of its assumed magnetic condition may be afforded. Supposing, in the next place, that our battery-power is limited, and that the effect jiroduced by sending the current through a single helix (such as Figs. 1 or 2) is incapable of performing a certain task, the question arises : How are we to increase the magnetic effect exerted upon the iron with- out submitting to a corresponding increase in the battery- strength ? This may be attained by increasing the coil of ■wire, or, in other words, by increasing the number of turns or loops. Presuming the coil to be closely wound, it is only possible to increase the number of turns in a single helix by using a thinner wire. It must, however, be borne in mind that by so doing we shall materially raise the re- sistance in circuit, and consei[uently cause a proportional diminution in the strength of the current traversing it Thus, supposing that we substitute a wire half the diameter of that previously used, we should be able to envelope the core with, approximately, twice the number of rings or loops. This means twice the length of wire ; and the resistance offered by a piece of wire varies directly as its length — or, more simply, twenty yards of wire offer twice the resistance that would be presented by only ten yards. But this is not all, for resistance also varies inversely as the cross section, which is the same as saying that it varies inversely as the square of the diameter. Now our thinner wire has only half the diameter of the other, or their diameters are as 1:2, the squ.ires of whicli are 1 and 4. Thus, for equal lengths of the thin and thick wires the respective resist- ances will be 4 and 1. Bvit it was said that the iron core ■would carry twice the length of thin wire, so that the resistance of such a helix would be eight times as great as the one composed of the thicker wire. The effect upon the current-strength is easily seen. Suppose we have two cells giving an electro-motive force of two volts, and having an internal resistance of 1 ohm per cell. Then, with the stout wire helix having a resistance of, say, 1 ohm, we get, according to Ohm's law (which declares that the current produced varies directly as the electro-motive force (E), and inversely as the total resistance, including that of the battery (r) and of the external circuit (E)), ^=-l-:=l-3. R-t-r l-f2 And with the thin wire helix (having eight times the resistance of the other, and therefore offering 8 Ohms) ■we get : — _^ = ^ = -4. R-f-r 8-f2 The bearing of these figures in demonstrating that in the second case we get less magnetic force developed than in the first case may be readily seen, and will be dealt with next, (To be continued.) OTHER WORLDS THAN OURS. A WEEK'S CONTEESATIOX OX THE PLURALITY OF WORLDS. By Mons. de Fontenelle. with xotf.s by richakd a. proctor. {Continued from p. 44.) " A LL philosophy," said T, " madam, is founded upon JrX. two things, either that we are too shortsighted, or that we are too cuiious ; for if our eyes were better than they are we should soon see whether the stars were worlds or not ; and if, on the other hand, we were less curious, we should not care whether the stars are worlds or not, which, I think, is much to the same purpose. But the business is, we have a mind to know more than we see. And, again, if we could discern well what we do see, it would be too much known to us ; but we see things quite otherwise than they are. So that your true philoso]iher will not believe what he does see, and is always conjectuiing at what he does not, which is a life, I think, not much to be envied. Upon this I fancy to myself that nature very much re- sembles an opera ; where you stand, you do not see the stage as it really is, but as it is placed with advantage, and all the wheels and movements are hid, to make the repre- sentation the more agreeable. Nor do you trouble your- self how or by what means the machines are moved, though certainly an engineer in the pit is aflected with what does not touch you ; he is pleased with the motion, and is demonstrating to himself on ■what it depends, and how it comes to pass. " This engineer, then, is like a philosopher, though the difficulty is greater on the philosopher's part, the machines of the theatre being nothing so curious as those of Nature, who disposes her wheels and springs so out of sight that we have been long a guessing at the movement of the universe. Suppose, then, the sages to be an opera — i.e., Pythagoras, Plato, Aristotle, and all the wise men who have made such a noise in the world for these many ages ; we will suppose them at the representation of Phneton, where they see the aspiring youth lifted up by the winds, but do not discover the wires by which he mounts, nor know they anything of what is done behind the scenes. Would you have all these philosophers own themselves to be stark fools, and confess ingeniously they know not liow it comes to pass ? No, no, they are not called wise men for no- thing ; the', let me tell you, most of their wisdom depends upon the ignorance of their neighbours. Every man presently gives his opinion, and how improbable so- ever, there are fools enough of all sorts to believe 'em : One tells you Phaeton is drawn up by a hidden magnetick virtue, no matter where it lies ; and perhaps the grave gentleman will take pet if you ask him the question. Another says Phaeton is compos'd of certain numbers that make him mount; and, after all, the Philosopher knows no moie of those numbers than a sucking child does of Algebra. A third tells you. Phaeton hath a secret love for the top of the theatre ; and, like a true lover, cannot be at rest out of his mistress's company ; with an hundred such extravagant fancies, that a man must conclude the old sages were very good banterers. " But now comes Monsieur Descartes with some of the moderns, and they tell you Phaeton ascends, because a greater weight than he descends ; so that now we do not believe a body can move unless it is push'd and forc'd by another body, and as it were drawn by cords, so that no- thing can rise or fall but by means of counter-poise ; to 70 KNOWLEDGE ♦ [Jdlt 25, 1884. see nature, then, as she really is, yju must ttaml behind the scenes at the opera." " I perceive," said the Marchioness, " philosophy is now become very mechanical." "So mechanical, madam," said I, " that I fear we shall quickly be ashamed of it ; they will have the world to be in great, what a watch is in little, which is very regular, and depends only upon the just disposing of the several parts of the movemeut But pray tell me, madam, had you not formerly a more sublime idea of the universe 1 Do not you think then that you honour'd it more than it deserv'd 1 for most folks have the less esteem for it since they have pretended t) know it." " I am not of their opinion," said she ; " I value it the more since I know it resembles a watch ; and the whole order of nature, the more plain and easy it is, to me it appears the more admirable." " I know not," said I, " who has inspired you with these solid notions, but I am certain there are i'evr that have them besides yourself. People generally admire what they do not comprehend, they have a veneration for obscurity, and look upon nature, while they do not understand her, as a kind of magic, and despise her below legerdemain, when once they are acquainted with her : but I find you, madam, so much better disposed, that I have nothing to do but to draw the curtain and shew you the world. " That then which appears farthest from the earth (where we reside) is called the heavens, that azure firmament, where the stars are fasten'd like so many nails, and are call'd fix'd, because they seem to have no other motion than that of their heaven, which carries them with itself from east to west. Between the earth and this great vault (as I may call it) hang at different heights,* the sun, and the moon, with the five other stars, Mercury, Venus, Mars, Jupiter, and Saturn, which we call the planets : these planets, not being fastened to the same heaven , and having very unequal motions, have diverse aspects and positions ; whereas the fixed stars in respect to one another, are always in the same situation : for example, the Chariot, which is com- pos'd of the seven stars, has been, and ever will be,t as it now is, tho' the moon is sometimes nearer to the sun, and sometimes farther from it ; and so it is with the rest of the planets. Thus things appear'd to the old Chaldean shep- herds, whose great leisure produced these first observations, which have since been the foundation of astronomy ; which science had its birth in Chaldea, as geometry sprung from Egypt, where the inundation of the Nile confounding the bounds of the fields, was the occasion of their inventing exacter measures, to distinguish every one's land from that of his neighbour. So that astronomy was the Daughter of Idleness, Geometry the daughter of Interest ; and if we did but examine Poetry, we should certainly find her the Daughter of Love." " I am glad," said the lady, " I have learnt the genealogy of the sciences, and am convinced I must stick to as- tronomy ; my soul is not mercenary enough for geometry, nor is it tender enough for poetry ; but I have as much time to spare as astronomy requires ; besides, we are now in the country, and lead a kind of pastoral life, which suits best with astronomy." " Do not deceive youri^elf, madam," said I, " 'tis not a true shepherd's life to talk of the stars and planets : see if they pass their time so in Astrsea." * The use of the word lieight by the old astronomers where we say distance illustrates curiously the former prevalence of the old idea of a flat earth. — R. P. t The proper motion of the stars had however been ab-eady detected by Ilalley when this was written, and the absolute fixity of the stars and unchangeableness of the constellationa could no longer be asserted. — E. P. "That sort of shepherd's craft," replied she, "is too dangerous for me to learn : I love the honest Chaldeans, and you must teach me their rules if j'ou would have me improve in their science. But let us proceed." (To be continued.) NOVEL TRICYCLES. By JoHS BEO^\TfING, (Chairman of the London Tricycle Cliih.) "V7OT contented with the important improvements he X\ has introduced in rear-steering tricycles', Mr. Piucker is bringing forward a new machine which will in my opinion eclipse all he has hitherto done, and possibly all that other makers have done in this direction. It is well known that Mr. Rucker has for some time made an excellent front-steerer with central gearing. The new rear-steering tricycle is also central-geared, and, with great ingenuity, a single vertical tube is made to carry both the seat-rod and .saddle, as well as the lower chain-wheel bracket and pedals ; and it will shortly be made to carry the steering-rod centrally arranged so as to allow the machine to be open to mount or dismount from it in tlie rear on either side. It is easy to dismount from this machine in front, if it should be found necessary to do so. The machine is very light, drives easily up hills, and is as safe as a hindsteerer can be made ; that is to say, that any person with a few hours' practice can ride down a tole- rably steep hill at the rate of from six to eight miles an hour, and a skilful rider at the rate of from ten to twelve miles an hour, and I think there are very few riders who would wish to do more. There has been a great demand this year for "Tandems," particularly for " Convertible Tandems." Messrs. Hillman, Herbert, i Cooper have produced a new machine of this class, which they have named the " Kangaroo " Tandem. The construction of this machine is very simple. The steering-wheel of a front-steering tricycle is removed, and replaced by the driving-wheel and back-bone of a " Safety" bicycle with a 36 in. driving-wheel, which is geared up by means of chains, so as to run at the same speed as the driving-wheels of the tricycle behind it Of course, this bicycle portion requires no bind wheel, as it is supported by the front part of the framework of the tricycle. The steering is done entirely by the front rider, who should, I think, have also a good break under his control. The machine I saw weighed about 120 lb., but a machine could, I should suppose, be made for careful riders to weigh less than 100 lb. if it were required. The " Kangaroo " Tandem possesses several important advantages over most other tandems. The riders do not sit so close behind each other as to look uncomfortable. The machine is light. It can have two breaks instead of relying upon one. It has no small steering-wheel, and thus has less friction and less vibration than those machines which have, and, with the addition of a small hind wheel to the front portion, it can be converted in a few minutes into two complete machines, i e., an excellent safety bicycle and a first-class front- steering "Premier" tricycle. Mr. Rucker has just completed for me one of his new two-chain two-speed machines, to my own specification. It is the most perfect front-steering machine I have yet ridden, answering in every respect my utmost anticipations. As regards speed, I can drive the new " Rucker" quite as fast as what I have been accustomed to regard as my inimitable little " Humber," for I have ridden three miles July 1884.] . KNOWLEDGE * 71 in a quarter of an hour on the main Brighton road between Crawley and Reigate ; and I have also ridden 15 miles of rather rough and hilly by-roads at the rate of nearly 10 miles an hour. Probably I should not be able to maintain the same steady rate of speed as I can on the " Hnmber," because the " Rucker " weighs full 25 lb. more than the " Humber," and weight tells in time. But the low-speed, or hill-riding gear, will give the heavier machine a great advantage. My "Humber" is geared to 48 in., the same as the high gearing of the " Rucker." On this, after I have ridden from 30 to 50 miles, hills begin to tell upon me if at all steep. With the " Rucker " I can drop down to the low gearing, which is about .33 in., and get over a stiff hill without any particular strain. This will allow me to ride much farther without getting tired than I should be able to do if I were compelled to keep riding always with the high gearing. The pace at which I can drive the new machine I believe to be due partly to the fact that I can ride it with the saddle farther in front of the pedals than I can on the " Humber," on which, though I ride almost leaning against the handle-bar and with my legs occasionally quite touching the axle (on this point I am quite certain) I yet feel that I should like to be farther in front of my pedals. I fear that some of my readers will come to the conclu- sion that with me the last machine is always the best. Lest this should be thought the case, I would beg to point out that for each machine I order I draw the specification so that it shall avoid disadvantages I have experienced with previous machines, and possess special advantages of its own; and again, that I am precluded from saying anything here about machines I have tried and found wanting, as the publication of such remarks might cause serious inconve- nience to the editor. The new Rucker has driving-wheels only 38 in. in diameter. In my next article I shall give the results of my expe- rience with other small-wheeled machines which I have been riding this season. * # * * Since writing the above I have ridden fifty miles with ]\Ir. Arthur Salmon, one of the fastest riders in my club, for the purpose of testing the new machine. I rode from Reigate to Merstham, on through Redhill and Bal- combe to Cuckfield and Lindtield — a series of hills ; then returned over Hand Cross Hill to Crawley, back through Redhill to Reigate. After riding about forty miles over this series of hills, I covered the ten miles from Crawley into Redhill, without making any perceptible effort, within an hour. THE INTERNATIONAL HEALTH EXHIBITION. IX.— WATER AND WATER-SUPPLIES— (coTi/iinied). THE quality popularly termed " hardness " has been most appropriately chosen to designate waters which offer a peculiar resistance to the sense of touch ; it is a harsh or rough feeling when compared with the smooth gliding sen- sation experienced by the use of rain, or, as it has been called, " soft " water. The hardness is due to the presence of dissolved mineral salts, more notably to the carbonates and sulphates of lime and magnesia. It becomes distinctly appreciable when those salts obtain in quantities of over three or four grains in each gallon ; and, in technical operations, it is customary to speak of the degrees of hard- ness in water, as determined by the " soap test." The unit of hardness is represented by the maximum amount of curdiness produced by one grain of chalk per gallon of water when soap is usetl. It is thus evident that before soap can be made available as a detergent, when used with a hard water, a certain amount is destroyed or decomposed by the substances which produce that hardness, and the waste so occasioned is directly proportional to the hardness of the water. We have now reviewed all the most important factors which bear upon natural water-supplies, with the single exception of upland surface waters, excellent examples of which are to be found in those which feed the rivers and lakes of Cornwall, Devonshire, Northern England, Wales, and Scotland. In all the districts just enumerated, the gathering grounds are chiefly formed of igneous and metamorphic rocks and sandstones. The water thus differs widely from that which we considered in our last com- munication, in being characteristically soft. The upland waters of the Millstone Grit and non-calcareous parts of the Coal Measures, which supjily portions of Yorkshire and Lancashire, are also particularly soft. But there are other British upland waters, which are decidedly calcareous ; they are derived from the limestone and other formations which include the basins of the far-famed Trent, the Tyne, Mersey, Wear, Tees, Tweed, Forth, and Clyde. All these upland surface waters, however, are more or less tainted with harmless colouring matters and objectionable odours. These undesirable items are due to their percolation throughout superficial layers of the peat derived from the decayed remains of successive growths of shrubs, heather, grasses, mosses and other cryptogamic plants. Lastly, the influence of man and other animals upon the water-supply demands our attention. The words guano- mounds, kitchen-middens, cesspools, and sewage are all suggestive of the presence of the " lords of creation " ; but when we come to churchyards and cemeteries, it seems as though modern civilization had undergone a process of retro- grade development. The refining influences of our social system have their drawbacks : they foster feelings which in themselves are noble in the ideal, but are too often proved to be practically pernicious, and even ghastly, in real life. In spite of the warnings of able geologists and doctors of medicine, the vast majority of persons in this country prefer to give their friends what they erroneously call a " Christian burial." When the ceremony is over, they little think that they have merely contributed their iota to a hotbed of festering filth, which has been shown over and over again to be only something short of a wholesale system of manslaughter. We have of late come into contact with many gravediggers and undertakers who loathe their trades so strongly, that nothing short of the hard struggle for existence keeps them to their uncoveted employments. How disgusting the disinterment of a leaden coffin, after perchance a lapse of some years, is, is perhaps only known to the few individuals whose unhappy lot is cast amongst the dead forgotten. Let us ask, with Dr. Attfield* :— " How much longer will a misguided sentiment, an ill- guided superstition, or simple ignorance, sanction the poison-breeding process of interment, when the highest religion and the best interests of humanity point to the harmless practice of cremation?" To soothe the feelings of the bereaved, would it not be better and more worthy of their creed to follow the dictates of reason? If they desire to perpetuate the memory of beloved ones, how much wiser, to say the least of it, would it be to erect something of value to their fellow-beings. The drinking-fountain dedicated to Greyfriar's Bobby, iji Edinburgh, might well be taken as an example in this ■ Water and Water-Snpplies," &c., 1884, p. 3. 72 KNOWLEDGE ♦ [July 25, 1884. direction ; and may we not hope that the time is at hand when pestiferous cemeteries, with their gloomy tombs, tablets, wreaths, and misshapen marhle doves, will give place to drinking-fountains, seats for the weary and foot- sore, shelters and food for the houseless, aud health and happiness for all t The evil gases and germs arising from graveyards are only too manifest to those whose duty leads them perpetually to such scenes ; not only does the air become vitiated, but the most serious cause for apprehension is to be souijht for in the drainage. The rain-water cariies the foul products from the atmosphere, and in greater abundance from the soil, into the underground circulation. If the strata happen to slope downwards to a district of water-supply from wells, the latter become perpetual sources of disease. To a less marked extent is the influence of man felt in the deteriora- tion of water through cesspools and pits ; yet they are oftentimes sources of great danger. See Fig. IS, which we avail ourselvfs of through the kindness of Mr. P. A. Maignen. Fig. 18. — Eeproduced from the Tenth Annual Keport of the Massacbussetts State Board of Health. There were twelve cases of typhoid fever among persons using this well water and the house became the centre of infection for a whole neighbourhood. Samples of "Water. We now propose to submit to our readers a series of samples of water, both natural and artificial, with a brief summary of their jtroperties, as preliminary to a sketch of the methods employed to render them valuable for specific purposes. In doing so we shall have occasion to lead them once more to the collections at South Kensington, there to view the numerous apparatus and inventions which have been designed to secure the purification of waters. 1. Natural Waters. — To this category belong the following types : — 1. Ice and snow ; 2. Kain, dew, and hoar-frost ; 3. Marsh and Pond water ; 4. Lake water ; 5. River water; G. Underground water ; 7. Sea water. 1. Ice and Snoiv are characteristic of all regions where the conditions of temperature and atmospheric pressure are such as to maintain the water in its solid forms. It usually obtains thus during wintry seas-ons in the temperate zones, and permanently on mountain snow-slopes and glaciers, at altitudes of from eight to ten thousand feet and upwards above the sea-level, and in the circumpolar areas. Frozen water is, as a rule, almost free from impurities ; and, when liquefied, yields a remaikably pure fluid, in which dissolved mineral salts and suspended solid particles are only acci- dental. Unlike most substances, water expands on cooling. But only between the limits of 39 25° Fahr. and 32= Fahr. ; it becomes frozen, and in virtue of its relative lightness remains on the surface of the water. The lower levels are thus prevented from radiating heat into space, and the warmth so necessary to the maintenance of life is thus retained by the earth. The bracing climate of a mild wintry country is too well known and appreciated by those who live in it to require any comments here. If we were writing a treatise on domestic medicine, we would consider it our duty to devote at least one chapter to ice and snow. In the kitchen, ice is a most desirable luxury ; and in the preservation of diets, we have but to turn for a tangible example to the gridiron of Messrs. Bertram k Roberts, at the foot of the passage leading to the Aquarium in the Exhibition buildings, to enjoy an excellent, well-matured mutton chop all the way from New Zealand. 2. Rain, Dp.v\ and Jfoar-frost. — The properties of these w-aters have already been detailed at some length.* The usefulness of rain-water depends to a very large extent upon its softness and freedom from suspended particles. It is, perhaps, the largest source < f supply of practically pure natural water in existence. Of possible impurities, dust and dirt, leaves and twig>, soot ard at-hes, traces of such acids as hydrochloric, sulphuric, and nitric acids, sulphates, chlorides, and ammonia, besides the gases of the air, are liable to afl'tct rain-water most of all. Dew, the fi'ozen variety of which is termed hoar-frost, generally contains a somewhat larger percentage of soluble and suspended impurities than rain water, which it abstracts from the air. In England, it has been shown that dew possesses 4 87 in 100,000 parts of solid impurity, and about •198 parts of ammonia.! In our remarks upon the forma- tion of dew,! we noted that a deposition of moisture from the invisiVile vapour held in the atmosphere takes place when the moisture-laden medium comes into contact with bodies which are ever so little colder than it is itself ; the exact temperature at which this occurs can be ascertained by means of a little instrument called after its inventor, Uaniell's ether hygroiu'ter, and is termed the dev jioint. On a clear night the leaves of plants, ic, radiate more heat into space than they receive back, and are thus rendei-ed colder than the furrounding air, and, in conse- quence of this, dew is formed ; on a cloudy night, however, the heat is radiated back by the clouds, and the deposition of dew thus curtailed. During the summer months, an immense amount of vapour is taken up by the warm air, and, as the nights are usually clear, enormous quantities of dew are produced and absorbed by the vegetation and surface soils of the earth. This state of affairs is, of course, more pronounced in tropical countries, where the source of water supply through the agency of dew is an all-important factor in the maintenance of the conditions of life during the protracted period of drought commonly called the " dry season." 3. Marsh and Pond Waters are local collections of rain, or, in the neighbourhood of sea-coasts, of rain and spray. They usually harbour vegetable and animal growths and decaying matters; and upon the absence or presence of these, in larger or smaller quantities, does the value of the water entirely depend ; it may thus range from a good, soft water to one which may be described as the essence of contamination. 4. Lake Water may represent the accumulated drainage of a large area which empties into a natural reservoir. The character of the water, which is primarily derived from rain, thus depends wholly upon the nature of the surrounding formations. The water of lakes without efferent streams, generally becomes saline, through evaporation and con- * Vt ^vpra, p. 31, et .'ieqnetites, t "Bivers Pollution Commission," 6th report, p. 32. J See this Journal, p. .3 1. July 25, 1884.] ♦ KNOWLEDGE ♦ 73 sequent precipitation and resolution of dissolved mineral salts, often to a prodigious degree. In the well-known Dead Sea, in Southern Palestine, one gallon of the water weighs about llijlb., or If lb. more than a gallon of ordinary fresh water. Other lakes, as the salt lakes of Utah and Russia, are almost, if not quite saturated solutions ; whilst still others afford a further stage in being destitute of liquid water ; of this character is the borax lake of Cali- fornia. Doubtles.s the presence of mines of salt in this country, Prussia, and elsewhere, point to former lacustrine deposits which have taken place under analogous opera- tions on the surface of the eaith or in vast underground reservoirs. Other lakes are merely expanded portions of rivers, or depressions occasioned by glacial erosion ; and they are commonly provided with both affluent and effluent streams. In such cases the waters are, of course, identical with those of rivers ; their physiographical surroundings, how- evei', make them the recipients ot the first upland drainage, and, as a rule, the water-supjily from such sources is parti- cularly free from impurities. As instances we may point to the waters of classic Loch Katrine, with its " silver .strand " and " Helen's Isle," and of Thirlmere, in Cumber- land ; they contain only about two grains of solid impurity in each gallon. 5. Hiver Water. — Enough has been stated with regard to the sources of the Thames water to afford a typical example of what may be expected from a river-supply of water. 6. Underground Waters furnish us with by far the most extensive supply in the world. Wo must once more refer our readers to our foregoing remarks, from which they will gather that rivers and lakes are very largely augmented, and that springs and wells are wholly derived from subter- ranean sources. A species of intestine warfare seems to be perpetually carried on between the pure and impure varie- ties of this element beneath the surface of the earth ; and, on the whole, a kind of equilibrium is established. Surface- waters which become contaminated by their passage through dissolvable soils and rocks, are operated upon by the counter effects of internal heat and other agencies ; they are com- pelled to give up portions of what they have taken, and may thereafter find an escape to the surface of the eaith, from which they originally came, considerably })urified. On the other hand, they may reappear surcharged with the substances they have collected on the way. As a rule, however, the tendency of extensive underground circulation is to render the water purer in the sense of its becoming more valuable to man, and these changes are chiefly brought about through the oxidation or destruction of harmful organic matters, which may accrue from sewage, grave- yards, abundant manuring, decaying vegetation, kc. 7. Sea Water occupies but a subordinate place in ordi- nary domestic economy. Its saline character is chiefly due to the continued accession of dissolved salts from the earth, which are brought to it by rivers, and which remain behind in the water whilst evaporation is constantly going on from its surface. As a bath, sea-water is often more invigorating than fresh water. In the vessels of the British Navy, and in many recently-built crafts, the waste steam from sea water is utilised by condensation, aerated, and used for drinking and culinary purposes. If a quantity of fresh water be represented by a weight of 1,000 lb., an equal volume of sea water would weigh 1,027 J lb. In consequence of this the boiling point of sea water is much higher than that of fresh water, because an additional amount of heat is necessary to overcome the adhesion between the water and the saline matters. (To ie continued.) THUNDERSTORMS. THIS is a topic to which we shall, when an opportunity presents itself, have occasion to refer with a view to demonstrate that it is possible to guard against such annual calamities as frequently accompany lightning discharges. On the three closing days of the week ending July .5 thunderstorms of more than ordinary violence passed over England and Scotland, lieports show considerable loss of human life and destruction of property. The storms were accompanied by heavy showers of rain and hail. Some of the hailstones, when ]iicked u|), were found to measure seven-eighths of an inch square, and weigh over two penny- weights. Subjoined i-j a summary compiled by a con- temporary of the effects produced in England and Scotland. England. Aslon, near WalUnriford. — Two men, while working in a field, were killed. Their clothing was completely con- sumed. A horse in the neighbourhood was also killed. Burnley. — Two men were seriously injured. Liverpool — At Holy Trinity Church the lightning passed through the roof and through the gallery floor, filling the building with a pale blue flame. The current passed between two boys, paralysing the arm of one and scorching the boot ot the other. The bell was rendered useless, and coping stones were hurled some distance. Peterborough. — A number of sheep and cattle killed. Weardale. — Wesleyan Chajiel struck, and two men at work on the spire were knocked down insensible, but recovered consciousness afterwards. At Burn Hope a house was partially destroyed. Xorthampton. — Lightning struck several dwelling-houses, demolished the turret of a shoe factory, and injured a girl. Wymeswood. — Three men, who were at work in the hay- field, took shelter under a hedge. One of the men felt a sharp pain on his thigh, and became insensible. On recovery he found that one of his companions had fallen, while the other was sitting, looking placid and ajiparently undisturbed ; but on examination he found both were dead. Skipton. — Tree struck and cut, and a cartload of hay which was being put into a barn set on fire. Wimiham. — A stable on the farm of Sir Brook Bridges was struck by lightning and set on fire, three valuable horses being burnt to death. Cambridge. — A woman was killed and several buildings were struck by lightning, Deddington. — A painter was killed whilst sitting under a tree during a thunderstorm. Consett. — Whilst nursing an infant on his knee a miner was struck by lightning and killed, the child escaping. Scotland. Ilamilton. — The storm, which was at its height about half-past one, continued for fully two hours. About half- past one o'clock, what is described as a ball of fire burst over the Clydesdale Bank, a large three-storey structure in Cadzow-street. The lightning struck the chimney head, racking and displacing the solid stonework, and passing, it is believed, down the chimney. The consternation of the inmates, including the ofiioials of the bank, may be con- ceived. In the room with which the vent communicated, the grate was thrown out on to the floor, and the apart- ment filled with soot, plaster, and debris. Something similar happened in the room on the second floor. The bank otiioe is immediately below on the street floor. The accountant was startled by the noise and falling debris. 74 • KNOWLEDGE ♦ [July 25, 1884. Mr. Lightbody, who was standing inside his shop door on the opposite side of the street, was almost knocked oil' his feet against the side of the door. His workmen in the bakehouse behind thovight the premises had been struck, and the beam and scales were knocked against the wall. The tailors in Mr. Park's workshop, which adjoins the bank, felt stunned, and thought their skylight window had been struck. Three independent witnesses standing in the neighbourhood at the time state that they noticed a ball of fire momentarily suspended over the bank. Lockerbie. — Several houses struck and their roofs damaged. KUhirnie. — Two houses damaged ; the lightning passing from the one to the other. Beith. — Intense darkness accompanied the storm, and business had to be suspended for fully an hour, during which time flash succeeded flash at intervals of four minutes. Ardrossnn. — The most severe storm ever experienced. The flashes of lightning were vei-y vivid, and the peals of thunder sharp and loud. Hailstones, weighing over two pennyweights, and measuring three-quarters of an inch in circumference, were picked off the streets. Saltcoats. — Two houses struck, and their gas-pipes cut in two. Kirkintilloch. — The lightning entered the room of a house, passed along the attics and out by the chimney, shattering the plaster and chimney top. Rothesay. — Valuable milch cow killed. Yale of Leven. — Darkness intense. The flashes of lightning very vivid, and the peals of thunder, which were loud, continued from ten to twenty seconds. Slonehouse. — Hailstones of large size, vivid lightning, and a series of tremendous sharp, and prolonged peals of thunder. Cow killed and a tree struck. Neinnilns. — Thunder peal followed thunder peal in rapid succession, and sometimes three of them were heard at the same time. Outside stair and belfiy of the Council Chambers damaged. Loans. — Two cows and a bull killed. Sinclairtovn. — Dwelling-house struck, followed by an explosion of gas ; damage not serious. Stack of hay set on fire and completely destroyed. Kirkcaldy. — Ventilator at the top of malting kiln at Gallatown struck, and one of the large beams supporting the ventilating apparatus shattered, some of the splinters being carried away a distance of about 200 yards. In a private house a valuable picture was destroyed, and the woodwork set on fire. Stardey. — A house was set on fire, and a portion of the structure knocked down on two women, rendering them insensible for a time. Slow. — Eight sheep instantaneously killed, and a ninth had to be afterwards destroyed. Haivick. — The storm lasted for upwards of two hours, and so dark was it that gas had to be lighted. The lightning entered two houses and damaged a number of articles. Girvan. — Several cattle killed. Bushy. — The lightning was most brilliant and vividly coloured, blue in many instances. From three to four flashes were seen before thunder heard. Three girls em- ployed in Busby Mills fell into a state of fainting, and remained in a trance for several hours. A cow grazing in a field was killed, its hide being singed. A building in the printworks was stripped of the lead and slates. Ayr. — The lightning very bright and the thunder almost incessant. Several of the flashes were of a violet tinge. Some little panic was created in Ayr woolworks by the girls getting frightened at the lightning gleaming on the spindles. I^eith. — The lightning entered a house, ran round the cornice of a room, teaiing it open. The window-curtains were set on fire, the roof singed, and a number of articles which were lying about damaged. The lightning escaped through the window, scorched the framework, and smashed several panes of glass. A gentleman sleeping in the room had a very narrow escape, as the lightning in its course went within a few feet of his head ; he was much shaken. After leaving the house the lightning had, judging from a quantity of plates dislodged, run down the outside of the house and entered the earth. Edinburyh. — The Scotsman says : — " Just as the btorm began, one of the telegraph clerks in the Scotsman ofiice had a narrow escape from being injured by the lightning. Word had come over his wire that the House of Commons had been counted out at 2.30 a.m., and he rose from the Morse instrument to carry the sheet into the adjoining sub- editor's room. As he re-entered the telegraph room a loud rei)ort like the discharge of a rifle was heard, and the thick glass cover of the relay was blown several feet into the air, and smashed one of the glass globes. The relay was completely destroyed. DuiiiJ'riessliire. — Reports give accounts of considerable destruction of farm stock. Mr. Phillips, Clarencefield, had two fine bullocks killed, Mr. H. Baird, Blackford, had one killed, and Mr. Aitken, a farmer in the parish of John- stone, had sixteen sheep killed. While a lad was harrow- ing turnips in a field the lightning struck the ground in the next ridge, and covered him with earth, and a man leading a horse bad a very narrow escape, he having just passed when a large tree was struck and thrown across the road. Heavy rain accompanied the storm. Arisaig. — Mr. Lewis Macdonald (28 years of age), crofter, Ardnish, was on the hill above the croft, taking home the cattle at about 4 p.m., on Friday last week, when he was stioick with lightning and killed instantly. When found it was discovered that there was a mark like a bullet hole on the right side of the head above the ear, and from the appearance of the body it is evident that the electric fltiid struck his head first, and then passed through his body. Appin. — There were several extremely vivid flashes of forked lightning passing straight down from a dense cloud overhead to the earth. Four sheep were struck by lightning and kOled ; and altogether the storm was one of the most severe remembered for some years. Errata. — P. 57, col. 2, line 8 from bottom, " now tired," shoald be " never tired. P. 60, letter 1340, line 1, " absence of home " should be "absence from home." Eaixfall Eecoeds at Glasgow Obsekvatoet.— On the authority of Professor Grant, F.E.S., some interesting rainfall records at Glasgow Observatory have been made available for public use. Their publication was suggested by the heavy rainfall at Glasgow during the twenty-four hours ending at ten o'clock on the morning of the 11th inst., which is said to have been the most excessive that has occurred during the past twenty-two years. The downpour was heralded by a smart shower which commenced abont 1 p.m. on the preceding day (Thursday), and lasted but a few minutes, when fair weather was again enjoyed for about an hour. A little after 2 p.m. there was registered by the self-recording instrument of the observatory, a drenching shower, which, although happily shortlived, was remarkable for the rapidity with which it fell. At 4.15 p.m., the sky, which was destitute of sunshine for several hours previous, again sent down rain in perfect torrents. During the evening, 1 in. of rain fell in five hotrrs. During the twenty- hours referred to, the rainfall amounted to 2'12 in., and during none of the twenty-two years preceding 1884 did the rainfall at Glasgow Observatory ever exceed 177 in. in the same period of time. That was in the month of July, 18G6. — Engineexin^. July 25, 1884.] KNOWLEDGE 75 iKtblfttJS* SOME BOOKS ON OUR TABLE. TextBook of Descriptive JRneralor/i/. By Hilary Bauer- man, F.G.S. (London: Longman?, Green, &: Co. 1884.) — In his volume on " Systematic Minei'alogy," in Messr.s. Longmans' admirable series of " Text-books of Science," which preceded the one whose title heads this notice, Mr. Bauerman considered the methods followed in the systematic determination of the form, structiire, and com- position of minerals, and he now proceeds to apply such determination to the description of every important species known. This is done in a way as convenient aud intel- ligible to the student as it well can be, and no less than 203 woodcuts of crystalline forms illustrate the text. It is curiously illustrative of the advance of mineralogical science that the capital index (of the names of minerals alone) with which ^h: Bauerman's work con- cludes occupies twenty closely printed columns. Simjile Lessons in Water-Colour : Jlariue. By Edward Duncan. (London : Blackie it Son.) — In no more agree- able form can reminiscences be secured of a holiday tour than in that of water-colour sketches, made by the tourist himself, of the localities which he has visited ; and the sea- coast will always supply him with a boundless variety of subjects for his pencil. Mr. Duncan's book will furnish him with all needful infoi'mation as to the best method of reproducing the various forms which he will meet with, and the atmospheric effects which add so much to their charm and beauty. The pos.session of a box of moist water- colours, a sketch-block, and this volume of" Simple Lessons" will add a new and very real pleasure indeed to a visit to the sea-side. Tea and Tea-Drinking. By Arthur Reade. (London : Sampson Low, Marston, A- Co.) — Mr. Reade, who is very keen and enthusiastic indeed about tea, does his best, and far from unsuccessfully, to interest the general reader in the same subject. Beginning with its introduction into this country in 1610, and tracing the gradual spread of its use, he goes on to describe its growth and preparation, teaches us how to make it, discourses on its effects on physical endurance, its employment as a stimulant, and winds up with some details of the extent to which it is a source of revenue. The book is both chatty and amusing, and will while away an idle half-hour pleasantly enough. Jolin Bull's Neiglthour in her True Light. By a "Brutal Saxon." (London : Wyman i Sons. 1884.)— How far what may be termed an International " Slanging- match " is a seemly or edifying spectacle, must be left to the judgment of individual readers. Within a comparatively recent period, however, certain French writers have taken upon themselves to revile and vituperate England and the Enelish in a manner which was certain sooner or later to o provoke reprisals. That the inhabitants of these islands are faultless, either morally or socially, it would be idle to con- tend ; that, however, on the other hand, we are the besotted, debauched, ignorant poltroons depicted by some of our highly-imaginative neighbours across the Channel, it would be equally idle not to deny. Stung, then, apparently by taunts as baseless as they are brutal, our author, who seems to be an English resident in Paris, has set himself to let a little light in upon Fi-eneh life, social and official ; and a most melancholy expose he gives us of ghastly immorality, filthiness, bragging, cowardice, and venality on the part of our critics. The " Brutal Saxon " is, at any rate, both eadable and amusing, and probably liy this time MM. Max O'Kell," Hector France, et Cie, are (like Lord S haftesbury's parrot) "sorry they spoke." The Straight Line and Circle. With a Chapter on the other Conies. By A. Le Sueur, B.A. Cantab. (London: Bailliere, Tindall, i Cox.) — This handy little rudimentary book on Analytical Geometry and the Conic Sections will be found useful to the student preparing for examination. A very excellent feature in ]Mr. Le Sueur's work is the insertion after the proof of the various formulae, of exer- cises, in the shape of numerical applications of them. Nothing, in our experience, appeals so immediately to the mind of the beginner as a concrete numerical example of a merely literal equation, and such examples are supplied in abundance in the book before us. General ones are also given at the ends of the chapters on the line and circle, as well as the questions set at the London University Exami- nations for the B.A. and B.Sc. degrees from 1840 to 1883. The author has done his unpretentious work well. The Blonplpe in Chemistry, 21ineralogg, and Geology. By Lieut.-Colonel W. A. Ross, R.A., F.G.S. (London : Crosby Lockwood rison sketches and notes will be commenced in eade, well known as the author of the " Literary Ladder," " Study and Stimulants," "How to Write English," Ac. The popularity which these several works have enjoyed entitles one to anticipate an equally favourable reception for the present series of articles, which have, moreover, had the benefit of revision by a number of leading journalists. Australian Timber. — A Board appointed to inquire into and experiment on the I'cst kind of timber grown in the Australian colonies, and adapted for the construction of railway vehicles, has. sent in its report. Among the woods which the Commissioners mention as suitable are blackwood, mountain ash, bluegum, arui Gippsland mahogany. Under test the blackwood presented results which were superior to any other timber. The mountain ash was second to the blackwood for railway purposes. It should be felled, the Commissioners think, daring the winter months, when it has attained maturity, and is between 4 ft. and 5 ft. in diameter, and ic might remain felled for six months before being broKen down into planks for seasoning. Bluegum should be treated in the same manner. Going somewhat beyond its reference, the Board deals with the question of timber licenses, and recommends that getters be compelled to pay for the timber felled, and to confine their operations to a given area, or otherwise that selected lots of trees be sold by tender. It is also strongly recommended that a forest, board should be called into existence. [The above, taken fromi Engineering^ serves to show that the continually-increasing demand for timber is causing considerable anxiety, not only in Europe and America, but in every quarter of the civilised world.] A VALUABLE contribution to the literature of physical astronomy * has recently been made in the issue by the Bureau of Navi- gation at Washington of Parts I. and II. of Vol. II. and Part I. of Vol. III. of " Astronomical Papers prepared for the Use of the American ' Ephemeris and Nautical Almanac' " In the first of these parts the formtJa> necessary for expressing the corrections to the geocentric right ascen- sion and declination of a planet are deduced in terms of cor- rection to the elements ; the expressions thus obtained being deduced to numbers for the planets Mercury and Venns, and tables for those two planets respectively being appended. The second part of Vol. II. contains investigations of corrections to the Green- wich Planetary f)bservations, 1762-1830; and, to the general reader, will probably be found the most interesting of the three, if it be only for the succinct history of the instruments employed at * We use these words in the original and legitimate sense, and by no means in the modem one of watching snnspots to predict rain and periods of stock- jobbing insolvency. July 25, 1884.] ♦ KNOWLEDGE ♦ 77 our British National Observatory (and tlio nature of their errors) during the period specified. Part I. of "Vol. III. of these " Astro- nomical Papers" is purely technical, and is " On the Development ot the Perturbativo Function." In it the subject is first treated analytically in an exhaustive manner, and the tables are appended for the numerical development of it. It is instructive to com- pare the lilieral and judicious expenditure of the Government of the United States in perfecting their National Ephemeris, with the parsimony of that of onr own country in connec- tion with our Nmitical Almanac];, in which, to take a single example, the phenomena of Jupiter's satellites are still computed from the imperfect and erroneous tables published by Damoisean nearly fifty years ago. This will serve as well as anything to illus- trate the merely mechanical — or bari'el-organ — kind of principle on which the annual calculations are ground out in Verulam Buildings. Meanwhile, any one who is sufficiently pushing and impudent, and can obtain the ear of members of the Government personally ignorant of science, seems to have no difficulty in dipping his hands into the public purse. If the money, absolutely and utterly wasted every year on a shallow sham called " The Committee on Solar Physics," at South Kensington, were devoted to the improvement of the Nautical Almanack, the advantage to astronomical science could hardly fail to be very great indeed. " Let Knowledge grow from more to more." — Alfbed Tenntsob, Only a small proportion of Letters received can possiily be in- serted. Correspondents mimt not le offended^ therefore^ should their betters not appear. All Editorial communications sho^dd ie addressed to the Editor of Knowledge; all Business communications to the Publishers, at the Office, 74, Great Queen-street, W.C. If this is not attended to DELAYS ARISE FOR WHICH THE EDITOR IS NOT RESPONSIBLE. All Remittances, Cheques, and Post Office Orders should he made payable to Messrs. Wyman & Sons. The Editor is not responsible for the opinions of correspondents. No communications are answered bt post, even though stamped AND DIBECTED ENVELOPE BE ENCLOSED. DICKENS'S STORY LEFT HALF TOLD (No. 139). [1343] — Being the writer of what Mr. Thomas Foster calls " a recent rather feeble article on the subject in the Cornliill Maga- zine," I should like, with your permission, to make a few observations. Not having read " Leisure Keadingn," I am not well aware what Mr. Foster's theory really is, and should therefore be glad to leam in what number of Knowledge his former article on this subject appeared. Until I have had the pleasure of reading it, I will only ask whether Mr. Foster lias seen the article, " How Edwin Drood was Illustrated," which appeared in the Century Magazine for February, 1884 ? From that I quote the following few sentences : — " The central crime of the book can never have been intended by the author to be a mystery ; the secret that Charles Dickens intended to keep, and kept in effect, was the manner of the discovery. He is a keen reader who has ever found out who and what was Mr. Datchery, and of this Mr. Fildes knows no more than does the public." " But, finding that Mr. Fildes knew a great deal, Charles Dickens went on to make the principal revelation which concerned the central figure ; he told his illustrator that Jasper was to be brought to justice in the end of the story. A drawing of this originally and most strongly-conceived criminal locked up in the condemned cell (which was to have been studied at Eochester) was then planned between the two as one of the final subjects." Mr. Foster contends that Edwin Drood is alive, though Jasper does not know it. That he should keep his very existence a secret for six months — causing terrible grief to Rosa and others — for the purpose of taking a deadlier vengeance in the end on Jasper, does not, I confess, appear to me reasonable ; but then I suppose I am what Mr. Poster calls " a commonplace reader." In conclusion, I may mention that I received letters from two gentlemen — both strangers to me — insisting that Baggard is Datchery. One wrote from Boston, U.S., the other from Jersey. But on tins point I agree with Mr. Foster, and differ from my cor- respondents as widely as their homes are distant. H. E. [As Mr. Foster is, I imagine, by this time on the other side of the Atkntic, a fortnight or three weeks must certainly elapse before I can receive anv reply or comment on the above letter from him. —Ed.] ■ THE SOLAR GLOW.— VENUS IN INFERIOR CONJUNCTION. [1344]— In connection with the letter (1342, p. 61) of " Cosmo- politan," it may be of interest to mention that I have received a letter from that careful and painstaking observer, Mr. T. E. Clapham, of Austwick Hall, near Lancaster, describing the appear- ance of the solar glow as seen by him on the 12th inst. It was (naturally) most favourably seen when the sun himself was obscured by a cloud, leaving the surrounding sky clear. Under these circum- stances, the ruddy glow seemed very approximately to follow the outline of the cloud; but there was also one fine reddish streamer, with almost parallel edges, above the cloud ; in shape, exceedingly like one of the beams of light visible when, as the country people say, " the sun is drawing water." This is illustrated by a water-colour sketch, which could not, of course, be reproduced here in colour. My correspondent goes on to say that the after- glow was stronger on the night of July 13 than he had known it for some weeks. Assuredly there is something still permeating the atmosphere in its upper regions. Mr. Clapham adds that at lOh. 30m. a.m. on Saturday 12, he could easily see the dark body of Venus with a 3i-iD. Wray tele- scope ; but that he could not trace the dark limb right round. I mention this because on the previous day at lOh. 41m. a.m., I saw precisely the same thing with my 4"2 in. Ross equatorial, armed with a power of 154 ; the dark limb of the planet being traceable for a considerable distance beyond the cusps, but fading into the bright sky in its southernmost portion. WiLLUJI NoBLE. Forest Lodge, Maresfield, Uckfield, July 18, 1884. THE "WAR OFFICE GHOST." [1345] — I take the following particulars from Wallace's " Miracles and Modem Spiritualism," pp. 72-3, where I happened to read it yesterday. Captain Wheatcroft's "ghost" appeared, not only to his wife — who by the way was in bed at the time — but to another lady, in London. On inquiry, R. Dale Owen (from whose narrative Wallace draws most of his facts) gathered from this lady and her husband that it was about 9 p.m. of Nov. 14, 1857, that the spirit appeared in uniform. He was struck b}- a fragment of shell, it seems, in the breast, on the afternoon of the 14th, not the 15th, as the War Office certificate first put it. The times, therefore, are within the limits required on the assumption, which is quite unnecessary, that the apparition occurred simultajieously with the death. If anything really hinged on the exact synchronism it might be worth while to make more minute inquiries as to the circumstances of the Indian battle-field. But I really see none. It is quite sufficiently con- vincing as it is, so long as nothing essential is authoritatively denied. J. Heescuel. [Mr. R. Dale Owen can scarcely be accepted as a trustworthy authority on anything whatever having reference to the " super- natural." Readers interested in the spiritualistic imposture will not have forgotten his famous article in the Atlantic Monthly, on the bona fides of the apparition of " Katie King," through the niediumship of a Mr. and Mrs. Nelson Holmes; nor his subsequent humiliating confession of the way in which those people had humbugged him. If Mr. Wallace has no better voucher for his "facts" than Mr. Owen, assuredly they must be taken with something more than a grain (say a salt-cellar full) of salt. — Ed.] A COINCIDENCE. [1346] — In May last, a friend mentioned to me in conversation a poem by the late Dean Stanley, entitled " The Untravelled Traveller," and addressed to Prince Leopold on the latter's reco- very from a severe illness at Oxford. I had never seen or heard of the poem before, and my friend, who was extremely anxious to procure a copy, begged me to let him know if I ever met with it, as he did not know where it was to be found. We then spoke of other things, and no fui'ther allusion was made to the subject — in fact, I quite forgot it till the next morning, when, quite casually taking up a small monthly magazine (which, by-the-by, I seldom 78 ♦ KNOAVLEDGE ♦ [July 25, 1884. read) from my sister's writing-table, almost the first thing that met my eye was a reprint of this very poem. It would have been the last place I should have thought of looking in. Ardennes. PERSPECTIVE. [1347] — Some of your corre.=!pondents seem to have got into a puzzle over their perspective. They seem to find a ditiiculty in understanding how parallel lines perpendicular to the line of sight — that is, lying in planes parallel to the plane of the picture, can be correctly presented to the eye of the spectator by parallel lines on the plane of the picture. Your correspondent " C. E. Bell " seems to forget that, although the upper and lower edges of the cube may be shown by parallel lines in the picture, yet the angle subtended with the eye by the perpendicular edges of the cube varies with the distance to right or left, as the case may be, while tlie edges are from the centre of the picture or line of sight. Thus, if P P in the annexed diagram bo the plane of the picture shown in plan, S, the spectator's eye, and SA, the line of sight, it is obviously seen that a given dimension M on the plane of the picture at A will subtend a larger angle with the eye than the same dimension M at B. Let " R. Jones," " C. E. Bell," and others simply examine the photograph of any rectangular object taken with the plate of the camera parallel to one face of the object, and they will find that all the horizontal lines in the object which arc in planes parallel to that of the plate will appear as parallel lines in the jiietvire. In connection with this subject I woitld remark that artists are in the habit of showing the sea-line as a straight horizontal line. Now this is not strictly correct, and especially when the sea is viewed from a great height. The spectator's eye being a point outside a sphere, may be re- gsurded as the apex of a flat cone, the base of which is a circle whose radius is (approximately), the distance of the spectator from the horizon. If a straight-edge be held up to the eye when looking towards the sea-line from a lofty cliff on the sea-shore, the curvature of the horizon becomes plainly visible. I commend this experiment to crazy Zetetics, though, doubtless, they can explain this as easily as every other fact that tells against them. E. W. Young. [What is " a flat cone " ?— Ed.] SHIPS' LIGHTS. [1348] — Apropos of your propositions respecting ships' lights in " Sent to the Bottom," in a former number of Knowledge, the reduction of the number of lights being most desirable, may I venture to offer for your consideration the following alteration, namely, that tim lights on each side only be adopted, in lieu of three side and two end lights. Thus, let the foremost light be white on each side, and visible from right ahead to right astern, and placed 15 (?) feet from the stcmmost, and 5 (?) feet above that light — the sternmost light to be particoloured — white showing ahead to well abeam, but say red astern to nearly abeatn ; steamships carrying a fifth masthead light as at present. A sketch may make my sug- gestion clearer : — * a. a. a- a a I * J starboard. (White.) Port. (White.) J Ahe (Wh * -A % Jf> M. Jb ad. Astern, te.) (a. White.) (!). Red.) The opening apart of the lights from a perpendicular line, as when seen from " right ahead," to their greatest distance apart, as when seen from " abeam," and their closing again, the lower be- coming red, to their original position, as when seen from " right astern," would indicate the required information as to course of observed ship. The reijulation interval between the lights being invariably adopted, would become by habit easily and surely recog- nisable as representing by their varied proximity the direction and distance of the observed ship. I leave this suggestion with you, as you may in a few moments run over an imaginary series of positions as depicted in your excel- lent magazine, substituting the two lights alone in lien of the five there shown, bearing in mind, at the same time, that ships at sea are not, as a rule, on an even keel or even beam, so to put it. A ship, say 30' — nay, 40° — out of the perpendicular, as often hap- pens, and at a time when lights are most requisite and important, would materially alter the relative length of the perpendicular side of your triangle, and that of each of the other two. I recognise that that upright side forms the gauge by which the apparent lengths of the other two are measured, and so the course of the vessel estimated. What, therefore, are we to do to obtain that information when our gauge or foot-rule is liable to considerable variation from this heeling over of the ship at sea? Let it also be remembered that perpendicular space available for effectively show- ing lights from the side of a ship is very limited. What would our lee triangle be like with our bottom light in danger of entire sub- mersion. The side lights now are carried almost invariably several feet above the top rail of bulwarks for this very reason, and if placed much higher would be eclipsed by the sails. All this, and more, I am sure, will present itself to your mind, and I need en- large no further. My best thanks are due to you for many most instructive and enjoyable hours spent in company with yon in Knowledge from Xo. 1. — I am, sir, &c., Cuas. Rice. TESTS OF DIVISIBILITY. [1349]— In letter 1334 (p. 39) I stated that 999 ... to (m-l) figures can be divided by n without remainder whenever n is prime to 10. I find it is not so. When n is a prime number it will divide 999 .... to (n — 1) figures. When n is composed of uneqiial factors a, b, c, &c., the number of 9's required is (a — 1) (i> — 1) (c — 1) . . . . , or some factor of this. When n contains eqttal factors (= say, o''b'c'' •••-)! the number is a''-'(a-l)i'-'(6-l)c'-'(c-l) or a factor of this. Thus the number of 9's required can never exceed (n — 1). W. LETTERS RECEIVED AND SHORT ANSWERS. FitzGeeen. The word "aperture," in the reply to which you refer, had reference to a refractor, but2i inches was a misprint for 2i inches. This would have an approximate focal length of 30 inches, and would cost between £7 and £8. An instrument fur- nished with a 2i-inch object-glass would be of about 3 feet focus. Either of these would bear a power of 200 on close double stars ; the latter even a somewhat higher one. No reflector of less tliau 3i inches aperture is of the slightest use. — Castor. The cause to which you refer, viz., the production in the offspring in an aggra- vated form of diseases common to their consanguineous parents, is the generally-accepted reason given against marriage between cousins. On the other hand, as you say, two people standing in that relation, each healthy and of exceptional intellectual power, might fairly be expected to beget a high type of children. Still, every agriculturist knows the evil of " breeding in and in " ; and what is so well established in the case of the bfute creation may reasonably be held to apply to man in his animal relations. — A. CD. C. suggests, in connection with a statement on p. 23 as to the origin of a rite held as sacred by Christians, " that Mr. Clodd should show that a similar one was observed in any religious system previous to the introduction of Christianity." He also finds fault with Mr. C.'s assertion that " the eastward position is the undoubted relic of worship of the rising sun," with which 1 am considerably more surprised, inasmuch as I imagined that tl 15 was admitted as an indisputable fact by all save a very few bigoted and ignorant people indeed. — W. A. Leonard. Thanks, but 1 have already declined a series of articles on the same subject from a thoroughly competent member of our own staff. — -J. Mubb.ay. The apology is sufficient. • — Sigma. Your reasoning is utterly falla- cious. You deal with infinity as a quantity which can form a member of an equation ! Were this possible, you might multiphj it; but you can no more talk of five times in- finity than you can of nothing-. An "infinite circle" is July 25, 1884.] • KNO^VLEDGE ♦ 79 absolutely unthinkable. It can bare noitlier centre nor circum- ference.— W. Brooks Sayers. Would you be surprised to hear that a gentleman named Aristarchus of Samos (who died B.C. 212) anticipated yoa in your idea of determining the distance of the sun, by observing the angle subtended by him and the dichotomised moon, some 2,160 years ago? From the practical impossibility, however, of ascertaining when the moon is exactly half-full, he made out that the sun's distance from the earth was onh- nineteen times that of the moon ; whereas, as we know, this is less than a twentieth part of its true value. Your absurd endorsement of " private " on your letter has delayed it exactly a week. — G.\ETn WiLKixsoN opines that the vaccine eruption is contagious. — T. Mann. The principal movements of the earth are : — 1. The annual. 2. Her motion round the centre of gravity of herself and the moon. 3. The diurnal. 4. What yon speak of as the pre- cessional, or that conical motion of her axis which gives rise to the Precession of the Equinoxes. 5. The Xutational. 6. The eecular change in the obIi(]uity of the ecliptic. 7. The revolution of her apsides. 8. The secular variation is the eccentricity of her orbit, and, 9, her motion in space in common with the whole solar system. The contributor to whom you refer seems to have forgotten his promise. — A. JIackay. See reply to you on page Gl and para- graph on page 02. — Jas. Gille.spie. Do, for goodness sake, master the rudiments of your subject. Do you know that the earth's mean equatorial semi-diameter only subtends an angle of 885" at the Sun, and that the Pole Star iV< actually vertically overhead in latitude 88° 11' north ? Polaris is not in the pole of the heavens, but 1° 19' from it. You seem hopelessly incapable of comprehend- ing that at the enormous distance of the fixed stars all lines simultaneously drawn to them from any parts of the earth's surface are parallel — nay, that so remote are they that even the diameter of her orbit shrinks to a point as viewed from them ! — J. Greevz Fi,*her sends me " Five Eulez for Improving Spelling," for which I am much obliged ; but fancy that I shall continue to employ, for some little time to come, orthography so thoroughly " understanded of the people" as that which ho seeks to supersede. — PoLY'GLOT. Thanks. Certainly not at present. — Nigel Doble. Premising that ()6 inches is a ridiculously in- adequate focal length for a 6-inch object-glass (which would per- form infinitely better if it had a focus of 90 inches). I may tell you that you would need at least four eye-pieces for astronomical purposes, which, with a G6-inch objective, would be constructed as follows, each, of course, consisting of two plano-convex lenses, with the plane sides next the eye. So. 1 field-glass 1'65-inch focus, eye-glass 0'55-inch focus, I'l inch apart. This would give a power of 80. No. 2 field-glass, 0'73 inch focus, eye-glass 0'24 inch focus, 0'48 inch apart. This would magnify ISO diameters. No. 3 field- glass, 0'53 inch focus, eye-glass 018 inch focus, 036 inch apart. This would magnify 250 times. And No. 4 Field-lens, 026 inch focus, and eye-lens 0'09 inch focus, 0'17 inch apart. This would give a power of 500 for very close double stars. Each of these eye-pieces should have a diaphragm, to limit the field of view, placed in the focus of the eye-glass. I do not know the work you mention. — Malcolm Fyte. The pernsal of your letter suggests the dictum of the great American philosopher: "There's nothing new, and there's nothing true, and it don't much signify." In everything of the slightest value you have been anticipated by Mr. F. H. Wenham and others — years ago. — Augustus J. Harvey suggests the appointment of a staff of commissionaires to conduct visitors to the principal points of interest of the Health Exhibition, and to explain the most important objects shown there. — The President AND Council of the Society for the Study and Cure of Inebriety. I regret that I was a good many miles from London on the evening of the 21st. — H. W. Jackson. Please communicate with Messrs. Wyman & Sons, the publishers of Knowledge. — Law. Prior to the receipt of your letter I was ignorant that there were any Whitworth Law Scholarships at all. — W. E. Snell. No one, that I am aware of, has ever disputed in these columns the value of sanitation as one form of prevention of small-pox. — A. McDonnell. I will read your pamphlet as impartially as I can. — Eye-witness. Something of the sort was attempted on p. 247 of our last volume, but did not seem to meet any general want. My large star-atlas would enable you to learn the constellations. — G. Pixnington. " I think not," says the lamb. — G. C. I do not know the particular book you mention, but the names of its joint authors afford a sutBcient guarantee of its excellence. Bloxam's is my text-book. Churchills publish it, and it is first-class, but it cost rather more than your specified price. In response to numerous applications, it has been decided to issue "The Index " to Volume V. of Knowledge, ivith the present numier,/ree of charge. (Bur iHattjfmati'ral Column. n NOTES ON EUCLID'S SECOND BOOK. By Richard A. Proctor. {Continued from p. 41.) IT is well to notice the algebraical and arithmetical relations which the different relations presented in the preceding proposi- tions serve to illustrate. We must show first that if each of the two lines which contain a rectangle can be divided into an exact number of parts each equal to some unit of linear measurement, then the product of the two numbers represents the number of corresponding units of square measurement contained in the rectangle. Let the rectangle A B C D be contained by the lines A B, AD; and suppose that a certain unit of length '^ " is contained 13 times in A B and 7 times in AD. Then if A B be diWded into 13 equal parts and A D into 7 equal parts, each part of each line is equal to this um't of length. And if we draw through the points of division in A B lines parallel to AD, and through the points of division in AD lines parallel to A B, it is clear that the rectangle A B C D will be divided into a number of squares each having its sides equal to the unit of len<'th. Now each row of squares parallel to A B contains 13 such squares, and there are seven such rows. Therefore the -whole rectangle contains 7 times 13 squares. Thus the product of the numbers 7 and 13, which represent the length of the sides in terms of the linear unit, gives us the number representing the area of the rect- angle in terms of the corresponding unit of square measurement. And the proof would have been precisely the same whatever the number of units of linear measurement in the sides A B, AD, — so that, if A B contains a such units, and A D contains b, the rectangle A B C D contains a b units of square measurement. It would be easj' to extend this proof to the case of a rectangle having incommensurable sides ; but for the purpose of illustration the case of commensurable sides is sutficient. This commenstira- bility is to be understood as implied in what follows. In Euc, Book II., Prop 1, if the undivided line contain a units of length, the several parts of the divided line b, c, and d units, respectively, the proposition corresponds to the algebraical identity a(b + c + d) =ab + ac + ad. Prop. 2. — If the undivided line contain (a + b) units of length, its parts a and h units correspond to the identity (a + b)a+ (a + h)b={a + by-' In Prop. 3, on the same supposition, the algebraical identity corresponding to the proposition is {a + b)b = ab + b'. Prop. 4, on the same supposition, corresponds to the identity {a + b)-' = a^ + 2ab + b' In Prop. 5, let AB = 2a, and CD = 6, so that AD = (a-l-6) and D B = (a — fc) then the corresponding algebraical identity is (a + b) (a-b) +b' = a' that is, the well known relation a-—b-= (a + b) (a — b). But if we put A D = a and D B = b, we obtain the relation — (a — b\- /a + b \- — )=(-!-) = that is, the well known formula — {a + by- (a-by=iab We get the same identities in the case of Prop. 6, if we make corresponding suppositions, simply interchanging a and b. In Prop. 7, put AC = a, and BC = b, then the algebraical identitv corresponding to the proposition is (a¥by'-\-b'' = a- + 2b{a + b) In Prop. 8 put AC = a, and BC = 5; then the corresponding algebraical relation is 4(o-t-b)b-Ha= = (a-H2b)2. In Prop. 9 put first A B = 2 a and C D = b ; then the corresponding algebraical identity is (a-f b)'-f (a-5)- = 2(a--Hb'). Nest put A D = a and D B = b, and we obtain the relation „= + b= = 2(«-±-7.2(«-rL^y 80 ♦ KNOWLEDGE • [JcLY 25, 1884. which is not a new relation, the change in our suppositions merely leading to the inversion of tlio former relation. In Prop. 10 corresponding suppositions with the interchange of a and b iiive the same results. It will bo found that any theorem respecting rectangles may be shown to correspond to an algebraical identity, — and in like manner that any homogeneous algebraical identity of two dimensions may be made to supply one or more geometrical theorems respecting rectangles. Let us take as an instance the following identity : — (a+b + cy- = a? + h- + c- + 2al + 2hci-2ca ; this resolves itself into the following proposition : — Prop. I. Tf a straiijht line AB ie dirided into any three parts in t'le points C and D; then the square on A B shall A___ , ^ he equal to the aqiiares on AC, CD, and D B, together with twice the rectangles contained bij A C, C 1), by AC, D B, and by CD, J) B. By Euc. II., prop. 4, the square on A B is equal to the squares on A C, C B together with twice the rectangle A C, C B ; that is (again applying Prop. 4) to tlie squares on A C, CD, D B, together with twice the rectangle CD, D B, and (Prop. 1) twice the rectangles AC, CD, and AC, DB. Prop. 11 is an important one. It may be enunciated also thus, — To divide a given straight line into tico parts so that the squares on the whole line and on one of the parts mai; be together equal to three times the square on the other part. That this enunciation is equiva- lent to the other follows immediately from Prop. 7. Prop. 11 offers a problem somewhat more difficult than most of those in Euclid. It is made use of by him in Book IV. Prop. 10 ; but when it is required for the solving of Prop. 30, Book VI., he appears to have forgotten that he had already solved it, and adopting a less happy mode of analysing it occupies three long propositions with its solution. We shall note an analogous proposition in our next contribution on this subject. {To be continued.) (Bm cores Column. By Mephisto. THE FRESCU DEFENCE. 1. P to K4 P toK3 THIS is a perfectly sound and safe defence, and suitable when- ever the second' player wishes to play a close game or avoid the more attacking lines of play arising from 1. P to K4 ; White's best reply is 2. ?J5_Qi. If now P x P, then P x P followed by ^ ■' P to Q4 Kt to KB3, B to Q3, and Castles with a safe game. Wiiite may also play 3. Kt to QB3 - — B to Kto would not lead to any favour- Kt to KB3 able result. White now would not gain anything by advanci-sg P to K5, as, after Kt to Q2, Black would vigorously attack the centre by P to QB4, Kt to B3, &c. If 3. P x P, P x P, and we have a normal position which Black follows up by B to K2 and Castles. White has now two lines of play, viz. : — B to Q3 and B to KKto. If Black. i - » 1 1. ^. 1 1 L % g 'J> o •?i o; •©'#.i 4. B to Q3 PxP 5. Kt xP B toQ2 G. Kt to K2 B to B3 7. P to B3 B toK2 8. Castles Castles and in this variation White has a good position. It might perhaps have been better to play 5. P to yKt3, followed by B to Kt2, as that would leave the square on B3 open for the Knight. If in- stead 4. B to KKt5 B to K2 5. B X Kt B X B 6. Kt to B3 Castles Whiiji. 7. B to Q3 PxP 8. B X P Kt to B3 With two Bishops on the board. Black need not be afraid to have his Pawn doubled, the position being an even one. SELECTED PROBLEMS. Black. Whitb. White to play and mate in three moves. Black. Whiib. White to play and mate in two moves. ANSWERS TO CORRESPONDENTS. ,*, Please address Chess Editor. Fraukford.— If 1. Q to K3, P to KtG, 2. Kt to K6(ch), K to Kto, 3. Q to Q5, K to R6. Geo. W. Thompson. — Solution not quite correct. 1. Kt to B3, 2. Kt to Kt3(ch;, q X Kt, 3. Kt to Q7(cli), Kt « Kt. George Gouge. — 1. Kt to Bsq, 2. Kc x P, and mates next move. Correct solutions received from il. T. Horton and A. Rutherford. The Owl. — Part solution correct. Contents of No. 142. PaGS Other Worlds than Ours. By M. de Foutenelle. With Notes by Richard A. Proctor (Conlimied)... 43 Chemistry of Cookery. XXXVIII. By W.M. Williams « Man and Xature 45 Optical Recreations, (lllut.) By F.R.A.S 46 Electro-plating. Till. By W. Slii}SO 47 The Entomology of a Pond. By E. A. Butler 49 Superstition 60 International Health Exhibition. VIII. (ntut.) 60 FA61 British Seaside Resorts. I. By Percv Russell 63 Zodiacal Maps. (lUut.) By R. A. Proctor 64 The Antarctic Regions By R. A. Proctor 64 The Absolute Capacity of a Con- denser 56 ne\-iews 56 The Face of the Sky. By F.R.A.S. 58 Design for Parlotir Organ. {Iltu*.) 58 Miscellanea 58 Correspondence 60 Our Mathematical Column 62 Our Chess Column 64 SPECIAL NOTICE. Part XSXIII. (.Tnlj, 188-11, now ready, price Is., post-free, 1b. 3d. Tolume Y., compnsine the numbers published from January to June, 1SS4, will soon be ready, price Os., including parcels postage, 9s. 6d. Binding Cases for all the Tolumea published are to be had, price 28. each; including parcel postage, 23. 3d. Subscribers' numtera bound (including tille, index, ard case) for 39. each Volume ; including return journey per parcels post, 3s. 6d. Eemittances should in every case accompany parcels for binding. OFFICE : 74-76, GREAT QUEEN STREET, LONDON, W.C. Aug. 1, 1884.] ♦ KNOWLEDGE ♦ 81 AN ILLUSTRATED MAGAZINE OF SCIENCE KWorded-ExactlyDe^©^ LONDON.- FRIDAY, AUG. 1, 1884. OONTBNTS OF No. 144. Chemistrv of Cookery, XXXIX. Br W."M. Williams 81 TheTransmission of Power 83 The EntomologTof a Pond. {Illut.) By E. A. Butler 83 Railway Brakes. By '* Trevitheck " InterDational Health Exhibition. X Other Worlds than Ours. By M. de Fontenelle. With Notes by Richard A. Proctor The Tricycle of Today. (Illut.) ... Embalmers 8-1 87 92 Electro-platine. IX. By W. Slingo Kii Tenns in a Three-inch Telescope, (/«»».) By F.R.A.S British Seaside Resorta, II. By Percy Russell 93 A Catastrophe averted by Electric Wires 96 Reviews 97 The Face of the Sky. By F.H.A,S. 9S Miscellanea 9!j Correspondence 100 Our Mathematical Column 101 Our Chess Colunin 103 THE CHEMISTRY OF COOKERY. By W. Mattieu Williams. XXXIX. COUNT KUMFORD'S DIETETICS. IN the formula for Eumford's soup given in my last, it is stated that the bread should not be cooked, but added just before serving the soup. Like everything else in his practical programmes, this was prescribed with a philosophical reason. His reasoning may have been fanci- ful sometimes, but he never acted stupidly, as the vulgar majority of mankind usually do when they blindly follow au established custom without knowing any reason for so doing, or even attempting to discover a reason. In his essay on " The Pleasure of Eating, and of the Means that may be Employed for Increasing it," he says : — " The pleasiu'e enjoyed in eating depends, first, on the agreeableness of the taste of the food ; and, secondly, upon its power to affect the palate. Now, there are many sub- stances extremely cheap, by which very agreeable tastes may be given to food, particularly when the basis or nutri- tive substance of the food is tasteless ; and the effect of any kind of palatable solid food (of meat, for instance), upon the organs of taste, may be increased, almost indefinitely, by reducing the size of the particles of such food, and causing it to act upon the palate by a larger surface. And if means be used to prevent its being swallowed too soon, which may easCy be done by mixing it with some hard and tasteless substance, such as crumbs of bread rendered hard by toasting, or anything else of that kind, by which a long mastication is rendered necessary, the enjoyment of eating may be greatly increased and prolonged." He adds that "the idea of occupying a person a great while, and afford- ing him much pleasure at the same time in eating a small quantity of food, may, perhaps, appear ridiculous to some ; but those who consider the matter attentively will perceive that it is very important. It is perhaps as much so as any- thing that can employ the attention of the philosopher." Further on he adds : — " If a glutton can be made to gormandise two hours upon two ounces of meat, it is certainly much better for him than to give himself an indigestion by eating two pounds in the same time." This is amusing as well as instructive, so also are his researches into what I may venture to describe as the specijic sapidity of diflerent kinds of food, which he deter- mined by diluting or intermixing them with insipid mate- rials, and thereby ascertaining the amount of surface over which they might be spread before their particular flavour disappeared. He concluded that a red-hen ing has the highest specific sapidity, i.e , the greatest amount of agree- alile flavour in a given weight of any kind of food he had tested, and that, comparing it on the basis of cost for cost, its superiority is still greater. He tells us that " the pleasure of eating depends very much indeed upon the manner in which the food is applied to the organs of taste," and that he considers " it necessary to mention, and even to illustrate in the clearest manner, every circumstance which appears to have influence in pro- ducing these important effects." As an example of this, I may quote his instructions for eating hasty pudding : — "The pudding is then eaten with a spoon, each spoonful of it being dipt into the sauce before it is carried to the mouth, care being had in taking it up, to begin on the out- side, or near the brim of the plate, and to approach the centre by regular advances, in order not to demolish too soon the excavation which forms the reservoir for the sauce." His solid Indian corn pudding is, in like manner, " to be eaten with a knife and fork, beginning at the cir- cumference of the slice, and approaching regularly towards the centre, each piece of pudding being taken up with the fork, and dipped into the butter, or dipped into it in part only, before it is carried to the mouth." As a supplement to the cheap soup receipts given in my last, I will quote one which Rumford gives as the cheapest food which in his opinion can be provided in England : — Take of water eight gallons, mix it with 5 lb. of barley- meal, boil it to the consistency of a thick jelly. Season with salt, vinegar, pepper, sweet herbs, and four red herrings pounded in a mortar. Instead of bread, add 5 lb. of Indian com made into a samp, and stir it together with a ladle. Serve immediately in portions of 20 ounces. Samp is " said to have been invented by the savages of North America, who have no corn-mills." It is Indian corn deprived of its external coat by soaking it ten or twelve hours in a lixoviumof water and wood ashes.* This coat or husk, being separated from the kernel, rises to the surface of the water, wliile the grain remains at the bottom. This separated kernel is stewed for about two days in a kettle of water placed near the fira " When sufiiciently cooked, the kernels will be found to be swelled to a great size and burst open, and this food, which is uncommonly sweet and nourishing, may be used in a great variety of ways ; but the best way of using it is to mix it with milk, and with soups and broths as a substitute for bread." He prefers it to bread because "it requires more mastication, and conse- quently tends more to prolong the pleasure of eating." The cost of this soup he estimates as follows : — d. 5 lb. barley-meal, at lid. per lb., or 5s. 6d. per bushel... 7i 5 lb. Indian corn, at lid. per lb 6J 4 red herrings 3 Vinegar 1 Salt 1 Pepper and sweet herbs 2 m This makes 64 portions, which thus cost rather less than one-third of a penny each. As prices were higher then than * Such UiOvinm ia essentially a dilate solution of carbonate of potash in very crude form, not conveniently obtained by burners of pit coal. I wiU try the commercial carbonate, and report results in my next, stating quantities and other particulars. I have but just come upon tl^i" particular soup receipt for the first time. 82 ♦ KNOWLEDGE ♦ [Aug. 1, 1884. now, it comes down to little more than one farthing, or one-third of a penny, as stated, -when cost of preparation in making on a large scale is included. I have not yet tried this soup. In reference to the others specified in my last, I should add that I found it advantageous to use a double vessel — a water-buth constructed on the glue-pot principle. Such vessels are .sold under the name of " milk-scalders." The reason of this is, that with our ordinary fireplaces the heat is so great that the liability to char the bottom of the thick porridge is a source of trouble. Rumford's fire- places were so skilfully constructed, and used with just as much wood fuel as was required to do the work demanded, and thus this difficulty scarcely existed. I have little doubt that one of the reasons why the thin broth of our workhouses and pri.sons takes the place of his thick soup is, that the liquid stuff demands no skUl nor attention from the officials who superintend and the cooks who prepare it. Their convenience is, of course, sacred. The feeding of the Bavarian soldiers is stated in detail in Vol. I. of " Rumford's Essays." Space will permit me only to take one example, and that I must condense. It is from an official report on experiments made " in obe- dience to the orders of Lieut.-General Count Rumford, by Sergeant Wickelhof s mess, in the first company of the first (or Elector's own) regiment of Grenadiers at Munich." JuxE 10, 1795. — Bill of Fare. Boiled beef, with sonp and bread dumplings. Details of the Expense. First for the boiled beef and the soup. lb. loths. Creutzers. 2 0 beef 16 0 1 sweet herbs 1 0 Oi pepper OJ 0 6 salt Ot 1 14i ammunition bread cnt fine 2J 9 20' water 0 Total... 13 10 Cost ... 20i The Bavarian pound is a little less than l^lb. avoirdu- pois, and is divided into 32 loths. All these were put into an earthenware pot and boiled for two hours and a quarter ; then divided into twelve portions of 26y't7 loths each, costing 1| creutzer. Second for the bread dumpling. lb. loths. Creutzers. 1 13 of fine Semel bread 10 1 0 of fine flour 4i 0 6 salt Oi 3 0 water 0 Total... 5 19 Cost... 15 This mass was made into dumplings, which were boiled half an hour in clear water. Upon taking them out of the water they were found to weigh 5 lb. 24 loths, giving 15^ loths to each portion, costing 1| creutzer. ""The meat, soup, and dumplings were served all at once, in the same dish, and were all eaten together at dinner. Each member of the mess was also supplied with 10 loths of rye bread, which cost ySj of a creutzer. Also with 10 loths of the same for breakfast, another piece of same weight in the afternoon, and another for his supper. A detailed analysis of this is given, the sum total of which shows that each man received in avoirdupois weight daily : lb. oz. 2 2^ of solids 1 2-;^ of " prepared water " 3 Sy'^j total solids and fluids. •which cost 511 creutzers, or twopence sterling, very nearly. Other bills of fares of other messes, officially reported, give about the same. This is exclusive of the cost of fuel, &.C., for cooking. All who are concerned in soup-kitchens or other economic dietaries should carefully study the details supplied in these essays of Count Rumford ; they are thoroughly prac- tical, and, although nearly a centuiy old, are highly instructive at the present day. With their aid large basins of good, nutritious soup might be supplied at one penny per basin, leaving a profit for establishment expenses ; and if .such were obtainable at Billingsgate, Smithfield, Leaden- hall, Covent-garden, and other markets in London and the provinces, where poor men are working at early hours and cold mornings, the dram-drinking which prevails so fatally in such places would be more effectually superseded than by any temperance missions which are limited to mere talking. Such soup is incomparably better than tea or cofiee. It should be included in the bill of fare of all the coffee-palaces and such like establishments. THE TRANSMISSIOX OF POWER. By a. Berixger. IF we admit that the local conditions are equally favourable to the four systems (viz , electricity, water under pressure, compressed air and telo-dynamic cables), that is to say, if we set on one side particular considerations which may render one or the other system more suitable in a given case, the comparison of prices shows that electricity and telo-dynamic cables are the most favourable agents for the transmission of power. Between these two we must choose the cable as effecting the cheap transmission up to a distance of 1 kilometre, but for greater distances electricity is preferable. We note, in passing, the interesting result that a hydraulic motive power transmitted by electricity to a distance of 20 kilometres costs less than the same power produced on the spot by a large improved steam-engine, even if we calculate the water-power at 0 03 fr. per horse-power daily. It follows that a powerful waterfall will supply, within a radius of four leagues, power cheaper than that produced by steam-engines of 100 to 200 horse- power, and within a far wider radius it will compete advantageously with small steam-engines or with gas. Although cables are very suitable for distributing power in the country to a few separate places, they are quite out of the question when it is required to effect unlimited sub- divisions, e.g., in a distribution of power from house to house in a town. In this case the three other systems remain alone in the field. For instance, if less than 1 kilometre electricity has only the advantage of a few centimes over air and water, but its advantage increases for longer distances. Thus the hourly cost per horse-power for i kilometre is 0'2-t franc, for 1 kilometre 0-2.5 franc, and for 12 kilometres 0'37 franc, whilst water and air reach this price for H to 2 kilometres. Transmissions by water and air are therefore far sur- passed by electric transmission, and if we wish to produce power by steam in a central establishment and distribute it from house to house within a radius of 10 kilometres electricity alone could furnish an economical solution of the problem. We must here remark that such a distribution of power can only be, for the present, useful in the small trades, for if more than 10 horse-power is required, a special motor is more advantageous. If we divide the region to be supplied with power into Au-steering wheel is supplied with Bowu's ball-bearings, while roller ones are fitted to the two driving-wheels. The latter, I believe, are the oldest bearings which exist, and are unmistakably the best bearings made, being well-uigh indestructible, if only kept well oiled and free from grit. The steering-wheel in front renders a spill scarcely possible when ordinary caution is used. It is well known that if a rider presses too hard on the pedals the front wheel will leave the ground. The back- stay of the " Salvo " prevents it from being lifted so far off the ground as to permit of the machine turning over backwards. The lever band-brake fitted to the machine is as perfect as a brake can be, being far preferable to a tyre-brake, which is not only liable to pitch an inexperienced rider out if applied too suddenly, but may snap at any time when least expected, and with constant usage cannot fail in time to wear the tyre away or cause it to work loose. No matter if the hill bs as steep as a roof, there need be no fear of descending on the " Salvo," since the brake is sufficiently powerful to check the machine on any incline whatever, and at any speed. Neither need there be any fear of ajjplying the brake promptly and vigorously — as, for instance, one is often compelled to do in the case of un- expectedly coming on children playing in the roid, who Aug. 1, 1884.] ♦ KNOWLEDGE 89 invariably run in front of the machine, instead of out of its way. One of the most pleasurable features of tricycling to my mind is descending hills at considei-able speed, and on this machine the rider may do so at all times safely without being robbed of his pleasure by a constant dread of the brake snapping or not acting in some way in case of emergency. The machine is also supplied with comfortable, rubber- clothed foot-rests, which, besides being a great luxury in riding down-hill, enable the rider on a good level road to take an additional rest by pedalling with alternate feet. But the best feature of the machine is its patent auto- matic balance-gearing, an illustration of which is here given (through the kindness of Messrs. Starley Bros., of Coventry). A. — Bevel tootli-wheel, fixed to the hub of one driving-wheel. B. — Crown-wheel. C. — Bevel-wheel fixed to shaft. D. — Main axle. E. — Chain-wheel. The axle connecting the two large driving-wheels is tele- scopic, the central shaft from the right wheel working in a hollow tube from the left. The chain-wheel works between two bevelled cog-wheels, one of which is attached to the hub of the right-hand driving-wheel, while the other is attached to the end of the hollow shaft that proceeds from the left hand. Between the two cog-wheels works loosely the collar that forms the centre of the toothed chain-wheel, while on a rod which passes from the centre to the circumference of the chain-wheel works a small, loose cog-wheel, whose teeth are so bevelled as to work against the teeth of the other two cog-wheels. While the machine is being driven in a straight course, the teeth of the little cog-wheel press evenly against the teeth of the other two cogs, and equal power is by this .means imparted to both driving-wheels. But should one wheel be rotated more slowly than the other, as in turning corners or steering the machine completely round, the little cog or pinion-wheel glides freely over the face of the Vievelled cogs that move the inner or slowly - rotating ■wheel, while it presses with more force against the cogs of the outer wheel, thus causing it to rotate with greater speed. The great advantage of this simple mechanism is at once apparent in the facility it gives of turning sharp curves without the risk of the machine tilting over. It also can be worked backwards or forwards with equal eflfect. While at all times the machine, by the use of this gearing, is kept thoroughly under control. With reference to its luggage-carrying capability, there are few machines to surpass it, the amount of articles one can fasten to the detachable luggage-carrier behind being something prodigiou?. It is in consequence a capital machine for an amateur photographer who wishes to take sufficient paraphernalia to photo any lovely bit of scenery he may meet with on his tour. I advise those persons, however, who are above the average weight, or who live in a district where roads are bad, to ride an ordinary " Salvo," on account of its greater strength ; whereas, on the other hand, for ladies, or those whose weight does not exceed 10 St., and who are fortunate enough to live in a neighbourhood of good level roads, with smooth surface, I strongly recommend their " Special Light Salvo." With regard to height of wheels, I should recommend a 46-in., geared level, for those whose height does not exceed 5 ft. 9 in., and a 48-in., geared level, for those above this height. Undoubtedly the " Royal Salvo " No. II. is one of the very best machines made. F. EMBALMERS. 11H0UGH in America embalming be on the increase and even bids fair to be one day popular, there can be no doubt that with us the practice does not gain ground. We are a sensible rather than a sensitive people, and, unable to grasp any very definite reason for encouraging the art, we scarcely notice it. We have, in fact, no desire to have our dead, like our poor, always with us. But, never- theless, there are in each year a certain number of cases of tolerably regular occurrence, and, to meet that demand, a small supply of practitioners, authorities on the subject, employed by the undertaker, who, as a rule, is the person first consulted. Compared with the ancient, the modern method is rapid and simple ; with the Egyptians, the process was a question of months, with us it is one almost of minutes. Here it is, as practised by Dr. B. W, Richardson, the eminent authority on health, who has probably had a wider and longer experience than any other man in the country. " A large artery is exposed and opened, and into the vessel a hollow needle is inserted. The needle is firmly tied in its place. Through the needle a solution of chloride of zinc is injected slowly until it has found its way over every part. The principal art that is required in this process is to be very careful not to use too much force in driving the fluid into the tissues, and in not using too much fluid. The fluid which answers best is made as follows : — To two pints of water, at 50° Fahr., add chloride of zinc slowly, until the water just refuses to take up any more of the salt. Then add one pint of water more, and two pints of methylated spirit. The five pints so produced are a suflioient quantity for embalming an adult body. The solution can be injected quite cold, and it will find its way readily over the vessels. If expense be not considered, pure alcohol may be used instead of the methylated spirit. The efiect of the solution is shown by its making the svr- faoe of the skin white, firm, and, for a short time, slightly mottled." We have this eminent authority's permission to add that the latest improvement (a discovery of his own, 90 KNOWLEDGE • [Aug. 1, 1884. and not yet publibhed to the world) is that of injecting through the optic foramen, by the introduction of a long subcutaneous needle into the cavity of the cranium from behind the eyeball. This method, -which will no doubt supersede all others, was discovered rather by accident than direct experiment, and dates from researches conducted by Dr. Richardson on the best modes of restoring animation after sudden dissolution from chloroform and other lethal substances. Thus, in original work it often happens that, in carrying out a design which has been most carefully projected, the origin<es above or below the Sun as seen by us. On the 12th of July she was nearly 5^ south of the Sun's centre. Under these circumstances, as we shall presently see, while nearly the whole of her lighted face must be turned towards the Sun, yet an extremely- narrow portion of her illuminated limb is perceptible. A& she travels to the westward of the Sun after this as a morning star, more and more of the lighted part of her disc Viecomes %'isible ; until she assumes the appearance of the Moon when in her first quarter ; or, technically speaking, ia " dichotomized." As will be seen by any one who will draw a diagram or plan of Venus's orbit, her diameter must appear the largest at the time of her inferior conjunction, and must diminish just as her illuminated surface increases. After attaining her greatest elongation west of the Sun (which can never exceed 47" 15'), the planet appears to begin to move back again, or from west to east, grows- smaller and smaller, and when her disc is becoming fully illuminated, disappears behind the Sun in the glare of his light, as merely a rather big star. She is then said to be in superior conjunction. Emerging, after an interval, from his rays to the east of him, she becomes an evening star, and goes through all her phases in the reverse order, increasing in diameter as the area of her illuminated surface dimi- nishes. Attaining her greatest eastern elongation, and then turning back as a rapidly- narrowing crescent, she finally returns to inferior conjunction again. This all being, understood, we will, at last, go to the telescope. Fig. 1.— Tenns, May 10, 18S-1. Power ICO. At 0 p.m., on May 2, Venus had attained her greatest- elongation (45° 27') east, and eight days later the drawing above was made, with a power of ICO, in a 3-in. telescope. Now, two or three things will strike the observer who will carefully scrutinise this sketch. Perhaps the first wUl be the great brilliance of the illuminated limb o£ Aug. 1, 1884.] ♦ KNOWLEDGE ♦ 93 the planet, and the way in which this contrasts with the inner portion, or "terminator" (Knowledge, vol. iii., p. 222), shading off into the bright sky. The two little cusps, too, 80 sharp and bright, will certainly catch the eye, from the want of correspondence of their inner edges with the interior curve of the planet's lighted surface. All this seems indicative of a dense and extensive atmo- sphere surrounding Venus. One effect of the inner shading is worthy of note, and that is the effect it has in reducing the area of the planet which should be theo- retically illuminated. It we draw a plan of the orbit of Venus we shall see that at her greatest elongation she ought geometrically to be dichotomised, i.e., exactly half-full ; but it will be seen that in reality she is rather less than this, the degradation of light towards the terminator being pretty rapid. Observers of repute have seen the terminator jagged and uneven, like that of the moon ; but it is too much to expect of a .3inch telescope that it should exhibit such difficult features as this. A blunting of one or both of the horns has also been perceived at times by various astronomers, both in this country and on the Continent. And, what is of considerable interest to the possessors of instruments of the size employed for the purpose of these papers, very faint dusky spots and bright patches have been perceived from time to time in telescopes of the most varying apertures ; small ones show- ing these spots as well as, in fact better than, some of the larger instruments. This may possibly arise from the creneral glare of light in a large objective or mirror deaden- ing the eye to such delicate details. It is by the aid of these spots, real or imaginary, that the hypothetical period of rotation of Venus has been determined. But, however beautiful and curious the spectacle may be which is presented by Venus in quadrature, it will scarcely interest the student so much as his first view of her in inferior conjunction. Our succeeding figure exhibits the Yic. 2. — Venus in Inferior Conjunction, July 11th, 1884. Power 160. planet as seen in the same instrument and with the same power as that employed to make our first sketch with. The contrast between these two aspects of Venus will arrest the attention at once. The comparatively small half-moon has become converted into a hair-like glittering semicircle of light, enclosing something which is certainly darker than the surrounding sky. The very abnormally hazy condition of the atmosphere which has now persisted for many months was against the percep- tion of any very delicate gradations of shade, so that the whole of the dark body of Venus was invisible ; but the effect, difficult or impossible to reproduce in a wood-cut, was that of a disc dark where embraced by the crescent of light, and fading into the light of the sky out- side or beyond the cusps. On the occasion of former inferior cocj unctions, the whole of the planet's dark limb has been unmistakably perceived. In order that it may be seen to the greatest advantage, a veri/ small diaphragm should take the place of the ordinary one between the two lenses of the Huyghenian eye-piece. A blackened card disc with a fine hole made centrally in it with a red-hot needle, answers capitally. The hot needle bums the fringed edge of the perforation and leaves it clean and sharp. The smaller the bole, consistently with distinct vision, and the more sky light that is cut ofl', the sharper and better will the body of the planet appear. This little device will always be found useful when any body is to be viewed in bright sunlight. There is a queer story — or, perhaps, it would be more correct to say a series of queer stories — with reference to various observations of a satellite or companion to Venus, situated always close to the planet, sometimes on one side of her, sometimes on the other, but always exhibiting a phase identical with her's. The most feasible explanation of this is that it has had its origin in each case in what is called, "a gho.st" in the eye-piece, i.e., in a reflection of the )ilanet's image from the convex surface of the eye-lens on to the plane surface of the field-lens, and so back to the eye of the observer. An observation made by Short, the famous optician, in 1740, who did use two different telescopes, seems the only one to throw any legitimate doubt upon this explanation. SI. Houzeau, the eminent Belgian astronomer, however, is so convinced of the objective reality of the various apparitions of this satellite that in Ciel et Terre for May l-ith of the present year he gravely propounds the hypothesis that a little planet (which he provisionally names Neith) revolves round the sun in an orbit just ex- terior to that of Venus herself. Here there is an oppor- tunity for the student to distinguish himself. He has only to watch Venus day and night until he picks up this attendant, to do so. Whether, though, he succeeds, or whether he fails in this attempt, he will find himself amply repaid for any amount of labour by the diversified but always beautiful appearance of the planet as she speeds on her path round the sun, and may find infinitely less profitable ways of spending his time than by the devotion of a daily half-hour to watching Venus in a Three-Inch Telescope. BKITISH SEASIDE RESOETS, FROM AN UNCONYENTIOXAL POINT OF VIEW". By Percy Russell. II- TAKING all England, and making proportional allow- ance for inland as against sea-coast populations, it would probably be found that the line of shore between Cromer on the north-east and the Bill of Portland on the south-west, is the best-known, perhaps, of all the coast of England to the greatest number of people. If, per contra, we take the much more sinuous shore-line from Portland Bill by Start Point, Falmouth, the Lizard Head, the Land's End, and then northwards to the splendid estuary of the Severn, and thence to St David's Head, that western head- land of Pembrokeshire, we shall follow a coast-line that, except at a few points, is unknown in detail as it is un- visited by the multitude, but which includes some of the finest scenery of these islands, being in many cases a happy blending of the rugged grandeur of north-west Britain with the softness and almost the climate of Italy itself. The 94 KNOWLEDGE ♦ [Aug. 1, 1884. Devonian heights extend southward to the Cornish high- lands, that magnificent series of granite table-lands and hills terminating in the Land's End and in the volcanic rocks of Lizard Point. These liighlands average from 800 to 1,300 ft. above the sea level, and from the ridge flow many short ri\ers through valleys rich with cornfields, orchards, and meadows. The combination of sublime with picturesque scenery is perfect, and on both sides of this peninsula the shore-line is bold, often grand, and constantly indented by beautiful bays guarded by imposing headlands. Some parts of Cornwall, like Falmouth — the creation, in a shipping sense, of Sir Walter Raleigh — are popularly known to most persons. Here, indeed, may be seen what is in truth a strange sight under English skies — in the form of lemon and orange-trees which yield plenty of fruit growing against garden walls. As a whole, however, this strange peninsula is rather out of the ordinary range of the normal seeker for a seaside resort, and I will, therefore, rapidly and lightly touch on a few of its salient features. St. Keverne, near the Lizard, with its quaint houses of unhewn .stone, the joints being stopped by that remarkable china clay which is in such demand as a principal ingre- dient in manufacturing Staffordshire potteries, is one of many examples of the extremely picturesque places to be found in this remarkable region. Here grows the graceful white heath {erica vagans), marking out with its pure blossoms the conformation of the serpentine which, com- posed of silica and magnesia, characterises the remarkable metamorphic rocks of the Lizard. In some places the dark- green masses of crystallised serpentine give a strange aspect to the scene. In contrast to these rocky masses are the marl lands, the true gardens of Cornwall, yielding enormous crops of from eighty to ninety bushels of wheat to the acre, if we may credit local agriculturists. Along the shores the successive cliffs are marked by variety and grandeur. At Nare Point is a cavern 100 ft. long, having, by a singular juggle of some natural convulsion, an ancient beach con- verted into its roof. Here one looks down on a famous flat known as the Chynals Wollows, of some sixty acres, and lying so low that in heavy gales the sea rolls in and deposits a tribute of fine sand, in constant request for brass castings in the great foundries at Hayle. The tamarisk hedges strike the stranger as something new. The twigs are reported to be possessed of tonic properties, and w-ere once in high repute in the days of domestic herbal medicine. Cliffs, caves, strange fissures, and extraordinary monoliths are among the common things of this romantic shore, and here, in the eighteenth century, there was, for a considerable period, a squadron of six smuggling vessels, manned by 23.5 fir.st-i-ate seamen, carry- ing 56 cannon, and maintaining for some years the com- mand of these wild seas, notwithstanding all the King's cruisers could do. This is but a patch of local colouring — a stray note in respect to the great and varied interest of these rugged shores. Penzance presents perhaps the most striking sight in the district. A mountain rises with ineffable grandeur from the midst of a lovely bay, beau- tiful in summer as Baia; itself, which Horace, by-the-by, preferred, he said, to all other watering-places in the Romau world, and, shooting up with stern abruptness, cul- minates in one of the most noteworthy pinnacles of the county. The precipitous sides are in strong contrast to the fertile lands around, and from St. Michael's Mount is a magnificent prospect of the Channel. At Penzance you can command both the English and the entrance to the Bristol Channel. Here gigantic rocks are piled about mute witnesses of some tremendous forces at work when, this portion of the British Islands was roughly fashioned into its present form ; here are the famous " Logging " or Loganstones — one of over a hundred tons being so deli- cately poised that it moves at a touch, and afar in the distance appears the Scilly archipelago. The island giving its name to the group is almost Inaccessible, and only five or six of the islands are regularly inhabited. These were the Cassiterides, or, perhaps, the Hesperides of the ancients, and they abound in strange monolithic monuments. Tresco, which lies between Bryhher and St. Martin's, wa.s granted by Athelstan to some monks in 930. St. Mary's, the largest member of the group, is quite a little kingdom in miniature. Hugh Town, the capital, is remarkable for the mingling of very old-fashioned with neat modern houses, and has an excellent pier, a post-oflSce, and custom-house. In Tresco may be seen the vestiges of a tenth-century abbey, and of a camp traditionally assigned to Oliver Cromwell Druidic remains — some real, and many, I suspect, fanciful — abound, and the geologist is certain here of a rich field for operation. On leaving the mainland to visit this singular cluster of rocky uplands — the highest points, no doubt, of an enormous submerged country — a splendid view is to be had of the Cornish coast formation here. In some instances, the promontories have a close resemblance to feudal castles. The thirty miles or so of sea between the Land's End and the Scilly Isles was once the famous Cornish champaign, and known as Lethowson, or Lyonesse, and is said traditionally to have included about a hundred and fifty churches. The landmarks of this submerged region are the Wolf Rock and the Seven Sisters — a cluster of cliffs whence fishermen of yore are said to have hooked up unmistakable evidences of a lost civilisa- tion. Some persons may think this exaggeration, but in 1817, in a January storm, it was for some hours extremely doubtful whether the sea would not break right through the country to St. Ives, and thus reproduce in the Land's End another Scilly group. As to the SciUy isles, some of the books I have consulted make them to number at most some forty or fifty, but other more trustworthy authorities reckon up full three hundred isles, islets, and rocks, scattered over an area of thirty square miles. Penimis, the head of the isles, is noticeable for its piled up granite blocks, forming walls, rude arches, and vast chambers, all the work of natural forces. There are caverns, covered galleries, and vaults hung with beautiful ferns, and enclosing crystal pools, while from the topmost blocks, the wild and lovely scene would be quite a revelation of land and seascape to thou- sands of persons who have seen nothing more striking than the Dover cliffs or Beachy Head. One of the rocky marvels of these weird regions is the " Pulpit " rock, over which projects a vast granite coping, fifty feet long, and twelve broad. It looks unstable, but is secure enough, and may yet last for ages. In these southern regions of England we have the wild- ness and much of the sublimity of the Scottish Highlands, mingled with and softened by a vegetation unknown in other zones of the island. At Penzance, the decomposed greenstone is marvellously fertile, and plants from Australia that will grow at Kew only under glass, here thrive out of doors. A perpetual southern spring reigns, but the near- ness of the sea to all points of the land tempers what would be an oppressive heat at seasons; and even in "winter" the days are comparatively warm, and the sun is nearly always shining. The mines are, of course, a source of inte- rest, but these hardly come within my present scope. Few, if any, counties of England present such examples of longevity among the inhabitants, and undoubtedly the purity of the atmosphere and the proximity of the sea to all points of the peninsula are in themselves highly hygienic Aug. 1, 1884.] ♦ KNOWLEDGE 05 conditions. The granite spine or ridge that divides the peninsula with its successive peaks — Brown Willy, 1,368 feet; Caradon Hill, 1,208 feet; Kit Hill, 1,067 feet ; and Hensbarrow Beacon, l,03i feet — help to complete the re- semblance of Cornwall to a miniature Italy ; and the fact that the Balm of Gilead — a species of tree flourishing in Arabia and Abyssiuia — grows out of doors sufficiently establishes the softness of the climate. Marazion in par- ticular, known as Market Jew, has special salubrity, being at the foot of a hill on St. Michael's Bay, and entirely sheltered from every cold wind. Marazion, by the way, is supposed to be the most ancient town in Cornwall, and is very near the famous Ictis, the great Tin Mart of ancient story. Svveeping round northwards, and facing the Irish Sea, we find the Devonian heights on the one haud and the seaward ending of the W elsh mountains have, between them, formed a coast abounding in picturesque features and in noble scenery. Proceeding northwards along the Cornish coast, under the shelter of the high lauds, we pass numerous points of interest like Padstow, Tintagcll, and, reaching the Devonian shores, pass Bideford, on the banks of the Tor- ridge, Barnstaple, and reach Ilfracombe, standing among picturesque and irregular hills, and having a harbour formed by veritable ramparts of rock. Here begin the special beauties of the Bristol Channel, the extension, in fact, of the magnificent estuary of the Severn. This is the grandest estuary of all Great Britain, and has a most irre- gular coast-line of 220 miles ; and here may be seen tides that rise to heights ranging at Bristol from 35 ft. to 70 ft. at Chepstow. The phenomenon of the boro is also a special marine feature, and shows the ocean advancing like a wall of water, as much as nine feet above the normal level. It is this bore or tidal wave that rushes up the broad mouth of the Severn, which, by the way, at its junction with the Wye, presents one of the most famous water views of the kind in all England. On the north of the Bristol Channel, Glamorganshire (in Welsh, Gwlad Morgan)hasa coast-line of full ninety miles, and includes the land of Gower, that re- markable peninsula projecting into the Bristol Channel with deeply indented and highly precipitous coast. Then comes the wild Caermarthen coast, the birthplace of Merlin, and having in Tenby what has been generally allowed to be one of the most beautiful and romantic places in these islands. It stands on a kind of promontory, and three miles away is Caldy Island, with many interesting archaeo- logical associations. The lodging-houses here are mostly on a high clitf, and the view across to Pembroke, on the shores of Milford Haven, is certainly unsurpassed for beauty. The grand approach to Pembroke is bv water, and this enables its castle, which is justly rankedjamong the most splendid monuments of antiquity in South Wales, to be seen to advantage. The town principally stands on the ridge of a long rock. Under the chapel of the castle is the famous natural cavern known as the Wogan, which commu nicates with the harbour. One matter worthy of special note for the tourist is that in Pembrokeshire, originally settled by Flemish emigrants, English is generally spoken, and, indeed, this county has sometimes been called the Little England beyond Wales. Milford Haven is a truly wonder- ful expanse of sea, landlocked by steep hills, rich with vegetation and abounding in splendid views from all points of the compass. As a harbour, the Haven is hardly equalled in the world, and it is entirely protected from winds by its green girdle of hills. It is full seventeen miles by two or three. Proceeding onward by the coasts we reach St. David's, once a splendid, and still an interest- ing place. Off Whitsand Bay there are six singular islets, quaintly known as the Bishop and his Clerks. Next we reach Fishguard, and thence to Cardigan on the mouth of the Tyvi. This was anciently Aherteif — i.e., the mouth of the Teif or Tiyvi. The scenery here is highly romantic, and the coast-line is marked by rocks of great grandeur. It is worthy of note that this Welsh river is believed to have been the very last retreat of the British beaver. Car- digan Bay is a fine semi-circular bend, having a coast of nearly 111 mUes, and being swept by a strong current from south to north, and obstructed by bars, it is rather dangerous for navigation. A great part of this grand bay is believed to have been formerly dry land, and had at least sixteen towns, and, tradition says, was entirely submerged during fearful storms in or about the year 520 a.d. This is decidedly a striking parallel to the submerged Lyonesse off the Land's End, of which I have spoken above. Cardiganshire, the great ma- ritime county of West Wales, rests on the lower Silurian slates, and sends down from its rugged hills abrupt slopes to a steep beach. This county is remarkable for containing full twenty lakes or Ihjiis, justly celebrated for their beauty, which is of the wUd and even terrible order, and for its romantic waterfalls, particularly that known as the Rheidol Falls, and the Devil's Bridge. "This is a single arch, crossing a chasm, and was diagonally erected by the monks of Ystrad Fflur Abbey, near the source of the Tyvi, in the thirteenth century. 'The stream of the Mynach descends impetuously from mountains about five miles, and roars beneath the bridge at a depth of Hi feet. The total fall of the Mynach is no less than 322 feet. It was this county that gave, in 834, a king to all Wales ; and throughout are many interesting remains of British and Roman camps, cairns, castles, and Druidical circles. Carnarvon is another of the romantic counties of Wales, and is traversed by the grandest mountains of South Britain. Here is the great Snowdonian range, culminating in Snowdon, 3,571 feet above the sea-level. The Menai Straits are well known for such features, of course, as appear in guide-books, and such glimpses of the special features as travel- lers to and fi-om Ireland may obtain in transitu. Ample British and Celtic remains abound here to occupy the antiquary, but it is in Anglesea — which means, by the way, the Englishman's island, that the richest store of archaeological and very ancient historic remains are to be found. This was the Mona of the Romans, and was the great stronghold of Druidical power. It has a coast-line of eighty miles, and possesses a milder climate than does the Welsh mainland, only it must be avoided in autumn, when the air is charged with very disagreeable mists. Beaumaris, with its ivy-clad castle, dating from Edward I., stands on a picturesque bay, and is a pleasant seaside resort in summer. From the Anglesea coast near the Tal y Moel ferry house, the town of Carnarvon, with the Menai Straits in the foreground and the lofty mountains of the Snowdonian range in the background, forms a picture of striking beauty. The Bay of Beaumaris is very sheltered and shallow, and at low water the Laven sands extend for miles. These, again, fn parallelism to Cardigan Bay, once formed dry and inhabited land, and were inundated in the sixth century. In the churchyard of Abergele, a Caer- narvonshire village, is a Welsh inscription, saying that there lies a man whose dwelling was three miles north, i.e., where now roll the breakers of the Irish Sea. Another pretty conclusive evidence of the fact that a great strip of land was here entirely submerged arises from the fact that the boles of some vast oaks have been discovered during extraordinaiy low tides. The lofty mountains of Wales, broken by the Bristol Channel to reappear as the Devonian, and then the Cornish high- lands save in their hard declivities on the west a new coast- 96 ♦ KNOWLEDGE . [Aug. 1, 1884. line, probably at some very remote period to this islan d ; and but for the Cornish islands there can be little doubt but that the land's end south would have been furnished by Devonshire. A remarkable feature of Carnarvonshire is the promontory of Llyn, which juts out to sea, and in- cludes many highly picturesque places, like Clynog, which, backed up by mountains, and with its houses half-hidden in refreshing foliage, presents the very perfection of a seaside resort where repose and natural beauties are the main desiderata. The principal town, however, on this remarkable promintory is Pwllheli. Some twenty-four miles away lies the Isle of Bardsey. Some portions of the coast are perpendicular, and others actually overhang- ing, producing a remarkable effect. Immense multitudes of birds build in the crevices of this cliff, and the collec- tion of their eggs is quite a staple occupation. On the south-east Bardsey is accessible. In 1840 the population numbered just 84. It is remarkable that no kind of reptile has ever been seen in Bardsey, which is in Welsh known as the Refuge of the Saints. At the end of the promontory is a bay in which every ship once entering must be inevitably stranded, as, from whatever quarter blows the wind, the current always sets powerfully in- wards, and among seamen on the coast this inhospitable and fatal bay is known vulgarly as Hell's Mouth. (To be continued). A CATASTROPHE AVERTED BY ELECTRIC WIRES. THE Scientific American learns by a letter from Rev. H. C. Hovey, that the new drill hall of the State University, at Minneapolis, was struck by lightning on June 12, with attendant phenomena of interest TTiis buDding, locally known as the Uuiver.-ity Colosseum, stands on a bluff overlooking the Falls of St. Anthony, occupying the highest gi-ound in the city. At 2 p.m. there were 1,000 children assembled on the stage, and about .3,000 persons in the audience. A thunder-storm arose, and while the children's choruses were going on, it was noticed that the series of electric lamps, fifteen in number, hanging from the dome, were lighted at each flash of lightning, going out again at once, and there was a sense of uneasiness pervading the people. Suddenly there was a loud report, as if of heavy ordnance, balls of fire were distinctly seen through the large skylight, and following the electric wires away from the building. Subsequent examination showed that the lightning first struck the flag-staff surmounting the door, thence pierced an oaken beam to which the staff was fastened, the splinters, or the concussion, breaking the glass in the skylight. An iron rod conducted the fluid to the network of electric wires below, where the charge was divided, a portion being harm- lessly distributed over the general circuit, and the remainder shattering several electric masts near the building. A workman on the roof had his shoe torn ofi" and his leg badly burned ; and another person in proximity to one of the masts was temporarily paralysed. There was a panic imminent at first, as every one instinctively sprang to his feet and confused cries and shouts were uttered. Dr. Thomas, with great presence of mind, had his orchestra play, and Herr Scaria came forward and sang. Thus reassured, people either remained to hear the music, or quietly left the hall. At night, an immense audience was present at the Colosseum to hear " The Creation," and quietly sat through another thunder-storm, seemingly satisfied that the electric wires were good lightning-rods. The lamps, however, worked fitfully, now blazing with startling brilliancy, and then going completely out, leaving the audience in total darkness, and then flashing iip again. Meanwhile the music went on as if nothing unusual had occurred, both soloists and chorus being pertectly familiar with the score ! What drew the lightning was the metallic ball surmount- ing the tall flagstaff fifty feet from the wires. The staff and girder to which it was attached were wet, hence be- came conductors, carrying the fluid along to an iron bolt, beside which it pasted through a heavy piece of timber, whence it leaped upon the electric wires, by means of which it escaped from the building. There is not the slightest doubt that the wires performed the duty of lightning-rods in this instance. Nor is there any doubt of the grave error of permitting a vast assembly to be gathered into a lofty, unprotected building on an eminence. The intensity of the current fused the fine wire circuit feeding the lamps, which accounted for the spasmodic working of the lamp.", the wonder being that they should have worked at all after being subjected to such a strain. Mr. Noyes, foreman of the Brush Company, tells an interesting experience. He was at work on the wires ) previous to the storm, and kept on after it burst, although aware of his danger. At the moment the building was struck he was splicing the wires directly above the central lamp, meanwhile taking every precaution possible under the circumstances. For a few minutes he lay xinconscious, and then, regaining his senses, descended to the ground. He says that he did not feel any pain until he reached terra Jirma, when he suffered intensely in his right foot. On examination he found that the bolt had struck his leg below the knee, tearing the clothing to shreds, bursting open his stout boot from heel to toe, and blistering the flesh as if with a hot iron. Tricycles ix Tictoeia. — The Postmaster-General of Victoria has it is said, decided to make a trial of the tricvcle postal delivery system at Portland, Sale, and Ararat. If the plan should be enc- cessful, he will have it extended to other districts at an early date. Electkic Lighting in London. — The Board of Trade have decided to proceed at once to revoke no fewer than twenty-five of the provisional orders which were gmnted by them last year, and subsequently confirmed by Parliament, for the electric lighting of London and its suburbs. Of this number twenty-three are orders which were obtained by the Metropolitan Brush Electric Light and Power Company, which has since gone into liquidation. These orders relate to the electric lighting of Barnes, Mortlake, Ber- mondsey, Chelsea, Chiswick, Clerkenwell, Finchley, Greenwich, Hackney, Holbom, Homsey, Islington, Limehouse, Poplar, Rother- hithe, St. George's-in-the-East, St. George the Martyr, portions of the parish of St. Giles, the parishes of St. Luke's, St. Olave, St. Saviour's, Sonthwark, Shoreditch, Tfhitechapel, and an order known as the Wandsworth order, which, however, relates to portions only of the parish of Clapham. Of the other two orders which will be revoked, one relates to the lighting of Kensington, and the other is an order granted to the Pilsen Joel Electric Lighting Company, with powers to light those portions of the parish of St. Giles not granted to the Metropolitan Brush Company. So far as London is concerned, the result, therefore, of the numerous electric-lighting orders which have been granted dtu-ing the past two years, is that only eight now remain in force — namely, the St. James's and St. Martin's order, which, with the Hanover-square, Strand, and Victoria district orders, are now held by the Edison and Swan United Electric Lighting Company, the Hampstead order, granted to the Hampstead Electric Lighting Company, the St. Paneras order, granted to the Vestry, the order for the lighting of Fulham, which was granted only last May to the West Middlesex Electric Lighting Company, and the order, also granted in May last, to the West London Electric Lighting Company, for lighting portions of the parishes of St. George's, Hanover-square, St. James's, Westminster, and St. Martin-in-the-Fields. Of these eight orders, the first five have already had their time extended within which to comply with the provisions of the orders, and unless these provisions are com- plied with before October 15 next, the powers will be lost, unless & further extension of time is granted. Aug. 1, 1884.] ♦ KNOWLEDGE ♦ 97 3RtbirU>S» SOME BOOKS ON OUR TABLE. ForM and Matter. By Professor Ludwig BUchner, M.D. (Loudon : Asher it Co. 1884.)—" Every scientific truth," said our great departed geolooist, Sir Charles Lyell, " passes through three stages. In the first it is deciied as absurd. Tlien it is said to be opposed to revealed religion. Finally, everybody knew it before." We arc forcibly re- minded of the verity and applicability of these words on openiug the fourth English (translated from the fifteentli German) edition of the now famous " Kraft und Stoff," whicli, at its first appearance, twenty-nine years ago, met with such a chorus of virulent abuse from orthodox journals of every shade of thought ; but which now would merely be held to push, perhaps rather to an extreme, views held by a large proportion of men of science in all civilised nations. The doctrine of the Conservation of Energy is now so firmly established that no one would seriously take the pains to attempt to controvert or deny it ; and, starting from the premises of the immortality of matter and the equal immortality of force, Dr. Biichner essays to explain the entire phenomena of the visible universe upon strictly material principles, to the exclusion of any extra or supernatural agency whatever. In much that he says he would seem merely to have anticipated the irrefragably established facts of modern scientific research ; while in other parts of his work it may, we think, be fairly said that his argument rests on assump- tions for which adequate proof (in the existing state of our knowledge) is not offered. That every single thought, for example, is accompanied by an actual molecular change — or rearrangement — in the brain is as certain as any fact in physiology. It is, however, taking a very considerable stride to assert with our author that such molecular change or vibration is thought. It may not be un- believable, but it is certainly inconceivable, that con- sciousness, reflection, and desire can be expressed in terms of motion ; and without actual proof of the possibility of such expression. Dr. Biichuer's final conclusions must drop to the ground. It is, of course, open to him or to his disciples to retort that where so much that he originally advanced has been shown to be absolutely true, every accessiou to human knowledge must tend to include a largi?r and larger proportion of what remains in tlie same category. This, however, is an argu- ment whose fallacy may be shown by applying it to the contentions of certain people in connection with astrology, spiritualism, itc, and which need not detain us here. On one point there can be but little doubt or dispute — that a work which has passed through sixteen German, six French, four English, three Italian, and two Hungarian editions, and has been translated into thirteen living languages, must be eminently well worth reading, whether we agree with or dissent from its author's conclusions. The Food Reform Magazine (London : National Food Reform Society.) — This is a vegetarian organ, seemingly devoted to the attempted conviction of mankind that their temporal salvation depends wholly upon their never touching a bit of meat. The whole thing is overdone to an extent which must repel every unprejudiced and im- partial inquirer. We note, by the way, on the cover of this magazine an announcement that letters on " Vege- tarianism" have been inserted in (int. al.) Knowledge; but we do not find any mention of the fact that Sir Henry Thompson, who had been publicly quoted by members of their society as an advocate of vegetarianism, publicly con- tradicted this false and dishonest impeachment on page 407 of our 1st Volume. Lessonsin Social Economi). Bv James Rdstz. (London: Educational Supply Association). — Why Mr. Runtz has considered it necessary to dub his work " Social " Economy is by no meaus apparent. It is a treatise in a simple and apprehensible form on what every other writer on the subject, so far, has called ])olitical economy ; and, as an introduction to that science (if it be a science) for the use of teachers in elementary schools, it leaves little to be desired. The tendency of modern elementary education would seem to be towards the loading of the wretched children's minds with a mass of heterogeneous subjects without the smallest thought or care wliether they can be understood or assimilated. For earning the " grant," probably political economy is as useful — or useless — as many other things taught ; and, admitting this, Mr. lluntz's book is a good and trustworthy one for the teacher's use. All Epitome of History : Ancient, Media'vaJ, and Modern. By Carl Ploetz. Translated by Wm. H. Tillinghast. (London: Blackie &, Son.) — Herr Ploetz has by no means mis-named his book in calling it an epitome, for he has packed what is practically a history of every nation in the civilised world within the limits of 564 pages. And yet, like all German work, his is done well and thoroughly, and the student who requires a conspectus of the life of any civilised nation at a given epoch will find it in these pages in a simple and convenient shape. While myth has not been excluded, the chronology is of the most orthodox description. The claims of the Chinese, the Ancient Egyptians, ikc, to great antiquity are entirely pooh- pooh 'd, and everything is smoothed down and squared off to fit in with the hypothesis of the supposed origin of mankind on the earth some 0,000 years ago. For the purpose, however, of such a work as that before us this is scarcely material, as it is only when we emerge from the region of legend into that of the contemporary chronicler that history — as such — possesses the slightest value to the student. The translator has not only done his immediate work well too, but has made considerable additions to the text ; in fact the book, taking it altogether, is one of unquestionable value. It is supplied with a first-rate index, which wUl be appre- ciated by all who have occasion to consult it. A Digest of English History, 1689—1760. By M. GuTTERiDGE, B.A. (London : Relfe Brothers. 1884.) This little volume is really what it professes to be, and is something more than the mere cram-book into which so many recent epitomes of history have degenerated. This is doubtless due to the fact that Mr. Gutteridge deals only with a limited period in our national annals, and hence he is enabled to expand his narrative to an extent which renders it intelligible. He gives the leading characteristics of each of the great battles fought during the seventy-one years covered by his digest, and deals with other historical details in a way similarly adapted to impress them on the student's mind. He has produced a useful little book. Text-hook of Practical Solid or Descriptive Geometry. By David Allan Low. Part I. (London : Longmans, Green, ifc Co. 1884.) — Mr. Low has produced a little book of real value to the student of Architectural or Engineering draw- ing, containing a large number of problems and a corre- sponding number of illustrations. After stating each pro- blem, he gives a general solution of it, and this is followed by its application to one or more examples, as the case may be, whose working is, as we have just hinted, always thoroughly elucidated by a diagram or diagrams. He 98 ♦ KNOWLEDGE ♦ [Aug. 1, 1884. claims no moi-e than is due to him when he expresses the hope that his endeavour to meet the wants of both ele- mentary and advanced students has been successful. Half-hours at. the Sea-side. By J. E. Tatlor, Ph.D., F.L.S., F.G.S., etc. (London : W. H. Allen & Co. 1884.) — The holidiiy-maker, whose idea of a sea-side trip is com- prised in the daily succession of the bath, the liovel, and the promenade, need only open Dr. Taylor's work to see what a wealth of intellectual pleasure and recreation lies altogether outside of such stock devices for " killing time." There is no such rest, either for mind or body, as a total change of occupation ; and more delightful occupation than the study of the myriad forms of life that people our shores it would be difficult or impossible to find. Beginning with a half-hour with the waves themselves, our author goes on to instruct us in the employment of the microscope, the construction and stocking of temporary aquaria, the use of the tow-net and dredge, the anatomy and physiology, manners and customs, of sea-weeds, sponges, sea-worms, corallines, jelly-fish, sea-anemones, sea mats and squirts, sea-urchins and star-fish, .shell-fish, and Crustacea. The reader who takes this book with him in his summer or autumn jaunt to the coast, will find that it will supply him with a perennial source of amusement. He who weak- mindedly omits to do so, will cut himself off from an incal- culable amount of pleasure of the most novel and exciting kind. Bringing it to Booh is an advertisement of a Mr. Eglin- TON a (so-called) " Medium," which we decline to forward or further by taking any more notice of it. Professor Ray Lankester and Dr. Carpenter would be the fittest people to deal with this person in the outset, as Mr. Flowers, at Bow- street, would be at a subsequent stage of the proceedings. THE FACE OF THE SKY. Tkom Augu-st 1 TO August 15. By F.R.A.S. THE usual daily watch for spots and facnlas will be kept upon the SuTi. A picture of the Kight Skj' will be found in Map Till, of " The Stars in their Seasons." Minima of the variable star Algol (Map I. of "The Stars in their Seasons") will occur at 2h. 35m. a.m. on Aug. 13, and at the more convenient hour of llh. 23m. p.m. on Aug. 15. The reader should keep a careful watch on the sky during the nights of the 9th, lOtb, and 11th (notably on that of the 10th) for that marvellous shower of shoot- ing stars which has been familiar from classical antiquity ; and mediaevally designated " St. Lawrence's Tears," is now known more philosophically as the " Perseids," from the fact of all their paths appearing to radiate from a point in the Constellation Perseus (" The Stars in their Seasons," Map I.). These bodies were shown conclusively by Schiaparelli to be travelling in the orbit of a comet (2) which appeared in 1862. Moonlight will interfere to some extent, though not to a great one, with their observation this year. Mercury is an evening star, and may just possibly be picked up close to the horizon after sunset during the fortnight over which our notes extend. Venus is a morning star, and a most brilliant object she is in the eastern sky before sunrise ; in fact, by a device akin to that explained on p. 421 of Yol. T., she may be found, and easily seen with the naked eye in bright sunshine, abont the time when these notes terminate. No other planets are at present visible. The Moon enters her last quarter at eight minutes past three in the early morning of the 1-lth, so that the first two or three days of August will probably suit the ordinary observer best for examining her in the telescope. She will occult three stars at convenient hours during the next fourteen days. The first is BAG. 6292, a sixth magnitude one, which on the 3rd will dis- appear at the Moon's dark limb at 7h- 32m. p.m., at an angle of 130° from her vertex ; reappearing at her bright limb at a vertical angle of 190° at 8h. 4m. Then, on the 14th, another sixth magni- tude star, 63 Tauri, will disappear at the bright limb of the Moon fifty minntea after midnight, at a vertical angle of 49°. It will reappear at the dark limb at Ih. 45m. the next morning, at an angle from the vertex of the Moon of 253°. On the same night (the 14th) BAG. 1351, a star of the sixth and a-half magnitude, will disappear at the bright limb eight minutes later than 63 Tauri at an angle of 12° from the vertex ; but it will reappear sooner, I.e., at lb. 34m. a.m. on the 15th, at the dark limb, at a vertical angle of 290°. The moon is in Ophiuchns when these notes begin, but at 6 a.m. on the 3rd enter Sagittarius. Hence at 6 p.m. on the 5th she passes into the N.W. portion of Gapricomne ; there she remains until 10 a.m. on the Cth, when she crosses into Aquarius; traversing Aquarius it is the same hour on the 9th ere she enters Pisces. Her passage across this great constellation occupies her until 10 a.m. on the 12th, at which time she crosses into Aries. She leaves Aries at 2h. 30m. a.m. on the 14th for Taurus; she is still in Taurus when our notes terminate. iBi^ftllanrn. There is an article on " Scintillation," by M. Ch. Montigny in the number of Ciel et Tcrre, for July 15, containing an account of the naked-eye observations of that phenomenon by M. Ch. Dufonr. It should be read by all interested in the curious subject to which it refers. Accident feom Light.xixg. — It is stated that on Wednesday, the IGth inst., during a storm, a house in the village of Chantemerle, Geneva, was struck by lightning and set on fire. There being no water available to extinguish the flames the &ie spread, and the whole village was reduced to ashes. Steam Ploughing in the West. — Recently, at Fargo, Dakota, a traction engine drew eight ploughs, turning a sod 4 in. thick as even and well as could be done by horse-power, and at a rate of over twenty-five acres per day. The cost of steam-ploughing is rated at about 1 dol. per acre as against 3 dels, per acre by horse- power.— Engineering. Be,ssemek Steel. — The production of Bessemer steel in the principal countries of the world last year is estimated at 4,852,956 tons. This total was made up as follows : Great Britain, 1,553,380 tons ; United States of America, 1,119,576 tons ; Germany, 955,000 tons ; France, 440,000 tons ; Belgium, 220,000 tons ; Sweden, 50,000 tons J Russia, 340,000 tons ; and Austria, 175,000 tons. WEDNESD.iv's standard says : — " Litigation in respect to patent rights has hitherto impeded the development of electric railways. The Patent Office has now decided in favour of S. D. Field against Edison and Siemens. The first railway was opened at Cleveland, Ohio, on Saturday, and others are expected to be constructed now in quick succession." The Raihcay Review says : — Bnffalo claims to have the tallest telegraph-pole in the world. The Western Union put up one measuring 70 feet, and thought thereby to cut the Baltimore and Ohio off from getting its wire to its office, but the Baltimore and Ohio got a pole 90 feet high, 8 inches at the tip, and set it up within 5 feet of the Western Union pole, so that the two now point to heaven in parallel lines, with the Baltimore and Ohio a trifle ahead. A SULPHUR deposit exists at Djemsa, Suez, in a perfectly rainless desert on the African coast, very near the sea, and constituting a hill 600 ft. high, whose sides are blasted down as in quarrying stone. Some 200 Arabs, employed under French engineers, succeed in mining ten tons a day. A similar deposit occurs at Ronga, 500 miles from Suez, also near the coast of the African continent, which differs only in being buried under other strata, so that mining is necessary. During a slight thunderstonn which passed over the Lake dis- trict on Saturday morning last, the corning house at the Black Beck Powder Mills, near Ulverston, was struck by lightning. A terrible explosion ensued, completely wrecking the btiilding, and instantaneously killing three men who were inside. Another man was standing outside the corning house, and the flames from the explosion set fire to his clothing, but by throwing himself into an adjoining brook he escaped with a severe scorching. Facts co^•CEENING Vaccination. — At a meeting of the Vaccination Officers' Association, held on Saturday last, a cordial vote of thanks was given to the National Health Society for issuing their pamphlet entitled " Facts concerning Vaccination." The Association ex- pressed their appreciation of the " thoughtful kindness which prompted the society to assist the vaccination officers of the Metropolis in the discharge of their often diflicult duties." We Aug. 1, 1884.] • KNOWLEDGE ♦ 99 ara informed that the pamphlet in question ha'5 now been distributed from house to house in most of the districts in the Metropolis where small-pox is epidemic, and that the demand for it still continues. Something like 150,000 copies have already been issued since the present epidemic began. The Standard says: — "The Midland Railway Company having decided to offer premiums for the best-kept station gardens throughout their system, a kind of Renaissance may be looked for in this branch of horticulture. Other companies are not unlikely to follow suit, and if flowers and fruit are to be ejects of compe- tition among station-masters and porters, paint and paper, draught- less waiting-rooms, and a constant regard for the comfort of their passengers may, ere long, be among the objects in which chairmen and directors will struggle to excel. In encouraging their servants to beautify their wayside premises, the Midland authorities are taking an excellent means to increase their business, by encouraging passengers to travel by a line where the carriages are good, the stations pretty, and everybody ready to oblige." Six Mo.nths' F.^ilures (in the States). — The failures for the six months ending July 1 are reported by R. G. Dun on'<-nde level- geared 48 in. " Coventry Rotary" roadster. The journey down, in the heat of the day, occupied 1 h. 50 m., including stoppages. He had been suffering two days previously, and his M.D. ordered him to take out-door exercise, and this was how he took it ; it is need- less to say he is now quite well. — The Tricijclist. The Hudson's Bay RorxE. — A report on the opening and closing of navigation at York Factory on the west coast of Hudson's Bay, with observations extending from 1828 to 1880, has been communi- cated by Mr. W. Woods to the Hudson's Bay Company. The latest recorded date of open water in spring is June 1, the earliest closing of navigation November 3. The earliest recorded date of opening was May 4, the latest day of closing, December 9. There is, there- fore, some six months of open water on the average in the bay itself, but the communication with the bay and the Atlantic can only take place through Hudson's Straits, and this passage is only clear in July, August, and September, with probably a part of October. Further information on this head is much needed, and it is satisfactory to learn that Hudson's Bay is shortly to be properly stirveved, for the question of its navigability is a most important one to the settlers of Manitoba and the Saskatchewan, since they can ship their exports for Europe by this shorter route, instead of by the Red River and the St. Lawrence. — Engineering. M. Pasteuk's Expekimexts ox Dogs. — The series of tests which, at M. Pasteur's own suggestion, were to be made with a view to confirming his theory of protective vaccination by attenuated hydrophobic virus, have now been partially completed ; and the result is a complete justification of the faith of those who had con- fidence in M. Pasteur's statements. So far, fifty-seven dogs have been made subjects of experiment under the supervision of a com- mission appointed by the French Government, and under conditions arranged between the latter and the illustrious discoverer himself. Of these fifty-seven dogs, nineteen were already atHicted with hydrophobia ; and of the remaining thirty-eight, one-half had been previously vaccinated with the attenuated virus. All the thirty- eight were then bitten by the nineteen rabid animals, and the result watched. This completely confirmed the truth of M. Pasteur's assumption of protective power on behalf of the cultivated vaccine matter, for every unvaccinatcd dog was speedily attacked with unmistakable symptoms of rabies, ending in death; whereas the protected dogs were unaffected by the injuries they had received, and are still in perfect health. In order, however, to make certainty positive, these nineteen dogs will be kept under observa- tion for a full year, when, if they still remain healthy, it is assumed that sufficient proof of their being protected will be given. — The Medical Press and Circular. The Utilisation- of the Niagara Falls. — At a recent meeting of the American Association of Civil Engineers, Mr. Benjamin Rhodes described what had been done, and what might be done, towards the utilisation of Niagara for electrical purposes. He said : — " The power of Niagara can be estimated very approxi- mately. The average flow of the river according to many careful measurements is 275,000 cubic feet per second. The fall in the river through the rapidsimmediately above the fall is 65 feet. The height of the falls is 165 feet, maki'ng a total of 230 feet ; thus we have for the whole power 7,000,000 horse-power. To utilise this amount of power by water-wheels, generate electrical currents, and transmit to various cities mthin 500 miles, would necessitate a plant representing at least 5,000,000,000 dols. Such figtires as these give some idea of the enormous amount of power here in reserve." He states that on the Canadian side the entire use of the falls i^» represented by a small over-shot wheel, which pro- pels a pump ftimishing a meagre supply of water to the adjoining village. On the American side there are five separate raceways, developing in all 800 to 1,000 horse-power. After de- scribing the hydraulic canal, the greatest power now in use at Niagara, he says : — " Further developments of power at Niagara may be made at little expense. "The hydraulic canal can be deepened and widened, and wheels may be set under greater heads, the total amount thus made available here being equal to the neces- sities of many years. It may safely be said that the use of Niagara has just begun. Low water is unknown; troubles from ice are slight ; hours of use are not limited to eight or ten, but 24 hours in the day, and 365 days in the year, and unlimited power is ready, making this the most reliable, as it is the grandest, water-power in the world." At a recent meeting of the American Society of Civil Engineers, observations upon the temperatures of the earth as shown by deep mines were presented by Messrs. Hamilton Smith, jun., and Edward B. Dorsey. At the new Almaden qmcksilver mine at California, at a depth of about 600 ft., the temperature was very high — some 115 deg. — but in the deepest part of the same mine, 1,800 ft. below the surface and 500 ft. below sea-level, the tem- perature is very pleasant, probably less than 80 deg. At the Eureka mines in California, the air 1,200 ft. below the surface appears nearly as cool as 100 ft. below the surface. Mr. E. B. Dorsey said that the mines on the Comstock vein, Nevada, were exceptionally hot. At depths of 1,500 ft. to 2,000 ft., the ther- mometer'placed in a fresh-drilled hole will show 130 deg. Very large bodies of water have run for years at 155 deg., and smaller bodies at 170 deg. The temperature of the air is kept down to 110 deg. by forcing in fresh air cooled over ice. Captain Wheeler, United States Engineers, estimated the heat extracted annually from the Comstock, by means of the water pumped out and cold air forced in, as equal to that generated by the combustion of 55,560 tons of anthracite coal or 97,700 cords of wood. Observa- tions were then given upon temperature at every 100ft. in the Forman shaft of the Overman mine, running from 53 deg. at a depth of 100ft. to 121-2 deg. at a depth of 2,300ft. The tempera- ture increased : — 100 ft. to 1,000 ft. deep, increase 1 deg. in 29 ft. ; 100 ft. to 1,800 ft. deep, increase 1 deg. in 30-5 ft. ;" 100 ft. to 2,300 ft. deep, increase 1 deg. in 32-3 ft. A table was presented giving the temperatures of a large number of deep mines, tunnels, and artesian wells. The two coolest mines or tunnels are in lime- stone— namely, Chanarcillo mines and Mont Cenis ttmnel, and the two hottest are in trachyte and the "coal measures" — viz., the Comstock mines in trachyte and the South Balgray in the " coal measures." Mr. Dorsey considered that experience showed that limestone was the coolest formation. In repli/ to numerous letters and communications addressed to the office of Knowledge, its Editor hegs to annoimce that he has noiv concluded his Lecturing Tour, and has, in fact, definitely ceased to lecture altogether. Should he {which is very doubtjul) at any future time resume his lectures on Astronomy, due and ample notice will he given of such res^trnption in these columns. 100 ♦ KNOWLEDGE ♦ [Aug. 1, 1884. " Let BCnowledge grow from more to more." — Alfred Tenntsos. Only a small proportion of Letters received can possihly he in- serted. Correspondents must not he offended, therefore, should their letters not appear. All Editorial communications should he addressed to the Editob of Knowledge; all Business communications to the Publishebs, at the Office, 74, Qreat Queen-street, W.C. If this is not attended to DELAYS ABI8E FOB WHICH THE EDITOR IS NOT RESPONSIBLE. All Remittances, Cheques, and Post Office Orders should he made payable to Messrs. Wyman & Sons. The Editor is not responsible for the opinions of correspondents. No COMMUNICATIONS ARE ANSWERED BY POST, ETEN THOUGH STAMPED AND DIEECTED ENVELOPE BE ENCLOSED. SOLAE GLOW. [1350] — In connection with Capt. Noble's letter (13-i4, p. 77), it may be also of interest to mention that the solar glow is a striking object here in the north-west quarter of the heavens on any tolerably clear evening at aboat an hour and a-half after snnset ; and likewise in the north-cast before sunrise. The colour of the meteor is not quite white, bat seems to be slightly tinged •with yellow. K. Phillifs. Northam, Bideford, July 2C, 188-i. LIGHTNING— VISIBLE LUMINOUS TRACK OF A METEOR. [1351] — The record of Thunderstorms which appeared in your issue of 25th instant induces me to send you these few lines, not 80 much for the purpose of telling you that one passed over my house on July 4 (during which one tree was struck in the front lawn, another within twenty paces of the hall door, and another about a quarter of a mile in the rear), as to remark that, in my humble opinion, the conclusion arrived at some time ago in your columns — that, because the duration of a flash of lightning is but about a millionth part of a second, therefore the eye cannot detect its direction — is an erroneous one. For not only have I seen lightning descend from the clouds, and dart from cloud to cloud, but ^also ascend out of the ground; the explanation of which facts, as contrasted with the aforesaid conclusion, appears to me to be very simple, viz., that the electric spark (which, owing to its velocity, appears as a flash) must subtend some angle while passing tlirough the air, which angle is necessarily reproduced in miniature on the retina, the consequence being that the optic nerve conveys to the brain, in exact sequence, the impressions made npon its terminal ramifications. I further wish you would kindly ask your readers whether any of them recollect having observed the track of a meteor remaining visible long after the meteor itself had vanished, as I did on one occasion for about half an hour ? Also, can you explain the " quare and quomodo" of such an unusual occurrence ? W. A. July 26, 1884. [I have myself seen lightning ascend from the earth to a cloud : and hear that this phenomenon was witnessed by a well-known contributor during a heavy storm, on Thursday, the 24th nit. — Ed.] LIGHTNING. [1352] — I am surprised that none of your correspondents have referred to the copy of the photograph of a flash of lightning, which appeared in yours of the 4th inst., and which is certainly quite unlike the conventional lightning-flash as it appears in paint- ings, &c. I only recollect once getting a good side-view of a thunderstorm. I was looking on at a cricket-match in the Phoenix Park, Dublin, and the storm took place in the neighbourhood of Kingstown. It is some years since, but I cannot fix the precise date. I saw a large number of lightning-flashes, all of which strikingly resembled the photograph in question, though in some cases the lines were, I think, a little more wavy In both cases the breadth of the flash was very perceptible, and I should expect to hear that the area of its section was considerable. Nevertheless, when the earth is struck by lightning the surface of contact appears to be very small. Possibly the flashes which I saw and that which was photographed by Mr. Gurley presented exceptional character- istics. Perhaps some of your readers could throw some light on this subject. — I remain, W. H. S. MoNCK. 13, Belvedere-place, Dublin, July 26, 1884. PARTRIDGES : THEIR LOVE OF YOUNG. [1353] — One morning here, after a heavy thunderstorm during the night, accompanied by deluges of rain and a great fall in tem- pera! ure, the keepers came npon a family of partridges, all dead — the I lareut birds crouching close together in the grass, their nine little ones between them, pressed as closely as possible to their sides, the inside wing of each parent bird extended, wing over wing, making a double roof for the protection of their family, and in this position these devoted birds had perished, trying to the last to save their young ones at the cost of their own lives. The men who found them seemed quite impressed, and said " It was a pretty picture ! " Swigell House, Northumberland, M. J. C. July 23rd. OVERHEAD WIRES. [1354] — Let me say a few words about overhead wires, the danger from which I think may be easily obviated. At present the posts to which the wires are fastened are placed on the rid^je of the roof. Let additional posts be placed on the eave in the street-front of the building on each side of the street, and directly opposite to each other. I assume the distance betwixt these posts across the street would be sixty-five feet, and the height of the building and post together from the ground ninety feet. If so, and the wire broke off, even riosr from the post, it would swing twenty-five feet above the traffic in the street, and could not, therefore, interfere with it. The posts could be made longer or shorter, so as in all cases a difference of twenty to twenty-five feet should be obtained. J. W. BCSK. DIVISIBILITY BY SEVEN. [1355]— When a vulgar fraction whose denominator is 7 is reduced to a decimal fraction, its equivalent is a repetend con- sisting of six figures, in which, when extended indefinitely, the 7th, 13th, 19th, &c., figures are repetitions of the first, and if the first figure be added to the 4th, 10th, or 16th, ic, figures, the snm is = unity or f . The 1st figure may, for convenience, be called the complement of the 4tb, 10th, or 16th, &c. Now, if a number be divided into terms of three figures each, and marked 0, 1, 2, 3, ic, from the right, it is evident from the above that any even term divided by 7 will have the same re- mainder, whether it is taken at its abstract or its local value ; also, that any odd term divided by 7 will, taken at abstract value, have a remainder which is the complement of the remainder when the same term is taken at its local value. Take the following example : — Terms. 2. 1. 0. 246,474,585 -i-7 = 35,210,655? or Local value 246,000,000-4-7 = 35,142,857^ „ 474.000-7-7= 67,714^ „ 585 -=-7= 83f 35,210,655? Abstract Value. 246-r-7=35f true fraction. 474-i-7 = 67f complement of true fraction. 585-=-7 = 83f true fraction. Taking local values, the remainders are }, f, i, whose sum gives the true fraction. Taking abstract values, the remainders are f , f, 7, and the true fraction is to be obtained from them thus, | — f •*- f = 0; for the same fractional result is obtained whether we add f to a quantity or subtract f from it, since the difference between the two results must be (J + 4 = ) unity. If, therefore, the even terms be called plus and the odd terms minus, and if their sum be divisible by 7 without a remainder, then the whole number is also Aug. 1, 1884] ♦ KNOWLEDGE 101 BO divisible. If there be a remainder, it will either be the true remainder or its oompleraent, according as the sum of the plus terms is greater or less than that of the minus terms. The extreme left-hand term may consist of less than three figures. William Si.vgers. LETTERS RECEIVED AND SHORT ANSWERS. J. Greevz Fisiiek. Forgive me. I do not "discountenance improvements in spelling because reformers are not unanimous," but because I regard the ortliography in which is enshrined the noble diction of Shakespeare, Milton, Pope, Addison, Macaulay, and Tennyson as quite good enough for me. As to the destruction of all traces of the etymology of words by " fonctic vagariz," I need say nothing to any philologist. I am much more disposed to sympathise with you in your protest against the meaningless limi- tations of the halfpenny postage. — Hector. The so-called " storm- glasses" are simply glass tubes (not air-tight) filled with a solution of camphor, nitrate of potash, and sal ammoniac. They are hygro- meters, if they are anything, but both light and temperature affect them. For any scientific purpose they are worthless. — Wm. Wilsox, M.A., LL.D. Accepting Colenso's example as one illustrating Common Measure, yon are obviously right in what you say as to his definition. — D. Wixstaxley dreamt on July Sth that his ex-sweet- heart came to say " good-bye" on the very morning on which (as he subsequently discovered) she was married to some one else. He also dreamt, on the 1-tth, a medical man but slightly known to him died on the floor of his (Mr. W.'s) bedroom. This gentle- man did die, in his own bed, early the next morning. My correspondent goes on to suggest that certain sorts of suppers may " yield prophetic dreams," which is too much for me. — Edward F. Hoerale. Without yourself taking the trouble to attend any course of lectures, you will, I think, find in Weinhold's " Introduction of Experimental Physics " ample material for such instruction as you propose to impart ; and you might even take the successive chapters of " Facts Aronnd Us " — a little book published by Stanford's — as the basisjof a series of lectures to them. I cannot possibly make an appointment for an interview, nor undertake to see any one personally in connection with matters discussed in these columns. — Thomas Maclean. Does it ever strike you that I have scores — not to say hundreds — of correspondents to deal with, and that in the tremendous pressure which exists upon an editor's time, it is quite possible (and even excusable) for him to overlook papers among those which descend in shoals on his devoted head ? I have not communicated your notions to Messrs. Browning and Wenham. You must do so yourself if you wish them brought before those gentlemen. — William Worslet. I do not print the letter on cholera which you send, inasmuch as it contains internal evidence that the " Rev. Dr." who penned it is ignorant of the very rudiments of physiology and pathology. — Ax Exile, while pro- testing against the selection of Ireland as an illustration of a country sunk in the lowest depths of superstition, points out, not wholly without reason, that past misgovernment may be to some extent held to be at the bottom of such a deplorable state of things. — Oxford asks this "question": Is it possible to obtain 360 different positions of the letters a, b, c, d, e, f, by means of the following two methods of transposition only, (i) and (ii) a, h, c, d, e, f a, b, c, d, e, f a, d, b, f, c, e , the last position being a, i>, c, d, e, f ? We /, d, a, e, b, c commend this to readers with plenty of idle time on their hands. — Edward .S. Haxsox points out that the " Design for a Parlour Organ," which we extracted from the Scientific American on p. 5S, was copied from the Building Neios into the EngHsh Mechanic of March 28 last, and was appropriated by the American paper without any acknowledgment at all. Thanks for your details anent the English translation of Fontenelle. — E. D. Warring. When a man submits his views for publication, he, ipso factor invites criticism upon them. You surely wanted my candid opinion of yours, and not an utterly insincere compliment. — Fred. Jackmax. WiU you kindly read the paragraph at the bottom of the first column on p. 62, where if is definitely stated that I have given up lecturing altogether ? — Kemts. I am unfortunately unable to give the address of the Cremation Society. Perhaps some reader of Knowledge will kindly do so. — J. H. Hayward. I am, I regret to say, out of town. — St. E. You can scarcely do better than get the " Human Physiology," by Dr. W. B. Carpenter. — Eye- Wit- ness. I do not think that either of my works which you name would render you more assistance than those which you possess. "The Stars in their Seasons " is a reprint of the maps which appeared monthly in Vols. I. and II. of Kxowledge. If you merely want the old constellation figures, get the " Six Star Maps on the Gnomonic Projection," now published by Letts's, but originally issued many years ago by S.D.U.K. 0av iHatljematiral Columm EASY LESSONS IX CO-ORDINATE GEOMETRY. By Richard A. Proctor. Problems ox the Straight Line. "TTTE proceed to discuss the equations to lines fulfilling given con- V 1 ditions, and also to examine some problems with which it is necessary the student should be familiar. 61. Prop. — To determine the form of the equation to a straight line passing through a ijiven point. Let x' y' be the co-ordinates of the given point. Now we have already seen that the equation to a straight line passing through x' y', and inclined at an angle whose tangent is m to the axis of X is y — y^ = m (x— i') (0 We might have obtained this equation as follows : — Let the equation to the required line be y = mx + c (ii) then, since the line passes through the point x' y', equation (i) must be satisfied when x ' is written for x, and y* for y ; therefore y' = mx'-^c (iii) And subtracting (iii) from (ii) we clearly obtain equation (i). This amounts to the elimination of c between equations (ii) and (iii). Instead of eliminating c we might have eliminated m ; thus, sub- stituting for m in (ii) the value given by equation (iii) we get v' — c this represents a straight lino passing through the point x' y' and having an intercept c on the axis of x. The equation will clearly assume different forms according to the condition we suppose the straight line to fulfil besides passing through the given point. We shall now consider the equations of lines fulfilUng such conditions. It is well to note in passing, how- ever, that whatever form of equation to the straight line be adopted in place of equation (ii), we obtain when the constant term is eliminated by subtraction, an equation of the form x-x' + l{y-y') = 0 Thus if in place of (ii) we take the equation y , we get in place of (iii) or subtracting a b a b • X' y • = 0 similarly from the equation X cos a -i- y sin a = p we should obtain (x — x') cos a + {y — y') sin a = 0 and finally from the equation Ax-hBy-hC = 0 we should obtain A (.r-x')-HB(!/-v')=0. It is important that the student should note these results. They show that in this particular case a relation subsists which we shall presently show to hold generally. The equations X— a?' =0, and y — y'=0 represent lines whose intersection determines the point x' y', and it appears that the equation formed by combining these two equations into a single equation of the forms X — x' -I- a const, (y — 'y')=0, represents a straight lino through the intersection of the lines represented by the two equations so combined. 62. Prop. — To determine the equation to a straight line passing throxigh two points. Let Xi !/i be the co-ordinates of one of the given points, X; y, those of the other. Then it follows from the preceding article that the equation of a straight line through xi yi is of the form V — y\ = m (r — .T,) (i) where m is the tangent of the angle which the straight line makes with the axis of x. If the straight line represented by (i) passes 102 KNOWLEDGE [Aug. 1, 1884. through the point x^ y^ (i) must be satisfied when Xo is written for X and 1/2 for i/, thus './; — i/i = m (^2— a^i) that is substituting this value of m in (i) we obtain the required equation, viz., 2/-Vl=^2Zli (a; -a:,) (ii) X« — Xi an equation which may be written in the easily remembered form V-Vi_ x-x^ y2 — V\ ^2— a:i CoK. — We may write (ii) in the form y{x^-x,) +y^{x — x.2) + y.,(xi — x)=0 (iii) This amounts to the statement that if « v be the co-ordinates of any point on the lino through Xji/, and Xay^, then the area of the triangle formed by joining the points aJii/,, x.^y^ and x y ia zero, — a consideration from which we might have deduced the equation required. Since (iii) may be written x(yi-y-:) +y(x2—Xi) + x0« — y,x.. = O the intercepts on the axes of x and y are X2V1 - -f l!/2 and iToj/i — ^iy» Vi-y^ x,-x.2 (To he continued.) (Bur Cf)t65 Column. By Mephisto. SELECTED PROBLEMS. No. 120. Buck. Whitb. White to play and mate in two moves. Xo. 121. Black. Whits. Keprinted from p. 80 on account of misprint. ^Vhite to play and mate in two moves. Ending from actual play. Amateur. Black. Whixb. Mr. Waters.- White to play and win. ANSWERS TO COKRESPONDENTS. ,*, Please address Chess Editor. Geo. W. Thompson. — You are quite right; we ought to have pub- lished the reply to Black's defence of Kt to Bsq — that is, Kt x P in Carpenter's problem. E. W. Young. — Regret to say problems not suitable. W. — You say that yon would cheer/idly have played 50. P x BP in the ending given in Kno^vledge of July 18, expecting 50. P x HP 51. P to B5, when, I am afraid, on Black playing K to Q4, yon would have become rather sad. No doubt we have seen the problem, but cannot recollect it. Is it not unsound ? Walter. — We reprint the position correctly. Conect solutions received from M. T. Hooton, Chas. T. Wilbra- ham, G. W. Thompson, Uncle John, C. T. G., The Owl. The Norwood Revien: says that a new Chess Club in in course of formation ; it will assemble in a locality near the station, and will begin in September next. OONTKNTS OP No, 143. FAGB Dreams. V. By Edward Clodd ... 65 The .4.ntarctic Kegious. By E. A. Proctor 66 Sensation in a Severed Head 67 The Electro-Magnet. By W. Slingo. (Itlu>.) Other Worlds than Ours. By M. de Fontenelle. With Notes by Eichard A. Proctor NoTel Tricycles. By John Browning 68 69 70 riam The International Health Exhibi- tion. IX. (niut.) 71 Thunderstorms 73 BcTiews 76 Miscellanea 76 Correspondence : Dickens's Story Left HaU Told (No. 139)— The Solar Glow, 4c 77 Our Mathematical Coloma 79 Our Chess Column 80 SPECIAL NOTICE. Part XXXIII. (July, 1884), now ready, price Is., post-free, 1b. 3d. Volume v., comprising the numbers published from January to Jane, 1684, will soon be ready, price 98., including parcels postage, Ss. 6d. Binding Cases for all the Volumes published are to be had, price 2e. each including parcel postage, 2a. 3d. Subscribers' numbers bound (including title, index, and case) for 3fi. C»ch Volume ; including return journey per parcels post, 3a. 6d. Remittances should in every case accompany parcels for binding. TERMS OF SUBSCRIPTION. The terms of Annual Subscription to the weekly numbers of Kitottledgb are as follows :— s- d. To any address in the United Kingdom 15 2 To the Continent, Australia, Xew Zealand, South Africa, &, Canada 17 4 To the United States of America $4.25 or 17 4 To the East Indies, China, ic. (na Brindisi) 19 6 All subscriptions are payable in advance. OFFICE : 74-76, GREAT QUEEN STREET, LONDON, W.C. Aug. 8, 1884.] • KNOWLEDG 103 ]AZiNE OF SCIENCE ^ rPmNUWORDED-EXACTUDESCRIBED LONDON: FRIDAY, AUG. 8, 1884. Contents op No. 145. PAGB The Morality of Happiness. By Thomas F..'ster Ill3 The Sea Horizon. BtR. X. Prorlor HU The Sense of Tasle. By Grant Allen ins TheOri-inot Silk 10.0 Dreams. VI. By Edward Clodd.. 107 The Earth's Shape and Motions ; In- troduction. Bt It. X. Proe'or ... 108 The Elect ro-Magnet. By W. Slingo. 109 The Capture Theory of Comets. By E. A. Proctor , , Ill Mind in Man and Brute. By G. J. Romanes 112 Natural Gas Fuel at Pittsburg 113 PAGB The Tarantula of Southern Cali- fornia. (Illiif.) Ill Attitudes after Death. {lUus.) By C. E. Brown-Sequard -. llj Other Worlds than Ours. By M. de Fontenelie. With Notes by Richard A. Proctor 117 The International Health Exhibi- tion. XI. Ulhit.) 118 Editorial Gossip 121 Our Paradox Column 121 Correspondence 122 Our Mathematical Colujon 123 ' Our Chess Column Vii THE MORALITY OF HAPPINESS. By Thomas Foster. [By an odd coincidence, the editor of Knowledge and I, Five of Clubs and the author of " How to Get Strons," crossed the Atlantic at one and the same time, in the steamship City of Rome. Jlyown voyaiie has caused some delay in the appearance of my closing paper, promised for several weeks since. 1 was unable to complete it, as I had hoped, before leaving England. Buc I believe that the time which I have been able to give to the consideration of that general view of my subject which now alone remains to be pre- sented has not been thrown away. — T. F.] Closing Remarks. IT remains only now that I should consider the general conclusions toward which our discussion of the sub- ject of happiness as a guide to conduct may appear to have led us. Let me note, yet once more, that those have entirely misapprehended the whole drift of this series of papers who imagine, as many still seem to do, that my subject has been the morality of being happv, the propriety of seeking after happiness. The mistake appears so absurd, when the nature of the reasoning I have advanced is considered, that it would seem hardly worth while to correct it, seeing that no one who could fall into such a mistake could (one would imagine) in the least protit by any explanation or correction. Yet the mistake has been made by several who are clearly not devoid of capacity alike to render and to receive a reason. I have therefore felt bound to correct it as far as possible, and, as several letters recently received show that the error is still entertained, I have now to correct it afresh. Let me explain, then, that the object of these papers has been to show what sort of moral law is likely to arise, and what law appears actually to have arisen and to be in progress of formation, when the guide of conduct is the increase of happiness, — individual happi- ness, and the happiness of those around us, with due regard to the proper apportionment of altruistic and egoistic happiness. I have not examined such questions as, What is happiness t What kind of happiness is worthiest 1 and so forth. I have taken, as included in the terra " hapjii- nfss," all the various forms of pleasurable emotion of which the human race is susceptible, while all the various forms of painful emotion to which we are exposed have come naturally into consideration as aU involving greater or less diminution of happiness. With the development of the human race, or of any part of the human race, in one direction or in another (for developmint is multiform), we tind that ideas about pleasure and pain become modified in various ways. And it has been a special part of our suUject to consider how the lower forms of pleasure, those related first to the physical gratification of self, and next those related specially to self, but otherwise of higher type, give place gradually to the higher gratifications arising from altruistic relations. But, apart from such considerations, our whole inquiry has been into the develop- ment of conduct by the natural operation of those laws which influence the development of happiness. In passing I would, however, note that the law of con- duct thus considered is by no means that abstraction which has been called " the happiness of the greater number," according to which each person is to regard himself and to be regarded as one, while the rest, being many, are to be regarded as of very much greater importance. This ab- straction has not and never had any value whatever, as a rule of conduct, either in a man's self or in his relation to others. Even if we can adopt any meaning for the word happit'css as thus used, it will be found that no rational way of apportioning the happiness thus regarded as a sort of common property can be conceived. If the law instead of being an abstraction were real and could be definitely applied, it could result only in this, that each person, being but one, should utterly neglect his individual welfare iu favour of the general happines.=, and, as it can be readily seen that no benefits he might receive from those around him (obeying, we may assume, the same law) could pos- sibly compensate for the direct and immediate effects of this complete self-obnegation, it foUoirs that a community of persons obeying this law would be a community of miser- able beings ; so that obedience to this law for obtaining general happiness would in reality insure universal miserj'. Taking concrete instead ot abstract happiness as the guide of conduct, we recognise far different results. We see that, though there must of necessity be a compromise between egoistic satisfactions and altruistic cares, the com- promise need by no means imply antagonism. Regard for the welfare of others, though in its inception more or less of an effort, becomes more and more spontaneous as social relations develop. After spontaneity has been attained, altruistic actions involve more and more of egoistic satis- faction. Conversely, the care of self, which in the earlier stages of social development appears to involve more or less of disregard for the interests of others, becomes more and more altruistic in its effect as society ad- vances. Thus also we recognise the answer to what at first might seem a difficulty, viz., that with the im- provement of social relations the opportunity for altruistic actiovis might seem likely to steadily diminish. We see that the domain available for altruistic actions changes in position rather than in extent ; nay, that such change of extent as actually accrues is toward increase. In a society where, owing to the steady improvement of the relation between egoistic and altruistic interests, the number of those depending for their happiness or even for their existence on altruistic cares has steadily diminished, the number of those who are the subject ot altruistic emotions will as steadily have increased. Sympathy becomes more widely extended, its development becomes surer and more rapid, as its operation becomes more pleasurable, and a change of this sort cannot but take place as occasions for directly altruistic actions, such as arise out of pain and suffering, become less frequent. With increased spontaneity in altruistic actions, more 104 ♦ KNOWLEDGE ♦ [Aug. 8, 1884. pleasurable feelings in the discharge of altruistic duties, and a wider range for altruistic emotions, will inevitably come such an evolution of conduct as must tend greatly to increase the well-being of the community. The care of self will lie felt as a duty to others ; due care of others will becotue a source of gratification to self. Society will be simply, on an enlarged scale and in a more varied form, sucli a community as might be formed by a number of kindly, vell-iiieauing persons, of good capacity and pleasing manrers, brought together for purposes of travel, research, or plt^asure. In such a community it would be felt that each person's first duty was to take due care of self, first as just to himself, and secondly (yet chiefly) as a duty to the rest of the community. But it would also be felt by e-ch member of such a community that lie must be care- ful of the interests of others, ready to be of use to any other members of the community who required assistance such as he could give individually, or to combine with others where the a>-!iuman ancestors. The third and lowest region of the tongue is the one cognisant of pleasures and pains in immediate sympathy with the stomach. The feelings we experience in this part ■ of our throats can scarcely be properly described as tastes ; they are best characterised, in Professor Bain's well-chosen language, as Kelishcs and Disgusts. When we have begun to chew a piece of wholesome beef-.steak in healthy hunger, we are conscious of a certain pleasurable sensation as it reaches the back of the tongue which induces us to persevere with the action of swallowing, and finally commit it to the digestive apparatus. On the other hand, when we take a dose of codliver oil, we are conscious, at the same stage in the proceedings, of a certain physical repulsion to the act of swallowing it ; something seems to rise up instinctively in the throat which warns us that cod-liver oil is a remarkably difliouli substance to digest and assimilate. The sensations thus experienced are purely premonitory of the eflfect of the food taken upon the stomach. Accord- ingly, they vary much, according to our state of health or appetite. However seasick we may be, ])ungent things are still pungent to u.s, acid thicigs acid, bitter things bitter, and sweet things sweet. But meat, fat, oils, and so forth, produce effects very different from their ordinary results. The tastes discriminated by the lower part of the tongue are all of this character ; and the thiugs which find it most difficult to pass the final examination liere are tainted or putrid meats, very rich or buttery dishes, and other indi- gestible or bilious substances. Thus we may say roughly that the threshold of the mouth warns us against whatever will prove absolutely destructive to the tissues generally ; the central region dis- tinguishes between what is ordinary human food, and what is poisonous or otherwise deleterious when taken internally; and the lower portion of the tongue and thrr at pronounces finally upon the digestibility and fitness for the stomach (in its passing condition) of the food which has success- fully passed the two earlier preliminary examinations. THE ORIGIN OF SILK. IF we put any trust in tradition, says an English journal, there is a legend that Tchin, the eldest son of Japhet, father of the Asiatic race, taught his children the art of ))reparing silk, as well as the arts of painting and sculp- ture. Be this as it may, it is certain that, about 3,000 years before the Christian era, a Chinese book, the " Ghou- Kiug," described silken cords, which were stretched upon a musical instrument invented by the Emperor Fo-HL One of his successors. Chin Nong, reputed inventor of the plough, explained to his contemporaries what beautiful stuff's could be obtained by cultivation of the mulberry tree, and about the year B.C. 2600 an empress, to whom a grateful posterity assigned a place in a celestial constella- tion, perfected the art of unravelling the cocoon and weaving. From that time silk culture had its principal seat near the northern portion of the Yellow River, in the province of Chan-Tong. There was produced silk for the Royal household. Yellow was the chosen colour for the emperor, empress, and prince imperial ; violet for the other wires of the emperor, blue for distinguished officers, red for those less conspicuous, and black for everyone else. In the book of rites, " Li-Ki," the ceremonies performed at the harvest are carefully described. Even the empress did not disdain to gather the leaves of the mulberry with her own dainty fingers, and watched over the rearing of the busy toilers of the cocoon. For a long time this invaluable industry remained the exclusive property of the Chinese empire, but about the third century before the Christian era a military expedition from China bore the results of its civilisation to the startled Occident. Silk became known in Persia and India, and was at last brought to Europe. The soldiers of Crassus, B.C. .56, saw silken standards among the Parthians, and a few years later an immense velarium of silk protected the spectators in the Roman circus from the rays of the sun. From this time the Romans were always provided with the beautiful textures which were the admiration of their legions. Yet silk was still the privileged possession of the rich, and in the time of Aurelian, who flourished in the third century, was worth about forty times its present value. The enormous price, when considered with the fact that there was at that time no commerce between Rome and the Orient, goes far towards explaining the great hoarding of treasure and jewellery which has since that time gone on in India. Aug. 8, 1884.] KNOWLEDGE 107 There is a dispute between tradition and history as to the period when the genuine cocoon was brought from China to Europe. How was the vigilance of Celestials thwarted, since exportation of the silkworm from the Flowery Kingdom was forbidden under the severest penal- ties 1 One accouut states that in a.d. 5.32, two monks sent to Kothan by Justiuian, succeeded in bearing away their booty concealed in a stalk of bamboo. The legend says that once upon a time, when Kothan did not yet possess the precious bombyx, the King of one of the provinces sought and obtaiDed a daughter of the Chinese Emperor in marriage. Before quitting her native land she hid seeds of the mulberry and silkworms' eggs Ln her hair, where it would escape the vigilance of the Customs officers on the frontier. When she reached her new home she planted the seeds of the mulbeiry in order that suitable nourishment might be provided in the leaf for the worms. — The Dyer and Calico Printer. DREAMS: THEIR PLACE IN THE GROWTH OF PRIMITITE BELIEFS By Edward Clodd. VI. TO the savage mind no other explanation of illness is possible than that it is due to the exit of one's own spirit or to the iiitrusiou of a stronger one, whether of re- vengeful man or animal. An old Dacotah, whose son had sore eyes, said that nearly thirty years before, when the latter was a boy, he fastened a pin to a stick and speared a minnow with it, and it was strange that after so long a time the tish should come to seek revenge. When an Indian is attacked by any wild beast, he believes that the avenging Kenaima has transferred his spirit to the animal which seizes him, and if he has even a toothache, of which more presently, then the Kenaima has insinuated himself in the shape of a worm. The tribal chief among the Brazilian natives acts as doctor, and ■when he visits the sick, he asks what animal the patient has offended, and if no cure is effected, the convenient explanation is at hand that the right animal has not been found. At the death of Iron Arms, a noted North Americaa Indian warrior, it was said that he died because the doctor had made a mistake, thinking that a prairie-dog had entered him when it was a mud-hen. The more abnormal and striking phases of disease manifest when a man is writhing under intense agony, as if torn and twisted by some fiendish living thing, or when in delirium he raves and starts, or when thrown down in epilepsy he struggles convulsively, or when he shivers in an ague, or when in more violent forms of madness he seems endowed with superhuman strength ; the various symptoms attending hysteria ; each and all support that theory of spint-influence which sur- vives among advanced races in referring disease to supernatural causes. For the ancient theories of a Divine government under which disease is the expres- sion of the anger of the gods, and medicine the token of their healing mercy ; and the current notions that any epidemic or pestilence is a visitation of God, are identical in character, however improved in feature, with the bar- baric belief illustrated above ; and in the ages when belief in the devil as one walking to and fro upon the earth was rampant, he especially was regarded as bringer of both bane and antidote. " He may," says an old writer, "inflict diseases, which is an effect he may occasion apjilicando activa passivis (by apjjlying actives to passives), and by the same means he may likewise cure .... and not only may he cure diseases laid on by himself, as Wierus observes, but even natural diseases, since he knows the natural causes and the origin of even those better than the physicians can, who are not present when diseases are contracted, and who, bein^ younger than he, must have less experience." In Lancashire folk-lore " casting out the ague " was but another name for " casting out the devil " ; in the Arabic language the words for epilepsy and possession by demons are the same; and in such phrases as a man being " beside himself," " transported," " out cf his mind," or in the convei-se, as when it is said in the parable of the prodigal son, " he came to himse'f "; in the words ecstasy, which means a displacement or removal of the soul, and catalepsy, a seizing of the body by some external power, we have language preserving the primitive ideas of an intruding or departing spirit Such minor actions as gaping and SLcezing confirm the belief. The philosophy of the latter, as Mr. Gill remarks in his '• Myths and Songs of the South Pacific," is that the spirit having gene travelling about, its return to the body is naturally attended with some difficulty and excitement, occasioning a tingling and enlivening sensation all over the body. And the like explanation lies at the root of the mass of customs attendant on snetzing, and of the superstitions generated by it, which extend through the world. Williams tells us that among the Fijians, when any one faints or dies, their spirit, it is said, may sometimes be brought back by calling after it, and occasionally the ludicrous scene is witnessed of a stout man lying at full length and bawling out lustily for the return of his soul. So in China, when a child is lying dangerously ill, its mother wOl go outside into the garden and call its name, in the hope of bringing back the wandering spirit But for all the ills that flesh is heir to — from hiccupping to madness, from toothache to broken limbs — the patient seldom dares to doctor himself ; neither the etiquette of the ordained medicine-man nor the orthodox thera- peutics favour that show of independence. The methods adopted by the faculty vary in detail, but they are ruled by a single assumption. When a Chinaman is dying, and the soul is believed to be already out of the body, a relative holds up his coat on a bamboo stick, and a Taoist priest seeks by incantations to bring back the truant soul so that it may re-enter the sick man. Among the Six Nations the Indians sought to discover the intruder by gathering a quantity of ashes and scattering them in the cabin where the sick person was Ijiug. A similar recipe for tracking demons is given in the Talmud ; but, as more nearly bearing on the Indian practice, a Polish custom mentioned by Grimm^ may be quoted. When the white folk torment a sick man, a friend walks rovmd him carrying a sieveful of ashes on his back, and lets the ashes run out till the floor round the bed is covered with them. The next morning all the lines in the ashes are counted, and the result told to a wise woman, who prescribes accordingly. A favourite mode of treatment is blowing upon or sucking the diseased organ, and deception is no infrequent resort when the sorcerer secretes thorns or fishbones, beetles or worms, in his n.outh, and then pretends that he has ex- tracted them. Cranz says that the Eskimaux old women appear to suck from a swollen leg scraps of leather or a parcel of hair which they have previously crammed into their mouths, and in Australia the same dodge is practised, when the sorcerer makes believe that he has drawn out a piece of bone from the affected part. That toothache is due to a worm, is a belief which exists throughout Europe * " Tent. Mythol.," 1165. 108 • KNOWLEDGE • [Aug. 8, 1884. and A&ia, and from the Orkneys to New Zealand. Shake- speare refers to it in " Much Ado about Nothing," •act iiL, sc. 2 : — Don Pedro. What ! sigh for the toothache ? Leonato. Where is but a humour or a worm. and instances are current of this superstition being acted upon in rural districts, whilst in China the itinerant dentist conceals a worm in the stick which he applies to the aching tooth, and on the stick being gently tapped, the worm wriggles out to the satisfaction of the sufferer. But among barbaric races the treatment is ordinarily the reverse of soothing. Here and there the virtues of some plant have been discovered by accident, and, whilst exalted into a deity in its native home, it has become, like cinchona, a priceless boon to the fever-stricken all over the world ; but, speaking broadly, the medicine-man is no Melampus, win- ning the secret of their healing balm from herb and tree. Nor has he much faith in magic or charm compared to his faith in noise, in incantations, with their accompanying hideous grimace.s and gestures, and their deafening yells with clang of instrument to drown the sufferer's groans -and chase away the demon. Not unfrequently, when the patient is kept without food so as to starve out the in- dwelling enemy, or when the body is pommelled and squeezed to force him out, the remedy helps the disease ! An illustration or two from a great mass at Gommand must sufhce. Among the Mapuches the sorcerer adopts the canonical howls and grimaces. Making himself as horrible-looking as he can, he begins beating a drum and working himself into a frenzy until he falls to the ground with his breast working con- vulsively. As soon as he falls, a number of young men outside the hut, who are there to help him in frightening the disease-bringing spirit out of the patient, add their defiant yells, and dash at full speed, with lighted torche.s, against the hut. If this does not succeed, and the patient dies, the result is attributed to witchcraft. When a Pawnee chief had some ribs and an arm broken, the medicine-men danced round him, and raised their voices from murmurous chants to howls, accompanying the music (?) by blows upon the wounded man's breast to banish the bad spirit. In olden time this rough-and-tumble busiuess of blows, to which immersion was added, was applied to lunatics in these islands. And, in fact, until some local paper narrates a current superstition, we seldom awaken to the fact how widely the theological explanation of diseases and the em- pirical choice of remedies still obtains, each being survivals of barbaric theory and practice. The savage who has more faith, as a curative, in plants that grow on burial-places, and the civilised, who ascribes special healing power to turf and dew from a saint's grave, differ no whit in kind ; and so ingrained was the medicinal belief in virtue inhering in fragments of the dead, that not even the satire of "Reynard the Fox," telling how the wolf was cured of his earache, and the hare of his fever, the moment that they lay down on the grave of the martyred hen, could give quietus to the notion that grated skulls and sacramental shillings were specifics for the heal- ag of the faithful. This reference to like practices reminds us how belief in the action of invisible agencies has passed into the practice of confession among advanced races outside Christendom, as in Mexico and Peru. The Eoman datholio priests were not less astonished at finding this in vogue on their arrival in South America than the good Father Hue when, on reaching Tibet, he found shaven monks wearing rosaries, worshipping relics, using holy water, and a grand Lama decked in mitre, cope, and cross.* But, as the Italian proverb has it, the world is one country and " we have all one human heart," so that the confessional has the like explanation in east as in west. If the disease be the work of an offended deity or of an avenging spirit, let the wrongdoer admit his fault, and trust to him who is credited with influence with the un- seen to exorcise the intruder. THE EARTH'S SHAPE AXD MOTION'S. t By Eichakd A. Proctor. INTRODUCTION. IN many works of astronomy the subject of the earth's figure and motions is dealt with at greater or less length ; the general principles on which modern views are founded are exhibited witli sufficient clearness ; and a number of facts quite sufficient to establish the justice of modern theories are quoted in illustration. But it has always seemed to me that the way in which such matters are commonly presented, is open to objection. Either from a desire to simplify the subject, or for some other reasons, the facts are stated in a general way, which is in reality much more perplexing to the beginner than an exact statement would be, befides being open to cavil and olijection. The full force of the observational or experi- mental evidence on which modem views have been founded, is lost to the student, when the results are stated without a careful reference to quantity and measure. The impression is too commonly left, that those inexact and unsatisfactory results are in reality all that astronomers have been able to gather ; and when it is seen that such results admit of being explained in other ways, doubts naturally spring up as to the exactness of modern astronomy. This would be less important, were it not that there is a class of persons very ready to [irofit by this state of things. Knowing perfectly well that the world is always more ready for novelty, than to hear the details of real scientific progress, these persons invent hypotheses of greater or less ingenuity, which appear to be consistent enough with the relations described in books on astronomy. These hypo- theses they further recommend to the public notice by garbled e.xtracts from the works of known authors, or by apocryphal experiments. Secure of a large audience for their absurdities, they little regard the contempt which all well-informed persons bestow on them. They invite con- trover.sy, confident that no student of science, who considers his own reputation, will enter the lists with them, and safe also (even if such an improbable event should occur) in the certainty that by a few verbal evasions they will be able to avoid the appearance of defeat. There is also another class of persons equally anxious to promulgate new theories, but not absolutely dishonest. Among the thousand who, having read the ordinary popular works on astronomy, remain unconscious of the exactness of modern science, there are necessarily some who mistake their want of apprehension for exceptional ability. Such persons, especially if they are troubled by the cacoetJies scribfndi, promulgate new theories with a sur- prising fecundity. Scarcely a month passes that a work involving some new absurdities does not pass through the press. And these books find purchasers who are at least * " Toil^ autant de rapportsque les Bonddhistes ont avec nons," adds the traveller, for hinting at which analogies between Bnddhists and Catholics the Pope put his book on the Index. t The papers which follow are revised versions of a series which appeared seventeen years since in the English Mechanic. Aug. 8, 1884.] ♦ KNOWLEDGE ♦ 109 as likely to adopt the new views as to retain their confidence in the ruodern system of astronomy. I would not have it undeistood that the present series of papers is in any way intended as an answer to the para- doxists — whether of the honest or of the dishonest school. To enter into controversy with these writers would be not only a foolish, but a wrong thing to do. It would imply that modern astronomy, and — which is more important — the professoi-a of modern astronomy, require to be defended. The task would also be necessarily a vain one, sinee the honest paradoxist cannot, and the dishonest paradoxist will not see the futility of their ai-guments. Nor does either class, indeed, deserve to be answered, since even the honest paradoxist — though otherwise to be commiserated — yet merits condemnation for professing to teach matters which he has not mastered, and so leading others astray. It is for the benefit of those who really wish to know something of the grounds on which the modern system of astronomy rests, that I pen these papers. I wish to indi- cate the way in which the various parts of the evidence dovetail into each other, and to show how observed facts are accounted for, not merely in a general way, but in measure and quantity — the only true test of a theory. Lastly, I may find occasion in passing to notice some of those absurd hypotheses which now, as at any time tince Newton's day, find supporters and believei's. A large part of the evidence I shall present to the reader is such as he can himself abundantly verify ; but necessarily, a very large part remains which has to be taken on trust. I cannot call upon readers to take sail for the southern hemisphere and make such and such measurements or ob- servations. I cannot ask them to devote a whole life to the study of practical astronomy, that they may be able to make those exact and delicate instrumental observations on which modern astronomy in large part depends. Nor can I insist that every one of my readers shall master the higher branches of mathematics so thoroughly that, if need were, he could follow Adams and Leverrier through all the intricate calculations by which they have extended our knowledge of the structure of the universe. On many points, therefore, I shall have to confine myself to giving as clear aud exact a statement of what is or of what has been done as I can, without being able to give evidence which can be tested, or of showing in all cases how such and such facts have been determined. In all such cases I shall have to claim the reader's trust, to ask hiiu to believe in the exactness and honesty of modern astronomical work. Now so much has been heard from the paradoxists of the cliquism of astronomers, of their determination to uphold a false system at all costs, and of other such matters, that many have been led (absurd as it may seem), to feel doubts as to the bare honesty of the professors of modern astronomy. To all such I would say, judge astronomers in this respect as you would judge other men if you had occa- sion to question their honesty of purpose. Ask whether it is for the interest of astronomers to uphold a false system. Consider whether it is in accordance with what we know of human nature, that they should combine to laud the names of a Newton, a Copernicus, or a Kepler, in defiance of truth and justice. On the first point it is easy to find an answer. The whole system of modern astronomy depends for support on the exactness with which it records or anticipates the celestial movements. Certain processes are applied for this purpose, which satisfactorily accomplish all that is rei:|uired. These processes might be continued without change, though the whole system on which they were founded should be abandoned. Thus the si.gle end and aim of practical astronomy, that purpose for which our observatories are founded, and our astronomical stafi" salaried, could be ac- complished as well as at present, though Newton wert^ pro- claimed a charlatan, and Copernicus a cheat. So far then ■we see nothing to lead to the suppression of the truth, if the truth really required the overthrow of modern theories. On the second point we can found a yet stronger claini for the confidence of our readers in the work of astronomers. Newton and Copernicus are long since dead. They can extend no patronage to the astronomer in return for the respect and admiration with which he speaks of them. To suppose that Aii-y, or the Herschels, Adams, Leverrier, or Hind, would praise Newton for a theory which they knew to be false, is not only to give them very little credit for honesty, it is to assert that they are blind to their own interest. If an unknown man, indeed, were to assert that Newton and Kepler were mistaken in their theories, we should, of course, pay no attention. But if Mr. Hind, for example, were to announce such a belief, he would be heard with respectful attention, .ind if (to conceive the incon- ceivable) he could establish the justice of his view, he would immediately rank high above the highest in the long list of eminent astronomers. So of any of the others 1 have named. On this second ground, therefore — that it is not in accordance with what is known of human nature for any man, still less for a set of men, to praise another (long since dead) for false theories, when he himself might acquire like or higher praise by overthrowing them — I con- fidently claim from my readers the acceptance of the results of all those observations, measurements, or experi- ments which have been made by modern astronomers. The method I propose to adopt in the forthcoming pages is the same that I employed in the first chapter of my treatise on Saturn, and is in great part new. 1 shall show how a person wholly unacquainted with modern astronomy, might have the true relations of the earth exhibited to him in a series of simple observations. The particular order I shall select for presenting those relations might be departed from, since the subject is one which admits of a considerable variety of treatment. Other methods have, indeed, suggested themselves to me, but I believe that, on the whole, the one I have adopted is that best calculated to present the subject in a clear and satisfactory manner^ within such limits as are hei-e available. {To he continued.) THE ELECTRO-MAGNET. Bt W. Slingo. (Continued from p. 69.) I All anxious to keep clear of formula as far as I can^ but at the same time to impart as much information as possible concerning the electro-magnet and the principles governing its structure. The two very simple equations at the end of the previous article may facilitate matters very materially. It was shown that with a coil of the relatively thick wire a current was produced, having a a strength of 1 -3 amperes, and that when the diameter of the wire was reduced to one half, so as to get twice the number of turns, the current strength was reduced to -i ampere, or less than one-third of that attainable with the thicker wire. One of the laws of electro-magnetism is that the strength of an electro-magnet is proportional to the strength of the current. This is only true when the number of tnrns is the same, because each time the current circulates round the iron core it exerts its electro- magnetic effect. This law has therefore to be taken in 110 ♦ KNOWLEDGE ♦ [Auo. 8, 1884. conjunction with another, declaring that " The strength of an electro magnet is proportional to the number of turns of •wire." Regarding these two laws together, it is clear tliat the thick wire coil has the greater effect, because, while there are twice the number of turns of the thin as com- pared with the thick wire, there may be said to be three times the current circulating through the thick as compai'ed with the thin wire. Were the two currents made equal by modifying the battery power, then the thin wire would be twice as effective as the other. On the other hand, if while the conditions of the thin coil remained constant, the thick wire could by any means be made to encircle the core twice as often (the current being kept constant) then tlie threefold curreut circu- lating in the thick wire would exert three times the magnetising itifluence upon the core. Even these laws, however, are not always applicable, because there is a limit to which iron or any other sub- stance is capable of being magnetised, and the fact of there being such a limit implies that the above laws may onlj' V>e regarded as applicalile when the effect to be produced is considerably below this limit, which is called the " saturation point." It was just now stated the magnetic strength varies in proportion to the number of turns. Supposing that the iron core were covered, and that no room could be found for another turn, how arc we to increase that number 1 It might be done by coiling a wire over tlie previously wound coil, but what about the direction 1 It is evident that if we send a current round the core through a left-handed helix (as in Fig. 1), so as to make the end N a north-pole, and then .send a current through an outer coil in such a manner as would induce a south-pole at N.then no polarity will be manifested unless the inducing force of one helix exceeds that of the other, in which case tlie magnetism induced will be a measure of the difierence between these forces. It is, however, very easy to calculate the inductive effect that would be produced by any particulai cod of wire. Suppose, for example, that we are dealing with the arrange- ment depicted in Fig. 1, and that we wind a second left- handed helix over the core, then join a wire from the S end of the inner coil to the N end of the outer one, so that the current is made to travel in the direction indicated by the arrows through each coil in succession. Neglecting the .slight increase in the length of wire involved in wind- ing one coil over another, we shall get an external circuit having twice the resistance of the iuner coil or (with the two cells). _E 4 R + r ~ 2-f 2 - ^ The current is thus 1 ampere as compared with 1 3, but as it passes twice as often round the core, it may be said to have an inducing power of 2 as compared with l.'; exerted by the single coil. Here, then, au advantage is clearly gained. Supposing, however, that instead of connecting the two coils in series, we join them in parallel circuit — that is, by connecting the two N ends together, and likewi.se the two S ends. Then the current will divide at N, and, the resistance of the coils being identical, the current will divide equally, to re-unite at S. But the joittt resistance of two equal wires is only half that of one of them, or their conductivity (the reciprocal of resistance) will be doubled. This principle has been more than once enlarged upon, so it need not further take up time here. The simple equa- tion becomes _i =16. i + 2 1 6 amperes do not, however, go through each coil, but the current halving itself at N becomes only IS in each. Mani- festly, then, a curreut of 8 ampere through a certain number of turns can only have the same eflect as a current of ro ampijres through half that number of turns. In other words, the eflect jiroduced is the same as would result from a single coil having the same number of turns as before, but with twice the conductivity or half the resistance. This could not be obtained with the same kind of wire, becau.se to have half the conductivity it would require twice the weight of metal. Of course, it would be possible to gain this end by using rectangular wire whose thickness in one direction is equal to the diameter of the original round wire. But even then the trouble involved would not be recompensed by the gain in inducing power, which, as pointed out, is only 16 as compared with lo. Under the circumstances, then, the best eflect is jiroduced when the current is made to traverse the coils successively. But, on the other hand, to wind a number of individual layers, and then to connect them by longitudinal lengths of wire is out of the question, more especially as the desired effect may be more easily jiroduced without such an arrangement. Fige. 1 and 2. By examining Figs. 1 and 2, the method to be employed may be readily made clear. Let us start with a layer wound, as shown in Fig. 1 — that is as a left-handed helix — and let the current travel from left to right, or from N. to S. Now it has been stated (and Fig. 2 will illustrate it) that a current passing through a right-handed helix induced a north at its exit. Suppose, then, that instead of travelling from left to right, the current pursues the opposite direc- tion, or from right to left. Then the end marked N becomes a south pole, and the end marked S a north pole. The effect thus produced is the same as that resulting from left to right through a left-handed helix. If a right-handed helix be wound over a leftrhanded one, and the adjacent extremities, say on the right-hand side, be connected to- gether, then the current will jiass from left to right through a lef1>handed, and from right to left through a right-handed, helix, when the inducing effect of each coil will harmonise, and a north pole will be produced on the left-hand side, and a south pole on the other (as in Fig. 1). It is scarcely necessary to say that the resistance of a wire is not affected by the direction of winding, consequently the current flowing will be ^=1 •2 + 2 which (as may be gathered from what has been said above) will produce a magnetising force of 2 as compared with 1 '3 resulting from either of the coils used singly. If the student takes a piece of wire or .string in his hand and winds it round a rod so as to make a left handed helix, and when he reaches the end of the rod continue the winding back to the other end without bending the wire back on itself, he will find that the second layer becomes a right- handed helix. If, furthermore, on finishing the second layer, he winds back again for a third layer, he will find that this is a left-handed helix. So, continuously winding, he gene- rates left and right-handed helices alternately. Every Aug. 8, 188L] o KNOWLEDGE 111 layer, therefore, supposing a current to traverse such series of coils, tends to produce a north pole at one end and a south pole at the other. This is the principle involved in the construction of electro magnets. Before dilating upon the size and length of wire for any particular coil, let us turn our attention to the practical details of construction. It may, in the first place, be stated that, generally speaking, the best effects are produced when the length of the core is six times its diameter. Its .=uiface should he as even as possible, not absolutely smooth, but free from marked irregularities. If such irregularities are present, they are likely to cut through or wear away the cotton or silk, whichever it may be, that is used for insu- lating the wire. If, again, the current is one of excep- tionally high electromotive force, there will Le a consider- able risk of its passing from the wire to the core, rejoining the coil at some other point. It is almost superfluous to say that when it behaves in this way, the coil might as well be absent for all the good it is capable of doing. Where any of these dangers are present the iron should either he coated with a layer of shellac varnish (made by dissolving good shellac in methylated spirit), or closely covered with paper which has been saturated with melted paraffin wax. Either of these cour-ses will, in the great majority of cases, be sutlicient to prevent the current taking a short path through the iron. The wire should be well insulated with cotton or silk, and wound as closely and regularly a.s possible. When the first layer is finished it should, more particularly if the wire is cotton covered, and currents of high EM.F. are to be used, be immersed in a bath of melted paraffin wax, and insulation is further assured by covering the layer o£ wire with a piece of paraffined paper. This will not want tying on or securing by extraneous means, but may be quite as effectually fixed by winding it round tightly, and then with the aid of a hot poker, or other piece of iron, heating one edge of the paper over the other. The hot iron melts the wax, which, on cooling, holds the paper firmly. The second layer may then be applied and treated in identically the same manner as the first. Layer should then succeed layer until their entire thickness equals the diameter of the core ; or, in other words, until the diameter of the coil measures three times that of the core. The length of the coil will then be twice its diameter. It will be apparent that, to get the greatest possible number of layers on, so as to come within these dimensions, the space occupied by the insulating material must be as small as is practicable. An electro magnet is then produced, care being taken, obviously, to leave free sufficient wire at the ends of the coils for purposes of •connection. Electro-magnets are very powerful, much more so than ordinary permanent steel-magnets, and are capable of producing marvellous effects. The shape of the magnet may be just whatever the experimentalist pleases, remem- bering, of course, that the simpler the shape the more easily will it be wound. The effects produced by magnets ■oi equal length wnth equal quantities of wire are not by any means identical. Even in simple straight bar-magnets, a number of different effects may be produced, and Pro- Jessors Ayrton and Perry have published particulars of very interesting experiments on this point, with which, however, as the allotted space is filled, we must deal a fortnight hence. (To he continued.) It is a. sad commentary on the danger of railroading to limbs, to say nothing of the disaster to life, that the Toledo Railroader, the xjrgan of the railway employes, contains the advertisements of nine different manufacturers of artificial limbs. - • THE CAPTURE THEORY OF COMETS.* Bv Ricn.vBD A. Proctor, "XTTE start from the conception that all comets originally * V entered our solar system from without. They came, says Heis, Schiaparelli, and others, who have advanced the Capture Theory, fiom out of interstellar space. Now, it is no valid objection to this view that it gives us no idea how cometary matter came to exist in interstellar space, for in all inquiries into the past condition of the celestial bodies we must always come short of their actual origin. Thus, in considering the past of our solar system we may start from a chaotic vaporous state, or from a past condition in the form of cosmical dust, or from a condition in which the vaporous and the dust-like forms are combined ; but if we are asked whence came the vapour or the cosmic dust we are obliged to admit that we cannot tell. If, hereafter, we should be able to say that it, carae from such and such changes io a quantity of various forms of matter, which we may represent by X, Y, and Z, we should still be unable to say how X, Y, and Z came into existence. So that I make no serious exceptiou against the supposed origin of comets on the ground that it really leaves very much to be explained. Interstellar space is a convenient place to which to assign the origin of bodies so mysterious as comets. Cela exprime bMucoup de c/wses. Almost anything might happen in regions of which we know so little, or, rather, of which we know absolutely nothing. Yet it may be worth while to remark that, on the whole, the interstellar regions are less likely to be the regions whence comets originally came to visit suns and sun systems, than to be regions whither comets strayed after leaving originally the neighbourhood of solar systems. The most probable idea about the interstellar spaces is that they are the most vacuous regions within the range of the sidereal .system. The mere circumstance thit comets came from out of them affords no belter reason for regard- ing them as the original home of comets, than tlie circum- stance that comets pass from the solar system into these interstellar spaces affords for rejecting that assumption. There is, in fact, simply no reason whatever for imagining that the place where comets came into existence is the vast unknown region around the solar system which we call interstellar space. Most comets come to us from thence ; as many comets are travelling into that unknown region as are coming out of it. To form an o|)iniou about the origin of comets from no better evidence than their last journey (out of millions, very likely) can afford, woidi be as absurd as for a day-fly to reason that the river flowing past the home of his race came out of the sky because a few drops of rain came thence. Suppose, however, we admit that in interplanetary space there have been in the past, and still exist, such flights of meteoric matter as the theory we are considering assumes. Let us grant them, also, such motion as may save them from what otherwise would inevit>ibly be their fate, viz., a process of direct indrawiiig towards the nearest sun, and consequently destruction (with mischief probably to his orb), after a period of time which must be regarded as utterly insignificant compared with the time intervals measuring the ditration of a solar system. It follows, then, that each flight of meteors would in the long run draw near some sun, without, however, rushing directly upon him ; and sweeping round his <;l frim-i ground. The process of organic and of mental evolution has been assumed to be continuous throughout the whole region of life and of mind, with the one exception of the mind of man. On grounds of a very large analogy, therefore, we should deem it antecedently improbable that the process of evolution, elsewhere so uniform and ubiquitous, should be interrupted at its terminal phase ; and I think that, looking to the very large extent of the analogy, this antecedent presumption is really so considerable that it could only be fairly counterbalanced by some very cogent and unmis- takable facts, showing a ditference between animal and human psychology so distinctive as to render it in the nature of the case virtually impossible that one could ever have graduated into the other. This I posit as the first consideration. Next, still restricting ourselves to the <> priori aspect of the matter, it is unquestionable that human psychology in the case of every individual human being presents to actual observation a process of gradual development, or evolution, extending from infancy to manhood ; and that in this pro cess, which begins at a zero level of mental life and may culminate in genius, there is nowhere and never observable a sudden leap of progress, such as the passage of one order of psychical being into another distinct in kind might reasonably be expected to show. Therefore, it is a matter of observable fact that, whether or not human intelligence differs from animal in kind, it certainly admits of gradual development from a zero level ; and to this we must add that, so long as it is passing through the lower phases of that development, it assuredly ascends through a scale of mental faculties which are pari passu identical with those that are permanently presented by the psychological species of the animal kingdom. These facts, which I present as a second consideration, tend still further, and I think most strongly, to increase the force of the antecedent presumption against the process of evolution having been discontinuous in the region of mind. Again, it is likewise a matter of actual observation, that in the history of our race, as recorded in documents, tra- ditions, antiquarian remains, and flint implements, the intelligence of the race has been subject to a steady process of gradual development — a general fact which admits of any amount of special corroboration by comparing the psychology of existing savages, where the process of evolu- tion in the past has not been so rapid or has in part been arrested, with that of civilised man. This is the last consJderation that I shall adduce of the cl priori kind, and its force consists in the fact of its proving that if the process of mental evolution was interrupted between the anthropoid apes and primitive man, it must again have recommenced with primitive man, and since then have continued as uninterruptedly in the human species as it previously did in the animal species. This, to say the least, upon the face of the indisputable facts, or from a merely antecedent point of view, appears to me a highly improbable supposition. At all events, it certainly is not the kind of supposition which men of science are disposed to regard with favour elsewhere : for a long and arduous experience has taught men of science that the most helpful kind of supposition which they can bring with them into their investigations of nature is that kind of supposition which recognizes in nature the principle of continuity. Taking, then, all these <> priori considerations together, they must, in my opinion, be fairly held to make out a very strong prima facie case in favour of the view that there has been no interruption of the developmental process in the curse of psychological history, but that the mind of man, like the mind of animals — and, indeed, like everything else in organic nature — has been evolved. For these con- siderations show, not only that on analogical grounds any SMch interruption must be held as in itself improbable ; but, also, that the human mind unquestionably admits of having been slowly evolved from the zero level, seeing that in every individual case, and during many past millenniums in the history of our species, the human mind actually does and has undergone the process in question. In order to overthrow so immense a presumption as is thus erected on a priori grounds, the psychologist must fairly be called upon to supply some very powerful con- siderations of an a posteriori kind, tending to show that there is something in the constitution of the human mind which renders it impossible, or, at all events, exceedingly difficult, to imagine that it can have a genetic relation to mind of lower orders. NATURAL GAS FUEL AT PITTSBUEG. AT the recent meeting of the American Society of Me- chanical Engineers at Pittsburg, the report of the committee appointed to investigate the whole subject of natural gas was made, and many interesting particulars, we read, were given. Though Pittsburg is within reach of three or four prolific localities, and gas has been used for many years, it is but recently that any organised eflbrt has been made to use it on a large scale. Already there are 1-30 companies charteredin the State, representing over -2,000,000 dols. ,; and gas is brought from eight to twenty-five miles for use in the city. Five-inch mains are being followed by 8-inch, new wells are being bored, and the time when Pittsburg shall become a smokeless city may not be far distant. Though the gas is used under a pressure of a few ounces, the pressures at the wells run from 50 to 12-5 pounds; this is due to the friction in the mains, five pounds being allowed for each mile. If the flow be shut olT the pressure runs up much higher, and great difficulty has been ex- perienced in making tight joints ; cast iron is too porous, and ordinary pipe-threads do not fit well enough. A number of new coupling devices were exhibited, in some of which a lead packing was used. No allowance for expan- sion need be made, as the gas maintains an even tempera- ture of about 45- Fah. \Yhen gas is allowed to burn freely at the mouth of a well, the cold produced by the expansion is such that ice has been projected through the flames. The gas is used in all kinds of furnaces for making steam iron, glass, &c. ; and electric light carbons, and the finest 114 • KNOWLEDGE ♦ [Aug. 8, 1884. lampblack for | rinting inks is made from it ; but it is used witli suicidal wastefulness, which causes anxiety, as many wells give out in le.-'S than five years. The report looks to its economic and safe control. For household use, it might otherwise be dangerous, and such usie has com- menced, though no practicable method of deodorising it has been found. Being composed largely (9G per cent.) of marsh gas, its value as a heating agent is high, and its density is about half that of air. One pound (23.5 culnc feet) of g-is has a theoretical evaporating ))Ower of 241b. of water, 20 lb. having been actually evaporated. The best method of burning it is not generally known ; experiments with injector burners show that they do not suck in suffi- cient air for complete combustion, and the best results have been from numerous jets in contact with the whole heating surface of the boiler. Tlie value of the gas, as compared by evaporation tests with coal at §1.40 per ton, is only Scents per thousand feet (which suggests tliat even our ordinary gas companies make profits), but its use is im- mensely more convenient ; no stacks are needed, and tlie furnace reduces to a simple nonconducting chamber. The gas has just been turned on to the city waterworks. On the first day's excursion numerous furnaces were seen running with gas blown in through rough, J. in. nozzles ; and two or three lines of 5-iu. pipe lay on the surface of the railway embankment. A gas well has lately been opened within the city limits, at a depth of 1,G00 feet, on the property of Mr. Westinahouse. THE TAEANTULA OF SOUTHERN CALIFORNIA. UGLY, vicious, energetic, and to a certain degree poisonous, are the spiders that infest the southern part of California, and yet when closely studied they pre- sent many jieculiar characteristics, both in regard to their structure and habits. Among the most valued trophies tourists carry away with them from the coast are neat cards adorned with these animals, and a case containing the nest so arranged as to show its wonderful trap-door and the delicate lining of the interior. The adobe ranches are full of these strange little hahitations, and some of the .sunny valleys among the foot hills are literally strewn with the small tunnel.", capped with the almost invisible door. Our engraving shows the tarantula (Mi/gale hentzii) as he is about to enter his abode, both being full size. The general appearance of the tarantula is very clearly shown in the engraving. The legs are larger, and are not furnished with so long and dense a growth of hair as are the specimens found in other sections of the south-western States. The back is covered very thickly with extremely tine short hair ; the back and the outer joints of the legs are of a liiiht brown colour, the remainder being of a deeper shade. The forward part of the head is divided, and each division terminates in a sharp, downwardly curved, and jt-t black horn or hook. The tarantula pi>unces upon his prey, and thrusting in the hooks most securely holds his victim. It is seldom met in the daytime, preferring to seek its food during the n ght, returning to its nest in the early morning. Although pugnacious when cornernd, he will not seek a tight, and is more anxious to escape than the stranger whom he chances to meet. This tarantula is justly celebrated for the architectural skill he di-ptays and for the luxurious comfort of his dwelling Having selected a suitable site, he digs a hole varying from four to eighteen inches in depth, and just large enough around to admit him easily, although it in puzzling to conceive how he ever gets his long, ungainlj', and many-jointed legs comfortably disposed in so small a space. The walls are carefully smoothed, and are completely covered with an exceedingly fine faVjric of his own manu- facture. The top of this tunnel is slightly tiared, and in this widened part is fitted the door, which is hinged at one side so that it may be easily lifted. The inside of the door is finely finished, and covered with a web similar to that on the side. The tarantula knows that this door is not heavy enough to ensure a light fit when it is dropped, so he makes a small handle near tlie centre of the under side by which he pulls the door closely down, thereby insuring a joint that most efiectually excludes all dampness from his abode. The handle is a strong web, the two ends of which are attached to the door at points about one-sixteeuth of an inch apart. The outside of the door is placed about at the level of the ground, and is so nearly the eame colour as the surrounding soil that it can be discovered only after the most careful search. The joint of the door is so well made and the colours are so nearly alike that it is almost impossible to ascertain upon which side the hinge is placed, except by raising the door. The framing of the door seems to be a coarse, stronir web, which is extended at one side to form the hinge, and which is bonded with earth to give it the requisite stiffness. The hinge is about three eighths of an inch wide, and acts as a spring to shut the door immediately alter the owner's exit. For the tarantula and nest from which our engraving was made, we are indebted to the courtesy of Mr. H. J. Finger, of Santa Barbara, Cal. — Scient'Jic American. Remedy for Toothache. — Melt two parts of spermaceti or war and dissolve in it two parts of chloral hydrate and one part of carbolic acid. Dip pieces of cotton into the mixture and let it cool. For use, detach a small quantity, soften it with a gentle heat, and press It into the hollow tooth. — Rundscli. f. Pharm, Aug. 8, 1884.] ♦ KNOWLEDGE ♦ 115 ATTITUDES AFTER DEATH. By C. E. Bkown-S^quard.* VMONG the phenomena sometimes noticed at the hour of death there is one that offers a peculiar interest, and which, up to recent times, has remained a mystery. This phenomenon appears especially, but not exclusively, after a sudden death due either to wounds received upon the field of battle or elsewhere, or to other causes, but almost always when there has been an intense excitement, and often also when great bodily fatigue has preceded the last moment of life. The principal feature ot this curiotis fact is the persistence after death of the expression of the face or of certain attitudes of the limbs or body, or of both. The object of this article is to answer this question, and to show that the cause or agency to be discovered is not the suddeu appearance of that state of muscular ttiffness known by the name of rigor mords or cadaveric rigidi/i/, but that such agency is found in a peculiar action of the nervous centres that manifests itself a little before or at the instant of death. One of the most striking examples of the strange fact that I am about to study was observed by Dr. Rossbach, of Wurzburg, upon the battlefield o Beaumont,, near Sedan, in 1870. He found the corpse of a soldier half-sitting, half reclining, upon the ground, and delicately holding a tin cup between his thumb and forefinger, and directing it toward a mouth that was wanting. The poor man had, while in this position, been killed by a cannon- ball that took off his head and all of his face except the Such persistence exhibits itself clearly in certain cases ; for example, wlien, despite the sudden cessation of life, a limb that is raised does not drop, or when the body of a man standing, or seated on horseback, does not fall over. In order to clearly understand the terms of the problem to be solved in reference to this [jhenomenon, it is abso- lutely necessary to know (1) that our attitudes and facial expression depend upon a contraction of our muscles due to an influence of the nervous centres, and (2) that such influence necessarily cea-ing at the instant of death, a re- laxation must also necessarily occur in all the muscles that were contracted, unless some other agency at once replaces that which has disappeared and causes the same physical state to persist that formerly existed therein. The question, then, is this : What is the agency that, as soon as the faculty of volition vanishes, takes the place of the latter, or at least produces in the muscles an organic state that prevents all relaxation 1 * La Nature, lower jaw. The body and arms at the instant of death hac? suddenly taken on a rigidity that caused them to after- ward remain in the position that they were in when the head was removeroper point was reached, when it remained balanced perfectly, so that light could be plainly seen the entire length of the straightedge between the two surfaces, except where the hair separated them at the middle of their length. — Sciejilific American. Feom the annual report of the Metropolitan Board of Works for 1883 it appears that the staff of the London Fire Brigade consists of 670 men. The number of firemen employed on the several watches kept up throughout the metropolis is at present 108 by day, and 253 by night, making a total of 361 in every 24 hours ; the remaining men are available for general work at fires. The number of calls for fires, or supposed fires, received during the year was 2,630. Of these 337 were false alarms, 149 proved to be only chimney alarms, and 2,144 were calls for lircs, of which 184 resulted in serious damage, and 1,96U in slight damage. The fires of 1883, compared with those of 1882, show an increase of 218; and, compared with the average of the last ten years, an increase of 446. Use of Disinfectants in Paris. — Experiments in the disinfecting of rooms have been carried on in a Paris hospital, and many have witnessed the experiments conducted by Drs. Pasteur and Dujardin- Beanmetz. At present two systems are under discussion — the use of the liquid sulphurous anhydride and the simple burning of sul- phur. At first the sulphur would not bum, and the acid, though it told on the litmus test-papers, did not kill the microbes which M. Pasteur had left in the room. Now, however, by pouring a little alcohol over the sulphur, it has been made to burn very successfully, and by using a larger quantity of the disinfectant, whether in a liquid or a solid state, the microbes were killed. Both the rooms measured 98 cubic metres, and 2 kilos, of snlphur had to be burnt before the living organisms left in the room were destroyed. This is about the same amount which long experience in England has proved to be necessary. " Let Knowledge grow from more to more." — Alfbed Tennyson. Only a small proportion of Letters received can possibly he in* serted. Correspondents mvst not le offended, there/ore, should their letters not appear. All Editorial communications should he addressed to the Editor of Knowledge; all Business communications to t?ie Publishers, at the Office, 74, Oreat Queen-street, W.C. If this is not attended to DELAYS arise FOR WHICH THE EDITOR IS NOT RESPONSIBLE. All Remittances, Cheques, and Post Office Orders should he made payable to Messes. Wyman & Sons. The Editor is not responsible for the opinions of correspondents. No COMMUNICATIONS ARE ANSWERED BY POST, EYSN TBOUGB BTAHFU) AND DIRECTED ENVELOPE BE ENCLOSED. VENUS IN A THKEE-INCH TELESCOPE. [1356] — I should like to ask readers of mj- paper on p. 92, to float a pale wash of Indian ink over the inner (the upright or right- hand) edge of Venus as shown in the woodcut (Fig. 1.) on that page, so as to cause it to melt, as it were, into the surrounding sky. The engraver has removed the shading from it, and erroneously left it too sharp and bright. A Fellow of the Koyal Astronomical Society. MIND AND BK.UN. , [1357] — Your very fair critique on Biichner's " Force and Matter" contains one remark on which you ■will, perhaps, permit me to say a word — viz., that it is inconceivable " that thought, &c., i^' motion in matter." To me this seems to follow clearly ; for if it is proved that no motion of brain-matter, no thought, is a truth — and Haeckel, Hurohke, Vogt, and other eminent scientists clearly say BO — it appears to me very conceivable and reasonable to say that thought is a mode of motion of the molecules of the brain. The more perfect the brain the more complicated these move- ments, the deeper the thoughts, seems to follow as a matter of logic. From the simple movements of attraction and repulsion, the loves and hates of matter, it is conceivable to me to trace the gradual development of thought movements pari x-assu with the physical development of the human brain in course of evolution through immense periods. F. W. H. [I may be as obtuse as F.W. H. appears to consider that the Reviewer of Biichner's work is, but I confess that I fail to see that because (as is indubitable) no thought occurs — or can occur — without motion of brain matter — ergo — such motion is itself thought. No tune was, or conceivably ever could be, 'played upon an organ without the movement of the keys, bellows, &c., but it would appear an old mode of reasoning to predicate that such movement was the tune itself. — Ed.] FLORAL PARASITISM. [1358] — During the past spring I have had a fine specimen of Cjrobanche minor make its appearance in a flower-pot containing a double pink geranium, and placed at a window in a sitting-room. When It had finished flowering I examined the root. It had firmly engrafted itself on the root of its host, which had made but little growth, and no recent roots at all. Is it not unusual for orolanche to establish itself on such a plant as a geranium? Wm. H. Allen. [The orobanchacecB are all parasitical on the roots of plants ; bat they mostly attach themselves to wild ones. Yours does seem rather a singular instance. — Ed] LETTERS RECEIVED AND SHORT ANSWERS. Nigel Doble. — A 4-in. object-glass of 66 in. focus ought to suit your purpose. You understand, of course, that for the eye-pieces of which I gave the details on page 79 to give the magnifying powers set against them, it is imperative that they should be em- ployed with an objective of that focal length. Any alteration in that respect would involve a corresponding alteration in their respective powers of amplification. I neither can nor will recom- mend tradesmen. The firm you mention onl}' sell — they do not make— object-glasses. — A. Roberts. See what you can do with X Ophiuchi. This is a very severe test for an instrument of the size of yours, r in the same constellation is, I am afraid, just beyond your instrumental capabilities. Try too the double- double star t'" and i- Lyrge, and see how many stars you can make out between the two pairs. — G. H. Robertson inquires what is the chemical composition of the substance called *' Essence d'Orient " used in the manufacture of artificial pearls. Can any of our readers inform him ? I suppose he does not mean the powdered bleak or minnow scales with which glass beads are internally coated to imitate pearls? — Anonymous (Bradford). Thanks for the cutting from Le Temps containing M. Cotteau's essay on the Krakatoa eruption. It tells in the picturesque French fashion what has appeared in print in other forms over and over again. — John Branch sends me a letter from "Enquirer" with reference to Spiritualism, which is very much too long for insertion. Some years since, impressed to a certain extent by the blatant assertions of so-called " Spiritualists," I investigated the question thoroughly for my own satisfaction; and am hence in a position to reply to, at all events, some of "Enquirer's" queries. Imprimis, neither furniture nor anything else ever moves unless it is pushed or lifted by human agency. In the next place, the whole of the race of mediums (save a very small percentage, indeed, who are insane) are arrant rascals j who, as I have said before in these columns, ought, one and all, to be prosecuted under 5 Geo. IV., c. 83, s. 4. And lastly, do not let " Enquirer " delude himself with the belief that he will be suffered to conduct any experiments in a scientific (to say nothing of a common-sense) fashion. If the "Spiritualists" forming the " circle," find out that he is sceptical, and likely to detect the vile cheat who trades upon the holiest feelings of our nature by pre- tending to communicate with our loved dead ones, he is told that "his influences are antagonistic," and that he must shift his place in the circle, &c., and so he is wedged in between people who take exceedingly good care that he is in no position to lay hold of the medium himself, that medium's paper tube, or anything else that may be "floating" about in the dark. I declare that I have sat in a sort of dumb wonder at the fatuous and idiotic manner in which believers have gone two-thirds of the way to meet the imposture of the medium, when I have been present at a seance, the indifferently-performed conjuring tricks of such mediums having been received by these nobe-mouches as the veritable acts of beings from another sphere ! I have said before, though, and must here repeat, that I cannot Aug. 8, 1884.] ♦ KNOWLEDGE ♦ 123 have the valuable space of Knowledge wasted in the discDSEion of an imposture which is simply a disprace to the boasted intellectual advancement of the nineteeutli century. — Fides. I regret to say that I am ipjnorant of the correspondence class to which yon refer. It was apparently a private adventure, possessing no official cha- racter whatever. — SvnNEV Pockli.nc.tox. To give the objects described as observed with a three-inch telescope, as seen in a two- inch one, would be simply to show them a very little smaller, and not quite so well-defined ; the closest separable double stars, for example, in the large instrument merging into misshapen single ones in the smaller telescope. It would be the veriest waste of space. — Ax AxoxiMors CuKRE.spoxnEXT sends us the Times obituary for July 29, as containing this coincidence : — " On the 25th inst., at Delverton-road, Jlanor-place, Walworth, Jolin Li'jhfning Morgue, aged 75," and " On the 26th July, after three years' suffering, Margaret, wife of Captain George Thunder, aged 31. ' These names are sufficiently uncommon to read oddly in such connection.— A Constant Reader. I have nothing to add to what I said about Professor Loisette's system in Jso. 117. Vou must hence judge of its applicability to your own case. If by " Abstract English History," you mean a cram-book, I can recommend none such. Dr. Wm. Smith's " Smaller English History," though, ought to answer your purpose. Stewart's " Modem Geography," too, pub- lished by Oliver & Boyd, will give you a sound grounning in the subject of which it treats. — H. Francis. Your "Coincidence" is of too doubtful a character to warrant me in wasting space by its insertion. You will see your extracts from the Christian Glohe elsewhere. There is not a trace either of air or water npon the Lunar surface. Did the latter exist, its evaporation must, perforce, form clouds. Of course, the Moon appears inverted as viewed from the Southern hemisphere, i.e., when wo are looking at, say, the "Metropolitan Crater" Tycho, in England with the naked eye, it appears to be at the bottom of the Moon; while, as ■■■iewed from New Zealand, it is at the top. Your difficulty about what you call the "axial inclination " of tlie Moon, arises wholly from the fact that her diurnal path is not parallel to the horizon. For a cognate reason the Great Cross in the Constellation Cygnus rises in these latitudes horizontally and sets perpendicularly. — J. Murray has had an octagonal tin reflector made, and tinds that it gives a number of dim blotches of light when a candle is placed 20 inches from its centre. This, he seems to conceive, affords some sort of explanation of Sunspots ! Like the lamented Artemus Ward, how- ever, " I don't see where the larfture comes in myself." — Excelsior. The Sidereal Messcnro- duced to D, so that the squares on BC and AC with twice the rectangle B C, C D are equal to the square on AB, then AD is perpendicular to B D. This property is often useful, as is the corre- sponding property converse to Prop. 13, viz., — 7/ A B C be an acute angle and a point D i;s taJcen in BC {produced if necessary), such that the squares on AH and BC together exceed the square on AC hij twice the rectangle BC, BD, th&n AD is perpendicular to B D. The proof in either case is easy, for in the first case, if the foot of the perpendicular from A on B C produced, fell othervvise than at D — at E suppose, it can be readily shown to follow from Prop. 12 that C D is equal to C E, which is absurd : and similarly in the second case we can show (if E is the foot of the perpendicular from A) that B E is equal to B D. These propositions mav be referred to as Euc. Bk. II., Props. 12, 13, c,v. com: 124 KNOAVLEDGE ♦ [Aug. 8, 1884. (But Cf)f£(£f Column* Br Mephisto. PROBLEM, No. 122. By T. Simmoxds. Black. Whit*. White to play and mate in three mores. SOLUTION OF PROBLEM, p. 80. PtoQ3 R to B. 1 B to KG (mate). 3. B to Kt7 (mate). 1. P takes P 2. K takes R If 2. Kt takes R 7. 8. 9. 10. One of three 29th of July at Wlite. E. Dale. 1. P to K4 2. Kt to KB3 3. Kt to QB3 4. B to Kt5 5. B to R4. 6. Kt X KP P toQ-i P X Kt Q to Q4 P X B 11. Castles (e) 12. Q to KKt4 13. B to Kt3 14. P to QR4 15. Q to Kt3 16. B to QR3 17. QR to Q sq 18. P to KB4 19. B to Q5 20. P to B4 21. QtoKR4(/; 22. P X B 23. P to K6 24. KRtoKsq, games played blindfold by Mr. Gl'xsberg on the the residence of Dr. J. Ilunt. Black. Gunsberg. P to K4 Kt to KB3 Kt to QB3 (a) P to QR3 B to B4 (6) Kt X Kt (c) B to QKt5 (d) Kt X P B X Kt (ch) Kt to Kt4 Kt to K3 Castles K toRsq. (/■) P to KB4 (g) P to QKt3 {h) R to B2 (i) Qto K sq. B to Kt2 B toB3(,)) R to Q sq. :)B X B (0 Kt to B sq. P X P [. Kt to Kt3 (m) Position after Black's 24th move. Black. 1 ^ it M .-rrrt It t r' - > > - 1 : Whits. White. E. Dale. 25. Q X R (n) 26. P X P 27. P to K7 ! 28. P X R (ch) Kt X P 29. B to K7 Kt to Q2 30. R toK5(9) PtoKtS 31. R to Q5 Resigns. Black. Gunsberg. Q X Q R to B sq. (o) QtoBsq. (p) NOTES. (o) If it was Black's intention to avoid the complications arising ont of the Rny Lopez, by playing the Russian Defence, then he ought to have continued with 3. B to Kt5 ; to this. White's best reply seems to be 4. Kt takes P (for if 4. P to Q3 then P to Q4), B takes Kt. 5. QP takes B, Kt takes P. 6. B to Q3, Ktto B3. 7. Castles, Castles with an even game. The move in the test transforms the opening into a four Knights' game. (b) Some German analysts consider 5. B to K2 to be Black's best reply. If White now or in his previous move plays B takes Kt, then QP takes Kt ; Kt takes P, Kt takes P ; Kt takes Kt, Q to Q5 ; and Black can equalise the game. In reply to B to K2, White might play 6. P to Q3, P to KKt4. 7. B to Kt3, P to Q3, &c. (c) There is no advantage to be gained by B takes P (ch), for although compelled to play K to Kt sq., later on White will obtain a strong centre by P to Q4, and, subsequently, a good development. (d) There is not much satLsfaction to be got from 7. B to Q3, as given by the books, as White comes very strong with 8. P to KB4, Kt to Kt3. 9. P to K5, B to K2. 10. P to B5, &c. (t) Here 11. B to R3 appears to be very strong. ( /) Black's proper reply was 13. P to Q4, threatening Kt to B4, and to exchange the B for the Kt, after which a draw is certain ; if P takes P en passent, Q takes P, and White has no perceptible advantage. (g) 14. P to KB3 was admissible. (h) Seeking to place the QB, but that leaves the QP weak. (t) 16. R to K sq. might have answered better, but Black's posi- tion is weak. (j) B takes B was the correct reply, and after R takes B, Black, although having a cramped game, would have been able to defend himself. (k) A very good move. White tlireateus B takes Kt, and neither the P nor the Q could then retake. (I) Anything but that. Black might have retired his QR to Kt sq. (m) Black had a satisfactory reply in 24. R to B3, i.e. 23. R to B3 24. P takes P R takes R or, B takes Kt Q takes B 25. R takes R R takes P P takes P R takes R, &c. leaving Black with the better game for the ending. (n) This move is as ingenious as it is sound. Mr. Dale has on more than one occasion shown that he is capable of playing in first-rate style. (o) If Q moves, P takes R, and the fi threatens mate. (p) If27. KttakesP. 28. R takes Q,R takes R. 29. Stakes Kt, remaining with two Pawns against the B, perhaps Black's best course. (q) If 30. Kt takes R, then P takes Kt, first followed by R to Q8. "THE CHESS-PLATERS NOTE-BOOK."* We were very pleased with this little book, which is well got up, and contains Diagrams, Letters for sending solutions, Game records, and tables for noting down results. There is a very good shilling's- worth in this useful little book of 150 pages. ANSWERS TO CORRESPONDENTS. ^*^ Please address Chess Editor. Jlinasoto. — The K must never be in check. T. Simmonds. — Ending received with thanks. Correct solntions received. Problem, p. 80 : — J. K. Milne — A. W. Overton. Problem No. 120 : C. T. G., E. Bidgway, George Gouge, Donna, T. Simmonds, John Watson, Uncle John, Minasoto, A. J. Howard. Problem No. 121 : The Owl, A. J. Howard, Minaaoto, S. B. C, Uncle John, John Watson, Geo. Thompson, T. Simmonds, C. T. G., Donna, George Gouge, E. Ridgway, J. K. Milne. Ending, p. 102 : C. T. G., G. Thompson, John Watson. * Rhodes Marriott, 95, Clifton-street, Manchester. Contents op No. 144. rASE Chemistrv of Cookery. XXXIX. By W.M.Williams 81 The Traosmission of Power 82 The Entomology of a Pond. {Illug.) By E. A. BatW 88 Kailway Brakee. Bt " Treritheck " 81 International Health Eihibition. X 86 Other Worlds than Ours. By M. de Fontenelle. With Xotes by Richard A. Proctor 8" The Tricycle of To-day. {Illiti.)... 88 Embalmers 89 Electro-plating. IX. By W. Slingo »i ' Tenns in a Three-inch Telescope, (lUut.) ByF.R.A.S 92 British Seaside Keaorte. II. By Percy Russell 93 A Catastrophe averted by Electric Wires 9« ReviewB 9" The Face of the Sky. By F.B.A.S. 9» Miscellanea 93 Correspondence lOO OoT Mathematical Colomn lf>l Onr Chess Coltmm 102 TEEMS OF SUBSCRIPTION. The terms of Annual Subscription to the weekly numbers of KsowutDGB are a? follows ;— 8. d. To any address in the United Kingdom 16 2 To the C.intinent, Australia. Xew Zealand, South Africa, & Canada 17 4 To the United States of America $4^ or 17 4 To the East Indies, China, &c. {rid Brindisi) 19 6 All subscriptions are payable in advance. OFFICE : 74-76, GREAT QUEEN STREET, LONDON, W.C Aug. 15, 1884.] • KNOWLEDGE ♦ 125 AN ILLUSTRATED MAGAZINE OF SCIENCE LONDON: FRIDAY, AUG. 15, 1884. Contents of Xo. 146. Pleasant Hours with the Micro- scope. (lUui.) By Heiiry J. Slack, F.O.S., F.R.Vr.S 125 The Capture Theory of Comets. By Eichuril A. Proctor 128 Chemistry of Cookery. XL. By W. M. AVilliams 128 Optical Recreations. (lilies.) By F.H.A.S 129 The History of a Lightning Flash. ByW. Slingo 131 The Earth's Shape and Motions. (Illus.) By Hichard A. Pn.ctor. 133 The Entomology of a Pond. (/««».) By E. A. Butler 134 riei Zodiacal Maps. By li. A. Proctor 13ti Other Worlds than Ours. By M. de Fontenelle. AVith Notes by Bichard A. Proilor 136 Remarkable Storms in Belgium 138 International Health Exhibition. XII J38 The Grecly Eipedition 140 Reviews 141 Editorial Gossip 141 The Face of the Sky. By F.E.A.S. 142 Miscellanea 143 Correspondence 143 Our Mathematical Coltinm 145 Our Chess Column 146 PLEASANT HOURS WITH THE MICROSCOPE. By Henry J. Slack, F.G.S., F.R.M.S. THERE is a remarkable group of small insects interest- in;,' to the microscopist on account of their beauty and their strangeness, and interesting, also, in a bad sense, to the agriculturist and the gardener on account of their destructive habits. They belong to the Order Thy sanoptera, or Fringe-wings, characterised by " four wings, alike, narrow, membranous, neither folded nor reticulated, with long cilia>, laid horizontally along the back when at rest." Westwood, in his " Introduction to the Modern Classifica- tion of Insects," cites Haliday, the first important English observer,* and, in the main, agrees with his description of the mouth parts of these creatures, which, he says, " though con- structed " in the mandibulated and palpigerous form, unite into a short conical sucker, which does not extend beyond the anterior coxse." Curtis, in " Farm Insects," specially describes the species which injures corn (T. cerealium), and speaks of the trophi or mouth-parts uniting to form a short beak. Duncan, in his pretty book, " Transforma- tions of Insects," founded upon Emile Blanchard, speaks of this species " nibhUngih^ protecting envelopes of the grain" — a thing they could only do if they had mandibles con- structed for biting, which is not the case. Westwood, although not detecting the principal feeding organ of these insects, judiciously said : " It appears doubtful whether the action, even of the maxilla?, can be transverse, or whether the insect can be said to bite its food." The kind common in greenhouses is rather more than one-fifteenth of an inch long in its adult stage, exclusive of its antennas. Its appearance, when considerably magnified, is shown in Fig. 1. To the naked eye, the full-grown specimen looks black, with white gauzy wings: but when mounted in Canada balsam, and seen with transmitted light, the colours are shades of brown, some much lighter than others, which may be a matter of age. Dark -ground illumination, and a magnification of about 50 linear, makes * " Entomological Magazine," Vols. III. and IV. them objects of great beauty. Each segment of the little creature is decorated with an elegant network pattern. The antenna; are foimed of segments like slender vases, the foot of one in the cup of another, and terminate like the top joints of a fii, and the rostrum can be thrust beyond it. Fig. 3 is a maxillary palp, and Fig. 4 a labial one. Two slender " horny, setiform man- dibles," as figured by Westwood, have sharp and probably piercing tips. In one mounted specimen two fine rapier- shaped instruments are thrust forward in advance of the rostrum, only the tip of which projects a little beyond the " short beak." Are they maxillie ? To see the rostrum, which has escaped the notice of so many observers, the head of the insect should be pushed ofi' by pressing it forwards with a fine needle. This will probably cause the rostrum and some other parts to be seen extending hack- wards. If the ^rst attempt is not successful, the process should be repeated till the end is accomplished. The larva and pupa much resemble the perfect insect, but they are yellow and very transparent. They reach the imago state through a succession of moultings. Their mouth organs seem like those of the adult, and if a few of the larger ones are mounted in thin Canada balsam some are pretty sure to exhibit the rostrum and some of the other mouth parts. In the head of the pupa several long muscular bands to work the mouth-parta are very interesting to view with powers of 200 and upwards. The mandibles and maxillaj are of transparent glassy aspect ; the rostrum is brown and chitinous, deepening in tint towards the tip. When the whole of this organ is seen, it corresponds to a gun with the barrel at an angle with the much curved stock. Not having succeeded in displaying the whole of the mouth organs in their natural position, naming them is uncertain, except as regards the rostrum, which clearly belongs to the Haustellate or Sucking insects, and not to the Mandi- bulate or Biting ones. Their modes of doing mischief are twofold. Firstly, by piercing leaves or other objects of attack, and sucking out the plant juices; and, in the second place, by depositing their excrement in the form of blapk globules as stiti' as tar. Vines and fuchsias are favourite objects of attack. The adults seem to like the upper side of the leaves best, and the little yellow babies and juveniles aS'ect the under side. The latter are so transparent as readily to show the con- tents of their intestines, and it is curious how soon their digestive processes turn the green leaf matter into the black mess which kills the part it is deposited upon. The insects may be seen moving about with balls of this stufi" at the end of their tails. The adults, when disturbed at their work on the leaves, never use their wings in order to escape, but can run pretty quickly. When they get into cucumber or melon frames they are very destructive, and troublesome to get rid of. They can stand a wonderful lot of tobacco-smoking, and most of the vaunted insecticides are of little use. With pot-plants, the best thing is to wash them off with yellow soap, or, better still, with Gishurst Compound, which is a sulphur soap. The damage done by these little pests is always serious It they get into any frame or house, and the species that attacks farm crops is terribly injurious. Curtis quotes Halliday to the effect that in 180.5 they destroyed one- third of the wheat crop in the richest part of Piedmont, and in the same year they caused similar losses to the British farmer. Olives, peaches, melons, and potatoes are assailed by some of the tribe. In attacking wheat, rye, &c., they are found between the interior valve of the corolla and the grain, causing; the latter to shrink, or be pungled, as they call it in Suflblk. In one case an orange- coloured powder was noticed in the grains that had been attacked, and was taken for the insect's excrement, which is not at all like it. Probably the yellow powder was one of the rust fungi.* In preparing these olyects for the microscope some should be mounted whole in thin balsam. To display the wings, the abdomen should be pushed off, and the head, thorax, and wings treated in the same way. What to do with the head has already been explained. The feet do not exhibit the bladder-like endings at all well in balsam. Probably some fluid would do better, but they are very diflicult to make out. Before balsaming the whole insect, it is well to soak it for an hour or two in a drop of carbolic acid, which helps to make the balsam penetrate, and adds to the transparency of the preparation. THE CAPTURE THEORY OF COMETS. By PiicHARD A. Proctor. {Continued from 'page 112.) ARRIVED at Jupiter's distance from the sun, the meteor flight from interstellar space will have a velocity of about eleven miles per second. Now let us inquire what its velocity must be reduced to in order that it may thenceforth be compelled to travel in a circle around the sun. As a matter of fact, all the members of Jupiter's comet-family travel in orbits whose remotest parts are near Jupiter's orbit, and to give a comet riuch an orbit as one of these much more must be done in the way of reducing velocity than is necessary merely to make the meteor flight from outer space travel thenceforth in a circle at Jupiter's mean distance. We are taking, in fact, a very unfavour- able case for our argument Still, the velocity must be reduced, even in this case, by nearly three-tenths, or by more than three miles per second. Now Jupiter's power to withdraw velocity from a body in his neighbourhood is measured by his power to impart velocity. In fact, both processes are but different forms of the same kind of work. Precisely as we say that the sun can communicate a velocity of three hundred and eighty-two miles per second to a body approaching him from interstellar distances, and that therefore the sun can withdraw such velocity from a body leaving his surface at that rate, and eventually bring such a body to rest out yonder in interstellar space, so can we make a corresponding statement for any planet, ^Tupiter or Saturn, the Earth, our Moon, and even for the least of all, the asteroidal family (supposing only the mass and size known). In the case of Jupiter, for instance, we find that the utmost velocity he can impart to a body reaching him from external space is about thirty-six miles per second. That, at least, is the velocity with which such a body would reach the visible surface of the planet What the velocity might be with which the real surface, far down below the visible envelope of clouds, would be reached, we do not know, — not knowing where that surface lies. In the case of oui- own earth, the * Dr. Cooke's " Microscopic Fungi " is a good popular introduc- tion to the study of rast, smut, Ac. Auci. 15, 1884.] ♦ KNOVV^LEDGE ♦ 127 velocity with which a body would reach the surface, if brought thitlicr solely by the earth's action from interstellar space, would be a little over seven miles per second, or more than twenty-seven times greater than the velocity of the swiftest cannon-ball. But wliilo Jupiter — to keep for the moment to our giant planet — has thus, theoretically, the power of giving or taking away a velocity of thiity-six miles per second, he is not practically able to do anything of the sort. He is not left to draw matter to himself, or to act on the recession of matter from bimself, alone. The bodies which come near to him from outer space have been drawn by solar might within that distance from the sun, and almost the whole velocity they there possess is sun-imparted. We have seen what it is — some eleven miles per second. Now mani- festly this greatly affects Jupiter's power of imparting or withdrawing velocity. Both processes require time, and it is clearly impossible for Jupiter to produce anything like the same effect on a body rushing past him with a sun- imparted velocity of eleven miles per second as he would produce on a body left undisturbed to his own attraction. Jupiter's action at any moment is the same whether the body is moving or at rest ; but the number of movements is very much reduced owing to the swift rush of tlie body past the planet. To use the old-fashioned expression of the first students of gravitation (an expression which has always seemed to me amusingly quaint) the solicitations of Jupiter's attractive force are as urgent on a swiftly rushing body as on one at rest ; but if a body will not stay to hearken to them, much less effect must be produced. In all this part of my reasoning, I may remark, I am not pleading a cause, but indicating what every student of celestial dynamics knows. We may fairly regard twenty -five miles per second as the utmost velocity that Jupiter can impart or take from any body coming out of interplanetary space past him, as close as such a body can pass without being actually captured. Moreover, in every possible case, Jupiter can only abstract or add a small portion of this amount ; for this reason, simply, that in every possible case there will be first an action of one kind (abstraction or addition of velocity), and afterward an action of the opposite kind (addition or abstraction respectively). It will be but the difference between these effects, in most cases very nearly equal, which will actually tell on the body's future period of revo- lution around the sun.* This makes an enormous reduction on Jupiter's potency to modify cometic revolution. Cer- tainly ten mUes per second is a very full estimate of the velocity he can abstract or add in the case of a body passing quite close to his apparent sm-face. But even this may seem ample. Seeing that a loss of three miles or so per second would cause a body whicli had reached Jupiter's distance from the sun, after a journey from out of interplanetary space, to travel in the same ])eriod around the sun as .Jupiter himself, and since we seem to recognise a power in Jupiter to abstract ten miles per second, it would seem as though Jupiter's capturing power were in fact demonstrated. But while, to begin with, the close approach required for this capturing power to exist is something very different from that approach within a million miles which I before considered, there is a much more important difficulty to be considered, in the circumstance that we have thus far dealt with Jupiter's capturing power on one body, not on a flight of bodies, such as a comet approaching from interstellar * As distinguished from the orbit. The orbit might be largely affected even in a case where the velocity at Jupiter's distance re- mained absolutely nnchanged; but in this case the period of revolu- tion would remain the same. space is held to be, according to the theory I am discussing. Let us take theformer point, though the least important, first. At Jupiter's apparent surface the actual maximum velocity which the planet could give to a body approaching from a practically infinite distance would be about thirty- six miles per second, and we reduced the actual maximum effect on a body passing Jupiter very close, under such conditions as actually prevail in the solar system, to ten miles per second. Let us see what would be the corre- sponding numbers in the case of a body passing within a million miles of him, remembering that even that would carry such a body right through Jupiter's system of satel- lites, the span of that system being about four and a half millions of mQes. Since a distance of one million miles exceeds the distance of Jupiter's surface from his centre nearly twenty-five times, it follows (I need not explain why ; mathematicians will know, and for non-mathematicians the explanations would be tedious and difficult) that the velo- cities which Jupiter can give or abstract at the greater distance would all be reduced to little more than one-fifth those determined for Jupiter's surface. So, instead of ten miles per second, we should get but two miles per second, as the greatest Jupiter could abstract from a body approach- ing him within a million miles. And this would not be sufficient reduction to make such a body travel thenceforth in Jupiter's period, still less in one of the much shorter periods observed throughout what has been called Jupiter's comet-family. But the other difliculty is altogether more serious. A comet approaches .Jupiter, on the theory we are dealing with, — and indeed the same may be assumed on any theory, — as a flight (jf scattered bodies. Either this flight is so close as to be in effect, because of mutual attractions, a single body, or it is not. If it is, the flight will not be broken up by Jupiter's action ; and, if not so broken up, will remain for ever after a united family. But if, as is more in accordance with observed facts, the cometic flight is so large that the attraction of the flight, as a whole, on the separate members, can be overcome by Jupiter's action, then not only will the flight be broken up, but the orbits given to different members of it by Jupiter's disturbing action will be widely different. Suppose, for example, the extent of the flight to be such that the parts coming nearest to Jupiter approach his centre within fifty thousand miles (a very close approach, indeed, to his surface), while those parts which are remotest from him at the time when the fifght, as a whole, is nearest, came only within sixty thousand miles from his centre. Then, in round figures, the reduction of velocity of the nearer members of the flight will be greater than the reduction for the farther members, as six exceeds five. Supposing, for argument's sake, the former reduction to be three miles per second, as it must be to make those members of the flight travel thenceforth in Jupiter's period round the sun, then the reductiton for the outermost members would be but three and a half miles per second ; or thenceforth one set of meteors -fosmerly belonging to the comet would have at Jupiter's distance a velocity of eight miles per second (eleven less three), while another set would have a velocity of eight and a half miles per second (eleven less two and a half) at that distance. This means that thenceforth the mean distance of the latter set from the sun would exceed the mean distance of the former set about as nine exceeds eight* Since the former set would thenceforth be * The simple law is, that for two bodies having different velo- cities at the same distance from the sun, the mean distances from him differ as the squure of those velocities. Now, the square of eight and a half is seventy-two and a quarter; that of eight is sixty-four. 128 KNOWLEDGE [AcG. 15, 1884. travelling at Jupiter's distance, or about 5 2 times the earth's, the latter set would be travelling at a mean distance greater by one-eighth of this, or -65 of the earth's distance, say some sixty millions of miles. The latter set would be at their nearest to the sun when at Jupiter's distance, would pass sixty millions of miles farther away to their mean distance, and as much farther away still at their greatest distance. Prac- tically, then, even in this case, as favourable for capture as can be well imagined, the capture, though effected, would result in .spreading out the comet, which had arrived as a compact flight of meteors ten thousand miles only in span, over a region one hundred and twenty millions of miles broad. It is hardly necessary to say that nothing like this is observed in the case of any member of Jupiter's comet-family, ^^'e know that along their track meteors are strewn to distances which, in some cases, may well exceed even the enormous distance just named; but they lie along the track, not ranging more than a few hundred thousand miles on either side from the path of the comet's head. This means that the orbit of every single meteor of such a system has, practically, the same mean distance from the sun. The difliculty last considered is simply fatal to the theory that the comets forming what have been called the comet- families of the giant planets were captured by those orbs in the way imagined by Heis, Schiaparelli, and others. THE CHEMISTRY OF COOKERY. By W. Mattieu Williams. XL.— COUNT RUMFORD'S SUBSTITUTE FOR TEA. TAKE eight parts by weight (say ounces) of meal (Rum- ford says " wheat or rye-meal," and I add, or oat- meal), and one part of butter. Melt the butter in a clean iron frying-pan, and when thus melted sprinkle the meal into it ; stir the whole briskly with a broad wooden spoon or spatula till the butter has disappeared and the meal is of an uniform brown colour like roasted coffee, great care being taken to prevent burning on the bottom of the pan. About half an ounce of this roasted meal boiled in a pint of water, and seasoned with salt, pepper, and vinegar, forms *' burnt soup," much used by the woodcutters of Bavaria, who work in the mountains far away from any habitations. Their provisions for a week (the time they commonly re- main in the mountains) consist of a large loaf of rye bread (which, as it does not so soon grow dry and stale as wheaten bread is always preferred to it) ; a linen bag, con- taining a small quantity of roasted meal, prepared as above ; another small bag of 8alt, and a small wooden box con- taining some pounded black pepper ; and sometimes, but not often, a small bottle of vinegar ; but black jjepper is an ingredient never omitted. The rye bread, which eaten alone or with cold water would be verv hard fare, is rendered palatable and satisfactory, Rumford thinks also more whole- some and nutritious, by the help of a bowl of liot soup, so easily prepared from the roasted meal. He tells us that this is not only used by the woodcutters, but that it is also the common breakfast of the Bavarian peasant, and adds that " it is infinitely preferable, in all respects, to that most pernicious wash, tea, with which the lower classes of the inhabitants of this island drench their stomachs and ruin their constitutions." He adds that, " when tea is taken with a suflicient quantity of sugar and good cream, and with a large quantity of bread-and-butter, or with toast and boiled eggs, and, above all, when it is not drank too hot, it is certainly less unwholesome; but a simple infusion of this drug, drank boiling hot, as the poor usually take it, is certainly a poison, which, though it is sometimes slow in its operation, never fails to produce fatil effects, even in the strongest constitutions, where the free use of it is continued for a considerable lensfth of time.' " This may appear to many a very strong condemnation of their favourite beverage ; nevertheless, I am satisfied that it is perfectly sound. This is not an opinion hastily adopted, but a conclusion based upon many observations, extending over a long period of years, and confirmed by experiments made upon myself. The Pall Mall Gaze.Ue of Aug. 7 says :— "There is balm for tea-drinkers in one of Mr. Mattieu Williams's ' Science Notes ' in the Gentleman's Maija~.ine." This is true to a certain extent. I referred to the Chinese as habitual drinkers of boiled water, and suggest that this may explain their comparative immunity from cholera, where all the other conditions for a raging epidemic are fulfilled. It is the boiling of the water, not the infusion of tea-leaves therein, to which I attribute the destruction of the germs of infection. In the note which follows, I proposed an infusion of fried or toasted bread-crumbs, oatmeal, maize, wheat, barley, malt, itc, as a substitute for the tea, the deep colour of the infusion (poured off from the grounds in this case) serving to certify the boiling of the water. Rumford's burnt soup, taken habitually at breakfast or other meals, would answer the same purpose, with the further advantage to poor people of being, to a certain e.vtent, a nutritious soup as well as a beverage. All that is nutritous in porter is in this, minus the alcoholic drug and its vile companion, the fusel oil. The experience of every confirmed tea-drinker, when soundly interpreted, supplies condemnation of the beverage; the plea commonly and blindly urged on its behalf being, when understood, an eloquent expression of such condem- nation. " It is so refreshing " ; "I am fit for nothing when tea-time comes round until I have had my tea, and then I am fit for anything." The " fit for nothing " state comes on at five p.m., when the drug is taken at the orthodox time, or even in the early morning, in the case of those who are accustomed to have a cup of tea brought to their bedside before rising. With blindness still more profound, some will plead for tea by telling that by its aid one can sit up all night long at brain-work without feeling sleepy, provided ample supplies of the infusion are taken from time to time. It is unquestionably true that such may be done ; that the tea-drinker is languid and weary at tea-time, whatever be the hour, and that the refreshment produced by "the cup that cheere" and is said not to inebriate, is almost instantaneous. What is the true significance of these facts ? The refreshment is certainly not due to nutrition, not to the rebuilding of any worn-out or exhausted organic tissue. The total quantity of material conveyed from the tea-leaves into the water is ridiculously too small for the performance of any such nutritive function ; and besides this, the action is far too rapid, there is not sufficient time for the conver- sion of even that minute quantity into organised working tissue. The action cannot be that of a food, but is purely and simply that of a stimulating or irritant drug, acting directly and abnormally on the nervous system. The five o'clock lassitude and craving is neither more nor less than the reaction induced by the habitual abnormal stimulation ; or otherwise, and quite fairly, stated, it is the outward symptom of a diseased condition of brain produced by the action of a drug ; it may be but a mild form of disease, but it is truly a disease nevertheless. The active principle which produces this result is the i Aug. 1.5, 1884.] ♦ KNOWLEDGE 129 crystalline alkaloid, the theine, a compound belonging to the same class as strychnine and a number of similar vege- table poisons. These, -when diluted, act medicinally, that i.s, produce disturbance of normal functions as the tea does, and, like tlieine, most of them act specially on the nervous system ; when concentrated they are dreadful poisons, very small do?es producing death. The non-tea-drinker does rot sutler any of these five o'clock symptoms, and, if otherwise in sound health, remains in steady -n-orkiDg condition until his day's work is ended .and the time for rest and sleep arrives. But the habitual victim of any kind of drug or disturber of normal functions acquires a diseased condition, displayed by the loss of vitality or other deviation from normal condition, wliich is temporarily relieved by the usual dose of the drug, but only in such wise as to generate a renewed craving. I include in this general statement all the vice-drugs (to coin a general name), such as alcohol, opium, tobacco (whether smoked, chewed, or snufted), arsenic, haschisch, betel-nut, coca-leef, thorn-apple, Siberian fungus, mate, itc, all of which are excessively " refreshing " to their victims, and of which the use may be, and has been, defended by the same arguments as those used by the advocates of habitual tea- drinking. Speaking generally, the reaction or residual effect of these on the system is nearly the opposite of that of their immediate efl'ect, and thus larger and larger doses are demanded to bring the system to its normal condition. The non-tea-drinker or moderate drinker is kept awake by a cup of tea or coffee taken late at night, while the hard drinker of these beverages scarcely feels any effect, especially if accustomed to take it at that time. The practice of taking tea or coffee by students, in order to work at night, is downright madness, especially when preparing for an examination. More than half of the cases of break-down, loss of memory, fainting, kc, which occur during severe examinations, and far more fre- quently than is commonly known, are due to this. I frequently hear of promising students who have thus failed ; and, on inquiry, have learned — in almost every instance — that the victim has previously drugged himself with tea or coffee. Sleep is the rest of the brain : to rob the hard-worked brain of its necessary rest is cerebral suicide. My old friend, the late Thomas Wright, was a victim of this terrible folly. He undertook the translation of the "Life of Julius Caesar," by Napoleon III., and to do it in a cruelly short time. He fulfilled his contract by sitting up several nights successively by the aid of strong tea or coffee (I forget which). I saw him shortly afterwards. In a few weeks he had aged alarmingly, had become quite bald, his brain gave way and never recovered. There was but little difference between his age and mine, and but for this dreadful cerebral strain, rendered possible only by the alkaloid (for otherwise he would have fallen to sleep over his work, and thereby saved his life) he might still be amusing and instructing thousands of readers by fresh volumes of popularised archaeological research. I need scarcely add that all I have said above applies to coffee as to tea, though not so seriously in tins coitntrt/. The active alkaloid is the same in both, but tea contains weight for weight about three times as much as coffee. In this country we commonly use about 50 per cent, more coffee than tea to each given measure of water, and thus get about half as much alkaloid. On the continent they use about double our quantity (this is the true secret of " Coffee as in France "), and thus produce as potent an infusion as our tea. I need scarcely add that the above remarks are exclu- sively applied to the habitual use of these stimulants. As medicines, used occasionally and judiciously, they are in- valuable, provided always that they are not used as ordi- nary beverages. In Italy, Greece, and some parts of the East it is customary when anybody feels ill with indefinite symptoms to send to the druggist for a dose of tea. From what I have seen of its action on non-tea-drinkers it appears to be specially potent in arresting the premonitory symptoms of fever, the fever headache, itc. \\ OPTICAL RECREATIONS. Bv A Fellow of the Royal Astroxomical Society. ( Continued /rom page 47.) 7E may fitly conclude our few remarks upon lenses f by a description of the methods adopted to find their foci, which the amateur will often find very useful. First, in the case of a convex lens of any considerable size, a cardboard disc may be fitted at the end of a straightedge accurately graduated into feet, inches, and tenths of an inch, at right angles to its length. This arrangement is then taken out into the sunshine, and the lens whose focal length is to be measured is slid along the straightedge rigidly parallel to the screen, until a sharp and distinct image of the sun is formed upon the latter. The distance between the point where the middle of the edge of the lens rests on the straightedge and the screen may then be taken off' the scale by mere inspection. Or, suppose that we wish to find the focus of our lens when sunlight is not available. We place a lighted candle at the end of a graduated scale of inches and parts, and so connect the lens with the scale that it may always have its axis parallel with the edge of the scale as it slides along it. A card disc, or screen, must also be made to slide along the scale so as to be in a line with the light and the lens, the light being manifestly on one side of the lens and the card on the other. Both the lens and the card must now be shifted backwards and for- wards until the least distance between the light and the card is found, at which a sharp image of the candle is depicted on the latter. Then, if we measure this least distance accurately, it is four times the focal length of the lens. An ingenious modification of this method devised by the Rev. Prebendary Webb, and applicable to the measurement of the foci of the smallest lenses, is illustrated in Fig. 22, in which K N is a Fig. 22. knitting-needle, along which three perforated corks, C, C, C", slide. To the one in the middle, C, the lens, L, whose focus is to be measured, is attached in a vertical position, with its axis parallel to K X ; while in each of the two others is stuck a piece of an ordinary sewing-needle, n, n', point uppermost, and of such a length that a line joining the two points p shall pass, as nearly as can be managed, through the centre of the lens, L. Now, as in our previous experiment, the corks are moved backwards and forwards until the inverted image of the needle-point, n', formed by the lens is seen coincident, and equally distinct, with the point of the needle, n, when both are viewed through a pretty strong magnifier, L', by the eye at E. If this condition of things obtains when the needle-points are 130 - KNOWLEDGE ♦ [Aug. 15, 1884. sensibly equidistant on each side of the lens (and we must shift them about until they are), then, if we take the distance between them very accurately — preferably with compasses and a finely-divided scale — this, as before, will be four times the focal length of the lens for parallel rays. And while on the subject of the measurement of the focus of lenses, we may just mention a simple way in which that of an equi-concave lens may be ascertained ; a kind of deter- mination which sometimes puzzles the beginner. Blacken one side of the lens whose focus you wish to find, and draw a diametrical line across the black backing. On this line make two dots, about the twentieth of an inch in diameter, and equidistant from the centre (or, what is of course the same thing, from the edges) of the lens. Now, hold your lens square to the Sun's rays with its unblacked face turned towards him, and place a card screen, as nearly parallel as may be to the face of the lens to receive the resulting image. Measure very carefully the distance apart of the spots on your lens, and shift the screen about until their images are exactly twice this distance apart ; then will the distance between the screen and the lens be the \"irtual focus of the latter. While we are on the subject of measurement, and before proceeding to the consideration of the structure of the human eye, and of the phenomena of xii'ion, we may say something on the very interesting subject of photometr}', or the measurement of the relative amounts of light emitted by various sources of it. We see lamps advertised which are guaranteed to give the light of sixteen or twenty candles, as the case may be. How can we find out for ourselves whether this quantity of light really is emitted by any given flame or not 1 The principle on which this is done will be apparent from Fig. 2.3, Fig. 23. wherein C is the flame of a candle, from which rays CR, CRi, &c., are radiating. If now we place a piece of cardboard, S, one foot square, at S, a distance of 2 ft. from the candle, C, a glance at our figure will show that its shadow will just cover an area of four square feet (i.e. two feet high and two feet wide), and so on. Or, putting it in another way, if we removed the first screen, S, altogether, the light falling on an equal area of another screen, S', at twice the distance would only be one-quarter as intense as that lighting the nearer screen. At three times the distance, S", the candle would only give one-niuth of the light it does at distance unity ; upon an equal area four times as far ofl', one-sixteenth, and so on. And this we may express in the form of the foUowiug law : the intensity of light is inversely proportional to the square of the distance of the illuminated surface from the source of it. Hence a very little thought will show that when two sources of light produce equal iutensities of illumination at different distances, their illuminating powers must be in the ratio of the squares of their distances from the illuminated surlace. This supplies us with a ready means of measuring the intensity of any given light. For we may adopt llumford's method, illustrated in Fig. 24. Fig. 24. In this figure S represents a white card screen, in front of which stands a rod about as thick as an ordinary drawing pencil. It will be seen that each of the two lights to be compared casts a shadow of the rod, and each light illumi- nates the shadow cast by the other. Let us suppose now that our candle, C, is one foot from the screen ; then if, on moving the lamp, L, to a distance of four feet from the screen, the two shadows appear identical in depth, the lamp really must give sixteen times the light of the candle. It will be quite evident that had it given a precisely similar shadow to that caused by the candle when removed to a distance of five feet, it must have emitted light of twenty- five-candle power, and so on. Bunsen's photometer is, if possible, more simple still in construction, consisting, as it does, mainly of a sheet of white paper with a grease spot on it. This, of course, lets more light through it than the rest of the paper. Hence, if it be illuminated more strongly from behind, it will appear to be bright on a dark ground. If the front surface be the more strongly lighted, it will seem to be dark upon a light ground ; while, if absolutely equally illuminated on both sides, it will disappear as a spot, and be merged in the general surface of the paper. In employing this simple device a sheet of white paper should be stretched on a frame, and the lights, whose rela- tive intensity is to be measured, placed one on each side of it at the height of the spot ; then they are moved about until the spot disappears, and, such disappearance being complete, the distances of the lights are measured from the screen, the squaring of those distances as before giving the com- parative intensities of the lights. One practical word of caution is needed here as to the method of making the grease-spot, as oil would create one of which it would be very difficult to cause the disappearance. The best plan is to let a drop or two of stearine fall on to the paper from a burning candle, and when it has cooled scrape the super- fluous stearine ofi" the paper with a pen-knife. Then the stearined spot should be placed in a fold or two of blotting- paper, and ironed with a hot iron until it becomes of the proper strength. This the reader must ascertain for him- self by direct experiment. The two common forms of photometer which we have just described wUl amply serve to illustrate the principle on which such measurements are made, and will afford the student both amusement and instruction. Into the great subject of celestial photometry we cannot here enter, our object being, as we have before stated, to describe optical experiments which can be per- formed without the aid of any elaborate or costly apparatus, and with materials within the reach of everybody. The Medical Press and Circular savs : — One of the effects of the cholera scare is the sudden increase in market prices of all kinds of disinfectants. Opium, too, has gone np twenty-five per cent., and sulphate of morphine has likewise advanced. We hear that the demand is so great from France that one well-known English house cannot manufacture carbolic acid sufficiently fast to meet it. Aug. 15, 1884.] - KNOAVLEDGE • 131 LIGHTNING THE HISTORY OF A FLASH. By W. Slisgo. LATELY -we have all felt, I doubt not, a considerable amount of interest in the various phenomena attend- ing this summer's unusually heavy thunderstorms, accom- panied, as thej have been, by vivid lightning discharges of a more or less hurtful nature. The list of disasters pub- lished in Knowledge, No. 14.3, might be very materially augmented were we to record such damage as has been wrought since that list was compiled. There is not, I suppose, in the mind of any intelligent man at the preseut day a doubt as to the electrical origin of a lightning flash. The questious to be considered are rather whence comes the electricity ? and in what way is the thunderstorm brought about ] In attempting to answer these questions, sight must not be lost of the fact that the very nature of electricity is in itself almost suffi- cient to baffle any effort put forth to ascertain from light- ning, as such, its whence and its whither. It is possible, however, with the aid of our knowledge of static electricity, to arrive at hypotheses of a more than chimerical nature. In the first place, that our sphere is a more or less electrified body is generally admitted. Jlore than this, it is demonstrated that the different parts of the earth's surface and its enveloping atmosphere are variously charged. As a consequence of these varying charges, there is a constant series of currents flowing through the various parts of the earth, which show themselves in such telegiaph- wires as may lie in the direction followed by the currents. Such currents are known as earth-currents, and present phenomena of a highly interesting nature. But, apart from these electrical manifestations, there is generally a difference of electrical condition between the various parts of the earth's surface and those portions of the atmosphere adjacent to or above them. Inasmuch as air is one of the very best insulators, this difference of condition (or po- tential) in any particular region is in most cases incapable of being neutralised or equilibriated by an electric flow. Consequently the air remains more or less continually charged. With these points admitted as facts, the question arises. Whence this electricity 1 There have been very many and various opinions expressed as to the cause of terrestrial electricity, but far the greater portions of such theories lack fundamental probability, and indicate causes which cannot be regarded as sufficiently extensive or operative to produce such tremendous effects as are occasionally witnessed. I take it that we may safely regard the evolution of elec- tricity as one of the ways in which force exhibits itself, that, in other words, when work is performed electricity may result. When two bodies are rubbed together, elec- tricity is produced, so also is it when two connected metals are immersed iu water and one of them is dissolved, or when one of the junctions of two metals is raised to a higher temperature than the other junction. I will go further than this, so far, in fact, as to maintain that there is reasonable ground for supposing that every movement, whether it be of the mass or amongst the constituent par- ticles, is attended by a change of electrical distribution, and if this is true it may easily be conceived that inasmuch as motion is the rule of the universe, there must be a constant series of electrical changes. Xow, these changes do not all operate in one diiection. nor are they all of similar character, whence it is that not only are there earth currents of feeble electro-motive force, but that this E M F is con- stantly varying, and that, furthermore, electricity of high E JI F is to be met with in various parts of the atmo- sphere. With earth currents we have here very little to do. The rotation of the earth is in itself sufficient to generate small currents, and the fact that they vary in strength at regular periods of the day and of the year enforces the suggestion that the sun exerts considerable electrical influence ou the earth. Letting it be granted, however, that the earth is variously charged, how comes it that the air is also charged, and with electricity of greater tension than that of the earth itself 1 It was pointed out by Sir W. Grove that if the extremities of a piece of platinum wire be placed in a candle-flame, one at the bottom and the other near the top, an electric current will flow through the wire, indicating the presence of electricity. If an electrified body be heated, the electricity escapes more rapidly as the temperature rises. If a vessel of water be electrified, and the water tlien converted into steam, the electric charge will be rapidly dissipated. If a vessel containing water be electrified, and the water allowed to escape drop by drop, electricity wpl escape with each drop, and the vessel will soon be dis- charged. We regard it as an established fact that the earth has always a greater or less charge ; whence it is safe to assume that in the process of evaporation wliich is going on all over the surface of the globe, more particularly in equatorial regions, every particle of water, as it rises into the air, carries with it its portion, however minute that portion may be, of the earth's electric charge. This small charge distributes itself over the surface of the aqueous particle, and the vapour rises higher and higher until it reaches that point above which the air is too rare to support it. It then flows away laterally, and as it approaches colder regions, gets denser, sinking lower and nearer to the eartli's surface. The aqueous particles becoming reduced in size, the extent of their surfaces is proportionately reduced. It follows that as the particles and their surfaces are reduced, the charge is confined to a smaller surface, and attains, therefore, a greater " surface density," or, in simpler language, a greater amount of elec- tricity per unit of surface. Electricity, as above eet forth, is in what is known as the "static" condition (to di>tinguish it from electricity which is being transferred in the form of a current), when it has the property of " repelling itself " to the utmost limits of any conductor upon which it may be confined This will account for the charge finding its way to the surface of the water particles, and will further- more account for the greater density of the charge as the particle gets smaller and has the extent of its surface rapidly diminished. It may be mentioned that the surface of' a sphere varies as the cube of its radius. Returning to the discussion of the state of affairs existing when the particles have reached their highest position in the atmo- sphere, we may imagine that they set themselves off on journeys towards either the north or the south pole. As they pass from the hotter to the colder regions, a number of particles coalesce ; these again combine with others on the road until the vapour becomes visible as cloud. The iiicreased density implies increased weight, and the cloud particles, as they sail pole-wards, descend towards the surface of the earth. Assuming that a spherical form is maintained throughout, the condensation of a number of particles implies a considerable reduction of surface. Thus, the contents of two spheres vary as the cubes of their radii, or eight (the cube of 2) drops on combining will form a drop twice the radius of one of the original drops. We may safely conceive hundreds and thousands of such combinations to take place until a cloud mass isformed, in which the constituent parts are more or le^^s in contact, and, therefore, behave electrically as a single conductor of 132 ♦ KNOWLEDGE ♦ [Aug. 1.3. 1884. irregular surface, upon which is accumulated all the elec- tricity that was previously distributed over the surfaces of the miilions of particles that now compose it. The tendency of an electric charge upon the surface of a conductor is to take upon itself a position in which it may approach nearest to an equal and opposite charge, or, if possible, to attain neutrality. If, then, a cloud has a charge, and there is no other cloud above or near it, the charge induces on the adjacent earth surface, electricity of the opposite kind. Thus, assuming the cloud to be charged with positive electricity, the subjacent earth will be in the negative state. The two electricities* exert a strong tendency to combine or to produce neutrality, whence there is a species of stress applied to the intervening air. Possibly the cloud will be drawn bodily towards the earth more or less rapidly, according as the charge is great or .small. Or, on the other hand, the cloud may roll on for leagues, carrying its influence with it, so that the various portions of the earth underneath become successively charged and discharged as the cloud progresses on its journey. Should the cloud be near the earth, or should it be very highly charged, the tension of the two electricities may be 80 great as to overcome the resistance of the intervening air ; and if this resistance should prove too weak, what happens f How does the discharge show itself 1 It takes place in the form of a lightning flash, and passing from the one surface to the other — or, may be, simultaneously from both — produces neutrality more or less complete. There has recently been a little discussion in these pages on the subject of lightning, some having stated that they discerned the discharge to take place upwards — that is, fi-om the earth towards the cloud. I will not venture so far as to say whether or not the direction of the discharge is discernible ; possibly the flash may sometimes be long enough to enable one to tell ; but I have never so seen it, and have always looked upon the eye as a deceitful member — very. " The lightning flash itself never lasts more than To oWo °^ * second." It is, however, just as likely that a discharge may travel upwards as downwards. What con- trols the discharge? Does the quality of the charge? — that is to say, is the positive or the negative move prone to break disruptively through the insulating medium ? Investi- gations with Geissler's and other tubes containing highly rarefied gases have made it tolerably clear that there is a greater " tearing away " influence at the negative than at the positive pole, and if two equal balls, containing one a positive and the other a negative charge, be equally heated, the negative is more readily dissipated than the positive. But, so far as we at present know, this question enters into the discussion scarcely, if at all. Our knowledge seems rather to point to the substances upon which the charges are collected. The self-repellent nature of elec- tricity compels it to manifest itself at the more prominent parts of the surface, the level being forsaken for the point. The tension of the charge, or its tendency to fly-off, is proportionately increased. And if at a given moment the tension attains a certain intensity, the discharge follows, emanating from the surface which offers the greatest facilities for escape. The earth is generally flatter than the cloud, whence, in all probability, the discharge more frequently originates with the cloud. Should a lightning flash strike the earth and produce direct neutrality, it is possible that no damage will result, * We may speak of two electricities or two electric states without neceBsarilv implying adherence either to the single or the double " fluid " theory. Whether electricity be of two kinds or no, the fact remains that there are two conditions, and all the features of this paper may be explained with equal facility by the supporters of either hypothesis. although this again is not always certain, because when the cloud-charge acts inductively upon the earth it produces the opposite (say negative) charge on the nearer parts, the similar (or positive) state is also produced at some place more or Itss distant. Sometimes this " freed " positive (which, by the way, accumulates gradually and physiologi- cally imperceptibly) is collected at some portion of the earth's surface. When the negative is neutralised by the discharge, the freed positive is no longer confined to a par- ticular region, but tends to dissipate itself, and a shock may be felt more or less severely by any person within the region. Or, again, a similar shock may be experienced by a person standing within the negative zone on the neutrali- sation of the charge. I may take the opportunity here to mention a highly interesting and instructive incident observed on local tele- graph circuits during a thunderstorm. The storm may be taking place at some distance from the point of observa- tion. The electrified cloud induces the opposite charge beneath it, the similar charge being repelled. It is noticeable that the needle of a galvanometer, starting from the middle position, goes gradually over to one side, eventually indicating a considerable deflection. Suddenly, owing apparently to a lightning discharge some distance away, the force which caused the deflection is withdrawn, and the needle rebounds with great violence to the opposite side. In a short time, the cloud becoming again charged on its under surface, and recommencing its inductive eflfect upon the subjacent earth, the needle starts again, and goes through the same series of movements, a violent counter- throw following every flash of lightning. If we can so far control our imagination, we may con- ceive the earth to be one large insulated conductor, suscep- tible to every influence around it If, then, the earth, as a mass of matter, behaves as above indicaf;ed, there is no plausible reason for declining to regard any other large conducting mass in a similar Ught, and, as a body capable of being subjected more or less completely to the various impulses affecting the earth. In other words, a large mass of conducting material, partially or perfectly insulated is, during a thunderstorm, in considerable danger. With this portion of the subject I shall, however, deal more fuUy when discussing the merits of lightning protectors. Lightning discharges do not take place between cloud and earth only, but also, and perhaps more frequently, between two oppositely-charged clouds. We then get atmospheric lightning, the flash often extending for miles. This form of lightning is harmless, and in all probability what we see is only a reflection of the dis- charge. The oft-told tale of the lightning flying in at the window, across the room, and out of the door, or up the chimney, is all moonshine, and before dealing with lightning- protectors I intend to expose some of the fallacies con- cerning lightning. Were the discharge to pass through a house it would infallibly leave more decided traces and do more damage than simply scaring a superstitious old lady now and again. Many people are often and unnecessarily frightened during a thunder-storm, but it may be safely predicted that a person under a roof is infinitely safer than one who is standing alone on level ground, and making himself a prominence inviting a discharge. Rain almost invariably accompanies the discharge, and the roof and sides of the house being wet, they form a more or less perfect channel of escape should a flash strike the building. Glass-making ix Italy. — Colle de Val d' Elsa contains one of the most important glass-works in Italy. The value of the annual pro- daction amounts to 2,500,000 lire; its sale extends overall Italy, but more especially in the Boman, Tuscan, and Piedmontese provinces Ave. lo, 1884.] • KNOWLEDGE ♦ 133 THE EARTH'S SHAPE AND MOTIO^^S. Bv EicuARD A. Proctor. (Continv/cd from page 109.) CHAPTER I.— THE DAILY IIOTIOX OF THE SUX. '^I'^HE first impression which the aspect of the earth and .L sky gives to the observer is that the earth is a vast plain over which the sky extends in the form of a dome. £ propose in the present chapter to consider the lessons =A'hich may be learned from the most easily recognised of all the forms of motion which this dome presents to our -contemplation. Each day we see the sun rise towards the east, pass to the highest point of his path in the south, and then set towards the west.* Xow the diurnal motion of the sun is far more instructive ■than is commonly thought. To say merely that the sun rises towards the east and sets towards the west, is to mention nothing which can teach the real significance of the motion. For we might see an object apparently rise towards the east, culminate in the south, and then set in the west, while the real character of its motion was totally different from the sun's, and due to causes of another sort. 'It is the rate of the sun's motion and the figure of his apparent path which are so instructive. I will describe some simple observations which will show this. Here in England, when the sun rises nearly in the east and sets nearly in the west — in other words, in spring Rnd autumn — he attains in the south a height of about 38i deg. Suppose, then, that we fix a rod in such a posi- tion that it will be square to a plane passing through the east and west point, and also through the highest point of the sun's path. In other words, let it have the position indicated in the figure, where N S represents the north and south line, E W the east and west line, O L (Fig. 1) the direction of the sun at noon, in spring or autumn, and O P the rod, which points towards the north, but is inclined Fig. 1. ■>ih deg. to the horizon (51| being the angle, which with •iS^ deg. makes up a right angle). Now to the rod 0 P let the observer attach a cross-wire L K N at right angles to the rod, and another cross wire, K M, at right angles both to the rod and to L X ; and let L K, K M, and K N be made equal. Then bend a strip of card or paper into a semicircular shape, and attach it, as •shown in the figure, to the ends of the wire. Set the rod in the sunlight in the position shown in Fig. 2, ^nd so that the wire L K N may point east and west ; no great exactness is required in this last respect. Now at any hour observe where the shadow of O P falls * I Bay towards the east and towards the west, for, as a rale, the san does not rise exactly in the east nor set exactly in the we3t, and ir is worth noticing in passing that in no place has the sun, since the world began, ever risen exactly in the east and set exactly in the west on one and the same day. on the strip of paper, as at R, and put a pencil-mark there. Half an hour later repeat the observation, and set another mark where the shadow now falls. Do this from half-hour to lialfhour, or at shorter or longer intervals, as may b« most convenient, only the successive intervals must be all equal, and carefully timed. Finally, remove the strip of paper, straighten it, and measure the spaces between suc- cessive marks. These will be found exactly equal. Fig. 2. Fig. 3. In describing this experiment I have for convenience spoken of a day in spring or autumn ; because this gave the readiest way of showing how the position of O P was to be determined. But this position once fixed (in other words 0 P set up in such a way as to point towards the north at an angle of 51^ deg.) the same experiment can be tried on any day of the year with prei:isely the same result. We have no^ learned an important truth about the rate of the sun's motion ; we know that if a plane were taken always through O P and the sun, this plane would revolve uniformly on O P as an axis. But we want to know further what the shape of the curve traversed by the sun may be. This is easily accomplished by the same simple instrument. We have only to turn the rod O P on its axis, keeping its direction unchanged, until the circular strip has its centre towards the south, as shown in Fig. 3. Then note where the shadow of the strip falls on the rod, as at S T ; i< tvill be found that the position of the shadow remairis unchanged throughout the day. Now, what does this result teach us \ The following illustration will show : — Suppose we attach to O P (Fig. 4) a straight rod A S, in Figs. 4 and 5. such a position that the point S coincides with the shadow of the upper rim of the paper strip, whUe S A just touches that rim. (The strip is removed from the figure for the sake of distinctness.) Then, since the sun's rays towards 0 P, crossing the top of the paper strip, fall at S, we can, by merely turning 0 P round on its axis without changing its position, make S A point exactly at the sun. And as 134 KNOWLEDGE • [Aug. 15, 1884. this is true at any part of the day, we can make S A follow the sun by eimply turning O P ii,iiiforriihj (remembering what we have already learned about the rate of the sun's motion) on its axis. Here, then, we have the simplest conceivable account of the sun's diurnal motion, we have a fixed axis O P pointing towards the north and inclined at an angle of 5 1 h degs. to the horizon. We have a straight rod S A, projecting from O P at a fixed angle determined for each day, by experi- ment ; and by merely rotating O P uniformly on its axis, we can make S A point towards the sun all through the day. We can now combine what we have learned in an in- structive instrument which any handy person can construct with the utmost ease, and which will afford the most satisfactory information concerning the sun's daily motion. A B, B C, Fig. 5, are two rods forming a/ight angle, and of such length that a line from C to A may be inclined 5H deg. to A B. D E is a cross-rod for supporting A B C in an upright position. F G is a rod revolving easily in the pivot-holes at F and G. H K is a circle of card or other material, marked round its circumference with degree divisions. L M is a rod turning round on a pivot at O (the dotted figure shows the nature of its motion,) and bearing a small card circle M. The instrument must be set upright, A B pointing due north and south, as shown. Then turn the rod F G on its axis, until L M can be made to point to the sun. It will be easy to know when this is the case by observing that when L M is pointing directly towards the sun, there will be no shadow of L M on the paper circle M. (The pivot on which L M turns .should be so placed as to keep L M an inch or so from G F, and should also be perceptibly smaller in diameter than L M. When this is attended to it is easy to direct L M towards the sun by observing its shadow, and making this shadow disappear.) The instrument is now ready for use. We note the division on the card H K which falls opposite the mark at K on the rod B C. Half-an-hour later, say, we inspect the instrument, and we find that L M now throws a shadow on the card M. We turn F G round on its axis until this shadow disappears. We find that this happens without our having occasion to shift L M, and we notice also that the card circle H K has to be turned through an angle of 7i deg. At the end of another half-hour the same motion has to be repeated. And the same happens whatever day of the year it may be. Now one day's observation of the sun with such an in- strument teaches us this first important fact : — If E S P W represents the dome of the heavens, K L N the sun's diurnal path, OPa point towards the north 51 i deg. above the horizon ; then every point of K L N is equally distant from T?,for the main axis of our instrument pointed throughout towards P, and the cross-rod, which v:e made to point to the sun, was inclined througliout at a fixed angle with that main axis. If, then, the sun's apparent motion were due to a real motion of his in a circle, that circle must have the inclined position K L M. Again we have learned that the diurnal motion of the sun is either really uniform, or is apparent and due to some uniform motion of our earth's Again we have learned that our earth is not an infinitely wide plane, but that the sun rises from beyond the earth's limits on the east, and sets beyond the earth's limits on the west. For having found that our instrument follows the sun from the time of his rising fairly above the horizon, all through the day, until he approaches the horizon again in the west — by merely giving a certain uniform rotation to the axis F G, we are justified in assuming that there is no break in the continuity of this motion at sunset, but that by turning the axis round after the sun has dis- appeared, at the same rate at which we have moved it during the day, it will still point to his place. Xow, doing this, we find the rod L M pointing below the horizon after Fig. 6. sunset. Further, by continuing the motion we find the rod L M pointing lower and lower until near midnight, when it is directed due north, and downwards, as towards R, in Fig. 6 ; then gradually it rises towards the east, and when it again becomes horizontal we find it pointing directly towards the rising sun. {To ie continued.) THE EXTO^klOLOGY OF A POXD. {Continued.) By E. a. Butlee. LEAVING now the middle depths, which have detained us so long, and continuing our descent, we reach the Bottom of the Poxd. The bottom of a pond can hardly be considered a par- ticularly attractive abode, at least so far as appearances are concerned, and if one remembers its usual composition it will appear even less desirable as a home. Here is col- lected a fine mud, composed of the remains of all sorts of rubbish that is continually being rained down from the watery heights above. It is, as it were, the dust-bin, the cesspool, and the cemetery of the pond. Dust blown in from time to time by high winds, fragments of plants broken from aquatic vegetation, dead leaves and bits of stick fallen from the trees on the banks, the excrement of the insect and other inhabitants, together with fragments left from their repasts, empty shells of aU sorts of water- snails, cast skins of larv.'e, the dead bodies of the multitu- dinous aquatic population (and the mortality in a thickly populated pond must be considerable) together with those of worms and other terrestrial creatures that have had the misfortune to fall in and be drowned — these are some of the materials that, besides the mere earthy matter, help to form the ever-increasing mud at the bottom. There are, however, multitudes of nainute creatures constantly at work on this refuse matter, di\-iding it up, and transforming the dead and eflfete materials into the living tissues of their own bodies, and therebj- reducing the ultimate waste sub- Aug. 15, 1884.] ♦ KNOAVLEDGE 135 stance to a much smaller bulk, and rendering it innocuous to a degree that might at first seem impossible. Halt buried in this mud, or slowly crawling over its surface, are the lurking monsters of entomological pond life, the majority of which belong to two orders we have hitherto scarcely noticed, the Neuroptera and Trichoptera, the former containing the dragon flies, and the latter the caddis flies. We will, however, first consider certain bugs which haunt these parts. They are known as water scorpions, and two species inhabit this country, one commonly found in almost every pond, the other of much less frequent occurrence. They have, of course, no connection with the true scorpions, which are not insects at all, but eight-legged creatures belonging to the class containing spiders and mites. The water scorpions, too, unlike their terrestrial namesakes, are not venomous. The first, and much the less common, is Fig. 1. — Eanatra linearis (reduced). a long, narrow insect, called Ranatra linearis (Fig. 1). On account of its habit of frequently lurking in an inclined position amongst the water weeds, often only a little below the surface, this creature belongs less to the fauna of the bottom than its common relative. Still, they are best treated of together. It is of a brownish colour, except the upper surface of the abdomen, which is scarlet, but this is concealed when the insect is in the water, being made apparent only when the wings are expanded, and then it is quite astonishing to see what a beautiful creature the apparently uninteresting object becomes. The head is small, but the eyes exceedingly prominent, as is often the case with aquatic insects, and the beak short and sharp, not bent underneath, but projecting in front like an ex- tremely acute nose. Both thorax and abdomen are elon- gated to an enormous extent ; indeed, the insect, with a length of an inch and a- half from tip of snout to end of abdomen, has its greatest breadth no more than one-sixth of an inch. The upper pair of wings, whDe almost abdomen, are each only about but the hinder pair are con- and have to be carefully folded be stowed away under their narrow covers. These hind wings are beautifully delicate and transparent, similar, indeed, to those of the Corixidae before referred to. But when we have reached the tip of the abdomen, we have by no means got to the end of the insect ; from this point there extend two long bristle-like organs, about an inch in length, which project straight behind like a stiff tail ; they are tubular, and communicate as long as the half its width, siderably broader, up before they can at their base with the tracheal system, and are, of course, respiratory in function. The legs are long and slender ; the first pair are not used for progression, but for seizing prey, and it is these in front, and the respiratory filaments behind, that give the creature whatever resemblance it may have to a scorpion, although the similarity to that venomous animal is not nearly so exact as in the other species to be considered presently. The front legs are most remarkable objects, and will well repay a careful study. To understand clearly their peculiarities, we must first refer to the general plan of an insect's leg (Fig. 2). Fig. 2. — (A) Fore-leg of Eanatra ; (B) Leg of Stag-beet'e. a. Coxa ; i. Trochanter ; c. Femur ; d. Tibia ; e. Tarsus, There is first a joint, usually comparatively small, and more or less globular, called the coxa, by which the leg is articulated to the body, and which is usually invisible from above. Succeeding this is a small triangular joint, called the trochanter, squeezed in, as it were, between the coxa and the next joint, and looking as if added, as an after- thought, to fill up a gap. Then follows, attached to the side of the trochanter, the first long piece of the leg, the thigh, or femur, then another long piece, the shank, or tibia, and lastly the tarsus, or foot, which is composed of from two to five joints, and usually terminated by a pair of claws. Now let us take one of Ranatra's fore-legs and compare it with this plan. First we find a long joint, which extends far beyond the head, but still, from its being that which articulates the leg to the thorax, we know it must be the coxa, though it protrudes so far that we may easily at first mistake it for the thigh. Then there is the trochanter, a little larger and more conspicuous than usual, and this is succeeded by a long piece slightly curved at the further end, and with a tooth a little beyond the middle ; this, of course, is the femur. After this there is a short, sickle- shaped part, less than half the length of the femur, and looking like a great claw ; it is able to be folded back upon the inner edge of the femur, along which a narrow groove, serrated at the edges, is excavated to receive it, and then its tip just reaches the above-named tooth. This sickle- shaped part consists of both tibia and tarstis, the latter of which is very small and has no claws. It will thus appear that the leg proper is, as it were, spliced on to the end of a long handle, the elongated coxa, an arrangement the efiect of which is to give the limb much greater freedom of motion and a much wider sweep, and thus to enable it to levy tribute over a much more extended area. So peculiar is the plan of these Limbs that it is no wonder that many persons have been puzzled to understand them. We must leave the habits of Ranatra for consideration in the next paper. (To be continued.) The Fkexch Eiectrical Power Stoeace Cojipaxt. — Yice-Chan- cellor Bacon made an order on Saturday week for the winding-up of this Company on the petition of the Faure Electric Accumulator Company. It was stated in court that the proceeding was rendered necessary by the frauds of M. Phillippart, whose name has been so intimateh- associated with electric lightning and accumulatoi-s. 136 • KNOWLEDGE * [Aug. 15, 1884. z\a^ x^ Day Sign for the ilonth. ZODIACAL MAPS. By Eichakd A. Proctor. WE give this week both the day sign and the night sign for the month, one showing the zodiacal sign now high in the heavens at midnigJit, the other showing the region of the zodiac athwart which the sun pursues his course at this part of the year. OTHER WORLDS THAN OURS. A WEEK'S CONVERSATION ON THE PLURALITY WORLDS. By Moss, de Fostenelle. OF B WITH NOTES BY RICHARD A. PROCTOR. (Continued from p. 118.) UT pray," said she, "how can the earth with all its weight, be borne up by your celestial matter, which must be very light, because it is so fluid ? " " It does not argue," said I, " that what is most fluid is most light : for what think you of the great ship I men- tioned just now, which with all its burden is yet lighter than the water it floats on ? " " I will have nothing to do with that great ship," said she, with some warmth, " and I begin to apprehend myself in some danger on such a whirligig as you have made of the earth." " There is no danger," replied I ; " but, madam, if yoi<- are afraid, we will have the earth supported by four elephants, as the Indians believe it." " Hey-day," cry'd she, " here's another system ; however, I love tho.«e people for taking care of themselves ; they have a good foundation to trust to, while you Copemicans are a little too venturous with the celestial matter : and yet I fancy, if the Indians thought the earth in the least danger of sinking, the}'- would double their number of elephants." " They would do well," said I, laughing at her fancy, " who would sleep in fear ? and if you have occasion for 'em to-night, we will put as many as you please in our system ; we can take 'em away again by degrees, as you grow better confirm 'd." " I do not think 'em very necessary," said she ; " I have courage enough to turn." "You shall turn with pleasure, madam," said I, " andr shall find delightful ideas in this system : For example, sometimes I fancy myself suspended in the air, without any motion, while the earth turns round me in twenty-four hours ; I see I know not how many difierent faces pass under me, some white, some black, and some tauny ; some- times I see hats, and sometimes turbans ; now heads with> hair, and then shav'd heads ; here I see cities with steeples, others with spires and crescents, others with towers of porcelain, and anon great countreys with nothing but cottages : here I see vast oceans, and there most horrible deserts : In short, I discover the infinite variety which is upon the surface of the earth." " I confess," said she, " twenty-four kours would thus be Au.;. 15, i88i.] KNOWLEDGE 137 [AgUARIUS ^Vi*« X2**T H,37 *45 *50 ^V- . et 1 m*r i^ •« * CCAPR/CORNU: I * CMicroscoDiumJ Xight t iffn for e Month very well bestow'd, so we were in the same place where we are now : I do not mean in the Park ; but we will suppose ourselves in the air, other people contioually passing by, who take up our place, and at the end of twuatj-four hours we return to it again." " Copernicus himself," said I, " could not have compre- hendt'd it better. First, then, we see some of our neighbours iiassiiig by us, up to the ears in politics, yet settling their nation no better than we do the world in the moon ; then follows a great sea, perhaps a Heet of ships, perhaps a rnackrelboat, no matter whether; then come some of the Iroquois going to eat a prisoner for their breakfast, who veems as little concerued as his devourers ; after, appear the nomen of the land of Jesse, who 'spend all their time in ■ Iressing their husband's dinners and suppers, and painting tdeir lips and eyebrows blue, only to please the greatest lirutes in the world ; then the fair Circassiaus, who give all tlieir love to the first comer, except a little they reserve for their husbands ; then the Tartars going to steal concubines tir the Turks and Persians ; and at last our own dear oountrymen, it may be in some points as ridiculous as the best of 'em." "It is very pleasant," said the Marchioness "but to imagine what you tell me ; tho' if I were above, and saw all this, I would have the liberty to hasten or retard the motion cf the earth, according as the objects pleas'd me more or less ; and I assure you I should quickly send packing the politicians and man-eaters, but should have a .irreat curiosity for the fair Circassians, for methinks they iiave a custom very particular. But I have a dilKculiy to dear, ! nd you must be serious. As the eaith moves, the air changes every moment, .-o we breathe the air of another country. " " >'ot at all," replied T, " for the air which encompasses, the earth does not extend above a certain height, perhaps twenty leagues ; it follows us, and turns with us. Have you not seen the work of a silkworm, the shells in which those little animals imprison themselves, and weave with, so much art 1 they are made of a silk very close, but ar& covered with a down very slack and soft ; so the eaith, which is solid, is covered from the surface twenty leagues, upwards with a kind of down, which is the air, and like the shell of the silkworm turns at the same time. Beyond the. air is the celestial matter, incomparably more pure and subtle, and much more agitat>d than the air." "Your comparison," said she, "is somewhat mean, and yet what wonders are wrought, what wars, what changes in this little shell." " ' Tis true," I replied, " but nature takes no notice o£ such little particular motions, but diives us along with the general motion as if she were at bowls." " Methinks," s-aid she, " 'tis very ridiculous to be upon, a thing that turns, and yet not be well assured that it does, turn ; and to tell you the truth, I begin to distrust the- reasons jou give why we should not be sensible of the motion of the earth ; for is it possible there should not- some little mark be left by which we might perceive it • " " All motions," said I, " the more common and natural they are, are tliH less perceptible : and this holds true e\ec in moralitv. The motion of self-love is so natural to us,, 138 • KNO\A/'LEDGE ♦ [Aug. 15, 1884. that for the most part we are not sensible of it, and we believe we act by other principles." "You are moralising," said she, "to a question of natural philosophy : But 'tis enough for the first time ; let us now go home, and meet here again to-morrow, you with your systems, and I with my ignorance." In returning to the Castle, that I might say all I could on the subject, I told her of a third system, invented by Tycho Brahe, who had fixed the earth in the centre of the world, turned the sun round the earth, and the rest of the planets round the sun ; for s-ince the new discoveries, there was no way left to have the planets turn round the earth. But the Marchioness, who had a quick apprehension, said, she thought it was too aflected, among so many great bodies, to exempt the earth only from turning round the sun ; that it was im- proper to make the sun turn round the earth, when all the planets turn round the sun : and tbat tho' this system was to prove the immobility of the earth, yet she thought it very improbable. So we resolv'd to stick to Copernicu!;, whose opinion we thought roost uniform, probable, and diverting. In short, the simplicity of his system convinces us, and the boldness of it surprises with pleasure. (To be contimied.) REMAEKABLE STOEMS IN BELGIUM. A NUMBER of very remarkable storms occurred in Belgium in July, 1884, and the following account is taken from reports made to the Observatory at Brussels. On the 4th, at Lamorteau, near Virton, from 2h. 34m. to 5h. 22m. p.m., ttere was a storm wind, and during eighteen minutes a great fall of hail, making the fields look as if thickly covered with snow. The hailstones were at first the .size of nuts, and then of large peas. At Thirimont, near Beaumont, on the 5th, the hail was the largest ever known there. The stones had sharp angles, and did great damage to crops. The storm did not extend beyond a radius of 1,500 metres. On the 13th, at Bruges, during a severe storm, the sky looked as if instead of clouds there were vast eddies of smoke from a huge fire, reflecting flames. The movements of the lower clouds increased in rapidity, the wind rose to a hurricane, and snapped great branches off the trees. Transparent hailstones fell for five or six minutes, the size of small nuts. At Maldegem, east of Bruges, almost at the same time, there was a deluge of rain mingled with pieces of ice from 25 to 40 millimetres in diameter (1 inch to li). They were round, lenticular, and angular, striking the ground with extraordinary force. A water- spout passed within 3,000 mfetres, destroying hundreds of trees. At Ostend, on the same day, some hailstones were as big as j)igeons' eggs and some as big as fowls' eggs. One of these, when cut in the direction of its longest diameter, exhibited a nucleus, surrounded with successive layers, alternately transparent and opaque. The surface was very irregular, with clear protuberances. At Haesrode, near Louvain, at 2.30, on the 13th, a small white cloud appeared and suddenly discharged hailstones as big as eggs, one weighing over 8 oz. They varied in shape — oval, hemi- spherical, triangular, and some spinous, like a prickly pear. This storm only lasted three or four minutes, and only ex- tended over the small space of from half a metre to a mfetre ! At Hechtil (Limbourg), on the same date, hail- stones fell over 3 inches in diameter. During the storm of July 13, Baron van Ertborn, at Aartselear, near Antwerp, examined with a telescope a large cloud 50 deg. above the horizon, and saw that it was formed of seven superposed layers, the lower ones eddying and moving quickest. Curved flashes of lightning darted from one layer to another. On July 17, near Arlon, pieces of ice fell 3 to 31 inches in diameter, breaking glass, kill- ing poultry, and cutting fruit-trees. Storms of this kind are said to be very rare in Belgium. S. THE INTEENATIOXAL EXHIBITION. HEALTH XII.— WATER AXD WATER-SUPPLIES— (conHnued). THE description of Mr. Roberts's " Rain -Water Separator," given in our last communication, is an apt introduction to the subject of water-purifying appli- ances, which we now propose to deal with. In the " East Central Gallery B," may be seen, in active operation, all the forms of apparatus that are of any value in the present enlightened day, when Darwin's great law of the "survival of the fittest " holds its sway more powerfully than ever. The plan we have chosen to adopt in our remarks upon the inventions here displayed, is to place before our readers a descriptive account of the fyjies that have been resorted to in gaining certain desired ends, rather than a serial dis- course upon the relative merits of the various patents. In illustration of these principles, we shall select the most suitable examples at our dbposal, so that our series of reviews shall embodj^ a digest of the highest possible value for those who wish to exercise their own discretion in the choice of what we deem to be one of the most essential requisites in every household — a good filter. Type I. — As a natural sequence of the rain-water sepa^ rator, which is adapted to procure a supply of good soft water suitable for all domestic purposes, save drinking,* we would draw attention here to " Stall 420," and the " Grant Revolving Ball Water Filter," the value of which lies in the fact that a tolerably pure water, such as that derived from a Roberts Separator, or delivered to town and suburban dwellings by water companies, may be rendered fit for drinking in an incredibly short space of time. It is, without doubt, the best rapid water filter for the above-mentioned sources of supply ; it can be fastened on to any existing water-pipe with the utmost ease ; may be as readily cleansed and re-charged with the filtering medium ; and, when " turned on full," there is but a slight, almost inappreciable, diminution in the rapidity of flow from the tap. We can safely recommend this filter to the notice of those who desire to have an unlimited supply of good, pure water always readily available, more especially in the kitchen ; and to convince our readers of its practical utility, we cannot do better than give an outline of its general anatomy. So far as we are aware, this type of filter stands alone — it has not yet been copied ; in one par- ticular, however, it may be placed amongst the so-called high-pressure filters. The " Grant Revolving Ball Water Filter " consists of a spherical metallic case, the smallest manufactured size of which, for domestic purposes, is about 2 inches in diameter, and under pressure from the tap diminishes the ordinary rate of delivery by about only 20 per cent. Within the case there is a hollow metal ball, designed to hold the filtering medium (granular animal charcoal), and every drop of water which passes into the mechanism is forced * In making this proviso, we desire it to be understood that, in most cases, the rain-water obtained through the tise of the Roberts " Separator," may be also used for drinking ; but it is well to pnrifj- it still further by efficient filtration, so as to render the result doubly secure. Aug. 15, 1884.] • KNOWLEDGE • 139 to percolate through the filter. This is secured by a washer, which forms a tight joint around the ball. The water may be permitted to pass through imfiltered along the passage B B, Fig. 21 ; but when the packed handle C is revolved so as to bring the filter into operation, the water Fig. 21.^Seotional view ..f " The Grant Revolving Ball Filter." A A, patent cup and joint washer, packed by pressui'e of water ; B B, direct way for water through ball icithout filtering ; c, packed handle to reTolre ball ; D D, bearings upon which ball revolves ; E E, animal bone, charcoal, or filtering medium : F f, bars inside of ball npon which the water strikes when filtering, preventing drilling of charcoal; H H, shell containing ball; i, section of wire screen or sieve which holds charcoal into the ball, and through which water passes when filtering. strikes upon the bars F F, thus breaking its initial force, and causing it to spread over the whole body, whence it finds its way through the charcoal with an equalised pressure, thereby securing perfect filtration with a minimal disturbance. The matters which accumulate in the filter may be removed by a simple revolution of the ball, and the entire system thus cleansed in a few seconds. An objec- tion to this method of cleansing is, that it is at most only approximately effective, but that is all that is really neces- sary in a filter of this kind ; and, moreover, should the objector be unusually fastidious, he may, at the worst, remove the charcoal, wash it thoroughly, and return it to its receptacle, or supply its place with a fresh charge, which is easily done at but a nominal expense. The entire appa- ratus is inexpensive, portable, almost indestructible, effective, and even elegant ; it speaks very highly for the ingenuity of its transatlantic inventor. The carbon recom- mended for use is in a sufficiently fine state of division to act as a thorough mechanical strainer ; it also acts chemi- cally, if we are to judge from analyses of the filtrate. Type II. — Although we strongly object to the old- fashioned " block " principle in filters, we are constrained to admit that there are some of them which it would be unjust to leave unnoticed, since they achieve results which place them amongst the best of modern inventions. Of these, " Doulton's Manganous Carbon Filters " deserve a special notice ; they may be seen and tested in the western annexe of their Pavilion in the " Central Gallery." Before we proceed to describe the action of these filters, we desire to draw attention to one of the most important features in the construction of filter-cases which is strikingly exemplified in Messrs. Doulton's patent. These are the only filters extant where anything of the kind has been Fi" adopted. Fig. 22 will help us to explain more clearly than any written description alone, how every drop of filteied water becomes available, and is prevented from getting stale by the gentle slope of the floor of the reservoir to the tap, which is situated below the level of that floor. In most filters this item is generally overlooked, with the consequence that the lowest stratum of water may lie unused within the reser- voir of the filter sufliciently long to become either mawk- ish or positively harmful through the accidental in- troduction of aerial germs, which usually gravitate to the bottom of the water. To this class belong certain forms of the minuter Algce and Rotifera, not to sjieak of Bac- teria, which in their totality may, and almost always do, pro- duce, in about ten or twelve days, an undesirable adherent slimy layer at the bottom and lower sides of the reservoir. This state of affairs may be observed in the form of filter- case shown at Fig. 23, where the position of the tap necessitates a constant remnant of unusable water, which has there- fore to be cleansed out periodically. As the majority of filters now in use are all modelled upon the type of Fig. 23, we would here offer our practical advice to such of our readers as may^ possess filters of this sort, which is : — To be careful to thoroughly wash out the reservoir at least once a week ; ''"S- ^^- this will be sufiicient to insure them against the possible sources of contamination to which we have alluded. Another praiseworthy fact about Doulton's filters is^ that their taps are made of ^^^ stoneware, and hence are not liable to the inevitable corro- sion, to which metal taps are subject, which, if not positively dangerous, are at least objection able on the score of cleanliness. "We would, of course, expect to find elegantly-shaped and beautifully-decorated filters at Messrs. Doulton's, nor are we doomed to disappointment. Apart from strict utility there is an indescribable charm about an artistically finished production, such as that re- presented at Fig. 24, which raises it above the common- place, to rank amongst the things that are to be desired. ■m//a//,'/.VyM>'- \ -^ a^^ i:i. 140 • KNC^/VLEDGS • [Arc. 15, 1884. THE GREELY EXPEDITION. IT was August 18, 1881, that the ofEcPrs and crew of the Frotei's bade good-bye to Lieutenant Greely and his little band, twenty-live in all, leaving them iu camp, as an advance guard of explorers, in a high northern latitude. The exploration in which they were engaged was not one for the advancement of material aims or the ambition of governments to enlarge their dominions — it was one solely in the interest of science, to widen the domaiu of know- ledge, and help us to better know the laws which affect the conditions of life and growth on this planet, as well as to throw light, if possible, on that great field of research, so largely .speculative, in which we are seeking to find out something of the universe. It was not until June 22, 1884, a little more than two years and ten months after the party had been left on the shore.s of Lady Franklin iBay, that seven of them, the onl)' living members of the original band, were relieved of their long vigil by the ap- pearance of the vessels of the government expedition tinder ■Commander Schley. Seventeen of the others had died of starvation, one was drowned while sealing to obtain food, and of those found alive one died subsequently from the amputation of limbs made necesf-ary by frost bite, so that only sLx of the original twenty-five remained alive to reach home again. The story of the expedition, the plans of the scientiQc bodies and Arctic explorers which led up to it — in con- nection with several other observation posts arotind the ipole — as well as the futile efforts of 1882 and 1883 to reach and relieve the colony at Lady Franklin Lay, have often been told. It was the understanding when the station was established — subject to the discretion of Lieu- tenant Greely, as circumstances might affect the situation — that if government relief did not reach the station during the summer of 1882, the party would endeavour to work its way southward in the summer of 1883 as far as Cape •Sabine, or make its quarters on the west coast as far south as might be practicable, and yet within the possibility of ■being reached by a relief expedition, but that the route would be on or along the we.st coast, and not on the Green- and side. In accordance with this idea Lieutenant Greely abandoned his quarters at Fort Conger, on Lady Franklin Bay, August 9, 1883, and reached Baird Inlet, near Cape Sabine, September 29, with the entire party wel up to that time. Great difficulty was experienced in getting to that point, with the instruments and records of observa- tions, and as large a supply of provisions as it was possible 4o convey. He was obliged to abandon all his boats, and was adrift for thirty days on the ice in Smith's Sound, the party finally making its way across an almost impass- able field of ice hummocks to a landing just north of Cape Sabine, where a permanent camp was established October 21. Here the party found that a very insufficient supply of provisions had been left, while some of tliose thus obtained had been left by Sir George Nares as long back as 1875, and were, of course, much damajied. It was known that supplies liad been left on Littleton's Island, almost opposite Cape Sabine, on the east side of Smith's Snund ; but the channel did not close all the winter on account of violent .gales and strong currents, and thpre was no means of reach- ing the food that was so near. The party was immediately put on short rations, but on May 11, 188-t, the last regular tfood was issued. After this the men were forced to live on boiled sealskin strips from their sealskin clothing, lichens, Hnd shrimps, game having failed, de.'spite daily hunting, from ■early in February. One had died in January, 1884 — the first death of the party — then five died in April, four in May, and seven in June, up to the 22nd, when the rescue was made, and when, according to Commander Schley, "forty-eight hours' delay in reaching them would have been fatal to all." Too high praise cannot be accorded to Commander Schley for the energy with which he pushed north so early in the season, fighting his way almost inch by inch through the ice : but it will be remembered with a feeling of sadness, if not of severe reprobation, that three Lnited States vessels, tb>- Yantic, the Pi-oteus, and the Npplv.ne, had visited the near locality of Greely's fatal camping - ground, during the summers of 1882 and 1883, with ample provisions, and came home again without leaving there the supplies that would have prevented these men from starving. It is too early to say what will be the probable value of the information obtained by this expedition. Up to the fall of 1883 its success seems to have been all that could have been desired by its promoters, and in the journey southward copies were brought of meteorological, tidal, astronomical, magnetic, pendulum, and other observations, although some photographs, Esquimaux relics, and other thing-i were necessarily left behind. It is probable, how- ever, that Lieut. Greely made all the observations required liy the International Conference at Hamburg, under whose directions the various circumpolar stations were established, and that substantially all such records have been saved. The distinguishing work of the expedition — that which will (lerhaps give it most fame — is thus announced by Lieut. Greely : " For the first time in three centuries England yields the honor of the furthest north," which had pre- viously been 83° 20', but was marked at 83' 24' by Lieut. Lock wood, of the Greely expedition, on May 13, 1882. The point of observation was named Lockwood Islnnd, where, " from an elevation of 2,000 feet, they saw no land north or north-west." To the east and north-east of Lady Frank- lin Bay the party undoubtedly made the best survey yet Aug. 15, 1884.] ♦ KNOWLEDGE ♦ 141 accomplished of northern Greenland, and, by observation of what seemed to be a distant headhiiid, located it as Cape Robert Lincoln, in latitude 83" 35', longitude 3S° west of Greenwich. At B, in our map, is shown Lookwood Island, the highest northern latitude yet reached, and from whence the obser- vation was made, while A marks the highest point attained by Commander Markham, the most successful British ex- plorer in 1870. In a subsequent endeavour to go still farther north, the party was turned back by open water, and, as Greely's report says, " barely escaped drifting into the Polar Ocean." There are many other newly-named places, and some material changes will have to be made in the maps of regions hitherto incorrectly laid out, along the west shore of Kane Basin and Kennedy Channel, and in the configu- ration of Grinuell Land, and the north shores of Grant Land and Greenland. Arctic geography will thus, doubt- less, be greatly amended, but whether the results attained will prove sufficient compensation for the loss of life of the brave men who were sacrificed is a query which many people will think most unsatisfactorily answered. — tScientific American. JlcblfUiS* SOME BOOKS ON OUR TABLE. An Introduction to Mental Philosophij, on the Inductive Method. By J. D. MoRELL, A.M., LL.D. (London: W". Stewart &■ Co.) As an introduction to the study of psycho- logy, at once scientific and popular, it would be difficult to find a work better adapted to its avowed purpose than that whose title heads this notice. While omitting nothing essential to a complete theory of the nature and modes of action of the human mind, it is yet commeudably free from that redundance of verbiage which unfortunately dis- tinguishes so mauy works on mental science ; though while as succinct as need be, it never degenerates into baldness, or slurs over a difficulty for want of detail in the argu- ment adduced to meet it. Dr. Morel 1 begins ab initio with the primordial forms of mental activity, and, proceeding through the nature and development of perception, and sub- sequently of ideas, traces the logical processes of the human mind from the latter. In subsequent divisions of his work he necessarily deals with human reason, the develop- ment of the will, and the feelings generally ; concluding ■with an appendix of very numerous examination papers in mental and moral science set for degrees in the London University. The reader who has been taught to regard everything in the shape of metaphysical or psychological disquisition as essentially dreary will undeceive himself very agreeably by the perusal of Dr. Morell's book ; while the student more familiar with mental science may read such chapters as those on belief and on the freedom of the will by DO means without profit. The work has one solitary defect, which we trust to see supplied in the next edition — it has no index. Manual of the Mosses of H'orth America. By Leo Lesquereux and Thos. P. James. (London : Triibner & Co. 1884.) — To every practical bryologist this wonderful specimen of patient and enduring labour of Messrs. Lesque- reux and James will be welcome, containing as it does a detailed description of something like nine hundred species of the mosses found on the American continent ; iu fact, presenting a practically exhaustive account of every one so far known there. It is illustrated with six beautiful plates, crowded with figures, illustrating the genera ; and | must be indispensable to every one interested in the lowly type of vegetable organisms with which it so ably deals. How to Foretell the Weather ivitli the Pocket /Spectroscope. By F. W. CoRV. (London : Chatto & Windus. 188-1.)— In or about the year 1872 Professor Piazzi Smyth, the Scottish Astronomer Royal, discovered that when moisture was present in the air a band or shading appeared in the spectrum of the light of the sky, on the less refrangible side cf the well-known D, or sodium, lines. The result of a series of observations induced him to believe that the spectroscope might thus be employed as a hygrometer, or, speaking more rigidly, a hygroscope, to foretell the advent of rain ; and, impressed with this idea, he published his discovery to the world. The matter was taken up in England by Mr. Rand-Capron and a few others, but very considerable difference of opinion seems to have prevailed as to the value of the method ; and, during the autumn of 1882, the columns of the Times were the scene of a l)retty lively conflict of opinion on this subject. Mr. Cory, however, appears to have given the spectroscope a pretty fair trial as a means of forecasting rain, and claims to have been quite successful in his vaticinations. To all who wish to follow his footsteps, his little book may be com- mended ; as he gives the plainest possible directions for the use of the instrument to predict rain, illustrated in a way which renders his descriptions almost equivalent to personal instruction. The method is worth a trial, at any rate. € ill tonal »gci£(£(ip. The devotees of the science or art, or whatever it is, of " Philately " may be interested to learn that up to the end of the year 1883 two hundred and three countries, states, ic, and twelve private companies had issued adhesive postage-stamps. Of these, sixty-nine have also issued envelopes, and one hundred and seven, post-cards. Between 1810 and Dec. 31, 1860, 2,400 stamps of sorts were issued. From 1861 to December, 1870, sixty-six new countries were added, and the stamps rose in number to about 6,400, an increase of 4,000 in ten years. In the next decade forty- nine new countries were added to the list, and another 4,000 was added to the number of adhesive stamps. Finally, the number of stamps which, up to Dec. 31, 1880, was about 10,400, had advanced to about 12,000 in the succeeding three years, or at the rate of more than 500 a year ; so that if the same rate of progression should con- tinue, by December, 1890, 16,000 varieties of postage-stamp will be in existence. When I read all this in the pages of Messrs. Alfred Smith the efficient and indispensable means of their production, is a very very very different thing to the allegation that it is the feelings and affections themselves. — Ed.~1 WHAT ALES IT ? [13G3] — Bottled ale or beer ^r^ll-vp when poured into a tumbler gives more than enough of froth. A small piece of cheese in the glass checks immediatehj the froth. — Why 'i or How ? — Boeeas. LETTERS RECEIVED AND SHORT ANSWERS. .1. T. RouTiEDGE. I have not read Professor Balfovir Stewart'." " Visible Universe," in the Contemporary Revitu-, and am hence ignorant as to the nature of the arguments by which he sustains his allegations. If, as you seem to imply, he simply asserts that the waste — or seeming waste — of Energy .n the Universe affords proof of the spiritual production of that Universe, than — be he "a person of authority in the scientific world" or not — he is talking nonsense. Jf we are going to admit the teleological argument at all into the discussion of any fact of nature, waste is evidence of absence of design and perfunctory workmanship ; certainly not of prevision and adaptation of means to ends. — F. M. Billings. Received. I have nothing to add to my former reply. Mr. Clissold regards Swedenborg as inspired. I am absolutely certain he was insane. We cannot argue on common ground. — Beccabuxga kindly sends the address of the Cremation Society for the benefit of "Kenius" (p. 101). Com- munications should be addressed to W. Eassie, Esq., C.E., 11, Argyle-street, Regent-street, London, W. My correspondent goes on to complain of the non-appearance of articles on Evolution in Knowledge. I fancied myself that Mr. Grant Allen's interesting articles, one and all, illustrated different phases of Evolution, but I suppose that I (in common with many thousands of readers) was mistaken. — J. F. 0. takes exception to a statement on p. 7G with reference to imprisonment for debt, and points out how the most thoroughly dishonest debtors can, and do, under the existing law, snap their fingers at their creditors. In fact, that, so far from the unfortunate debtor being treated as a criminal, the scoundrel almost systematically escapes. — H. Siggers. Everything depends upon the branch of astronomy to which you propose to devote yoar- self. Ball's is, in every respect, an excellent book. — Major Gas- lOYXE. The sole official statement of the results obtained from the last Transit of Venns which has been so far issued, is that of the Belgian ones by M. Houzeau, in Tome V. of the " Annales de I'Obsenatoire Royal de Bruxelles" for 1884. I need scarcely say that no English results have been yet published. May 1 invite yotir attention to the concluding sentence (in capital letters) of those which head the Correspondence column.— H. P. S. Not easy to introduce into a scientific journal. — M. J. C, having apparently heard of Fon- tenelle's treatise for the first time through these columns, took it up at random from among a lot of old books recently found in a cupboard at a friend's house. — J. Pax.max. You will see from p. 103 that Mr. Proctor had started for America at the date for which your invitation was issued. — Wm. Hakrisox. Received with thanks. — Ignoramus. 1. There are three primary colours, red, green, and violet. 2. A com])lementary colour is that which when mixed with the one to which it is complementary gives white light. Blue and yellow are complementai-y colours, so are red and greenish- blue, orange and what is called cyan-blue, and greenish-yellow and violet. The complementary colour to pure green is purple. Note especially that I am speaking of light of different colours, not of pigments. The blue and yellow of our paint-boxes, for example. Aug. 15, 1884.] ♦ KNOWLEDGE ♦ 145 form green, and not white at all. 3. Flints are ajrirrepations of silica round shells, sponges, cchinites, &e., which died and sank to the bottom of the ocean which deposited the chalk. There were thermal springs then as now, and you know that hot water will mi x = ~ y = = ' m^ — wij ■ /*io — 7>ij Since both equations are satisfied when we give to •: and 1/ the above values, it follows that the point which has these coordinates is a point on both lines, — that is, is the point in which the two linos intersect. If 7?ij = m, the values above obtained for .c and y are indefinitely great. This is the analytical expression of the relation that parallel lines never meet. If the equations of the lines be given in the form AiJ +B, ly 4-Ci = 0 (i) and A^i-i-Bjy-HC- = 0 (ii) we obtain B,C.,-B„Ci A,Co-A„C, " = A,B,-A,Bi' """^ y = A,B,-A.B., 65. Prop. — To determine the condition that three straight lines ichose equations are given may pass through a point. Let the equations of the three lines be !/ = mja;-pC] (i), y = nuj> + c.2 (ii), and y = ni3T-i-i-3 (iii). Then the x co-ordinate of the point of intersection of (i) and (ii) ' ^ and the a;-co-ordinate of the point of intersection of (i) iHj — nil, and (iii) is — ! — Hence, if (i) (ii) and (iii) meet at the same point we must clearly have Ci — C.1 Ci-Cj (0 (ii) tiv; — nti 7713— mi that is <^i™3 ~ '^a'"! + '^znu — c^m-^ + c^m^ — Ciiii.. =0 (iv) In fact (iv) is the algebraical condition that the three equations (i) (ii) and (iii) may be equivalent to only two independent equations. We know from algebra that if the three equations (i) (ii) (iii) are equivalent to only two independent equations, that is if con- dition (iv) hold, then when (i) (ii) and (iii) are multiplied respec- tively by the quantities c^m^ — c^m.,, C3"»i — Ciwij, and c,n!.;— c.,m,, and added together, both sides of the resulting equation vanish iden- tically. Hence we obtain the following rule, which is frequently useful in practice. If three equations representing straight lines can be multiplied by such quantities that the sum of the resulting equations expresses identical equality, the straight lines represented by the three equations all pass through a single point. 66. Prop. — To determine the form of the equation to a straight line passing through the intersection of two given straight lines. If these equations to the two straight lines are A,! +Biy-HCi = 0 A,vr + B.,y-HC2=0 We may proceed to a full-length solution as follows : — Solving (i) and (ii) we get for the point of intersection BiC.-B.,C, ^ A.,C,-A,C., ^=aib:-a:b, ^"'^ ^==a;b,-a,b; .'. by the equation to a straight line passing through the point of intersection of (i) and (ii) is of the form L a,b.-a.BiJ L AiB»-a.,bJ *■ ' or (AiB2-A.,Bi)(Ai-hBt/)-f(BB.,-AA.,)C,-i-(AA,-BB,) C;=0 (iv) Now if we multiply (i) by (B B.-A Ao) and (ii) by (A Ai-BBJ and add, we get for the co-eflicient of x A,B B,,-A A,A.-(- A AiA;-A;B Bi = B(AiB;-A.,Bi) and for the co-eflicient of v BB,B.-AA,B, -hAAiB.,-BBiB.: = A(AiB.,-A;B,) or for the resulting equation the form (iv). We might simply have proceeded thus A,j! + B,!/-iCi = 0 (1) A»3;4Bov-hCo = 0 (2) any equation of the form Z(A,.'' -I- Bit/ -1- Ci) + m(A.;7- -I- B;!/ + C-) =0 (3) which is also obvious since whatever values of t and y satisfy (1) and (2) must also satisfy (3). It is also obvious that every equation to a line passing through the intersection of (1) and (2) can be put in the form 3, seeing that the ratio B : A of the preceding article is the tangent of the angle made by a straight line through (i) (ii) with the axis of x, and as we have seen to give B and A Bnitable values, all we require is that the following equations shall hold. i = EB;-AA, and »i = AAi — BB, The method of the preceding article leads directly to the very valuable method of treating certain problems on the straight line called the Method of Abridged Notation. I do not here dwell upon it because any one who is likely to require much information on the subject would go to treatises where the methods of co-ordinate geometry are more fully dealt with than they can be here. 146 ♦ KNO\VLEDGE ♦ [Aug. 15, 1884. (2^nr €f)t^^ Column* By Mephisto. PEOBLEJI, Xo. 123. (Selected.) Black. Sk. ■White . White to play and mate in two moves. SOLUTIONS. Problem Xo. 120, p. 102, 1. QtoKtS 1. B toK.5 2. Q to B sq. mate 1. -.0 Kt 2. Q to B5 mate. No. 121. 1. Q to Q3 and mate accordingly. E.\Di.N(; p. 102. 1. Rto K8 (cli) 1. RxB 2. Q to Kt8 (oh) 2. K X Q 3. P X R mate 3. PxE(Q) (ch) and wins K2 ENDING FROM ACTUAL PLAY. Blick. rf mi WniTE, 1. B X Kt 2. B X P (ch) 3. Kt to B5 (ch) 4. R to B6 (ch) 5. B to Q3 (ch) 6. P X Q (ch) 7. B to Q2 (ch) 8. R to R sq. (ch) 9. B X R and White won 1. RxQ 2. K to Q2 3. K to Q3 4. K X Kt 5. Q to Q5 6. K to Kt5 7. KxP 8. K to Kt4 GAME AT ODDS OF TWO KNIGHTS. Wo publish the following amusing game as a cnrious example oi of odds giving. Remove the two White Knights. 1. P to K4 P to K4 2. P to Q4 P X P 3. B to B4 B to B4 4. P to QB3 P X P 5. Castles PxP 6. B X P Kt to KB3 7. P to K5 P to Q4 This move is often ])!ayed, but not when the B is on Kt2 ; ol course, receiving the odds, Black ventured something to exchange pieces. 8. P X Kt P X B 9. R to K sq. (ch) B to K.3 10. P X P R to Kt sq. 11. Q to R5 AVhite threatens R x B, also Q x B and (.} x RP; the latter move especially would be dangerous. BxP (ch) Black was bound to lose a piece. K to y2 would have been best, but BxP looked feasible. 12. K X B Q to Q7 (ch) 13. K to Kt sq. An artful move QxB Besides this likely-looking move, Black could have played K to K2, but White would maintain his attack. 14. R X B (ch) K to Q sq. 15. R to Q sq. (ch) K to B sq. It Kt to Q2 then R x Kt (ch), and mates in fonr moves. 16. R to K8 (ch) R X R 17. Q to B5 (ch) E to K3 18. P to Kt8(R) (ch) and mate. ANSWERS TO CORRESPONDENTS. »*» Please address Chess Editor. Joseph Farrar. — In the article on the Roy Lopez in Kxowledge, p. 490, Black's move ought to read 9. Kt to K3. G. Thompson, T. B. S., Chas. T. Wilbraham, M. T. Hooton, C. T. G.— In I'roblem No. 122, if 1. Q to K2, B to B3, and there is no mate. Correct solutions received. — Problem p. 80, H. A. X. ; Xo. 120, 121, A. W. Overton, M. T. Hooton, G. Thompson. Contents oi' No. 145. PAGB The MoralitT of Happiness. By Thomas Foster 103 The Sea Horizon. ByR. A. Proctor 104 The Sense of Taste. By Grant Allen 105 The Origin of Silk 106 Dreams. VI. By Edward Clodd,.. 107 The Earth's Shape and Motions : In- troduction. By R. A. Proctor ... 108 The Electro-Magnet. By W. Slingo. 109 The Capture Theory of Comets. By R. A. Proctor Ill Mind in Man and Brute. By G. J. Romanes 112 Natural Gas Fuel at Pittsburg 113 PAGE The Tarantula of Southern Cali- fornia. {Illug.) 114 Attitudes after Death. (lUni.) By 0. E. Brown-Sequard 115 Other Worlds than Ours. By M. de Fontenelle. With Notes by Richard A. Proctor 117 The International Health Exhibi- tion. XI. [niut.) llg Editorial Gossip 121 Our Paradox Column 121 Correspondence 122 Our Mathematical ColuKm 12.'} Our Chess Column 124 SPECIAL NOTICE, Part XXXIII. (July, 1884), now ready, price Is., post-free. la. 3ii. Volume v., comprising the numbers published from JanQary to Jane, 18S4, now ready, price 99., including parcels postage, Os. 6d. Binding Cases for all the Volumes published are to be had, price* 29. including parcel postage, 2b, 3d. Subscribers' numbers bound (incloding title, index, and case) for Se. Volume ; including return journey per parcels post, Ss. 6d. Kemittances should in every case accompany parcels for binding. each, each TERMS OF SUBSCRIPTIOF. The terms of Annual Subscription to the weekly numbers of Kxowi-BrGE are as follows : — s. d. To any address in the United Kingdom 35 2 To the Continent, Australia, New ZeaJand, South Africa, & Canada 17 4 To the United States of America $4.25 or 17 4 To the East Indies. China, Sac. (rm Brindisi) 19 6 All subscriptions are payable in advance. OFFICE : 74-76, GREAT QUEEX STREET, LONDON, W.C. Aug. 22, 188-t.] ♦ KNOWLEDGE 147 AN ILLUSTRATED ~ MAGAZINE OF SCIENCE J^^YWORDED-EXACTLYDESjl^ LONDON: FRIDAY, AUG. 22, 1884. Contents op No. 147. PAGE Sunflowers. By Grant Allen 147 A Stranfje Disorder 148 Paradoxistsin America. By Kiehard A. Proctor 148 Tncycles in 18S4 : Small v. Large Wheels and Two-Speed Gearings. By John Browning 119 The Earth's Shape and Motions : II. The Diurnal Motion of the Stars. {lUu^.) By R. A. Proctor l.=;o Electro-plating. X. By W. Slineo 151 Dreams. VII. Bv Edward Clodd l.'>:; The Workshop at "Home. {IUu».) By a Working Man 153 The Greely Expedition. By Andrew McPherson 156 167 A Xew Volcano The WfRtinghoase Brake. {lUut.) By " Trevilhick " 157 Other Worlds than Ours. By M. de Fontenelle. With Notes by Richard A. Proctor 160 International Health Exhibition, XIII. [IUuk) 161 British Seaside Resorts. III. By Percy Russell 162 Editorial Gossip IfH Mi&cellanea 165 Correspondence -. The Sense of Taste — Perspective — Wearing the Dead — A Coincidence, &c 166 Our ChesB Column 168 SUNFLOWERS. By Grant Allex. IT is well to choose a text which everybody can easily verify for hiaiself; and as hardly a house is now without a sunflower, I may as well choose that fashionable blossom as the subject for this morning's discourse. Take down one from the drawing-room mantel-shelf, and you will be able to follow for yourselves what I have to say to you. You had better choose a blossom in which the central florets have not yet begun to open, as you will then be able to fiud flowers in every stage of development. The sunflower, I need hardly say, is a member of the composite family ; and each head is not, of course, a single separate flower, but a whole collection of hundreds of golden bells. If you pull out one of these, you will find it consists of a yellow tubular flower, five-lobed above, and bulging broadly at its base. This flower surmounts a large seed, or rather fruit, with one or two wings at its top, which are all that now remain of the original calyx. In the centre of the compound flower-head you will find a mass of unopened flower-buds, each one covered and protected by its own scaly bract. These bracts are the remnants of the little leaves which once grew under each blossom when the ancestors of the sunflower still possessed long spikes of flowers. But in course of time the compo- sites learnt to flatten out their spike into a broad, disc like head. Still, however, the bracts, in a much-dwarfed form, remained to separate the individual little bells ; and in some cases, as in the sunflower, they have been utilised for a new purpose — namely, to protect the unopened flower- buds from insects which might otherwise eat them, or lay their eggs upon them. Many composites still retain the bracts ; in others, and often in closely allied forms, they are wanting, having been gradually lost by disuse. There are none in the daisy or the dandelion. Beyond this central region, where the buds are yet unopened, you will find two or three rows of newly -opened flowers, with all their lobes displayed, and wi'h the little black stamens standing up conspicuously in their midst. These florets are in their first or male stage. If you open carefully with a needle the tube formed by the united stamens, you will find inside the little style, with its two branches still pressed closely together. The bee hovering over these florets in the first state, dusts himself over viitli pollen from the yellow tips of the atithers. This he after- wards carries away to fertilise the other florets. Outside the rows of flowers in the first male state we come to some other and more crowded rows, which have reached the second or female cone ition. In them the style has grown longer, so as to overtop the now withered stamens. At the same time, its branches have opened out- ward, and now curl over gracefully, so as to expose their sensitive surfaces. If you look closely you can see, even with the naked eye, grains of pollen cHnging to their surface. Outside these female florets again come a few rows of fully-fertilised and over-blown blossoms, which are crowded together by pressure from within, and of which the bees and other visitors hardly take th^ slightest notice. Lastly of all, on the very outside of the great compound flower-head, we reach the big expanded golden ray florets, which are, in fact, neuter members of this organised floral community. Their business is to make as large a display as possible, and so to attract insects to the fertile florets iu the centre. If you pull out one of them carefully, you will find that it is tubular in its lower portion, but that the broad upper p.irt is formed by the splitting open of the tube on the inner side. One may still observe faint traces of the original five hibes even in these very enlarged and distorted florets, e.^pecially at the tip, where they are often notched or divided. In some composites the expanded ray florets still keep their styles ; but in the sunflower they have become wholly abortive. We may thus compare the compound head in some respects with a hive of bees con- taining females, males, and neuters. It will be observed that the sunflower opens from with- out inward, and the bee who approaches it visits it in the same order. Thus he comes in contact first with the florets in the female stage on the outside, and dusts them over with pollen which he brought from the last head. He then proceeds to the inner rows of male florets, from which he unconsciou^^ly collects pollen to carry to some neigh- bouring plant If either the sunflower or the bee reversed this proceeding, the result would be that the florets would get fertilised with pollen from their own brother flowei-s, the least desirable form of cross-fertilisation ; but here, as elsewhere, natural selection has adapted the habits of the plant to those of its regular visitors, and has thus secured the best form of impregnation. Bees are jiarticularly fond of the sunflower, and obtain from it large quantities both of pollen and honey. The fruit of the sunflower has no feathery top or pappus to float it away like the dandelion and thistledown. It is too large and hfavily stored with rich food-stufTs for the young plant to admit of that form of dispersion. So the calyx, instead of being transformed into a pappus, as in most other composites, here remains simple and cuplike. But the seed profits in the end by its richness in oil and other valuable stores, for the sunflower plant is thereby enabled to get that splendid start in life which makes it into one of the tallest and stoutest annuals of temperate climates. Very few species attain so immense a height in a single year. Probably, too, no other annual, except Indian corn, produces so large a number of so richly-stored seeds. It is this provision on the part of the mother plant which allows them to reach so great a stature during a sin^'le short summer. 148 KNOWLEDGE ♦ [Aug. 22, 1884. A STRANGE DISORDER. AVERY curious disorder of the nervous system is de- scribed in the Revue Scientifique of August, being taken from the Archives de Neurologie for Api-il of this year. It appears that, in the U.S. State of Maine there are some persons in apparent health except so far as relates to nervous excitability, which is excessive. The least irri- tation causes them to jump. They also feel compelled to execute anything they are ordered to do, and they repeat the command in a loud voice. Dr. Beard reports that one "jumper," as they are called, was sitting on a chair cutting tobacco. He went up to him, struck him suddenly on the shoulder, and said, " Throw it away ! " He repeated the words in a voice of terror, and threw his knife, so that it stuck in a door opposite to him. Two other jumpers struck themselves violently on being told to do it. This disorder appears to be hereditary. In one family Dr. Beard found the father, his son, and two little girls of four and seven affected by it ; and in another case three brothers were its victims. A similar complaint occurs in the Malay region of Asia, and it has been observed amongst various races, Tamils, Bengalese, Sikhs, and Nubians. The Malays call the patient a latah, a word of wide significance, applied to various degrees of nervous excitability. Mr. O'Brien states that when travelling in the Malay Peninsula he had as a servant a young Malay whom his comrades called a latah, though his conduct and conversation indicated nothing irrational. Four-and-twenty hours elapsed before his peculiarity was displayed. A signal fuse was then fired by way of rejoicing, and the doctor was about to ignite another when the young man pushed him violently on one side, seized the torch, lit the fuse, and fell to the ground face downwards, uttering a strange cry. The next day he seemed all right, but when the doctor waved his hand as an adieu on leaving the shore, he imitated the movements with frenzy. He also imitated him as he whistled a European tune. On another occasion the doctor had introduced to him an old and highly respectable woman, with whom he talked for ten minutes without noticing anything abnormal. All of a sudden the person who brought her took off his coat, upon which she began to undress, and would soon have been quite naked, if he had not stopped her. She was furious against the man who incited her to this indecency, and while she was taking off her clothes, abused him as " an abandoned pig," and wanted him killed. Another case ended tragically. The cook of a steamer was latah, and one day was nursing a child, when a sailor came near him with a billet of wood in his arms. He rolled the wood on the top of an awning, and loosening it let the wood fall. The cook did the same with the child, and killed it. At Singapore another latah, seeing his mistress tear a letter and throw the pieces out of window, did the same with a bundle of new clothes he was carrying. The disorder is not confined to warm climates. It is known in Siberia, and a case is mentioned of the pilot of a ship on the Ussar who could not refrain from imitating actions or noises made by the passengers to try him. The captain had a fall while clapping his hands, whereupon the pilot clapped his, and fell in the same way. The Russians call the complaint miryachil, and it is said to be common near Yakutsk in severe winters. S. American Telegraphy. — There were 42,917 telegraph offices in the United States in 1882. The number of telegrams forwarded during the year was 40,581,1/7. PARADOXISTS IN AMERICA. By Richakd A. Proctor. ONE of the most remarkable features of American newspapers is the attention directed in them to men of the paradoxical turn of mind. Our Hampdens, Paral- laxes, and Newton Crosslands ought to cross the Atlantic if they wish to receive the amount of attention which doubtless they consider their due. At Montreal lately there died a man named Vennor, who had posed as a weather prophet, with the usual amount of success, for several years. His predictions were quoted over the length and breadth of the United States, as well as of British America, and he was regarded (if we can judge from news- paper comments) as a veritable man of science by most Americans. The Montreal Daily Witness paid Montreal the left-handed compliment of describing Vennor as " her most celebrated citizen." In Kentucky, a few years ago, there was another charlatan, by the name of Professor Tice, who claimed similarly to be a weather-prophet, and showed an even more marked ignorance of real science in every line of his writing. His predictions were for a long time regarded with approval, although they showed no more than the usual proportion of successes to failures. He was successfid as a lecturer, getting fees, in fact, which an English science-teacher of the soundest kind would certainly not command in the old country, nor secure in America unless he had done something which had attracted special attention there. After a while, " Professor " Tice found that his failures were becoming rather too prominent a feature in newspaper notices; so he made a bold stroke for public favour. He invented a planet to account for his failures — an intra- Mercurial planet, of course. He described how, observing the sun one September day, he saw a round spot, which at first he supposed to be only an ordinary sun-spot ; but, seeing it was moving across the sun's face, he concluded it must be Mercury. (He had no idea how thoroughly he was thus exposing his ignorance — not, indeed, to the average American paragraphist — but to every one acquainted with the elements of that science in which he pre- tended to be most profound ; a transit of Mercury in September would be as surprising a phenomenon to an astronomer as an eclipse of a crescent moon.) Finding after reference to an almanac that it was not Mercury, he concluded it must be Vulcan, the intra-Mercurial planet discovered by Lescarbault, if that veracious observer's account is to be believed. This idea being conceived, Tice was at once able — such is the force of genius — to assign the true period of Vulcan, so as to com- bine together Lescarbault's observation, his own, and all those failures of his which wanted a new planet for their interpretation. So ingeniously was this done, that it appeared, on examining " Professor " Tice's own most precious data, that when he saw Vulcan, that planet must have been seen through the sun. This was pointed out in a Louisville magazine, edited by a gentleman much less widely known throughout America than " Professor" Tice, but having the advantage of him in knowing a good deal about science, whereof the professor knew nothing. We heard less about Tice after that, though, doubtless, millions still put faith in him. And now, another of these charlatans has distinguished himself in such a way that American papers have spoken of him as one might speak of a new Newton, though every line he has written shows him to be ignorant of the veriest elements of science. Like Tice, this man — who rejoices in the name of Wiggins, and honours Ottawa by his presence Aug. 22, 1884.] ♦ KNOWLEDGE ♦ 149 — has undertaken to predict weather. He terrifies all the unwiser folks iu British America and the United States, and not a few who by no means regarded themselves as idiots, by announcing some year and a half since the destruction of every ship on the ocean by a mighty storm, which did not come when he did call for it. But latterly even newspajier paragraphists have noted that Mr. Wiggins's predictions have been unfortu- nate, to say the least. So, as Tice invented a new planet, and probably Wiggins thought another new planet would nol be welcomed with enthusiasm, the weather prophet of Ottawa invented a new moon, not where M. Petit, of ^Marseilles, thought that another moon may perchance be travelling, to wit, nearer than the known moon, and lost nearly always in the earth '.s shadow, but far beyond the moon, and invisible because it has no atmosphere ! I think the readers of this paper would hardly credit me if I were to tell them of all the silly things Mr. Wiggius said in the preposterous paper in which he announced the discovery of a second moon ; but perhaps the most ludicrous notion was that the atmosphere of a planet plays an important part in enabling the planet to reflect sunlight, so that an orb without an atmosphere ■would not be visible at all. Another absurdity was the statement that Newton could not explain the perturbations of the moon's movements ; but that with this outer moon everything could be fully explained — the inanity of which assertion may not be obvious to others, but is simply stupendous even to the humblest students of the lunar theory. It is not, however, the absurd nature of this man's ideas and reasoning that I care to dwell upon. The ways of paradoxers are tolerably well known, and Mr. Wiggins is neither better nor worse than the rest of them. What is really interesting, and I fear significant, is that in many American newspapers the nonsense of a Wiggins, a Tice, or a Vennor, is discussed as gravely as the work of a Draper, a Young, a Langley, or a Newcomb. In a country distinguished by the labours of such men as these, and a host of other steady workers in the fields of science — from men who rank with the best ia Europe down to those whom form indeed the rank and file, but are nevertheless sound scientific students — the average newspaper paragraphist is so ignorant that he speaks of the inanities of men who, in the very nature of things, must either be knaves or fools, as though he were dealing with the thoughts of men of sense. They seem unaware of the fact that the mistakes of a Young or a Newcomb cannot be brought into comparison with the notions of even the least foolish (or knavish) among the paradoxers. A stranger taking up an American newspaper in which a man like Vennor is spoken of as " the most celebrated citizen of Montreal," or a Tice as " our distinguished weather prophet," in which a Wiggins, as recently in a paper published in Missouri, figures among the great men of the day, would never suspect, what is in reality the case, that America possesses mathematicians, astronomers, geologists, meteorologists, and chemists, who yield in skill and in the quality of their work to none in Europe. — Kevicastle Chronicle. An attempt ia being made to obtain subscriptions for enlarging the buildings in Whitechapel of the Working Lads' Institute. These are to comprise Heading, Refreshment, and Class Rooms, Lecture Hall, Technical School, and Swimming Bath. All inte- rested iu the social and intellectual advancement of the working classes, who may feel the desirability of providing such counter attractions as are indicated above to street-comer betting and sotting in the public-house, can send their subscriptions to the treasurer, F. A. Bevan, Esq., 54, Lombard-street, B.C., or to the hon. sec, Henry Hill, Esq., jnn., 38, Bow-lane, E.G. TRICYCLES IN 1884. By John Browning. (Chnirman of the London Tricycle Club.) SMALL VERSUS LARGE WHEELS AND TWO-SPEED GEARINGS. THOUGH I have for some months written but little for Knowledge, I have been riding tricycles and experi- menting with them continuously. During this season, I have ridden only machines made to my own specifications. The whole of my machines now have wheels either 30 in. or 38 in. in diameter. Here my experiments in reducing the size of the wheels must stop, for if the wheels were reduced in diameter only two or three inches more, my legs would not clear the axles, nor would my pedals clear the ground. But, as far as my experience goes, I have found the reduction of my wheels to this extent an unmixed advan- tage. The machines are lighter, they are stronger, they are more portable, and they travel quicker or with greater ease. To my thinking, only one point worth considering has been urged against the use of small wheels — that is, that their employment would greatly increase vibration, particularly when they were highly geared. I have one machine geared up to 48 in., and another to 52 in. I can- not find that the vibration of these machines is greater than other machines I have been riding, which have wheels of -10 in. and 48 in. diameter, level-geared. Mr. S. Salmon, who is deservedly considered an autho- rity on tricycles, has had a machine built this year by Hirst, of Croydon, of the Coventry Rotary type, with a 38-in. driving-wheel, which weighs less than one pound to the inch. It is geared up to 57 inches, yet Mr. Salmon assures me that after three months' experience he prefers it to any other machine he has ridden. From this it is e\'ident that small wheels can be adopted with advantage, even with high gearings. The gi-eat obstacle to their introduction is the fact that manufacturers whose patterns have been designed for large- wheeled machines, and who have often a considerable stock of parts of machines and of large wheels by them, dissuade customers from having them, and frequently refuse to make them. Also in the case of two-speed gearings, manufacturers have made the high speed agree with the diameter of the driving-wheels, and obtained the low speed by gearing down ; thus, a machine with 50-inch wheels will run as 50, or when geared down, as 35 inches. If, instead of this, a machine were made with wheels say 42 inches diameter, geared up to 50 inches and down to 35 inches, it would be stronger, faster, and about 20 lb. lighter. The Crypto-Dynamic two-speed gearing has not, I believe, had such a success as was anticipated for it, and I notice that the patentees particularly recommended the use of large-wheeled machines. By doing so, I consider they have not given their invention a fair chance, but have stood in their own light, as, by adding weight in the form of a two-speed gearing, and also by increasing the weight of the machine by making it with large wheels, they neutralised the advantage of the gearing ; in plain words, what they gave with one hand they took away with the other. This point I am urging is of great importance just now, as so many manufacturers are bringing out two-speed gearings. Unless some maker of more originality than the rest will depart from the beaten track, we shall have this new and invaluable improvement in machines brought for- ward in an unsatisfactory form, and tested at a great dis- 150 ♦ KNOWLEDGE ♦ [Ado. 22, 1884. advantage. The new two-speed, central-geared Sparkbrook is a well-planned and well-made machine, half spoilt by being constructed on the plan I have described. The Coventry Machinists have, however, introduced a new and very original two-speed machine, in which speed is obtained by gearing up above the size of the wheels, which is the correct principle. It would be unfair for me to leave this subject without saying that Messrs. Humber, Marriott, & Co., Singer it Co., and Starley & Sutton, make most of their mnohines with wheels from 40 in. to 44 in. diameter, and gear them up according to the requirements of their customers. A very noteworthy fact iu connection with the adoption of small wheels is the wonderful performance of the various safety bicycles, chiefly the Facile, the Suu and Planet, and the Kangaroo. Now, these machines have wheels ranging from 36 in. to 42 in. in diameter, yet their performances in point of speed and of long distances will bear favourable comparison with those of bicycles of the usual make, with wheels from SO in. to 60 in. in diameter, though all the small bicycles have to contend with additional friction in extra moving parts. This is one of the most powerful, because it is the most practical, argument, I have yet found in favour of small wheels. Having now had more than a year's experience of two- speed tuachines, and having three out of my five machines — viz., a Sterling, a Europa, and a Rucker, provided with two-speed gear, I say deliberately that I do not care in future to ride any tricycle that is not furnished with two- speed gearing. Several correspondents have called my attention to the fact that while I ,have highly recommended the Sterling it is only a single driver. I have not overlooked that point, but I consider its merits as a most simple and efficient two speed machine quite over-balance that single dis- advantage. Sir John Herschel said, with regard to the correct figure of a curve for the mirror of a reflecting tele- scope, " that is a good curve which performs well," and I say that is a good form of machine which performs well, and that is the case with the Sterling. Some objections have been raised against two-speed gearings ou the ground of their complication, the uncer- tainty of their action, their liability to get out of order, and the increased friction they cause. My reply is that my Sterling has never, in the hundreds of reversals I have given it from speed to power, failed to act instan- taneously, nor has it ever given me one moment's trouble. I can say the same of my Europa, so far as the speed and power gearing are concerned ; and my frieud, Mr. Grace, gives the same testimony as regards the Diana of the same makers ; while the fact that my two-chain Rucker, with speed and power gear, is by far the fastest machine I have ridden, is a convincing proof that the amount of extra friction produced by the second revolving chain is of no material consequence, and may, in mathe- matical language, be neglected. Very soon I propose to give Eades' new tricycle, the Emperor, a trial. Thi.s novel machine has bicycle .steering, and is central-geared, and is open-fronted above the axle. I am prepared to find that it may require a little practice to develop its best qualitie.'', and to give it, on account of its novelty, the time and attention necessary to form a fair opinion of its qualifications. The Colonial Exhiditio.v.— The Victorian Minin,? Department has decided to send to the Colonial Exhibition, which is to be held iu London in 188G, a scientific and economic mineral oolleotiou representing the geological featiu-es of Victoria. A collection which was sent to Aiii.sterd.am will be used as a nuclcns. THE EARTH'S SHAPE AND MOTIONS. By Richard A Proctor. ( Continued from page 134.) CHAPTER ir.— THE DIURNAL MOTION OF THE STARS.* HAVING satisfitd himself respecting the character of the sun's diurnal motion, our observer, we will sup- pose, turns his attention to the celestial objects which make their appearance when the sun is below the horizon. Among these the moon is the first to attract his attention. I do not propose, however, at present, to devote much space to the diurnal motion of the moon, which closely resembles that of the sun. It may be followed with the instrument represented by Fig. 5, p. 133, without any change what- ever, either in the position of the instrument or in its con- struction. The only peculiarity which would be noticed would be, that the rate of the moon's motion, though uniform, is not e.xactly the same as that of the sun's motion, but somewhat slower. The stars which seem scattered over the whole sky in unnumbered profusion, are the objects to which our observer is now supposed to turn his attention. A very short time suSices to show that, in the east, stars are rising into view, while in the west stars are setting. INIore careful observation shows that all the stars visible to tlie eye are moving with greater or less speed. The stars which rise in the east pass over to the south, where they attain their greatest elevation ; and their motion con- tinuing, they pass down to the west, where they set. Stars which rise towards the south of east attain but a small elevation when due south, and set towards the south-west. Stars which rise towards the north of east attain a con- siderable elevation when due south, and set towards the north of west Other stars are seen, which neither rise nor set ; but appear to travel in circles around a point on the northern skies. And stars very near that point seem scarcely to move at all. Such are the general features of the stellar diurnal motions ; but our observer is now to inquire what are the exact paths which the stars appear to follow. He might notice that a star rising in the east attains in the south about the same elevation as the sun when that luminary rises due east. He is led, therefore, to inquire whether the whole system of the stars maj- not be re- volving (really, or in appearance,) after precisely the same law as he had observed in the case of the sun. The instru- ment which he has constructed to follow the solar diurnal motion (Chapter I., Fig. 5) will serve equally well to follow the sidereal motion, if this sui^picion be correct ; only the observer must be able to look along the rod L M at a star. He need not, however, remove the circular card at M. He may bore a hole through it, and place another card similarly pierced at the end L of the rod, so that the two holes may be directly opposite each other. It, how- ever, the rod L M is a tube, he can look yet more con- veniently at a star through this tube. Thus provided, the observer directs L M to any star whatever, noticing what division of the card H falls opposite the opening in the upright B. At the end of half-an-hour (say) he again directs the tube towards the star. He finds that 1 1 do this he has only to turn the rod F G round on its axis, just as he had done in the case of the sun, and apparently through exactly the same angle. In reality the angle is slightly greater, a matter which will presently be noticed more at length. But the great point to be here * The word diurnal in astronomy is not used as the converse of the word nocturnal, but is applicable to any motions observed dnrinp the twenty-four hours, from noon of one day to noon of the next. Aug. 22, 1884.] ♦ KNO\VLEDGE ♦ 151 noticed is, that every star in the heavens obeys the law of uniform rotation round the axis F G, precisely as the sun and moon had been observed to do. This is indeed a most imiiortant discovery ; and will be found, when we come to examine it, to be full of sig- nificance. In the first place it is to be noted that if the stars were bright points on the inner surface of a vast sjihere rotating uniformly around the earth, their motions would be pre- cisely such as we have thus seen them to be. So that the notion entertained of old by Anaxagoras and his followers — that the stars are the heads of nails driven into the con- cave of a vast dome — however bizarre it may seem in the light of modern science, was founded at any rate on an observed relation. Another notion, somewhat less fanciful, was equally consistent with observed appearances. If a vast spherical crystal shell surrounded the earth, and the stars were bright points fixed within the substance of this crystalline dome, but not necessarily at the same distance from the observer, then the observed diurnal motion of the stars would be accurately reproduced by the rotation of the crystalline shell about a fixed axis through its centre. Let us carefully consider the points thus suggested. Let us take the case of one of those stars which never set. Fig Suppose E (Fig. 1) to be a part of the earth's surface (we are supposed to know nothing as yet of the shape of the earth), and let A C B repre.-ient the imaginary dome of the heavens on which the stars seem to move. Let P be the point to which the axis of our instrument (F G, in Fig. 5 to Chapter I.) was directed throughout our observations. Further, let C D be the apparent path of a star. Now our observations showed us the star going round and round in the circle 0 D, at a perfectly uniform rate. When we saw the star in direction O C, the star must have been somewhere along that line (produced if necessary). Suppose the star was at S. Now where was the star when it seemed to be at other parts of the circle C D ■? The line of sight went round and round 0 P, uniformly and keeping always inclined at the same angle to O P. It therefore described a conical surface of which O P was the axis. Now if our star travelled in S S', a circular section of this cone, then the star motion really was as equable ai it seemed, and the fixed axis O P (produced) passed through the centre of the star's motion at F. But if our star travelled in any other section (necessarily non- circular) as S s, then its motion was not equable, but obviously was slowest at S and swiftest at s. Also the fixed axis O P did not in this second case pass through the centre of the star's path, but through an eccentric point Q. We fee that the path S S' explains observed appearances simply, while the path S s requires altogether artificial assumptions of varying motion around an eccentric axis. But this is only a small part of the difficulties in which we become involved if we give to a star a diurnal motion (relatively to the earth) in any other but a circular path around the axis O P. The path S a- lies wholly above the plane of the earth's surface at E where the observer is sup- posed to stand, and, in fact, I have made the oval S s parallel to A B, because that is the sort of path by which one of the paradoxists explains the diurnal celestial motions. When, however, we take the case of a star which rises and sets, we get a cone corresponding to S E S', but having part of its surface below the plane A B ; so that we have to con- ceive an oval path quite diflferent to S s, not only as regards shape and centring, but in position also. Even this, however, is not all. When we take the case of a star which rises due east and sets due west, the coue corresponding to S E S' becomes a plane. We have, in fact, the case illustrated in Fig. 2, where eOtv represents Fig. 2. the apparent path of such a star on the heavens. Now, in this case, if the true path of the star (relatively to the observer at E) is not a circle (as that of which S A S' is the half), uniformly described, it must either be some other curve s A s' in the same plane, not uniformly described, or if it belong to some other plane as vxll as the plane e C w, it must be a straight line as ^i A S'. For it cannot by any possibility lie out of the plane e C w, since the line of sight from E to the star is observed always to lie in that plane ; therefore, if it belongs to another plane also, it must be on the intersection of two planes ; and we know that two planes can only intersect on a straight line.* When we see that so many artificial and incongruous assumptions have to be made if the a]i[iarent motions of the stars are to be explained in any other way, we can no longer feel any doubt that the simple explanation sug- gested by our observations is the correct one. We con- clude, therefore, that the motions of all stars relatively to the earth, take place uniformly in circles having one line (EP of Fig. 1) as common axis. As yet, however, we do not know whether the celestial sphere, carrying all its stars with it, rotates around the earth on this axis, or whether the earth rotates within the celestial sphere, on an axial line in the same direction. We must make excursions over the earth's surface to determine what the figure of the earth may be, before we can form a probable opinion on this point. And before we can feel abselutely certain we shall need yet other observations. But first it will be necessary to somewhat extend our * It may be noticed in passing that the snn's course when he rises dne east is so very nearly coincident with the conrse of a star so rising, that the account just given is true appreciably for the sun also ; so that if the sun really were travelling parallel to the earth's surface as conceived by one of the paradoxists, he would on Marcli 22 or Sept. 23 (when he rises due east) be travelling in a straight line as 2 A S' with a variable velocity saving its least value when he was at A. How he should ever come back again after going off in the direction A S', until by the enormity of his distance he ap- peared close to the horizon (though, strangely enough, looking appreciably undiminished), we may leave to be settled by those who have flattened the earth. 152 ♦ KNOWLEDGE • [Aug. 22, 1884. observations of the heavens. Hitherto we have only con- sidered the apparent motion of the sun during a single day, and that of the stars during a single night. We have to inquire whether there are any changes from day to day, and if so, what their character may be. It is clear that until we are certain what the aspect of the heavens by day or by night would be in the place whence we are to start on our excursions, we cannot rightly estimate the significance of the appearances presented in other places. ELECTRO-PLATING. X. By W. Slingo. TO the amateur or student, one of the most interesting branches of the electrolytic art is the deposition of a metallic film upon the skeleton of a leaf or upon a mould of one. At this point in this series of papers we ought rather to confine ourselves to the preparation of a mould and the deposition of copper upon it. For several reasons, however, it will be found better to take up and finally deal with the finer work that is involved in plating or typing small and delicate objects, such as leaves, insects, and other animal and vegetable matter. To take an electrotype copy of a symmetrical two-sided animal, such as a herring or other fish, is not diflicult. A rather stiff paste of plaster is prepared and poured on to a piece of greasy paper, fastened on a flat board — a rim being provided to prevent the plaster spreading. The fish, having been oiled to prevent adhesion, is laid on the j)laster, and then gently pressed in until the lower half is, as it were, enveloped or hidden. The plaster is then allowed to dry until it is well set, although not quite hard, when the object is removed and the edges of the mould finished off with the aid of a knife. Two or three small holes are made in the level portion surrounding the figure. The mould is then brushed over with soap and water, and the fish re- placed in its former position. A thin plaster paste is then prepared and poured over the fish and lower mould rather quickly. When quite set and thoroughly hardened, the two moulds, each representing one side of the fish, are easily separated, after which they are placed in an oven to dry. When dry they are treated in the ordinary way — that is to say, they are first saturated with molten wax, and the surfaces, so far as they present an image of the fish, are plumbagoed and connected to the negative electrode of the bath ; leading wires are used if the fish, or whatever else the object may be, is thick, or, in other words, if the copy is to be a work in high relief. It would be possible to make arrangements for taking the copy in one piece, but it is preferable to take it in two pieces, and then filing, fitting, and soldering them together. When the object to be copied is under-cut, or of such a shape as to render the use of plaster impossible — as in the case of, say, a mouse, the elastic-mould process is, as a practical necessity, resorted to. Of course, it would be possible to use plaster moulds, if we divide the copy into four instead of two pieces. Leaves may be very faithfully and beautifully copied. To take the upper side, a plaster-of-paris paste is prepared, on which the back of the leaf is laid and gently pressed. Some little care is necessary here to ensure a good result. Air-holes must be filled up and the plaster, if necessary, helped into its place by means of a thin stick of wood. When thoroughly set and hard, plumbago is brushed over and melted wax is poured on until a layer of sufficient thickness is deposited. When cold, the wax is separated, coated with plumbago, and placed in the bath ; a good electrotyped copy of the leaf i-esults, if the work has l)een performed with sufficient care. Other substances than plaster may be used for imbedding purposes, such as clay or fine sand. Where, however, a soft substance is em- ployed, it is advisable to make the leaf rigid by coating the back with a few layers of thin plaster, allowing each layer to dry before the successive one is applied. Sub- stances which require pressure cannot be used for moulds, because the surface or shape of the object is liable to damage. Gutta-percha is therefore inapplicable. The process for plating leaves, flowers, insects, &c., is an interesting one. The object to be coated is first dipped into a solution of phosphorus in bisulphide of carbon. A silver solution consisting of 1 dwt. of nitrate of silver dissolved in a pint of distilled water having been prepared, the object is immersed in it and kept in until the phos- phorus has caused an entire coating of silver to be deposited, which will be evidenced by a uniform blackness. After washing in clean water, the silvered object is immersed in a solution of chloride of gold, again washed in clean water, and then allowed to dry. When dry, it is placed in the bath, and a thin copper deposit is taken. If bisulphide of carbon is not available, a silver coating may be obtained by dipping the object in the nitrate of silver solution, and then suspending it under a glass jar or receiver, closed at the top, in which a piece of phosphorus is being burned. Another method is to grind in a mortar to a fine powder some nitrate of silver crystals, and shake up the powder with alcohol in a flask placed in warm water. One hundred parts of alcohol should take up about 2^ parts of the nitrate. The object to be copper-plated is dipped in the solution, while warm, for a moment, and on withdrawing the alcohol is allowed to evaporate, the nitrate being left on the object. It is then placed in a vessel containing burning phosphorus, when the salt is reduced and the usual conducting coating is provided. Skeletons of leaves may be treated in the same way as insects or flowers, and beautiful results obtained. The appearance may be further considerably improved by depositing a gold or silver film over the one of copper, of which, however, more anon. I must leave the amateur to work out any special design he may have in view, derived from combinations of leaves, skeletons, and insects, and I fancy that with a little application he may produce, with the aid of various metallic solutions, some remarkably pretty and attractive results. It is, perhaps, worthy of mention, as an interesting fact rather than as an experiment to be repeated, that E. T. Noualhier and J. B. Prevost, in 1S57, introduced a plan to " metallise soft surfaces," such as a human corpse. All the apertures, mouth nostrils, ic, were stopped -n-ith modellers' wax, and pulverised nitrate of silver was spread over the body with a brush. It was then placed in the bath, and a copper coating deposited, the " result being a metallic mummy." The next subject to claim our attention will be the deposition of copper upon the baser metals, glass, ic. The number of workmen employed in oar dockyards at home in- creased from 1879 to 1S8-1 from'l6,381 to 18,8i9. The armoured building had been advanced from 7,427 tons in 1879-80 to 12,614 tons, as proposed in the Estimates for 1884-85. The expenditure on armoured building for 1883-84 and 1884-85 was actually doubled as compared with 1879-80. For the protection of our vast com- merce in every part of the globe we maintain a fleet in commission with an aggregate displacement of 324,256 tons, as comjiared with 171,300 tons for the French. Our fleet in commission was more than double the tonnage of the French, but our mercantile marine was tenfold larger than theirs. Adg. 22, 1884.] ♦ KNO\VLEDGE ♦ 153 DREAIIS: THEIR PLACE IN THE GEOWTH OF PEIMITIVE BELIEFS. By Edward Clodd. VII. IN thus far illustrating the confusion inherent in the barbaric mind between what is and what is not external to itself, and the explanation which it conse- quently gives of such simple matters as a man's name and likeness, the explanation given of matters still dividing philosophers into opposite camps has been hardly indi- cated. The uniformity of this among the lower intelligence in every zone and age might surprise us, and we should be in bondage to the theory which explains it by assumption of primal intuitions of the race, were we not rejoicing in the freedom of the truth of the doctrine of the descent, or ascent, of man from an ape-like ancestry, and the resulting slow development of his psychical faculties, involving his accounting for motion in things around by the like per- sonal life and will of which he is conscious in himself, and for his regarding the world of gi'eat and small alike as the home and haunt of spirits. For the assumption underlying the savage explanation of such things as dreams and diseases involves a larger assumption — namely, that the spirit which acts thus arbitrarily, playing this game of hide-and-seek, now, as it were, caught up into Paradise, and now dodging its owner and worrying its enemy on earth — is, to quote Mr. Spencer's appropriate term, a man's otlier self. It is, at least, what the scientists call a working hypothesis ; it is the only possible explanation which the uncultivated mind can give of what it has not the power to see is a subjective pheno- menon. Odd and out-of-the-way events have happened to the dreamer ; he has been to strange places and seen strange doings, but waking up^ he knows that he is in the same wigwam where he lay down to sleep, and can be convinced by his squaw that he has not moved therefrom all night Therefore it is the other self, this phantom-soul, which has been away for a time, seeing and taking part in things both new and old. We civilised folk, as Dr. Wendell Holmes re- marks, not rarely find our personality doubled in our dreams, and do battle with ourselves, unconscious that we are our own antagonists. Dr. Johnson dreamed that he had a contest with an opponent and got the worst of it ; of course, he found the argument for both ! Tartini heard the Devil play a wonderful sonata, and lay entranced by the arch-fiend's execution. On waking, he seized his violin, and although he could not reproduce the actual succession of notes, he recovered sufficient impressions to compose his celebrated " Devil's Sonata." Obviously the Devil was no other than TartinL Thus the philosopher, to whom dreaming merely indicates a certain amount of uncontrolled mental activity, may satisfy himself; not thus can the savage, who cannot even think that he thinks, and to whom the phenomena of shadows, reflection, and echoes bring confirming evidence of the existence of his mysterioiis double. What else than a veritable entity can his shadow be to him ? Its intangi- bility feeds his awe and wonder, and increases his bewilder- ment ; its actions, ever corresponding with his own, make it, even more than its outline, a part of himself, the loss of which may be serious. Only when the light is withdrawn or Intercepted does it cease to accompany, precede, or follow him, and to lengthen, shorten, or distort itself; whilst not he alone, but all things above and around, have this phantom attendant. The Choctaws believed that each man has an outside shadow, shilombisli, and an inside shadow, shihip, both of which survive his decease. Among the Fijians a man's shadow is called the dark spirit, which goes to the unseen world, while the other spirit, which is his likeness reflected in water or a mirror, stays near the place where he dies. The Basutos are careful, when walking by a river, not to let their shadow fall on the water, lest a crocodile seize it, and harm the owner. Among the Algonquin Indians sickness is accounted for by the patient's shadow being unsettled or detached from the body ; the Zulus say that a corpse cannot cast a shadow, and in the barbaric belief that its loss is baleful, we have the germ of the mediaeval legends of shadowless men and of tales of which Chamisso's story of Peter Schlemihl is a type. The New England tribes called the soul chemung, the shadow, and in the Quiche and Eskimo langi-iages, as also in the several dialects of Costa Pica, the same word expresses both ideas ; while civilised speech indicates community of thought in the skia of the Greeks, the manes or umbra of the Romans, and the shade of our own tongue. Still more complete in the mimicry is the reflection of the body in water or mirror, the image repeating every gesture and adopting every colour, whilst in the echoes which forest and hillside fling back, the savage hears confirmation of his belief in the other self, as well as in the nearness of the spirit of the dead. The Sonora Indians say that departed souls dwell among the caves and nooks of the cliffs, and that the echoes are their voices, and in South Pacific myth echo is the first and parent fairy, to whom at Marquesas divine honours are still paid as the giver of food, and as she who " speaks to the worshippers out of the rocks." In Greek myth she is punished by Juno for divei-ting her attention whDst Jupiter flirts with the nymphs, and at last, pining in grief at her unrequited love for Narcissus, there remains nothing but her voice. But what, in primitive conception, is the more specific nature of the other-self, and how does it make the passage from within to without, and vice versa 1 Very early in man's history he must have wondered at the difference between a waking and a sleeping person, a living and a dead one, and sought wherein this consisted. There lay the body in the repose, more or less broken, of sleep, or in the undisturbed repose of the unawakening sleep ; in the latter case with nothing tangible or visible gone, but that which was once "quick" and warm, which had spoken, moved, smiled, or frowned but a little while before, and which still came in dream or vision, was now cold and still. It should here be remarked, in passing, that many savage races do not believe in death as a natural event, but regard it as differing from sleep only in the length of time that the spirit is absent from the body. Xo matter what anyone's age may be, if his death is not caused by wounds, it is attributed to magic, and the search for the sorcerer becomes a family duty, like the vendetta for other injuries. And the widespread myths which account for death have as their underlying idea the infraction of some law or custom, for which the offender pays the extreme penalty. And that personification of it which pervades barbaric thought, whilst undergoing many changes of form, yet retains its hold in popular conception as well as in poetry. Pictured as the messenger of Deity, the awful angel who sought the rebellious and impious, or who, in mission of tenderness, bore the soul to its home in the bosom of the Eternal, it was transformed and degraded by the grotesque fancy of a later time into a grim and dancing skeleton whetting his sickle for ingathering of the young and fair to their doom, or into the grinning skull and crossbones of Christian head-stones. But to resume. Whilst shadows, reflections, and echoes, one and all seemed to satisfy the uncivilised mind as to the 154 ♦ KNOWLEDGE ♦ [Aug. 22, 1884. existence of the other-self, they gave no key to its nature, to what it is like. Obviously the difference between death and life lay in some unsubstantial or semi-substantial thing. Perhaps, thought some races, it lies in the blood, with the unchecked outflow of which de:itli ensues, and the idea of this connection has not been confined to barbaric peoples. Perhaps, thought other races, it lies in the heart, which, say the Basutos, has gone out of anyone dead, but has returned when the sick have recovered. Among the Greeks some philosophers held that it was fire, which was extinct when the fuel of life was burnt out, or water, which would evaporate away. But, as language shows, it is with the breath that the other-self of the savage and the vital principle of the philosopher has been most widely identified. For it is the cessation of breathing which would in the long- run be noted as the unfailing accompaniment of death ; and the condensing vapour, as it was exhaled, would con- firm the existing theories of a shadowy and gaseous-like soul. In this, as the illustrations to be adduced from various languages will evidence, the continuity of idea which travels along the whole line of barbaric and learned speculation is unbroken. THE WORKSHOP AT HOME. By a Working Man. I HAVE been asked by the Editor of this paper to give directions in its columns for the performance of some of those kinds of handicraft which may be practised by the amateur without assistance. I mean the construction of articles of household use, and furniture, in wood (both by the aid of ordinary joiners' tools and the lathe), and the making of simple apparatus in brass, &c., as well, in the last-named machine. 1 shall begin at the beginning, describe tJie tools to be employed, and their use, and tell the learner not only what to do, but — what is often of as much con- sequence— what not to do. And my first piece of advice will be, " Don't buy a chest of tools." There are certain ones which are essential, which will be found in it ; but, on the other hand, it is sure to contain others of comparatively infrequent use, while some which are certain to be wanted, sooner or later, will be conspicuous by their absence. Start with an outfit suitable to your purse, go to a first-class maker, like Buck, Churchill, Fenn, or Melhuish, or (if you are a wealthy man) to Holtzapflel, get just what you require, and add to your original collection as necessity arises, by to lathe tools ; just now we will those used by the carpenter or joiner. I shall come by-and- confine ourselves to FiK. 2. To begin with, we ought properly to have the three saws shown in the annexed figures ; where Fig. 1 represents ■what is called a "handsaw," for cutting planking the 1 engthways of the grain of the wood ; Fig. 2, a " tenon- saw," for cutting across the grain ; and Fig 3, a "bow " or " frame-saw," for sawing round curves. A very thin, narrow saw, sliding through a handle (or " pad "), and called a "keyhole-saw," will sometimes be found useful; but we can dispense with it for the present. Next, we bhall require three planes, two of which are depicted in Figs. 4 and 5. Fig. 4 is known as a "jack-plane," and is Fig. 4. used for the first rough planing-up of wood as it comes from the timber merchant. A longer and " finer-set " form of this workmen call a " trying (by which is meant true-ing) Fig. 6. Fig. 9. plane," It is used to produce a perfectly flat surface ; and Fig. 5 is a "smoothing-plane." In addition to this, there are " plough," " rabbeting " (or rebating), " side filister," "match," "grooving," "moulding," "beading," and divers other planes, to more than one of which I may have to return. Any one of these, though, if wanted for a special job, can be bought subsequently. Then we shall require at least four "firmer" chisels," — 1-in., |-in., i-in., and ^-in. — (Fig. 6), and a couple of gouges, together with a wooden mallet, four gimlets, three bradawls, a hammer, a square (Fig. 7), a marking-gauge (Fig. 8), and a moitice-gauge (Fig. 9), a two-foot joint-rule, or else a yard measure, an oilstone, a glue-pot and brush, glue, screws and nails ; Nettlefold's screws in cardboard boxes and the so-called " French " or wire-nails being the best for the amateur. The tools I have enumerated may Aug. 22, 1884.] • KNOWLEDGE ♦ 155 be considered as essential. They will cost as nearly as may be .£2. Ss. at a good shop. A carpenter's bench, too, is a great desideratum, but a very tirm table will do for smaller jobs, especially if it is placed in the corner of a room so that one end and one side of it abut against the adjoining walls. The amateur who is about, though, to take up carpentering in earnest, had better buy a bench. A new one of sufficient size for ordinary amat<"ur cabinet- making may be bought for five and forty shillings or so, but occasionally a second-hand one may be picked up for much less. Suppose, then, that the reader has provided himself with the tools mentioned above, the next thing will be to learn how to use them in an attempt upon a simple piece of work. Asa preliminary, though, even to this, it is essential that they should, one and all, be very sharp . No good or even decent work ever was done yet with blunt tools, or ever will be ; so we had better begin at the very beginning by learning how to sharpen ours. Saw-sharpening the amateur had better not attempt — at all events, for some time to come. It is an art which requires a considerable Fifr. 11. ^ Fig. 10. Fig. 12. amount of practice ; and, besides, he can get them sharpened and set for 3d. a ]iiece ; so that the game is really not worth the candle. Using the word ''set" just now, re- minds me to explain that a saw is set by bending its teeth alternately to the right and to the left ot' the plane of the saw ; so that if we suppose the first, third, fifth, and seventh teeth to bend to the left, the second, fourth, sixth, and eighth, and so on, will be bent to the right. If the reader ■will turn a saw-edge upwards and look along it, he will see what I mean in an instant. His plane-irons and chisels, though, he must, perforce, sharpen himself. To get out a plane-iron, a long plane (like Fig. I) should be knocked with a mallet on the front part of the top of it. In the case of the smoothlng-plane (Fig. 5) the iron is released by striking the hinder end of the plane. Having got our iron out, we shall find it present the appearance of Fig. 10, where i is the cutting plane-iron proper ; in front of which is screwed b, the break-iron (so called because it breaks the ehavings and causes them to curl up). These two irons Now it will be noticed at occe that this iron is sharpened from the back only, its face being perfectly flat, and the angle at which it has been found in practice the best to sharpen it is one of .3-")^ (there are, as everyone knows, 360^ in a whole circle, and 90" between two lines that stand square to each otiier). Any one who knows the XXIXth proposition of the 1st Book of Euclid will see at once the explanation of the little "dodge" I am going to describe. By the aid of the " protractor," to be found in every case of mathematical instruments, we cut out a bit of card ABC with its angle at B = 35'' and that at A a right angle. If now we put our piece of card so that its side B C shall lie lengthways along the face of the plane iron P I, and placing the iron on our oilstone OS, Fig. 11, tilt up the plane-iron until the side of the triangle A B is parallel with T D, the top of the stone, we shall have B C D = A B C, or measuring 3.J", so that we have only to keep our plane-iron steadily at this tilt to sharpen it accu- rately. After rnbbing it sulficiently we must lay it per- fectly flat on its face on the stone, and give it a rub or two to take otf the rough or " wire" edge caused by sharpening it from behind. Then we replace our break-iron, and put the plane together again, being careful that the edge of tho iron is o«Zi/ just visible when the bottom of the jilace is looked at edgeways from the front. A firmer chisel (Fig. 6) may be sharpened in precisely the same way. It is almost needless to add that some clean olive oil must be dropped on the stone before we begin sharpening. Very well. Suppose that we have got all our tods thoroughly sharp and in good order, we will begin by makin;i the wooden framework for a three-leaved screen ; to be afterwards covered with canvas and scrap engravings, or bronzed American cloth, and painted with flowers. The three frames, which must, of course, be identical in size and shape, I will suppose to be each 5 feet high by 2 feet wide, the framing being l\ inch wide and ^ inch thick. In each frame we shall require two upright sides (technically called the "stiles"), each 5 feet long, and three transverse pieces (known as the " rails"), each 2 feet long. This will involve our buying 13 feet 3 inches (or thereabouts) of 1 inch deal planking, which will be 7 inches wide, and must be free from knots. It will, in one sense, cut to waste, i e , we shall not use it all, but a little reflection will show that we cannot get wool of the dimensions we want out of a smaller plank. It may, though, pretty evidently be in the form of two planks — one 5 feet 1 inch, and the other S feet 2 inches. The odd inches are to enable us to cut the ends of our styles and rails truly square, and yet leave them of the right length. Out of our 5 feet 1 inch piece of board we shall (allowing for planing - up) only get five stiles ; so we begin by drawing f.iur straight lines on it, equidistant from its edges, and parallel to them and to one another. This will divide the 7 inclies of width into five equal strips each, ly*j inch wide. The jilane will reduce this width to our adopted one, when it comes to be used. But perhaps in a job like this, we had better plane up our board first; so, laying it on our bench, or a very flat table, with a stop of some sort in front of it (N.B. This stop must obviously project above the bench or table less than the thickness or Fig. 13. are connected by the screw s, which must be loosened by a screw-driver until it moves up and down easily in the slot, through which it. is to be drawn until the screw-head comes opposite the big round hole at the top of the slot, through which it can be then drawn, and the plane-iron will be free. the bo.ird, or it will catch the plane every time), we begin with the jack-plane (Fig. 4), and go all over the board. Having taken otf all the dark and rough outside, we finish up with our tr)ing-plane. The amateur must try to plane hollow, or his plane will take oflT too much at each 156 ♦ KNOWLEDGE ♦ [Arc. 1884. end of the board, and it will assume a more or less convex outline. From the very construction of the tool, he will fail in his attempt, but this must be the tendency of his planing. When, however, he can take off shavings of the whole — or nearly the whole — length of the board, lie may rest satisfied. By looking at the boaid edgeways, he will see when it is perfectly flat on both sides, and then he must plane the edges too, taking care that they are square to the face of the board. He must try this all along with the square (Fig. 7). Now, then, he can mark his 5 feet 1 inch piece of board into the 5 equal strips, and laying it down on a very firm wooden chair or box, saw it into strips with the hand-saw (Fig. 1). He should pencil the lines along which he is to saw, clearly, and take particular care that the plane of the saw is square to the face of the board. It must be sloped, though, in the direction of its length. Little short cuts may be made at first, and then, when the saw is fairly in the pencil-line, longer ones ; but the saw must be watched and brought into the line again, if it shows the slightest tendency to wander from it. In this way, then, must the beginner saw out the fifteen strips of wood he requires, the six " stiles " 5 ft. long, and the nine "rails " 2 ft. long. The edges of these must now all be planed up truly, and the strips cut to their exact lengths by the tenon-saw, the lines defining those lengths being marked by the aid of the square (Fig. 7) and pencil. As I began by saying, the planing should finally leave the strips IJ in. wide and | in. thick. It now remains to fit our frames together. For simplicity's sake, we will make the corner joints like those of the frame of a school-slate. The middle rail, however, must be morticed in. I have said that the thickness of the wood is just Jths of an inch ; so we begin by loosening the screw in front of the mortice-gauge (Fig. 9), separating the little points f ths of an inch, and then moving up the wooden fence or guide until it is | inch from the lowest point, finally tightening all up by the screw again. It will be seen that if now the gauge be run along the edge of the wood, it will draw two parallel lines gths of an inch apart in the middle of its thickness. Let us suppose that we have one of our 2 feet " rails " so marked, then at 1| inch from each end we draw a line truly square round it with the scjuare and pencil, as before, and taking the tenon-saw (Fig. 2), cut along the line marked by the mortice-gauge down to our pencil-mark, and then saw from each face on our pencil-line down to this cut. This will obviously take oflf two thin slabs of wood, about ] in. thick, H in. wide, and IMn. long, and will leave the two smaller ends or "tenons," t t, standing as in Fig. 12, in which/ repre- sents the rail as seen from the front, and e as viewed edgeways. In sawing out these tenons the marks should all be Jeft visible, and not obliterated by the saw-teeth passing actually through them. Leaving the mortice-gauge undisturbed, we now run it along the edge of our 5-ft. "styles" (Fig. 1.3), at each end of which we cut with the tenon-saw 1| inch down into the wood, leaving the gauge-lines visible on that, too, and by the aid of our quarter-inch firmer-chisel clear out the two apertures s s. As we went inside the marked lines in cutting these out, and oulside the lines in cutting our tenons, the latter will fit veiy tightly into them ; so tightly, perhaps, as to involve a little delicate shaving or scraping of the tenon before it will enter without splitting the end of the style. This joint may be seen at the corners of an ordinary school- slate. In the middle of the frame, though, at m, it is obviously inapplicable, so here we must make a regular " mortice." This is a rectangular opening through the whole width of the style, I^in. long and -Jin. wide (the width and thickness of the tenon respectively). Carefully outlining this on both edges of the wood, the amateur had better begin by boring a series of holes in this marked space with the biggest gimlet he has, and then carefully and truly clearing out the rectangular opening or mortice with sharp chisels. If the reader has followed me so far, he will see now that the tenons will drop, with a little pressure or knocking, into the mortice in each rail at m, and into the apertures s s, at the ends of them. When everything is neatly fitted together, the styles and rails laid in order must be once more separated, the tenons and the holes they are to enter rapidly brushed with fresh, thin, hot glue, and the whole frame put together again as rapidly as possible, tied or cramped tightly together, and set aside for the glue to cool. Finally, the reader may once more get his biggest gimlet, and bore holes through the styles and the tenons, and cutting some bits of deal verij slightly conical with a penknife, dip them in hot glue, and drive them home as far as they will go. The tenon-saw will trim them off level, or practically so, with the face of the wood, and a finishing touch can !:« given with the smoothing-plane (Fig. 5). These wooden pins are technically called " dowels." The frame now completed is represented in Fig. 14. Three ot these will, as we began by saying, have to be constructed, and they must be united by two pairs of brass hinges (called "butts"), which may be bought, with the necessary screws, at any ironmonger's. Note that they must be placed on — so to speak — alternate edges of the frame for the screen to fold properly. It only remains to cover the screen with canvas or American cloth, and this may be nailed on with the smallest tacks or with cabinet-maker's brads. The decoration of the screen with scrap engravings, pasted ot to the strained canvas, or with flowers painted in oils on the American cloth, may safely be left to the taste^ of the reader. Fig. 14. THE GREELY EXPEDITION. By Andrew McPhersos. THE account which was published in Knowledge last week of the doings and sufferings of the Greely band of explorers has been supplemented in an unlooked-for and unpleasant manner. A charge of cannibalism has been preferred against the surviving members of the crew, and- although the charge has not received oflicial confirmation, it has not been met with that categorical refutation which one would wish for. But, after all is said, what does the charge amount to "i That cannibalism is in itself abhorrent no civilised being would deny ; but to go so far as some of our contemporaries seem disposed to do, is, so far as I can see, uncharitable in the highest degree. I think, rather, that to be so reduced by want of food as to render one capable of overcoming the feelings of revulsion which must present themselves, is indicative of agony of the acutest description, and demands our sincerest pity and commiseration rather than condemnation. As Dr. Rae, a well-known explorer, writing to a con- temporary, says : — " It is all very well for those who, probably, have never been twenty-four hours continuously Aug. 22, 1884.] ♦ KNOWLEDGE ♦ 157 without food in their lives to enlarge most indignantly on the suViject. Had they been for days, as I have, living, or, rather, existing on the smallest scraps of skin and bones, and enjoying the most disgusting-looking food as if it had been the greatest delicacy ; had they but witnessed the sufferings and cravings of some of my tine fellows during these times of privation, they would have had some know- ledge of what starvation meant." Charges of bad discipline are also brought, as helping to account for the resort to cannibalism ; but such charges re- quire only a moment's consideration to be contemptuously hurled aside. Suffice it to say, that the members of the crew were picked from one of the best disciplined bodies of Mien in the States. We have occurring around ua almost daily, suicides and perhaps murders, actuated only too frequently by want of food, and yet we do not give vent to the same feeling of horror that has found utterance against the supposed doings of the unfortunate travellers, icebound and starving. It is po.ssible, ray more, it is highly probable, that many a similar expedition has in bygone days resorted to similar means to sustain vitality, but surely no pleasure or satis- faction can accrue to a healthy-minded man in peering into and scanning with microscopic eyes all the doings of men when reduced to the greatest extremities to which humanity is susceptible. Let us then rather close our eyes to such pictures, regard the survivors with pity, and do what in us lies to prevent a recurrenceof the dreadful episode. It is clear that nothing further can be gained by Arctic exploration — nothing that is which is likely to be of any use to mankind ; and it behoves us therefore to discountenance any further expeditions. But, perhaps the most fitting conclusion to these few remarks is afforded by what Mr. Proctor said last week in the Newcastle Chronicle. " The expedition has ended, as many feared that it must end, in the loss of nearly a score of lives, and the probable loss of health and strength on the part of the seven sur- viving members of the ill-fated party. Per contra, some little light has been thrown on the position of certain shores, mountains, and so forth, which wUl never be visited for any useful purpose by human beings, while the Noi-th Pole has been approached nearer by some eighty miles than at any previous Arctic expedition. In what respects such expeditions as these differ from Captain Webb's attempt to swim the Niagara rapids, except that many lives are risked instead of one, it would be difficult indeed to say. The members of the expedition were gallant and enduring men ; but Webb was as brave and as resolute. They risked their lives ; he risked his. It was certain beforehand that no good could come from Webb's attempt ; it was no less certain that no considerable advantage to the human race -could accrue from any new Arctic expeditions. A certain element of savagery in our most cultured races, by which importance comes to be attached (goodness knows how) to tiseless exploits, is exhibited in such attempts. That is all we can say for them." A NEW VOLCANO. THE Secretary of the Treasury has received from Captain M. A. Healy, of the United States revenue cutter, Corimn, under date of Ounalaska, May 2S, two interesting reports by otficers of the Corivin describing a visit to the recently upheaved volcano in Behring Sea at the northern end of Bogoslofl" Island, in latitude 53° 55' 18" N.; longi- tude 168° 00' 21" W. This volcano, which is in a state of constant and intense activity, was upheaved from the sea in the summer of 1882, but was not seen by any civilised eye until Sept. 27, 1883, when it was discovered by Captain Anderson, of the schooner 2Iatthew Turner. A few days later it was also seen by Captain Hague, of the steamer Dora, but no landing upon it was made previous to that by the officers of the Corwin last spring. Dr. Yemans describes it as a dull gray, irregular, cone- shaped hUl, about 500 ft. in height, from the sides and summit of which great volumes of vapour were arising At a height of about two-thirds the distance from the base to the apex of the cone, there issued a very regular series of large steam-jets, which extended in a horizontal direction, completely across the north-western face of the hill. Around these steam-jets were seen upon nearer approach deposits of sulphur of various hues, which at a distance had looked like patches of vegetation. A landing was effected without difficulty upon a narrow sand spit connecting the new volcano with the old island of Bogosloff', and Dr. Yemans and Lieut CantweU undertook the ascent of the smoking cone. It was covered by a layer of ashes formed into a crust by the action of rain, which was not strong enough to sustain a man's weight, and at every step the climbers' feet crushed through it, and they sank knee-deep into a soft, almost impalpable dust which arose in clouds and nearly suffocated them. As the summit was neared, the heat of the ashes became almost unbearable. A thermometer buried in them halfway up the ascent marked 196°, and in a crevice of the ram- parts of the crater " the mercury rapidly expanded and filled the tube, when the bulb burst, and shortly after- wards the solder used in attaching the suspension ring to the instrument was fused." The temperature was esti- mated at 500° F. On all sides of the cone were per- forations through which the steam escaped with more or less energy, and in some cases at regular intervals like the exhaust of a steam engine. The interior of the crater could not be seen on account of the clouds of smoke and vapour which filled it. " A curious fact to be noted," Lieut CantweU says, " in regard to this volcano is the entire absence, apparently, of lava and cinder. Nowhere could I find the slightest evi- dence of either of these characteristics of other volcanoes hitherto examined in the Aleutian Islands." Volcanic dust or ash, however, is thrown out in considerable quantities, and carried by the wind to places as distant as Ounalaska. After carefully measuring the volcano, and photographing it from various points of view, the exploring party returned, without accident, to the ship. Captain Healy reports his intention to visit the new volcano again on his return from St. :Michaers and the Arctic. — Kamas City Review of Science and Industry. THE WESTINGHOUSE BRAKE. By " Teetithick." A FEW weeks since I commented upon one or two of the relative features pertaining to the various brakes used in railway working. It has, of course, been apparent from the time when the first train was started, that an efficient brake would, sooner or later, be an essen- tial feature in railway working, and Stephenson, having this fact in view, patented fifty years ago a steam brake to be applied to the engine by the driver. The increased length of trains, their multiplicity and high speed, require something more than this. Several brakes have been introduced, which may be divided, as I have previously indicated, into two classes, \-iz.. Local (that is, operative on the individual vehicle only) and Continuous. The local 158 • KNOWLEDGE ♦ [Are. 22, 1884. brakes are very rapidly dying out, and in all probability will soon become things of the past, so far at least as rail- way working is concerned. The continuous brakes may bo subdivided into two sections, which may be denominated automatic and non-automatic, terms sufficiently clear to explain themselves. It is to the automatic that attention is now drawn, and the Westinghouse is taken as the specimen, although, as will be seen presently, it is nearly without a peer. The Westinghouse Automatic Brake, named after the pateiitee, is worked by air pressure. A small, but powerful, air-pump is ])laced on the engine, and with the aid of steam d-rived from the locomotive boilers, air is forced either into a re.'-ervoir under the foot-plate of the engine, or through a one-inch pipe extending throughout the length of coupling with similar pipes on the adjoining vehicles. A branch-pipe connects E with an essential and eminently interesting piece of apparatus called the Triple Valve, F, which is in reality the controlling piece of mechanism, and of which Fig. 2 is an enlarged view. Enclosed in a case, 1, is a piston, 5, carrying with it a slide- valve, 6, which covers the port, a, to the brake cylinder, and iu the position shown establishes a communication between a and the atmosphere by the exhaust-cavity h and passage c. Compressed air from the main pipe E enters the lower part of the case, and forcing up the piston, 5, feeds past it into an auxiliary reservoir (G, Fig. 1) through the groove d (Fig. 2) and the outlet C. This reservoir is thus filled with air under a high pressure (the same as that in the main pipe), and as things now are, this air cannot escape. Fiff. J the train. The pnmp is entirely under the control of the engine-driver, and he is at liberty, by simply turning a handle, to connect it with his reservoir (T with the pipe. He is also able t > connect the pipe with the external atmo- sphere, so as to reduce more or less completely the air- pre^sure in the pipe, which nominally is about 701b. to the square inch. The pump and its appurtenances, however, need not furtlier detain us, as notliing essential to the proper working of the system is involved ; all that is re- quired being a means of rapidly raising the pressure in the pipe, of easily exhausting it, and of spt edily re-establishing it. Let us turn our attention to the brake proper. The acconi]ianying illustration will materially help «s. Fig. 1 is a general representation of the apparatus as applied to every individual vehicle. A one-inch pipe, E, which rnns the length of the carriage, is connected by an ingenious At the same time, the slide-valve (6) covers the port a, leading to the "brake" cylinder (H, Fig. 1), and is in such a position that air from the latter may exhaust through h and c into the atmosphere. In the brake cylinder are two pistons, which are pressed inwards and almost together by sfiiral springs ; but when the air enters from a (Fig. 2), through the short connecting-pipe shown in Fig. 1, it passes into the small space separating the pistons, and drives them outwards. To each piston is attached a rod, which, acting on a lever, presses a friction block against each side of the wheel. So long as an equal pressure is maintained in the reservoir, triple valve, and brake-pipe, the brakes are off, the brake cylinder being in direct comniuiiication with the air, and the spring.'^, therefore, effectually keeping the pistons near each other, and consequently the friction-blocks clear of the wheels ; but on the pressure in the main Aug. 22, 18e4.] * KNOWLEDGE . 159 pipe and beneath the piston, 5, being suddenly reduced, the piston falls, and by so doing shuts otl' both the reservoir from the main pipe E and the cylinder from the exhaust port D ; at the same time the passage from the reservoir to the cylinder is open, and air passing from the former to the latter, the brakes are applied. Fig. 2. For the purpose of graduating the brake with the greatest nicety, that is to say, normally ■nhen approach- ing a station, a small valve, 7, is introduced into the slide-valve, 6. The action is as follows : — Upon a slight reduction of pressure in the brake-pipe being made, the piston, 5 — having a limited movement, without affecting the slide-valve, 6 — will descend, thereby closing the feed- groove d, at the same time unseating the valve, 7, which thus opens the passage e. The slide-valve, 6, then moves until the passage e opens into port a, leading to the brake- cylinder, the communication from which to the exhaust is at the same time cut ofl". The further downward move- ment of the slide-valve, 6, is arrested by the decrease of pressure above the piston, caused by the air flowing into the brake-cylinder. So soon as the pressure in the reser- voir is thus reduced a little below that in the brake-pipe, the piston, 5, moves up of its own accord, and closes the valve, 7, while the slide-valve, 6, retains its position. By simply regulating the reduction of pressure in the brake- pipe, and causing the motion of the piston and graduating- valve, 7, to be repeated, the driver can gradually introduce any desired pressure into the brake-cylinder from zero up to full power. However, if a considerable reduction of pressure in the main pipe is suddenly made, the piston, ."), is seated on the leather gasket, 10, while the port a is entirely uncovered, and the brakes are thus applied witli full force. To release the brakes, air is again admitted from tha main reservoir to the brake-pipe Viy means of the driver's valve. This store of power acting against the reduced pressure in the small reservoirs, forces the piston, 5, into the position shown, thus permitting the air in the brake- cylinders to exhaust, while at the same time the reservoirs are recharged. To prevent such application of the brakes as might result from ordinary leakage in the brake-pipe, a small hole runs from the face of the slide-valve t() the passage e. In such a case a piston and slide-valve descend very slowly, and as the port a is open both to the exhaust cavity, h, and the leakage hole during the first por- tion of the stroke, air from the reservoir is able to escape by this means into the atmosphere, instead of passing into the brake-cylinder. The reduction of ))ressure thus caused above the piston, as already explained, prevents the slide- valve from moving far enough to close the communication between the port a and the exhaust cavity b. The only moving parts of the triple valve (an ordinaTij pislon and slide valve moving together as one piece) do not make as many motions in fifteen years as are made by the piston and slide-valve of the locomotive in one day ; hence their durability is beyond question, and this is confirmed by many years' experience. A stopcock is placed in the branch-pipe (between E and F, Fig. 1) for the purpose of closing the connection with the triple valve on anyone vehicle without interfering with the operation of the brakes upon any other. A release valve (inserted in the tube connecting F with H, Fig. 1), operated by hand from either side of the train, may be opened to allow the air to escape direct from the brake-cylinder if necessary. The leservoir space is about five times that of the braka- cylinder, consequently, a reduction of 20 per cent, in the brake-pipe pressure fully applies the brake, each pound reduction of pressure in the brake-pipe producing several pounds per square inch in the biake-cylinder. By the action of tlie triple valves, moreover, the brakes cannot be released without re-charging the small reservoirs, and owing to these features it has been found in working that the store of power is practically never-faiiing. It is evident from what has been said that if by any means, air is allowed to escape from the main-pipe, the brake must be brought into action, whether it is required or not. This fact constitutes the one great recommendation of the brake to the travelling public, which, I appiehend, embraces the va-^t majority of our countrymen. We are not so much inter.-sted in bone-shaking stoppages at stations, as we are in being arrested on what might otherwise be the highroad to destruction. The brake may be relied upon to o[)erate within 200 yards when running at fifty miles an hour. It is not, however, in such cases only that 160 * KNOWLEDGE ♦ [Aug. 22, 1884. the need for a brake exists. In the event of a train dividing, more especially when on either a rising or a falling gradient, it is important that the brake should be applied instantly to every section of the train. It may be taken as a certain eventuality that if a carriage gets oflF the rails, the couplings -will be broken, together with the brake-pipe. The rupture of this pipe, however, causes an instantaneous reduction of pressure withia it to 15 lb., that is to say, to the same as that of the atmosphere outside. The result is that the triple valve is In-ought into energetic action, is impressed downwards, and opens the small reservoir into the brake- cylinder. The brake is therefore immediately and most firmly applied, and the motion of the carriage arrested -axitomatically. Had a device of this kind been fitted to the trains which met with such fatal accidents at Downton, Penistone, &c., there is every reason to believe that the lives of the victims would have been spared, because the carriages would have been so pulled up that they would not have rushed down the embankments as they did, but would in all probability have remained near the rails. {To he continued.') OTHER WORLDS THAN OURS. A WEEK'S CONVERSATION ON THE PLURALITY OF WORLDS. By Mons. de Fontenelle. with notes by richahd a. proctor. {Continued from p. 138.) THE SECOND EVENING.— THAT THE MOON IS A HABITABLE WORLD. NEXT morning I sent to the Marchioness's apartments, to know how she had rested, and whether the motion of the earth had not disturbed her t She sent word back, she began to be accustomed to it, and that she had slept as well or better than Copernicus himself. Soon after, there came some neighbours to dinner, who, according to the tiresome rural custom, staid till evening, and were very obliging in going then ; for the country also gives a privilege of extending their visit to the next morning, if they are so disposed : when they were gone, we walk'd again into the park, and immediately fell upon our systems. She so well conceiv'd what I told her the night before, that she desired I would proceed without any repetition. " Well, madam," said I, " since the sun, which is now immoveable, has left off being a planet, and the earth which turns round him, is now become one, you will not be sur- prised when you hear that the moon is an earth too, and that she is inhabited as ours is." " I confess," said she, " I have often heard talk of the world in the moon, but I always looked upon it as visionary, and mere fancy." " And it may be so still," said I ; "I am in this case as people in a Civil war, where the uncertainty of what may happen makes 'em hold intelligence with the opposite party, and correspond with their very enemies : for tho' I verily believe the moon is inhabited, I live civilly with those who do not believe it ; and I am (like some honest gentlemen in point of religion) still ready to embrace the prevailing opinion : but 'till the unbelievers have a more considerable advantage, I am for the people in the moon." " Suppose there had never been any communication between Paris and St. Dennis, and a cockney who was never beyond the walls of this city, saw St. Dennis from the towers of Notre-Dame, you ask him if he believes St, Dennis is inhabited as Paris is 1 He presently answers, ' No : for,' says he, ' I see people at Paris, but none at St. Dermis, nor did I ever hear of any there.' 'Tis true, you tell him, that from the towers of Notre-Dame he cannot perceive any inhabitants at St. Dennis, because of the distance ; but all that he does discover of St. Dennis, very much resembles what he sees at Paris, the steeples, houses, walls, (fee, so that it may very well be inhabited as Paris is : all this signifies nothing, my cockney still persists that St. Dennis is not inhabited, because he sees nobody there. The moon is our St. Dennis, and every one of us as mere cockneys as he that never was out of his own city." " You are too severe," said she, " upon your fellow- citizens ; we are not all sure so silly as your cockney ; since St. Dennis is just as Paris is, he is a fool, if he does not think it inhabited : but the moon is not at all like the earth." "Have a care what you say," replied I; "for if the moon resembles the earth, you are under a necessity to believe it inhabited." " If it be so," said she, " I own I cannot be dispensed from believing it ; and you seem so confident of it, that I fear I must, whether I will or no. It is true, the two motions of the earth (which I could never imagine till now) do a little stagger me as to all the rest. But, yet, how is it possible the earth should enlighten as the moon does, without which they cannot be alike t " " If that be all," said I, " the difference is not great, for it is the sun which is the sole fountain of light : that quality proceeds only from him ; and if the planets give light to us, it is because they first receive it from the sun. The sun sends light to the moon, and she reflects it back on the earth. The earth in the same manner receives light from the sun, and sends it to the moon ; for the distance is the same between the earth and the moon, as between the moon and the earth." " But is the earth," said the Marchioness, " as fit to send back the light of the sun as the moon is 1 " " You are altogether for the moon," said I ; " she ia much obliged to you. But you must know that light is made up of certain little balls,* which rebound from what is solid, but pass through what admits of an entrance in a right line, as air or glass ; so that what makes the moon enlighten us is that she is a firm and solid body, from which the little balls reboimd ; and we must deny our senses if we will not allow the earth the same solidity. In short, the difference is how we are seated ; for the moon being at so vast a distance from us, we can only discover her to be a body of light, and do not perceive that she is a great mass, altogether like the earth ; whereas, on the con- trary, because we are so near the earth, we know her to be a great mass, proper to furnish provision for animals, but do not discover her to be a body of light, for want of the due distance." "It is just so with us all," said the Lady; "we are dazzled with the quality and fortune of those who are above us ; when, do but look to the groundwork, and we are all alike." " Very true," said I, " we would judge of all things, but still stand in the wrong place ; we are too near to judge of ourselves, and too far off to know others ; so that the true way to see things as they are, is to be between the moon and the earth, to be purely a spectator of this world, and not an inhabitant." " I shall never be satisfied," said she, " for the injustice we do the earth, and the too favourable opinion we have of * We have here a popular account of the emission theory of light, which in Fontenelle's time (it is hardly necessary to say) was * regarded as scarcely open to question. — R. P. Aug. 1884.] ♦ KNOW^LEDGE ♦ 161 the moon, 'till you assure me that the people in the moon are as little acquainted with their advantages as we are with ours, and that they take our earth for a planet, with- out knowing theirs is one too." " Do not doubt it," said I, " we appear to them to per- form very regularly our function of a planet. 'Tis true, they do not see us make a circle round them, but that is no great matter. That half of the moon which was turn'd towards us at the beginning of the world, hath been turn'd towards us ever since ; and those spots in her, which we have thought to look like a face, with eyes, nose, and mouth, are still the same ; and if the other opposite half should appear to us, we should no doubt fancy another figure from the different spots that are in it : not but that the moon turns upon herself, and in the same time that she turns round the earth, that is, in a month ; but while she is making that turn upon herself, and that she would hide a cheek, for example, and appear somewhat else to us, she makes a like part of her circle round the earth, and still presents to us the same cheek : so that the moon, who in respect of the sun and stars, turns round herself, in respect of us, does not turn at all : they seem to her to rise and set in space of [about] fifteen days ; but for our earth, it appears to her to be held up in the same place of the heavens. 'Tis true, this apparent immobility is not very agreeable for a body which should pass for a planet, but it is not altogether perfect ; the moon has a kind of trembling, which causes a little edge of her face to be sometimes hid from us, and a little edge of the opposite half appear ; but then, upon my word, she attributes that trembling to us, and fancies that we have in the heavens the motion of a pendulum, which vibrates to and fro."* (To be coniiHued.) THE INTERNATIONAL HEALTH EXHIBITION. XIII.— WATER AND WATER-SUPPLIES— (confinued). THE excellent filter-case described in our last communi- cationj not only provides for the outflow of every drop of filtered water, but can be taken to pieces and thoroughly rinsed when desired. A glance at the sectional figure (Fig. 22) will explain how this may be accomplished. To the apparatus thus constructed Messrs. Doiilton ife Co. have adapted the Patent Manganous Carbon Block, which is exempt from the disadvantages of the ordinary " block " principle. The latter are prone to harbour organic and other impurities to such an extent as to render them quite unwholesome. Thus, the Rivers Pollution Commissioners state that "the property which animal charcoal possesses in a high degree, of favouring the growth of the low forms of organic life, is a serious drawback to its use as a filtering medium for potable waters.''^ The Army Medical Report, again, states of charcoal in porous blocks, that, " after a time the purifying power becomes diminished in a marked degree, and water left in contact with the filtering medium is apt to take up impurity again, § It is well known that carbon is adapted to filtering pur- poses, on account of its property for appropriating and condensing oxygen, which it parts with to organic sub- * Of course the lunar vibrations are not real tremblings, as liere described. They arise, in fact, from the nniformity of her rotational motion, combined with her steady, though not abso- lutely uniform motion, on a path slightly inclined to the plane of her equator. — R. P. + Ut supra, p. 139. J " Sixth Report," p. 220. § " Army Medical Report," XIX., p. 170. stances brought to it, and oxidises or burns them up. Animal charcoal is peculiar in its decolourising or bleaching effects, and vegetable charcoal has the power to deodorise. A combination of the two deprived of all adventitious matters is, therefore, of the highest value to filter manu- facturers who seek to purify water for drinking. To entirely discard such a valuable medium would indeed be to "fly in the face of Providence." The problem which here arises may be solved in either of two ways : — (a.) The purified mixture of carbon should be such as to provide for a constant reparation of its properties ; or (p) It ought to be easily replaceable at a very trivial cost. We have already stated that experiment has shown the " block " system to be faulty, because it soon becomes over- taxed, and no amount of boiling or scrubbing can restore it to its pristine active condition. The only remedy is to be sought for in a renewal of the block, but the frequent necessity for such an operation has the great disadvantage to be a very expensive process. Such was the state of affairs when the block system " ruled the roast," that the domestic filter came to be looked upon either as a trouble- some luxury, or, when neglected, as a dangerous con- trivance. Yet the necessity of an efiicient household water purifier made itself sorely felt, and Messrs. Doulton i Co., as one of the oldest and most celebrated firms of filter manufacturers, felt themselves called upon to remedy matters. They consulted Dr. Albert J. Bernays, F.C.S., the Professor of Chemistry at St. Thomas's Hospital, and the result of his researches, which extended over a period of three years, is now embodied in their " Patent Man- ganous-Carbon Filter." Fig. 25 shows one of these filters Fig. 25. — Doulton's Patent " Manganous-Carbon " Block Syphoia Filter and Case. For the use of tourists and erplorers. as adapted to the use of tourists and explorers. The carbon block can be immersed in any pond or stream, and a draught of pure water sucked through the flexible tube. These filters may also be used upon the " Syphon " principle ; the block may be placed in a pail of water, and the flexible tube permitted to hang over its side, below the level of the block ; once set going by suction, their action thereafter becomes continuous. The value of manganous-carbon as a filtering medium has been set forth by Messrs. Doulton in their prospectus^ in the following outline of its reactions : — " With the object of rendering the charcoal pure in the manganous- carbon filter, each grain of the medium receives a coating of manganese dioxide, and is then reournt at a high tem- perature in absence of air. By this means the hydrogen- bearing impurities are oxidised and removed. At the same time the manganese dioxide is reduced to a lower oxide. These lower oxides rapidly reabsorb oxygen from the air, becoming again converted into hyclrated dioxide, which, in its turn, yields oxygen to the organic matters present in the water. Thus the manganese acts as a carrier of oxygen from the air to the impurities in the water, oxidising or burning up the latter, and then again becoming revivified by the atmosphere. Manganese also exerts a preventive influence on the growth of organisms, the 162 ♦ KNOWI.EDGE - [Aug. 22, 1884. result being that the charcoal, purified by the treatment, and increased immensely in oxidising power by the carrying action of the manganese, ads better and lasts longer than wiy ordinary charcoal could. This was proved by one of the early experimentdl filters of manganous-carbon, which ran for two years with ordinary water, and then, on taking to pieces, showed the charcoal perfectly sweet, and with no objectionable appearances under the microscope. The organic impurities had evidently been burnt up, not simply separated by straining: in the latter case, they would have remained in the charcoal." . . . "Manganous- carbon has a developing or increasing power of agency, and improves greatly after short use, as the lower man- ganous oxides gradually assume a flocculent and highly active peroxidised condition. The activity then remains for a long time unchanged, depending, of course, much upon the quality of the water." It will be gathered from the above that the block is kept perpetually sweet and clean, by exposure to the influence of the atmosphere, and upon this depends the advantage to be gained by the use of manganous-carbon. Two blocks are supplied, if desired, with each filter, so as to allow of a weekly or fortnightly change for purposes of aeration. Type III.— The " Silicited-Carbon Patent Movable Block Filter," as its name implies, is also constructed ■upon the "block " principle, and finds a place here, because it too has survived the severe oideal to which filters are subjected now-a-days. All the working i)ans of the filter «i8e arc made of stoneware, and are hence incorrodible ; the tap is placed on a level with the lowermost stratum of the reservoir, and the entire apparatus admits of being taken to pieces and easily cleansed. The mechanical details of these filters may be readily understood by a reference to Fig. 2G. It may be observed that in Fig. 26, A, the direction of the passage of the water through the Vig. 2G.— The SiUoated-Carbon Movable Block Filter. A. Longi- tudinal Median Section. B. Interior view. Wock is indicated by a series ot arrows ; this is caused by the novel construction of the block itself, the top and •ed'Tcs of which are made ot non-porous material, so that the water is forced to pass through a maximum amount of the carbon. Toe block, moreover, is bolted down on to an asbestos seating, which is made to form a water-tight joint. The company have informed us that — " SUicated Carbon is an admixture of carbon, iron, silica, and alumina in ascertained proportions ; the carbon being Torbane Hill mineral, from which the oil has been abstracted." Pro- fessor Wanklyn states* that his confidence in the filter is such, that he has passed a solution of strychnine through it, and then drank the filtrate. His explanation ot its action vs. as follows : — " It is an energetic oxidising process, very like the action ot the strongly alkaUne solution of per- * The Echo, Aug. 9, 1881. manganate with which we are in the habit of boiling the nitrogenous organic matters in drinking-waters. Just as by working the ammonia process we make the nitrogenous organic matter contained in water yield anmionia, so the Silicated Carbon Filter breaks up nitrogenous matters and makes them yield ammonia. In fact, it is possiVjle to work the ammonia process ot water analysis by means of a Sili- cated Carbon Filter, instead of the b liling alkaline solution of permanganate of potash.''* Its lead-removing property has been commented upon by Dr. Bartlett and others, and experiments have shown that it even softens water to an ap[)reciable extent. BRITISH SEASIDE RESORTS, FROM AN CNCOKYENTIONAL POINT OF VIEW. By Percy Russell. III. PASSING from Bangor, famous for its slates and the tombs of veritable Princes of Wales, with its long crooked streets, in a fertile valley, guarded by steep heights, and proceeding eastwards, we reach Conway, the historic s-eaport of Carnarvonshire. Here can be studied some fine examples of ancient municipal fortifications, and the Castle is allowed to be the finest example of such structures in Great Britain. Some of the walls are nearly four yards thick. A " sight " of this place is the Plas Mawr, i.e , the Great Mansion — a stately pile dating from Elizabeth, and most curiously adorned without and within by heraldic devices. Conway contains the tomb of the Great Llywelyn, and to Welshmen is on that account a sacred city. The river is here, at spring-tide, full half a mile wide, and from the days of the Romans has had a rejjutation for pearls. The coast now takes a sharply northern direction, and brings us to one ot the nineteen great headlands of England and Wales, Great Orme's Head. This striking natural feature lies about five miles only north east of Conway, and is an immense mass ot liraistone rock, rising t > a height of nearly 700 feet, and surmounted by a lighthouse. East ot this remarkable feature of the coast is Llandudno, with its soft airs and fine bathing, and passing Abergele and Rhyl, and still working eastward, we now reacli the noble tidal estuary of the river Dee, which the ancient Britons', by the way, regarded as a sacred stream. The estuary ot the Dee is nine miles long, and at seasons full six wide, and is hallowed to the students of Milton as the fatal shallow where " Lycidas," or, in plain English, Mr. King, the friend of the poet, sufTered shipwreck and death. Parkgate, little known to the ordinary tourist, is a small watering-place competing with the better-known ^Mersey resorts for visitors from Liverpool. No purer air can be found in England than that blown over the beautiful Dee and down from the Welfh hills, while the lovely scenery of North Flintshire and the splendid expanses ot the estuary here give Parkgate a strange charm for all who love Nature in her pict'ire-que phases. At times, indeed, and especially at low water, the estuary becomes in great part a vast waste ot s-ind and ooze, and then aptly enough reminds one of the dirge-like song in Kingsley's famous Chartist novel or political pamphlet — Oh, Mary, go and call the cattle home, Across the sands of Dee. Seen, however, with the tide in, the estuary is a grand * In a paper read before the " British Medical Association," at Sheffield. Aug. 1884.] KNOWLEDGE 163 oxpanse, and fit for the haven of commercial fleets. This was, I believe, the Seteia iEstuarium of Ptolemy. About a ceDtiiiy fand a h;ilf since the Dee from Queenferry to Chester was embanked, and thereby the agricultural area of these ii-lands gained about 50,000 acres. For persons of true pedestrian tastes, a ramble from Parkgate to Hoylake along the high ground parallel with the coast here has greac charms, and in the vicinity may be seen the favourite resorts of many of the merchant princes of Liverpool. Birkenhead — which originated in a Benedictine Priory of the twelfth century, possessing the importatit monopoly of the ferrits over the Mersey — is a place of commerce, and in its present aspect in no way resembles the Berkin de Birchen of Edward III. Then one vast, beautiful forest extended in leafy luxuriance from the Dee to the Ribble, and thus amply justified an old local distich — From Birchen haven to Hiltre A squirrel might hop from tree to tree. The shores of the Dee, by the way, are memorable as the place whence the English freelances and other worthies of the feudal time used regularly to set out for excur- sions to Ireland — excursions which, doubtless, sowed the fatal seeds of nineteenth-century Fenianism. Traversing the coast at Bidston Hill is the historic Liverpool Observatory. I say historic, for here all the chronometers go to be regulated, and the equatorial of twelve feet focal length and eight and a half inch aperture, with other special scientific appliances, are worthy tobeduly chronicled — more so than the doings of many of the iron- clothed gentlemen who found these remote shores a good place for rendezvous when on spoliation bent. From the lighthouse here a magnificent view can be had both of the estuaries of the Dee and of the Mersey, of Liverpool, that lordly seat of British commerce ; of Birkenhead, Seacomb, Hoylake, Flint, a long and grand expanse of distant Welsh mountains, and, nearer to the gazer by far. New Brighton, which is just a pretty medley of seaside houses and hotels standing on a sandy promontory north of Birkenhead, and commanding extensive and lovely views of the Irish Sea. The lighthouse here is constructed of Anglesea granite, and cemented with a peculiar volcanic substance, brought, I am told, from Etna, and possessing the useful property of hardening more and more with the lapse of time. One place on this coast must not be overlooked, that is Leasowl Castle, a singular quaint erection near a shoal known as Mookbeggar Wharf. This spot is associated with a racecourse, and as long ago as 1593 races were run here, and it was about then that Ferdinand, Earl of Derby, built Leasowl as a sportsman's lodge. It is said that the unfor- tunate Duke of Monmouth was prominent in one of these races in 1683, and once on a time Leasowl was quite a centre of Lancashire fashion. Although the magnificent forests which once clothed these shores in such sylvan beauty have long since perished, ample traditions thereof remain in the neighbourhood, and in the hall at Leasowl are preserved specimens of the Cervus elephas, not to speak of fibuhe and rings which silently remind us of the grandest civilisation of the Pagan world. We now enter the region of the great Pennine range, that vast expanse of lofty moorlands and enormous masses of hill and mountain stretching south of the famous Cheviot hills. These ranges lie much nearer the Irish Sea than to the North Sea, and reach considerable altitudes — Cross Fell being 3,000 ft. ; Mickle Fell, 2,591 ft. ; Whern- side, 2,41-1 ft. ; and Ingleborough, 2,373 ft. above the sea level. The Cumbrian group of mountains lie in the west of the Pennine Chain, which is, in a manner, continued right down to the Cornish highlands, and is bound to the main range by lofty moorlands, beginning near Whernside. These moorlands dip and form the striking pass of Shapfell — the commercial road between all West England and Scotland — and north of Sliapfell is the broad and beautiful valley of the Eden, ending in the famous estuary of the upiier portion of the Sol way Firth. Southward is the narrow estuary of the River Lune, on which stands Overton, whose inhabitants have become celebrated through their quaint petition, that, being surrounded by the sea twice every twenty-four hours, they might have a minister of their own instead of being obliged to go to Heysham. The Lune, which gave its name to Lancaster, doubtless, as antiquaries tell us, the Lengovicum of Roman days, flows into Morecambe Bay, one of the most beautiful indentations of the whole English norih-west coast. Inland, within the wild and picturesque region bounded by the Lune on the one hand and the Sol way Firth on the other, soars up in great grandeur a compact and somewhat circular mass of mountains, preci- pitous in general upon their northern and western faces, but subsiding gently to the wide sweep of Morecambe Bay in long and easy declivities. From the centre of this group, which imparts such a distinctive and romantic character to the north-west of England, there soars up the " mighty Llewellyn " (3,118 feet) as Scott calls it. Then there is the famous Skiddaw (3,054 feet), embalmed in the somewhat obsolete poetry of Southey, and Scafell, already mentioned, the loftiest peak in all England ; and southward the hills slope away into the sea in the picturesque penin- sula of Furness. Within, of course, is the great series of lakes, but with these I have here no concern. Returning to the shore I note that on the pretty penin- sula formed by the mouths of the Lune and the Cocker may be seen the ruins of Cockersand Abbey, once occupy- ing the third place among the proud array of Lancashire monasteries, and, subsequently to the Reformation, falling into the possession of the Dalton family, who raised a whole regiment of cavalry for the service of Charles I. All along the coast, or but a little way inland, are to be found objects of great interest to archMologists. Morecambe Bay receives the waters of the Lune, the Keer, the Winster, the Kent, and the Leven rivers, and is set in the midst of some of the very finest scenery in these islands. The coast is remarkable for its very picturesque sinuosities, and is characterised by its many lovely valleys, its noble parks, and in many cases rich woods, that come down to the very .shores. The towns on or near the coast are mostly ancient, and all are rich in historic associations and generally abound in archaic remains of great and enduring interest ; and in few, if any, regions of England are such truly picturesque villages to be found. When the tide is out the enormous stretches of sand form an extensive plain which, in olden days, was traversed by the famous "Over sands" coach running from Lancaster to Ulverston. But the route was always perilous, con- sequent on the shifting nature of the sands and the action of the rivers flowing into the vast Bay. In one churchyard alone are the graves of over one hundred persons drowned while attempting, at dangerous seasons, the passage of the alluring but treacherous sands ; and many are the legends current in the locality of hair-breadth escapes and romantic episodes connected with the far-stretching Bay. The rail- way constructed across the bend of Morecambe Bay ranks high as among the most remarkable achievements of modern engineering science, and was beset with extraordinary difficulties. The works are a monument of the genius of Mr. Brunlees, and have resulted inter alia in restoring land to agriculture where for generations fishermen cast their nets. The whole region abounds in places of interest, 164 ♦ KNOWLEDGE ♦ [Aug. 1884. but for tlie greater part these are but little known, popu- larly speaking, in soutliern England. The fishing-villages on some parts of the Lancashire coast are remarkable for the utterly primitive habits of the inhabitants, and for the large quantities of flounders and shellfish here taken. All along the wild shores of this beautiful region may be seen the picturesque lime- stone cliffs, mingled with hanging woods, peaceful-looking, fresh grassy mounds, and far away in the grey distance are the lofty mountains and elevated moors — virtually unin- habited stretches of country, swept by perfectly pure and fresh breezes, and equally refreshing to body and mind. Barrow, the port whence the famous iron ore of the Furness district is shipped, lies on the coast of the penin- sula, and is opposite a little island which tradition tells us was once a burial-place for the Nor.se Sea Kings. Until 18i7 this place was only a small fishing-village, having barely 300 inhabitants, but in 1875 it had increased to 40,000, and now the docks and the various iron and steel works render this town one of the great sights on the Lancashire coast. Furness Abbey gives in its remains the finest examples extant of medireval ecclesiastical architec- ture. It was formerly one of the most powerful of the great religious establishments of England, before, as Scott tells us, the ire of a despotic kind made altar shake and crozier bend. The landed property of the abbey once included the entire promontory on which it is situated, and extended to the river Duddon, whose beauties Wordsworth has crystallised for evermore in some of his exquisite sonnets. This domain was about equal to the area of the Isle of Man, and the Abbey could, and frequently did, send over a thou- sand regular troops into the field, sending, by-the-by, a large contingent to Flodden Field under Sir Edward Stanley. On the hill commanding the Abbey there was formerly a beacon, and thence alarm fires were flashed right across Morecambe Bay as far as the grim towers of Lancaster Castle. The Abbey has a very fine transept, and many very interesting monuments, and for full four centuries these proud and lordly representatives of what was emphatically a Church Militant held imperial sway far and wide. The last abbot was, if I mistake not, Roger Pyle, who surrendered his authority to Henry VIII., and thenceforth all the material pomp and circumstance of these lordly priests went to decay. For the last three centuries the rooks have occupied the ruins, which have been preserved from further decay by the Duke of Devon- shire. These i-emains furnished subject-matter for one of Wordsworth's many fine examples of what may be called topographical poetry, and no one can stand amid these magnificent ruins without feeling some emotion, some touch of that fine sympathy with the past which imparts to every ruin its true pathos. The Furness District, once the boundary between the Kingdoms of England and Scotland, and the scene of many a tough border scuffle which has found no historian, may be described as in some measure all mountain, and it was in these stern and natural fortresses that the ancient Britons lingered for two centuries and a quarter after the Saxons had obtained the mastery everywhere, except in Wales. Straightaway due west of the mouth of the romantic River Duddon is the Isle of Man, its southern extremity being in a line with Walney Island, at the enti^ance to Morecambe Bay. Before, therefore, entering the Solway Firth, and proceeding, as I propose doing, up this wild coast and among the wilder islands of Scotland on the west, I shall rapidly sketch this i-emarkable island, which, as it richly deserves, is becoming more and more a place of resort for those who desire to be personally familiar with the less known seascape beauties of the British Isles. eiritorial (gossftp. The well-remembered words of Virgil, " Uno avnlso, non deficit alter," have had no more literal applicability in recent days than to the succession of shows at South Ken- sington. With the Health Exhibition in the very height of its popularity ; with its innumerable forms of restaurant perennially mobbed by customers ; with the instructive popular archteological lesson conveyed by the admirable model of Old London, daily and hourly being learned by the thousands who throng it ; with the exhibition of historical costumes scanned by a perpetually densely packed crowd ; with the third-rate Cremome at night in the gardens, where 'Arry smokes his cheap tobacco and Jemimarann exhibits her fringe, her long gloves, and her box-pleated skirt ; with the dairy cows in f uU milk ; the sweet-stufT and candle-making machinery in full work ; with the bands playing, the lamps twinkling, the steam-boilers hissing, and the dynamos whirling — already is the note of preparation in the air, and the prospectus of the International Inventions Exhibition in 1885 lies before me as I write. Reading through it, it seems as though the bazaar element, so obtrusive in the present show, will be — or rather may be — to a certain extent, modified ; and that the Exhibition may possibly assume a more strictly scien- tific character than the present one. It cannot, however, bs lost sight of that the Commissioners of the '51 Exhibition have now become as much showmen as Mr. P. T. Bamum, Mr. Hollingshead, or Madame Tussaud. If turning their buildings into a series of railway refreshment-rooms, or lighting their gardens with "10,000 additional lamps" pays, they will furnish the buffets, stick up the little marble tables, and light the lamps. They are merely trying to justify their raison d'etre, and have hit upon periodical shows as a good device for giving employment to the officials on their estate and of making money. If money can be made by science, all well and good ; if not, well, a slight soupcon of the Bartlemy-fair element obviously proves attractive. The present " glorious weather " (to employ the phrase- just now in every one's mouth) brings us once more face to face with the wholly inefficient means we possess in this country for meeting the somewhat violent extremes of temperature to which we are subject Adapted, perhaps, best to the average warmth of an English spring or autumn, a very severe winter, and perhaps even more conspicuously an abnormally hot summer, shows the weakness at once of our domestic architecture and of our orthodox type of dress. That any human being should disport himself in a " pot " hat and black cloth coat with the thermometer registering 15-1 Fahrenheit in the sun, must seem almost incredible to any one who does not daily see the un- numbered thousands so attired who throng the streets of the metropolis. But the cult of Mrs. Grundy among Englishmen is so earnest and sincere that the average Londoner would about as soon think of carrying a Punch's show through St. James's-square, or of wheeling a barrow full of periwinkles down Bond-street, as of appear- ing in either of those localities in a " khaki " suit with a pith hat and " puggree." And what applies to our attire may be equally predicated of our contrivances — or, rather, \itter want of contrivances — for keeping our houses cool. Why does not some enterprising tradesman devise something akin to the Indian " tattie," and furnish us with a sun- blind constructed to be kept wet The delicious coolness produced in the air by the rapid evaporation from such a device must be felt to be appreciated. Nay, even a modi- Aug. 22, 1884.] ♦ KNOV/LEDGE 1G5 tication of the familiar punkah would not be without its pleasurable use oa such a clay as that on which these lines are penned. Will no one render us aid before we get into the condition so feelingly described by the negro, when he said that " it couldn't be no hotter in our house, for de termometer 'as got bang up to de top, dat's one comfut ! " 1 i¥licv. Wm. Anderson, 48, Pulteney-street, Bath.] Sib, — Among the persons whose lives and labours have ennobled the city of Bath, none stand so high in force of character, in difficulties overcome, and in magnificent services rendered to science as William Herschel and his scarcely less distinguished sister and fellow labourer Caroline. Herschel was great as a thinker, a worker, a philosopher, and, above all, a discoverer. In- ferior to Newton as a philosopher, he was greater as an astronomer. Arago was astonished by " his extraordinary success as a dis- coverer." Judged by the diflficultics which he overcame, as well as by the actual additions which he made to human knowledge, by the instruments which he invented and bequeathed to future dis- coverers, and by his prescient anticipations of the future triumphs of science, he was by far the most distinguished citizen who ever lived in Bath. During the sixteen most fruitful years of his life — from 17C6 to 1782, i.e., from his 2Sth to his 42nd year — he resided in Bath, as organist of the Octagon Chapel and director of the public concerts. He frequently composed anthems, chants, and whole services for the choir under his management. Music was the business, astronomy was the amusement of his life. Before he made the discoveries which have given him an immortal name, he had to bring to completion, by a series of labours of almost incredible industry and perseverance, sometimes extending to sixteen hours of continuous work, the instruments of discovery. He erected a furnace in his garden, where he and his brother worked for months of almost incessant toil, and made hundreds of specula before he completed the great reflector through which he discovered the planet Uranus, on the 13th of March, 1781. His illustrious sister read to him while turning the lathe or polishing the mirrors. Subsequently, after he had been invited to Windsor, he said, ''I would rather be polishing a speculum than at Court." Then he found that the telescope which he and his sister bad con- structed was superior to anything in the Royal Observatory. He discovered the motion of the solar system in space. He mapped out all the double stars ho met with. He first discovered the lunar volcanoes.* He constructed a telescope of 40 ft. focal length and 8 ft. aperture. In the words of his biographer, in the last number of the Encyclop(Edia Britannica, '* He demonstrated the action of the same mechanical laws among the distant members of the starry firmament which bind together the harmonious motions of our solar system. This sublime discovery would of itself suffice to immortalize his memory in the respectful homage of all future races of intelligent men." In him there were combined — each in its highest form — the attributes of the artisan, the artist, and the astronomer in a degree so highjand employed for purposes so noble, that few cities can point to a citizen so noble and so worthy of lasting remembrance. I have been requested by the committee of the Octagon Chapel, in which the organ associated with the name of Herschel still remains, to write this letter, in the hope that their efforts to put up in the chapel a memorial window not unworthy of its distinguished organist may be aided by those of our fellow-citizens who desire to honour an illustrious name and transmit a memorable example. William Anderson'. LETTERS RECEIVED AND SHORT ANSWERS. T. R. Clapiiam. Does your sketch of a flash of lightning represent the appearance it represented to the naked eye, its track through the ground, or what ? — Galvanises. No. — T. McIlveme. Probably the situation of assistant in the Science and Arc Department, or in the British Museum, would be one as congenial to your tastes a3 any; but either would involve a pretty severe competitive examination. There is no profession or occupation outside of such subordinate Government appointments as these, in which you can be<,'in to earn anything for many a long day. — Qiiham. Your mistake lay in writing a second time for an explanation. Such articles are merely used as "padding" in a daily newspaper, and may lie unused for an indefinite time. I have seen one of my own appear after a lapse of twelve months ! An editor (like the Captain of one of her Majesty's ships) must, ex necessitate, be an autocrat ; and, according to the usages of journalism, you have nothing whatever legitimately to complain of. — James Gillespie. Will you be good enough to read my replies to you on pp. 40 and 70. I neither will nor can answer correspondents prirately through the post. — M. asks how distemper painting is practised, the colours required, where they are to be obtained, and the ground used, for painting on. He further wishes to know whether the process might not be employed in painting landscapes from nature, it being alleged that J. M. W. Turner so used it. Pending any detailed reply with which he m,ay be favoured by some brother reader, he may get some hints from Godwin's "Art of Mural Decoration," published for a shilling by Winsor & Newton. — Con Spikito. There cannot be the slightest doubt that when a table moves in a oona-jide experiment such as you refer to, it does so through the unconscious muscular action of the operators. At the time when table-turning became a fashionable craze, our great departed Physicist Faraday devised a simple piece of apparatus, by the aid of which any pushing action on the part of the experimenters was at once rendered visible by the motion of the long arm of a lever. When the top and bottom parts of this simple contrivance were rigidly connected (so that the arm was a fixture) and the hands of the persons sitting about the table were placed upon it, the table went round merrily. The moment, though, that such connection w.as broken, so that a push on the top plate of the apparatus caused the arm to move, the pei-formers had ocular demonstration, by its swinging round, that they were (wholly unconsciously) themselves pushing; and, their attention being thus directed to it, ceased to do so; the inevitable result being that the table stood stock-still. Thanks for your friendly expressions. — C. J. Pettit. I can find nothing about a tricycle (American or otherwise) in Knowledge for August 8. See con- cluding paragraph, in capital letters, at the head of Correspondence Column. — C. E. Parkek-Rhodes. Received too late. Thanks. — H. RoMEiKE. I am much obliged ; but the needs of a scientific journal scarcch- include such paragraphs. Errata. — In column one, p. 130, line 14 from the bottom, the words " at S', 4 feet from it," should immediately precede " and so on." — In line 17, col. one, p. 145, " for what " should be "for which;" and in line 40 of the same column the word "where" should follow " Cassiopeia." [^ This is erroneous ; but in no sense affects the appeal. — Ed.] 168 ♦ KNOWLEDGE ♦ [Aug. 22, 1884, (JPur Cljfsisi Column* By Mephisto. PROBLEMS BY I. G. No. 124. Black. Whitk. White to play and mate in three moves. Hi W£'^m i ^^ ^^ ^M Whttb. White to play and mate in three moves. 1. Kt to KB3. This first move leads to a close opening, pro- ducing a very safe game for White. The opening is remarkable for an entire absence of combination leading to any direct line of play. The player is soon thrown upon his own resources, and he has to sti-uggle for position. This kind of game is specially adapted for match play between strong players, as it requires first class judgment and experience to conduct these subtle wrangles for position in which minute advantages are gained, which, if properly followed up, lead to a winning advantage for the End game. Weaker jilayers not having sufficient judgment, miss the subtle points in this opening, which then becomes dull and featureless, but always affording a comparatively safe game to the first player. The opening affords but very poor practice for young players, who ought to adopt lively and attacking debuts, as by undertaking such attacks and defences they will gradually gain experience and a deeper insight into the game, they will also derive much pleasure from such practice, which after all is the main object of Chess play. The effect of 1. Kt to KB3 is twofold— to prevent P to K4, also to enable the first player to avoid the French defence. If Black plays 1. P to Q3 with the object of playing 2. P to K4, White will gain an advantage by playing 2. P to Q4, or he may play 2. P to K4; and if 2. P to K4, White may reply as in the Philidor defence by 3. P to Q4 with advantage. It in reply to 1. Kt to KB3, P to QB4, the same as in the Sicilian defence. White can at once play 2. P to Q4, and the QP will be weak, 2. P x P. 3. Kt x P, P to K4. 4. Kt to Kt5, i-c. 1. P to QB3 may be played, but the best replies are 1. P to K3 and 1. P to Q4. It is not desii-able to play 1. Kt to QB3 as it is Whitb. requisite to play P to QB4 later on, to counteract the advance of White's centre Pawns. Having stated sufficiently to indicate the import of 1. Kt to KB3, we will proceed to the normal variation arising out of that move : — 1. Kt to KB3, P to K3. 2. P to 04 P to Q4. 3. P to K3, Kt to KB3. 4. P to QKt3, B to Ki' 5. B to Kt2, Castles. G. B to K2, P to QKt3. 7. P to QB4 B to Kt2. 8. Castles, P to QB4. 9. Kt to B3, Kt to B3. 10. R to B sq., R to B sq. 11. Kt to R4, Kt to E4. In this opening, the player who is too soon compelled to change Pawns, is at a disadvantage, as the opponent, by retaking with Pawn, obtains a commanding position. If 13. P x BP, PxQP. 13. BxKt, PxB. 14. PxP, P X P. 15. Kt to E4, threatening B to Kt4, B to B5, and Q to H5, &c. If in reply to 12. P x BP, B X P. 13. P X P, B X P. 14. Kt X B, isolating and weakening the BP. If Black, on his 11th move, instead of Kt toR4 plays Kt toK5, then 12. Kt to Q2 still threaten- ing to win the BP by P x KP. We must now come to consider the various deviations from this line of play by which Black seeks to avoid this knotty position. For that purpose we quote Blackburne's method of posting the P on QB3, playing the Kt to Q2 and B to Q3, viz., 1. Kt to KB3, P to Q4. 2. P to Q4, P to K3. 3. P to K3, Kt to KB3. 4. B to Q2, Kt to Q2. 5. P to QKt3, B to Q3. 6. P to B4, P to B3. 7. Castles, Castles. In this position, which of course may be arrived at by various transposition of moves, Black is ""^^ somewhat confined. His inten- tion is to play B to Kt sq., but we doubt whether any attack need be feared on the K's side, as P to KKt3 is always available. White, when opposed to strong l>lay, not wishing to incur any risk, may plaj- B to R3, compel- ling the exchange of Bishops. White may also play B to Kt2 or Kt to QB3. The latter move may lead to complications nnfavoui- able for White, for if Kt to K5. Kt X Kt, P X Kt, Kt to Q2. P to B4, White cannot play P to B3 now, on account of Q to R5. It seems that when Black does not play P to QB4 but P to B3, then the White B is better placed on Q3. White may arrive at the same position by playing as his first move either 1. Kt to KB3, P to Q4. P to QB4, P to K3, &c. ; while he may vary his moves considerably, Black has to be careful to answer correctly. We think we have given the leading principle of this opening. Endeavour to develop all the pieces and to support the QP and QBP until the position is ripe for an advance on the Q's side. White must meet deviations in a careful manner, guarding against exposing his game or attacking prematurely, and he will always obtain a fairly developed and safe game. 1 / " «#3, i k ^^ i $ t White. SOLUTION. Problem No. 122, p. 124. 1. R toB4 BxR, or 2. K to Kt5 Any 2. Q to Kt4 3. Q to KR sq. Slate 3. Q x P If B to B3. 2. B X B and mate next move. If K to B5. 2. Q X P and mate next move. " Well constructed and somewhat difficult." BxB K to K4 Mate ANSWERS TO CORRESPONDENTS. #*, Please address Chess Editor. Correct solutions received. — Problem No. 122, Geo. Thompson, W., A. W. Overton, J. K. Milne. No. 123. John Watson, Geo. Thompson, C. T. G. Aug. 29, 1884.] ♦ KNOV\^LEDGE - 169 Pi^ MAGAZINE ofSCIENCE AINLYWORDED-EXACTLYDESCmBED LONDON: FRIDAY, AUG, 29, 1884. CoirrKNTs OP No. 148. PAOS Next Year's Eshibition. By In- ventor 1 69 The -Entomolo^ of a Pond. {Jilus. ) By E. A. Butler 170 The Physics of the Earth's Craat. By R. A. Proctor 171 The Chemistry of Cookery. XLI. Authorities on Tea and Coffee. By W. Mattieu Williams 172 The Electro-Magnet. {Illu$.) By W. SUngo 173 The Earth's Shape and Motions. III. The Annual Motion of the Son and StarB. By R. A. Proctor 175 PAGB Got Supply of Coal 176 A Practical Method of Eatimating Distances. (lilus.) 177 Pleasant Hours with the Micro- scope, (niu^.) By H. J. Slack . 179 Photograpby for Amatetirs ISO Editorial Gossip 182 Face of the Sky. By F.R.A.S 182 Reviews 183 Miscellanea 18-t Correspondence : Sunflowers — I<» Tea Injurious?— Small-Poi and Vaccination — August Meteors, &c. 185 Cor Chesa Column 183 NEXT YEAR'S EXHIBITION. By Inventor. THE operations of exhibitions are very manifold. Primarily, I suppose, they are intended for educa- tional purposes, to show people what advances have been made in the development and product of the human intellect. Were this, however, the only purpose they are capable of serving, we should find these now oft-recurring shows attain but very shadowy dimensions compared with what is actually seen. In reality, an exhibition has a more or less distinct business ring about it, and if this element is once lost sight of, the fate of the show is almost in- fallibly sealed. Much was said and done to give backbone to the greatest educational effort ever put forth in this direction, viz., the Loan Exhibition of 1876. It was a grand display — such a one, perhaps, as will never again be seen ; it was purely educational ; the business element was conspicuously absent, and consequently, although not so decided a failure as some, it cannot be said that the exhi- bition was a success, particularly when compared with that which has been achieved by more recent shows. A similar fate attended the Exhibition of Electrical Apparatus at the Albert Hall. The Paris Exhibition of 1880-1, and the Crystal Palace Exhibition of lSSl-2, regarded electricity as a marketable something, and suc- ceeded— that is to say, they paid their expenses and left a balance, stimulated trade and spurred on scientists as well as unseientiiic inventors to produce something even better than the best then producible. And these I take to be some of the main points to be regarded in estimating the measure of success accomplished. It follows by implication that for an exhibition to succeed, not only must the guarantors be relieved of all anxiety so far as the claims upon their pockets are con- cerned, but the exhibitors must see a prospect of recouping themselves. To collect and adorn a case or stand of com- modities more or less novel, to print circulars, to pay the cost of packing, of carriage and fixing, i-c, involves no small expense, which, if there is little or no prospect of business, the would-be exhiliitor is not likely to incur. And why should he ] Are we to suppose him to be endowed with a greater share of self-abnegating philanthropy than the rest of maukind ? It is all very well for a wealthy or independent man to exhibit his hobby, or for a traveller to display his collection of curiosities ; but, if we waited for a sufficient number of such enthusiasts, 'we should be compelled to wait for many a year, and then, doubtless, we should only succeed in getting together such a motley collection as would please nobody, not excepting even the exhibitors themselves. The man of the world, the man of business, knows full well that a show which is purely educational will have little attraction for the great majority of people, and it is only by the drawing together of great crowds, and entertaining and interesting as well as instructing them, that he can hope to defray his expenses and pay himself for his trouble. Would it were otherwise ; but we must take people as we find them, and this I take to be the main feature which, though perhaps never formulated, aflfords excuse for the general plan adopted by the executive councils of the present Ken- sington exhibitions. There are, of course, some points we might feel disposed to find fault with ; they are so far too superficial, and pos- sibly offer too many facilities for airing the obtrusive peculiarities of certain people ; but we should be unjust were we to blame the working class for not being wiser or more cultured than they are. Maybe the fault rests more with the teachers. Indeed, it is to remove as much of the existing ignorance as possible that Knowledge is issued week by week, and we are fond of regarding the pages of this journal as among the educational influences of the day The mere show of articles of every-day consumption i?, however, little calculated to educate, or even to interest, the beholders, and can only find excuse from an advertising standpoint. Such displays are, in fact, outside the business region of my purview. The coming Exhibition of Inventions and Musical Instruments promises to be of such a nature as to satisfy the hungriest searcher after knowledge, while, at the same time, business people will see in it an opportunity for entering into competition with the keenest energy. Those also who will visit it for fashion's sake stand a chance of reaping some benefit from it. The field embraced by " inventions " is so extensive that we may fairly and confidently look for an excellent display, in which jam-pots and such like impedimenta will scarcely find a place. The scientific element will be more predominant, and there is, in fact, a prospect of its satisfying all sections of the com- munity. Music is doubtless introduced as a kind of leaven. The idea upon which the exhibition is planned is not to bring together a mere collection of models of inventions, but rather to illustrate the progress which has been made in the practical application of science during the past twenty years. In order to carry out this intention, the council will, as far as possible, confine the exhibits to pro- cesses and appliances, products being admitted only where they are themselves novel, or where their introduction is required to make the purpose or advantages of that which is new in any process more interesting and intelligible. It is not proposed to allot space for manufactured goods unac- companied by any illustrations of the process of manufac- ture. Generally, it may be said that, as far as is prac- ticable, inventions will be shown by models, with, in the case of models of entire machines, actual specimens of the portions improved under the exhibitor's patent, and when the invention relates to parts only, the whole machine will not be admitted, unless, indeed, the improvement effected 170 ♦ KNOWLEDGE ♦ [Aug. 29, 1884. cannot be sufficiently sliown without the exhibition of the entire apparatus. The limitations of space which make these restrictions necessary, also compel the Council to decline, unless iu exceptional circumstances, to receive objects which have already been shown in either of the recent exhibitions. The second division — music — will, of course, be aiTanged on somewhat different principles. Here the object will be to illustrate as completely and in as interesting a manner as may be all that relates to the development of the science and of the art of music. Examples of musical instruments of a date not earlier than the commencement of the present century, and any machinery, apparatus, or appliances connected with their manufacture or their use, will be admissible. And, further, without restriction of date, contributions to an historic collection of musical instruments, and paintings and engravings representing musical subjects, are invited, and many, it is known, will be forthcoming. Criticism at this early stage is practically out of the Question, but the Council includes such a phalanx of good men (Sir Frederick Bramwell, F.R.S., vice-president of the Institute of Civil Engineers, Sir Frederick Abel, C.B., Mr. I. Lowthian Bell, F.R.S., president of the Institute of Mechanical Engineers, Colonel Sir Francis Bolton, Professor Dewar, F.R.S., Sir George Grove, D.C.L, Mr. W. H. Preece, F.R.S., Sir E. J. Reed, M.P., F.R S., Professor Chandler Roberts, F.R.S., Dr. Stainer, Mr. R. E. Webster, Q.C., &c.), that there will, I fancy, be little to iind fault with. One thing is very certain, and that is, that the Exhi- bition will be one from which excellent results may, and most assuredly will, be looked for. The first division will be divided into some thirty or thirty-one groups, and single specimens of the objects mentioned in the prospectus would in themselves constitute a show of no mean proportions. We hope, naturally, for something more than this. Practically, every branch of human in- dustry is taken up — and, indeed, it is almost a matter of impossibility to conceive how any one thing could be regarded as outside the scope embraced by the title. It follows that there will be whole multitudes who will visit the Exhibition, and who will leave it minus that benefit which they ought to derive. It will be the duty of Knowledge to help its readers to grasp more truly the lessons to be learned from what we have no doubt will be a great and a highly interesting exhibition. Such exhibits as may be likely to prove beneficial to the community will be referred to, and described more or less fully, sight not being lost of the fact that while many of our readers may be able to view the objects themselves, many others, pos- sibly the majority, will be debarred for various reasons from ever visiting the Exhibition. THE ENTOMOLOGY OF A POND. By E. a. Butler. THE BOTTOM (continued). THE Eanatra linearis is a creature of three elements, though, of course, its proper sphere is the water. It can manage to progress on land better than most aquatic insects, carrying its body high up on its stilt-like second and third pairs of legs ; still, its movements are, at best, but slow and awkward. It will also, sometimes, take to the air, and on returning to its pond, finds occasionally a little difficulty in re-entering the water, on account of its own slight specific gravity and the dryness ^ legs, but still similar in plan to Ranatra, |w7\ \ which it resembles also in its brilliant scarlet body. It is a most sluggish insect, and can easily be secured by the hand when seen near the edge of the pond ; but the diffi- culty is to catch sight of it, for so exactly similar is its colour to that of the mud amongst which it lies, that unless the ob- server can bring to bear upon it a pair of keen and well-trained eyes, it will in nine cases out of ten remain undetected, if only it have the sense not to betray its presence by moving. In consequence of its sluggish habits and mud-loving pro- pensities, it sometimes becomes covered with an incrusta- tion which does not render its detection any the easier. Its protective coloration, no doubt, gives it chances of many more meals than it would otherwise get, for unwary insects will often approach near enough to come within range of the hooked fore-feet without being conscious of the risk they run, and are only aroused from their fancied security by finding themselves suddenly clutched and pressed in a deadly embrace against the sharp beak which is ever in waiting to tap any juicy body that may be presented to it. The breathing apparatus is a marvel of complexity ; there are both spiracles and tail filaments, the latter lead- ing into the two longitudinal trachea?, which run parallel to the sides. From these, innumerable minute tubes ramify all over the body, and if only it were possible to dissect out the whole tracheal system, and separate it from the rest of the body, it would form a most elegant object, and appear like an exquisite network of silver filagree, built up, as it were, upon a gridiron-like framework consisting of two long curved side-pieces connected by arched cross- pieces. In the thorax there are a few dilatations of the tracheal system, in the form of air-bags, such as in many other insects, especially those that are vigorous in flight, may be found in other parts of the body as well. The eggs of Nepa are very peculiar. They are oval, with seven long filaments at one end ; while they are being laid, the filaments of each serve as a sort of cup to keep its successor in position, but when the egg is once de- posited, the filaments bend backwards and form a circlet of recurved hooks. The eggs of Eanatra are more elongate, and furnished with only two bristles. As these water-scorpions are bugs, they do not undergo much change of form in the course of their life ; the larvse are very similar to the adult, the chief differences being the smaller size and the absence of wings and tail-filaments, the place of the latter being taken by a small pointed projection. (To he continued.) THE PHYSICS OF THE EARTH'S CRUST. By Richaed A. Peoctok. PROFESSOR DAVIDSON, of the United States Geodetical Survey in California, has noticed most remarkable deviations in the direction of the action of gravity in the region which he has surveyed. Deflections of ten or eleven seconds of arc — which would corresjiond. in the determination of the position of a place by astro- nomical methods, to errors of 1,000 or 1,100 feet — are common. This shows that the density of the materials beneath the visible surface of the earth is very irregular. But what is remarkable is that the deviations of the plumb-line (so, for convenience, to describe a peculiarity which in reality is far too delicate to be dealt with by a plumb-line observation) are not, as might be expected, towards the great mountain ranges, but towards the regions of depression. It would seem that the depressions indicate the downward tendency of very dense matter, and a resulting closeness of packing, so to speak, which makes those depressed regions exert a very powerful local attrac- tion, causing the plumb-line in their neighbourhood to deviate towards them. On the contrary, in the neighbour- hood of the mountain ranges, and even on their flanks, the deflection of the plumb-line is from the regions of elevation, as though vacant spaces or matter of relatively small density existed beneath the upheaved portions of the crust. Another point, still more remarkable, and apparently established on sufficient evidence, is that in certain regions the direction of gravity seems to have changed largely during a period of less than thirty years. Professor Davidson mentions one place where the position, as deter- mined by astronomical methods depending on the direction of gravity, has varied no less than 16 seconds of arc since 185-1. The arrangement of the masses beneath the sur- face in the neighbourhood must have greatly changed — marvellously, in fact, when the shortness of the time is considered. One cannot wonder that California should be a region of great earthquakes, insomuch that no large building can safely be made of stone in that part of the earth. Prof. Davidson's observations tend to throw some doubt on all such methods of determining the earth's density as depend on variations in the force and direction of gravity in the neighbourhood of mountain masses, at the bottom of deep mines, and so forth. It is certain that had such observations been first made in such a region as California, they would have led to entirely erroneous results, or, rather, they would have failed utterly ; for it appears that instead of the plumb-line being deflected towards the upraised masses (supposed to be of known density), as in the case of the Schehallion experiment, it would have been drawn from them towards masses of compressed matter beneath the lower levels, and before unsuspected. As for pendulum experiments in mines, such as the celebrated Harton Colliery observations, they seem utterly discredited by such observations as Professor Davidson's. But, to say the truth, they have long been regarded as worthy cf little trust. In dealing with Airy's observations (really con- ducted by his assistant, Mr. Dunkin), in Rodwell's " Physi- cal Cyclopa?dia," I pointed out fifteen years ago that the result obtained was altogether unreliable, chiefly because of the uncertainty necessarily existing in regard to the density of the regions surrounding the scene of operations. The result obtained at Schehallion by Maskelyne was more nearly correct, judged by the indications of the Cavendish experiment, the only method which seems really trust- worthy. But what was learnt from the Schehallion experiments was simply that the rock masses in that region are tolerably uniform in structure, and of about the mean density assigned by Maskelyne, not that the earth has the mean density deduced by that observer from his observa- tions there. This last we learn from Baily's experiments by the Cavendish method, in which the earth is weighed against metallic masses of known density. Other observations in California show hov,- little reliance 172 KNOWLEDGE ♦ [Aug. 29, 1884. can be placed on certain results which have been accepted with considerable confidence. Not only does the rate of in- crease of temperature with descent vary greatly in different regions, but in some places the law is reversed. Thus, in the new Almaden Quicksilver Mine in California, the tem- perature is about 115° at a depth of GOO ft., while in the deepest part of the mine, 1,800 ft. below the surface, and 500 ft. below the sea level, the temperature is not higher than 80''. At the Eureka mines, California, the tempera- ture, 1,200 ft. below the sea level, is not higher than it is 100 ft. below that level. — The Newcastle Weekly Chronicle. THE CHEMISTRY OF COOKERY. By W. Mattieu Williams. XLI.— AUTHOKITIES ON TEA AND COFFEE. SINCE the publication of my last I have been reminded of the high authorities who have defended the use of the alkaloids, and more particularly of Liebig's theory, or the theory commonly attributed to Liebig, but which is Lehmann's, published in Liebig's "Annalen," Vol. 87, and adopted and advocated by Liebig with his usual ability. Lehmann watched for some iceeks the effects of coffee upon two persons in good health. He found that it re- tarded the waste of the tissues of the body, that the pro- portion of phosphoric acid and of urea excreted by the kidneys was diminished by the action of the coffee, the diet being in all other respects the same. Pure caffeine (which is the same as theine) produced a similar effect, the aromatic oil of the coffee, given separately, was found to exert a stimulating effect on the nervous system. Johnstone ("Chemistry of Common Life") closely fol- lowing Liebig, and referring to the researches of Lehmann, says : — "The waste of the body is lessened by the intro- duction of theine into the stomach — that is, by the use of tea. And if the waste be lessened, the necessity for food to repair it will be lessened in an equal proportion. In other words, by the consumption of a certain quantity of tea, the health and strength of the body will be maintained in an equal degree upon a smaller quantity of ordinary food. Tea, therefore, saves food — stands to a certain extent in the place of food — while, at the same time, it soothes the body and enlivens the mind." He proceeds to say that " In the old and infirm it serves also another purpose. In the life of most persons a period arrives when the stomach no longer digests enough of the ordinary elements of food to make up for the natural daily waste of the bodily substance. The size and weight of the body, therefore, begin to diminish more or less perceptibly. At this period tea comes in as a medicine to arrest the waste, to keep the body from falling away so fast, and thus to enable the less energetic powers of digestion still to supply as much as is needed to repair the wear and tear of the solid tissues." No wonder, therefore, says he, " that the aged female, who has barely enough income to buy what are called the common necessaries of life, should yet spend a portion of her small gains in purchasing her ounce of tea. She can live quite as well on less common food when she takes her tea along with it ; while she feels lighter at the same time, more cheerful, and fitter for her work, because of the indulgence." All this is based upon the researches of Lehmann and others, who measured the work of the vital furnace by the quantity of ashes produced — the urea and phosphoric acid excreted. But there is also another method of measuring the same, that of collecting the expired breath and deter- mining the quantity of carbonic acid given o£f by combus- tion. This method is imperfect, inasmuch as it, onlv measures a portion of the carbonic acid which is given off. The skin is also a respiratory organ, co-operating with the lungs in evolving carbonic acid. Dr. Edward Smith adopted this method of measuring the respired carbonic acid. His results were fir.st published in "The Philosophical Transactions"' of 1859, and again in Chapter XXXV. of his volume on " Food," International Scientific Series. After stating, in the latter, the details of the experi- ments, which include depth of respiration as well as amount of carbonic acid respired, he says : — " Hence it was proved beyond all doubt that tea is a most powerful respiratory excitant. As it causes an evolution of carbon greatly beyond that which it supplies, it follows that it must powerfully promote those vital changes in food which nlti- matel}' produce the carbonic acid to be evolved. Instead, therefore, of supplying nutritive matter, it causes the assimi- lation and transformation of other foods." Now, note the following practical conclusions, which I quote in Dr. Smith's own words, but take the liberty of rendering in italics those passages that I wish the reader to specially compare with the jireceding quotations from Johnstone : — " In reference to nutrition, we may say that tea increases waste, since it promotes the transformation of food without supplying nutriment, and increases the loss of heat without supplying fuel, and it is therefore especially adapted to the -wants of those who usually eat too much, and after a full meal, when the process of assimilation should be quickened, but j* less adapted to the jyoor and ill-fed, and during fasting." He tells us very positively that "to take tea before a meal is as absurd as not to take it after a meal, unless the system be at all times replete with nutritive material" And, again, "Our experiments have sufficed to show how tea may be injurious if taken v.-ith deficient food, and thereby exaggerate the evils of the jyoor ; " and, again, " The conclusions at which we arrived after our researches in 1858 were that tea should not be taken without food, unless after a full meal ; or with insufficient food ; or by the young or very feeble ; and that its essential action is to v:aste the system or consume food, by promoting vital action which it does not support, and they have not been disproved by any subsequent scientific researches." This final assertion may be true, and to those who " go in for the last thing out," the latest novelty or fashion in science, literature, and millinery, the absence of any refuta- tion of later date is quite enough. But how about the previous scientific researches of Lehmann, who, on all such subjects, is about the highest authority that can be quoted. His three volumes on " Physiological Chemistry," translated and republished by The Cavendish Society, stand pre-eminent as the best- written, most condensed, and complete work on the sub- ject, and his original researches constitute a lifetime's work, not of mere random change-ringing among the ele- ments of obscure and insignificant organic compounds, but of judiciously selected chemical work, having definite philosophical aims and objects. It is evident from the passages I have emphatically quoted that Dr. Smith flatly coutradicts Lehmann, and arrives at directly contradictory physiological residts and practical inferences. Are we, therefore, to conclude that he has blundered in his analysis, or that Lehmann has done so 1 On carefully comparing the two sets of investigations, I conclude that there is no necessary contradiction in the facts; that both may be, and in all probability are, quite correct as regards their chemical results; but that Dr. Aug. 29, 1884.] - KNOAA^LEDGE 173 Smith has only attacked half the problem, while Lehmann has grasped the whole. All the popular stimulauts, refreshing drugs, and " pick- me-ups" have two distinct and opposite actions — an imme- diate exaltation which lasts for a certain period, varying with the drug and the constitution of its victim, and a sub- sequent depression proportionate to the primary exaltation, but, as I believe, always exceeding it either in duration or intensity, or both, thus giving as a nett or mean result a loss of vitality. Dr. Smith's experiments only measured a partial result (the carbonic acid exhaled from the lungs without that from the skin) of the first stage, the period of exaltation. His experiments were extended to 50 minutes, 71 minutes, 65 minutes, and in one case to 1 hour and 50 minutes. It is worthy of note that in Experimeut 1 were 100 grains of black tea, which were given to two persons, and the time of the experiment was 50 and 71 minutes ; the average increase was 71 and GS cubic inches per minute, while in No. G, with the same dose and the carbonic acid collected during 1 hour and 50 minutes, the average increase per minute was only 4 7 '5 cubic inches. These indicate the decline of the exaltation, and the curves on his diagrams show the same. His coffee residts were similar. We all know that the " refreshing " action often extends over a considerable period. !My own experiments on my- self show that this is three or four hours, while that of beer or wine is less than one hour (moderate doses in each case). I have tested this by walking measured distances after taking the stimulant and comparing with my walking powers when taking no other beverage than cold water. The duration of the tea stimulation has been also measured (painfully so) by the duration of sleeplessness when female seduction has led me to drink tea late in the evening. The duration of coffee about one-third less than tea. Lehmann's experiments extending over weeks (days instead of minutes), measured the whole effect of the alkaloid and oil of the coffee during both the periods of exaltation and depression, and, therefore, supplied a mean or total result which accords with ordinary everyday ex- perience. It is well known that the pot of tea of the poor needlewoman subdues the natural craving for food ; the habitual smoker claims the same merit for his pipe, and the chewer for his quid. Wonderful stories are told of the long abstinence of the drinkers of mate, chewers of betel- nut, Siberian fungus, coca-leaf, and pepper-wort, and the smokers and eaters of haschish, ka. Not only is the sense of hunger allayed, but less food is demanded for sustaining life. It is a curious fact that similar effects should be pro- duced, and similar advantages claimed for the use of a drug which is totally different in its other chemical properties and relations. " White arsenic," or arsenious acid, is the oxide of a metal, and far as the poles asunder from the alkaloids, alcohols, and aromatic resins, in chemical classi- fication. But it does check the waste of the tissues, and is eaten by the Styrians and others with physiological effects curiously resembling those of its chemical antipodeans above named. Foremost among these physiological effects is that of " making the food appear to go farther." It is strange that any physiologist should claim this diminution of the normal waste and renewal of tissue as a merit, seeing that life itself is the product of such change, and death the result of its cessation. But in the eagerness that has been displayed to justify existing indulgences, this claim has been extensively made by men who ought to know better than admit such a plea. I speak, of course, of the habitual use of such drugs, not of their occasional medicinal use. The waste of the body may be going on with killing rapidity, as in fever, and then such medicines may save life, provided always that the body has not become " tolerant," or partially in- seu-sible, to them by daily usage. I once watched a dangerous case of typhoid fever. Acting under the instructions of skilful medical attendants, and aided by a clinical thermo- meter and a seconds watch, I so applied small doses of brandy at short intervals as to keep down both pulse and temperature within the limits of fatal combustion. The patient had scarcely tasted alcohol before this, and therefore it exerted its maximum efficacy. I was surprised at the certain response of both pulse and temperature to this most valuable medicine and most pernicious beverage. The argument that has been the most industriously urged in favour of all the vice-drugs, and each in its turn, is that miserable apology that has been made for every folly, every vice, every political abuse, every social crime (such as slavery, polygamy, &c.), when the time has arrived for reformation. I cannot condescend to seriously argue against it, but merely state the fact that the widely- diffused practice of using some kind of stimulating drug has been claimed as a sufficient proof of the necessity or advan- tage of such practice. I leave my readers to bestow on such a plea the treatment they may think it deserves. Those who believe that a rational being should have rational grounds for his conduct will treat this customary refuge of blind conservatism as I do. THE ELECTRO-MAGNET. By W. Slingo. THE experiments referred to at the close of the previous article as having been made by Professors Ayrton and Perry* present many features full of interest and worthy of study. They are all such as may be easily repeated by the student. The object was to determine which mode of winding a given length of wire on an iron bar "ave the strongest electro-magnet for the same current. Four bars of iron, each 12 inches long, were cut from the same rod § in. thick ; and an exactly equal length of wire was wound on the four bars respectively, in the following way : — • Fig. 1 Fig. 2. Fig. 3. 1. Wire wound equally over the whole length, Fig. I. 2. Wire coned towards each end. Fig. 2. 3. Wire wound equally over half the iron bar, leaving the other end bare (Fig. 3). * " Phil. Mag.," Vol. XY., p. 397. 174 ♦ KNOWLEDGE ♦ [Aua. 29, 1884. 4. Wire wound on one half, but coned towards the end (Fig. 4). Fig. 4. To ascertain their relative strengths, electro-magnet No. 1 was put so that its axis was at right angles to the axis of a small magnetic needle and passed through the point of suspension of the needle, which was suspended so as to move freely in a horizontal plane, and far enough away that the magnetic field due to the electro-magnet, when magnetised by passing a current through it, was nearly constant over that portion of the field in which the little suspended needle moved when deflected. A constant current was now passed through the coil, and the deflection of the little needle observed when the electro-magnet was placed at different distances from the centre of the test- needle, the axis, however, always remaining in the same line. Under these circumstances, the strength of the field produced by No. 1 at the centre of the test-needle is approximately proportional to the tangent of the angle through which the needle is deflected. Experiments were made in a similar way with electro-magnet No. 2, and with each end of No. 3 and of No. 4, the same current being used in all cases. TANGENT Or OErLECTlQN OF NBtDLE The results obtained are shown plotted in the accompany- ing curves (Fig. 5), vertical distances representing the dis- tance between the near end of the electro-magnet and the centre of the te.st-needle, and horizontal distances indi- cating the tangents of the deflections of the test^needle : A AAA is that for No. 1 ; B B B B for No. 2 ; C 0 CO for the covered end of No. 3 ; D D D D for the uncovered end of No. 3 ; E E E E for the covered end of No. 4 ; and F F F F for the uncovered end of No. 4. These cur\'es show that at considerable distances from the end of the electro-magnet the uniformly coiled magnet No. 1 produces the most powerful field, while for points nearer the magnet, but still at a distance of about 3 inches from it, the covered end of No. 3 magnet, corresponding with the curve 0 0 C, produces the strongest field, the next in strength being produced by the magnet No. 2, with the wire coned towards each end, since obviously the curve B B B cuts the curve A A A at a point corresponding with a distance of about 3 inches from the end of the magnet. The strength of the field at shorter distances than those indicated cannot be measured by the means above adopted. There is, however, another, although perhaps a rougher, means of observing the strength of the various parts of the field produced by the electro-magnet. It is well known that a magnet is capable of attracting iron filings, and that they take up definite positions when attracted. It is also an every-day experimeut to lay a magnet under a sheel of paper, thin glass, or other non-magnetic material, upon which iron filings are then sprinkled, when they form certain definite figures. If the magnet is a straight bar of steel, the filings take up their position in a manner ana- logous to that depicted in Fig. G. Professors Ayrton and Perry pursued a similar course in investigating the mag- netic properties of their coils, and obtained some interesting and instructive results. Fij?. 6. ^-^--■r..:M n 1 s " \ (■f v 1 'V, 1 V 1 1 r A\ V 1 \ ^ 1 ■ N s \^ s, , .v> N k \ i '\ \ 1 ^. 6^ I i ■< 4. ^, ^ .. \ V "^ ~H — 1 '"■l"- e... ... ^ L '^ -.1 [_ L_ 1 1 '' Fig. 7. Fig. 8. Fig. 9. Figs. 6, 7, 8, 9 afford remarkable illustrations of the effects produced. The iron filings are seen to take up defi- nite positions, and supposing Fig. 6 to represent an ordinary bar magnet, there is observable a concentration of filings around the extremities indicating the positions of maximum magnetic strengtk It will also be noticed that £J1 the filings set themselves in curves, and that these cur\'es exhibit a strong tendency to connect the one pole with the other, much in the same way that they do when the poles of an ordinary horse-shoe magnet are dipped into a quan- tity of filings. Even the apparently straight lines taken by the filings at the extremities (Fig. 6) are in reality only parts of large curves, easily discernible in the actual experiment. Aug. 2i), 1884.] • KNOWLEDGE • 175 The effect, then, of winding an electromagnet evenly is to produce an ordinary magnetic field as shown in Fig. C. With the second mode of winding, i.e., coning the wire towards the two ends of the iron, we obtain a held (Fig. 7) similar to the one produced by the usual winding, with the exception that the field between the poles is very weak. With the two other modes of winding (Xos. 3 and 4) there is a considerable concentration of force in the vicinity of the covered end, while the uncovered end " seems to form a long, weak pole," the difference between the two being that with No. i as contrasted with No. 3 there is a greater con- centration at the wound end, and that the opposite pole is longer. The movement made by the " neutral zone " towards the left hand is clearly indicated. The professors completed their experiments by ascer- taining the weight necessary to detach the armature from the covered end of each magnet, a constant or equal current flowing through each coil. The result was that with : — 1 43 ounces were required to detach the armature. 2 5/ „ ,, ,, 3 5i „ „ ,, ■t 77 „ „ „ These results show, then, that the effect of coning the wire is to produce a strong field near the pole, which, how- ever (as may be gathered from Fig. 5), falls off rapidly as the distance from the pole increases. It is also seen that ill contact or close proximity with the magnet numbers, 2 and 3 are equal, and are stronger than No. 1, while the effect produced by No. 4 is much greater than that pro- duced by either of the others. The deductions to be drawn are that with a given piece of iron, a given length of wire, and a given current, at distances from the end of the magnet very small compared with the length of the core, the wire should be coiled up at the near end. At points a little removed, equal, say, to one third the length of the core, winding evenly over one half is advantageous, while, for greater distance, uniform winding is the best THE EARTH'S SHAPE AXD MOTIONS. By Richard A Proctor. (Contimied from page 152.) CHAPTER III.— THE ANNUAL MOTION OF THE SUN AND STARS. ALTHOUGH during a single day the sun's motion is such as I have described it, yet it is impossible to watch the sun many days without noticing that the place of his rising and setting is continually changing, and also the elevation which he attains when in the south. Sup- posing our observations to commence in spring, we should notice that the sun began to rise further and further to the north of east, setting, of course, further and further to the north of west. We should further see his mid-day elevation gradually increasing. In about three months these changes would attain their greatest effect, and at this time we should find that the sun rose almost as far north as north-east, and set almost as far north as north-west, while at mid-day he attained an elevation of no less than ()2°, instead of 3Si°, as at first. Then in the next three months we should find these changes taking place in reverse order, so that at the end of the three months the sun would be rising nearly in the east and setting nearly in the west, as at the beginning of the observations. After this the sun would be found to rise towards the south of east, setting towards the south of west, while his mid-day elevation would continue to diminish. At the end of three more months these changes would produce their greatest effect, when the sun would be rising nearly as far south as south- east, and setting nearly as far south as south-west, attaining a mid-day elevation of only 15^. Lastly, during the next three months the sun would gradually return to the path he had at the beginning of the observations. Year after year these circumstances are repeated with the utmost regularity, so that the observer would find no ditHculty in forming a table recording the height which the sun would attain when due south on any day of the year. This, at present, is all that we shall note on this point. We shall shortly have to return to this part of our subject, and by considering the annual changes of the sun's appa- rent path more exactly — that is, in quantity and measure, instead of in a general manner, we shall be enabled to form an estimate of the real character of the sun's annual motion relatively to our earth. At present, however, our observer is supposed to be limiting his attention to those observations which may enable him to determine the earth's figure by travelling from the scene of his first researches. He is, in fact, endeavouring to learn how the sun or the stars would seem to move on any day of the year, as seen from his first station, in order than when he goes to others he may estimate the effect of change of place on these motions, and so learn what is the shape of that surface over which he is travelling. Our observer might notice also with special care where the sun rises and sets on different days, were it not that after some attention to this point, he would find that in the immediate neighbourhood of the horizon, celestial objects are not seen in their true places. He would quickly see that this was an atmospheric effect, because he would notice that even terrestrial objects, at a considerable dis- tance, appear often to be disturbed or distorted. Presently this peculiarity will need to be carefully considered. At present, all that is necessary is that the obsei-ver should avoid laying any stress on the observations of celestial objects when very close to the horizon.* The result, then, to which our observer pays special attention is the circumstance that on any given day in the year the sun always attains a certain elevation when in tie south. If he should find that when he travels to some other place, the sun, on any particular day, does not attain the elevation it would have had as seen from his first station, he will have to explain that circumstance — he will, in fact, have something to guide him to a true estimate of the earth's figure, of which, at present, he is supposed to know nothing, except that it has limits. In the meantime, and with a similar end in view, he notices the annual changes in the apparent position of the stars. This part of his work also leads to certain definite and very interesting results. Night after night he sees the stars following the same orderly movements which he had before detected. But gradually he begins to notice, that, at any given hour of the night, the aspect of the heavens is not the same as at the same hour on the first night of observation. The stars seem to have got further forward in their apparent rotation- movement. Carefully noticing this change, he is led to the conclusion that it is taking place in a regular manner. He can very effectually test its rate and character by means of the instrument figured in Chapter I. (Fig. 5), modified (as described in Chapter II.) for sidereal observation. He * It may be necessary to remind the reader that the refractive effects of the atmosphere slightly affect the apparent position of every celestial object, but in this part of my subject I avoid aU. reference to corrections so minute that the simple process of observation I am describing would not suffice to detect them. 176 ♦ KNOWLEDGE ♦ [Aug. 29, 1884, directs the tube L M at a given hour on any night to a certain star, and notices what division of the card circle, H K, falls opposite the mark on the upright. At the same hour on the next night, he will scarcely notice any appreci- able change ; but if he repeat the observation a fortnight later, he will find that he has to turn the card circle round about as much as for an hour's diurnal motion — that is, through about 71° — before '^L M points to the star. He will notice, however, that L M has not to be turned on its own pivot ; in other words, he will see that the star's distance from the pole of the heavens (the point to which F G is directed) remains unchanged. He may confirm this result by a second observation. Let him direct L M towards a star, and in any convenient manner clamp the axis F G, so that L M will remain fixed in position. Then at the end of fourteen or fifteen days let him come to the instrument an hour earlier in the evening than it was set. He will find L M pointing directly towards the star. He finds this to be true of every visible star in the heavens, except five. Consequently, all the stars retain the same relative positions among themselves, except those five, which he will therefore look upon as wanderers, a word synonymous with the term planet given to these five stars by the Greek astronomers. Our observer will, for the pre- sent, however, confine his attention to the other stars, which he will call for distinction's sake the fixed stars. He now knows that these stars have a somewhat swifter daily motion than the sun, insomuch that in half a mouth the stars have gained an hour's motion on the sun. It follows that in a year they have gained twenty-four hours' motion, or one complete rotation. Now here we shall avoid any reference to the diflicult processes by which the exact length of a year is determined. We will suppose that our observer is satisfied by noticing the perfect regularity of the stellar rotation, not only from hour to hour, but from day to day ; and that by some means or other he enables himself to measure time with such exactness that he could detect any apparent departure from the observed regularity of motion, should any such result seem to follow from his excursions over the earth's surface. We shall see that this knowledge, combined with his knowledge of the sun's altitude at noon of every day, or even only with his knowledge of the position of the pole of the heavens, round which the rotation seems to take place, will enable him to form the most certain and con- clusive opinions as to the 6gure of the earth on which he lives. On one point he has already gained new information. He has noticed that the star-groups retain their configura- tion altogether unchanged in whatever part of the sky they may be seen. And comparing the observations of one part of the year with those of another, he is enabled to see that the stars are strewn over the sur- face of all that portion of a sphere having E P as axis which can rise above the horizon circle S e N w — in fact, over every part of a complete sphere S ic P K, except the small segments S P' K. Now, at any moment the observer can only see half of the sphere S w P K. He knows that unless the stars, when below the horizon, take up relative positions very different from those they have when visible, they must at every instant cover the portion S w N K of space beneath the horizon, and as he sees no sign of any such change when the stars are visible, while at every season of the year he sees the known star-groups unchanged in aspect, he is clearly justified in feeling very certain that no such change takes place after the stars have gone below the horizon. Hence he is certain that the earth is not only limited in the direction of the horizon, but in every ditection below the horizon (except possibly towards the tr "nout S P' K, about which he has as yet no certain inforiijation). He will naturally infer that a complete sphere around him is bedecked with stars, and not a sphere wanting such a segment as S P' K ; but whether this be so or not, he is quite certain about the earth being limited towards all points below S tv N K, except points in S P' K,_/'or he knovjs t/cat stars are streion towards all such points. Knowing that the earth has limits, and perhaps even suspecting already that the earth, which lies within the celestial sphere, is more likely to be in ro- tation than the sphere itself, he sets out to explore his abode. He will direct his explorations first towards the north, to see what changes, if any, may be perceived in the position of the apparent pole of the heavens. Then he will return and travel southwards ; and, lastly, he will make a series of explorations towards the east and towards the west ; untU, finally, the secrets of the earth's figure shall have been completely mastered. OUR SUPPLY OF COAL. AT a time when approximate calculations have been, made of the date at which our British coal supply will be exhausted, the discovery of a reserve of some 8,000,000 tons must possess great popular, as well as more purely scientific, importance. Hence a pricis of a lecture delivered before the members of the Cotteswold Field Club on the 12th instant, by Mr. Handel Cossham (for which we are indebted to the Bristol Afercuri/ and Daily Post), can scarcely fail to be of considerable interest at once to the geologist and to the coal consumer : — • After remarking on the complicated geology of the Bi'istol coal-field, and particularly of the northern part of it, he mentioned that twenty years ago he was able to correct the geological maps of the district by showing that the supposed Millstone Grit, or Farewell Rock, between Bristol and Wick, was one of the Siliceous Sandstones of the coal-measures. It had consequently been discovered that the coal-bearing strata extend south of Kingswood and St. George under the river Avon, and, as far as he knew, to the Mendip Hills. That discovery had had an important bearing on the mining industry of the district, and would help in the future to unlock the mineral re- sources of the neighbouring county of Somerset He had, however, now to describe a discovery he had recently made, which, he believed, would prove of much greater importance. He reminded them that the Kingswood section of the Bristol coal-field contains probably the most ancient coal workings, not only of this country, but probably older than those of South Wales, Somerset, or Dean Forest. In 1371 Edward III. issued a mandate to the keeper of the chase of Kingswood to allow Edward, the son of Hugh Blunt, lord of the manor of Bitton, to take, sell, and carry away wood, gorse, and sea-coal found within the demesne ; and by the second half of the seventeenth century he saw by a map which passed to him as lord of the manor, that in the year 1672 there were no less than seventy small coal- pits at work in the Chase of Kingswood. The workings, down to the early part of this century, were of course con- fined to shallow depths, chiefly drained by levels into the Avon and Froom rivers, and were mainly confined to the upper section of the seams now worked in the district. About fifty years ago the Great Vein series were dis- covered, and have been largely worked ever since on the Aug. 29, 1884.] ♦ KNOWLEDGE ♦ 177 South dip, and over a considerable area. Some time ago he resolved to explore the whole of the area, about 2,500 acres, the mineral freehold of which he purchased some years ago. To do this he commened an exploring drift to the south, at a depth of sixty - eight fathoms from his Belgium pit, to cut the upper section of seams that lie over the ordinary Kingswood series and between those and the Pennant rock ; and at the same time he started a drift to the north, at a depth of 500 yards from the bottom of Speedwell pit, and it was the discoveries made by the latter, or north drift, from Speedwell, that he wished to describe. For some 200 yards this drift was driven in strata nearly upright, and exhibited traces of great disturbance and enormous lateral )iressure ; and, in fact, the whole of the Kingswood district has in past workings exhibited proofs of enormous disturbance and displacements, chiefly, as he some time ago explained in a published paper, having been produced by lateral pres- sure and not by vertical movements. Some 250 yards north of Speedwell pit they cut a seam of coal about 2 ft. 4 in. thick, lying in an upright position, and for a long time he supposed this to be the first of the lower or Ashton series of veins, which was what he expected to find when he drove the underground tunnel. But, extending the drift some 50 to 100 yards farther to the north, they found the strata became horizontal, and they struck a second seam of coal in several separate beds, the thickest of which was about 20 in. After following the vein for some 50 to 100 yards, he found that it was one of the old Great Vein group that had been worked 300 to 350 yards overhead up to the outcrop of the vein near the surface. This fact was so difficult to explain that he resolved, before coming to any decided conclusion, to drive cross-measure drifts to the veins above and below, so as to prove the fact beyond doubt before accepting it himself or announcing it to others. At the proper distance below this second vein, known as the Giller's End Vein, he found a particular and remarkable bed of strata, known in the district as the " Worm Bed," in its proper position in connection with this vein. He also knew that if he were correct in his opinion he should find at a dis- tance of some 30 yards vertical above this vein the splendid seam or bed of coal known as the Kingswood Great Vein, which he had no doubt was the equivalent of the celebrated 4 feet Aberdare Steam Coal Vein. Driving a drift across measures he discovered, on the 21st of last February, the vein known as the Kingswood Great Vein, lying in splendid position, and an average of about 5 feet thick, or from that to 5 feet G inches. Since that time he had been driving on these veins north, «ast, south, and west, and found that he was on the floor of the original coalfield, with a gentle dip to the west and rise to the east of about 3 in. to the yard, and apparently ex- tending to the north and east far beyond the bounds of his mineral estate. He did not want to trouble his hearers with anything that was merely personal and commercial, but he was sure they would pardon him for saying that not the least interesting feature of this discovery to him was that it had revealed the existence of from six to eight million tons of magnificent steam coal in his mineral estate that he had no expectation of having, and he could see clearly that for the next 50 to 100 years, at least, the collieries be worked could go on landing a large quantity of splendid coal, at a cost that would enable those who worked them to hold their ground against all competition, come from where it may, and thus continue to develop one of the important industries of the district Proceeding to the source of the dislocating force, he said the Mendip Hills formed the southern boundary of the Bristol coal-field, though their distinguished president (Sir William Guise), Mr. Etheredge, and himself were able some two or three years ago to gather proofs from the rocks at Cannington Park, near Bridgwater, that those rocks, which had previously been regarded as Devonian Limestone, were after all the Carboniferous Limestone, though in a highly crystalline condition, and very sparse of fossil remains. Being, however, genuine mountain lime- stone they showed almost certainly the existence of a coal- field south of the Mendips. His object in referring to this was to recall their attention to a fact that was proved by their friend Mr. Etheredge, and the late Mr. Charles Moore, of Bath, beyond all question, namely, that the Men- dips were lifted after the deposition of the coal measures— but prior to the deposition of the secondary rocks — and that when those hills were thrust up by the volcanic force that in some portions had pushed the lava right through the limestone and Old Red Sandstone, the whole country to the north, and possibly to the south as well, was thrust forward. At Radstock, five miles north of the Mendips, this thrust had given Lady Waldegrave a double quantity of the Radstock or upper series in veins. They must, however, look for the force that has thrust the Kingswood coal-field over itself at a nearer point than the Mendip Hills, and he thought if they would look at the enormous develop- ment of carboniferous limestone at Blackdown, Bourton, and in that district, they would see the seat of the force that has caused this displacement. It was singular and exceedingly interesting to note the effect of this thrust. If they looked at the map they would see that south of where they stood the river Avon has been pushed a mile to the north out of its natural course by the same force that had thrust the coal-field over itself, and he happened to know that two or three miles below the level course of the seam of coal in the coal-field had been turned almost at right angles to its regular course by the same upheaval of Carboniferous Limestone, and the displace- ment caused thereby and the level course of the workings on the south dip of the coal-field at Kingswood at a great depth, followed the remarkable course in the river to which he had called attention — thus showing pretty conclusively that the course which had caMed the one had produced the other. The level course of the workings at the South Liberty of the Ashton Colliery had been turned round by the same course. In conclusion, Mr. Cossham remarked that the' problem he had endeavoured to explain would have a very important influence on the future of the district, and was associated with an industi-y upon which the future of the country largely depended. Whenever England's mineral resources failed, her commercial supremacy must end, and therefore every discovery that widened the area and increased the extent of their mineral resources should be regarded with interest. A PRACTICAL METHOD OF ESTI- MATING DISTAXCES. DRAW one or more silhouettes of standing or kneeling men upon a card — the standing ones 25 mm. in height and the kneeling ones 16 mm. If you are an artist and have the means at disposal, instead of simply blacken- ing the figures, you may paint both surfaces with the colours that are peculiar to the different uuiforms of the enemy, but care must be taken not to lay the colours on too thin. Now cut the figures out with care, leaving sufficient paper attached to their bases to allow the instrument to be held between the thumb and first finger. 178 ♦ KNOWLEDGE ♦ [Aug. 29, 1884. The apparatus being constructed, it only remains to use it. At 200 metres Jistance station one or more men, and, where you are standing, allow an assistant to hold the instrument at the height you direct him to. Now proceed 10 a distance of exactly four paces, of 0'7.5ni. each, from your figures, and ascertain whether their general aspect, as regards height and width, corresponds to that of the men stationed 200 mitres off. If the resemblance is perfect, you are in possession of one of the timplefet and most port- able of telemeters ; if it is not, you will have to begin all over again. You may renew the operation by placing your men at 300 metres, and taking six paces instead of four (Fig. 1). The arrangement adopted permits, on holding the instru- ment away from the eye, of diminishing the ditficulty that the latter has of seeing the objective and image simulta- neously. Besides, it lessens the trembling of the hand that holds the apparatus, and which would render observation, impossible in an ordinary stadium placed at OG m. from the eye. What is the value oi —1 In the majority of -proportional base telemeters the distance sought is .50 times greater than the base. Such a ratio is'very convenient, since it necessi- tates a base of only 20 mfetres for a distance^of^l kilometre >^^^- ¥M^ ', ■A • ' -^ ' "^^Sf*?:-' _ - ''^^^i^iF:^^': Fig. 1 — lleth)d of Estimating Distances. Supposing that the apj)aratus has been constructed satis- factorily, the manner of using it for estimating distances •will be readily understood. Let an assistant hold the in- strument in the direction of the troop th;it serves as an oVijective, while you move backward in keeping your eye upon the silhouettes and the objective, and stopping when the figures and men exhibit the same aspect and seem to form part of one and the same group. Then returning to your assistant, you count the number of paces that separated your eye from his hand. Upon multiplying this number by 50, you will obtain a product that will give you in metres the distance sought. Notwithstanding the wonderful simplicity of the instru- ment, it is easy to control the accuracy of the principle upon which it is based, first, by reasoning, and then by experiment. In the similar triangles, ABC and DEC (Fig. 3), we have the ratio : («) x = l—- h H and h being constants, I will have to vary -with x, that is to say, with the distance. However, as the observer can scarcely measure the bas*- otherwise than by pacing it off, it has seemed preferable, in order to expedite the operation and avoid a conversion of pace measurements into mitre ones, to take a mean pace of 07.5 m. as unity, and to modify the formula so as to all once obtain the distance in metres. In formula a, on substituting wxO'75 for I, and making -T-x 075=50 (H being equal to 1,6&5) we shall have 0'249 m. as the value of /(. If, however, greater precision were required in the results, the metre might be preserved as the unity of measurement of the base, the silhouettes be given a height of 33 millimetres, and a cord about 30 metres, with knots 1 mitre apart, be employed. But it will be readily under- stood that this process, although more accurate, is much less practical. Let us now examine the causes of error, as well as their limits. The height of a soldier, taken as a base, varies between l'-t5m. and LSm. As the mean height generally ad- mitted is 1'665 m., we should, upon taking this as a basis Aug. 29, 1884.1 ♦ KNOWLEDGE ♦ 179 and operating upon extreme heights, commit an error of about one-thirteenth, more or less, of the distance sought. But if, besides the height, we consider (and it is the case here) the breadth of several men, we see that this dimen fion has less variation, and that we could not assign to the error a value of more than one fourteenth. This might, moreover, be sensibly reduced by means of operations re- peated upon different subjects. Another cause of error is due to the manner of doing the pacing, which may vary from 0*7 m. to 08 ni. at the most when some little attention is paid to it, or 005 m., more or less, than the normal pace. But the error com- mitted in this case will represent only one thirty-fifth, more or less, of the distance sought, and this may be thrown entirely out of consideration when regulating firing is con- cerned. The two errors, upon being added, will, at the worst, never give a deviation of more than one tenth in the real distance, and we shall admit that such an approxi- mation is sufficiently exact if we reflect upon the gross errors that we should commit in estimating by eye, and ujion the great variations in range that occur in the best- regulated firing. Fig. 2. — Apparatus for Estimating Distances (actual size). Let us add, that with this instrument it is not necessary to see the entire object ; if the upper part of a man's body can be seen, it will be sufficient. In clear weather this process can be applied to distances of 1,000 metres and beyond ; but if there is a field-glass at one's disposal, it will be preferable to use it for very long distances. In all cases it is well to light the image as much as possible in the same manner as the men observed. If, for example, these latter were in shadow and the instru- ment were too brightly lighted, it would be necessary to Fig. 3. — Apparatus for Estimating Distances. cut off with the hand or cap the solar rays that were falling thereupon. It resulted from experiments made at Fort Cagnelot, on the Langre plateau, that, out of thirty measurements, one only could be considered as insufficient, this having given an error of at least one-eighth of the distance. All the rest showed a deviation much less than that which had been fixed on as a limit ; and, if a mean of such deviations be sought, it will be found that it was only one twenty-second. The little instrument that we have just described has in nowise the pretension to replace those excellent tele- meters that all infantry corps are provided with ; but it offers a sure and convenient means of estimating distances, and we believe that a frequent use of it will quickly familiarize the observer with making such estimates by the unaided eye, and this, it should not be forgotten, will always be the most really practical method on the field of battle. — La Nature. PLEASANT HOURS WITH THE MICROSCOPE. By Hknet J. Slack, F.G.S., F.R.M.S. THE dry season has not been favourable to the growth of fungi, but in cool houses, stoves, and out of doors, some of the gardener's plagues are sure to be found. Here, for example, is a plum-tree against a wall, with leave* looking as if all manner of minute rubbish, plentifully mixed with soot, bad been stuck upon them. An inspec- tion with a hand-glass shows amongst the smut-patches numerous cast skins of aphides ; here and there a small, live object — the so-called red spider, which is a mite — and some scale-bugs. So little of the leaf is left in its natural state that all its functions must be suspended. If an orange-tree is examined, some of its leaves will most likely exhibit similar dark spots. Geraniums in a cool house may here and there have on their leaves the same sort of sooty stuff, and ferns are not infrequently attacked. The only thing to be done for the health of the plants is to wash all the objectionable stufi oflf with soapand-water, or the Gishurst compound — a sulphur soap. If the leaves of any plant exudes honey- dew, or that substance deposited by aphides, black fungi are pretty sure to grow ; but leaves are often covered with them when no particular reason can be detected why they should be assailed. If a bit of infected leaf is viewed under the microscope, as an opaque object, small tufts may be discovered, looking less black than they appear to the naked eye. They are composed of thread-like tubes and spores of various shapes, which are translucent enough to transmit some rays of brownish or sometimes olivaceous light. A little of the black stuff may be removed with a pea- knife placed in a drop of water on a glass slide, and spread out by moving a covered glass over it. The annexed figures represent the miscellaneous objects likely to meet the view. It is hopeless for any one not well practised in fungology to name these things with proper discrimination, and great authorities like Berkeley or Cooke would not pronounce upon some except after carefully cultivating them, and seeing what they should do. The old authors called the black stnS Cladosporiiim fumago, but Dr. Cooke tells us it is now usually named Funiago varians, and that it is considered a conidial stage of Capro- dium. If the inquirer examines these things under a microscope, and compares what he sees with the drawings and descriptions of the fungologists, he will think they might be taken for IlehninthosjMrmm, Cladosporium, Macrosporium, and Sporidisinium. What is remarkable, and of great though puzzling inte- rest, is the variety of forms under which fungi of the same species can carry on their life processes. In the aggregate, a prodigious amount of work is done by fungi of the minuter kinds. They and their relations — bacteria, &c. — 180 ♦ KNOWLEDGE ♦ [Adg. 29, 1884. preside over the disintegrating processes of decay and putre- faction. Their spores abound in the air of towns, and in rural places that are not very high above the sea level and remote from sources of contamination. Their adaptation to various conditions of heat, cold, moisture, dryness, rich or poor supply of appropriate food, 2. QtoKS 3Iate 2. Kt to Q8 Mate If K to Q2 If BxR 2. Kfc to B5 Mate 2. QxR Mate If R moves If K toK4 2. KttoQS Mate. 2. QxR Mate. A WELL-FOUGHT Consultation Game, played at the Chess Clnb, at Amsterdam : — Two Knight's Defbnxe. 3. 4. 5. G. 7. 8. 9. White. B J. Loman and B. J. Mever. 1. P to Kl 2. Kt to KB3 B to Bi Kt to Kt5 PxP B to Kt5 (cli) PxP Bto K2 Kt to KB3 10. Kt to K5 11. P to KB4. (b) 12. P to Q4 13. Kt to QB3 IV. Castles 15. B to K3 16. Q to K sq. 17. Kt to Q sq. 18. BtoQ3 19. Kt X Kt ((') 20. P to B4 21. B to QR5 22. P to Q5 23. Q to E4 24. P to B5 Black, ilerr von Forrest and H. J. Siohlberg. P to K4 Kt to QB3 Kt to B3 P to Q4 Kt to QR4 P to B3 PxP P to KR3 Pto K5 B to Q3 (a) Q toB2 Castles P to QR3 (c) R to Q sq. PtoB4 RtoKtsq.((l) Kt to Q4 Kt to QB3 QxKt P to KG (.0 Kt to Kt3 Q to B2 R to K sq. B to K4 (g) Position after Black's 24th more. Black. 1 S? 4 kj © f-3"^ -^' 1 t 't ^- 1 /f-- * . k (_) a- w i \tL ^ w "' i % '• s^ 1^ 1 ^ AViHTi:. White. p to EC (;,) RxB QxRP PtoKR4 (0 Kt to B3 B to Q3 B to B7 (m) BxB Biac-k. BxP PxR (i) QtoK4 Kt to R5 (/,) RxP B to B4 (/) QxB Resigns (m). NOTES. (a) This move seems to afford the best chance for Black in this defence. (I) It is reqnsite to advance this Pawn before the QP. (c) To prepare for P to B4. ( Our Chess Column 168 NOTICES. Part XXXIV. (August, 1884), now ready, price Is. 3d., poat-free, la. 6d. Volume v., compriaing the nnmbers published from January to June, 18S4, now ready, price Os., iucluding parcels postage, 93. 6d, Binding Cases for all the Volumes published are to be had, price 2s. each, including parcel postage, 23. 3d. Subscribers* numbers bound (including title, index, and cafe) for 3s. each Volume ; including return journey per parcels post, 3s. 9d. Remittances should in every case accompany parcels for binding. TERMS OF subscription: The terms of Annual Subscription to the weekly numbers of Ksowledgb are as follows : — 8. d. To any address in the United Kinedom 15 3 To the Continent, AustrHliu, New Zealand, South Africa, & Canada 17 4 To The United States of America $4.25 or 17 -4 To the East ludies. China, ic (rm Brindisij 19 6 All subscriptions are pavubje in advance. OFFICE : 74-76, GREAT QUEEN STREET, LOKDOX, W.C. Sept. 5, 1884.] ♦ KNOV/LEDGE ♦ 189 AN ILLUSTRATED MAGAZINE^SCIENCE PuunlyWorded-Exactlydescribed LONDON: FRIDAY, SEPT. 5, 1884. Contents op No. 149. Our Two Brains. By Richard A. Proctor 1S9 Dreams. VIII. By Edward Clodd lOO The Westinghouse" Brake. By "Trevitliicli" 193 More About Sunflowers. By Grant Allen I!I3 The Earth'9 Shape and Motions : IV. Determining the Shape of the Earth (/Hi«.) By H. A. Proctor 191 An Address to the British Associa- tion 19li The Electric Light in the Mecher- nich Mines 197 Optical Becreation. (Illun.) By F.R.A.S 19S Ttow American Carp are Destroyed. I {luui.) : im t other Worlds than Onrs. By M. de Fontenelle. With Notes by Richard A. Proctor 200 Muscular Contraction after Death 201 ] International Health Exhibition. XIII. ilUm.) 202 I Editorial Gossip 203 Reviews 2(H Miscellanea 205 Correspondence 205 , Oar Chess Column 208 OUR TWO BRAINS. By Richard A. Proctor, THAT we have two brains may be said to be as certain as that we have two eyes, two ears, and two nostrils. Whether the two brains — I use the expression purposely, instead of the usual expression, the two hemispheres of the brain — act as independently of each other as the two eyes or the two ears may be disputed. It may be maintained by some that though they can thus act independently, should occasion arise, the two halves of the brain, as a ru^e, work not only as one but as parts of a single organ. Others may hold (though the evidence is strong against this extreme view) that one brain alone of the two can never suffice for the process of reasoning. Others again may believe that the two brains are absolutel}^ independent organs, a view as extreme on the other side. But whatever opinion may be held as to the action of the two brains, there can be no question as to their existence in all normal case.''. That the two brains are connected or associated together, is no doubt true. So are the two eyes connected by the optic commissure. But we do not speak of the two eyes as one organ, though they serve a single sense. Even less can we speak of the two brains as a single organ, when we find no clear evidence even that they do the same work. If each does or can do the same work, independently of the other, they must be held to be distinct organs even as the right eye is distinct from the left, when both work together in ordinary vision. If the two brains do different work, they are still more obviously distinct organs, — even as I, for instance, more definitely recognise the duality of my eyes than most persons, because, unlike most, I use one eye for distant vision and the other for fine work at short focal ranges. Of course a case might be made out for the oneness of the brain as an organ, despite its duality of form, if it could be shown that the individuality of the owner of the brain depended wholly and solely on the co-existence, in a complete state, of both hemispheres of the cerebrum (or of both cerebra, as one should more correctly say). Even if the two eyes, distinct though they are in appearance, were found to be severally essential to vision, we should be obliged to regard them as a single organ, much as we regard the upper arm and the lower arm as forming a single limb. Nothing short of this, however, — and we have no evidence even approaching this. — could compel us to reject the doctrine of the duality of the brain. I propose to consider some of the evidence which led Dr. A. L. Wigan to definitely enunciate this doctrine, suspected apparently by Dr. Holland and others before Wigau's time, but not clearly perceived or stated till he wrote his work, now I believe out of print, " The Duality of Mind." I would, however, at the outset, point out how interesting, nay important, the inquiry is. How many moral problems of difficulty find their solution if we recog- nise in each one of us two minds, and in efiect two wills, woi king it may be in harmony together at all times, or only in h.rmony when the body is iu sound health, or one usually holding sway over the other, or alternating in their influence on conduct, or one it may be diseased and only held in restraint by the other from guiding tlie man astray ! Again, how many interesting mental problems appear in a new light when thus viewed ! We have to consider two memories, usually no doubt synchronising in their action, but not necessarily working thus simultaneously ; two attentions ; two reasoning processes ; and so forth. Again, the two brains maj' differ in their physical powers, even as one arm may be stronger than the other, one eye more sen- sitive than the other to light, more easih' wearied, and so on. Such cmsiderations are full of interest, and mav throw important light on mental phenomena : but they are most important in their bearing on character and conduct. I might here occupy much space with a description (in outline) of the human brain as analysed and interpreted in our time. But for my present purpose this is unnecessarv. The following points, only, need here be specially noted :— If a vertical section be supposed to be taken through the middle of the head from front to back, that is so as to divide it (through the middle of the chin, nose, forehead, crown, .and nape of the neck) into right and left portions, this section will divide the whole nervous mass within the skull into two symmetrical halves. Each part on one side of the plane of division has its counterpart on the other side, in the same way that each bone, muscle, tendon, fibre, and nerve in the right arm has its counterpart in the left arm. There is not perfect symmetry, nor exact corre- spondence, any more than in the case of the two arms. In some cases there is a marked want of symmetry, just as in some men we see one arm much bttter developed than the other : but such abnormal cases do not affect the general truth that the right and left sides of the outer head are symmetrical, and that the right and left arms corre- spond to each other. Again, the principal parts of the cerebral mass, though thus double, are connected across the median plane by medullary bands called commissures, by which each part on one side is united to its fellow on the other side. Thus the great hemispheres (which in reality are not much more than quarter spheres) are connected by the " great com- missure " called the corpus callosiim ; the halves of the cereheUuni (or little brain, occupying the lower and hinder part of the cavity of the cranium) are connected by the po)is Varolii or tii,ber annulare : and there are pther com- missures ot smaller size. This connection of .tlie corre- sponding parts of the two side brains no more cdiiljbines them into a single brain than the two arms are' made one by being attached to the same body. Between tie two so-called hemispheres of the brain there' lies above a scythe-shaped extension of the membranoiife covering called the di'.ra maUr; the point of the scythe is 190 KNOWLEDGE ♦ [Sept. 5, 1884. forward, and its median plane is of course vertical. It is called tlie fal.c cerebri. A large lateral expansion of the falx — called the tentorium — separates the posterior lobes of the cerebrum from the cerebellum, extending over the latter like a vaulted floor. It protects the cerebellum from the pressure of the hinder part of the cerebrum.* The central hemisjiheres are separated below by two cavities termed the lateral ventricles. There are other smaller cavities called respectively the third ventricle, and the ventricle of the cerebellum. The last-named is of considerable extent, and occupies the space between the cerebrum, the commissure of the cerebrum, and the medulla oblongata, the portions of the nervous mass lying at the base of the cranial cavity, between the cerebrum and the cerebellum. It should be added that from the upper surface of th^^ convolutions, fibres descend to the medulla oblongata, where they form the corpora pyramidalia and decussate or cross over from one side to the other. This interesting fact was first established by Drs. Gall and Spurzheira. It follows that the right brain rules the left side of the body, and the left brain the right side. In agreement with this is the fact that if one side of the brain suffers it is the opposite side of the body which is alone affected. I have said so much respecting the parts of the brain rather that the cases which will have presently to be •quoted may bi^ fully understood, than with any idea of giving even in outline an account of the exceedingly com- plex; structure which appears to regulate thought, sensa- tion, and motion. We have now to consider the evidence tending to show that each of the so-called " hemispheres of the braiu " is an independent [orgau of thought, in the same sense that each eye is an independent organ of vision. The first point to be noted is that one side of the brain may suffer the most serious mischief, or even be destroyed, -without any marked injury to the mental functions. Dr. Wigan mentions the following case as that which first attracted his attention to the duality of the brain : — ' A boy, in climbing a high tree for a rook's nest, missed his footing, and fell on the sharp edge of an iron railway, one of the earliest laid down in this country, and on a different principle from those now in use, the wheel passing in a sort of groove, instead of on the edge of a projection. The side of the iron rail stood up, and was exposed to the ■friction of the outer side of the wheel, which soon wore it to a sharp edge. The boy fell head-downwards on this ; it entered about an inch from the falx and sliced off a large portion of brain, with nearly the whole of the parietal bone ; much of the brain being torn and ragged, I pared off the projecting fragments aud replaced the mass, not having the slightest hope of his recovery, and only occupy- ing myself with the task of laying on plasters and bandages to appease the anxiety of the friends. The quantity of the brain lost must have exceeded four ounces, but my recollection of the case is vague after an interval of more than thirty years. Having always read that the integrity of both hemispheres was essential to the due «xercise of mind, I was much astonished the next day to * Wigan makes the following remarks on the Falx and the Tento- Tiunj : — The object of these membranes, which are as tightly stretched as the akin of a drum, seems to be to prevent the mis- v.hievous con^pfpi^nces of the concussion of the brain in sudden movements; a> jumping, for example — the elastic membrane gives w.ay to the impKi.M-. and thus diminishes the shock. The falx is also of great utility iu preventing the pressure of one brain on the other in lying down j and the transverse membrane, called the tentorium, performs a similar office j it forms a kind of tent (whence its name), and covers a deep hollow in the back of the skull, which contains the cerebellum, and thus preserves it from the pressure of Jthc fniJCiincumbci.l mass of cerebrum. find the patient (a remarkably intelligent lad, of twelve or thirteen years of age) in the full possession of his faculties in as high a degree as at any former period. He did not seem to suffer pain, — had no delirium, — and advanced steadily towards recovery ; considerable new growth took place ; but of its nature I have no recollection ; it was probably fungous ; at the end of a few weeks he was so well that, in spite of the remonstrances of his mother, he went into the field to play ; became exceedingly heated by this, under exposure to a violent sun, and then walked deliberately into the water to cool himself. The new blood- vessels burst, and he died of haamorrhage ; never having manifested from first to last any loss or perversion of mental power." It seems impossible to doubt that in this case the part of the brain which was destroyed was large enough and important enough to have seriously affected the mental power had the brain been a single organ. Nay, it would seem probable that just as one eye would be rendered for a while entirely useless by some serious injury, so the whole half of the brain, on the side which had suffered injury, must for a time have been useless. Therefore as the boy showed no loss of mental power, the other half must have been a perfect brain in itself Let us consider, however, some cases which seem still more decisive. {To be continued.) DREAMS: THEIE PLACE IN THE GROWTH OF PBIMITIVB BELIEFS. Br Edward Clodd. VIII. IN proof of the closing remarks in the previous paper, that the breath has given the chief name to the soul, we find the Western Australians using the same word, waiig, for " breath, spirit, soul ; " in Java the word naxva is used for " health, life, soul ; " in the Dakotah tongue jiiya is literally "breath," figuratively "life;" in Netela jmits is " breath " and " soul ; " in Eskimo silla means air and wind, and is also the word that conveys the highest idea of the world as a whole, and of the resisoning faculty. The supreme existence they call Sillain Innua, Owner of the Air, or of the All ; in the Yakama tongue of Oregon wkrisha signifies there is wind, vkrishwit, life ; with the Aztecs eJiecatl expressed both air, life, and the soul, and, personified in their myths, it was said to have been born of the breath of Tezcatlipoca, their highest divinity, who himself is often called YoalliehecatI, the Wind of Night.* This identity of wind with breath, of breath with spirit, and thence of spirit with the Great Spirit, which Sees him in cloud, and hears him in the wind, has further illustration in the legends of the Quiches, in which the unknown creative power is Hurakan, a name familiar to us under the form hurrieane, and in our own sacred records where the advent of the Holy Spirit is described "asof a rushing, mighty wind. "t In the Mohawk language atonritz, the "soul," is from atonrion, "to breathe"; whilst, as showing the analogy between the effects of restricted sense and restricted civilisation, Dr. Tylor quotes the case of a giil who was a deaf-mute as well as blind, and who, when telling a dream in gesture-language, said : » Brinton's "Myths of the New World," p. 51. (Second Edition.) + Cf. Knowlefge, June 1, 1SS3, p. 321. Sept. 5, 1884.] ♦ KNOWLEDGE 191 " I thought God took away my breath to heaven." Among the higher languages the same evidence abides. " The spirit doth but mean the breath." That word spirit is derived from a verb spirare, which means "to draw breath ;" Animus, "the mind," is cognate with anima, "air;" in Irish, which belongs to the same family of speech as Latin, namely, the Aryan or Indo- European, we have anaJ, "breath," and anam, "life," or " soul ; " and in Sanskrit, which is the oldest member of that family, or has, at least, best preserved the primitive forms, we tind the root an, to "blow " or " breathe," whence anila, " wind," and in Greek anemos, with the like mean- ing. The Greek psyche, pneuvia, and thymos, each mean- ing " soul " and " spirit," are from roots expressing the wind or breath. In Slavonic the root du has developed the meaning of breath into that of soul or spirit, and the dialect of the gipsies have duk with the meanings of breath, spirit, ghost. That word ghost, the German geist, the Dutch geest, from a root meaning to blow with violence, is connected with gv^t, gas, geyser, in Scandinavian, glosor, " to pour forth." In non - Aryan languages, as the Finnish, far means " soul, breath, spirit, wind " ; henki, " spirit, person, breath, air " ; the Hebrew nephesli, " breath," has also the meanings of " life, soul, mind," and rnach and neshamah, to which the Arabic 7iefs and ruh correspond, pass from meaning "breath" to "spirit." The legend of man's creation records that he became a living soul through the breathing of God into his nostrils " the breath of life," and concerning this the Psalmist says of all that live, " Thou takest away their breath, they die, and return unto the dust. As a final illustration, the Egyptian k7ieph has the alternative meanings of " life " and " breath."* When we pass from names to descriptions, we find the same underlying idea of the ethereal nature of spirit. The natives of Nicaragua, California, and other countries remote from these, agree in describing the other self as air or breeze, which passes in and out through the mouth and nostrils. The Tongans conceived it as the aeriform part of the body, related to it as the perfume to the flower. The Greenlanders describe it as pale and soft, as without flesh and bone, so that he who tries to seize it grasps nothing. The Congo negroes leave the house of the dead unswept for a year, lest the dust should injure the delicate substance of the ghost ; and the German peasants have a saying that a door should not be slammed, lest a soul gets pinched in it. In some parts of Northern Europe, when the wind-god, Odin, rides the sky with his furious spectral host, the peasants open the windows of every sick-room that the soul of the dying may have free exit to join the wild chase ; whilst both here and in France it is still no uncommon practice to open doors and windows that the soul may depart quickly. Dr. Tylorf cites a passage from Hampole's " Ay en bite of Inwyt," i.e., "Remorse of Conscience," a poem of the fourteenth century, in which the author speaks of the intenser suflering which the soul undergoes in purgatory by reason of its delicate organisation. The soul is more teudre and nesche (soft) Than the bodi that hath bones and fleysche ; Thanne the soul that is so tendere of kinde, Mote nedis hure penaunce hardere-y-finde, Than eni bodi that evere on live was, * Jacob Grimm remarks that whilst the more palpable breath, as spirit, is masculine, the living;, life-giviny pollen brought from a totally distinct plant. The resinous secretion may therefore serve a double pur- pose, first, in protecting the young buds, and, secondly, in compelling bees to alight and visit the flowers in the order most conducive to cross-fertilisation. The mechanism for the withdrawal of the anthers and style after their functions have been respectively performed is so minutely curious that I feared to describe it in full, lest it should prove tedious to the readers of Knowledge. Since I am asked for it, however, here it is, as well as I am able to explain it. The style, with its two sensitive stigmatic surfaces folded closely together, is enclosed in the united anther tube, and has numerous small hairs, pointing upwards, on its outer sur- face. The pollen-sacs open inward, and fill the hollow cylinder thus formed with shed pollen, before the separate florets open. As each floret matures for its first (male) stage, the style pushes upward, inside the anther-tube, and the hairs on its surface drive the pollen to the top of the tube, where it stands in a little heap, as soon as the flower opens. The filaments are sensitive (a fact which can be tested in a manner I will presently describe), and as soon as the pro- boscis of an insect touches them they contract, thus slightly withdrawing the anther tube, and shedding the pollen over him at the exact right moment to ensure its being employed in fertilising another flower. After the pollen has thus all been shed, the filaments continue still further to contract, apparently by mere fading, till the style protrudes from the top of the anther-sac. The fila- ments, however, are still so elastic that one can pull them out with the finger almost to the original length. The depression of the anthers into the tube of the corolla seems to be aided in part by the unfolding of the style, which now curves over its two branches, thus displaying the receptive stigmatic papill.T, which catch the pollen and induce it to emit pollen-tubes. If the floret is fertilised by a bee, well and good ; if not, the branches of the style bend over until they come in contact with the pollen swept by the hairs of a neighbouring style from a sister floret. They thus secure the second-best sort of cross-fertilisation, that from another flower of the same head. As soon as ferti- lisation has taken place, the curved branches wither, the style shrinks or shrivels just as the filaments had done before, and the entire mechanism is finally withdrawn within the tube of the corolla. At the same time, the corolla as a whole bends outward at the base, becomes humpbacked as it were, so as to turn away from the centre and thus avoid distracting the attention of the insect visitors. The lobes also bend together slightly, as if to deter the bee from trying these already over-blown flowers. The shrinkage in each case seems to me to be merely due to the usual shrivel- ling of all parts which have fulfilled their function, but in the filaments it is greatest on the inner surface, so as to make them bow outward. As long as the style and the filaments are still actively required, they are full of juice and vigour ; as soon as the pollen is shed and the ovary fertilised, they become at once flaccid and contracted. In order to observe the sensitiveness of the filaments, take a fully-open sunflower, and select a few florets (with- out removing them from the head) in the highest perfection of the male stage, when the pollen stands in a little heap at the top of the anther tube. Then, with a needle, or, still better, a soft bristle, remove the pollen gently from the summit of the anthers. You will thus be enabled to observe better the after effect. Next, push the needle or bristle down the corolla tube, and gently irritate the base of the filaments, exactly as an insect would do with its proboscis in searching for honey. You will observe in a 194 KNOWLEDGE [Sept. 5, 1884. moment that more pollen is beginning to exude from the top of the anther tube, its exudation being due to the con- traction of the sensitive filaments, which draw down the anthers, and so cause the pollen to be expelled by the hairs on the surface of the style. After continuing the irrita- tation for twenty seconds or so, again brush off the pollen from the top of the tube. You will find that the anthers have now receded somewhat, and that the style, with its branches still closely pressed together, begins to [jrotrude slightly fi'om the summit of the anthers. In other words, you have given the flower its cue for passing from the first or male to the second or female stage. As soon as that cue is once given, the change proceeds apace — the anthers continue to shrink down into the corolla, and the style to open its branches. The question of the mechanism for ensuring irritability in the filament, I must leave to better microscopists than myself. This is rather a more technical paper than usual, and I fear some readers may find it difficult of comprehension. But if they will take a sunflower in its prime, and cut it in two, following the description with the living object, I think it will all become quite clear to them. THE EARTH'S SHAPE AND MOTIO^^S. By Richard A Proctor. (Continued from page 176.) CHAPTER IV.— DETERMINING THE SHAPE OF THE EARTH. AS our observer sets out on his northward journey he sees the earth spread forth as a plane before him in that direction as well as in others ; and, therefore, his natural conclusion is that he is about to voyage in a straight line. This, at least, is the assumption on which all his observations must, in the first instance, be grounded. Let us suppose that an observer travels about 380 miles towards the north before recommencing his observations of the skies ; although not very important for the particular observations now to be made, we shall yet suppose that he has taken careful count of time, and has with him the means of measuring time throughout his observations. He proceeds precisely as at his first station ; and, after a similar series of observations, he finds results strikingly similar to those before obtained. He finds the whole heavens rotating in appearance about a fixed axis, with perfect uniformity, and at precisely the same rate as he had noticed when at his former station. But one important difference attracts his attention. He finds that the point about which the .stars appear to move (which point he may determine either as before by watching the daily motion of the sun in .spring or autumn — for we suppose him to settle for some time at his new post — or by watching the motions of the stars themselves) is higher up above the northern horizon. Measuring carefully the extent of the change, he finds that instead of being about 51^° the pole is now about 57" above the horizon. Let us see what this result seems to teach : — Let A (Fig. 1) be the first sta- tion of the observer, B the second, so that A B represents a distance of about 380 miles. Then if the assumption that the observer has been travelling in a straight line is correct, he must draw AP at ' --. an angle of 5U° with AN, and B P at an angle" of 57°, these lines Fig. 1. of course meeting, and so forming a triangle A P B, whose vertical angle A P B is the difference between 57° and 51^°, that is 5i°. Now, before proceeding further, we notice here a source of perplexity. When at A the observer found the whole of the heavens moving exactly as though they were rotating around the axis A P ; and now, when he is at B, he finds them moving exactly as though they were rotating around the axis BP. It need hardly be said that rotation cannot take place simultaneously around two intersecting axes. Therefore, we must select one of two alternatives. Either we must abandon the notion of a uniform rotation, which seemed in so simple and beautiful a manner to account for observed appearances, or we must give up the theory that in travel- ling along the earth surface the observer h;8 followed a straight line. Now about the first of these alternatives, it is easy to form an opinion. We know certainly that the line of sight from A to a star traces out the surface of a right cone, having A P as axis. We know with equal certainty that the same is true of the star as seen from B. Hence, in place of the uniform circular motion we deduced before, we require that the star should travel along the complex (and not even plane) curve which is the intersection of two right cones having intersecting axes. But we need not follow out the difficult considerations here suggested ; for we can take the case where the cone becomes a plain, and so simplify matters. Let E S W (Fig. 2) be the path of a star which rises in the east, as seen from A. Then the line of sight from A to this star lies always in the plane E A W S. But the same star, as seen from B, also rises in the east and sets in the west, attaining a lower altitude in the south by 5°. Therefore its apparent path lies as e s w in the plane e B ir s. This plane intersects the plane E A W S in a straight line K L, and it is only by moving along the straight line K L, starting with an infinite velocity from an infinite distance in direction K, travelling with a con- tinually diminishing velocity up to -, and thence passing away with a continually increasing velocity to infinity to- wards L, that the star could appear to move as it actually does when viewed from A and B. The journey from infinity in direction 2 K to infinity in direction 1, L would, according to this view, occupy but half a day, and in some inscrutable manner the star would return in the next half day to its original position, at an infinite distance from us, in direction 2 K. This is altogether absurd and in- credible. Our observer, therefore, finds himself compelled to abandon the theory that he has travelled in a straight line from A to B. But, to make assurance doubly sure, he applies other experiments. It will be seen at once (from Fig. 1), that if A B really were a straight line, the distance of P could be at once determined, either by a geometrical construction or by calculation. Suppose the observer applies either method, and then makes another journey equal in length to A B, and still due northward ; then, renewing his ob.servations of the heavens, he would have it in his power to make a new calculation of the distance of P from A ; and if his assumption that he was following a straight path were correct, his rew estimate of A P should agree with his Sept. 5, 1884.] • KNOWLEDGE ♦ 195 rig. 3. former one. But this he does not find to be the case. When he has got to C (Fig. 3), making B 0, equal to A B, he finds that the pole of the heavens has Tisen by exactly as much as it was raised by his former journey. Now, if we draw a line from C to P, we get an angle C P B, which a very brief consideration will show to be larger than the angle A P B — that is, we get P C N larger than our observer actually finds it, so that, as seen from 0, the pole has another direction, as ■C P' P", giving the angle C P" B, equal to the angle AP B. But which of the three points P, P', and P", is the real polel They cannot all three be. Yet, if our traveller takes the observations made at A and B, he gets the point P by purely geometrical reasoning ; if he takes the obser- vations made at B aud C, he gets the point P" with equal reason ; and if he takes the observations made at A and C, he gets the point P'. He is forced, then, by this second line of argument, also, to abandon the notion that he has been travelling in [a straight line. He has now to consider what his observations require from him. He has first, to get the axis, B P, in Fig. 1, -coincident in direction with A P. He draws A N (Fig. 4) to repre- sent the line on which he set out from A, and he sets up A P at an angle of 51^° to A N. Then he draws at a convenient distance P' B parallel to A P, and, of course, meeting AN at an angle of 51.^''. Now, if he can draw an arc A B, touching A N at A, and having at ^ig. 4. B a direction (B N') making an angle of 57' with B P' then he knows that A B represents very satisfactoriU' the -curved path he must have followed when journeying from A to B. Then again he draws a third parallel, C P", at the same distance from B P' that B P' is from A P ; and he makes the arc B C (just as he made the arc A B) so that C N" may be inclined about 62i° to C P". This con- struction makes ABC the arc of a circle, because the circle is the only curve whose tangents (as A N, B N', C N") change equally in direction for points separated (as A, B, and C) by equal arcs. The observer is guided, therefore, to the belief that the section of the earth's surface along which he is travelling forms a circle. And he can roughly tell what the size of that circle is. For he has found that A 0 (Fig. 5) being about 7 GO miles, the tangent C N" has fallen away, in direction, about 1 1° from A N. But if AC L represent the circle of which A C is a part, he knows that lines O A and O C from the centre include the same angle between them as that by which C N" is inclined to AN.* Hence AC is an arc of about 11°. And therefore the complete circumference of this circle A C L is about 360 „ . ^pp X 760 miles, or in round numbers, some 25,000 miles. * This will perhaps be obvious at once to my readers ; but if not, they will easily see its truth by drawing K C M parallel to A N. Then, since 0 C N" is a right angle, the angle II C X" is the complement of K C 0. But K O C is also the complement of K C 0. Therefore, K 0 C is equal to M C S". Fig. 5. This gives to the circle a diameter of about 7,900 miles. In order, however, to test the justice of this view, our observer first travels farther north. He finds the slow change of elevation of the pole continuing quite uniformly as he continues journejing in that direction. After going as far north as he can, at which time he finds that the pole of the heavens is nearly overhead, he is satisfied that in this direction, at any rate, the circular figure of the path he has followed continues unchanged. He next returns to A, and commences a series of similar journeys towards the south. These confirm in every respect his theory that the section ho is traversing is either actually circular, or does not differ sensibly (so far as his instru- mental means are concerned) from the circular form. For every successive distance he travels there appears to be a proportionate depression of the pole. At length the pole sinks to the very horizoir, and the relations now presented by the heavens are so interesting that we shall have to consider them attentively. But first, we must exhibit the general results of our observer's voyages up to this point. We see from Fig. G, that even if our traveller's first observations were doubtful on account of the comparative smallness of the changes noticed, yet the great change he now notices — the apparent coincidence of the pole with the horizon — is altogether inexplic- able on the assumption that he has been traveUing in a straight line. For though undoubtedly by going very far indeed in direction A E he would bring the pole very low down, yet in the first place he would have to travel very much farther than he has actually done, in order that E P might seem horizontal, and in the second, it is absolutely impossible that the heavens should seem to revolve about A P when he was at A, and about a nearly horizontal line E P, when he is at E. On the other hand, we see from Fig. 7, how his uniform progression round the circular arc C B A E would lead to a uniform depression of the polar axis, until at E that axis appeared to lie (as Ep) in the horizon-plane of the observer at E. And then two things served very strikingly to confirm the views of the traveller. We see from Fig. 6 that on the assumption of the earth being plane, the pole of the heavens P has a distance from points on E C which is com- parable with the distances passed over by the observer. This being so, the stars which lay round the axis A P ought not only to change appreciably in brightnes.^ as the observer varies his position along E C, but they ought to change in relative position. The polar constellations, for example, could not possibly present the same aspect when viewed from A as when viewtd from E. But the observer can detect not the slightest change in the aspect of any one of the constellations he had become familiar with when at A, either in the brightness of the component stars or in their relative position. Now, Fig. 7 accounts perfectly for this. We see all the lines representing the polar axis parallel in position ; in other words, the pole is removed to a distance indefinitely great compared with the distances A B, B C, E A, ic. This makes the sphere of the fixed stars very large indeed compared with the arc E C ; and while this has been the direct result of geometrical con- siderations of another sort, it explains at once and simply, the striking fact that, let the traveller journey as he may 196 ♦ KNOWLEDGE ♦ [Sept. 5, 18b4. along distances which seem enornoous when counted by miles, he can yet detect no change whatever in the aspect of the several constellations. (To ie continued.) AN ADDRESS TO THE BRITISH ASSOCIATION (GEOGRAPHICAL SECTION), AT MONTREAL, 1884. By General Sir J. H. Lefrot, R.A., F.RS., Ac. THE subjoined extracts from General Lefroy's very able address comprise those portions of it possessing the greatest interest for the ordinary reader, as contradis- tinguished from the professional geographer pure and simple : — It is scarcely necessary to do more than allude here to the intimate relations between geography and geology. The changes on the earth's surface etfected within historical times by the operation of geological causes, and enumerated in geological books, are far more numerous and generally distributed than most persons are aware of ; and they are by no means confined to sea-coasts, although the presence of a natural datum in the level of the sea makes them more ob- served there. A recent German writer. Dr. Hahn, has enume- rated ninety-sbt; more or less extensive tracts known to be rising or sinking. We owe to Mr. R. A. Peacock the accumulation of abundant evidence that the island of Jersey had no existence in Ptolemy's time, and probably was not wholly cut ofl' from the continent before the fourth or fifth century. Mr. A. Howarth has collected similar pi oofs as to the Arctic regions; and every fresh discovery adds to the number. Thus the gallant, ill-fated De Long, a name not to be mentioned without homage to heroic courage and almost superhuman endurance, found evidence that Bennett Island has risen a hundred feet in quite recent times. Nordenskjold found the remains of whales, evidently killed by the early Dutch fishers on elevated terraces on Martin's Island. The recent conclusion of Pro- fessor Hull, that the land between Suez and the Bitter Lakes has risen since the Exodus, throws fresli light on the Mosaic account of that great event ; and to go still further south, we learn from the Indian survey that it is " almost certain " that the mean sea-level at Madras is a foot lower, i.e., the land is afoot higher, than it was sixty years ago. If I do not refer to the changes on the west side of Hudson's Bay, for a distance of at least 600 miles, it is only because I presume that the researches of Dr. Robert Bell are too well known here to require it. Any of my hearers who may have visited Bermuda are aware that so greatly has that island subsided, that great hangings of stalactite, unbroken, may be found dipping many feet into the sea, or at all events, into salt-water pools standing at the same level, and we have no reason to suppose the sinking to have come to an end. We learn from the Chinese annals that the so-called Hot Lake Issyk-kul, of Turkestan, was formed by some convul- sion of nature about 160 years ago, and there seems no good reason to reject the Japanese legend that Fusiyama itself was suddenly thrown up in the third century before our era (b c. 286). These are but illustrations of the assertion I began with, that geography and geology are very nearly connected, and it would be equally easy to show on how many points we touch the domain of botany and natural history. The flight of birds has often guided navigators to undiscovered lands. Nordenskjold went so far as to infer the existence of " vast tracts, with high mountains, with valleys filled with glaciers, and with precipitous peaks " between Wrangel Land and the American shores of the Polar Sea, from no other sign than the multitudes of Vtirds winging their way northward in the spring of lb79, from the Vega's winter quarters. The walrus-hunters of Spitzbergen drew the same conclusion in a previous voyage from the flight of birds toward the Pole from the European side. Certainly no traveller in the more northern latitudes of this continent in the autumn can fail to reflect on the ceaseless circulation of the tide of life in the beau- tiful harmony of nature, when he finds that he can scarcely raise his eyes from his book at any moment, or direct them to any quarter of the heavens, without seeing counties* numbers of wild fowl, guided by unerring instinct, directing their timely flight towards the milder climates of the South. From Central Africa it is not an unnatural transition to Central Asia, the region next the most inaccessible, and pregnant, perhaps, with greater events. The Russian project for diverting the Oxus, or Amu Darya, from the Sea of Aral into the Caspian, remains under investigation. We learn from the lively account of Mr. George Kennan, a recent American traveller, that there is more than one motive for undertaking this great work, if it shall prove practicable. He states that the lowering of the level of the Caspian Sea, in consequence of the great evaporation from its surface, is occasioning the Russian Government great anxiety ; that the level is steadily but slowly falling, notwithstanding the enormous quantity of water poured in hy the Volga, the Ural, and other rivers. In fact, Colonel Vcnukof says that the Caspian is drying up fast, and that the fresh-water seals, which form so curious a feature of its fauna, are fast diminishing in number. At first view there would not appear great difiiculty in restoring water communication, the point where the river would be diverted being about 216 ft. above the Caspian ; but accurate levelling has shown considerable depressions in the intervening tract. As the question is one of great geographical interest, we may devote a few minutes to it It is not to be doubted that the Oxus, or a branch of it, once flowed into the Caspian Sea. Professor R. Lentz. of the Russian Academie Imperiale des Sciences, sums up his investigation of ancient authorities by aflirming that there is no satisfactory evidence of its ever having done so before the year 1320; passages which have been quoted from Arab writers of the ninth century only prove, in his opinion, that they did not discriminate between the Caspian Sea and the Sea of Aral. There is evidence that in the thirteenth and fourteenth centuries, the river bifurcated, and one branch found its way to the Caspian, but probably ceased to do so in the sixteenth century. This agrees with Turkoman traditions. Even so late as 1869, the waters of the Oxus reached Lake Sara Kamysh, eighty or ninety miles from their channel, in a great flood, as happened also in 1850, but Sara Kamysh is now some 49 ft. lower than the Cas- pian, and before they could proceed further an immense basin must be filled. The difliculties then of the restoration by artificial means of a communication which natural causes have cut off, are (a) The disappearance of the old bed, which cannot be traced at all over part of the way ; (b) The possibility that further natural changes, such as have taken place on the Syr-Daria, may defeat the object : (c) The immense expenditure under any circumstances necessary, the distance being about 350 miles, which would be out of all proportion to any immediate commercial benefit to be expected. We may very safely conclude that the thing will not be done, nor is it at all probable that Seit. 5, 1884.] ♦ KNOWLEDGE ♦ 197 Russian finances -will permit the alternative proposal of cutting a purely artificial canal by the shortest line, at an estimated expense of 15 to 20 million roubles. There are few particulais in which the best atlases of the present day differ more from those published twenty-five years ago than iu the information they give us respecting the submerged portions of the globe. The British Islands, with the fifty and one hundred-fathom lines of soundings drawn round them, seem to bear a different relation to each other and to the Continent than they did before. The geography of the bed of the ocean is scarcely less interesting than that of the Continents, or less important to the knowledge of terrestrial physics. Since the celebrated voyage of H.M.S. Challeni/er, no marine researches have been more fruitful of results than those of the Talisman, and the Dacia. The first was employed last year by the French Government to examine the Atlantic coasts from Rochefort to Senegal, and to investigate the hydrography and natural history of the Cape Verde, Canary, and Azores archipelagos. The other ship, with her companion, the International, was a private adventure, with the commercial purpose of ascertaining the best line for a submarine telegraph from Spain to the Canaries. These two last made some .550 soundings and discovered three shoals, one of them with less than 50 fathoms of water over it, between the Con- tinent of Africa and the island. If we draw a circle passing through Cape Mogador, Teneriffe, and Funchal, its centre will mark very nearly this submarine elevation ; the other two lie to the north of it. The TnUs- man found in mid-ocean but 1,640 fathoms, among sound- ings previously set down as over 2,000 fathoms. Our knowledge then of the bed of the Atlantic, and of the changes of depth it may be undergoing, is but iu its infancy ; and we have only to reflect what sort of oro- graphic map of Europe we could hope to draw, by sounding lines dropped a hundred miles apart from the highest clouds, to be conscious of its imperfection. But this knowledge is accumulating, and whether revealing at one moment a profound abyss, or at another an unsuspected summit : marvels of life, form, and colour, or new and pregnant facts of distribution ; it promises for a long time to come to furnish inexhaustible interest. Canada comprises within its limits two spots of a physical interest not surpassed by any others on the globe. I mean the pole of vertical magnetic attraction, commonly called the magnetic pole, and the focus of greatest magnetic force; also often, but incorrectly, called a pole. The first of these, discovered by Ross in 1835, was revisited in May 1847 by officers of the Franklin Expedition, whose observations have perished, and was again reached or very nearly so by McClintock in 1859, and by Schwatka in 1879 ; neither of these explorers, however, was equipped for observation. The utmost interest attaches to the question whether the magnetic pole has shifted its position in fifty years, and although I am far from rating the difficulty lightly, it is probably approachable o\erland, without the great cost of an Arctic expedition. The second has never been visited at all, although Dr. R. Bell, in his exploration of Lake Nipigon was within 200 miles of it, and the distance is about the same from the Rat Portage. It is in the neigh- bourhood of Cat Lake. One of the finest feats of mountaineering on record was performed last year by Mr. W. AV. Graham, who reached an elevation of 23,500 ft. in the Himalayas, about 2,900 ft. above the sitmmit of Chimborazo, whose ascent by Mr. Whymper, in 1880, marked an epoch in these exploits. Mr. Graham was accompanied by an officer of the Swiss army, an experienced mountaineer, and by a professional Swiss guide. They ascended Kabru, a mountain visible from Darjeeling, lying to the west of Kanchinjunga, whose summit still defies the .strength of man. The reported outbreak of a new volcano in the northern part of West Australia, on August 25, 1883, in connection with the great eruption of the Sunda Straits, has not, as far as I know, been verified ; but the graphic description of the natives : "Big mountain burn up. He big one sick. Throw him up red stuff, it run down side and burn down grass and trees," seems to leave little doubt of the reality of the occurrence. THE ELECTRIC LIGHT IN THE MECHERNICH MINES.* THE electric-light installation at the Mechernich Mines in its once volcanic Eifel district in Rhenish Prussia, has now had a fair trial for more than three years, and has proved a complete success. The expectation that it would both facilitate the operations and increase their security, has fully been realised, and an extension of the i)lant is now being carried out. Messrs. Siemens and Halske, of Berlin, undertook the work, which was superintended on their behalf by Mr. Boeddinghaus. An open working 2,000 ft. long, 1,000 ft. wide, and over 300 ft. deep, in which 300 men and 20 horses are continually occupied, was first to be supplied with the electric light. This part of the mine is excavated in steps, the horizontal terraces being provided with rails. Ordinary lamps in globes on poles were out of the question, as blasting operations continue throughout the day, and the shots would soon have made havoc of the lamps. After several trials two powerful lamps, of 3,000 candles each, were erected at the upper margin of the pit, where they were fairly out of the reach of the projected stones ; and reflec- tors "were fixed to throw the light down upon the steps. To find the proper positions for these powerful lamps and to avoid too dark shadows caused some difficulty. But the illumination was finally rendered most efficient, and the open pit, with the light playing on the whitish grey rock, aflbrds a fine spectacle. As any interruptions, even for short periods, such as those occupied in renewing the lamp carbons, would be dangerous, the whole plant is double, each lamp receiving its current from a D;. dynamo. No hitch of any kind has occurred, and the safety of the miners has decidedly been augmented. It was formerly not always possible for the superintendents to see whether the loose mass resulting from the blasting operations had been properly removed, and frequent minor acci- dents arose from the debris falling down upon the miners engaged on the step next below. The work can now be controlled much better than before when petroleum lamps and hand lamps were in use. The cost shows a saving of about 4d. per hour in favour of the electric illumination. The satisfactory results obtained in the open working induced the company to introduce the electric light down in the subterranean galleries. The ore forms little concre- tions of sand and galena scattered all through the rock ; the whole mass has therefore to be brought to day to be disintegrated and sifted, and the mining proceeds in piiraUel and cross galleries, which are constantly being widened until they become 90 ft. in width, and 70 ft. in height, by sometimes 300 ft. in length. The operations in themselves would not require much light if there was not always danger threatening from loosened pieces of rock. Pitch torches were formerly employed to examine the bore- holes and fissures round them after each explosion. * From Engineering. 198 • KNOWI.EDGE . [Sept. 5, 1884. It was a question whether the arc lamps would answer for this purpose in the smoky atmosphere. For the first experiments, arc lamps of 3,000 and 1,000 candles were used, with the positive carbon in the lower holder. The effect was brilliant, yet the light did not penetrate the white smoke cloud which collects at the upper wall immediately after the shot But as the smoke settles within ten minutes, it was thought advisable to acquiesce in this interruption of a few minutes, and to use smaller lamps of 350 candles, which proved quite efficient. Of these, there are ten in use, with about 10,000 ft. of lead cable, the cable being partially elastic, as the lamps with their wires have to be removed when the blasting is to take place. The lamps were originally supplied with hexagonal lanterns with obscured glass to protect the eyes of the miners. The glasses were, of course, soon broken, but no complaints are said to have been made about the naked electric lights. The proprietors of the mine have decided upon an extension of the installation. OPTICAL RECREATIONS. By a Fellow of the Royal Astronomical Society. (Continued from page 130.) IN all that has preceded, we have, so to speak, taken sight for granted. Before, however, proceeding to examine the phenomena which essentially depend upon the very way in which we see at all — e.g., those of binocular vision and the like — it will be necessary to enter into a little elementary explanation of the structure of the eye itself. The student who may wish to follow this subject out in detail must consult some of the larger textbooks on Human Anatomy. It will conduce to a better appreciation of our description if he will obtain a fresh sheep's or bullock's eye from the butcher. We shall remark in the outset that the eye-ball is very nearly globular, but the front part (Fig. 25) is more convex than the other portion. Now, excepting this front pro- tuberant part, the eye will be observed to be covered by a Cliomi'd Crustalhn cLcns- Cornea Ins OpticXcrve ei'Olicr Fig. 25. thick white membrane called the sclerotic coat, which is popularly known as " the white of the eye." The front of the eye is enclosed by a thick, strong, glassy membrane called the cornea, which suggests the idea of a watch-glass. The light quite obviously passes into the eye through the cornea. From the circle of junction of the cornea and the sclerotic, a kind of opaque coloured plate, with a hole io the middle, separates the front clear part of the eye from the main portion of the interior of the eyeball. It is called the iris, and it is the colour of the iris, which is spoken of as that of the eye, when we talk about blue eyes, grey eyes, brown eyes — and so on. The hole in the centre of this iris is known as the pupil. This appears jet-black, because we look through it at the dark interjor of the eye-ball. The function of the pupil is to admit 1 ight, and further to regulate the amount of light so admitted. It contracts in the presence of a bright light, and expand s in partial darkness — a fact of which the reader may satisfy himself by standing before a looking-glass in a dim light, and watching the pupils of his own eyes when a candle or lamp is suddenly brought near them. The same result may be attained in daylight by shutting the eyes close and opening them suddenly before a mirror. This is all that we can make out from the exterior of the eye. We must dissect it (preferably under water) if we wish to under- stand its internal structure. Doing so, we shall find that the sclerotic is lined by the choroid membrane, of a dart brown or black colour ; as is that again in turn by the retina : the latter being nothing but an expansion of the- optic nerve after it enters the eye from the brain. The choroid coat at the front of the eye splits into two layers, one going to form the iris already spoken of, the other taking the shape of a kind of pleated curtain. To this is attached the crystalline lens — an absolutely transparent, double-convex lens, between which and the cornea lies a clear liquid called the aqueous humour , while the greater portion of the cavity of the eye — that behind the crystalline lens — is filled with a transparent, gelatinous substance- known as the vitreous humour. Our figure above should" make this short description intelligible. From it we gather that the eye consists in effect of an optical instrument, like- the camera obscura (Fig. 2, Vol. V., p. 306, and Fig, 20, Vol. VI., p. 46), in which an image formed by the refrac- tion through a combination of lenses of the rays of light emanating from various external objects is projected on to the back of the eye, and being there received on the retina, is conveyed by the optic nerve to the brain. That such an image is formed on the retina, the student may satisfy him- self by carefully scraping the back of a bullock's eye (under water) until it becomes thin enough ; when, on holding the eye u[) with the cornea directed to the window, or a well- lighted landscape, a charming little picture of the object towards which it is directed may be seen on the semi- transparent screen to which the hinder part of the eye has been reduced. It -will be noted that this image is inverted, and a large amount of unprofitable discussion has arisen as to why we do not see external objects upside down (as though we had another eye at the back of the first one to view the image formed by that !). The fact is that we do not see anything in the eye, but something wholly external to it. For it is the brain, after all, that sees, and Fig. 26. not the eye. Sever the optic nerve, and utter and absolute blindness instantly supervenes ; albeit the eye, as an optical instrument, remains intact In the sensorium we refer any object to the direction in which the light from it reaches the eye. If we have to raise the head, as to view the zenith, we say the object regarded is above us or up ; if we have to depress the head, as in looking at the ground, we say that the object is beneath us or down. The so-called " mystery " of inverted vision is then, in reality, no mystery at all. Various illustrations may be found of this reference by the brain (through the optic nerve) of external objects to the direction whence the light they emit or reflect enters the eye. For example, press the comer of the eye with the finger, and a patch of light will appear as existing in the direction of the pressure. Look at the bright sky, preferably through an astronomical telescope. Sept. 5, 1884.] ♦ KNOWLEDGE * 199 and specks will often be seen floating about,'seemingly in the heavens, and travelling slowly downwards. When these assume the appearance of minute transparent spheres, they become a source of annoyance to the observer of small stars in daylight, whose appearance they simulate. They are really extremely minute specks floating in the vitreous humour (Fig. 25). Or the very curious and instructive experiment devised by Purkinje may be tried. It is thus performed : You take a lighted candle into an otherwise totally darkened room ; shut the left eye, and hold the candle as close as you can to the right eye (say three inches from it), to the right and rather in front, so as to light up the retina strongly. Keeping the right eye steadily fixed on the opposite wall, you move the candle about into various positions. Now, the glare of the light will soon cause the field to appear dark, and then, as the gentle motion of the candle continues, suddenly there starts into view on the wall a strange ghostly kind of branching net-work, or thing like the upper part of an oak-tree when the leaves are ofT in winter. This is really an image of the blood-vessels of the retina. They enter the eye at the same point as the optic nerve, and spread out over the sensitive surface of the retina. The candle casts their shadows upon it, and they are projected, and seem to exist on the opposite wall. The words " sensitive surface of the retina," which we have just written, suggest to us to remark that the retina is by no means equally sensitive over its whole area ; in fact, that, as we shall immediately see, there is one spot in it which is absolutely blind or insensitive to light, while in another the greatest exaltation of visual perception obtains. In the axis of the eye is situated what is known as the central spot, a thinning or actual depression of the retina. If we look out over an expanse of country without moving the head or eyes, we shall observe certain objects immediately in front of us, sharply and brilliantly defined ; but if we attend a little, we shall note that, as we recede from them, either to the right or the left, upwards or downwards, every- thing becomes gradually less distinct, and with a more im- perfect outline, so that at any considerable angular distance from the point of sharpest vision things become blurred and amorphous. In practice, and unconsciously, we shift the eyes, and so successively take in the various details of the landscape, which we fancy we see altogether ; albeit, as we have explained, we do nothing of the sort. The central spot, of which we have spoken above, is the seat of the sharpest vision. On the other hand, the place where the optic nerve enters the eye-ball is utterly insensitive to light, and hence is known as the blind spot Fig. 20 will enable the reader to verify its existence in his own eye for himself. Let him shut the left eye and steadily regard the little cross with his right one, say at a foot or eighteen inches distance. He will see both the cross itself and the dark disc perfectly. Now, let him slowly bring the page nearer to Ins face, and at a certain point the circular disc will vanish and the paper appear white. At this instant the image of the disc has fallen upon the blind spot of his right eye. An he continues to approximate the paper to his eye, the disc will once again reappear, its image now falling upon another sensitive part of the retina. (To he continued.) Thirty-kive years ago the ratio of railway passengers killed in the United Kingdom from causes heyond their own control was one in 4,782,000, while last year it was one in 61,810,000. In 18S3 only eleven persons were killed from causes beyond their control. As compared with this, upwards of 200 persons are annually killed in the streets of London. HOW AMERICAN CARP ARE DESTROYED. THERE is a little plant, common enough in our ponds, and known as the bladder-wort, which has suddenly sprung into importance for breeders of carp. The bladder- wort (genus Utrimlaria) is a rootless plant fond of still water, and usually found floating half in and half out of water, the branching and stem-like leaves forming the submerged float from which rises the flower stem. To the leaves are attached curiously insect-like bladders filled with water, and varying in size in the difiisrent species, reaching at times a diameter of one-fifth of an inch. It was formerly, and with much probability, supposed that these bladders served the purpose of floats ; for until a few years ago it was taken for granted that air and not water filled them. It is now known, however, that the bladders serve a more useful purpose than merely to keep the head of the plant above water ; they are the digestive organs of the Utricularia, and at the same time are so constructed as to form a very ingenious but extremely- simple trap for catching food. It is into these bladders A. Bladder (with small fish caught). B. Longitudinal section of bladder. C. Branch showing leaves and bladder. that thousands of carp eggs find their uuwitting way, to- gether with many insects, Crustacea, and other tiny objects, both animate and inanimate. It is only recently that the Ulricularia has been accused of destroying carp eggs, but for nearly thirty years it has 200 ♦ KNOWLEDGE ♦ [Sept. 5, 1884. been known as a receiver of small insects and crustaceans, and it has been known as an insect feeder for at least twenty years. Mrs. Treat, of America, in 1875 gave a full and interesting description of the habits of one species {Utricularia clandestina), and Darwin and others, of Europe, studied the habits of other species in Europe and elsewhere. In its character as an insectivorous plant the bladder- wort might fail to arouse general iuterest, but as a des- troyer of carp it has a commercial as well as botanical and scientific character. The common bladder-wort {Utricularia vulgaris) affords the easiest subject for study, inasmuch as its bladders reach the largest size and may be satisfactorily examined with a moderate magnifier. The bladder is pear-shaped, with an opening at the small end. Around the mouth are anteniue like projections or bristles, which, according to Darwin, are for the purpose of warding off and keeping out insects of too great size. The mouth is closed hy a valve which yields readily to light pressvire, but offers an immovable barrier to the once captured creature. The utmost strength compatible with such a structure has apparently been attained. The valve is a thin and transparent plate, and, by means of the water behind it, is made to stand out a bright spot, which Darwin thinks may attract prey. Something certainly attracts the tiny denizens of the water, for they swim up to the mouth and crawl into the bladder by the readily yielding door. As there is no seductive seci-etion here, as in the case of many insect-destroying plants, the great naturalist's surmise is probably correct. Some of the insectivorous plants, on catching their prey, at once pour out a digestive fluid analogous to the gastric juice of the human stomach, but with the Utricularia it is not so. The insects or other food when caught in the bladder are merely captives, and swim about in their con- fined quarters with eager activity in their endeavour to find an outlet, until asphyxia for lack of oxygen comes on. Even now the plant makes no effort to digest the animal food, but waits patiently until decay takes place, and the animal matter is by putrefaction resolved into fluids which the numerous papilla; lining the bladder can absorb. Darwin's experiments showed not only that living animals could make their way into the bladder, but that inanimate objects falling on the valve would be engulphed with lightning-like rajjidity. With all this information to begin with, it is not strange that naturalists should turn to the bladder-wort to seek a solution for the great destruction of the carp, for the carnivorous plant was known to possess facilities not only for the capture of floating spawn, but even of tjie newly hatched fish. Examination and repeated experiment proved conclusively that the greedy little bladders were making sad havoc with the fish, and in con- sequence carp breeders are bidden to open war vigorously on Utricularia and all its species. It may seem at a hasty glance that the small bladders can hardly be responsible for any very extensive destruction of eggs or small fish, but the doubters of the ability of insignificant agents, acting together, to produce stupendous effects may be referred to the microscopic rhizopods or the earth worms, each in their own way performing vvonderful feats in the way of earth building and earth preserving. — Scientijic American. Catalpa Ties. — The catalpa ia already in use in the south-west of the United States, to some extent, for railwaj' ties. It is a wood of rapid growth, and yet has shown lemarkablo durability. In an address before an agricultural society in Ohio, General Harrison, of Indiana, mentioned a catalpa foot-log over a small stream in the Wabash county which had been in use for 100 years, and was still sound, showing no aign of decay. OTHER WORLDS THAN OURS. A WEEK'S CONVERSATION ON THE PLURALITY OF WORLDS. By Mons. de Fontenelle. with notes by eichard a, peoctoe. THE SECOND EVENING {continued). " T FIND," says the Marchioness, "the planets are just X like us ; we cast that upon others which Ls in our- selves. The Earth says, ' 'Tis not I that turn, 'tis the Sun ; ' the Moon says, ' 'Tis not I that shake, 'tis the Earth ; ' the world is full of error." " But I would not advise you," said I, " to undertake the reforming it ; you had better convince yourself of the entire resemblance of the earth and the moon. Imagine, then, these two great bowls suspended in the heavens. Yon know that the sun always enlightens the one half of a body that is round, and the other half is in the shadow. There is, then, one half of the earth, and one half of the moon, which is enlightened by the sun — that is, one half which is day, and the other half which is night. Observe, also, that as a ball has less force after it has been struck against a wall, and rebounds to the other side, so light is weakened when it is reflected. The pale light which comes to us from the moon is the very light of the sun ; but it cannot come to us from the moon but by reflection. It has lost much of the force and lustre it had when it came directly from the sun upon the moon ; and that bright light which shines directly upon us from the sun, and which the earth reflects upon the moon, is as pale and weak when it arrives there, so that the light which appears to us in the moon, and which enlightens our nights, is the part of the moon which has day ; and that jiart of the earth which has day, when it is opposite to the part of the moon which has night, gives light to it. All depends upon this, how the moon and the earth behold one another. At the beginning of the month we do not see the moon, because she is between the sun and us ; that half of her which has day is then turned toward the sun, and that half which has night is turned towards us ; we cannot see it then, because it has no light upon it : but that half of the moon which has night, being turned to the half of the earth which has day, sees us without being perceived ; and we then appear to them just as the full moon does to us. So that, as I may say, the people of the moon Lave then a full earth ; but the moon being advanced upon her circle of a month, comes from under the sun, and begins to turn towards us a little corner of the half which is light ; which is the crescent : then those parts of the moon which have night, do not see all that half of the earth which has day, and we are then in the wain to them."* "I comprehend you very well," said the lady; "the people in the moon have a month quite contrary to us ; when we have a full moon, their half of the moon which is light, is turned to our half of the earth which is dark ; they do not see us at all ; and they have then a new earth, this is plain. But now tell me how come the eclipses 1 " " You may easily guess that," said I ; " when it is new moon she is between the sun and us, and all her dark half is turned towards us who have light, that obscure shadow is cast upon us ; if the moon be directly under the sun, that shadow hides him from us, and at the same time obscures a part of that half of the earth which is light ; this is seen by that half of the moon which is dark : here * Fontenelle omits to notice here the varying aspect of the eart\> to the moon, as rotation turns different parts of her surface moon- wards. But he touches on this point in the next chapter. — K. P. Sept. 5, 1884.] ♦ KNOWLEDGE ♦ 201 then is an eclipse of the sun to us during our day, and an eclipse of the earth to the moon during her night. When it is full moon the earth is between her and the sun, and all the dark half of the earth is turned towards all the light half of the moon ; the shadow then of the earth c£ista itself towards the moon, and if it falls on the moon, it obscures that light half which we see, which has then day, and hinders the sun from shining on it. Here then is an eclipse of the moou to us during our night,* and an eclipse of the sun to the moon during her day ; but the reason that we have not eclipses every time that the moon is between the sun and the earth, or the earth between the sun and the moon, is because these three bodies are not exactly placed in a right line ; and by consequence that which should make the eclipse, casts its shadow a little beside that which should be obscured." " I am surprized,' said the Marchioness, " that there should be so little mystery in eclipses, and that the whole world .should not know the cause of 'em." " They never will," said I, " as some jieople go about it In the East Indies, when the sun and the moon are in eclipse, they believe a certain devil who has black claws, is seizing on those planets with his talons ; and during that time the rivers are covered with the heads of Indians, who are up to the neck in water, because they esteem it a very devout posture, to implore the sun and the moon to defend them against the devil. In America, they are persuaded that the sun and the moon, when eclipsed, are angry, and what is it they will not do to be reconciled with them 1 The Greeks, who were so refined, did they not believe the moon was enchanted, and that the magicians forced her to descend from heaven, and shed a dangerous juice on the plants ■? Nay, what a panic were we in, not many years ago, at an eclipse of the sun 1 How many people hid themselves in their cellars ; and all the philosophers could not persuade them to come out till the eclipse was overl" "Methinks," said she. "'tis scandalous for men to be such cowards ; there ought to Ije a general law made to prohibit the discoursing of eclipses, that we might not call to mind the follies that have been said and done upon that subject." " Your law then," said I, " must abolish even the memory of all things, and forbid us to speak at all, for I know nothing in the world which is not a monument of the folly of man." (To be continued.") MUSCULAR CONTRACTION AFTER DBATH.t DR. BROWN-SfiQUARD maintains that lixed and rigid positions after death, speedily ensuing, are due to the last vital act, which has induced a " tonic contrac- tion," and that causes of death which produce sudden dissolutions without pain or excitement may be the means of such a contraction. Assuming this to be true, still the modus operandi by which a vital act can leave such a " tonic contraction " after all vital power has ceased is not suggested by him, and we need one step further in the way of en- lightenment. Let us see if we cannot take that step now. In accordance with the observations of Du Bois Reymond, it has been pretty generally accepted that the normal state of even quiescent living muscle is one of electrical tension, and that during muscular contraction the tension diminishes Or rather, daring the night of the parts of the earth turned moonwards. — E. P. t From the Scientific American. in such a way that as the wave of contraction moves along the muscle it is preceded by a wave of negative variation. This variation is slight for a single contraction, but in those of great rapidity it may become so great as to completely neutralise the galvanometric deflection due to the normal current of the quiescent muscle. These views have been attacked and sharply criticised, notably by Hermann in 1807, and as lately as 1877 Engel- mann has come to Hermann's aid in Pfluger's "Archiv." They maintain that normal muscle-currents do not exist ; and that those observed by Du Bois Reymond were due to the unnatural conditions of the muscles examined by him. He, however, has replied to their criticisms with great ability, and his views are now, as already stated, very gene- rally adopted by physiologists. A consideration of these views may perhaps hel[i us to a clearer idea of the position of the headless soldier of Sedan, as shown in Brown- Sequard's figure. The conditions required, in order that a limb or the entire body should be in a state of rigidity, are simply that the antagonistic muscles, the flexors and extensors, for instance, should be braced at the same moment to full activity, and the rigidity continues so long as the mutual action remains. If this action is not local, but general, such a figure will continue without motion indefinitely, excepting that gravitation may cause it to fall to the ground, if unsupported. But even such a fall would not aflTect the limbs : they would necessarily retain their position. Now Du Bois Reymond has shown us that tonic contrac- tion is the normal state of muscle fibre, and that relaxation is due to an accession of vital activity through the agency of nerve force. We know well that commonly when life ceases muscular contractility ceases with it. And we can readily see that when death comes as the result of disease or exhaustion, and is attended with suflfering, the pertur- bation of nerve force and of muscle currents must be so great that such a result wUl surely follow. And as these include death in almost every form in which we ever witness it, we have naturally come to understand that mus- cular relaxation is its normal attendant and its immediate result "He bowed his head" is the fearfully expressive term employed when death came on Calvary. But in the very few instances where death occurs suddenly and without suffering, it seems possible that the instanta- neous cessation of the nerve force may leave every muscle fibre in its normal condition. If that could be, universal rigidity would instantaneously ensue, and the last position assumed in life Wduld be retained in death. Now, we know that the one cause of all causes which can bring a death into which the element of time does not enter is a wound which obliterates the base of the brain as well as the commencement of the spinal cord. That there is an interval between the cause and efl!ect is doubtless theoretically true, but practically the interval has no existence, for it is infini- tesimal. Such a stroke must necessarily be painless, for life (including of course sensation) is abolished at its occur- rence. The two chief eases cited by Brown-Sequard are cases precisely in point. The cannon-ball at Sedan left nothing remaining above the lower jaw. The brain of the soldier at Goldsborough had been swept by a bullet from a Springfield rifle, that struck him in the right temple, while his head was turned toward his right shoulder, and beyond question inclined downward, for his leg had that instant crossed the saddle, and the stock of his own rifle was still on the ground. Following Du Bois Reymond, it is diificult to see how instantaneous rigidity should not ensue in each of these cases ; it did ensue, whether our explanation be correct 202 KNOWLEDGE ♦ [Sept. 5, 1884. or not. And with each one the state of support was such that he could not fall so long as the rigidity continued. Many questions and conclusions of intense interest are rassocialed herewith, but for the present we must leave them untouched. W. A. O. THE INTERNATIONAL HEALTH EXHIBITION. XIV.— WATER AND WATER-SUPPLIES— (conlinwect). IN our remarks upon the " Grant Revolving Ball Water Filter," we drew the attention of our readers to this remarkable contrivance as being one which is peculiarly adapted to the purification of tolerably wholesome water, and in doing so provoked a reply from the inventor, who, it is but just to state, has furnished us with ample evidence that the instrument is capable of dealing effectively with *ven filthy and highly impure waters. We have tested the apparatus, and find the filtrate of our experiments all that could be desired for drinking and for culinary purposes. In cleansing the filter by reversion of the ball, it is some- what surprising to find, in spite of all theoretical rea.soning to the contrary, that the carbon is not approximately, but thoroughly cleansed, and the operation is so simple that it raay be put into action every time that the filter is used, although in reality it does not require such attention more than once or twice daily. On a large scale, these filters might be fixed with ad- vantage to public drinking-fountains and street-service hydrants, as suggested by the Home and Colonial 2rail,* when " the policeman on his beat could cleanse them at intervals by merely turning a handle in passing. This handle could be constructed, in filters destined for public hydrants, to allow of its being locked, to prevent damage from mischief." Type IV.—" The Spongy Iron Filter."— The researches ■of Prof. Gustav Bischof, which led to the employment of -spongy iron as a filtering medium of value, are carefully recorded in the " Proceedings of the Royal Society,"! and •one of the most important benefits derived from its use is shown to be due to its destructive action upon organic germs. In his report to the company. Professor Frank- land, F.R.S., writes as follows: — +" Taking into account the extremely bad quality of the raw material at the time of my visit, I consider this result to be eminently satisfac- tory from a purely chemical point of view ; but there is another factor involved in this result which has still greater weight with me in the comparison of the water before and after treatment, viz., the circumstance that the water has Ijcen passed through a material which is absolutely fatal to bacteria and their germs. It has been proved by Prof. Bischof § that water which has passed through spongy iron is entirely free from bacterial germs, and by my pupil, Mr. F. Hatton, working in my laboratory, that spongy iron is the only known substance applicable to the treat- ment of large volumes of water which immediately destroys living bacteria. "II We need scarcely add that the immunity from zymotic disease, secured through the use of so valuable an apparatus, ought to be a powerful argument in favour of its general acceptance as a household necessity. The internal mechanism of the filter may be readily understood by a reference to the figure here annexed * July 18, 1881, p. 5. t " On Putrescent Organic Matter in Potable Water," No. 180, 1877; No. 186, 1878. X Report to the Directors of the " Spongy Iron Water and Sewage Purifying Co.," August 8, 1882. § Op. cit., xxvii., p. 258. ]| " Journ. Chemical Society," x.'vxi.'i.. p. 2i7. (Fig. 27), from which it will be gathered that it is entirely different in plan from any of the appliances which we have hitherto noticed. The following description, which hae been kindly furnished to us Vjy the company, will enable the reader to gain an insight into its detailed structure : — " (1) The unfiltered water is supplied by means of ball-cock, Fig. 27. — Bischof's Spongy Iron Special Ball-cock Filter. B., ball- cock ; U., unfiltered water; V., ecrew-valve; I., spongy iron; S., S'., S"., prepared sand ; F., filtered water; T., stop-cock. B, with glass-ball, G, and screw-valve, V ; the latter serves to shut off the water in any emergency. The ball-cock requires no fixing to a wall, but is fastened to the side of the filter-case by screws, R ; it is connected with the water- supply or cistern by india-rubber or other tubing, P. The water passes through the several layers of filtering materials, which are enclosed betweeu the perforated plates, C, C', C". It is next collected in a small well, or regulator bowl, and thence passes into a tin tube, provided at its outer end with a screw-cap, A. The lateral opening, X, in the side of the tube forms the only communication between the upper part of the filter and the reservoir for filtered water. The flow of water is thus controlled by the size of such opening. (2) The supply of water to this filter should be sufficient to insure the materials remaining covered with water." Spongy iron is metallic iron in a state of excessively fine division, which renders it sufficiently porous to admit of the percolation of water. It takes the place of the carbon of other filters, and acts virtually in the same way. Apart from its obvious property as a mechanical strainer, it is a chemical purifier. It counteracts lead contamination,* reduces the hardness of water,! and, as we have before noted, is strongly antise])tic as far as organic matters are concerned. Mr. F. Hatton has shown : — I (1 ) " That it acts as a very powerful reducing agent on the carbon compounds composing the organic matter dissolved in water. In some cases marsh gas itself was produced — probably the organic matter was first oxidised to carbonic acid (C0„), and then the action of the metallic iron on this gas gave rise to marsh gas (CH^) by the ordinary decomposition of water. (2) The organic nitrogen is in nearly all cases reduced to ammonia." In its passage, the water dissolves a small quantity of * " Joiu-nal Eoval Agricultural Society," vol. xi., part 1, 1875, p. 158. t " Rivers Pollution Commission," 6th report, p. 220. I " Journal Chemical Society," May, 1881. Sept. 5, 1884.] ♦ KNOWLEDGE 203 the iron, but this is abstracted and retained by the layers of prepared sand undorneatb. The entire filter is thus cDmposed from below upwards of : — (1) A perforated plate 0", Fig. 27. (2) Fine gravel, S". (3) Coarse white =and, S'. (4) Black pyrolusite, S. (5) Interoiediate per- forated plate, C. (G) Spongy iron, I. (7) An upper per- forated plate, C. It thus appears that, as the entire system is constituted by a series of inorganic substances, the liability to decomposition of the filtering medium is entirely dispensed with, and, in consequence, a renewal need not be resorted to more than once in twelve months. The tiiter may then be taken to pieces, thoroughly cleansed, and recharged, by following the simple directions supplied with each instrument. Type V.—" The Patent Carbon Paper Water Filter," Fig. 'JS, manufactured by Messrs. S. H. Johnson & Co., of Stratford, London, E., is constructed upon the principle of combining a theoretically perfect mechanical strainer with a chemical purifier of the highest value. Both of these requirements are premised to he but temporarily obtainable, and bearing this in mind the inventors have sought to produce an instruajcnt which shall fulfil all the duties of a perfect filter with the materials at hund, which can be iriexpensively and readily renovated. *^#,.fe'v: Fig. 28. Stout filter -paper, into which a quantity of purifie(f animal charcoal (from 10 to 20 per cent, of its weight) has been incorporated, is held within a chambered frame- work, and operates by means of the pressure in the main- service or household supply pipe. The body of the appa- ratus consists of a series of apposed compartments, each designed to hold two circular discs of the prepai'ed paper, so that a six-chambered instrument, such as that shown at Fig. 28, would contain tweh-e of such filtering suifaces. The unfiltered water passes in at one side, and, after nitration, flaws into the supply-pipe under pressure. The substitution of fresh papers is provided for thus : — " The filter can be shut off on both sides from the service-pipe, a small disc run back, and the grooved plates and distance- frames of which the filtering chambers consist can be opened out, and the spent carbon papers changed in the course of a minute or two. When screwed up the machine is again ready for work." The entire arrangement is a novel device, and practically .'•upports the theory upon which it was con- structed, and which we have already enunciated. New Zkalaxd Coal. — The coal trade of the north island of Xew Zealand promises to be extensive. Coal is found at the Bay of islands, where a mine is in full operation. At Whaugharei two mines are at present working ; at Raglan coal of good quality has recently been found, and at the Mokau a seam of excellent coal is seen cropping out to a great thickness for a distance of between twenty and thirty miles. Besides these places, coal is now being worked to a considerable extent at several points on the Waikato, and a large seam of coal — between 50 It. and 6U ft. in thickness — on the estate of the late Mr. Foots, on the Maramarua Creek, is ex- pected to become a source of supply shortly. editorial (gosJsifp. A LESS sensational Presidential address than that of Lord Rayleigh to the British Association this year it would be difficult to imagine, and yet it is not without interest for those outside of the comparatively narrow circle of specialists in physics, to whom it primarily appeals. Among the more notable points in it I may refer here to Crookes's masterly discovery of the element Yttrium by the pre- sence of a bright band in the phosphorescent spectra of cer- tain earths, and the proof thence derived of its compara- tively wide distribution. The researches, again, of Abney in the ultra-red end of the spectrum, Langley's conclusion (already adverted to in these columns) that the sun would appear of a blue tint if viewed by an eye situated outside of our atmosphere, and the description of Cornu's method of determining whether any given line in the solar spectrum has its origin in the sun or in our own atmosphere must command the attention of all who possess the slightest familiarity with the theory, or practical use, of the spectro- scope. Michelsen's final determination, too, of the velocity of light as 186,290 miles per second will be accepted with interest by all concerned in the study of cosmical or astro- nomical phenomena ; while, finally, Lord Rayleigh's brief discussion of the tendency and methods of modern educa- tion can scarcely fail to be valuable to a very large number indeed to whom the very British Association itself is but an entity of the vaguest and most shadowy kind. " There was," says the Book of A^onsense — " There was an old person of Phila^ Whose conduct was scroobious and wily " — conduct which apparently finds very sedulous imitation in certain gentry who try to pufl' themselves in journals weak enough to fall into the trap they set for them. I may select two illustrations of this of which I have had recent experience. The first is that of a so-called " Spiritualistic " paper which has been moving heaven and earth to provoke me into a discussion, with the sole object of getting a gratuitous advertisement in the columns of Knowledge. Its failure to do so has driven it nearly frantic ; but, surely, in vain the net is spread iu sight of any bird. The second eflbrt to use this journal comes from a gentleman who has invented something — -what, I decline even to hint : but will suppose, for the sake of illustration, that it is an im- proved hair-pin. Well, the inventor writes to me asking for an appointment that I may see his hair-pin ; and goes on to suggest that I should (of course, by puffery) aid him to introduce it into ladies' schools " for our mutual advan- tage." It affords an instructive notion of the idea which such a person must entertain of the social status, habits, training, and ethics of the editor of a scientific paper, to suppose that he would misuse its pages for the sake of the proiit to be got out of selling hair-pibs (or anything else) on commission ! I SEE that the 2i0th minor planet was discovered on the night of the 28th ult. at Marseilles. It is much to be deplored that the astronomers at the Observatory there had not something more profitable to occupy themselves with. In addition to the letter printed on p. 206, I have re- ceived another from Dr. Kinns, complaining of the para- graph on p. 142, and containing scarcely veiled threats of what he will do if I do not apologise to him. Such threats trouble iiie but little indeed ; but Dr. Kinns — and every one else — is entitled to the most rigid justice; and I 204 ♦ KNO\VLEDGE ♦ [Sept. 5, 1884. am earnestly anxious that he should have it. When a man voluntarily publishes a book, he, ipso facto, sub- jects that book to the most searching, and, if need be, damaging criticism (always supposing such criticism to be honi% fide, and without malice) ; nor does the patronage of Lord Shaftesbury, or even of the Lord Mayor himself, exempt him from unfavourable comment. To two expressions in the paragraph in question Dr. Kinns takes especial exception. The first is this : " He claimed to have the sanction and support of, inter alioa, members of the staff of the British Museum, but this was promptly denied and repudiated by more than one leading mem- ber of that staff themselves." The members of the staff who do appear to support Dr. Kinns are Dr. Birch and Mr. Pinches ; who are, doubtless, ex- cellent judges of the faithfulness of a translation of a cuneiform inscription, but whose authority as astronomers, physicists, geologists, and palwontologists may reasonably be questioned. As for the repudiation by the Natural Science staff of the Museum, see Mr. Carruthers' letter in the Standard of Jan. 4, 18Si, and the mass of correspondence which appeared in that journal, the Times, ic, about, and subsequently to, that period, together with Dr. Kinns's replies. The next expression to which Dr. Kinns objects is " crass ignorance," which he alleges is calculated to do him serious injury. As I would not wilfully injure a human being, and assuredly not a total stranger to me, I withdraw that expression entirely, and invite Dr. Kinns himself to substitute for it, in these columns, his own definition of the mental condition of a man who could believe that refraction, in any form what- ever, could cause the sun to appear above the western horizon after the rotation of the earth had carried it — not only beneath the observer's feet — but actually to its point of rising 180° distant! I must, in fairness, add that, at the time of my penning these lines the new edition of Dr. Kinns' book has not reached me. Should it do so before going to press, and I find that the astounding statement to which I have just referred has been expunged from it, I will take care to give the fact all the publicity in my power. Dr. Kinns seems to be labouring under the curious hallucination that his private character and personal honour have been attacked. No such utterly baseless charges were ever brought (or would for a single instant have been suf- fered to have been brought) against him in these columns. It was his judgment as an author, and that alone, which was assailed, in conjunction with the policy of the action of his committee. Celestial Motions : a handy book 0/ Astroitomi/. By TV. T. Lynn, B.A., F.R.A.S. Second Edition. " (London: Edward Stanford, 1884.) — Scarcely two monthshave elapsed since our first notice of Mr. Lynn's capital little book, and already the first edition is exhausted. In the second, the two or three printer's errors, &c., which we noticed in p. 483 of our la.'it volume have disappeared, all numerical and other detail is brought down to the very latest date, and a diagram of the orbit of the November meteors has been added. Mr. Lynn's tiny volume has honestly earned the success it has met with. London Wafer : A Review of the Present Condition and Suggested Improvements of the Metropolitan Water Supply. By A. DE C. Scott, Major-Gen eral late R.E. (London: Chapman &, Hall. 1884.) — When we read on the first line of General Scott's work that, even in 1882, in addition to the supply from private wells, London consumed daily 140,130,000 gallons of water ! the vast importance of the subject which he undertakes to discuss is irresistibly forced upon us. He gives us a .succinct history of the Metropolitan Water Supply ; and shows very plainly in what respects it breaks down ; discusses the various schemes proposed for furnishing a supply of pure water — such as Mr. Bateman's for bringing it from South Wales, Messrs. Hemans and Hassard's, for deriving it from the Lake District; Mr. Fulton's, for obtaining it from the Wye, ic, as well as the idea of Messrs. Homersham and Barlow for sinking very deep wells within the area of the metropolis itself. He appears to be pretty definitely of opinion that the monopoly of the Water Companies has been abused, and that the sooner it is destroyed the better. General Scott's book deserves the attention of every water-consumer in London. Raihvay Accidents. By Clement E. Stretton. Third Edition. (London : Simpkin, Marshall, fc SutclifEe, with most satisfactory results. The size of the tube well is 7i in., and at 81 ft. the chalk springs are so abundant that the yield is over 100 gallons per minute, or about 150,000 gallons per day. The pnmping, when necessary, can be continued night and day with a very small amount of attention, as the motor is a powerful water-wheel worked by the river Lea. This well affords a further illustration of the fact stated by Mr. Robert Sutcliffe at the recent Water Supply Conference held at the Health Exhibi- tion, that it frequently happens there is abundance of good water t3 be found on the banks of a river that is no longer itself fit to sapply water for dietetic purposes. The total saving of the expense of filtration is also a very important item, which might, to some extent, recompense the London water companies for the expense of obtaining their supplies from sources that need no outlay on this head. The total cost of the tube-well, including cast-iron connec- tions to pump, was under £150, so that the town supplies on this system cannot be considered extravagant. Efficacy of Vaccination. — In his rei)ort of the working of the Homerton Small-pox Hospital, Dr. Gayton supplies us with the most recent, as well as most cogent, proof of the marvellous effi- cacy of vaccination as a prophylactic, and of the utter ignorance and crass stupidity of the peo]>le who are induced by paid agitators to lend their names and their uneducated minds to the contest against vaccination. From .lauuai'y 1 to March 7, 1883. during which time the small - pox patients were treated in the Fever Hospital, 02 cases were admitted ; of these, 43 were vaccinated, of whom 3 died, or at the rate of 70 per cent. ; 12 were doubtfully vaccinated, of whom 3 also died, or at the rate of 25 per cent. ; and 7 wore unvaccinated, of whom again 3 died, or at the rate of 4285 per cent. From March 7 to the end of the year, 325 patients were admitted — viz., 237 vaccinated, 30 doubtful, and 58 unvaccinated. Amongst these 17, 5, and 25 deaths respectively occurred, or at the respective rates of 702, lG-6, and 431. It seems, therefore, that the unhappy child who, by the influence of these foolish people, has been deprived of the benefit of vaccination, runs a risk of death from small-pox more than six times greater than the child who has undergone the harm- less operation necessary to preserve him against that disease. — The Medical Press. The AxTiquiTY of Merccry. — A recent writer in the North China Herald discusses the part played by mercury in the alchemy and materia medica of the Chinese. Cinnabar was known to them in the seventh century before the Christian era, and its occurrence on the surface of the earth was said to indicate gold beneath. Their views on the transformation of metals into ores and ores into metals by heat and other means took the form of a chemical doctrine about a century before Christ, and there is now no reason- able doubt that the Arabian Geber and others (as stated by Dr. Gladstone in his inaugural address to the Chemical Society) derived their ideas on the transmutation of metals into gold and the belief in immunity from death by the use of the philosopher's stone from China. Among all the metals with which the alchemist worked, mercury was pre-eminent, and this is stated to he really the philosopher's stone, of which Geber, Kalid, and others spoke in the times of the e;irly Caliphs. In China it was employed ex- cessively as a medicine. On nights when dew was falUng a suffi- cient amount was collected to mix with the powder of cinnabar, and this was taken habitually till it led to serious disturbance of the I o lily functions. In the ninth century an emperor, and in the tenth a prime minister, died from over doses of mercury. Chinese medical books say it takes two hundred years to produce cinnabar ; in three hundred years it becomes lead ; in two hundred years more it becomes silver, and then by obtaining a transforming sub- stance called " vapour of harmony " it becomes gold. This doctrine of the transformation of mercury into other metals is 2,000 years old in China. The Chinese hold that it not only prolongs life, but expels bad vapours, poison, and the gloom of an uneasy mind. " lict Knowledge grow from more to more." — Alfred Tennyson. Only a small proportion of Letters received can possibly be in- serted. Correspondents must not le offended, there/ore, should their letters not appear. All Editorial com.munications should he addressed to the Editor o» Knowledge; all Business communications to the Publishers, at the Office, 74, Great Queen-street, W.C. If this is not attended to delays arise fob which the Editor is not responsible. All Remittances, Cheques, and Post Office Orders should le made payable to Messrs. Wymau & Sons. The Editor is not responsible for the opinions of correspondents. No communications are answered by post, even though stamped AND DIKECTED ENVELOPE BE ENCLOSED. DAISIES. [1381] — I never had the slightest desire to exterminate daisies anywhere, and I have not the remotest idea how anybody seized with such an unnatural longing could proceed to gratify his or her wicked and destructive tastes. Perhaps the easiest way out of the difficulty would be for the " Disconsolate Female " to aim at acquiring a more reasonable liking for beautiful natm*al objects, and to correct the mistaken feeling which prefers an artificially smooth lawn to the graceful variety of self-sown herbage. Grant Allen. FALSE PERSPECTIVE. [1382] — It was a grave omission in the elementary works on Perspective not to have pointed out to T. E. (R.) Jones that the appearance of his "Plane of the Picture," and of the lines drawn 206 • KNOWLEDGE * [Sept. 5, 1884. upon it, are subject to the same laws of perspective as other objeots. For experiment, if he will arrange his row of equidistant and similar posts against a wall, which may be called the " Plane of the Picture," then trace the outline of eaeh on the wall with chalk, and remove the posts, there will remain a perspective representa- tion in harmony with the recognised rules ; and which yet, from its parts being at different distances from the spectator's " station- point," will show the same variations from crnde regularity as the original objects themselves. R. R. [1383] — By returning to the charge, T. E. (E.) Jones proves that this question is not yet satisfactorily disposed of. Does not the solution of the difficulty lie in the fact that a picture containing the element of perspective can only be seen properly from one point — which is technically known, I believe, as the '* point of station ? " Of course, the post / (in Mr. Jones's diagram) appears shorter than the post a, "because it is more distant" ; but its counterfeit presentment in the picture will also appear shorter for the same reason ; and, if properly drawn, exactly in the same proportion. The accompanying figure is intended to represent the posts in perspective. A a is at right angles to a/. The post /will then subtend a smaller angle at A than, for instance, the post c. of c' f is the ground-line of the posts as represented in a picture. A is still the position of the observer. It will then be seen that the post/' must be represented as exactly the same length as the post c' in order that their apparent sizes may correspond with those of / and c ; and the line y' x' must be drawn parallel to the line / a' in order to appear to converge as y x and / a appear to do. Of course, the post a must be supposed to be towards the centre of the picture ; but the field of view would never in practice be made to include so large a lateral angle as twice / A a. J. H. D. [1384] — In my letter (1359, August 15th) which appeared in Knowledge, I should have added, "If an observer standing at any point on the line AB parallel to af, proceed to move either to his right or left, still keeping on the parallel line, he will observe the effect described. Perhaps you will kindly allow me to point out (with a view to setting this question at rest) that if any one who doubts what I have said about the false perspective of rectangular solids, will place himself on the pavement in Gower-street, Lancaster-gate, Portland-place, or some similar street where the window and door lines, &c., are sufficiently even, and then walk along the curbstones until he can just catch sight of the houses in a side street opposite, he will have before him (supposing the streets to be at right angles) two sides of a parallelepiped, whose top and bottom edges trend away (or seem to trend away) to their respective vanishing point. R. (not "T. E.") Jones. " MOSES AND GEOLOGY." [1385] — I have only this morning been made aware of your article in Knowledge of Aug. 15, and must say that it has greatly surprised me. You call upon the members of my committee to furnish you with the names of the eminent scientists who have re-examined my work. I herewith send you them, and also enclose copies of their letters, the originals of which I shall be happy to show you at any time, and as you have attacked me so virulently and charged me with " orass ignorance," you will no doubt feel bound in honour to print these letters in full in your next edition. You state that my ridiculous blunders have been thoroughly exposed. Permit me to say that 1 have clearly proved in my replies to my antagonists that I have been on all occasions mis- represented and mi f quoted, and in most instances it was quite evident that my opponents had not even read my book. I would venture to think, from what you have written, that yon also have not done bo. Therefore I have desired Messrs. Cassell & Co. to send you a copy, and I must beg of you, as an act of justice to me and to the whole scientific world, that you will kindly read at least what I have written npon astronomy, after which I am sure you will be led to do your best to neutralise, as far as lies in your power, the article before me. Samcel Kinns. [I willingly print Dr. Kinns's letter, and those of his " eminent scientists." I read attentively through a former edition of his book, at the time of its appearance ; and will re-read the astro- nomical portion of the present edition with equal care. Mean- while, 1 note that in his printed testimonials his sole astronomical authority is Mr. W. T. Lynn (he seems, somehow, to have dropped Mr. Dunkin), a gentleman who has written a nice little book or two, and who occupied a subordinate position in the Royal Observa- tory for some years. Whether Mr. Lynn was responsible or not for the abnormal refraction business, I do not know. If so, singu- larly little deference need be paid to his opinion as to the logical value of the rest of the book. If, however, names are to be quoted (like texts) as decisive, it might be curious to speculate what Dr. Kinns thinks of the dicta of one of the very greatest astronomers now living. Sir George B. Airy (with whom Mr. Lynn could scarcely be compared, even by Dr. K. himself), as expressed in his " Notes on the Earlier Hebrew Scriptures," published by Longmans & Co. in 1876. One would also, by the way, like to know how far Dr Kinns's ideas are endorsed by such members of the staff of the British Museum as Sir Richard Owen, Drs. Giintherand Woodward, or Messrs. Carruthers, Butler, Etberidge, and Fletcher ? — Ed.] "the scientific accuracy of the bible. " In reference to the correspondence which appeared some few months ago as to Dr. Kinns' work, ' Moses and Geology,' we tmst we may count upon your giving insertion to the accompanying letters which have been called forth by the publication of the Seventh Edition, and bear important testimony to the accuracy of the statement of scientific and other facts in the work. We are very desirous that this act of justice should be done to an author who was subjected to the painful ordeal of so much unfair and injurious criticism, to which it was diflicult at the time to give a complete answer. We may add that the cordial reception of the lectures and addresses which Dr. Kinns has continued to give in various towns throughout England, bear witness to the esteem in which he is held. — On behalf of the Committee, we are. Sir, very truly yours, Shaftesbury ; R. N. Fowler, Lord Mayor ; Thomas Chambers, Recorder; R. Payne Smith, Dean of Canterbury; Henry White, Chaplain in Ordinary to the Queen." " British Museum, London, April 12th, 1884. " Dear Dr. Kinns, — Having examined the proof-sheets of the Seventh Edition of ' Moses and Geology,* now in the press, we consider the intrinsic merits of the work as very great, and that you have compiled the scientific, historical, and other facts with much care and accuracy. — Trusting that the book may continue to have the success which it deserves so well, we remain, yours most truly, S. Birch, LL.D., Theo. G. Pinches, Department of Oriental Antiquities, British Museum." " Royal Astronomical Society, Burlington House, Piccadilly, " May 12, 1884. " Dear Dr. Kinns, — At your request I have examined the astro- nomical portions of ' Moses and Geology ' for a Seventh Edition of the work. Great credit is, I think, due to yon for the care, dili- gence, and accuracy with which you have brought the scientific information up to date, as well as for the thorough revision which the book has now again undergone, rendering it still more worthy of the perusal of those who take an interest in its important sub- ject.— Yours sincerely, W. T. Lynn, B.A., P.R.A.S., late Super- intendent of the Calculating Department, Royal Observatory, Greenwich." "Athena3um Club, Pall Mall, S.W., 21st May, 1884. "My deae De. Kinns, — Having examined the proof-sheets of the geological portion of the Seventh Edition of your work. ' Moses and Geology,' I can testifv to your having exercised great care and pains in the arrangement and statement of the facts which they contain. — With kind regards and good wishes, believe me, dear Dr. Kinns, yours truly, H. W. Beisiow, F.K.S., Senior Director of H.M. Geological Survey." Sept. 5, 1884.] ♦ KNOWLEDGE ♦ 207 •• 1, Bedford-square, W.C, May 14, 1884. " My deak Dk. Kinns, — Having gone over the proof-sheets of the Seventh Edition of your book, ' Moses and Geology ' — or, rather, tliat portion of it devoted to the subject with which I am more familiar, the brain and its wondrous nervous connections — X may say jour descriptive matter is all that I can desire it to be, lending a charm and a value to the generally instructive character of your work. — Btlieve me to remain, yours very sincerely,— Jabez Hogg, M.K.C.S., Consulting Surgeon to the Royal Westminster Ophthalmic Hospital ; Fellow of the Medical Society, London, &c." " 97, Highbury New Park, May 15, 1884. " My dear Dr. Kixns, — I have at your request again examined all the Hebrew references in your valuable book, ' Moses and Geology,' and find them quite correct. I humbly believe that you have done immense good by proving the correctness and authenticity of the sacred records, and trusting you will meet with that snccess which your ardour and pious labour truly deserve, I am, my dear doctor, yours very sincerely, B. H. Ascheb, Rabbi of the United Synagogue." THE BEST FORM OF TRICYCLE. [1386] — During my tour along the south coast I saw Kxow- LtDGE, and noticed an article on tricycles. I ride a 36-in. " Merlin," and find it most suitable for my own use; but, having formerly ridden a Coventry " Compressus," I thought how near youi ideal machine it approaches. Having often ridden with the " Compressus," I know there are few machines that surpass it, only that it requires the rider to get a little forward to get additional weight on the driving-wheel going up hill ; and for those who care to have two speeds it can easily be applied. But it mainly dismisses the great point of Large v. Small Wheels, inasmuch as the large wheels carry the weight at level running, while the small one does the driving. I think if you would give the machine in question a little study and fair trial, you will be disposed to pronounce it second to none of chain-driven tricycles. Have vou tried the new " Merlin," and what is vour opinion of it y ' " H. A. MIXD AXD BRAIN. [1387] — If not encroaching too much on your valuable space, in reply to your editorial note on Huschke's dictum, that the vibra- t;ions of ether do not become colour until they are transmitted to the brain." I would rather put it thus: — "The phenomenon of colour is perceived " by the brain, through the eye and connecting nerves, and there transformed into the idea or thought expression — viz., colour. Nevertheless, the phenomenon of colour would still exist or be formed in fact, whether we could see it or not, or whether we called it colour or any other name. So I take Buschke to mean that the vibrations of stimuli, transmitted from within or without to the brain, are there transformed into thoughts or ideas by the self-acting molecules of the brain, whatever names we may give them. In short, like the vibrations of light are transformed — say by a prism into colours — so are the "vibrations of stimuli passing through our nerves and the brain transformed or modified into thoughts or ideas. F. W. H. [Just so. External stimuli may be " transformed into" thought by the molecular vibration of the brain ; but the contention of Biichner and Uuschke is that such vibrations are thought, which to ordinary minds is simply inconceivable. — Ep.] THE TERMS PRIMARIES" AND "SECONDARIES APPLIED TO COLOURS. AS [1388] — In a recent issue of Knowledge there was some refer- ence to what have been — under the nomenclature founded on erroneous conceptions regarding colour — termed primaries and secondaries^ or complementaries. Colours are still regarded, and spoken of, as if they had external existence. Persons, even those esteeming themselves " scientific," have constantly to be reminded that colours are but sensations, or appearances, excited in us by vibrations of different periodicities. Externally to sense the vibrations which excite all the different sensations of light (colour) in us are simply vibrations without luminosity or colour. " The light is within us." Now, we cannot consistently speak of primary and secondary sensations. The complementary colours, as they are <;alled, are not the effects of mixed sensations, but of the combined action of different wave lengths. It matters not whether vibrations be produced by the prismatic spectrum or by pigments, it is by means of vibrations alone that vision is effected. Let, for the sake of argument, the wave length of red be represented by 14, and blue liyO; then, if the two vibrations simultaneouslv aSect the same portion of the retina, we shall experience a third sensation of colour — the result of their combined action. Correctly speaking, it is not a colour that has a complementary, but a vibration. In my little work upon *' Light" I have expounded the principle of complementary vibrations — a principle which the late Mr. William Spottiswoode pronounced to be a sufficient and complete explanation of the phenomena. But to our point, the prism does not refract colours, but vibrations ; externally to the eye, there is, therefore, nothing but differentiated vibratory action, and by this medium all our varied sensations of sight are affected. On a future occasion, if permitted, I will advance reasons why it is also inconsistent that the terms primaries and secondaries should be applied to differentiated vibratory action. W. Cave TaoMAS. [Carrying out the principle enunciated in the above letter in its integrity, I have no business to talk about the object on which X am writing as " a table." What — if I rightly apprehend Mr. Cave Thomas — I ought to say is that I have certain sensations which I call brownness, blackness, hardness, resistances, extension, the scent of Morocco leather, &c., the sum of which make up my concept. I have myself said (in a note to letter 1362, p. 144) that the ethereal vibrations do not become colour untU they have been transmitted through the eye and optic nerve to the brain ; but, alike for the purposes of science and common sense, we treat colours as objective realities. — Ed.] LETTERS RECEIVED AND SHORT ANSWERS. The Honorary Secretary of the Cork Literary and Scientifr- Society is requested kindly to read the paragraph which concludes the first column on p. 62, and which has recently appeared on other occasions in this journal. — E. P. The whole thing is a matter of common sense. Mechanical pressure is admittedly a — or rather the — vera cau^a of such a movement, and Faraday's contention was that pressure was innocently exerted by the operators. His apparatus was so constructed that when pressure was applied the index moved, and when such pressure ceased to be applied it remained stationary. With the result you are familiar. Hermann, the conjuror, brings two live rabbits down into the stalls, and, holding them up by the ears in the very midst of his audience, strokes them into one. On the principle of Par^nmonia principionim , I find a ready explanation of this in the conjurer's proficiency in sleight-of-hand. Suppose, though, that some one chose to assert that the spirit of (say) Hermann's deceased wife's sister had removed the second rabbit, or incorporated it with the first, and that you or I were to suggest a plan (such as catching the performer by the wrist at a pai'ticular stage of the trick) by which the disappearance of rabbit No. 2 was prevented. Are we to be told that because the performer failed to unite the rabbits, our device " leaves the question just where it was ? Without the postulate of Parsimony it is migatory, and with that postulate it is superfluous ? " — Sidney Woodforde. For the dozenth time I have nothing to add to what I wrote on p. 58 of Vol. V. of Knowleikje. I really must beg you (and scores of correspondents who persist in sending me stamped and directed envelopes for private replies) to read, mark, learn, and inwardly digest the sentence in capital letters which concludes the heading of the correspondence columns. — L. G. R. See answer to E. P. above. — C. H. Johns. You will find the Unes you quote in Wordsworth's "Tintern Abbey." — The Secretary of the Bow AND BROMtEY INSTITUTE is requested to be good enough to read the first reply above. — W. W. S. The " Monthly Notices " of the Royal Astronomical Society are published by Williams & Norgate, London. 1 do not know the price to the public. All information with regard to the publications of the Liverpool Astro- nomical Society may be obtained on application to W. H . Da vies, Esq., F.R.A.S., 55, Great Newton-street, Liverpool. — Anontmocs (Sunderland). Our advertising columns are open to you. — John Hampden. Some one has been hoaxing you. Does not your own common sense suflSce to show you that, were the earth flat, no intermediate stations whatever would be needed between Wimble- don and Portsmouth ? — SiGSLA. It appears as though you were incapable of realising the meaning of Infinity. How can yon pos- sibly add — or subtract — from Infinity, or one infinite quantity from another ; or conceive a circle vrith an " infinite " radius ? As for your notions of equating two expressions each of them = nothing; a very old mathematical joke will serve to illustrate where that will land you. Let a = T> : then a'' = ab and a'- — b- = ah — h- : or {a + i) (a — b) = {a — h)b or a + b = b : i.e. 2a = a or 2 = 11 — C. Frederick Wilkinson. — Thanks for your interesting extract, which is marked for insertion. — Chas. Aldridge. The Editor is nearer to you than you imagine. Tonr letter will be forwarded. — Erimus. Does " every ninth wave rush in .vith greater volume and force than any of the others ? " — Dr J. Murray Mooee. How could a star which appeared in Virgo, by any conceivable possibility, reappear in Cassiopeia ? A new star did blaze out in Cassiopeia from Nov., 1572, to March, 208 • KNOWLEDGE • [Sept. 5, 1884. 1574, and Tycho Brahe determined its place with some accuracy. There is a minute telescopic star (No. 129 of d'Arrest's Catalogue) within 1' of this position, which was discovered to be slightly variable by Hind and Plummer in 1873. There is no record of the appearance of any new star in Virgo, B.C. 4 ; but that very doubt- ful authority, the Bohemian astronomer, Cyprianns Leovitius, asserts that he found, in a manuscript, a record of the appearance between Cepheus and Cassiopeia in 945, and again, iu the same neighbour- hood, in 1264, of a new star, which it has been thought may have been Tycho's. Assuming such conjecture to have been correct, the star should have reappeared in 1880. "Jlercator" is wrong, im limine, in his dates, and quite obviously ignorant of the veiy rudi- ments of astronomy, or he could never have imagined two stars, separated by an arc of more than 120' in the heavens, to be one and the same object. (Bur Ct)t6s! Column. By Mephisto. P to Q6. Thus 33. " Deak Sir, — I have been much interested in the game published in this week's Knowledge. But, on going over the moves sug- gested as a probable continuation, I cannot see that White can really force the game. I enclose a rough analysis to show yon where my difBculty lies. It seems to me that 33. Ktto K7 (ch) is a complete answer to 33. P to Q6. After 32. Kt^x Kt, Black has a Book to the good, and therefore can afford a considerable sacrifice to beat off White's present attack. I tried 33. K x P (ch;, but the Whit« King can escape. I cannot see any escape after 33. KttoK7 (ch). " I think White's best play is to get his B to Q3 before playing BtoRTJch) gj BtoQ3 (ch) 35 pj^Qg. gut KtoRsq. KtoKtsq. even then Black may follow with 35. KttoK7 (ch), and I don't think White can dare capture the Knight. Then, again, if Black can get one more check and then attack the White Queen with Kt, he can safely challenge the exchange, or can sacrifice his Knight to give his Queen time to take the QP and retire to defend KBP. " Altogether, the position is such a good one, that I think yon would interest other readers as well as myself if you would analyse it for us a little further. " W." We agree with our correspondent that the position is an interesting one. We ought to have been a little more remark about 32. Kt x Kt. It is all-im- portant in such critical posi- explicit in onr Position after White's 32nd move. Buck. 1 r 1 1 # f ■ ^ 1 2 * i i; & .. ■ 'M i 37 ■Whits R X Kt(a) 38. K to R sq. tions to find the correct way of playing, as without it a sure game may be lost. If in this position 32. Kt x Kt then we must first avoid losing the important B by a ch with Kt on Kt6 ; we, there- , „„ B to R7 (ch) „■ I ore play 33. r— i — - . The ^ ■' K to R sq. ]i being now very well posted, we proceed to 34. P to Q6, which valiant P the Q cannot take on account of a mate in three. But if 34. Kt to K7 (ch) K to R sq. gg ^ ^^ JJ2. To KttoKtG(ch) avoid the threatened three Black has better than 36, mate m nothing Kt to B8 (ch) - , , (best). QxP(ch) QtoB2 ^ ' We did not play R to B4 as Black could have replied with Q x B, followed by KxB remaining with two R's against the Q and a bettor game. Now White cannot do better than play B to Q3 (ch) ,„ Q to R7 (ch) ^^ Q to R8 (ch) ■ K to Kt sq. ■ K to B sq. " K to K2 4&. Q"^^"''^ 43. Qx Rand White wins. K to B sq. (a) This leads to a win if correctly followed up. A more decisive yet simpler move is 37. K to E3, which wins at once, as Black cannot check with the (Q) on account of B coming on B5 ^vith a check. If QxP 38. B to KtG (ch), K to Kt sq. 39. Q to R7 (ch), K to B sq. 40. QxP mate, or if Q to R2, the Q mates in two moves on R8. PROBLEM No. 126. By I. G. Black. m WMn^wm ¥M TVhitb. White to play and mate in two moves. SOLUTIONS. Peoblems BY T. G.p. 168. 1. 2. 3. B to QB3 K to B8 (ch) B toB7 II. 1. Q toKKt2 2. QxQ mate 1. 2. 3. Q to Kt7 PxQ P to Kt8 (ch) (Q) 1. QxQ 2. K to R sq. mate. ANSWERS TO CORRESPONDENTS. »*, Flease address Chess Editor. Jas. G. Reeve. — See above letter. Solution incorrect as 1. K to R sq. Correct solutions received Problem No. 124. — Fred Kingley, J. K. Milne, H. A. N., M. T. Horton, A. W. Overton. CONTKKTS OP Xo. 148. Xeit Year's Exhibition. By In- Tentor 169 Tbe Entomolo^ of a Pond. IIUkk.) BtE. A. Buller 170 The' Physics of the Earth's Cmst. Bt R. A. Proctor 171 The" Chemistry of Cookery. XLI. Authorities on Tea and Coffee. By W. Matlieu Williams 172 The" Electro-Magnet. (Illut.) By W. Slingo 173 The Earth's Shape and Motions. III. The Annual Motion of the Sun and Stars. By E. A. Proctor 175 Pie* Our Supply of Coal 176 A Practical Method of EstimatiDg Distances. (Uluf.) 177 Pleasant Hours with the Micro- scope. (lUvn.) By H. J. Slack . 17S> Photo^aphr for Amateurs 190 Editorial Gossip 182 Face of the Sky. By F.K.A.S 182 Reviews 183 Miscellanea 184 Correspondence : Sunflowers — Is Tea Injurious? — Small-Poi and Vaccination — August Meteors, &c. 185 Our Chess Column 188 N^OTICES. Fart XXXIV. (Aagnst, 1884), now ready, price Is. 3d., post-free, 1b. 6d. Volume v., comprising the nunobers published from January to Jane, 1E8-J, now ready, price 99., including parcels postage, 99. 6d. Binding Cases for all the Volumes pubhihed are to be had, price 28. each, includJDff parcel postage, 23. 3d. Subscribers' numbers bound (including title, index, and case) for 3s, each Volume ; including return journey per parcels post, 3s. 9d. Kemittances should in every case accompany parcels for binding. TEEMS OF SUBSCRIPTION. The terms of Annual Subscription to the weekly numbers of KxowxinoE are as follows:— »• "J- To any address in the United Kingdom 16 2 To the Continent, Australia, New Zealand, South Africa, & Canada 17 4 To the United States of America $1.25 or 17 4 To the East Indies, China, &c. (nu Brindisi) 19 6 All subscriptions are payable in advance. OFFICE : 74-7G, GREAT QUEEN STREET, LONDON, W.C. Sept. 12, 1884.] ♦ KNOWLEDGE ♦ 209 "■^ AN ILLUSTRATED AGAZINEofSCIENCE lYWORDED-EXACTUDESCRlBMii LONDON: FEJDAT, SEPT. 12, 1884. Contents op No. 150. Dickens's Story Left Half Told. By Thomas Foster 209 The Entomology of a Pond, {lllui,) By E. A. Butler 210 The Chemistry of Cookery. XLII. Stimulants and Condiments. By W. Matlieu Williams 212 Ships' Liuhts 213 The Earth's Shape and Motions. {nius.) By Richard A. Proctor... 214 British Seaside Kesorts. IV. By Percy Russell 215 Notes on Coal. By Richard A. Proctor 216 Novel Tricycles. {Ilhtt.) By John Browning 217 The International Health Eihibi- Hon. XT. (.Ilbia.) 218 Other Worlds than Ours. By M. de Fontenelle. With Notes by Richard A. Proctor 220 Editorial Gossip 221 Renews 222 Face of the Sky. By F.R.A.S 222 Correspondence : — Shooting Stars and Meteorites, &c 22-i Our Whist Column 227 Our Chssa Colimm 228 DICKENS'S STORY LEFT HALF TOLD. k QUASI SCIENTTFIC IXQCIRY INTO THE MYSTERY OF EDWIN DEOOD. Bt Thomas Foster. IN reply to H. E., I note that the article on " The Mystery of Edwin Drood," though republished in the Kno^\t.edge LibrjVry (" Leisure Readings ") did not origi- nally appear in Knowledge but in the Belgraria Magazine, about five years since : I do not recollect the exact date. In " Leisure Readings " the article is longer by about one- fourth than as it first appeared.* Let me further explain that in speaking of the ai'ticle in the CornhiU JIagazine as " rather feeble," I was thinking only of the way in which the writer presents as a mystery' which Dickens had been careful to conceal, precisely that which Dickens had been most careful to suggest. In this sense, also, H. E. appeared to me decidedly to place himself in the rank of those " commonplace readers " whose ways Dickens understood so well. Dickens himself, though he may have led Mr. Fildes to think that only " a keen reader " could " ever find out who and what was Mr. Datchery," had as certainly conveyed to Miss Hogarth his fear lest keen readers would find out the real meaning of what he called " the Datchery assumption," and that with that they would recognise the course along which the story was to have advanced towards its end. And Dickens himself, while he knew how much or how little he had consciously left open to the keener among his readers, did not know how much he unconsciously left open to those whose ears could take in the music of his prose poetry. I venture to say that to any one possessing this power the general purport of the plot of all Dickens's later novels was made clearer by unconscious suggestions than by any of those indications which Dickens consciously left open to his keener followers. Before entering on the consideration of what appears to me most obviously to have been Dickens's purpose and meaning in his last story, let me invite H. E.'s attention to * It will be found that the greater part of the reasoning pre- sented in this and the following papers on the subject of Dickens's last story is independent of the evidence — itself I think convincing — advanced in the above-mentioned article. the significance of the passage which he quotes from the article " How Edwin Drood was illustrated," in the Century Magazine for February, 1884. It disposes in the first place, utterly, of H. E.'s own views, if ho admits that the central crime was " never intended by the author to be a mystery," — which is precisely my contention. And certainly if the true interpretation of Mr. Datchery is that " he is some detective," then no great keenness would be required on the reader's part, for Dickens tells us as plainly as possible that Datchery is some detective, though assuredly not an ordi- nary detective, as H. E. opines. If the character of Datchery is " an assumption," and Dickens spoke of it as such to Mr. Forster and to Miss Hogarth, then apart from all other evidence Datchery cannot be a professional detective ; and if the " finding out who and what Mr. Datchery was " be important to the elucidation of the mystery, Datchery cannot be Buzzard, the only other character in the story who could possibly have assumed the part, except Edwin Drood himself. H. E., I see, rejects as I do the idea that Datchery is Buzzard ; and I may remark on this point that any one who could suppose for a moment that Buzzard is Datchery would .show such an utter want of appreciation of Dickens's manner and methods, that it would be idle to deal with him by reasoning. Datchery and Buzzard are made by Dickens to be altogether difl^erent men : Datchery and Drood are made by him to be as unlike as possible in all outside features ; and as the great trial through which he had passed would necessarily have changed Drood much in character, Dickens has endeavoured to make Datchery and Drood unlike in manner ; but they are as obviously the same men, as Hamlet after he has seen his father's ghost is the same as the Hamlet of earlier scenes. There is a quaint humour in Datchery which is seen in Drood and Drood only of all the characters of the story. There is a kindness to old folk and to childreu, and a power of understanding their ways, which is shown only in Drood (and is in words attributed to him, besides being indicated in action) ; and lastly there is a wistfulness associated with Datchery's humorous manner which Drood alone of all the characters in the opening part of the story had shown. So that Datchery being by Dickens's own statement an " assumption," could be no other than Drood, even if Dickens had said in so many words that Drood was dead (which in his earlier manner, he would not have hesitated to do, explaining afterwards how that meant only that he was dead in men's thoughts). But it will be noticed that Drood is never once spoken of as dead, either by the author, or by Grewgious, or by Rosa. We have passages suggestive of death, both before and after the attempted murder. We are told that " he never called Rosa Pussy more, never again." Again, after we are told he purposed never to return to Cloisterham, come the words, "Poor youth! poor youth! "and so forth, just as Dickens says that " no such being as Richard Doubledick remained in the world of consciousness," that Yendale's " heart had ceased to beat," and so forth. He does aU he can to suggest that the murder has been successful, and lets us know, in fact, that Jasper is full sure it has been suc- cessful (and surely .Jasper ought to know) ; but he had been just as careful to impress on his readei"s the belief that Jonas Chuzzlewit had been successful in murdering Anthony Chuzzlewit, and he lets us know that Jonas was full sure he had been successful : yet neither in one case nor in the other had the murderer's plot succeeded, as he imagined. With regard to the terrible grief which H. E. considers that Drood unnecessarily caused Rosa, he wiU find if he reads the story attentively the most remarkable avoidance of any words suggestive that Rosa suflered such grief as she 210 • KNOWLEDGE [Sept. 12, 1884. would certainly have felt had Drood been really dead. There is not a word implying that she thinks Drood is dead. And this is so much the stranger that Dickens draws so close, again and again, to occasions for speaking of Rosa's sorrow for Drood. She speaks of Drood to Jasper in the past tense ; but that of course she would be bound to do. We hear of her sorrow for Drood in connection with her growing love for Tartar, — and this would be natural whether she thought Drood dead or alive, (but much more natural if, supposing Drood alive, she was sad at the thought that he might still love her though their engage- ment had been broken off.) — T. F. But now for what seems to me most obviously to be the course of the story up to the time when its author's pen fell from his hand, and (in general outline only, of course) its intended course thereafter. Before the attempted murder, the points to be specially noted are these : — First, the way in which Jasper has arranged for the dis- posal of Drood's body after the murder. We see him arranging a meeting with .Japsea and Durdles, in such a way that all he may do in the way of using Durdles' knowledge may seem to have been suggested by Japsea. (The three wineglasses, and what is said of them, should be specially noticed.) At this meeting again Jasper cleverly uses his musical knowledge to obtain a means of identify- ing the various keys carried by Durdles, — a means which neither Durdles nor Japsea would suspect, but Durdles notes (without at the time understanding) what he is doing. He repeats his tone-test soon after, in company with Durdles only. Later, in the " surely unaccountable expedition," we see how Jasper applies the knowledge thus obtained. He drugs the wine which he knows Durdles will drain to the last drop, and when Durdles sinks to sleep, he takes the keys, clinks them again, and in the long hours at his disposal (for the " murmur of the tide of life " is still heard when they enter the Precincts, and it is two o'clock when Durdles at length wakes) he takes impressions of the keys, collects quicklime within the Japsea tomb, and prepares generally for the crime he has planned. That he has been outside is shown, after the author's manner, by his wrath with the Deputy (wrath so fierce that " he seemed like a devil ") because " he followed us here to-night " and " has been prowling near us ever since, " which would not have mattered had Jasper remained inside the crypt while Durdles slept. Secondly, we are to note the sadness felt by Drood after his parting with Rosa. Much of the significance of Datchery's conduct later is lost if we overlook this feeling on Drood's part. That it had an important beaiing on the later progress of the story, and was meant to be most care- fully noted by the more thoughtful and understanding readers, is obvious to all who know Dickens's manner. Follow what Dickens says here, noting that his first words about Drood in the chapter most significantly headed When will these three meet again? (showing clearly that Neville, Drood, and Jasper tvere to meet again) : " Edwin Drood passed a solitary day. Something of deeper moment than he had thought, has gone out of his life ; and in the silence of his own chamber he wept for it last night . . . the pretty little affectionate creature, so much firmer and wiser than he had s\ipposed occupies the stronghold of his mind. It is with some misgiving of his own unworthiness that he thinks of her, and of what they might have been to one another, if he had been more in earnest some time ago ; if he had set a higher value on her ; if instead of accepting his lot in life as an in- heritance of course, he had studied the right way to its appreciation and enhancement." .... Then later, — " He strolls about and about, to i)a8S the time It some- how happens that Cloisterham seems reproachful to him to-day ; has fault to find with him, as if he had not used it well ; but is far more pensive with him than angry. His wonted carelessness is replaced by a wii-tful looking at and dwelling upon, all the old landmarks. He will soon be far away, and may never see them again, he thinks. Poor youth ! Poor youth ! " — Later yet, — " Always kindly, but moved to be unusually kind this evening, and having bestowed kind words on most of the children and aged people he has met, he bends down " to the old opium eater, and speaks to her. The conversation should be most carefully followed and compared with the later conversation between the same old woman and Datchery. I could as readily doubt that the same person speaks to her on both these occasions, as I could doubt whether the IMoonlight Sonata and the Sonata Pathetique came from the same composer. Apart, how- ever, from the words and manner of Drood and Datchery, consider what is said about them. Compare the words quoted above with these : — " Mr. Datchery pauses as if he were falling into a brown study and couldn't bear to part with" — something — "but he bestows" his gift on the old woman (who is then so dull as to imagine that it is of this he is thinking'!), "as if he were abstracting his mind from the sacrifice John Jasper's lamp is kindled, and his lighthouse is shining when Mr. Datchery returns alone towards it. As mariners, on a dangerous voyage, approaching an iron-bound coast, may look along the beams of the warning light to the haven lying beyond it that may never be reached, so Mr. Datchery's wistful gaze is directed to this beacon, and beyond." Compare the two following few words alone, if the music of each full passage is not easily caught : — Of Drood, we read, — " His wonted carelessness is replaced hy a vmtful looking at and dwelling upon all the old land- mai-ks : he. irill soon be Jar away, and inay never see tftem again, he thinks." Of Datchery, — "As mariners look along the beams of the warning light to the haven lyinr/ beyond it that may never br reached, his wistful gaze is directed to this beacon and beyond." That this resemblance, or rather this oneness of tone should have escaped notice I can understand ; but that any one whose attention has once been directed to it can fail to see that Drood and Datchery are one, seems to me scarce conceivable. I certainly cannot imagine how any one could suppose the later words applied to a detective employed by Grewgious, or to the stupid and selfish Buzzard. (To be continued.) THE ENTOMOLOGY OF A POND. By E. a. Butler. THE BOTTOM (continued). THE water scorpions are aquatic during the whole of their lives, but the insects we have now to consider pass only their earlier stages in the water, being inhabi- tants of the air when they have reached the perfect, or imago, form ; indeed, the bottom of the pond is, as a rule, much more the theatre of larval than of imaginal life. As we have before intimated, beetles and bugs are almost the only kinds of insects that are strictly aquatic when adult. We will first take the larva> of the dragon-flies. The perfect insects, which are sometimes also called horse- Sept. 12, 1884.] ♦ KNOWLEDGE ♦ 211 stingers, and in Scotland go by the name of " devil's darning-needles," and in America by that of " mosquito hawks," will detain us later on, when we speak of the fauna of the atrial regions just above the pond. Suffice it here to say, that they have four large glassy-looking wings, reticulated with a multitude of nervures, and usually a long, slender body, which has suggested to our Highland brethren the diabolical connection above mentioned. For brilliancy of coloration they easily take a prominent position in the insect world ; but their beauty pertains wholly to the adult form. In their aquatic stages they are the dingiest of the dingy, and in many cases are hideously ugly. When you have brought yourself to perform the disagreeable task of hauling out of a dirty pond a mass of slimy weeds and fetid mud, and have deposited it on the bank, you see the mass here and there heaving with the struggles of these ugly brutes as they gradually work their way into daylight and drag their grimy bodies out of the tenacious and unsavoury mess. What a contrast between this sordid life and the gay and brilliant existence of the shiny- winged adult, as it dashes about, glistening in the sunbeams ! There are two principal types of these larvre ; one a broad, thickset, clumsy creature, which yields the larger and stouter - bodied dragon-flies, the other slender and carrying some leaf-like ap- pendages at the tail, the immature condition of the most slender and graceful members of the group. Taking first the former of these (Fig. 1), we see a creature with six Fig. 1. — Larva of Dragon Fly. straggling legs, which, sprawling out at the sides, would, were it not for their number, be strongly suggestive of affinities to the spider class. The head, when viewed from above, is surprisingly like that of a kitten, the prominent ears of the latter being represented by the equally prominent eyes of the insect ; the two short antennse, too, are suggestive of the kitten's whiskers. Then comes the thorax, with curious ridges Like rough bark, and carrying the six sprawling legs and the rudimentary wings, and then the abdomen, broadest a little behind the middle, and exhibiting, especially in its hinder part, periodi- cal contractions and dilatations, the length being lessened at the expense of the breadth. This motion, as might be expected, is a respiratory one. The breathing is performed in a manner as wonderful as it is unique. It is most marvellous what a variety of contrivances there are to enable aquatic insects to perform this important function ; we have already referred to the diving-bell arrangement of the water-beetles, the anal spiracle of some of their larva?, and the lateral leaf-like appendages of others, the long tail- filaments of the water scorpions, and the feathery stars and tubes of the gnat larva^ and pupa?, and now we come to an arrangement totally distinct from all of these. At the extremity of the body there are some stout, spiue-lLke processes, surrounding the terminal orifice of the diges- tive tube, which is guarded by a valvular apparatus. By mxiscular effort these spines, which are movable at their base, can be opened out like the parts of a wire egg- whisk, the capacity of the abdomen being at the same time increased ; the valves are thus opened, and water rushes in and fills the terminal part of the intestinal canal, and after remaining there a short time, is forcibly ejected by a reversal of these operations. The lining of the last part of the intestine is produced into six double series of folds, whereby its surface is enormously increased. In the interior of these thin folds, great numbers of minute tracheal tubes are distributed. The water, of course, as usual, contains air dissolved in it ; and, as it passes over these tracheal tubes, the fresh air with which it is charged can be exchanged for the contaminated supply contained in the tubes, by simple transfusion of the gases through the thin walls of these. As soon as this has been effected, the now useless water is got rid of in the manner above described, but its expulsion frequently serves the additional purpose of effecting locomotion. Wlien the insect is calm and undisturbed, the water is passed out gently, but should it be disturbed or alarmed, a forcible ejection of the liquid follows, and just as a rocket mounts in the air while the gases into which its contents are being transformed by the process of combustion, rush out in the other direction, so the larval dragon-fly is shot swiftly forward as the jet passes out from behind. The jet can be readily observed : if there are particles of matter in suspension in the water, their movements as they are carried slong with the stream make the current perceptible ; or if the creatures are in a shallow vessel with only just enough water to cover them, the sur- face will be seen to be violently disturbed at every expira- tion. The force with which the water can be projected is quite surprising ; the most astonishing record comes from over the sea. A lady states in the American Naturalist that a larva of a large species, when disturbed, sent out a fine stream of water to the distance of from two to three feet, and continued doing so indefinitely ! These curious beings then progress by a series of jerks or leaps, though, of course, they can crawl as well. Some kinds while jerking themselves forward, assist their efforts by a sharp backward stroke of the legs (though these are not modified for swimming purposes), and finish the stroke by bringing the legs close alongside the body, an action by no means inelegant. The more slender kinds have an elongated body, which they can move pretty vigorously from side to side as a fish does its tail. They have also three external leaf-like appendages at the tail, which are thin, and are each sup- plied with a tracheal tube and its branches, the exchange of gases taking place here externally in the same way as in the others internally. These caudal leaves, too, are used to assist locomotion. But we have yet to consider one of the most remarkable peculiarities of these creatures. If we take a front view of the head, we see the lower part of the face rounded and smooth, with a vertical zigzag line down the centre, and showing no traces of great jaws such as one would expect in so voracious an insect. This is simply because they are concealed by a very curious modification of that part of the mouth which, in insects generally, is called the labium, or lower lip. To examine this structure it is best to take a freshly-killed specimen ; this is easily obtained by plunging the creature into boUiny water, which produces instanta- neous death. By aid of a pin or needle we can now easily open out the " mask," as it is called (Fig. 2), and when fully extended, we see that it looks something like a broad-handled ladle, attached by the handle underneath the head. It consists of several joints, the basal one of which is attached to the lower part of the head, 212 ♦ kno\a;^ledge ♦ [Sept. 12, 1884. or, as we might say, under the chin. Succeeding this is another piece, at the outer angles of which are attached two curved triangular jaw-like pieces articu- lated to it l)y one of their angles, and capable of folding inwards till their saw-like edges exactly meet, when the front part of the apparatus forms the bowl of the ladle. When closed, the basal joint is bent backwards, showing as a bluntly-i^ointed projection, reaching to the base of the ^ZD=^ Fig. 2. — Mask of Dragon Fly. a. Side View. I. Viewed from Above, c. The Same, with Jaws Open. second pair of legs ; the next piece is folded back upon this, and the bowl-like part is thus brought close up to the face, which fits into the hollow. When the mask is ex- tended, the real jaws are seen beneath in the usual position. The mask is used somewhat like the raptorial legs of the water-scorpions — viz., to seize a passing insect at a little distance. To accomplish this, it is very rapidly unfolded, darted out with unerring aim, and brought back again into position, thus holding the prey close up to the true jaws. Dragon-flies do not alter much during their earlier stages. The traces of wings soon appear, even after the first moult or two. When a moult is about to take place, the creature fixes its claws into some support to obtain leverage for its coming struggle, and then, by strong mus- cular efibrt, the back of the thorax is split, and the insect crawls out of its case. The cast skins may frequently be seen floating about in ponds. The insects are very voracious, and when other food fails, will not scruple to adopt cannibalism. (To he continu,ed.) THE CHEMISTRY OF COOKERY. By W. Mattieu Williams. XLII.— STIMULANTS AND CONDIMENTS. BEFORE proceeding further, I must fulfil the promise made in No. 39 to report the results of my repetition of the Indian process of preparing samp. I soaked some ordinary Indian corn in a solution of carbonate of potash, exceeding the ten or twelve hours specified by Count Eumford. The external coat was not removed even after two days' soaking, but the corns were much swollen and softened. I suspect that this difference is due to the con- dition of the corn which is imported here. It is fully ripened, dried, and hardened, while that used by the Indians was probably fresh gathered, barely ripe, and much softer. Mr. Gaubert (No. 1,373, page 185) asks me whether I think that tea taken in moderation (say two cups in the evening) does any mischief. If he carefully reads No. 40 he will find the answer already given before his question was asked. He offers to relinquish the habit, in spite of the pang, " on the advice of so eminent an authority " as myself. I hope that he will not be so weak as to accept my authority or any other on a question which can easily be answered by common-sense and simple direct experiment. There are cases in which we are compelled to lean on authority, but this is not one of them, and he will see, by re-perusing what I have written on the subject, that I have repudiated mere authority, and appealed to facts that are open to all. I will reply further to Mr. Gaubert, as in doing so I shall be also replying to a multitude of others, his CMe being typical. Let any of these repeat the experiment that I have made. After establishing the habit of taking tea at a particular hour, suddenly relinquish it altogether. The result will be more or less unpleasant, in some cases seriously so. My symptoms were a dull headache and intellectual sluggishness during the remainder of the day — and if compelled to do any brain-work, such as lecturing or writing, I did it badly. This, as I have already said, is the diseased condition induced by the habit. These symptoms vary with the amount of the customary indulgence and the temperament of the individual. A rough, lumbering, insensible navvy may drink a quart or two of tea, or a few gallons of beer, or several quarterns of gin, with but small results of any kind. I know an omnibus-driver who makes seven double journeys daily, and his " reglars " are half-a-quartern of gin at each terminus — i.e., If pints daily, exclusive of extras. This would render most men helplessly drunk, but he is never drunk, and drives well and safely. Assuming, then, that the experimenter has taken suffi- cient daily tea to have a sensible effect, he will suffer on leaving it off. Let him persevere in the discontinuance, in spite of brain languor and dull headache. He will find that day by day the languor will diminish, and in the course of time (about a fortnight or three weeks in any case) he will be weaned. He will retain from morning to night the full, free, and steady use of all his faculties ; will get through his day's work without any fluctuation of working ability (provided, of course, no other stimulant is used). Instead of his best faculties being dependent on a drug for their awakening, he will be in the condition of true man- hood— i.e., able to do his best in any direction of effort, simply in reply to moral demand ; able to do whatever is right and advantageous, simply because his reason shows that it is so. The sense of duty is to such a free man the only stimulus demanded for calling forth his uttermost energies. If he again returns to his habitual tea, he will again be reduced to more or less of dependence upon it. This con- dition of dependence is a state of disease precisely analogous to that which is induced by opium and other drugs that operate by temporary abnormal cerebral exalta- tion. The pleasurable sensations enjoyed by the opium- eater or smoker or morphia injector are more intense than those of the tea-drinker. Mr. Gaubert tells us that he enjoys his cup " immensely." The gin-drinker enjoys his half-quartern " immensely," as anybody may see by " standing treat " and watching the result. The victim of opium has enjoyment still more immense, and in every case the magnitude of the mischief is measurable by the immensity of the enjoyment. Again I say that I am not denouncing the proper use of any of these things. There are occasions when artificial stimulants or sedatives cautiously used are most desirable. ]My condemnation is applied to their habitual use, and the physical and moral degradation involved in the slavish dependence upon any sort of drug, especially when the drug operates most powerfully on the brain. To the brain- worker tea is worse than alcohol, because it exaggerates his special liability to overstrain. I can detect by physio- gnomical indications the habitually-excessive tea-drinker as readily as I can detect the physiognomy of the opium- victim, as may anybody else who chooses to make careful observations. Sept. 12, 1884.] ♦ KNOWLEDGE ♦ 213 I must not leave this subject -witliout a word or two in reference to a widely prevailing and very mischievous fallacy. Many argue and actually believe that because a given drug has great efficiency in curing disease, it must do good if taken under ordinary conditions of health. No high authorities are demanded for the refutation of this. A little common sense properly used is quite sufficient. It is evident that a medicine, properly so-called, is something which is capable of producing a disturbing or alterative effijct on the body generally or some particular organ. The skill of the physician consists in so applying this disturbing agency as to produce an alteration of the state of disease, a direct conversion of the state of disease to a state of health, if possible (which is rarely the case), or more usually the conversion of one state of disease into another of milder character. But, when we are in a state of sound health, any such disturbance or alteration must be a change for the worse, must throw us out of health to an extent proportionate to the potency of the drug. I might illustrate this by a multitude of familiar ex- amples, but they would carry me too far away from my proper subject. There is, however, one class of such remedies which are directly connected with the chemistry of cookery. I refer to the condiments that act as " tonics," excluding common salt, which is an article of food, though often mis- called a condiment. It is food simply because it supplies the blood with one of its normal and necessary consti- tuents, chloride of sodium, without which we cannot live. A certain quantity of it exists in most of our ordinary food, but not always sufficient. Cayenne pepper may be selected as a typical example of a condiment properly so called. Mustard is a food and condiment combined ; this is the case with some others. Curry powders are mixtures of very potent condiments with more or less of farinaceous materials, and sulphur compounds, which, like the oil of mustard, of onions, garlic, itc, may have a certain amount of nutritive value. The mere condiment is a stimulating drug that does its work directly upon the inner lining of the stomach, by exciting it to increased and abnormal activity. A dyspep- tic may obtain immediate relief by using cayenne pepper. Among the advertised patent medicines is a pill bearing the very ominous name of its compounder, the active con- stituent of which is cayenne. Great relief and temporary comfort is commonly obtained by using it as a " dinner pill." If thus used only as a temporary remedy for an acute and temporary, or exceptional, attack of indigestion all is well, but the cayenne, whether taken in pills or dusted over the food or stewed with it in curries or any other- wise, is one of the most cruel of slow poisons when taken liahituallij. Thousands of poor wretches are crawling miserably towards their graves, the victims of the multi- tude of maladies of both mind and body that are connected with chronic, incurable dyspepsia, all brought about by the habitual use of cayenne and its condimental cousins. The usual history of these victims is that they began by over-feeding, took the condiment to force the stomach to do more than its healthful amount of work, using but a little at first. Then the stomach became tolerant of this little, and demanded more ; then more, and more, and more, until at last inHammation, ulceration, torpidity, and finally the death of the digestive powers, accompanied with all that long train of miseries to which I have referred. India is their special fatherland. Englishmen, accustomed to an active life at home, and a climate demanding much food fuel for the maintenance of animal heat, go to India, crammed, may be, with Latin, but ignorant of the laws of health ; cheap servants promote indolence, tropical heat diminishes respiratory oxidation, and the appetite naturally fails. Instead of understanding this failure as an admoni- tion to take smaller quantities of food, or food of less nutritive value, they regard it as a symptom of ill-health, and take curries, bitter ale, and other tonics or appetising condiments, which, however mischievous in England,^are far more so there. I know several men who have lived rationally in India, and they all agree that the climate is especially favourable to longevity, provided bitter beer, and all other alcoholic drinks, all peppery condiments, and flesh foods are avoided. The most remarkable example of vigorous old age I have ever met was a retired colonel eighty-two years of age, who had risen from the ranks, and had been fifty-five years in India without furlough ; drank no alcohol during that period ; was a vegetarian in India, though not so in his native land. I guessed his age to be somewhere about sixty. He was a Scotchman, and an ardent student of the works of both George and Dr. Andrew Combe. While still seasonable I add by way of postscript a receipt for a dish lately invented by my wife. It is vege- table marrow an gratin, prepared :by simply boiling the vegetable as usual, sKcing it, placing the slices in a dish, covering them with grated cheese, and then browning slightly in an oven or before the fire, as in preparing the well-known " cauliflower ait yratin." I have modified this (with improvement, I believe) by mashing the boiled marrow and stin-ing the grated cheese into the midst of it whilst as hot as possible ; or, better still, by adding a little milk, a pinch of bicarbonate of potash, mixing with the cheese, and then returning this puree to the saucepan, heating and stirring it there for a few minutes to effect the complete solution of the cheese. This dish is not so pretty as that au gratin browned in orthodox fashion, but is more digestible. SHIPS' LIGHTS. THE following extract from the New Regidations for Preventing Collisions at Sea, which came into force on the 1st inst. (and for which we are indebted to Captain D. Forbes, of Southampton), may be read in connection with letter 1375 (p. 185) :— A ship, whether a steam ship or a sailing ship, employed in laying or in picking up a telegraph cable, shall at night carry in the same position as the white light which steam ships are required to carry, and, if a steam ship, in place of that light, three lights in globular lanterns, each not less than 10-in. in diameter, in a vertical line over one another, not less than 6 ft. apart ; the highest and lowest of these lights shall be red, and the middle light shall be white, and they shall be of such a character that the red lights shall be visible at the same distance as the white light. By day she shall carry in a vertical line, one over the other, not less than 6 ft. apart, in front of but not lower than her foremast head, three shapes, not less than 2 ft. in diameter, of which the top and bottom shall be globular in shape and red in colour, and the middle-one diamond in shape and white. The following portion of this article applies only to fishing vessels and boats when in the sea ofi' the coast of Europe lying north of Cape Finisterre : — (a) All fisMng vessels and fishing boats of 20 tons net registered tonnage, or upwards, wlien under way and when not re- quired by the following regulations in this article to carry and show the lights therein named, shall carry and show the same lights as other vessels under way. (h) All vessels when engaged in fishing with drift nets shall exhibit two white lights from any part of the vessel where they can be best seen. Such lights shall be placed so that 214 KNOWLEDGE ♦ [Sept. 12, 1884. the vertical distance between ahall be not Igbb than C ft. and not more than 10 ft. ; and so that the horizontal dis- tance between them measured in a line with the keel of the vessel shall be not less than 5 ft. and not more than 10 ft. The lowest of these two lights shall be the more forward, and both of them shall be of such a character, and contained in lanterns of such construction, as to show all round the horizon, on a dark night with a clear atmo- sphere, for a distance of not leas than three miles. (c) A vessel employed in line fishing with her Unes out shall carry the same lights as a vessel when engaged in fishing vpith drift nets. (d) If a vessel w^hen fishing becomes stationary in consequence of her gear getting fast to a rock or other obstruction, she shall show the light and make the fog signal for a vessel at anchor. (e) Fishing vessels and open boats may at any time use a flare- up in addition to the lights which they are by this Article required to carry and show. All flare-up lights exhibited by a vessel when trawling, dredging, or fishing with any kind of drag net, shall be shown at the after part of the vessel, excepting that, if the vessel is hanging by the stern to iier trawl, dredge, or drag net, they shall be exhibited from the bow. (/) Every fishing vessel and every open boat when at anchor between sunset and sunrise shall exhibit a white light visible all round the horizon at a distance of at least one mile. (g) In fog, mist, or falling snow, a drift net vessel attached to her nets, and a vessel when trawling, dredging, or fishing with any kind of drag net, and a vessel employed in line fishing with her lines out, shall, at intervals of not more than two minutes, make a blast with her fog horn and ring her bell alternately. A ship whyih is being overtaken by another shall show from her stern to such last-mentioned ship a white light or a flare-up light. An " Officer of the Watch," writing to the Times, says : — " In the June number of the Nautical Magazine, a letter ap- peared pointing out the necessity of screening all lights about the decks of ships at sea, except those which are required by the Board of Trade for the prevention of collision, and stating that the Board of Trade surveyors would do well to see that the proper means were at hand for so doing, as the chances of collision would be thereby diminished. On my last homeward passage, in the Bay of Biscay, a large outward-bound steamer was passed between 8 and 10 o'clock one night on our starboard side, and so great was the glare from the lights in her deck saloon (which I took to be lighted by electricity) that her green light was completely outshone, and could not be seen, though well within the range of visibility. 1 should venture to say that, from the size and speed of the ship, she belonged to one of the finest lines of steamers running, and it seems to me rather strange that those in authority in the managing departments of large steamship companies are not alive to what might be a very fruitful source of collision. Had dense smoke obscured the masthead light of this steamer, the direction in which she was travelling would have been left to conjecture." THE EARTH'S SHAPE AND MOTIONS. By Richard A, Proctor. CHAPTER IV. (conHnued from page 196.) OF all parts of the earth's surface the Equator is that where the evidences of the real nature of the earth's relations to surrounding space are most convincing. I think it probable that to many of my readers an account of the nature of the diurnal rotation of the heavens, as witnessed from the Equator, may be at once new and interesting. The north pole, as I have mentioned, has sunk to the horizon when our voyager reaches the equator. Another pole, whose existence had hitherto only been indicated, is now raised from beneath the southern horizon, and lies directly opposite the northern pole. Thus a circle carried from the east point of the horizon through the point ver- tically overhead, and so down to the western horizon, divides the visible heavens into a northern and a southern half, the motions within one half corresponding exactly to the motions within the other. Fig. 1. In Fig. 1, let 0 represent the station of the observer, E, S, W, and N, the east, south, west, and north points of his horizon, Z the point overhead, then E Z W represents the course of a star which rises in the east, and the other curves represent the course of stars rising towards the south and north of east. Every star rises straight up from the horizon, and sets equally square to it. Every star, too, is above the horizon, while describing exactly half of its visible course. Further, as the sun is also visible above the horizon while traversing one-half of its diurnal circle — in other words, as night and day are equal — every star which is visible when the sun sets has passed to the west and set there before the sun rises again ; and every star invisible when the sun set, makes its appearance above the eastern horizon before the sun rises. In other words, all the stars upon the sphere of the lieavens become visible in the course of a single clear night at any place upon the Equator* So that the observer can no longer feel any doubt that the earth is limited in all directions beneath the horizon. Let us consider, then, what our observer has already learned respecting the earth's figure. We shall see that he has obtained enough information to suggest very definite views about the dimensions of the globe on which he has travelled. His first station was at A (Fig. 2). He travelled north- wards to B, and afterwards southwards to C, establishing by the most indisputable evidence the fact that the arc B C is circular, and that the distance of any point upon it from O, the centre of the circle to which the arc belongs, is * After carefully considering the appearances thus presented to the observer situated on the Equator, and recognising the con- vincing evidence these appearances give respecting the trne character of the diurnal rotation, the reader can conceive the indignation with which many gallant naval officers who had often crossed the Equator heard one of the paradoxists lecture at Plymouth to the effect that there is only eue pole of the heavens around which all the stars circulate in places parallel to the plane surface of the esirth. The lecturer, who was as well aware as they were of the absurdity of his views, succeeded in convincing the simpler among his audience, by asserting that in a particular number of the Times which he quoted, it was mentioned in the '' Naval and Military Intelligence," that a certain naval oflicer had seen the pole star from the Tropic of Capricorn (234 degrees south of the Equator). It was in vain for intelligent persons present to assert that this could not be. The lecturer insisted that it was so, and for some time after he left Plymouth, many were actually per- suaded that the earth is plane. At length some one was at the pains to turn over the volumes of the Times in the Plymouth Library, and then it turned out (as was to have been expected) , that the ship from which the pole star had been seen (the fact was merely men- tioned as part of log observations), had been indeed 23 J degrees from the equator, but to the north instead of the south ! Sept. 12, 1884.] ♦ KNOWLEDGE ♦ 215 somewhat less than 1,000 miles. He is now at C, and he learns that in all directions beneath the horizon the earth is limited, because he has proved on indisputable evidence that the stars pass round and beneath the earth, and come up again on the opposite side. He cannot as yet be cer- tain what the shape of the unvisited part of the earth may be, and for aught he knows the section he has found uni- formly curved along BC may elsewhere be as irregular as the broken curve shown in the figure. But he is far more likely to believe that in reality this section has a uniform figure either perfectly or very nearly circular. Fig. 2. Continuing his journey southwards, our observer finds that the north pole of the heavens passes below the horizon, the south pole rising ; and now precisely the same rotations which he had observed respecting the North Pole and the motions of the stars around the polar axis, are jiresented in the southern heavens. As he advances the south pole rises vniformhj — a relation which, as in the case of the North Pole, shows that he is travelling along a circular arc. He sees the apparent stellar motions continuing as uniformly as before. In fact, the only specific difference in the southern skies consists in the fact that the celestial bodies appear to turn in a contrary direction. This circumstance is noticed in the pages of old Herodotus, who mentions (with some doubt whether it may not be a yarn) that seamen who had passed far southward along the shores of Africa, stated that the sun appeared to move from right to left, instead of from left to I'ight, as with us. We, of course, who have followed the steps of our observer, as he has progressed southwards, can at once understand why the heavens should seem to move a different way round the pole, and why the suu, as he ascends towards the north, appears to travel from right to left, whereas ■when he ascended from the east towards the south, he appeared to travel from left to right. We know that the observer in the southern hemisphere who faces the sun when that luminary is at his highest, and the observer in the northern hemisphere who does likewise are facing each other, so that a motion which is from right to left, as seen bj one, is from left to right as seen by the other. {To he contiiiued.) BRITISH SEASIDE RESORTS, FKOM AX UKCOXVEXTIOXAL POINT OF VIEW. By Percy Russell. IV. THE Isle of Man is, in some respects, the most remark- able of all the islands of England and Wales, and from Snaefell, the highest of its rugged but majestic moun- taius, there may be had one of the most splendid panoramic views in all the Biitish isles. Thence, indeed, is commanded at once a distinct panoramic view of a very considerable extent of the coasts of England, Wales, Ireland, and Scotland. That noble estuary the Solway, hallowed by so many legen- dary and historic associations — Ailsa Crag, the famous Mull of Galloway, and the wild mountains of the vicinity- are all prominent features, and compose a scene that can hardly be surpassed for beauty and boldness of land and seascape anywhere. The length of the Isle of Man is 33] miles, the breadth about 12.',, thus bringing every portion within easy pedestrian reach of the sea, and the area is generally computed at 145,325 acres, of which full 50,000 remain virtually in a stite of nature. The Calf of Man is a small islet at the south-west extremity, containing oidy about 800 acres of surface. A chain of veritaVjle mountains extends from uorth-east to south-west, Snaefell, the highest, being 2,024 ft. above the sea-level. The general scenery is rich in variety, such as most delights the landscape-painter. There are numerous picturesque glens, which seem ex- pressly made for the still life of poetry or romance, and rich undulating tracts of cultivated country, and in fine weather, such a clear atmosphere that the very cornfields when in their full golden glow can be distinctly seen on the adjacent shores. Many beautiful streams rush down from the mountains, and in some of these are excellent salmon- trout, although I am sorry to say that washings from the lead-mines in the interior have in many cases quite destroyed the fish. Some parts of the interior are boggy, but the glens separating the numerous hills and mountains are frequently wooded with beautiful beech-trees and elier, and the numerous mountain torrents, ending often in beautiful waterfalls, impart a strange charm to the varied landscape. Most of the villages, farm-houses, and churches are em- bowered in trees, and, for sott rural beauty, the interior of this remarkable island leaves nothing to be desired. The coast is, in many places, of ineffable grandeur, and some of the most formidable precipices are in the immediate neigh- bourhood of the wild loneliness of harbours, shelving shores, and villages framed in woods, and presenting every- where quite a material presentment of true pastoral poetry. Douglas, deriving its name from being at the junction of two streams — the Dhoo (black), and Glass (s^rey; — lies on the edge of a very picturesque bay. Castle Mona, once the residence of a Duke of Athol, is now a good hotel, and another conspicuous landmark is the Tower of Refuge, built on a rock, for the benefit of shipwrecked seamen. The ancient town is interesting in its narrow streets, but there are comparatively modern marine residences in the recently-buUt portion, and not only is the living cheap, but the bathing is remarkably good, and the water is singularly free from mud, seaweed, or even s-hells. The coast north of Douglas is highly precipitous, and what givas beautiful colour in summer to the scenery, is often green with foliage almost to the water's edge. The striking promontory of St. Maughold's Head should be notici-d. Tbe well-known town of Peel, formerly called Holm, is reujarkable, inter alia, for its grotesque and romantic caverns, which re- semble nothing so much as sundry of Victor Hugo's poetic flights into the region of the terrible made visible. A small river enters the sea at Peel, and thence once on a time Manx salmon was exported. South of Peel is Brada Head, a truly stupendous pile of black rocks, somewhat like those which give to Spanish Head, close to the Calf of Man, such an imposing appearance. The lead-mines often run here close to the sea, as in Cornwall. The Spanish Headland is very grand, and the masses of rocks off the coast lo k like piles of huge timbers or regular blocks of masonry all laid ready for rearing some colossal structure, while the prevailing blackness of the cliffs im- 216 ♦ KNOWLEDGE • [Sept. 12, 1884. parts a grim and stern character to what is certainly remarkable scenery. But to return. One of the great attractions of Peel is, of course, its terrible castle, once the frequent residence and long the formidable fortress of those Lords of Man, the Earls of Derby. The prison vaults under the castle still exist, fearful mementos of what feudal imprisonment meant ; and here Elinor Cobham, Duchess of Gloucester, was im- prisoned for life. This place is also connected with the old Manx legend of a spectre dog, which it was a very serious matter indeed for any one to encounter. The fine ruins of the Cathedral of St. Germains, built 1245 A.D., should be examined, and the insulated rock on which these re- main— Sodor — possesses permanent interest, being, like the historic lona, the place whence the original savages of the islands first derived some of the lights — very broken they were, in truth — of mediteval knowledge. Sodor, as every- body knows, has puzzled etymologists considerably ; some authorities declaring that it is simply derived from Sudureys, which would mean merely the Southern Hebrides, with which the Isle of Man was once associated. Very great improvements have been efiected of late years at the principal ports of the island, and particularly is this the case at Douglas. I obtained recently some special information on this head from Sir Henry B. Loch, whose beneficent rule will long be remembered by the Manxmen, and who is now the Governor of Victoria, Australia. Sir Henry did much to advance the material progress of the island, and in im- proving the social and moral state of the people he was ably seconded by Lady Loch. In the space of five years only the tonnage entering Douglas was raised from a value of £100,000 to £500,000, and the splendid sea defence and docks constructed in the harbour are reckoned as among the largest examples of solid concrete at the greatest depth of water in the United Kingdom. (To be continued.) NOTES ON COAL. By Richard A. Proctok. IT has become a question of serious import whether we may indeed look confidently for abundant supplies of coal during many future years, or whether those have been in the right who have told us that before the close of the present century this country must feel the effects of the over-rapid working of our chief coal-fields. I propose briefly to sketch what is known about the origin of coal, and then to touch on the subject of the supply of this mineral, with special reference to the requirements of our own country. A mistaken impression is somewhat widely prevalent that, in the coal-fields, we have the remains of ancient forests ; in other words, it is supposed that, wherever there was a forest in primeval times, there now exists a coal-field of greater or less extent. In connection with this view, also, the opinion is entertained that the forests now in existence will, in process of time, and after due geological changes, become the coal-beds of future ages. But although, as we shall presently see, the coal-fields are undoubtedly due to the vegetation of former eras, it is far from being the case that the primieval forests became converted in a general way into coal. Conditions of a pecu- liar, and to some extent exceptional, character were requi- site for the formation of coal-fields. If we consider the evidence given by the coal-fields themselves, we shall see ■what these conditions wera The beds or seams of coal form but a small portion of the thickness of the great geological group of strata to which they for the most part appertain. This group is called the carboniferous, and not uncommonly " The Coal " ; but even where coal is most abundant, it forms only a minute part of the whole mass. Thus it has been estimated. Sir Charles Ljell tells us, that in South Wales the thickness of the carboniferous strata amounts in all to between 11,000 and 12,000 feet (or more than two miles);* " but the various coal-seams do not," according to Professor Phillips, " exceed in the aggregate 120 feet," or little more than one-hundreth part of the whole. In North Lanca- shire the carboniferous strata occupy a depth of more than three and a half miles, with the same relative disproportion between the thickness of the coal-seams and that of the complete series of strata. Again, in 'Nova Scotia the coal- bearing strata attain a thickness of more than three miles, t Here no fewer than eighty seams of coal have been counted (seventy-one having been exposed by the action of the sea) ; but these seams are nowhere more than five feet in thickness, and many are but a few inches thick. Thus it is evident that the formation of coal can have been in progress but for a short portion of the time during which the great carboniferous series of strata was in process of deposition. Throughout by far the greater portion of that time other minerals were being deposited. It is next to be noticed that under each coal-seam a stratum of older soil exists, in which there ai-e commonly found the roots of ancient trees ; while above the coal there is commonly a layer of shale or sandstone, in which not unfrequently the trunks of those trees are found either fallen or still in their original position, and only partly converted into coal. The bark remains, but is transmuted into coal ; the hollow of the trunk, decaying long before the trunk gave way, is represented by a cast in sandstone. Thus, if we try to picture to ourselves the state of things which existed when such a seam of coal first began to be covered up by the next higher deposit, we see that there must have been trees standing erect above a layer of vegetable matter, the roots of the trees being imbedded in the soil which forms the deposit next below the coal. The vegetable layers may probably have been two or three times as thick as the resulting coal-seam, and were reduced by pressure to their present thickness ; but such layers cannot at any time have reached to the branches of the forest-trees. Then the process of deposition began. This can only have happened when some subsidence of the soil had caused it to be submerged to a greater or less depth. We can infer from the depth of the strata overlying the coal-seams that this state of submergence continued in many cases for a long period of time ; £md it is equally clear that the formation of the vegetable layers themselves must have been a process occupying a considerable time, since tall trees grew before the next submergence took place. So soon as submergence was complete, the tall trees perished and began to decay. The stout trunks above the vegetable layer were broken off and swept away by the * It is, perhaps, hardly necessary to remark that this depth has not been measnred anywhere in a vertical direction. The thick- ness of the several layers can be measured where they either crop out, or show at the surface, or else come within the range of mining operations ; and thus the total depth of the series can be estimated. t The way in which this has been made known is worthy of notice. In the Bay of Fundy the tides run to an enormous height. The tidal wave can be seen when it is stUl thirty mUes away, advancing with a prodigious uproar, and rising sometimes to the height of more than a hundred feet. These tremendous waves have not only produced a continuous section ten miles long, through the inclined strata, but by their action they sweep away continually the whole face of the cliffs, and bring into view fresh sections year after year. Sept. 12, 1884.] KNOWLEDGE ♦ 217 sea. The forest itself, properly so called, was for the most part thus destroyed. It was the decaying refuse of the forest, intermixed with the lowlier growths, which formed the coal-seam as it now exists. Amongst these were the lower parts of the trunks of the ancient forest-trees. These became converted, like the rest of the vegetable matter, into coal. But it may be asked how those portions of the trunks which still remain above the level of the vegetable layer are to be accounted for. Are we to suppose that they remained erect after the sea had made its way into the domain of the ancient forest 1 Many geologists think so ; and doubtless the stumps of stout trees might resist for a long time the action of the sea waves. But there seems good reason for believing that, when the submergence first took place, these stumps stood but little above the upper surface of the vegetable layer, or that in many instances the trees were broken off even below that level. Then, as the pressure of the superincumbent layer gradually in- creased with the layer's increase of thickness, the vegetable matter was pressed down below its former level, and the stumps were left standing above the depressed surface of the vegetable layer. This explains the conversion of the bark of these stumps into coal, since there is every reason to believe that stumps simply left imbedded in sandstone would not change into pure coal. In passing, I may remark that in whatever way it happened that the stumps of the ancient forest-trees re- mained standing above the level of the vegetable mass forming the coal-seam, a strange result has followed. The upper part of the stem became filled, as I have said, with sandstone, forming a cast of the interior of the ancient tree ; the bark became coal ; and outside the bark is sandstone again. Thus there is a mass of sandstone separated from the surrounding sandstone by a tube of coal. This mass is not cylindrical, being larger below than above ; so that if in any way the mass ceases to be supported, it falls like a bolt from a gun. But in working the coal-seam the material which had supported the sandstone mass is neces- sarily removed. Hence the miners look with dread on these coal-pipes, as they are called, which each year cause fatal accidents in the Newcastle and other coal-fields. As Sir Charles Lyell well remarks : " It is strange to reflect how many thousands of these trees fell originally in their native forests in obedience to the law of gravity, and how the few which continued to stand erect, obeying, after myriads of ages, the same force, are cast down to immolate their human victims." (To he continued.) NOVEL TRICYCLES. By John Browning. (Chairman of the London Tricycle Cluh.) THE ElIPEEOK. HAVING obtained one of these very novel machines, I took it to Reigate to give it a thorough trial. On mounting the machine, for the first few minutes' riding my course was somewhat erratic, showing that it requires a little practice in steering. The difficulty was soon sur- mounted, and I may say at once that the machine is certainly easier to steer that the Humber, and that with experience it is completely under control. The method of applying the brake by means of the left foot is very peculiar, and at first a rider feels awkward in using it, but this feeling soon wears oft'. When running down a long hill with varying grades it seems difficult to vary the pressure of the brake with the foot ; yet there is a simple method, as I discovered in my second ride, by which this may be done with the greatest delicacy. Whenever the brake has to be applied continuously for some time, the left foot should be put on the brake- pedal just above the axle, and the right foot on the opposite, or right-hand side of the axle, then a slight lifting action of the rir/ht foot — that is, a slight decrease in the pressure of the right foot — will cause an increase of pres- sure on the left foot, and thus the brake can be applied as geutly as any hand-lever brake, and the pressure regulated with as much nicety. I agree with Mr. Bennett, who tells me that he has ridden 1,500 miles on the Emperor, that it is desirable that the power of the brake should be in- creased for the steepest, that is, downright dangerous hills. The Emperor is a good hUl-climber. I have ridden the Woodhatch-hill, out of Reigate on to Earlswood-common, on a machine geared to 52 in., and that without practice and without strain. Some skill is undoubtedly required to ride the Emperor, but what it requires, more than skill, is confidence. It looks and feels a risky thing to do, to put your feet up on the axle when flying a hill, but it is tolerably easy and safe to do it, unless the hUl is almost unrideably steep. The machine is made with 42-in. side-wheels, geared to 52 in. The hind wheel, which is about 30 in. diameter, is the driving-wheel, and is driven by means of a chain. The machine is a front-steerer, both the front wheels moving with the axle for steering. It is, of course, a single driver, but I have not as yet found the driving-wheel slip, either on mud or dust, even when climbing hills. Some contrivance is required for tightening the chain when it becomes slack. The Emperor can be mounted or dismounted either from the front or behind. 1 prefer to mount it behind from the pedal, and dismount from the front over the axle. There is no fear of falling head first out of this machine when descending a hill, as, if the feet are in their proper place on the brake and axle, the rider has an open front before him, and can always come down on his feet. If the Emperor were made about 5 lb. or 10 lb. lighter — and this might easily be done — and a little more brake power were given, the machine would, I think, take a good position, and soon be a favourite. But as back-pedalling can only be performed with one foot, the brake on this machine is all important, and unless the brake-power on the hind driving-wheel can be increased — which I venture to doubt — it will be necessary to apply band-brakes to both the front wheels, which might be done readily by means of a hand-lever ; and to this moat riders would give the preference. The Emperor may be obtained of Mr. Brooke Hitching, the tricycle agent of Ludgate-hill, E.G. THE COVENTRY CHAIR. A year or more ago I suggested in Knowledge that Sociable tricycles might be employed at country railway- stations to carry passengers and luggage. Messrs. Starley &. Sutton, the manufacturers of the Meteor and the Rover, have brought out a modified tricycle which they call the Coventry Chair. This is intended to supersede the present Bath Chair, which is now generally dragged along at a crawling pace of about two miles an hour at the utmost. The Coventry Chair can be driven easily at a pace of five or six miles an hour. The wheels have india-rubber tyres, and the chair is mounted on tricycle springs ; the motion is therefore easy and pleasant. The engraving shows that the invalid sits on a light wicker 218 ♦ KNOWLEDGE ♦ [Sept. 12, 1884. chair, in front of and below the driver, who pedals behind him. In a trial which recently took place of the Coventry Chair, an untrained workman, with a sitter weighing between eleven and twelve stone in the chair, drove from Coventry to Birmingliam, and back — a distance of thirty- five miles — in four and three quarter hours, including stoppages amounting to thirty-five minutes ; the riding time was thus only four hours and ten minutes — a pace of between eiyht and nine miles per hour. I expect very soon to see some Coventry Chairs in our sea-sifie watering-places, and wish the ingenious and spirited inventors success. I cannot resist the opportunity of pointing out how this machine proves the accuracy of one of my so-called theories that a large amount of weight may be thrown upon the front steering-wheel of a tricycle with advantage. THE NEW QUADRANT. Messrs. Lloyd Bros, have kindly shown me a new front- steering Quadrant tricycle, of which I think highly. The machine is very light, weighing only .50 lb. with a brake. It has 40-in. driving-wheels, and a 2G-in. frout-steering- wheel. Of course, this laige steering-wheel lias only been rendered possible by the use of the ingenious Quadrant system of steering. The makers have had the courage to throw the weight of the rider on to the steering-wheel and in front of the driving-wheels, and so to dispense with the weight and inconvenience of back-stays to prevent the machine from capsizing backwards. I say they have adopted the correct plan in making a machiue which can- not in this particularly dangerous manner be capsized, because I have known of two bad accidents occurring to my own friends, owing to these back stays, which were to prevent accidents, themselves giving way. The driving-wheels of this Quadrant are only 40-in. diameter, and it is spoken of by those who have tried it as an exceedingly fast machine. I confess I feel greatly interested in its success, as it embodies every important point in its construction which I have for some time been urging on manufacturers, viz., small driving-wheels, large front-steering-wheel, and the weight of the rider thrown well upon it. Its success would prove, in a machine which can be purchased in the open market, that the advantages of small wheels are not, as has been so frequently asserted, confined to the Humber type of tricycle. 1 should exceedingly like to test this new Quadrant well, but the only machine I could get at present is one without a brake, geared to 60-in. Now a .jO-in is the very highest gearing I can ride with advantage in a one-speed machine, and I should, therefore, be only trying myself, and not the machine, if I were to take it, as I should do, over a hilly line of country, as I consider this the true method of testing a tricycle. I anticipate that this will prove the fastest of the front- steeiiiig machines, as well as one of the safest. THE CLUB TANDEM. The Coventry Machinists' Company have introduced yet another new Tandem. This machine is a good front- steering tricycle, with a movable backbone attached by a joint behind in the centre of the axle. This carries a small wheel and a saddle for a second sitter. The front rider steers, but the machine can be arranged so that either rider can steer, and either rider can now apply the brake. The riders do not sit so close together as on many- Tandems. By removing three small bolts the Club Tandem can be converted into an excellent front-steering machine for a single rider. I have had no experience in riding this machine, though I have been on one, but I do not see how it can fail to perform well. THE INTERNATIONAL HEALTH EXHIBITION. XV.— WATER AND WATER-SUPPLIES— (coM^inwd). Type VI.—" Chamberland's " Filter.— Amongst the interesting group of exhibits in the French Court, under the direction of the distinguished professor of the Ecole Normale, of Paris, there are a few examples of this type of filter open to inspection. It has been specially designed for laboratory work, and consists of a hollow cylinder closed at one end, made out of biscuit china ; probably a hydrous silicate of alumina and lime passed through a preliminary or biscuit furnace. The water is forced to percolate through the walls of this comparatively dense material, and, in doing so, becomes divested of even the minutest aerms, such as Bacilli, ic. ; and, so thoroughly does it accomplish its work, that M. Pasteur has relied upon it for water in his experiments upon the culture of the lower forms of life. Type VII.— Maignen's "Patent Filtre Eapide." We Sept. 12, 1884.] ♦ KNOWLEDGE 219 have reserved this type of filter for our final example, ina-smuch as it will help us to explain in detail what a thoroughly good household filter ought to be. Water suitable for drinking and cooking should be free from taste and smell, yet so aerated and cool as to become refreshing. It is needless to say that it ought also to be not only free from harmful matters, but more, its administration should be beneficial. The commonest impurities that are met with in waters are adventitious particles derived from the earth or its atmosphere ; they are more or less of appreciable dimensions, and include such matters as the silt and other detritus of streams, and organic matter, both Jiving and dead. There are also other impurities of a less evident nature, derived from both living and inert matter dissolved in the water ; so that the requirements of a perfect filter are twofold : it should be an eflicient mechanical strainer as well as a chemical separator. Nor is this all ; it must conform to the peculiar senses of man ; to his organs of taste, his eye, and — if the truth must be written — to his pocket. We insist at the beginning that the domestic filter shall be " a thing of beauty," even though it be made of such a homely substance as brown stoneware. Placed upon the sideboard, chiflbnier, or other stand, the tap should be at a convenient distance from the surface of the table, so as to permit of the easy insertion of a tumbler beneath it, as shown at Fig. 29. Such pedestals, we are glad to find. Fig. 29.— Maignen's Re- frigerating Stand, with "Filtre Kapide" and Ball- valve attached. Fig. 30. — Sectional view of the "Filtre Rapide." A, unfiltered water ; B, screen ; c, granular " carho calcis" ; D, powdered " carbo calcis" ; E, asbestos cloth ; M, filtering frame ; K, reservoir. are supplied by !Mr. Maignen ; and we notice with pleasure that he has turned the pedestal to account to serve as a " refrigerating stand," Fig. 29, where the filtered water is made to pass through a non-oxidisable tin pipe imbedded in ice — a most delightful luxury for the summer months. The filter-case ought to be constructed in such a way as to permit of being taken to pieces, and the shapes of the component parts such as to allow of their being easily and thoroughly cleansed. It is but our duty to state that Mr. P. A. Maignen must always be associated with this most important advance in the structure of filter-cases as its originator, and we may point to Fig. 30 as substantially a perfected model We need not here enter into a detailed explanation of Mr. Maignen's filter-case, as we have already done so in a former issue. Those of our readers, however, who cannot have access to our previous brochures, and who are desirous of learning something more about Mr. Maignen's filter-case than the pictured description, Fig. 30, would do well to write to him for a copy of his excellent pamphlet on the filtration of water.* We may observe, however, that the filtering mechanism consists of a funnel, M, Fig. 30, the expanded portion of which is pierced by- many circular apertures ; that oi-er this an asbestos cloth is fitted ; and that the filtering medium is deposited uniformly over the ichole of this surface. The idea of the asbestos cloth and perforated funnel has, we find, been taken ad- vantage of by another manufacturer, but, most unfortunately for him, he has reversed the funnel and made a kind of a bag of it; over the hollow cone the asbestos cloth is tied, and the perforations in the funnel are elongated slits ; hence it is obvious that the filtering surface is only par- tially available, and the filtered water is not properly aerated, as in the filter-case Fig. 30, where the stem of the funnel, suitably plugged with cotton wool, to prevent the entry of disease-germs, allows a stream of purified air to enter the reservoir of filtered water underneath. The asbestos- cloth surface is undeniably Mr. Maignen's invention ; it is of such a nature, that a very fine powder, such as the " carbo calcis," enters into association with it in such a way as to form one of the most perfect strainers known. The cloth is subjected for a prolonged time to an intense heat, so as to thoroughly purify it ere it is sent out with the filter, and in order to cleanse it after continued use, Mr. Maignen directs that it ought to be washed, and then roasted before a clear fire ; this can be done in any kitchen. The filtering medium is termed carbo calcis, because it is made of pure carbon and pure lime, combined by the patented process. It is in such a fine state of division that it has been estimated that one square inch, | inch thick, contains over 200,000 square inches of adhesive or straining surface. Thus, when spread over the asbestos cloth, it ought to be capable of preventing ihe passage over of even the smallest germs — e.g., excessively small Micrococci measure only about -^^g inch in diameter, and other Bacteria and Bacilli are proportionately larger ; even the jtagella of Bacterium termo, i.e., the whip-like terminal appeudicular organs of motion of the organism, measure 2 0*7 0 0 i"<=h in breadth.! Fig. 31.— A Tillage Filter House. Over the fine layer of powdered carbo calcis, D., Fig. 30, a quantity of granular carbo calcis may be placed, as at C, Fig. 30 ; this does not only arrest the coarser impurities in * " Water, Preventable Disease, and Filtration." By P. A. Maignen. 22 and 23, Great Tower-street, London, E.G., 18S-1. t Dallinger, " Monthly Microscopical Journal," London, vol. xiv. p. 105. 220 ♦ KNOAVLEDGE ♦ [Sept. 12, 1884. the water, but prolongs the efficacy and speed of the filtra- tion. As a chemical reactor, carho calcis is equal, if not superior, to any other medium of its kind. It removes iron, lead, sewage poisons, and even ammonia and sulphuretted hydrogen. It also reduces the hardness of water to an appre- ciable extent. As soon as it becomes foul, it may be replaced by a fresh charge at a trifling cost, and thus entirely over- comes the objection to the use of organic carbon as a filtering agent. The requirements of a good drinking water are that it shall be tasteless, odourless, colourless, cool, and refreshing ; that, in order to be so, it shall be ai'i-ated with purified air or carbonic acid gas ; and that it shall neither be too hard nor too soft, and be free from all septic or other dele- terious impurities. The filter that can modify foul water which is alike disagreeable to the eye, nose, and mouth, and which, when it enters the alimentary system, becomes dangerous, and endow it with all the qualities of good, wholesome water, and which, moreover, is within the reach of the humblest cottager, needs no word of commendation — it speaks for itself. Such a filter is Maigoen's. It is not, then, a matter for astonishment that the Exe- cutive Council have deemed the " Filtre Rapide" worthy of the place they have assigned to it, and visitors to the Exhibition may now drink freely from the fountains with- out any fear of being injured thereby. Mr. Maignen has in- formed us that he has recently furnished the " Nile Expedition Commission" with 800 filters. Each instru- ment is capable of purifying from ten to twenty gallons per hour, measures 18 by 12 by 10 inches, and weighs only 1 G lb. Two buckets are telescoped round the filter, one furnished with a long strap to draw the water from the river, and the other placed under the filter to receive the purified water. We believe that Sir Peter Lumsden has also taken a few of these valuable travelling companions with him to Afghanistan. Doubtless the merits of the Filtre Rapide will soon make it a universal favourite, when the village smithy may be flanked on one side by its rural "Filter House" (Fig. 31), and water companies seek its aid to give us better water. OTHER WORLDS THAN OURS. A WEEK'S CONVERSATION ON THE PLURALITY OF WORLDS. By Mons. de Fontenelle. with notes bt richard a. proctor. THE SECOND EVENING (continued). " X)UT what do you think," said she, "of the people in JlJ the moon ; are they as fearful of an eclipse as we are "i It would be a good jest to see the Indians there up to the neck in water ; that the Americans should believe the earth angry with them ; the Greeks fancy we were bewitched, and would destroy their plants ; in short, that we should cause the same consternation among them, as they do here." " And why not f' said I. " I do not doubt it at all ; for why should the people of the moon have more wit than we 1 What right have they to aflVight us, and not we them 1 For my part, I believe that since a prodigious company of men have been, and still are such fools to adore the moon, there certainly are people in the moon that worship the earth, and that we are upon our knees the one to the other." " But sure," said she, " we don't pretend to send any influences to the moon, and to give a crisis to her sick ; if the people have any wit in those parts, they will soon destroy the honour we flatter ourselves with, and I fear we shall have the disadvantage." " Fear it not, madam," said I ; "do you think we are the only fools of the universe? Is it not common for ignorance to spread itself everywhere t 'Tis true, we can only guess at the folly of the people in the moon, but I no more doubt it, than I do the most authentick news that comes from thence." " What news comes from thence ? " said she. " That which the learned bring us," I replied, " who travel thither every day with their tubes and telescopes ; they will tell you of their discoveries there, of lands, seas, lakes, high mountains, and deep abysses." "I fancy, indeed," said she, "they may discover mountains and abysses, because of the remarkable inequality; but how do they distinguish lands and seas 1 " " Very easily," said I ; " for the waters letting part of the light pass thro' them, send back but a very little, so that they appear afar ofllike so many dark spots* ; whereas the lands being solid, reflect the whole light, and appear to be more bright and shining. The illustrious Monsieur Cassini, a most compleat astronomer, has discovered something in the moon which divided, then reunited, and sunk in a kind of well : we may very probably suppose this was a river. Nay, they pretend to be so well acquainted with the several places, that they have given them all names: one they call Copernicus, another Archimedes, another Galiteus : there is the Caspian Sea, the Black Lake, the Porphyrite Mountains ; in short, they have publish'd such exact descriptions of the moon, that a very almanack-maker will be no more to seek there than I am in Paris." " I must own, then," said the Marchioness, " they are very exact ; but what do they say to the inside of the country 1 I would very fain know that." " 'Tis impossible," I replied ; " the most learned astro- nomers of our age cannot inform you. You must ask that of Astolfo, who was carried into the moon by St. John. I am going to tell you one of the agi-eeable follies of Ariosto, and I am confident you will be well pleased to hear it. I must confess he had better have let alone St. John, whose name is so worthy of respect ; but 'tis a poetical licence, and must be allowed. The poem is called ' Orlando Furioso,' is dedicated to a Cardinal, and a great Pope has honoured it with his approbation, which is prefixed to several of the editions. This is the argument : Orlando, nephew to Charlemain, runs mad because the fair Angelica prefers Medore before him. Astolfo, a knight-errant, find- ing himself one day in the terrestrial Paradise, which was upon the top of a very high mountain, where he was carried by his flying horse, meets St. John, who tells him, if he would have Orlando cured, he must make a voyage with him into the moon. Astolfo, who had a great mind to see new countries, did not stand much for entreaty ; and im- mediately there came a fiery chariot, which carried the apostle and the knight up into the air. Astolfo, being no great philosopher, was surprised to find the moon so much bigger than it appeared to him when he was upon the earth ; to see rivers, seas, mountains, cities, forests, nay, what would have surprised me too, nymphs hunting in those forests ; but that which was most remarkable was a valley where you might find anything that was lost in our world, of what nature soever — crowns, riches, fame, and an infinity of hopes ; the time we spend in play and in searching for the philosopher's stone ; the alms we give * It is interesting to find Kepler's notion that tlie dark parts of the moon are seaa prevailing after Cassini's time. — R. P. Sept. 12, 1884.] KNOWLEDGE ♦ 221 after our death, the verses we present to great men and princes, and the sighs of lovers." " I know not," said the Marchioness, " what became of the sighs of lovers in Ai-iosto's time, but I fancy there are very few of them ascend to the moon in our days." " Ah, madam," replied I, " how many does your Lady- ship send thither every day t Those that are addressed to you, will make a considerable heap ; and I assure you the moon keeps all safe that is lost here below. Yet I must tell you, Ariosto does but whisper it, though every thing is there, even the donation of Constantine, (the Popes have pretended to be masters of Rome and Italy by virtue of a Donation which the Emperor Constantine made Sylvester ; and the truth is, nobody knows what is become of it.) But what do you think is not to be found in the moon 1 Folly ; all that ever was upon the earth is kept there still ; but in lieu of it, it is not to be imagin'd how many wits (if I may so call them) that are lost here, are got up into the moon ; they are so many vials full of a very subtile liquor, which evaporates immediately, if it be not well stopp'd ; and upon every one of these vials the names are written to whom the wits belong ; I think Ariosto has heap'd 'em upon one another a little confusedly ; but, for order sake, we will fancy 'em plac'd upon shelves in a long gallery. Astolfo wondered to see several vials full, inscribed with the names of persons whom he thought considerable for their wisdom. To confess the truth, I begin to fear, since I have entertained you with these philosophical and poetical visions, mine is not very empty : however, 'tis some consolation to me, that while you are so attentive, you have a little glass full, as well as your humble servant. The good knight found his own wits among the rest, and, with the apostle's leave, snuifed it all up his nose, like so much hungary-water ; but Ariosto said he did not carry it far ; it returned again to the moon a little after. * The love of one fair Xortheni lass, Sent back his wit unto the place it was. " Well, he did not forget Orlando's vial, which was the occasion of his voyage ; but he was cursedly plagued to carry it, for heroes' wits are naturally very heavy, and there did not want one drop of it. To conclude, Ariosto, according to his laudable custom, addresses himself to his mistress in the following beautiful verses : — Fair mistress, who for mo to Heaven shall fly, To bring again from thence my wandering wit ? Which I still lose, since from that piercing eye, The dart came forth that first my heart did hit : Nor of my loss at all complain would I, Might I but keep that which remaineth yet; But if it still decrease, within short space, I donbt I shall be in Orlando's case. Tet, well I wot where to recover mine, The' not in Paradise, nor Cynthia's sphere, Yet doubtless in a place no less divine, In that sweet face of yours, in that fair hair. That ruby lip, in those two star-like eyes, There is my wit, I know it wanders there ; And with my lips, if yon would give me leave, I there would search, I thence would it receive. " Is not this very merry 1 To reason like Ariosto, the safest way of losing our wits is to be in love ; for you see they do not go far from us, we may recover 'em again at our lips; but when we lose 'em by other means — as, for example, by philosophising — whip, they are gone into the moon, and there is no coming at 'em again when we would." " However," said the Marchioness, " our vials have an * Sir J. Harrington's translation of " Orlando Purioso," lib. 36. honourable station among the philosophers, when 'tis forty to one but love fixeth our wits on an object we cannot but be ashamed of. But to take away mine entirely, pray tell me, but tell me seriously, if you beUeve there are any men in the moon ; for methinks hitherto you have not been very positive." (To be continued). ©Iritorial (gosstp. A CURIOUS illustration of the impossibility of abolishing social distinctions reaches me from the other side of the Atlantic. In an article on " Second-class Cars," in the Railwatj Revieiv (a journal published in Chicago), I read : — Xo matter how much we may ignore, theoretically or politically, the existence of class distinctions as something foreign to our system of government, they do exist, nevertheless, as rigorously and as unavoidably here as anywhere e!se, and in the relations o£ business they have got to be dealt with as snch. Just SO ; for, as Horace wrote some 1,900 years ago, " Naturam expellas furca, tamen usque recurret." You may decree that one man shall be as good as another (and, according, the Irishman's addendum is the venerable Joe Miller, " A grate dale betther too ! "), yet people will no more meet universally on an equality than oil and water will unite in a bottle. You will never get the possessor of birth, cultivation, and refinement to consort freely with the vulgar and illiterate man, if you shout " Liberty, equality, and fraternity " until you are black in the face ; and the suggestion (from a purely business point of ■i-iew) to establish second-class carriages in the greatest Republic in the world affords pretty convincing proof that it is as impossible, by legislation, to equalise men's social relations as it is the length and shapes of their noses. I WAS, I confess, much interested to read extracts from EJsowLEDGE in the Hindu Excelsior Magazine, a monthly Madras journal, conducted — and very ably conducted, too — by a native gentleman, Mr. R. Sivasankara Pandiah, B.A. It is pleasant to find that words penned primarily for Englishmen are read with appreciation by those who, though of different race and creed, and separated from us by so many thousands of miles of land and water, are yet our friends and fellow-subjects. Every one who has an interest (and who has not V) in the condition of our Lunacy Laws, should read the re- markable series of papers, " My Experiences in a Mad- house," which began in the Pall Mall Gazette for Aug. 27. From some further particulars of the balloon of MM, Renard and Krebs which have been received, it would appear that its lifting power in excess of the entire weight was but small, and that the weather was " presque calme." It remains to be seen what progress can be made against a gale of wind — or even a stiff breeze. I fear that the problem of aerial navigation is not yet solved. I HAVE received the Presidential address (on Psychology) of the Hampstead Naturalists' Club, and am glad to find that excellent Local Association in so flourishing a condi- tion. The Citizen states that since the removal of the Natural History Collections from the British Museum to South Kensington the number of daily visitors has diminished from 2,500 to about 1,000. 222 ♦ KNOWLEDGE . [Sept. 12, 1884. AN APOLOGY TO DR. KTNNS. I INTIMATED, on p. 204, my earnest anxiety that justice should be done to Dr. Kiuns. I now hasten to render it. Having carefully read through the edition of his book just published, from beginning to end, I feel that, differing, as I do, from him in the inferences he draws from his facts, I can the more willingly, and with the ler^s bias, bear testi- mony to the entire accuracy of the very large number of scientific facts which he has brought together. A para- graph on abnormal refraction which appeared in the only edition of " Moses and Geology " that I had previously seen (and upon which I placed an interpretation repudiated by Dr. K.) has been expunged from the present one ; and I can only frankly express my regret that I should have brought a charge of ignorance, which a simple perusal of the volume before me suffices amply to refute. I do not know whether it is necessary to reiterate here that I never did — as assuredly I never intended to — make the very slightest insinuation against Dr. Kinns's personal character, honour, or veracity. They have been as unassailed in these columns as they are unassailable. ilftiifliiS* SOME BOOKS ON OUR TABLK Suggestions for Eslahlishing Popular and Educational Museums. By Teos. Laurie. (London : Laurie.) — In this pamphlet Mr. Laurie offers suggestions for the esta- blishment of local museums of science and art, which may be studied, not without profit, by those interested in popular education. His ideas as to the collection of ■objects illustrating the local industry of the place in which the museum is situated seem good, and he further gives a list of anatomical and physiological models, works of art, wall charts, ifcc, which he considers should form part of every collection established for educational purposes. Hospital Sunday and Hospital Saturdaij. By Henry C BuBDETT. (London : Ivegan Paul, Trench, &. Co. ) 1884. — Mr. Burdett finds gi-ave fault with the administra- "tion of the funds collected on what are known as Hospital Sunday and Hospital Saturday — especially with the latter. All who are anxious that the very large sums of money gathered on these days should be applied to the greatest advantage to the alleviation of sickness and suffering, should study the pamphlet whose title heads this notice. Children's Dress. A Lecture delivered in the Lecture- room of the International Health Exhibition by Miss Ada S. Ballin. (London : W. Clowes