Frans Cornells Donders For Mem R S Bora 27 May 1816 Died 2* March 1883 PROCEEDINGS ROYAL SOCIETY OF LONDON. VOL. XLIX. LONDON: HARRISON AND SONS, ST. MARTIN'S LANE, f) rintcrs in ©rbinarg to Her l^ajtstg. MDCCCXCI. LONDON: HABBIBON Mil) SOX?, PRINTBBB IK ORPTNAKY TO HEK MAJESTY, ST. MARTIN'S LANE. CONTENTS. VOL. XLIX. No. 296.— December 11, 1890. Pa«e On Ellipsoidal Harmonics. By W. D. Niveu, F.RS 1 Photometric Observations of the Sun and Sky. By William Brennand.... 4 Determinations of the Heat Capacity and Heat of Fusion of some Sub- stances to test the Validity ef Person's Absolute Zero. By Spencer Umfreville Pickering, M.A., F.RS 11 On Wolf and Rayet's Bright-Line Stars in Cygnus. By William Hug- gins, D.C.L., LL.D,, F.RS., and Mrs. Huggins 33 On Stokes's Current Function. By E. A. Sampson, Fellow of St. John's College, Cambridge „ 46 List of Presents „ 53 December 18, 1890. On a Determination of tke Boiling Point of Sulphur, and on a Method of Standardising Platinum Resistance Thermometers by reference to it. By Hugh L. Callendar, M.A., Fellow of Trinity College, Cambridge, and E. H. Griffiths, M.A., of Sidney Sussex College, Cambridge 56 On the Generic Identity of Sceparnodon and Pkascolonus. By E. Lydekker, B.A. (Plate 1) .". 60 Contribution to the Study of the Vertebrate Liver. By Sheridan D616- pine, M.B., Edin 64 On certain Conditions that modify the Virulence of the Bacillus of Tubercle. By Arthur Eansome, M.D., F.E.S 66 List of Presents 73 No. 297. — January 8, 1891. On the Minute Structure of the Muscle-Columns or Sarcostyles which form the Wing Muscles of Insects. Preliminary Note. By E. A. Schafer, F.RS, \ 76 On the Minute Structure of Striped Muscle, with Special Reference to a New Method of Investigation by means of " Impressions" stamped in Collodion. By John Berry Haycraft, M.D., D.Sc., F.E.S.E 76 On the Eeflection and Refraction of Light at the Surface of a Magnetised Medium. By A. B. Basset, M.A., F.RS * 76 Further Contributions to the Metallurgy of Bismuth. By Edward Matthey, F.S.A., F.C.S., Assoc. Eoy. Sch. Mines 78 List of Presents.... , 80 IV January 15, 1891. P*«e On the Rate of Prorogation of the Luminous Discharge of Electricity through a Rarefied Gas. By J. J. Thomson, M.A., F.RS.., Cavendish ProfesBor-of'Experimental Physics, Cambridge 84 Note on the Present State of the Theory of Thin Elastic Sheik By A. E. H. Love, M.A., St John's College, Cambridge 100 On the Chemical Phenomena of Human Respiration while Air is being re-breathed in a closed Vessel. By William Marcet, M.D., F.R.S 103 List of Presents „ 117 January 22, 1891. < >n the Unsymmetrical Distribution of Terrestrial Magnetism. Bv Henry Wilde, F.RS „ _ * 120 The Passive State of-Iron and Steel. Part II. By Thos. Andrews, K.R.SS.L. and E., M.IustC.E '. 120 List of Preseuts _ \-l~, January 29, 1891. BAKKRIAX LECTURE.— On Tidal Prediction. By G. H. Darwin, F.RS., Plumian Professor and Fellow of Trinity College, Cambridge 130 List of Presents 133 No. 298.— February 5, 1891. Chi the Chief Line in the Spectrum of the Nebulae. By J. Norman Lockyer, F.H:S „ 136 On the Chief Line in the Spectrum of the Nebulae. A Reply. By William Huggins, D.C.L., LL.D., F.RS 136 On a Membrane lining the Fossa Patellaris of the Corpus Vitreum. By T. P. Anderson Stuart, M.D., Professor of Physiology in the University of Sydney, N.S.W. ..„ ' .... 137 On the Connexion between the Suspensory Ligament of the Crystalline Lens and the Lens Capsule. By T. P. Anderson Stuart, M.D., Pro- fessor of Physiology in the University of Sydney, N.S.W 141 A simple Mode of Demonstrating how the Form of the Thorax is partly determined by Gravitation. By T. P. Anderson Stuart, M.D., Pro- fessor of Physiology in the University of Sydney, N.S.W 14:* On the Physiology of Asphyxia, and on the Anaesthetic Action of Pure Nitrogen. By Geerge Johnson, M.D., F.R.S _ 144 List of Presents 150 February 12, 1891. On the Organisation of the Fossil Plants of the Coal-measures. Part XVIII. By Professor W. C. Williamson, LL.D., F.R.S., Professor of Botany in the Owens College, Manchester 1">4 On certain Ternary Alloys. Part III. Alloys of Bismuth, Zinc, and Tin, and of Bismuth, Zinc, and Silver. By C. R. Alder Wright, D.Sc., F.R.S., Lecturer on Chemistry and Physics in St Mary's Hospital Medical School, and C. Thompson, F.I.C., F.C.S 156 On certain Ternary Alloys. Part IV. On a Method of Graphical Representation (suggested by Sir G. G. Stokes) of the way in which certain Fused Mixtures of Three Metals divide themselves into Two different Ternary Alloys ; with further Experiments suggested thereby. By C. R. Alder Wright, D.Sc., F.R.S., Lecturer on Che- mistry and Physics in St. Mary's Hospital Medical School ; C. Thompson, F.I.C., F.C.S. ; and J. T. Leon, B.Sc., F.C.S., Assistant Lecturer on Physics and Demonstrator of Chemistry in St. Mary's Hospital Medical School „, 174 On the Structure of Amreboid Protoplasm, with a Comparison between the Nature of the Contractile Process in Amoeboid Cells and in Mus- cular Tissue, and a Suggestion regarding the Mechanism of Ciliary Action. By E. A. Schafer, F.E.S 193 On the Demonstration by Staining of the Pathogenic Fungus of Malaria, its Artificial Cultivation, and the Results of Inoculation of the same. By Surgeon J. Fenton -Evans, M.B 199 List of Presents..., . 200 February 19, 1891. On the Sensitiveness of the Bridge Method in its Application to Periodic Electric Currents. By Lord Rayleigh, Sec. R.S 203 On the Influence of Pressure on the Spectra of Flames. By G. D. Liveing, M.A., F.R.S., Professor of Chemistry, and J. Dewar, M.A., F.R.S., Jacksonian Professor, University of Cambridge „ 217 On the Focometry of Lenses and Lens-Combinations, and on a new Foco- meter. By Silvanus P. Thompson, D.Sc., B.A., Professor of Physics in the City and Guilds Technical College, >Finsbury 225 The Numerical Registration of Colour. Preliminary Note. By Captain W. de W. Abney, C.B., R.E., D.C.L., F.R.S 227 List of Presents.... .. 233 February 26, 1891, CROONIAN LECTURE. — On the Mammalian Nervous System ; its Functions and their Localisation determined by an Electrical Method, By .Francis Gotch, Hon. M.A., Oxford, and Victor Horsley, B.S., F.R.S., &c. (From the Physiological Laboratory, Oxford) 235 List of Presents .. 24C The Rupture of Steel by 'Longitudinal Stress. By Chavles A. Carus- Wilson. (Plates 2 and 3) 243 Photometric Observations of the Sun and Sky. By William Brennand.... 255 No. 299. On the Minute Structure of the Muscle-Columns or Sarcostyles which form the Wing-Muscles of Insects. Preliminary Note. By E. A. Schafer, F.R.S. (Plates 4 and 5) 280 VI PMT* Chi the Minute Structure of Striped Muscle, with Special Reference to a New Method of Investigation, by means or " Impressions " stamped in Collodion. By John Berry Haycraft, M.D., D.Sc., F.R.S.E. (Plate 6) 287 March 5, 1891. List of Candidates „ .. _ 304 Some Suggestions regarding Solutions. By William Ramsay, Ph.D., F.RS., Professor of Chemistry in University College, London 305 Preliminary Notice of a New Form of Excretory Organs in an Oligo- ciuetous Annelid. By Frank E. Beddard, M.A., Prosector of the Zoological Society .". 308 ( 'oiitributions to the Study of the Connexion between Chemical Consti- tution and Physiological Action. Part II. By T. Lander Brunton, M.D., F.R.S., and J. Theodore Cash, M.D., F.RS, 311 The Physiological Action of the Paraffinic Nitrites considered in con- nexion with their Chemical Constitution. Part I. The Action of the Parattinic Nitrites on Blood Pressure. By J. Theodore Cash, M.D., F.R.S., Professor of Materia Medica in the University of Aber- deen, and Wyndham R. Dunstan, M.A., Professor of Chemistry to the Pharmaceutical Society of Great Britain 314 Some Points in the Structure and Development of Dentine. By J, Howard Mummery 319 List of Presents — „ .. 321 Marc\ 12, .1891. On the Plasticity of an Ice Crystal. By the late J. C. McCennel, M.A. 323 On the Effect of Temperature upon the Refractive Index of certain Liquids. By W. Cassie, M.A _ 343 On the Bisulphite Compounds of Alizarin-blue and Coanilin as Sen- sitisers for Rays of Low Refrangibility. By George Higgs 345 On certain Properties of Metals considered in Relation to the Periodic Law. By W. C. Roberta-Austen, C.B., F.R.S 347 List of Presents ,.. 357 March 19, 1891. On the Uterine Villiform Papillse of Pteroplntcea micrura, and their Relation to the Embryo, being Natural History Notes from H.M. Indian Marine Survey Steamer " Investigator," Commander R F. Hoskyn, RN., Commanding. No. 22. By J. Wood-Mason, Superin- tendent of the Indian Museum and Professor of Comparative Anatomy in the Medical College of Bengal, and A. Alcock, M.B., Surgeon I.M.S., Surgeon-Naturalist to the Survey „ ^. 359 A New Test for Albumin and other Proteids. By John A. Mac William, M.D., Professor of the Institutes of Medicine in the University of Aberdeen *...... 368 The Influence of Oxygen on the Formation of Ptomaines. By William Hunter, M.D., F.R.S.E .*.... 376 Vll Page Some Measures of Young's Modulus for Crystals, &c. By A. Mallock.... 380 On the Chief Line in the Spectrum of the Nebulae. By James E. Keeler, Astronomer of the Lick Observatory 399 List of Presents.... ... 403 No. 300.— April 9, 1891. On Electrostatic Screening by Gratings, Nets, or Perforated Sheets of Conducting Material. By Sir William Thomson, D.C.L., P.R.S 405 On Variational Electric and Magnetic Screening. By Sir William Thomson, P.E.S 418 The Measurement of the Power given by any Electric Current to any Circuit. By W. E. Ayrton, F.R.S., Professor of Applied Physics in the City and Guilds of London Institute, and W. E. Sumpner, D.Sc 424 On Galvano-Hysteresis. (Preliminary Notice.) By Silvanus P. Thomp- son, D.Sc., B.A., Professor of Physics in the City and Guilds Technical College, Finsbury 439 List of Presents.... .. 440 April 16, 1891. On the Causes which produce the Phenomena of New Stars. By J. Norman Lockyer, F.R.S 443 An Attempt to determine the Adiabatic Relations of Ethyl Oxide. Part I. Gaseous Ether. By W. Ramsay, F.R.S., Professor of Che- mistry in University College, London, and E. P. Perman, B.Sc 447 On the Physical Characters of the Lines in the Spark Spectra of the Elements. By W. N. Hartley, F.R.S., Professor of Chemistry, Royal College of Science, Dublin 448 List of Presents.... 452 April 23, 1891. Contributions to the Chemical Bacteriology of Sewage. By Sir Henry E. Roscoe, F.R.S., D.C.L., LL.D., and Joseph Lunt, B.Sc., F.C.S 455 Note on the Instability of India-rubber Tubes and Balloons when dis- tended by Fluid Pressure. By A. Mallock 458 List of Presents . 463 April 30, 1891. Cloud Photography conducted under the Meteorological Council at the Kew Observatory. By Lieutenant-General R. Strachey, R.E., F.R.S., and G. M. Whipple, Superintendent of the Observatory 467 The Passive State of Iron and Steel. Part III. By Thos. Andrews, F.R.SS.L. and E., M.Inst.C.E 481 On the Demonstration of the Presence of Iron in Chromatin by Micro- chemical Methods. By A. B. Macallum, M.B., Ph.D 488 List of Presents . ....: 489 vm No. 301.— May 14, 1891. Page On the Examination for Colour of Cases of Tobacco Scotoma, and of Abnormal Colour Blindness. By Captain W. de W. Abney, C.B., RE., D.C.L., F.R.S 491 On the Limit of Visibility of the different Rays of the Spectrum. Pre- liminary Note. By Captain W. de W. Abney, C.B., RE., D.C.L., F.RS.~ 509 Researches on the Structure, Organisation, and Classification of the Fossil Reptilia. VII. Further Observations on Pareiataunu. By H. G. Seeley, F.R.S., Professor of Geography in King's College, London 518 On the Theory of Electrodynamics. By J. Larmor, Fellow of St. John's College, Cambridge 521 List of Presents 536 May 28, 1891. On the Bases (Organic) in the Juice of Flesh. Part I. By George Stil- lingfleet Johnson, M.RC.S., F.C.S., F.I.C 538 Note on Dr. Fen ton Evans' Paper on the Pathogenic Fungus of Malaria. By W. T. Thiselton Dyer, M.A., C.M.G., F.RS 539 Method of Indexing Finger-Marks. By Francis Galton, F.R.S 540 On the Anatomy and Physiology of Protopterus anna-tent. By W. N. Parker, Ph.D., F.Z.S., Professor of Biology in University College, Cardiff 549 On the Constitution of the Terpenes, Camphors, and Camphor Acids. By J. Norman Collie, M.D 554 List of Presents 554 Plates 7 and 8 (with explanations), illustrating Messrs. Wood-Mason and Alcock's paper (No. 299, p. 359). Obituary Notices : — Alexander John Ellis i John Marshall - iv Frans Cornelis Donders (with a portrait) vii John Casey xxiv Index . . x.\ vi PROCEEDINGS OF THE ROYAL SOCIETY December 11, 1890. Sir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. The President announced that he had appointed as Vice-Presi- dents— The Treasurer. The Astronomer Royal. Professor Alfred Newton. Sir G. Gabriel Stokes. Lieut.- General Strachey. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read : — I. " On Ellipsoidal Harmonics." By W. D. NIVEN, F.R.S. Received October 23, 1890. (Abstract.) In the paper, of which the following is an abstract containing statements of the principal results arrived at, an attempt has been made to develop the subject of ellipsoidal harmonics from their expressions in Cartesian coordinates. The harmonics of the ellipsoid of three unequal axes are first investigated, as being the most readily dealt with on account of symmetry and, afterwards, those of the prolate and oblate spheroids are deduced as particular cases. 1. It has been found convenient to discuss separately the forms which are respectively suitable to the inside and outside of the ellipsoid, the former being taken first — VOL. XLIX. B Mr. W. D. Niven. [Dec. 11, , denote the expressions comprised under G = (1, x, y, z, yz, zx, xy, xyz) Ql ---- 0*, where any of the quantities inside the brackets is the multiplier of the product of the 9's outside, will satisfy Laplace's equation, provided n equations of the form P g r | 4 4 =0 are satisfied, where p, q, r are respectively 3 or 1 according as G does or does not contain x, y, z as factors. 2. If Kr denote _£ — +_J'l_+_! — , so that Kr = Qr+l, then, in a2 + 0, 62-r0r c* + 0, like manner, the expressions comprised under H = (1, a% y, z, yz, zx, xy, xyz) K^ ---- K, will satisfy Laplace's equation for precisely the same values of 6 as in §1, and it may be shown that there are 2» + l independent conjugate H-harmonics of any degree n. 3. The function H is a spherical harmonic. Suppose it is of the nth degree and of order a, and let it be denoted by H,,'. The corre- sponding ellipsoidal harmonic, i.e., for the same values of 0, may be denoted by G,*, and it may be shown that Gn* and H,,' are con- nected by the relation D2r 1 4.C_iy _ " __ L IH* ' 2->!(2n-l)(2n-3)....(2n-2r+ir J where D* = a2 ~ + b* ^-+c3 ?L ox oy Oz 4. Let iryc be any point on the surface of the ellipsoid and x'y'z' the corresponding point on a concentric sphere of unit radius, so that x = ax', y = by', z = «r', then will Qr (x, y, 2) = -0rKr («', y', *'), and Q(x,y,z) = (1, a, 6, . . . . , a6c) (-^) (-02). ... H («',!/', 2')- By means of thase relations any function/ (x, y, z) or/ (ax1, by', cz') 1890.] On Ellipsoidal Harmonics. can be first expressed in terms of spherical harmonics in x', y', z', by Laplace's expansion, and then in ellipsoidal harmonics in x, y, z. A sei'ies of ellipsoidal harmonics can thus be found having an arbitrary value at the surface of the ellipsoid. 5. External Harmonics. — The leading proposition in this part of the subject is as follows : — If TrabcVn denote the potential at an outside point xyz due to a solid ellipsoid, whose semi-axes are a, 6, c, such that the density at any internal point fgli is of the form f g* l *co&20 J The expression cannot be integrated ; but, by using a formula of reduction in series, it gives — 1890.] Photometric Observations of the Sun and Sky. Total intensity of the gore on the paper at 0 which is the formula I have used in numerical computations. It is the numerical value in the column " Sky alone " in Table B, which is thus brought into direct verification with ia observed by the mitrailleuse. Arts. 25 — 29 show that the integral (K) taken for the whole visible hemisphere is 2ia (ir sin a + 2 COS a) (Q). This is the whole chemical action of the hemisphere resolved on the horizontal plane, which was one of the quantities observed by Sir H. Roscoe. 30. Deals with any suspicion that may arise that the law of cosecants may have been assumed, the fact being that the law was arrived at, by experiment simply, more than twenty-two years ago, &c. 31. Applies the equation (Y) to determine ia for the altitudes given by Sir H. Roscoe in his table showing the total chemical action of diffuse daylight (i.e., of the whole sky, the sun being stopped off) on horizontally exposed paper (' Phil. Trans.,' 1870, p. 314). These values are tabulated with corresponding values of ia calculated by formula in (24) from the Dacca Table B, forming together Table E. 32. As a first approximation from Table E, it would appear that Sir H. Boscoe's unit of chemical action is if of the Dacca candle unit- 10 Photometric Observations of the Sun and Sky. [Dec. 11, Table E. 1 2 3 4 5 Values in col. 4 Diffused »'a to brought up for Sun's altitude. daylight of calculated calculated from comparison Koocoe. from col. 2. Dacca Table B. with those in col. 3. o / 9 51 0-038 0-0076 0-0068 0-009 19 41 0-062 0-0105 0-0107 0-0141 31 14 O'lOO 0-0150 0 -01 18 0 -0156 42 13 0-115 0-0160 0-0121 0 0160 53 9 0-126 0 -0170 0 -0121 0 -0160 61 8 0-132 0-0177 0-0120 0 -0159 64 14 0-138 0-0187 0-0120 0-0159 Twilight. 33. The resultant chemical action of the sky on a horizontally exposed piece of paper, the sun's altitude being «, is found = (2»- sin at + 4 cos *)t«. This vanishes when 2ir sin a. + 4 COS at = 0, i.e., when en- tan * = — — , TT * = -32° 29'. This gives an absolute value for twilight, supposing daylight to cease when the diffused daylight of Roscoe entirely vanishes. The extreme limit at which twilight has been certainly observed is when the sun is 24° below the horizon ; at which time the formula ta(2jr sin a + 4 cos *) would show the chemical action of diffuse day- light to be only -^ of what it was just after sunset. In other words, the formula (2ir sin a. + 4 cos «)ta gives a very good agreement with the observed duration of twilight. 34. Taking as co-ordinate planes the plane of symmetry, the plane of minimum intensity, and the plane through the sun at right angles to these (which last I call the plane of the sun's altitude), it is found (as a corollary in Article 34) that [U], [V], [W], representing the total chemical effect of the sky, resolved on these co-ordinate planes. This suggested the construction of the octant actinometer, which 1890.] On the Validity of Person's Absolute Zero. 11 requires only a quarter of the visible sky to be clear for observation, and gives the value of ia directly, requiring no calculation or reduc- tion. It possesses, moreover, the great advantage of not taking in the low band of sky near the horizon, and thus avoiding a principal element of uncertainty in other observations. 35. The octant actinometer consists of three quadrantal planes, MOS, M01, and IOS, joined at their edges so as to form a hollow trihedral, and mounted so that one of the edges, OS, can be brought to point to the sun ; the plane MOI will then coincide with the plane of minimum intensity. The instrument has another adjustment, by which it can turn round OS as an axis, and if one of the planes MOS, IOS be brought to coincide with the plane of sym- metry, the other will coincide with the plane of the sun's altitude. I take a small square of sensitised paper, and cut it along CO ; then slipping the part COB under AOC, so that B coincides at C, it forms a- rectangular trihedral of paper. This is placed in a small exposure trihedral of cardboai-d, and covered by a thin metal trihedral in the trihedral of the octant (I make several of these trihedrals of sensi- tised paper, so as in the field to take quickly a series of observations ; the trihedral of paper is, of course, carefully covered till the instru- ment is in adjustment) ; exposed to the action of the sky for (say) thirty seconds, the readings 011 the planes MOS and IOS will be each 30t'a, and that on the plane MOI will be 30 . \ TT ia. ,36. Gives in Table F the observations with the octant in August last. 37. Discussion regarding the most useful method of resolution of the sky and sun. III. " Determinations of the Heat Capacity and Heat of Fusion of some Substances to test the Validity of Person's Abso- lute Zero." By SPENCER UMFREVILLE PICKERING, M.A., F.R.S. Received November 6, 1890. The relations existing between the heat of fusion of a substance and its heat capacity in the liquid and solid condition were demon- strated by Person, in 1847 ('Ann. Chim. Phys.' (3), vol. 21, p. 315). He showed that the heat of fusion must diminish as the temperature 12 Prof. S. U. Pickering. Determinations to test [Dec. 11, is lowered, the decrease per degree being equal to the difference between the heat capacities of the liquid and solid, and that, therefore, there most be a certain temperature at which the heat of fusion will be nil, this temperature being given by t — — — , in which t is the melting u — c point of the substance, I its heat of fusion at t, and C and c its heat capacity in the liquid and solid conditions respectively. At this tem- perature a liquid could not freeze, since there would be no difference between it and the solid, and Person argued that there would then be no heat at all in it, and that this temperature was the absolute zero. He then made determinations with various substances, which tended to show that this temperature was the same for all bodies, and was situated at -160°C. The analogy between this zero and that deduced for gases is, how- ever, very imperfect ; the total heat in a gas is measured by its tem- perature reckoned from — 273°, whereas it is only the difference between the total heat in a liquid and solid that is measured by its tem- perature reckoned from — 160°, and, instead of considering the latter as the absolute zero, it is preferable to regard it as the critical tem- perature for the solid-liquid conditions (see ' Chem. Soc. Trans.,' 1889, p. 32) ; and indeed, since we have now succeeded in obtaining liquids at temperatures below — 160°, it is quite impossible to regard — 160° as the absolute zero, or to believe that the heat capacities of all bodies would indicate this same temperature for that of no solidification. Guldberg (' Bidrag til Agarnernes Molekylar Theorie,' ch. v, p. 484) has defined the critical point of the solid-liquid states as that at which the volumes of the liquid and solid are identical, and at which the heat of fusion is nil, a certain pressure, as well as a certain tem- perature, being required to fulfil these conditions. It appears to me, however, that the question of pressure may practically be left out of consideration; pressure will, of course, affect the temperature m question, but to such a small extent that the ordinary atmospheric pressure, under which the data necessary for the calculations are obtained, may be regarded as nil, and it also appears to me that the definition depending on the heat of fusion being nil includes the idea of equal volumes, for it seems hardly possible to conceive two con- ditions of the same substance, each possessing the same kinetic and potential energy, which could yet differ from each other in volume or any other property. The analogy, however, between this temperature and the critical temperature for the liquid gaseous conditions is at best but an imper- fect one. If we start with a crystalline solid below this temperature and heat it, it could never pass by insensible degrees into a liquid ; the molecules in a crystal possess a definite arrangement, those of a liquid an indefinite arrangement, and, between these two, no inter- 1890.] the Validity of Persons Absolute Zero. 1& mediate state appears possible ; on the other hand, when we start with a liquid and cool it, it becomes in many cases (see ' Chem. Soc. Trans.,' 1890, p. 340) so viscous that even at —80° to —100° it can scarcely be termed a liquid, and by further cooling it would probably become so firm that it would be regarded as a solid. This affords a striking illustration of what may be meant by the gradual passage of a liquid into a solid, but the solid thus obtained would evidently not be identical with the crystallised solid, nor could it be obtained by heating the crystals from a lower temperature ; as the data on which the calculations are based do not refer to this solid but to the crystalline one, I think it preferable to avoid the use of " critical tem- perature," and to term that given by the equation t— — the "tern* w — G perature of no crystallisation." For the purpose of extending the applications of a law governing the freezing points of solutions which I have lately propounded (' Chem. Soc. Proc.,' 1889, p. 149), it was necessary to determine this temperature in certain cases. The present communication con- tains the details of these determinations, and they afford evidence- that it is not a constant for all bodies, as Person imagined. The values which Person obtained with various substances were as- follows : — * Water -159°7t Phosphorus — 151°7 Sulphur -160°-3 Sodium nitrate — 156°'7 Potassium nitrate — 170°'9 Hexahydrate of calcium chloride .. — 165°'3 Dodecahydrate of sodium phosphate — 161°'0 Potassium and sodium nitrate .... — 161°'0 The concordance of these values is certainly very striking, espe- cially when the diversity of the substance examined and the difficulties of the determinations are considered ; but a closer examination of the results cannot fail to suggest that the concordance must in some instances have been accidental. The difference between the heat capacities of the liquid and solid, C— -c, is often very small, and even ordinary experimental errors in either of the quantities would make a large difference in the results, while in some of Person's determina- tions the experimental errors must have been of more than ordinary magnitude, for these determinations occasionally lasted between one and two hours, during which time the loss by cooling must have been very * 'Ann. Chim. Phys.' (3), yol. 21, p. 295 ; vol. 24, p. 129 ; and vol. 27, p. 250. f Taking Person's later determinations of the heat of fusion of water — 8CKV (' Ann. Chim. Phys.' (3), yol. 39, p. 73), this value becomes -16l°'3. 14 Prof. S. U. Pickering. Determinations to test [Dec. 11, large. Special sources of error and uncertainty might be pointed oat in each particular case (except that of water, perhaps), but there is one fatal objection to all Person's results, namely, that the heat capacity of both solids and liquids varies considerably with the temperature, and that he mnde his determinations at any temperature which hap- pened to be most convenient, that, for instance, at which the heat capacity of the solid was determined varying between 11° and 280° below its melting point. One case will be sufficient to illustrate the effect of this. With solid phosphorus determinations have been made by Kopp ('Liebig's Annalen,' Snppl. 3, p. 1) and Regnault ('Ann. Chim. Phys.,' vol. 73, j>. 56 ; and (3) vol. 26, p. 269), and the latter, at any rate, must com- mand as much confidence as Person's (indeed Person adopts some of Regnault's determinations with this substance) ; these results are — c = 0-2020 at ( + 36° to + 13° = ) + 24°- 5 C. . . Kopp, r = 0-1895,, ( + 7°'15,, + 30°-21 = ) + 18°-68 .. Regnault, c = 0-1783,, (-21° „ + 7° =)- 7° .. Person, c = 0-1699 „ (-77°-75,, +10° =)-33°-88 .. Regnault, and, taken in their order, they give —1969°, —292°, —152°, and 102° for the temperature of no crystallisation,* which results clearly show that no value can be attached to Person's figure, — 152°. Person's and Regnault's results lie in a fairly straight line which gives c = 0*1979 at the fusing point, and — 719° as the temperature of no crystallisation, but it is impossible to accept even this value, as there are not sufficient data for calculating the heat capacity of the liquid at the fusing point. C, c, and I should evidently be determined at the same temperature, and this temperature must necessarily be that of fusion (f), but, inas- much as the heat capacities near this temperature may be abnormally high owing to the fusion or solidi6cation being sometimes a gradual process, the determinations should not be made too near the fusing point,t and the only means of ascertaining their true value at this point is to determine them at several different temperatures, and from the rate of change thus obtained to calculate their value at the fusing point itself. This method has been adopted in the present work. • C = O2045 (98° to 48°), I = 5'034, and t = 44°'2. t The values obtained by Person for beeswax afford a striking instance in point ; from — 9° to + 50° the heat capacity of this solid increases from 0'43 to 1'72, exceed- ing at this latter temperature that of the liquid (0'50) by a very large amount. Ice chows a similar increase, but in a much smaller degree (see Person, 'Ann. Chim. Phys.' (3), Tol. 30, p. 80). 1890.] the Validity of Person' 's Absolute Zero. 15 Substances Investigated. The substances investigated were sulphuric acid, the monohydrate of sulphuric acid, the tetrahydrate of calcium nitrate, benzene, and naphthalene, the last mentioned being the only one in which C, c, and I had been determined by previous investigators. The sulphuric acid was the same as that used in my determinations of the freezing points of this substance (' Chem. Soc. Trans.,' 1890, p. 337), the stock acid having been diluted by the addition of ice so as to contain exactly 100, and, for the monohydrate, 84-488, per cent. H2SOi. The calcium nitrate was prepared by repeated crystallisation ; the percentage of anhydrous salt in the fused crystals having been de- termined by evaporation and heating at 250°, the excess of water which the fused salt was found to contain was driven off by a gentle heat. The melted salt will remain liquid at ordinary temperatures for many days, although its solidifying point is 42°'4. The naphthalene and benzene were special preparations made by Messrs. Kahlbaum : repeated crystallisation was not found to alter the melting point of either to any appreciable extent. Method Employed. The substance was placed in a cylindrical platinum bottle measur- ing 9x2 cm., and holding about 30 c.c. Its mouth was closed by a. caoutchouc stopper, through which passed a thermometer with a very narrow bulb, long enough to extend from the top to the bottom of the bottle, thereby giving the mean temperature of the contents more accurately than an instrument with a short bulb would have done. The bottle was placed in a double test tube, and the latter in a double bath containing warm water or a freezing mixture, as the case might be. After the bottle had attained the required temperature, and this had remained constant for some time, it was removed from the test tubes and plunged into the calori- meter, an operation which occupied only two or three seconds. To prevent the deposition of hoar-frost on the bottle while it was being cooled, the inner test tube in which it was placed had a bulb blown at the bottom, in which was kept some sulphuric acid. The calorimeter contained either 600 or 1800 c.c. of water, the quantity being adjusted so that the rise or fall of the temperature in it was about 1°, the smallness of the change being favourable to the accuracy of the de- termination by rendering the loss of cooling, or gain by heating, very small. This loss or gain was estimated by determining the rate of cooling at the initial and final temperatures, both thermometers being read at intervals of one minute, and having been compared with each other before the determinations. The rate of cooling during the time when the temperature was rising or falling was taken to be the mean of 16 Prof. S. U. Pickering. Determinations to test [Dec. 11, that at the initial and final temperatures ; it was generally very small, since the temperature of the air was kept at a point such that there was heating at the initial temperature, and cooling at the final tem- perature, or vice versd. The time occupied in obtaining almost identical temperatures in the bottle and calorimeter varied between two and twenty minutes, the whole determinations, including the interval allowed for determining the two rates of cooling, occupying fifteen to forty-five minutes. Such a duration militates very much against the accuracy of the results. The calorimetric thermometer read by estimation (0'05 mm.) to 0°'0005 ; the stirring apparatus and other appliances were the same as those described elsewhere (' Chem. Soc. Trans.,' 1887, p. 293). The water equivalent of the platinum bottle and its thermometer was ascertained by direct experiment to be 2*223 grams. The last men- tioned thermometer possessed a range of 30°, one estimation figure being equivalent to 0°'01, and, as the rise or fall measured sometimes exceeded 30°, it was in such cases set so as to register the initial temperatures of the bottle, the final temperature of this being taken to be the same as that of the calorimetric water, previous determina- tions having shown that the two temperatures were identical within the reading error of the instruments when this rate of cooling became constant. The temperature of the calorimeter was generally about 18°. The determinations were all made in duplicate. The mean error of a single observation was found to be about 0'8 per cent, of the total rise or fall measured ; this corresponds to an error of 0°'0075 in the alteration of temperature registered in the calorimeter, or 00>22 in that registered in the bottle; considering the long duration of the determinations and the magnitude of the total correction for cooling which had to be applied, such an error must, I think, be regarded as small. In many cases the error in the heat capacity found is the same as that in the rise or fall measured, i.e., 0'8 per cent., of its value, or, on the average, 0'0032 of the heat capacity per gram ; in other cases it is much greater, for the heat evolved sometimes in- cluded the heat of fusion, and, after subtracting this, the whole error remained concentrated in the smaller quantity, which represented the beat capacity. In some cases, again, the heat capacity for a given interval had to be found by taking the difference between two different determinations, and in such cases the error was greater. Results Obtained. The experimental results are collected in Tables I to X, pp. 23 — 32. In these w is the weight of substance taken, r the rise or fall mea- sured in the calorimeter, t and t' the initial and final temperatures of 1890.] the Validity of Persons Absolute Zero. 17 the substance in degrees centigrade (the latter being identical with that of the calorimeter) ; " Cal." represents the total calories evolved or absorbed, and " Cal. per 1 gram " those evolved or absorbed per unit weight of substance, a deduction having been made for that portion attributable to the bottle and its thermometer, namely 2'223 X t — t' ; C or c is the heat capacity deduced, the range of temperature and mean temperature to which it applies being given under T, measured in degrees above or below the melting point of the substance iu question. Such results as apply to ranges of temperature partially embraced in other determinations are enclosed in square brackets, and are used for deducing those values opposite to which no experimental data appear. The two values given for the heat capacity at Or (the freezing point of the substance) are those which would be deduced from the determinations at the two higher and two lower temperatures respectively. Where the determinations include the heat of fusion the differences between the individual experiments (not the means) are used in calculating the heat capacity ; those determinations are divided into two series, A and B (see Table II), each of which is differentiated separately (Table II continued), and the means of these two series of values taken ; then the experiments A and B are taken together alternately, and the two other series thus obtained give another series of mean results, the mean of these two means being tinally taken. The heat of fusion was determined from those experi- ments in which the initial temperature was nearest to the temperature of fusion. The general results are collected in Table A, where those in the first five lines give the values for 1 gram of substance, and those in the second five the values for a gram-molecular proportion of it. Details. Before discussing the general results, the following details may be noticed : — Sulphuric Acid. — The value found for the liquid at 19°'53 seems to be rather too high, and this makes the value deduced for 26°'74 too high, and that for 41°'25 too low. The value for 0° has here been deduced diagrammatically, the probable error (Table A) being deter- mined from the errors of the duplicate determinations. Both the values for the solid at the initial temperature of — 16°'8 appeared somewhat anomalous, and they were consequently omitted in the calculations. In taking the mean value for T = 0°, a double weight has been assigned to the value deduced from the determinations at the two higher tem- peratures. The probable error (given in Table A) in this, and most other cases, has been deduced in the ordinary way from those two values. The heat capacities of neither the solid nor the liquid show any signs of an abnormal increase as we approach the melting point. VOL. XLIX. C Prof. S. U. Pickering. Determinations to test [Dec. 11, ta II t> f f» ® 9 I fe i i B S • M 1 1 1 1 4 • 1 u *• a * • • • •H -M -H -H S S S S K M w • o. rf d f ? •* ? r 0 00 N 0> <0 u U 2; '-•>"' g — ?j ?> ; O O O 0 9523; • S S 2 II § o ot o» «o »o « N — PI O o o o o o S S S S S 2 3 S S -0 Heat of fvu •2 oo 3 .0 » 5 -* o 01 n j> o» •» to •* •* o> « o e» CI §J o f~~ 1_" 1 Efe o> M o n 8 I i | • b b 6 o b E 2 2 3 3 b b — b fi N -H -H -H -H -H •H -H -H -H -H •d 1 • II X HJ « jO S JJ i i 1 s i Heat capaci 0 O 0 0 0 + + + + + — « « w o R & 5 • 8 ? f f f I 0 0 O 0 0 0 0 0 o O + + -t- + + g S S 2 K S S 2 » S 1, ii 8 I I S I 00 OS t- IO -f — 0 — •* 0 b b b n o 2 0 EH -H -H -H -H -H -H -H -H -H -H 1- li o' II K ! to oo o o Z K 9 bob b + + 1 + O O O •* t~ 1 00 jj 0 i i i I b b o b + + 1 + 8 S 2 S S i « ^ 0 •* CO b b b b b g S g 5 § J f 5 3 a 3 j 2 S Subitance. 1- | _, s S 9 • « I ^ e • 8 ° u- § ! i 1 1 § 1 1 - i l_l_S_5_^ ! 2 n s V 2- : s S o 5 =2 ^ '1 =I J " ^ C O 65 N?

—992° (Regnault) These being the only results available for testing Person's view, that the temperature of no crystallisation is — 160° for all substances, we must certainly conclude that this view has not yet been established. • Taking the other ralue for c deducible from Alluard's results (0 3642), we get -583°. the Validity of Persons Absolute Zero. 23 o CM CO o O O T .p E3 CO 13 a d H i — i i — i rH kra CO 00 ^P *O 00 CO lO O J> N fi. rH IO OS O O rH rH rH CO 00 00 00 O rH O 4. is> 333333 CO • OOoSoOrHlOlOCD |T}(COCDrHO500OOO[ I g& rH rH . rHNMS^XCDCO a o osooiocoosxoooeo |COCOT}(lOlOCDrHOO| | t> t^ oo oo oo oo os oo rHi— li— It— IrHrHrHrH d ^ ^ H;( OS V5 OS O rH •« >5Ocoeo5'^'CDCD il |cocOTj(T}.t>inio 1 1 OOOOOOrHrH s t> tO rH tO 1 « .Vs -1-? -°> c 1 t* "co "eo "oo kS i-O O ».O •3 24 Prof. S. U. Pickering. Determinations to test [Dec. 11, Heat of fus -H CJ t^ 1 ' £ 1 1 1 1 1 1 1 1 1 1 t*t>-<— < i* 10 t— 'co o T a o O2 o CG •S H — L- c. C. — ^ ? i r: — 11 i-l 1-1 00 CO 1 1 1 1 1 1 COOiOiOOOOCM CO ^00 ^CO ^^ ^TO ' " ~- i •» i " O) •5 § eo -f 3; 1-1 X 00 o • • 1-1 co 1 1 1 - : : ^ 1 g 0 S Cl 71 71 b o o o v: 'r' CM 5i 1 O O a ^1 - « « tX) HJ o© o H CM c3 ?J bob »a e» t» CO O CM "11 t-t*co 1 1 1 1 1 1 cTgTtj -g^ B B B *" g 71 • f3 c? .2 1-1 N ^i . « 1 1 1 .2 •8 555 1 O CO -H i-H N -* i i r 522 g rl O5 « PQ " •* O CO S — 71 OS P "5 O O O O O O o Illlllll 00000000 t-< r-s S CO OS O ts» rH CO N i— i CO O US X5 03 bb o co co co x> o os i-H ffl CO CO SSI CO US (N rH O3 00 Q 00 ^ Cs CO co "i1 co "^ us us 0 t^ CO rH OS OS 00 00 CO US O5 t» CO rH rH US US CO CO 8 i> i^ oo oo oo oo i-H rH rH i-H i-H i-H Q us eo us IN t> os •^ CO 00 »O CD US eo us •* co co us %» eo CN eo CD rH g CO CO "^ "^ * oq o os co os -r> co i> QS co « os oo i-H OS CO O to us Prof. S. U. Pit-k i-rii i g. !>>t, THI! nations to test [Dec. 11, 02 •s •§ 02 •i H J3 ;3 $89 -< -^ f- N tt CO M I I I M I I CMININNCMCvllNCOCO 1 1 1 1 1 I i 0 oo •-> oo i-i O CO t> CO C5 1 1 1 eo z -. -* i O) N O 71 ir'i 71 bob a J t-H 13 s bb H «p t^. c. ?7. ~* ~* IN (N IN OOO 1§ M CM IN O US CO 1^ N CO •* 717171 bob «P3 CO 13 OS C *» 7- 1 77 i 7 i TTT CO CO CO J TTT | « eo -H •i 77? | 333 g 777 •| 333 — ~ : ' vULJ, PQ 1-1 *l g ^\^\^ 171-71 ^1§2 « X IN CO 7) 71 71 « 53 IN ooo ooo 1 77 *-s^ III « y y | TTT i! § ^X3> jf "i» "3 1 1? .§333 E SIM 1 333 •*! l-l r-i >— ^«*-^ 1 7?? j CO S IN — 71 7-1 •-i ^ N 000 ooo 1890.] the Validity of Persons Absolute. Zero. o to fl s _d 'cS O «*H O CD i — i i — i O5 *>. X »o O5 =? «P rH Bg SSI X go X 1 1 + + + °o § & & co^ OO O5 lO CO O5 II O CO CO i-H *J" O5 X CO Q t- IO C5 rH (M §5 -H — O ^5 G> O O O O d =0000000 L CD I 3" I-H IM rH N rH rH rH I-H IN IN CO CO t^ O X i-H -H* Tjl 00 J 10 U5 T}( T# (N CO 1 Hi X X X X O5 O d -* X O5 O CO O 1 x O5 sq i> O5 co i *• O5 rH O rH O rH eo •* «o co x x . X X X rH O> t~ sq o o CO CO O CC CO I 1 1 05 o 05 9 o o 1 1 O rH rH IM CO CO i , £ 3§ ^ | 1 ^ - • - • = 1 O IM ift 10 10 w O CC •s 0 II d, •w X CO if I t. -4 ep cp CO CO CO CO •fs S "^ 10 eo 0 I co eo 1 si O O Jig rH rH X IM •* X rH rH eo co * * CO CO 6 ID CD rH i-H 1 d ^ X X i-H rH d IM CO co eo 1 1 rH rH . (M rH t- X X X 1 0 0 i rH O £ Prof. S. U. Pickering. Determinations to test [Dec. 11, J5 § ^0 '5 *rt O •8 I I O CO t> o> ? £ i A •H V— ' t> - 5? Q « cp S3 a « CO 00 CD rH « •* iS 1 1 1 1 ^^\ ^"N X~S ^x II II II II 00 N 00 00 bee M o o H 3 f» |C 1 1 1 1 3232 8 O 0 N ® ^ S 9 X >L vL sL « i-l US t» O» t* ^5 t^ Oi ••* 00 CO CO 00 CD d 0 0 0 £ 0 ^•Q5frlQ5Q®>ftOO Tfcsoso^'gt^-'-H OQCt^^^^'I"^(N ,* 00 CO CO CO CO CO CO 00000000 h t ~ ^A -* ~ Q5 Oi S^ CC W X (M CO £** 00 00 90 1 -2 ™ 36 oo oo to ua co ko T-> I-H 3 * * * * -t- -t- — ; r .- ?i -M CC N rt t> •* O 3 1 00 t>. CO 00 US ** 1 C6 00 kffl U3 ift M ••* ^» eo eo ao os d °^ 1 00 00 l~ t> «O CO d SN CM 00 t* CO 0 M 95 CP C» I CC O IM -H O5 00 1 ^ i-H .-H O O CO OS •* •* W N 1 1 V N -• «O os oc ei Oi "^ CO ^* lO CO I So t* co us t~ 06 1 1 t» *>• 10 ui co ^r 1 O O O O «H iH 8 iH (M OS ,- — .-: | 1 s's^1' •5 r e 1890.] the Validity of Person's Absolute Zero. 29 ,0 oB EH Heat of fusion. o IM cp IO CO C5 OS CO CC O CO Tfi os »o CO -^ US co co co g" II a QQ. ?.*< PP O CO OS OJ OS -* CO o •* •* oo ^H oo 00 i-H >O Tfl t>- os eo os co o «i t- ^1? o£-§ 0 t- CO l> CO • O X ^ CO i— I TJ< (M »O O iO sr oo i> oo co o co K5 O 10 CD CD CO 00 t~ «O CO •"? CO "« 0 !M •* CO N O •£> •* CC -* CO OS CO t> O CO OS «5 iH OS r-l i-l CO CO *. oo oo os os oo oo d (M >O 00 »O Q OS os co eq r- o co co o -^ co i-i i> ^» i-H Tp •*? 1> 00 00 x oo oo os a os V ** (M 5*1 O i— ! d O i-l i-H 1— 1 I-H I-H i-H i— 1 d CO 00 •* CD 35 10 -* CO fM Tjf iO rjt O O 0 0 o ^ i.' \a eo co co op o OS O rH 0 i-H 0 O -^ Z> N CO %$3 eo IA i— I d O 0 0 0 a d 0 CQ. J^ § 30 Prof. S. U. Pickering. Determinations to test [Dec. 11, y rH rH S 00 rH •* Q CO CO »A 04 I 1 1 b i - CO O II ex, •M •^s 333 r 6

l> rH rH •d * * * * • t» T!< T? co i- r r o 3d t'^ ^ fr» O5 00 t> -X) CD CD O4 04 d o V, O4 O t^ rH co ao t^ co O rH t^ t^ 00 X l> t* rH rH I— I rH d CO CO CD 04 * CO 04 O 3) t^ t>» "^ co il Illl rH rH O O 8 §\Q .04 B B — cr M hH CD S rt El £ d, S w . r— i . >o e» t^ c t» t~ t- e» i E jj T T T T 04 CO kO A O ^ co p ^ ^f N « CD fH i-l f-l tO 3333 §3 S ? S iH WS CO «» CO iS CO d t^ •** oo CO >Q •0 0 O 0 -* O rH Ol CO I.O ** I*1 "? 7 "? 0 O O Oj O ooi"fco»o-Heo30 l.O >O i— 1 O5 t^ "* lO lO QO O f^ o *^ ^j c^ co 000=0000 •i Lg • - ^P t^ cz *f ^f co CO CO C- CO W JO 1 10 ?^ co co o oo 1 3^ >->-.-.-. r. /• rH ft —J * * -t- -t-« * CO Q «-i >A «O "5 10 co ci t» M -H 3 1 t* t>- US *» -^ •* - 04 O4 TIM the Validity of Persons Absolute Zero. o CO XI H " o o 2 O S go 1 1 eq (M IM co 1 1 1 1 1 1 kO IM £>» (M K°° ^~ KOJ o cq «q On the Validity of Persons Absolute Zero. [Dec. 11, OJCD ^ «« j< . »H ^ O) CO X w CO X «9 TO G i 1 7 i i 1 §TO ci i^ S « i TO TO i.-J t- »- •* •* CO TO N o b o b o o o pq jj tj — i d m os 1 "Si a" w b£) •«! 3 O O O O O MS ri ?i TO Vi ^ ^ f 7 1 — U 1 - 1 - if, •* 4 TO eo N O 0 O OO t-t N 3 C5 iH WS X TO TO S CO 0* i^ TO 00 ia 1-1 r! fi CO X >o r-4 n k 1 1 1 1 1 1 1 1 1 1 N II ii 3 ii II 05 N O O n n t- X f & n S x P " * ». * l! i-H iH N TO ^5 •* o 25 N S « 1 1 1 1 ' s, 1 1 l 1 1 fi 60 | 22 5 . . 3 P 333 S S | 32 ?SJ 3 S 3 P 3 •— i X •e *4 ta 2 2 S S 1-1 ^ i— i x •H « >UL J^ 1 1 PQ ""' v~^ ..i vLi J J X SS TO tO & » c o t— i 1 1 OO o A^ o o A o o b 0 *- _ b c' < w \ os -*> t- o »o i~- 01 oo. 53 — i V5 X •* f TO •v TO N cc co OOOO b ob o •* CJ 2 1-1 t- '." •r- 0 N — U5 t- 9 P « X S N TO « X i— i §5 TO 1 1 i 1 1 1 1 1 i 1 ^"v^*^ *~\ f~~ s~* • /•••^^••s. ^*^ >H-^ ^^ R 1 i n i | ii n n R 1 Sao m « x as "S o co X N N r. M P ».• • • • § *S i-H N N *° •- •* N N CO kO •a i i 1 I I S 1 7 1 "l T 1 53 3 3 3 1 S3 3 3 3 SOS O W ^H — O CO N cs •? 30 N ao P5 ^ X N N •« ~ + •H N & 'a ~ •* N iH i IX 7 2- >L «< ^L 7^ 1 ***• 1 T*~T t- TO 5 1« N X TO i 5< T i • TO 10 TO 00 CO . TO N 00 0 b b b b b O b 1890.] On Wolf and Rayefs Bright-Line Stars in Cygnus. 33 IV. " On Wolf and Ra jet's Bright-Line Stars in Cygmis." By WILLIAM HUGGINS, D.C.L., LL.D., F.R.S., and Mrs. HUGGINS. Received November 25. 1890. In 1867 MM. Wolf and Rayet discovered at the Paris Observatory three small stars in Cygnus, which in the spectroscope showed several bright lines upon a continuous spectrum.* All three stars have a very bright band in the blue part of the spectrum. These stars aro : — B.D. +35°, No. 4001. B.D. +35°, No. 4013. B.D. +36°, No. 3956. Their spectra were described in 1873, by Vogel, whose observations agree substantially with the original description given by Wolf and Rayet.f A more complete account of their spectra was given by Vogel in 1883, from observations at Vienna with the 27-inch refractor made by Sir Howard Grrubb. J Vogel's measures of the bright blue band place it in the star No. 3956 at from X 468 to X- 461, with a maximum at X 464; in the star No. 4013 with a maximum at the same place in the spectrum; while the corresponding blue band in the star No. 4001 has a con- siderably less refrangible position, commencing at X 470, reaching a maximum at X 468, and ending about X 465. These later measures, though they differ from his earlier ones, in ,so far as they show that the blue band has not an identical position iu all three stars, nevertheless support substantially his earlier obser- vations, which Vogel considered to show, contrary to the statements of Secchi, that the bright lines, including the blue band, were not due to carbon. In the diagram, Nos. 1, 2, and 3 show the positions of the bright bands in the three stars, according to Vogel's measures, relatively to the blue band of the hydrocarbon flame. Vogel's measures are : — End of the band. X465 X461 * ' Comptes Rendus,' vol. 65, 1867, p. 292. t ' Berichte K. Sachs. G-es. der Wiss.,' Dec., 1873, p. 556. J * Publicationen Astrophys. Observ. Potsdam,' vol. 4, No. 14, pp. 17 — 21. VOL. XLIX. ' D Star No. 4001 Beginning of the band. X470 Brightest part. X468 „ 4013 X464 3956.. X468 X464 34 Dr. and Mrs. Huggins. On Wolf ami [Dec. 11, 460 461 40L 463 4$4- 465 ** 447 4tfl 469 470 *7( 422 475 V4- 475" i . i . i . i . l . l . I . i . i . l . Vogdlfrj His diagram shows the band in No. 4018 to begin and end at about the same positions as in the star 3956. It has been stated recently that the bright blue band in all three stars is the carbon band in the blue, commencing near X 474 ;* and more recently, notwithstanding the difference of position, according to Vogel, of the band in one of the stars from that which it occupies in the other two of as much as X 0040, that direct comparisons showed * Professor Lockyer, in the Bakerian Lecture for 1888 ('Roy. Soc. Proc.,' vol. 44, p. 37), says of the star No. 4001 : — " The bright band with its maximum at A. 468 is the btight carbon fluting commencing at A 474 and extending towards the blue, with its maximum at 468, as photographed at Kensington." Of the star 4013 : — " The bright band in the blue at 473 is most probably the carbon band bright upon a faint continuous spectrum, this producing the absorp- tion from 486 to 473 " (loc. cit., p. 41). Of the star No. 3956: — " The bright band at 470 is the carbon band in the blue, commencing at 474, with its maximum at about 468, as observed and photographed at Kensington" (loc. cit., p. 43). See Vogel's measures for the band in this star, which are given in the text. Diagrams of the spectra of these stars are given at pp. 38, 40, and 41, based on Vogel's observations and his curves, which, on a slightly reduced scale, are placed at the bottom of the diagrams. The maximum of Voxel's curves is placed in all three diagrams at \ 468, and agrees in the diagrams with the carbon band, whereas Vogel's original curves and his measures place the maximum in the case of two of the stars- at A 464, beyond the carbon band. 1890.] Rayet's Bright-Line Stars in Cygnus. 35 an absolute coincidence of the band in all three stars with the bine band of a spirit-lamp flame.* As the presence or absence of carbon in these stars, as shown by the coincidence or otherwise of the bine band with that of the hydro- carbon flame, was of great importance to us in connexion with a wider investigation on which we are at work, we thought it necessary, after these recent statements as to the position of the band, to make direct comparisons of the spectra of these stars with that of the hydro- carbon flame under sufficiently large dispersion to enable us to deter- mine whether Vogel's measures are substantially correct, or whether they are so largely in error as the absolute coincidence of the band with the blue band of a spirit-lamp flame in the case of all three stars would show them to be. The obvious importance of making the observations with sufficient dispersion is supported by Yogel's own experience. With the small dispersion which he employed in his earlier observations in 1873, he did not detect the large difference of position, about X 0040, of the band in No. 4001, as compared with its position in the other two stars. On this point Vogel says, in his memoir of 1883 : — " Etwas abweichend ist nur die Auffassung der Lage der breiten hellen Bande im Blau, die bei den friiheren Messungen bei alien drei Sternen ubereinstimmt. . . . Bei den verhaltnissmassig geringen optischen Hiilfsmitteln, mit denen jene Messungen ausgefiihrt wurden, ist die Uebereinstimmung aber eine ganz iiberraschende " (Zoc. cit., p. 21). We observed the spectra of the stars successively, first with a direct vision prism of small dispersion, then with a spectroscope (A) con- taining one prism of 60°, and finally with a spectroscope (B) with two compound prisms, equal to about four prisms of 60° ; with the last-named instrument the comparisons with the hydrocarbon flame were made. A rapid preliminary comparison in the spectroscope (B) of the spectra of the three stars with the blue base of a Bunsen flame * Professor Lockyer, in a signed article in ' Nature ' (August 7, 1890, vol. 42,. p. 344), writes ; — " In the Bakerian Lecture for 1888 I gave a complete discussion of the spectra of bright-lined stars, as far as the observations went, and the conclusion arrived at was that they were nothing more than swarms of meteorites a little more condensed than those which we know as nebulae. The main argument in favour of this conclusion was the presence of the bright fluting of carbon which extends from 468 to 474. This standing out bright beyond their short continuous spectrum gives rise to an apparent absorption band in the blue. . . . Direct comparisons of the spectrum of all the three stars in Cygnus with the flame of a spirit-lamp have been made by Mr. Fowler, and these showed an absolute coincidence of the bright baud in the stars with tbe blue band of carbon seen in the flame. It was found quite easy to get the narrow spectrum of the star superposed upon the broader spectrum of the flame so that both could be observed simultaneously." D 2 36 Dr. and Mrs. Iluggins. On Wolf and [Dec. 11, showed at once the substantial accuracy of Yogel's measures, and the striking difference of position of the band in the star No. 4001 from tint which it holds in the other two stars. The obvious want of agreement of the star bands with the blue band of the Bunsen flame was seen at once. Their relative positions appeared to agree substantially with the positions represented in No. 2 and No. 3 of the diagram, which are based on Vogel's measures. More careful and repeated observations brought out clearly, as is indeed shown by Vogel's curve, that the star bands differ in character as well as in position from the blue band of the hydrocarbon flame, and also in some respects from each other. Before giving in more detail the results of our observation on each of the three stars, it should be stated that in all the stars the continuous spectrum is not in our instruments a short one, ending before the position of the bright blue band is reached. On the contrary, an examination with all three spectroscopes showed that the continuous spectrum, though enfeebled by absorption a little before reaching the blue band, can be traced, as is shown in Vogel's curves, quite up to the band, and indeed extends for a long distance into the violet beyond the bine band. The blue band does not in our instruments stand out bright beyond the end of a short continuous spectrum, but falls upon a fairly luminous continuous spectrum, which can be traced past the blue band into the violet, apparently as far as the eye could be expected to follow it. We suspected blight lines or bands in the region more refrangible than the blue band, but in such faint objects this is a point which should be determined by photography. Professor E. C. Pickering has since kindly informed us that his photographs of the star No. 4001, which extend into the ultra-violet region, show beyond the blue band the bright hydrogen lines at 434, 410, 397, and 389 ; and also other bright lines at 462, 455, 420, 406, 402, 395, and 388. In his photographs of the stars 4013 and 3956, however, the only well-marked line is in the blue at 470. Star 4001. — In this star, as is shown by Vogel's measures and curve, the bright blue band is less refrangible than in the other two stars, and approaches therefore nearer to the position of the blue band of the hydrocarbon flame. The appearance and position of the band in the star as contrasted with that of carbon, when observed in spectroscope B, are represented in spectrum No. 4 of the diagram. The brightest part of the band, from about X 468 to X 469, falls off rather suddenly in brightness at about these wave-lengths, but can be traced towards the red as far as about X 471 '5, and as far in the blue ns about X 465*5. 1890.] Rayefs Bright-Line Stars in Cygnus. '67 In our observations of this and the other stars we did riot attempt micrometric measures of the blue band, but we estimated their positions by means of the intervals between the five flutings of the band of the Bunsen flame. In the case of objects so faint in our instrument when viewed under the dispersion of spectroscope B, we did not consider there would be any real gain of accuracy by attempting to take measures. Though the wave-lengths assigned to our positions must therefore be regarded as not more than approximately correct, we have no hesi- tation in considering them fully accurate enough for the purpose of our investigation. The star band is not split up into well- separated maxima, as is the Bnnsen flame band, but we have little doubt that the brightest part of the band, from \468 to X469, which is much, and rather suddenly, brighter than its beginning and termination, consists of bright lines. Lines appear to flash out at moments, but in our instruments they cannot be seen with sufficient steadiness for us to be sure of their number and position. Under certain conditions of the electric discharge, the normal rela- tive brightness of the component flutings of the blue hydrocarbon band has been observed to be so far changed that the position of maximum intensity is moved from the less refrangible end of the band towards the blue end; but the five flutings remain without any change of their position in the spectrum.* Dr. Hasselberg, by means of feeble disruptive discharges from tin- foil terminals placed outside an exhausted tube containing vapour of benzole, obtained a nearly pure spectrum of the order of that in a hydrocarbon flame mixed only with faint lines of hydrogen. He says: " Es war aber hier die violette Gruppe sehr schwach. Dagegen schien mir die blaue Gruppe relativ heller als im Flammenspectrum, und sie hatte ausserdem entschieden ihre grosste Intensitat nicht an der weniger brechbaren Kante, sondern inehr nach dem Violetten hin. Dasselbe schien mir auch mit der gelben Gruppe der Fall zu sein. In Bezug auf die grime Gruppe konnte ich aber keine Vcr- schiebung des Intensitatsmaximums bemerken." Dr. Hasselberg gives curves to show the amount of this change of intensity in the blue group and in the orange group. In the blue group the maximum is moved from the first to the third line, that * "It is necessary to state that the maximum luminosity of the blue band, under some conditions, is about 468. . . . The conditions under which this band hns its maximum luminosity at 468 in Geissler tubes seem to be those of maximum conductivity. If the pressure be high, all the members of the group are sharp, and the luminosity of the band is almost uniform throughout. This always occurs when the pressure is very low. At intermediate stages of pressure, however, the luminosity has a very decided maximum at about 468 " (Appendix to the Bakerian Lecture for 1888, 'Koy. Soc. Proc.,' vol. 45, pp. 167, 168). 38 Dr. and .Mrs. Hugging. On Wolf and [Dec. 11, is, to about \ 4698. His curve gives the brightness of the maximum over that of the first line as about 7 to 6, whereas the normal relative intensity of these two lines is in the inverse direction and as about 2 to 4 (Watts, 'Index of Spectra,' p. 30).« A similar change from the normal relation of brightness of the flatings within the band, even if removed to X 468, does not seem to us to bring the star band sufficiently into accordance in character and position with those of the band of the hydrocarbon flame to justify us in attributing the blue band in the star to carbon. Though we traced the band a little further towards the red, than the position of the beginning of the band given by Vogel's measures, yet it is very faint, and without any increase in brightness at the place of the second fluting of the carbon band, beyond which we were unable to see it. According to Hasselberg's curve, the second bright fluting, where in our instruments the star band ends, still retains a brightness of about 11/12 of that of the maximum, and the first line, at the position of which no brightening of the feeble continuous spectrum of the star could be detected, a brightness of about 6/7 of that of the maximum. That the flutings of the band were not obscured by the absorption band at this part of the spectrum appears clear from the circumstance that we could trace the faint continuous spectrum up to the bright band. Vogel's and our observations agree in making the band run on some distance beyond the visible termination of the blue band of the Bnnsen flame. Piazzi Smyth, under some conditions, observed a large number of faint " linelets " beyond the " 5th leader " of the band, where its visibility usually ends ; and in the brilliant light of the arc the band can be traced further in the blue. The extension of the band under such circumstances does not seem to us to affect our present argument ; for in the very feeble light of the star we may Bnrely take it that the carbon band, if present, could not be seen to extend further than its usual visible limit in a Bunsen flame, namely, about X 468. Perhaps it should be stated in connexion with the circumstance that we saw the band extend a little further towards the red than Vogel did, that at the time of our observations the hydrogen line at F was not visible in our instruments, whereas it was bright at the time when Vogel observed the star. In the spectrum of a similar star, D.M. +37° 3821, in which the hydrogen line at F at the time was bright, the blue band was seen by us to stop near the place given by Vogel in his measures of the star No. 4001. Not only is there no coincidence, so far as Vogel and we have observed, of the position of the band in the star with that of the blue * ' Mem. de 1'Acad. Imp. dee Sciences de St. Petersbourg,' TO!. 22, No. 2, 1880, p. 82. 1890.] Rayefs Bright-Line Stars in Cygnus. 39 band of the Bunsen flame ; but, further, the want of accordance of its general characters is so great as to make the view that its origin is carbon very improbable. This improbability is very greatly in- creased when we find, as will be shown presently, that no traces whatever of the very bright beginnings of the more brilliant gresn and orange bands could be detected by iis in any of the stars. Further, Professor E.G. Pickering has kindly sent to us an account of his photographs of this star, which, though they show the hydrogen line at X 43-4, do not exhibit any brightness at the positions of the indigo hydrocarbon bands, beginning near 4312, and X 4382. This star, however, can scarcely be taken by itself; in the case of the other two stars, in the spectra of which, according to Vogel's, Copeland's, and our own observations, the brightest part of the blue band is from X 464 to X 465, but nearer X 465, quite outside the ordinary visible limit of the carbon band, the evidence seems very strong indeed that the band does not owe its origin to carbon. We satisfied ourselves that when the spectrum of the star is examined under the dispersion of spectroscope B, none of the brighter parts of its spectrum fell at, or very near, the green, orange, and indigo flutings of the hydrocarbon flame spectrum ; at these positions we were unable to detect any sensible brightening of the star's spectrum. Professor Copeland's measure of the blue band in 1884 was X 469'5. No. 4013. — Vogel does not give measures of the beginning and the ending of the band in this star, but only of the brightest part : — " Hellste Stelle, nahezu Mitte, einer breiten verwaschenen Bande, X. 464." He gives, however, a diagram of the spectrum in which the bright blue band is represented as substantially coincident in position and in general character with that in the spectrum of No. 3956. Our observations agree substantially with those of Vogel, but they make the band to consist of two parts — a very bright part, from about X 466 to X 464, but brightest near X 465, and a very faint band, apparently detached from the bright one from about X 4685 to about X 4705. This faint band is brightest near where it ends rather abruptly at the more refrangible end. The very bright band has not the character of a fluting, nor is it broken up into maxima widely separated like those of the Bunsen flame band, but appears to be a group of bright lines. The lines were only glimpsed at moments ; it is therefore difficult to make a drawing which truly represents the character of the band as seen in our instruments. The band, which is shown at No. 5 of the diagram, is left unfinished at the more refrangible end, as we were not certain how far we ought to consider it to extend. In this star (as we shall show to be the case in No. 3956 also), the 40 Dr. and Mrs. Huggins. On Wolf at the point £ of the axis, we get 1 d — — . o^ = 0. iff dr d Mr. R. A. Sampson. [Dec. 11, Therefore — ad Whence disregarding a constant. But By = V and clearly, ^ (-m, = — 2m . — . r = —2.IH . B\nO . . cos 0, Hence = - V- («, + (m, £) - ^ (»n, ?) + c Therefore and where = — 2mr (1), disregarding a constant. Thus if m =/(f) d£, we may, by properly choosing the function/, write (2), where YT is the current function for any irrotational motion in a liquid, symmetrical about the axis of z. Again, if r = ^{^+(2-?)"}, dr w dr _ z—£ dv ~ V dz ~ r d*r 1 tr3 d*r 1 (z — r)3 Therefore J^+^ = ™ 1 r dw 1890.] On Stokes s Current Function. 49 and the expression (1), and consequently also (2), satisfies the differential equation J2V, &y I «ty ~; — o ~r T~5 — -3 — w ....................... \'JJi cftr* az~ w az or, as I shall write it, D^- = 0. When the motion is rotational, (3) no longer holds. In fact, as is well known, we have under all circumstances — D^= -2o>, " where w is the resultant molecular rotation at the point (•zzr, z). Thus, if there is molecular rotation in the fluid, (3) is replaced by a.3 .. d2 d» 1 rf 1 d2 Again, it V" stand for the operator + _| — _| -- rf'ar'5 az- •ar a^nr -nr" a0- sin 0 Consequently sin <& u) dx dy dz where T^O ^s a solution of (3). Or \(f consists of a solution of (3) together with - X the poten- 2?r sin 0 tial at the point considered of a distribution of mass of density at any point sin 0 X the molecular rotation at that point. This result is given by Basset, ' Hydrodynamics,' vol. 2, § 306. I give one other general result. ?ince the circulation in any evanescible circuit drawn in a meridional plane is - 1 1 — D f dw fh ................. (5), VOL. XL1X. 50 Mr. R. A. Sampson. [Dec. 11, whore the integration extends over the area embraced by the circuit. This result enables us to transform D^r readily from cylindrical to other systems of coordinates. For instance, consider polar coordi- nates, r, 0, and let us find the circulation in a small rectangle bounded by r, r + dr, 0, 0 + dO. Let the velocities in the direction of r and perpendicular to it be R, 9. Then the circulation in this circuit is Rdr + Per + -^ (9r) dr~\ d0- |~R +^ di\ dr-Or dO .„ r = rdrd0 \_ dQ , e dR~\ - --- -=- - i- rddj Now G = - 1 (ty r sin 0 ' dr ' 1 dllr r~ sin 0 ' dO ' Thus the expression in square brackets is — or p ^ sing d ( l_d+\ dr*^ r2 dO \sin0d0J if p. stands for cos 6. Other applications will be found later. (6), 1890.] On Stokes s Current Function. 51 Reverting now to the expression (1), it will be seen that the direct distance of any point from a point on the axis of symmetry plays the same part in the theory of Stokes's current function that is played by its reciprocal in the theory of the potential function belonging to symmetrical distributions of matter. Thus if r0, 0, r, 6, be the coordinates of a point upon the axis, and of any other point, the distance between these points, x/C^o2— 2r0r cos 0+r2), may be developed in a convergent series, say ! §f ~^ J- (cos 0} or ".to -** ln (cos 0)' according as r0 is greater or less than r, Ifl(cos 0) being a certain function of 0, and we see from (6) that (1_^) 4+rc (n-1) 1,00 = 0 ......... (7). Now it is evident from the analogue of zonal harmonics that it is proper to discuss the function In(cos 0), and other solutions of (7) before considering the applications of Stokes's current function to the motion of liquids. It is with this discussion that the first three chapters are occupied, and, as might be expected, the theory closely resembles that of spherical harmonics. I have accordingly made free use of the order and methods adopted by Heine in his ' Hand- buch d. Kugelfunctionen,' more especially in chapters i and ii,* where the necessary changes were slight. Moreover, the functions I deal with have themselves been discussed by Heine, on a different method, and most of the expressions which I find in the following pages are given by him. Full references to these are given in §18. The idea of developing the solutions of D^ = 0 in a manner more or less analogous to that employed with regard to Laplace's equation appears to have been first used by 0. E. Meyer, f who obtains the equation (7), shows that the functions contain 1 — /t2 as a factor, and that they obey (28), chapter ii. An expression which shows the relation of the functions to zonal harmonics was given by Mr. Butcher ;J and functions of fractional order have been used by Mr. Hicks, § in connexion with his researches on the theory of the motion of vortex rings. The fuller account of such functions which is found in the following pages may be of interest in relation to these ; for example, I would refer to § 63, chapter v. * The following sections of the first three chapters contain methods or results •which, so far as I am aware, are original :— 12, 13, 17, 21, 25, 26, 29, 30, 32, 36, 38, 40, 42. The remainder of the paper is original, except where specially acknow- ledged, or where a result is too well known for that to be necessary. t ' Crelle,' vol. 73, 1871. % ' London Math. Soc. Proc.,' vol. 8. See p. 143, chapter vi. § ' Phil. Trans.,' 1884, 1885. E 2 52 On Stokes s Current Function. [Dec. 11, The applications to hydrodynamics whirh I here give are of mathematical interest rather than physical. They are chiefly in con- nexion with the motion of viscous liquids. In ' Crelle-Borchardt,' vol. 81, 1876, Oberbeckhas given the velocities produced in an infinite viscous liquid by the steady motion of an ellipsoid through it, in the direction of one of its axes, and from these Mr. Herman* has found the equation of a family of surfaces containing the stream lines relative to the ellipsoid. In chapter vi, Stokes's current function is obtained by a direct process for the flux of a viscous liquid past a spheroid, and it is shown that the result differs only by a constant multiple from the particular case of Mr. Herman's integral. Some minor applications are also given, namely, the solutions are obtained for flux past an approximate sphere, and past an approxi- mate spheroid. The solution is also obtained for flux through a hyperboloid of one sheet, where it appears that the stream surfaces are hyperboloids of the confocal system. A particular case is that of flux through a circular hole in a wall, and this is interesting because we see that, by supposing internal friction to take place in the liquid, we find an expression which gives zero velocity at the sharp edge, and thus avoids the difficulty which is always present in the solution of such problems on the supposition that the liquid is perfect. A comparison may be instituted between this problem, and that of the effect of a disturbing periodic force upon a dynamical system capable of vibrating alone with a period eqnal to that of the force. It is well known that the amplitude of the vibration induced appears infinite, if we totally disregard friction, and this difficulty is met by the fact that the damping effect of even slight friction is rendered considerable by high velocities. Now a viscous liquid can move irrotationally, and, if there were no friction at the boundaries, this is the class of motion it would take in cases of flux past or through obstacles. But if the obstacle terminated in a sharp edge, this would make the velocity there infinite, and the friction, however inconsiderable elsewhere, would here become of account. The boundary conditions which were necessary for the existence of irrotational motion throughout the liquid would no longer apply, and the whole character of the solution would be changed. This would at any rate seem to apply to cases in which the whole motion is slow, and when, consequently, the boundary con- ditions which must hold are pretty well understood. The paper concludes with an attempt to discuss the flux past a spheroid, or through a hyperboloid at whose boundary there may be slipping. The current function is not obtained, all that appears being that it probably differs from the parallel case of the sphere in being far more complicated than when there is no slipping. From * « Quart. Joura. Math.,' 1889 (No. 92). 1890.] Presents. 53 this we except the case of the flux through a circular hole in a plane wall, when the solution for no slipping satisfies the new con- ditions. Presents, December 11, 1890. Transactions. Adelaide : — Royal Society of South Australia. Transactions and Proceedings and Report. Vols. IX, XII. 8vo. Adelaide 1887, 1889 ; Transactions. Vol. XIII. Parti. 8vo. Adelaide 1890. The Society. Amsterdam : — Koninklijke Akademie van Wetenschappen. Jaar- boek. 1889. 8vo. Amsterdam ; Verhandelingen. Deel XXVII. 4to. Amsterdam 1890 ; Verslagen en Mededeelingen (Letterkunde). Deel VI. 8vo. Amsterdam 1889 ; Verslagen en Mededeelingen (Natuurkunde) . Dee! VII. 8vo. Amster- dam 1890. The Academy. London : — British Museum. Catalogue of Birds. Vols. XIII, XV, XVIII. 8vo. London 1890; Catalogue of the Fossil Reptilia and Amphibia. Part 4. 8vo. London 1890 ; A Guide to the Exhibition Galleries of the Department of Geology and Palaeontology. Parts 1 — 2. 8vo. London 1890. The Trustees. Society of Antiquaries. Index to the Archoeologia, vols. I — L. 4to. London 1889. The Society. Lund : — Uuiversitet. Arskrift (Mathematik och Naturvefcenskap). Tom. XXV. 4to. Lund 1888-89 ; Ditto (Medicin). Tom. XXV. 4to. Lund 1888-89 ; Ditto (Philosophi, &c.). Tom. XXV. 4to. Lund 1888-89 ; Ditto (Theologi). Tom. XXV. Lund 1888-89. The University. Manchester : — Public Free Libraries. Thirty-eighth Annual Report, 1889-90. 8vo. Manchester 1890. The Committee. Melbourne : — Royal Society of Victoria. Proceedings. Vol. II. 8vo. Melbourne 1890. The Society. Mexico : — Sociedad Cientifica " Antonio Alzate." Memorias. Tomo III. Num. 7—12. Tomo IV. Num 1-2. 8vo. Mexico 1890. The Society. Milan : — R. Istituto Lombardo di Scienze e Lettere. Atti della Fondazione Scientifica Cagnola dalla sua Istituzione in poi. Vols. 8—9. 8vo. Milano 1888, 1890. The Institute. Montreal : — McGill College and University. Calendar. 1890-91. 8vo. Montreal 1890. The College. Munich: — K. Bayerische Akademie der Wissenschaf ten. Sitznngs- berichte. Bd. II. Heft 1-2. 8vo. Munchen 1890. The Academy. 54 Presents. [Dec. 11, Transactions (continued). Physikalisch-Medicinische Societat. Sitzungsberichte. Heft 22. 8vo. Munchen 1890. The Society. Paris: — Association Francaise pour 1'Avancement des Sciences. Compte Rendu de la 18me Session. 8vo. Paris 1889. The Association. Prague : — Konigl. Bohmiache Gesellschaft der Wissenschaften. Sitznngsberichte (Mathem.-Naturw. Classe). Jahrg. 1890. Bd. I. 8vo. Prog ; Sitzungsberichte (Philos.-Histor.-Philolog. Classe). Jahrg. 1889. 8vo. Frag [1890]. The Society. Sydney : — University. Calendar. 1890. 8vo. Sydney. [Two copies.] The University. Journals. American Journal of Philology. Vol. XI. No. 2. 8vo. Baltimore 1890. The Editor. Annales des Mines. 1890. Tome 17. Livr. 1-4. 8vo. Paris. Ecole des Mines, Paris. Annales des Ponts et Chaussees. 1890. Nos. 1-7. Personnel, 1890. 8vo. Paris. Ministre des Travaux Publics. Archives Neerlandaises des Sciences Exactes et Natnrelles. Tome XXIV. Livr. 2-3. 8vo. Harlem 1890. Societe Hollandaise des Sciences. Asclepiad (The) Vol. VII. Nos. 27-28. 8vo. London 1890. Dr. Richardson, F.R.S. Canadian Record of Science. Vol. IV. No. 3. 8vo. Montreal 1890. Natural History Society, Montreal. Epigraphia Indica, and Record of the Archaeological Survey of India. Part 5. 4to. Calcutta 1890. The Government of India. Galilee (Le) 1890. Nos. 6—10. 8vo. Paris. The Editor. Horological Journal (The) Vol. XXXII. Nos. 383—387. 8vo. London 1890. The British Horological Institute. Medico-Legal Journal. Vol. VII. No. IV. 8vo. New York 1890. Medico-Legal Society, New York. Naturalist (The) Nos. 180—184. 8vo. London 1890. The Editors. Nature Notes. Nos. 6—10. 8vo. London 1890. The Editors. Prace Matematyczno-Fizyczne. Vol. II. No. 2. 8vo. Warszawa 1890. The Editors. Revista do Observatorio. 1890. Nos. 6 — 9. 8vo. Rio de Janeiro. The Observatory, Rio de Janeiro. 1890.] Presents. 55 Brookes ( W. K.) On the Lucayan Indians. 4to. [Washington 1890.] The Author. Cameron (Sir C. A.) Report upon the State of Public Health in the City of Dublin for the year 1889. 8vo. Dublin 1890. The Author. Cotterill (J. H.), F.R.S. The Steam-engine considered as a Thermo- dynamic Machine. Second edition. 8vo. London 1890. The Author. Helmholtz (H. von), For. Mem. R.S. Die Energie der Wogen und des Windes. 8vo. Berlin 1890. The Author. Hinde (Gr. J.) Notes on the Radiolaria from the Lower Palaeozoic Rocks (Llandeilo-Caradoc) of the South of Scotland. 8vo. [London] 1890. The Author. Kirk (R.) On Primary Chloroform Syncope. 8vo. Glasgow 1890 ; A New Theory of Chloroform Syncope. 8vol Glasgow 1890. The Author. Leidy (J.) Notice of some Fossil Human Bones. 8yo. [Philadel- phia 1890.] The Author. Newton (Sir I.) Optice, sive de Reflexionibus, Refractionibus, Inflexionibus et Coloribns Lucis. La tine reddidit Samuel Clarke. Editio secunda. 8vo. Londini 1719. Mr. Horace K. Pope, Southampton. Perry (Rev. S. J.), F.R.S. Photographs and Drawings of the Sun. 4to. London 1890. Stonyhurst College, Blackburn. Rowell (G. A.) Electric Meteorology [Miscellaneous Essays, &c., of various dates]. 8vo ; Letters on Meteorological Phenomena. 4to. [Various dates.] The Author. :»i; Messrs. H. L. Callendar and E. H. Griffiths. [De<-. I*. December 18, 1890. Lieut -General STRACHEY, R.E., Vice-President, in the Chair. The Presents received were laid on the table, and thanks ordeml for them. The following Papers were read : — I. " On a Determination of the Boiling Point of Sulphur, and on a Method of Standardising Platinum Resistance Thermo- meters by reference to it." By HUGH L. CALLENDAR, M.A.. FelJow of Trinity College, Cambridge, and E. H. GRIFFITHS. M.A., of Sidney Sussex College, Cambridge. Communi- cated by J. J. THOMSON, F.R.S., Cavendish Professor of Physics. Received November 29, 1890. (Abstract.) Experiments by different observers have shown that electrical resistance thermometers afford the most convenient and accurate method of measuring temperature through a very wide range. By selecting a particular thermometer as the standard, and directly com- paring others with it, it has been found possible to attain a degree of accuracy of the order of 0°'001 in the relative measurements between 0° and 100° C., and of the order of 0°'01 at 450° C. In a previous communication* it has been shown that, if t be the temperature by air thermometer, and if pt be the temperature by platinum resistance thermometer, the difference between them is very closely represented from 0° to 700° C. by the formula d = t-pt - 6 {*/100|2- lead The fixed points given in the above have not been so carefully de- termined as the boiling point of sulphur. They rest entirely on the * See Griffiths, ' Phil. Trans.,' A, 1891. 60 Mr. Lydekker. On the Generic [Dec. 18r assumption of the accuracy of the c-formula, and have not been directly referred to the air thermometer. We believe, however, that they are probably correct to 0°'l C., and that they may be safely used to standardise thermometers of limited range, in cases where it may happen to be inconvenient to make use of the sulphur point. In comparing the platinum and air thermometers between 0° and 100° C. observations were taken at intervals of 5° all the way up. The mean deviation of the observations from the parabolic formula (d) is only 0"'006. This corresponds to the limit of accuracy of the barometric readings, and there is no reason to suppose that the ^-formula may not represent the difference even more closely than this. The same platinum thermometer has been compared with several mercury thermometers standardised at Kew.* The result seems to show that the Kew standard reads 0°'l C. lower than our air-ther- mometer at 30°. II. ft On the Generic Identity of Sceparnodon and Phaxcolonus" By R. LYDBKKER, B.A. Communicated by Professor W. H. FLOWER, C.B., F.R.S. Received November 19, !«!»<>. [PLATE 1.] In the year 1872, Sir Richard Owen described and figured in the ' Phil. Trans.'f two imperfect lower jaws of a large extinct Wombat, from the Pleistocene of Queensland, under the name of PJiascolomys (Phoscolonus) gigas, the term Phascolonus being employed in a sub- generic sense. The species Phascolomys gigas, it should be observed, was founded by the same writer J at an earlier date, upon the evidence of a detached cheek-tooth. Subsequently Sir Richard 0\veu§ de- scribed and figured certain imperfect upper incisors, from Queensland and South Australia, characterised by their peculiarly flattened and chisel-like shape, under the new generic name Sceparnodon, which was suggested from their contour. In cataloguing the fossil Mammalia in the collection of the British Museum, || I was at once struck by the circumstance that, while the upper incisors of the so-called Phascolomys gigas were unknown, there were no cheek-teeth which could be referred to Sceparnodon, and it accordingly occurred to me that the two might prove to be identical. Support was afforded to this conjecture by the following circumstances : — 1st. The incisors of Sceparnodon agreed fairly well in relative size » Griffiths, ' Brit. ASBOC. Report,' 1890. f Page 257, PI. 36—38, 40. J • Encyclopaedia Britannica,' 8th ed., TO!. 17, p. 175 (1859). § ' Phil. Trims.,' 1884, p. 245, PI. 12. j| ' Cat, FOBS. Mamm. Brit. Mus.,' pt. 5, pp. 157—159 (1887). 1890.] Identity of Sceparnodon and Phascolonus. 61 with the jaws and cheek-teeth cf Phascolomys gigas. 2nd. The inci- sors of Sceparnodon were decidedly of a Wombat-like type, differing mainly from those of existing Wombats by their large size and excessive flattening and expansion. 3rd. One of the incisors of Sceparnodon agreed so closely in the structure of the enamel, and the reddish stains upon the same, with an upper premolar of Phascolomys gigas, that I even suggested both teeth might have belonged to the same individual animal. As the result of the above it was concluded that the teeth described as Sceparnodon Ramsay i were probably the upper incisors of Phascolomys gigas, and on this supposition it was considered that the latter was generically distinct from existing Wombats, and it was accordingly entered as Phascolonus gigas in the Museum catalogue. Thns the matter stood till a short time ago, when I visited the Exhibition of the Mineralogical Products of New South Wales, recently held at the Crystal Palace. Among the specimens exhibited was a small collection of Mammalian remains, obtained from clay beds, near Miall Creek, in the neighbourhood of Bingera, a station lying close to the northern border of New South Wales. These deposits, which have only recently been brought to notice, and appear to be full of Mammalian remains, have been described by Mr. W. Anderson, in the ' Records of the Geological Survey of New South Wales.'* All the bones from these beds are of a characteristic pale-brown colour, by which they can be distinguished at a glance from those of all other Australian deposits. The following account is taken from Mr. Ander- son's report, in order to give an idea of the richness of these ossiferous deposits. This writer observes that " several tons of bones were recovered, but the majority of them were more or less broken, although many perfect specimens were procured. Those which occurred most frequently in the deposit were the long bones of the limbs, the small bones of their distal extremities, and vertebras, and, as a rule, these were also the most perfect, and in the best state of preservation. Rib bones were rather common, but were mostly broken into short fragments. Of the vertebrae, specimens of the axis and atlas were usually found entire, both in the case of those which had belonged to the smaller animals, such as the Kangaroo (Macropws), &c., and also to the larger forms, such as Diprotodon, &c. Generally, however, only the bodies of the other vertebrae remained, the spines and the various processes having been broken off. Jaws, both large and small, occurred frequently, while isolated teeth were very abundant. The lower jaws of the larger forms were more fre- quently met with than the upper ; indeed, the latter were rather rare. When they did occur, however, they never formed part of an entire cranium, but always consisted of the upper maxillary and palatal * Vol. 1, pp. 116—225 (1839). r,-_> .Mr. Lydekker. Out/if' [Dec. 18, bones only, the rest of the cranium being absent. So far as I saw, there was no specimen that could be demonstrated to be a portion of the cranium proper of one of the larger animals, although there are undoubtedly small fragments of the cranial bones among the collection, which has, however, not yet been thoroughly examined. The bones of the pelvis were of rare occurrence, fragments of the thickest part of the os innominatum, about the rim of the acetabulum, being the part generally met with. In one instance, however, a very large portion of the pelvis of one of the larger animals was found, consisting of the greater part of one os innominatum, and the sacrum. Nearly perfect specimens of large scapula) were in a few cases obtained, while fragments of the scapulae of smaller animals, generally con- sisting of the articular head of the bone, with a portion of the neck and the coracoid process, the blade being wanting, were of frequent occurrence. The remains of birds, although by no means common, were often met with. " There can be little doubt as to the comparative age of this ossi- fcrous deposit. From the presence of pebbles of Tertiary bassalt and tachylite, and the fact that the whole series rests upon the Tertiary basalt of the district, its origin is certainly of post-Tertiary date. The thickness of the series, the occurrence in the deposit of angular, as well as rounded water- worn pebbles, together with the relation which the whole series bears to the general level of the country, all point to the supposition that it more probably belongs to the Pleistocene than to the Recent period." The series of specimens from those deposits shown in the Exhibition, which may be taken as a fair sample of the whole, comprises various remains of Procoptodon (the Macropus of Mr. Anderson), Diprotcdcn, NototJierium, molars and jaws of Phascolonus, and a large number of the incisors described as Sceparnodon. It will thus be apparent that if Sceparnodon were a distinct genus, it would be represented only by upper incisors, while Phascolonns would be equally deficient in these teeth. It is further noteworthy that all the Mammalian remains in the collection appear to belong to extinct genera, there being no evi- dence of the numerous species of Macropus and Phascolomys, which are so common in the Pleistocene of Queensland. This feature suggests that the Bingera deposits are somewhat older than those of the area last named. Seeing what an important bearing the remains from Bingera have on the question of the identity of Sceparnodon and Phascolonus, I requested permission from the Commissioners of the Exhibition to borrow some of the specimens so named, a request which was at once most courteously acceded to. In due course I received from the Commissioners part of the right ramus of the mandible of Phascolonus, together with three imperfect LycLekJcer. Proc. Roy. Soc. VolA9.Pl. 1. \ PHASCOLONUS GIGAS. West, Newman., lith. 1890.J Identity of Sceparnodon and Phascolonus. 63 incisors of the so-called Sceparnodon. Of these, the lower jaw and the best preserved of the upper incisors are figured in the accompany- ing Plate. The lower jaw (Plate 1, figs. 2, 2a) has been much crushed, and appears to have belonged to an individual just attaining maturity. It contains the third and fourth molars in a perfect condition, the second molar somewhat damaged, part of the root of the first molar, and the base of the incisor. The fragment agrees in all respects with the nearly complete ramus figured in the ' Phil. Trans.' for 1872, PL 36, 37, and, like the latter, shows that Phascolonus differs from living Wombats in the relatively smaller size of the last molar, more especially as regards its second lobe. The Queensland specimen also shows that the mandibular symphysis of the extinct form was much larger, and also relatively wider at its anterior extremity, than in Phascolomys. These features alone would, perhaps, be sufficient to justify the generic separation of the extinct form as Phascolonus, and the great width of the anterior part of the symphysis is especially significant, as being apparently adapted to fit with the wide upper incisors described as Sceparnodon. The fragment of the upper incisor represented in figs. 1, la, belongs to the right side, and accords closely with the specimens figured in the ' Phil. Trans.' for 1884, PI. 12, as the types of Sceparnodon, although it is still wider than either of those examples. The cutting- edge is entire, and exhibits the same oblique bevelling on the posterior surface that is shown in two of the specimens figured by Sir R. Owen. Both the anterior and posterior surfaces are covered by a coating of cement, and while there is a well-marked layer of enamel on the ante- rior surface, on the opposite aspect this element is either totally wanting, or reduced to a rudiment. The structure and colour of the cement, enamel, and dentine agree in all respects with those of the molars in the lower jaw of Phascolonus, and, allowing for their greater relative width and flattening, the upper incisors accord in proportionate size with the lower molars, as deduced from a compari- son with a recent Wombat. With the foregoing circumstantial evidence before us, I therefore venture to consider that we are now justified in definitely regarding the so-called genus Sceparnodon as based upon the upper incisors of the gigantic extinct Wombat known as Phascolonus. From the great width of the upper incisors as compared with the lower ones, it is pretty evident that the former must have worked somewhat obliquely against the latter. An interesting question arises as to the nature of the food which these excessively wide, and apparently fragile, chisel-like, upper incisors were adapted to cut ; but the answer to this question I must leave to those intimately acquainted with the recent and Pleistocene flora of Australia. «'l M r. S. Deldpiiie. Contribution to llie [Dec. 18, DESCRIPTION OF PLATE 1. Remains of Phatcolonua gigot. Fig*. 1, la. — Anterior and posterior aspects of an imperfect upper incisor. Figs. 2, Za. — Outer and oral aspects of a fragment of the right mandibular ramu*. HI. 1, m. 2, »i. 3, m. 4, molars ; t, incisor. All the figures three-quarters natural size. 1I[. *• Contribution to the Study of the Vertebrate Liver." By SHKRIDAX DELEPINE, M.B. Edin. Communicated by T. LAUDER BRUXTON, M.D., D.Sc., F.R.S. Received No- vember 20, 1890. (Abstract.) Preliminary Remarks. — The following observations were made at the end of last year in the course of an investigation touching the action of drugs on cellular structure carried out by Dr. Lauder Brunton and myself, for the Royal Society. Arrangement of the Hepatic Columns in a Classical Liver Lobule.— The following arrangement is visible in a plane perpendicular to the direction of the terminal vessels occupying the centre and the peri- phery of such a lobule. The columns of cells extend radially round the hepatic veins only in tho direction of the portal veins, that is, in three, four, or five directions at most. In the intermediate region the columns present a typical feathery arrangement. The line from which the columns diverge will be called hereafter hepatic line of divergence. A similar arrangement is found around the terminal portal veins, giving rise to what 1 call portal lines of divergence. Towards the portal lines of divergence the columns of cells become smaller in diameter, and join each other, becoming continuous with narrow tubes lined with flat epithelium and having the character of intermediate tubes. These narrow channels open into more distinct terminal bile ducts. Arrangement of the Bile Canaliculi. — The liver columns branch from the portal lim-s of divergence towards the hepatic lines. This branching is, however, generally obscured by lateral anastomoses, but it becomes more evident when the bile canaliculi are distinct. Two sets of bile canaliculi may be recognised : 1. The main canalicnli, occupying the axis of the columns of cells and becoming comparatively wide in the portal zone ; it is the branch- ing of these which renders that of the columns so evident in some specimens. 2. The lateral canaliculi, which pass between the cells forming the walls of the main canaliculi. 1890.J Study of the Vertebrate Liver. 65 In addition to these two sets of passages an intracellular branched system of lacuna may be described as forming the rootlets of the canaliculi. These spaces open directly into the canaliculi, and have been previously partly described by Pfliiger and Kupffer. Description of a True, Secretory, or Primary Lobule. — From what precedes it follows that the liver tubes, instead of being grouped round the terminal hepatic veins, are distinctly arranged in small pyramidal masses, which correspond to the lobules of other glands. These lobules are composed of the tubules diverging from the intermediate tubes found in the portal line of divergence, each set of intermediate tubes opening into a terminal bile duct. An arrangement somewhat analogous had already (in 1882) been supposed to exist by Sabourin, but he had been unable to discover in healthy livers what he believed to exist and had been obliged to fall back upon diagrammatic repre- sentations which are not altogether correct. Development of the Liver. — Eberth and other observers since have recognised that the embryonic liver is composed of hypoblastic tubes branching in a mass of mesoblast. This being common to the liver and all other glands does not explain the differences between these organs. Between the third and sixth weeks of embryonic life (in man) nearly the whole of the mesoblastic tissue separating the hypo- blastic columns becomes transformed into embryonic veins full of blood. In other glands only a small part of that tissue becomes transformed into veins, the greater part remaining in the shape of interlobular and interlobar tissue. In the liver, therefore, the hepatic veins take the place of the greater part of the stroma of other glands. It is only around the oldest hypoblastic tubes which become ulti- mately ducts, and at the periphery of the organ, that a little meso- blastic tissue becomes transformed into fibrous connective tissue (Grlisson's capsule). Structure of the Hepatic Cells. — The mitoma gives unmistakable evidence of a further differentiation of parts of the trabeculae com- posing it. These trabeculae are contractile. The paramitoma is enclosed in the meshes formed by the mitoma, and is the chief seat of the anabolic and katabolic changes taking place in protoplasma. The products thus formed probably under the influence of the mitoma accumulate in the midst of the paramitoma ; when soluble, they permeate it ; when insoluble, they are precipitated in the shape of drops or vacuoles, globules, granules, crystals. For these products only the name of Paraplasma should be reserved. In the paraplasma two kinds of elements may be recognised, namely : — (1) those resulting from the katabolic process of the cell or other tissues (kataplasma), e.g., bile pigment; (2) those result- ing from the anabolic processes (anaplasma), e.g., glycogen. In the VOL. XLIX. y 66 Dr. A. Ransome. On certain Conditions that [Dec. 18, paramitoma of the liver cells the following anaplastic and kataplastic products may be demonstrated easily : — serous fluid (vacuoles) bile pigment, pigment containing iron, glycogen, fat, ut others, where there might be a possibility of infection, were enclosed in cages, so arranged that air could reach them through a * [Since this was written, I have learnt that Savitzky has ascertained that phthisical sputum, exposed " at the ordinary room temperature, and generally under all common life conditions," retains its infectiousness not longer than 2J months, and, other conditions being equal, a sputum dried in darkness loses its infectious properties within the same period as a sputum exposed to light. ' Med. Chronicle,' Nor. 1890, p. 117.] 68 Dr. A. Ranaome. On certain Conditions that [Dec. 18, thin layer of cotton wool, one kind of cage being constructed of two squares of glass, supported at their edges by cork, and surrounded by cotton wool, tlio other of small flasks the bottom of which had been cut off, and the lower edge resting in a small circular tray fitted with wool, the months of the flasks being also loosely stuffed with the wool. These watch glasses were then exposed for five weeks under the conditions already noted, commencing on April 29, 1890, with the exception of B. 9 and 10, which were started on May 2. Most of the specimens were withdrawn on June 3; but one, B. 10, was divided on May 13, and a portion, B. 10a, was introduced into a glass bulb and exposed for several minutes each day to a current of ozonised oxygen. All the specimens were then enclosed in a box and forwarded to the Pathological Laboratory, Owens College, where Dr. Dreschfeld, the Professor of Pathology, had kindly undertaken to carry out the necessary inoculations. Owing to various causes, some of these operations were not commenced until June 27, 1890, others until July 10. The animals used were rabbits, kept under favourable hygienic conditions. The dried sputum was mixed with sterilised water, to form a pasty mass, and this was inserted into the sub- cutaneous tissue of the back. All the instruments used were made thoroughly aseptic. The following tables give : — (1) The conditions of exposure. (2) The date of inoculation. (3) The date of death, by killing or otherwise. (4) Dr. Dreschf eld's report upon the results of the inocula- tion. 1890.] modify the Virulence of the Bacillus of Tubercle. Table I. — Influence of Dry Soil, Air, and Light. No. of speci- men. Conditions of exposure. Date of Dr. Dreschfeld's reports. Inocula- tion. Death. A. 1 In outdoor studio, June 27 Killed Rabbit in good condition; Bowdon. In light Sept. 4 wound completely healed, and free ventilation cicatrix of wound scarcely in flask arrange- visible. All inserted spu- ment tum completely disap- peared, only a few pig- inented streaks left, no caseation ; internal organs healthy. A. 2 Ditto, open watch- July 10 Killed In good condition ; wound glass Sept. 4 healed, good cicatrix, no caseous mass. In liver a number of disseminated firm spots; microscopically, these consisted of fibrous tissue; no tubercle bacilli found in them. B. 6 Ditto in cotton wool July 10 Killed In good condition ; cicatrix cage Sept. 4 healed, no trace of sputum left, no caseation where sputum had been inocu- lated, only a few pig- mented streaks. B. 7 Ditto in open cage July 10 Killed Good condition ; cicatrix per- until May 9, then Sept. 4 fect, some fibrous indura- cotton wool added tion in subcutaneous tissue where sputum had been ; no caseation ; inter- nal organs healthy. F Z 70 Dr. A. Ransome. On certain Conditions that [Dec. 18, Table II. — Influence of Dry Soil, Air, and Darkness. No. of speci- men. Conditions of exposure. Date of Dr. Drcschfeld's reports. Inocula- tion. Death. A.8 In darkened photo- June 27 Killed Rabbit in good condition, graphic room, Bow- Sept. 4 small caseous mass be- don, in watch-glass neath healed wound ; all internal organs healthy. Microscopic examination of caseous mass. — Granu- lar detritus, no tubercle bacilli. B. 8 Ditto in cotton wool June 27 Died Moderately emaciated ; wound cage iug. 26 healed, but the edges sepa- rated on pulling the skin at the sides. In the sub- cutaneous tissue beneath the wound a few yellowish, soft spots, about the size of pin-heads, surrounded by a zone of hypenemia. Internally all organs healthy, no signs of tuber- cle, right heart full of blood, left heart empty. Microscopic examination of the yellow spots shows them to consist of granu- lar detritus and a few granule cells ; no tubercle bacilli could be detected. B. 9 Under ward of Con- July 10 Died Emaciated ; wound healed sumptive Hospital Aug. 14 under a scab, a thin mass in full ventilation, in of yellow caseous material darkness, in cotton just beneath the skin. wool cage Heart and lungs healthy ; kidneys contained a num- ber of small cysts. In the caseous mass a few tubercle bacilli were found. 1890.] modify the Virulence of the Bacillus of Tubercle. 71 Table III. — Influence of Clay Soil, Bad Air, and Light. Date of fff. nf xi O. OI speci- men. Conditions of exposure. Dr. Dreschfeld's reports. Inocula- T\ Al_ tion. Death. B. 3 On window-sill of June 27 Died Large rabbit ; emaciated. small cottage bed- Aug. 14 Inoculation wound com- room in Ancoats. pletely healed, slight scab ; Flask arrangement no caseous material or any signs of sputum. Internal 1 organs healthy ; one white spot found on surface of liver. Microscopic exami- nation of this showed it to consist of round cells, some with one nucleus and others which were poly- nuclear. At the periphery of the nodule, fibrous tissue. Sections of the nodule showed no tubercle bacilli. B. 4 Ditto in open watch- July 10 Died Emaciated, wound at back glass Aug. 9 not healed, and appeared slightly sloughing at the borders. Lungs presented several small caseous no- dules ; pleura, heart, peri- toneum, liver healthy. Tubercle bacilli found in the caseous lung nodules. 72 Bacillus of Tubercle. [Dec. 18, Table IV. — Influence of Clay Soil, Bad Air, and Darkness. Date of No. of speci- men. Conditions of exposure. Dr. Dreschfeld's reports. Inocula- tion. Death. B.I On dark shelf by fire- June 27 Killed Babbit in good condition ; place in small cot- Sept. 4 wound completely healed, tage bedroom in no caseation, and only a Ancoats. Flask ar- small pigmcnted spot rangement where the sputum had been deposited ; all the internal organs healthy. B. 5 Ditto in a dark corner July 10 Killed Babbit in good condition ; near the bed. In Sept. 4 cicatrix where the wound watch-glass was, and beneath it a caseous mass about the size of a bean. Examined mi- croscopically, this mass contained tubercle bacilli. Nothing abnormal in any of the organs. Table V. — Influence of Dry Soil, Bad Air, and Darkness Date of No. of speci- men. Conditions of exposure. Dr. Dreschfeld's reports. Inocula- tion. Death. B. 10 Cotton wool cage, in July 10 Died Emaciated ; wound healed ventilating shaft Aug. 14 under a scab. A yellow from ward of Con- caseous mass about the size sumption Hospital of a small pea beneath the for ten days, then scab. The liver presented placed on top of a few yellowish nodules ; bookcase in sitting- all the other organs sound. room In the caseous mass a few tubercle bacilli were found; none in the liver. B. 10 A portion of the above July 10 Killed Babbit fairly well nourished ; was taken on the Sept. 4 cicatrix quite healed, no tenth day and ex- trace of inoculated matter, posed to a current of and no trace of caseation. ozonised oxygen for In the left lung one firm a few minutes daily nodule; this waft carefully for a fortnight examined microscopically and showed no bacilli. It was apparently only thickened pleura. 1890.] Presents. 73 It will be seen that none of the four specimens of sputum exposed to fresh air and light on a dry soil conveyed the disease, but one of the three portions exposed under similar conditions in darkness pro- duced tubercle. Of the two exposed in the cottage in Ancoats in the light one produced tubercle, and of the two specimens exposed in the same place, in comparative darkness, one caused tubercle, the other did not. Lastly, the specimen placed in the ventilating shaft from a ward in the Consumption Hospital, Bowdon, on a dry soil, conveyed the disease, and the portion removed from it after ten days and exposed to the action of ozonised oxygen did not produce tubercle. These experiments are too few in number to justify the statement of positive conclusions, but, so far as they extend, they go to prove that fresh air and light and a dry sandy soil have a distinct in- fluence in arresting the virulence of the tubercle bacillus ; that darkness somewhat interferes with this disinfectant action ; bat that the mere exposure to light in otherwise bad sanitary conditions does not destroy the virus. There are also some indications that the presence of a cotton wool envelope may interfere somewhat with the action for good or evil of both good and bad air respectively. Further observations are now being made with sputum exposed by Professor Tyndall at Bel Alp, Switzerland, in light and darkness, each kind for 10 days and 14 days respectively, and compared with the same sputum exposed in the same cottage in Ancoats. The pathological results of these specimens have not yet been made out. The results will be given in a future note. The Society adjourned over the Christmas Recess to Thursday, January 8th, 1891. Presents, December 18, 1890. Transactions. Batavia : — Koninklijke Natuurkundige Vereeniging. Natuur- kundig Tijdschrift. Deel XLIX. 8vo. Batavia 1890. The Society. Bergen: — Museum. Aarsberetning. 1889. 8vo. Bergen 1890. The Museum. Bern: — Naturforschende Gesellschaft. Mittheilungen. 1889. 8vo. Bern 1890. The Society. Birmingham: — Philosophical Society. Proceedings. Vol. VII. Part 1. 8vo. Birmingham [1890], The Society. Chapel Hill : — Elisha Mitchell Scientific Society. Journal. 1890. Parts 1-2. 8vo. Raleigh (N. Carolina). The Society. 74 Presents. [Dec. 18, Transactions (continued). Glasgow : — Philosophical Society. Proceedings. Vol. XXI. 8vo. Glasgow 1890. The Society. Gratz : — Natnrwissenschaftlioher Verein fur Steiermark. Mittheil- ungen. Jahrg. 1889. 8vo. Qraz 1890. The Society. Halifax : — Nova Scotian Institute of Natural Science. Proceedings and Transactions. Vol. II. Parts 1, 3-4. Vol. IV. Parts 3-4. 8vo. Halifax 1866-78. The Institute. Halle :— Verein f Ur Erdkunde. Mitteilnngen. 1890. 8vo. Halle. The Society. Hamburg: — Natnrhistorisches Museum. Mitteilungen. Jahrg. 1889. 8vo. Hamburg 1890. The Museum. Kew: — Royal Gardens. Bulletin of Miscellaneous Information. Nos. 43-47 ; Appendix 2-3. 8vo. London 1890. The Director. Konigsberg: — Physikalisch-Okonomische Gesellschaft. Scbriften. Jahrg. 1889. 4to. Konigsberg 1890. The Society. Lausanne : — Societe Vaudoise des Sciences Naturelles. Bulletin. Vol. XXV. No. 101. 8vo. Lausanne 1890. The Society. Leeds: — Philosophical and Literary Society. Annual Report, 1889-90. 8vo. Leeds 1890. The Society. Lie*ge : — Societe Geologique de Belgique. Annales. Tome XVII. Livr. 3. 8vo. Liege 1890. The Society. London : — British Museum. Catalogue of Printed Books. Laune — Lemalliaud. 4to. London 1890. The Museum. Institute of Brewing. Transactions. Vol. IV. No. 1. 8vo. London 1890. The Institute. Marine Biological Association. Journal. New Ser. Vol. I. No. 4. 8vo. London 1890. The Association. Odontological Society of Great Britain. Transactions. Vol. XXIII. No. 1. 8vo. London 1890. The Society. Photographic Society of Great Britain. Journal and Transac- tions. VoL XV. No.^2. 8vo. London 1890. The Society. Sanitary Institute. Transactions. Vol. X. 1888-9. 8vo. London 1890. The Institute. Society of Biblical Archaeology. Proceedings. Vol. XIII. Part 1. 8vo. London 1890. The Society. Manchester: — Geological Society. Transactions. Vol. XXI. Part 1. 8vo. Manchester 1890. The Society. Newcastle-upon-Tyne : — Natural History Society of Northumber- land, Durham, and Newcastle-upon-Tyne. Natural History Transactions. Vol. X. Part 2. 8vo. Newcastle 1890. The Society. 1890.] Presents. 75 Transactions (continued). New York: — American Geographical Society. Bulletin. Vol. XXII. Nos. 2-3. 8vo. New York 1890. The Society. Observations and Reports. Edinburgh : — "Royal Observatory. Circular. Nos. 10-11. 4to. [Sheet.] 1890. The Observatory. Hongkong: — Observatoiy. Tables of Hourly Readings of Tides in 1887 and 1888. Folio. [Hongkong] 1890. The Observatory. Kiel : — Commission zur Untersuchung der Deutschen Meere. Ergebnisse der Beobachtungsstationen. Jahrg. 1889. Heft 1-9. Obi. 4to. Berlin 1890. The Commission. Madrid : — Observatorio. Resumen de las Observaciones Meteoro- logicas. 1886. 8vo. Madrid 1890; Observaciones Meteoro- logicas. 1888-89. 8vo. Madrid 1890. The Observatory. Oxford: — Radcliffe Observatory. Results of Astronomical and Meteorological Observations. 1886. 8vo. Oxford 1890. The Observatory. Paris : — Bureau des Longitudes. Annales. Tome IV. 4to. Paris 1890 ; Connaissance des Temps pour 1'An 1892. 8vo. Paris 1890 ; Annnaire pour 1'An 1890. 12mo. Paris. The Bureau. Washington : — Engineer Department, U.S. Army. Report from United States Geographical Surveys. Vol. I — Geographical Report. 4to. Washington 1889. The Department. Smithsonian Institution. Annual Report of the Board of Regents. ' 1886. Part 2. 1887. Parts 1-2. 8vo. Washington 1889. The Institution. U.S. Geological Survey. Monographs. Vol. XV (Text and Plates). 3 vols. 4to. Washington 1889; Eighth Annual Report. 1886-87. Parts 1—2. 4to. Washington 1889. The Survey. Wellington : — New Zealand Institute. Transactions and Proceed- ings. 1889. 8vo. Wellington 1890. The Institute. Wiirzburg : — Physikalisch-Medicinische Gesellschaft. Sitzungs- berichte. Jahrg. 1890. Nos. 1-7. 8vo. Wiirzburg', Ver- handlungen. Bd. XXIV. Nos. 1-5. 8vo. Wwrzburg 1890. The Society. Yokohama : — Seismological Society of Japan. Transactions. Vol. XIII. Part 2. Vol. XV. 8vo. Yokohama 1890. The Society. 1890.] Presents. 75 Transactions (continued'). New York: — American Geographical Society. Bulletin. Vol. XXII. Nos. 2-3. 8vo. New York 1890. The Society. Observations and Reports. Edinburgh : — Royal Observatory. Circular. Nos. 10-11. 4to. ("Sheet.] 1890. The Observatory. Hongkong : — Observatory. Tables of Hourly Readings of Tides in 1887 and 1888. Folio. [Hongkong] 1890. The Observatory. Kiel : — Commission zur Untersuchung der Detitscben Meere. Ergebnisse der Beobachtungsstationen. Jahrg. 1889. Heft 1-9. Obi. 4to. Berlin 1890. The Commission. Madrid : — Observatorio. Resumen de las Observaciones Meteoro- logicas. 1886. 8vo. Madrid 1890 ; Observaciones Meteoro- logicas. 1888-89. 8vo. Madrid 1890. The Observatory. Oxford : — Radcliffe Observatory. Results of Astronomical and Meteorological Observations. 1886. 8vo. Oxford 1890. The Observatory. Paris: — Bureau des Longitudes. Annales. Tome IV. 4to. Paris 1890 ; Connaissance des Temps pour 1'An 1892. 8vo. Paris 1890; Annnaire pour 1'An 1890. 12mo. Paris. The Bureau. Washington : — Engineer Department, U.S. Army. Report from United States Geographical Surveys. Vol. I — Geographical Report. 4to. Washington 1889. The Department. Smithsonian Institution. Annual Report of the Board of Regents. 1886. Part 2. 1887. Parts 1-2. 8vo. Washington 1889. The Institution. U.S. Geological Survey. Monographs. Vol. XV (Text and Plates). 3 vols. 4to. Washington 1889; Eighth Annual Report. 1886-87. Parts 1—2. 4to. Washington 1889. The Survey. Wellington : — New Zealand Institute. Transactions and Proceed- ings. 1889. 8vo. Wellington 1890. The Institute. Wiirzburg: — Physikalisch-Medicinisohe Gesellschaft. Sitzungs- berichte. Jahrg. 1890. Nos. 1-7. 8vo. Wurzburg ; Ver- handlungen. Bd. XXIV. Nos. 1-5. 8vo. W&rzburg 1890. The Society. Yokohama: — Seismological Society of Japan. Transactions. Vol. XIII. Part 2. Vol. XV. 8vo. Yokohama 1890. The Society. YOL. XLIX. Q 76 Mr. A. B. Baaset. Reflection and Refraction [Jan. -s. January 8, 1891. Lieut -General STRACHEY, R.E., Vice-President, in the Chair. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read : — I. " On the Minute Structure of the Muscle-columns or Sarco- styles which form the Wing Muscles of Insects. Pre- liminary Note." By E. A. SCHAFER, F.R.S. Received December 15, 1890. [Publication deferred.] II. " On the Minute Structure of Striped Muscle, with Special Reference to a New Method of Investigation, by means of ' Impressions ' stamped in Collodion." By JOHN* BERRY HAYORAFT. M.D., D.Sc., F.R.S.E. Communicated by Dr. KLEIN, F.R.S. (From the Physiological Laboratory, Univ. Edin.) Received January 2, 1891. [Publication deferred.] III. " On the Reflection and Refraction of Light at the Surface of a Magnetised Medium." By A. B. BASSET, M.A., F.R.S. Received December 17, 1890. (Abstract.) The object of the present paper is to endeavour to ascertain how far the electromagnetic theory of light, as at present developed, is capable of giving a theoretical explanation of Dr. Kerr's experiments* on the effect of magnetism on light. In the first series of experiments, polarised light was reflected from the polished pole of an electromagnet, so that the lines of magnetic force were perpendicular to the reflecting surface ; and in the second * ' Phil. Mag.,' May, 1877, and March, 1878. 1891.] of Light at the Surface of a Magnetised Medium. 77 series, the light was reflected from a polished plate of soft iron laid upon the poles of a horseshoe electromagnet, so that the lines of magnetic force were parallel to the reflecting surface. In both series of experiments, it was found that, when the circuit was closed, so that the reflector became magnetised, the reflected light exhibited certain peculiarities, which disappeared when the current was off. It was also found that the effects of magnetisation were, in most cases, reversed when the direction of the magnetising current was reversed ; that is to say, if the intensity of the reflected light was strengthened by a right-handed current, it was weakened by a left-handed one. In these experiments, a metallic reflector was employed, and con- sequently the results were complicated by the influence of metallic reflection ; it therefore seems hopeless to attempt to give a complete theoretical explanation of these experiments until a satisfactory electromagnetic theory of metallic reflection has been discovered ; and this, I believe, has not yet been done. There are, however, several non-metallic substances (such as strong solutions of certain chemical compounds of iron), which are capable, when magnetised, of producing an effect upon light ; and the theore- tical explanation of the magnetic action of such substances upon light is accordingly free from the difficulties surrounding metallic reflection. I have accordingly, in the present paper, attempted to develop a theory which is applicable to such media. The theory, which is due to Professor Rowland, is founded upon the following considerations : — It was proved by Hall* that, when a current passes through a con- ductor which is placed in a strong magnetic field, an. electromotive force is produced, whose intensity is proportional to the product of the current and the magnetic force, and whose direction is at right angles to the plane containing the current and the magnetic force. Professor Bowlandf has assumed that this result holds good in a dielectric which is under the action of a strong magnetic force ; accordingly the general equations of electromotive force become (1), where «, /3, 7 are the components of the external magnetic force, and C is a constant which depends upon the physical constitution of the medium. Writing p\ = C«, &c., it follows that, if the medium is isoti'opic, the equations of electric displacement are of the form. * < Phil. Mag./ March, 1880. t Ibid., April, 1881. G 2 Mr. E. Matthey. Further Contri/xitlnn* [Jan. 8, The boundary conditions are : continuity of magnetic indnction and electric displacement perpendicular to the reflecting surface, the of which is equivalent to continuity of magnetic force perpen- dicular to the plane of incidence; continuity of magnetic force along the line of intersection of the plane of incidence with the reflecting surface ; continuity of the rate at which energy flows across the reflecting surface. Now the refracted light consists of two waves, circularly polarised in opposite directions, and the reflected light is elliptically polarised; we have, therefore, four equations to determine the amplitudes of the two refracted waves, and the amplitudes of the two components of the reflected wave. The results of the paper agree with Dr. Kerr's experiments in the following particulars : — (i.) The reflected light is elliptically polarised. (ii.) When the magnetisation is parallel to the reflecting surface, no effect is produced when the incidence is normal, or when the plane of incidence is perpendicular to the direction of magnetisation. (iii.) When the plane of incidence is parallel to the direction of magnetisation, and the light is polarised tn the plane of incidence, the magnetic term increases from grazing incidence to a maximum •value, and then decreases to normal incidence. The principal point of disagreement is, that in all cases the inten- sity of the reflected light is unchanged when the direction of the magnetising current is reversed. I do not think that the results of the theory cnn be considered altogether unsatisfactory, since they certainly explain some of Dr. Kerr's experimental results ; and I am disposed to think that the disagreement is due to the disturbing influence of metallic reflection. At the same time, the question is one which can only be decided by experiment, and it is therefore most desirable that experiments on magnetised solutions should be made. IV. " Further Contributions to the Metallurgy of Bismuth." By EDWARD MATTHEY, F.S.A., F.C.S., Assoc. Roy. Sch. Mines. Communicated by Sir G. G. STOKES, Bart., F.R.S. Received December 22, 1890. In October, 1837, I read a paper before the Royal Society* upon a new method which I incidentally discovered while working with a view to separate copper from bismuth, by fusion with bismuth sulphide. » ' Roy. Soc. Proc.,' vol. 43, p. 172. 1891 .] to the Metallurgy of Bismuth. 79 I stated in this paper that bismuth " frequently contains a small proportion of copper, an element most detrimental even in small traces, and hitherto only eliminated by a wet process, costly in prac- tice and tedious in operation. It is necessary by such method to dissolve up the whole of the alloy, and precipitate the bismuth, in the usual manner — a bulky operation, and one requiring a considerable amount of time. It became therefore advisable, in order to treat cupriferous bismuth rapidly and upon a commercial scale, to effect this separation, it' possible, by means of a dry process." In further researches in the metallurgy of this interesting metal, a case was found in which bismuth contained a very small proportion of copper, under 0'5 per cent., but sufficient to render the metal use- less, and in fact, to destroy those characteristic properties upon which its industrial applications depend. Instead of treating this cupriferous bismuth by fusion with bis- muth sulphide, which necessitates a temperature sufficiently elevated to bring about a complete fusion of the bismuth sulphide, and conse- quently, unless very great care be taken, great loss by volatilisation of bismuth, it occurred to me to fuse the alloy, and, at a temperature a little above its melting point, to add a small proportion of sodium monosulphide. The mass was then stirred well, so as to bring every portion of the fused alloy into contact with the fused sulphide. After about one hour's stirring, a test was made of the molten metal, and it was found that the amount of copper in it was very considerably decreased. By skimming off the film of scoria which had risen to the surface, adding a further small proportion of the sodium monosulphide, and continuing the operation of stirring, every trace of copper was eliminated, and the bismuth so freed from copper rendered in every way suitable for industrial use. The first experiment was made upon a quantity of 105 kilograms, which yielded 94 kilograms of bismuth free from copper, and about 11 kilograms of skimmings containing the whole of the copper, their bismuth contents of course being available for reduction with further and larger quantities of skimmings as they accumulated. This process has been repeated upon very considerable quantities of cupriferous bismuth, and has proved to be successful. This question of keeping the temperature low is of much import- ance, for the lower the temperature the less tendency there is for the bismuth to volatilise, and as it is necessary to obtain the bismuth free from traces of impurity, which entirely change its nature, it will be seen that any improvement in manipulation, or in the process itself, which enables pure metal to be obtained possesses much interest. ,,, Presents. [Jan. 8, Presents, January 8, 1891. Tnmsactions. Berlin: — Deutsche Chemische Gesellschaffc. Berichte. 1890. Nos. 10-17. 8vo. Berlin. The Society. Konigl. Preuss. Akademie der Wissenschaften. Sitznngsberichte. 1890. Nos. 1-40. 8vo. Berlin. The Academy. Brussels: — Acaderaie Royale de Medecine de Belgique. Bulletin. Se>. 4. Tome IV. Nos. 6-11. 8vo. Bruxelles 1890. The Academy. Academie Royalo des Sciences. Bulletin. Ser. 3. Tomes XIX-XX. Nos. 5-11. 8vo. Bruxelles 1890. The Academy. Cambridge : — Philosophical Society. Proceedings. Vol. VII. Part 2. 8vo. Cambridge 1890. The Society. Edinburgh : — Royal Society. Proceedings. Vol. XVII (Pp- 193-400). 8vo. Edinburgh 1890. The Society. Hobart : — Royal Society of Tasmania. Abstract of Proceedings, April 22, 1890. 8vo. Hobart. The Society. Jena : — Medizinisch-Naturwissenschaftliche Gesellschaft. Jenaische Zeitschriffc fUr Naturwisseuschaft. Bd. XVII. Heft 3-4. 8vo. Jena 1890. The Society. London : — Anthropological Institute. Journal. Vol. XX. Nos. 1-2. 8vo. London 1890. The Institute. Chemical Society. Journal. July to December, 1890. 8vo. London ; Proceedings. Nos. 85-89. 8vo. London 1890. The Society. Geological Society. Abstracts of the Proceedings. Nos. 559-564. 8vo. [London] 1800; Quarterly Journal. Vol. XLVI. Nos. 183-184. 8vo. London 1890. The Society. Institution of Civil Engineers. Abstracts of the Proceedings. Session 1890-91. Nos. 1-3. 8vo. [London..] The Institution. Linnean Society. Journal (Botany). Nos. 175, 183-186, 189-192. 8vo. London 1890 ; Journal (Zoology). Nos. 124-125, 145-146. 8vo. London 1800; Transactions (Zoology). Vol. V. Part 4. 4to. London 1890; List of the Society. 1890-91. 8vo London 1890. The Society. London Mathematical Society. Proceedings. Vol. XXI. Nos. 381-390. 8vo. [London.] The Society. Pharmaceutical Society of Great Britain. Pharmaceutical Jour- nal and Transactions. July to December, 1890. 8vo. London. The Society. 1891.] Presents. 81 Transactions (contimied} . Physical Society. Proceedings. Vol. X. Part 4. 8vo. London 1890. The Society. Royal Astronomical Society. List of Fellows, June, 1890. 8vo. [London] ; Monthly Notices. Vol. L. Nos. 7-9, with Appen- dix. Vol. LI. No. 1. 8vo. [London] 1890. The Society. Royal Geographical Society. Proceedings. July to December, 1890. 8vo. London. The Society. Royal Institute of Bi-itish Architects. Journal of Proceedings. Vol. VI. Nos. 17-20. Vol. VII. Nos. 1-3. 4to. London 1890 ; Calendar. 1890-91. 8vo. London 1890. The Institute. Royal Institution of Great Britain. Reports of the Weekly Meetings. January to June, 1890. 8vo. [London.'] The Institution. Royal Meteorological Society. Quarterly Journal. Vol. XVI. Nos. 75-76. 8vo. London 1890. The Society. Royal Microscopical Society. Journal. 1890. Parts 4-6. 8vo. London. The Society. Society of Arts. Journal. July to December, 1890. 8\o. London. The Society. Society of Chemical Industry. Journal. Vol. IX. Nos. 6-11. 8vo. London 1890. The Society. Zoological Society. Proceedings. 1890. Parts 2-3. 8vo. London. The Society. Munich : — K. Bayer Akademie der Wissenschaften. Sitzungs- berichte (Math.-Phys. Classe). 1890. Heft 1-3. 8vo. Munchen. The Academy. Palermo : — Circolo Matematico. Rendiconti. Tomo IV. Fasc 5. 8vo. [Palermo'] 1890. The Circolo. Paris : — Academie des Sciences. Comptes Rendus. Juillet — Decembre, 1890. 4to. Paris. The Academy. Hicole Normale Superieure. Annales. Annee 1890. No. 11. 4to. Paris. The School. Societe de Biologic. Comptes Rendus. Juillet — Decembre, 1890. 8vo. Paris. The Society. Societe de Geographic. Bulletin. 1890. Nos. 1-2. 8vo. Paris ; Compte Rendu des Seances. 1890. Nos. 11-15. 8vo. Paris. The Society. Societe d'Encouragement pour 1'Industrie Nationale. Bulletin. Juin — Decembre, 1890. 4to. Paris ; Compte Rendu des Seances. 1890. Nos. 10-17. 8vo. Paris. The Society. Societe Philomathique. Bulletin. Ser. 8. Tome II. Nos. 2-3. 8vo, Paris 1890 ; Compte Rendu Sommaire des Seances. Mai— Novembre, 1890. 8vo. [Paris.'] The Society. Presents. [Jan. -s, Transactions (continued). Philadelphia : — Academy of Natural Sciences. Proceedings. 1890. Pp. 145—336. 8vo. [Philadelphia.] The Academy. Franklin Institute. Journal. Vol. C. Nos. 1-6. 8vo. Phila- delphia 1890 ; Index of Reports of the Committee on Science and the Arts, 1834-1890. 8vo. Phila, ]>oiiit of view, the shortening of tubes of electrostatic induct ion) is effected by the dissociation of the molecules into atoms, in other words, that " chemical decomposition is not to be considered as an accidental attendant on the electrical discharge, but as an essential feature of the discharge, without which it could not occur " ('Phil. Mag.,' vol. 15, 1883, p. 432). Free atoms must, on this view, exist in the path of the discharge to serve as the ends of the tubes of force as they shorten. If, however, we take this view of the discharge of electricity, the chemical decomposition attendant on the discharge along the positive column cannot consist of the consecutive inter- change of atoms between adjacent molecules, for, since on this view each atom would have to move up to the one in the adjacent mole- cule, the velocity of the atoms would have to be that of the discharge of the positive column, viz., about half that of light. The existence < f a wind in the tube of this velocity is, a priori, unlikely, and the following calculation will show that it would require the expenditure of more energy than we have at our disposal. Let us take the case of the discharge of a parallel plate condenser, the distance between the plates being 1 cm. Let F be the electro- motive intensity between the plates, K the specific inductive capacity of the gas ; then the energy per square centimetre of area of the con- denser plate is Let N0 be the number of atoms required to discharge unit area of the condenser ; then, if a is the density of the electricity on the con- denser and 6 the charge on each atom in electro-magnetic measure, N0€ = a. If m is the mass of one of these atoms, r the velocity with which the atoms move, their kinetic energy is If ]S" is the number of atoms in one gramme of the substance, then, if the charges on the atoms are the same as that deduced from electro- lytic considerations, Ne = 10* and Nw = 1. Now 4™ = KF. Making these substitutions, we find that the kinetic energy of the atoms is 1 KFpa 8» 10* ' 1891.] Luminous Discharge of Electricity through a Gas. 93 so that the ratio of the kinetic energy of the atoms to the energy in the electric field is 10*.F Now, at atmospheric pressure, F for air is about 3Xl012 ; we have seen that v = 1'6 x 1010 ; hence, in this case, the kinetic energy of the atoms is about 8000 times that of the electric field. If we had taken the case of a gas at a lower pressure, the disproportion would have been still greater. For this reason, the discharge along the positive column cannot be carried by atoms travelling at the same rate as the discharge ; the same argument would also be fatal to the view that the discharge takes place by the consecutive interchange of atoms between adjacent molecules. If, therefore, we are to retain the view (which seems to me to be almost established by the results of recent experiments) that the passage of electricity is effected by the dissociation of the molecules in the path of the discharge, we are precluded from sup- posing that in the positive column the discharge takes place by the molecules dissociating one after another, as the discharge comes up to them. In a paper in the 'Philosophical Magazine' for August, 1890, I suggested that we could reconcile the dissociation theory with the observed velocity of propagation of the discharge (of which I had, at that time, only obtained an inferior limit, and did not know that it started from the anode), by supposing that the molecules of the dielectric in the path of the discharge, before the discharge takes place, form themselves into a series of Grotthus chains, and that for the molecules which constitute any one of these chains, the dissocia- tion and recombination go on simultaneously. This may, perhaps, be made clearer by a somewhat crude illustration. A. B. C. D. If A, B, C, D represent consecutive polarised molecules, the simplest view of the discharge would be to suppose A to split up into atoms, its positive atom going up to B and combining with the negative atom of that molecule ; the positive atom of B is driven off, and travels to C and combines with the negative atom, and so on. On this view the velocity of the atoms would be very nearly that of the discharge which other preceding experiments have shown to be inadmissible for the positive column. If, however, we suppose that the molecules A, B, C, D, constituting a Grotthus chain, are split up simultaneously, and that while the positive atom of A combines with the negative of B, the positive atom of B is combining with the negative of C, and so on, then, in the time which elapses between H 2 '.'I Prof. J. , I. Thomson. On th? Propagation of the [Jan. 15, the commencement of the dissociation of a molecule to the end of the recombination of its atom with those of neighbouring molecules, a positive atom will hnve disappeared from one end of the chain and appeared at the other. Thus in this case, since the time taken for the decomposition and recombination of the molecules is independent of the length of the chain, whatever the length of the chain may be, th«; positive charge will travel from one end of the chain to the other in the same time, and thus the velocity of the discharge will be proportional to the length of the chain. In the paper referred to above, it i> gested that the high velocity of the discharge ( f the positive column is attained by the formation of Grotthns chains of suitable length, the column thus consisting of a series of separate discharges, the length of each discharge being that of the Grotthus chain ; these separate discharges are made manifest in the stratification which is so striking a feature of the positive column, the space between the bright portions of two striae corresponding to the length of the Grotthus chain ; thus, on this view, the stratifications are the mani- festations of the machinery which enable the positive discharge to travel at snch a rate. In the paper in the ' Philosophical Magazine ' it is shown that this view of the discharge agrees well with what is known as to the behaviour of striae. The preceding experiments show that the tubes of force which we imagine as stretching round the circuit, and contracting when the discharge takes place, are anchored almost completely to the negative electrode. When the discharge begins to pass., the ends of these tubes near the positive electrode will be agitated in an approxi- mately periodic way, electrical vibrations will travel along the tubes with the velocity of light, and, as one end of the tube is fixed, these will form stationary vibrations ; these stationary vibrations may be conceived to give the molecules of the gas in the tube a certain periodicity of arrangement, and lead to the formation of the Grotthus chains of definite lengths, required by the preceding explanation. It will be seen that this would make the position of the striae depend on that of the negative electrode, so that when the latter is moved the- strire ought to be displaced ; this effect has been observed by Gold- stein. As an alternative to the preceding view, it might perhaps be urged that the luminosity of the positive column outruns the positive discharge. This view, however, seems to be quite untenable in the face of Spottiswoode's and Monlton's experiments on the sensitive st.ite of the electric discharge (' Phil. Trans.'), for the relief effects observed in their experiments seem to show, without ambiguity, that the positive luminosity is coincident with free positive elec- tricity. Wo have also no evidence that a gas can be made luminous by 1891.] Luminous Discharge of Electricity through a Gas. 1'.") sadden alterations in the electric or magnetic intensity of the field in which it is placed, unless these are accompanied by the passage of free electricity through the gas. In order to get some further information about the laws which govern the propagation of the positive column, some experiments were made in which the discharge had to pass from the gas to mercury and out again from the mercury to the glass several times in its passage from B to G (fig. 1). The arrangement by which this was done is shown in fig. 3. Pieces of glass tubing, bent as in the figure, with baro- FIG. 3. metric tubes filled with mercury attached to their lowest points, were inserted in the circuit between B and G. By raising or lower- ing the vessels into which the ends of the barometer tubes dipped, mercury could be poured into or taken out of the bends in the tube. There were in all six of these mercury electrodes introduced between B and G. The displacement of the images, as seen through the tele- scopes, was observed (1) when the mercury was below the level of the tops of the barometer tubes, and (2) when the mercury filled the bends of the tube, blocking it up completely in six places. No appreciable difference could be observed between the displacements of the images in the two cases. When, however, the mercury was in the tube, the discharge had very much greater difficulty in getting through than when its path was not interrupted by the columns of mercury ; this was shown by the luminosity in the maiu circuit being very much fainter, and that in a branch circuit leading to the air- pump much brighter, when the mercury was in the tubes than when it was not. It seems, I think, pretty clear that what takes place when the '.'•'. Prof. J. ,J. Thomson. On the Propagation of the [Jan. !.">. ury is in the tube is something of the following kind. The positive electricity rushes from the anode down the tube until it reaches the first mercury plug; it attracts the negative electricity to the nearer end of this plug, and repels the positive to the other end ; this positive electricity begins to leave the mercnry immediately a?id travels down to the next mercury ping. The positive electricity which travels up to the first mercury plug and the negative electrification it produces on the mercury form an i ical double layer which takes some time to disappear, longer probably than the time taken by the electricity to travel from one end of the tube to the other. The time the luminosity takes to travel from B to G will thus not be much affected by the mercury plugs; but, as the discharge leaves behind it a series of electrical double layers on the sides of the mercnry columns nearest the positive electrode, the difficulty of forcing electricity through the tube will be temporarily increased. It is, I think, worthy of remark that the effects produced by dis- placement currents render it impossible to predict the velocity of the discharge of electricity through a rarefied gas. For, if we consider the processes which accompany this discharge, we have, first, the production of the electric field ; this causes an increase in the electric displacement, and in consequence produces magnetic effects ; and the displacement current behaves as if it had inertia, travelling through the medium with the velocity of light. When the intensity of the field is increased sufficiently to cause discharge, the electricity passes through the gas, and the electric field disappears. The convective current formed by the passage of the free electricity is balanced by the displacement current in the opposite direction, due to the dis- appearance of the electric displacement. The discharge, therefore, does not produce a magnetic field, and has, therefore, no inertia. The velocity of propagation of this discharge will, therefore, be governed by different laws from those which control currents pro- ducing a magnetic field, and need not, therefore, have anything to do with the velocity of propagation of light through the medium. By adjusting the circumstances under which the preliminary charging takes place, we can separate the magnetic force due to the charging by as long an interval as we please from the discharge. We can also, by charging sufficiently slowly, make the magnetic force at any instant as small as we please ; thus it is conceivable that we might have a copious discharge of electricity through a gas prac- tically unaccompanied by magnetic force. The very remarkable action of a magnet on the electric dis- charge is not inconsistent with this view, as on it the discharge consists of two equal and opposite currents, of which only one is 1891.] Luminous Discharge of Electricity through a Gas. 97 visible : we see the action on the visible current, but not the opposite one on the other. The most obvious explanation of the remarkable difference in the behaviour of the discharges from the anode and cathode is that it arises from some difference in the chemical action between the gas and the two electrodes. I have made a series of experiments in order to test this view, and have been led to the conclusion that an explanation of this effect by purely chemical action is delusive. At the same time I think that the necessity for the existence of some action between the gas and the electrode is shown by the fol- lowing experiment. In the ' Philosophical Magazine/ vol. 29, 1890, p. 441 (On the Passage of Electricity through Hot Gases), I described an experiment in which cold electrodes were plunged into a hot gas, such as iodine, heated until it dissociated, when it was found that no current passed through the gas until the electrode got hot, when it passed freely. The effect produced by the cold electrodes seemed too abrupt to be altogether due to the cooling of the adja- cent gas by the electrodes. I therefore made the following experi- ment in order to test this point. If the effect is due to the cooling of the gas, the temperature of the electrodes when the system begins to conduct ought not to vary much, whatever may be the material of which they are made ; while if the effect were due to chemical action between the gas and the electrodes, we should expect con- siderable variation with different electrodes in the temperature at which conduction begins. I therefore attempted to measure roughly the temperature at which conduction began (a) when the electrodes were iron, (b) when they were platinum. This was done by making one of the electrodes into a thermopile placed in circuit with a dead-beat galvanometer; in case (a) the thermopile consisted of an iron plate with a German-silver wire, in case (6) of platinum, foil and a German-silver wire. The electrode used as the thermopile was dropped cold into the hot gases and connected up with the main circuit. When the galvanometer in the main circuit first began to show decided indications of the passage of a current, the ob- server who was watching this galvanometer called to the observer at the dead-beat galvanometer in the thermopile circuit, and this observer read the deflection of this galvanometer. From this reading the temperature of the hot junction could n pproximately be determined. Ine experiment was repeated, using, instead of the iron- German silver couple, a platinum- German one, the platinum foil being wound round an iron plate to make it heat up at approximately the same rate as the first couple. It was found that the conduction began at a much lower temperature when the electrode was iron than when it was platinum, indicating that some action between the electricity and the gas was necessary for conduction. I could not, 1'^ Pn>f. .1. .1. Thomson, fin //«• /V.y.,/,/,r'/,,,; <>f the [Jan. !.">. ho.vover, detect any difference hot worn the positive and negative elect Hides in this respect. The ir:ise>; in which tliis effect was found w.-iv I, HC1, and HI. I next endeavoured to see if I could detect any difference in the chemical action of chlorine on a meta! positively or negatively elec- trified. This was done in the following way : — A and B (fig. 4) are Tin. 4. p— 50 r— 40 :— 30 h- 20 :— 10 E— 0 two coils of copper wire, of the same length, made from the same hank of wire, and as nearly as possible alike in all respects: these: are filled into two equal vessels which are connected by a U-tube 1891.] Luminous Discharge of Electricity through a Gas. 99 filled with sulphuric acid, which serves to indicate any difference in the absorption of the chlorine by the two c.oils of wire. The vessel was exhausted and then filled with chlorine, and A and B were placed in parallel with the electrodes of an induction coil, giving sparks about an inch and a half long. In this way one coil was positively and the other negatively electrified, and any dif- ference in the rate of combination of the chlorine with the metal would show itself by the motion of the sulphuric acid in the gauge. Only a very small motion of the sulphuric acid occurred, and this seemed to be accidental, as it was not reversed on reversing the coil. The difference between the rate of combination of chlorine with a positively and negatively electrified metal must therefore be small. Again, if the difference between the behaviour of the positive and negative discharge were due to purely chemical action between the gas and the electrode, we should expect this difference to be absent in the case where the electrodes consisted of a volatile liquid or solid, and the gas was the vapour of the electrode. I tried three cases of this kind : one in which the electrodes were water and the gas water vapour; a glass tube was completely filled with water, then placed on the pump, and the water boiled away until only just enough was left to serve as electrodes ; the tube was then sealed off and cooled down until the vapour pressure was low enough to allow the electric discharge to pass without difficulty ; this tube, however, had all the usual characteristics of the discharge through vacuum tubes, including the negative dark spaces and the striations. In the next experiment a similar tube was taken, the water being replaced by bromine ; this, too, showed the usual differences between the dis- charge at the two electrodes, and similar appearances were presented by a tube in which the electrodes were re-distilled arsenic and the gas arsenic vapour. Another difficulty in the way of explaining the difference at the two electrodes by chemical action is that no difference seems to be made in the appearance when a strongly electronegative gas, such as chlorine, is substituted for a strongly electropositive one, such as hydrogen. I next endeavoured to get rid of the electrodes altogether by trying to get a circular discharge in an exhausted re-entrant tube without any electrodes. For this purpose the primary was generally a piece of copper rod bent into a horse-shoe shape; the secondary circuit was an endless circular glass tube from which the air had been ex-- hausted. A Leyden jar, charged by a Wimshurst machine, was dis- charged through the primary, and produced by induction an electro- motive force round the exhausted tube. When the secondary was not shielded from the electrostatic induction of the primary, it was 100 Mr. A. E. II. Love. Note on ths present [Jan. 15, tilled with a uniform glow whenever the discharge passed through tin- primary circuit, but, when the electrostatic induction was shielded off by pieces of wet thin blotting paper connected to earth, no glow could be observed, though the wet blotting paper is not a sufficiently good conductor to shield off electromagnetic induction. The maximum integral electromotive force round the secondary is shown to be VM/L, where V is the difference between the potentials of the coatings of the jar before discharge, L the coefficient of self-in- duction of the primary circuit, and M the coefficient of mutual induc- tion between the circuits. Though in my experiments this was greater than the electromotive force requisite for a discharge through gas at the same density between terminals separated by the length of the tube, not the faintest glow could be detected. A.11 ray efforts to get a discharge through the secondary have so far been unsuccessful,* and I feel sure that the ease of getting a discharge without electrodes, say by the motion of the upper regions of the earth's atmosphere across the lines of magnetic force, has been much over-estimated. Until, however, we have got a discharge without electrodes through nothing but the gas itself, we are unable to say whether the passage of the discharge from the positive to the negative electrode which occurs in gases is a consequence of having matter in two states in the path of the discharge, or whether it is an example of a more general law, that, whenever tubes of electrostatic induction shorten in a con- ducting circuit, they do so in the direction of the electric displacement. In conclusion, I have much pleasure in thanking Mr. Bartlett and Mr. Everett for the assistance they have given me in the course of this investigation. II. " Note on the Present State of the Theory of Thin Elastic Shells." By A. E. H. LOVE, M.A., St. John's College, Cambridge. Communicated by LORD RAYLEIGH, Sec. R.S. Received January 3, 1&91. In a paper read before the Royal Society in February, 1888, and published in ' Phil. Trans.,' A, of that year, I advanced a theory of the mode of deformation that takes place when a thin shell is vibrat- ing. The theory was founded on the form of the potential energy function, obtained by a method adapted from that of Kirchhoff for plates. It appears that, in case there are no surface-stresses on the faces of the shell, this function consists of two terms, of which one contains a certain function W2 and the thickness 2h as factors, and * Since this paper was sent in to the Royal Society, I have succeeded in getting a discharge without electrodes through a tube about 45 cm. in circumference. The discharge did not exhibit any signs of stratification. -Jan. 23, 1891. 1891.] State of the Theory of Ihin Elastic Shells. 101 the other contains a function W\ and A3 as factors. The term W2 depends entirely on quantities S/ull*. [Jan. 15, difficulty. Each of these writers has shown that, in particular statical problems relating to cylinders, the quantities expressing the exten- sion can be very small everywhere except in the neighbourhood of an edge, and there they may increase with such rapidity as to secure the satisfaction of the boundary conditions, the total potential energy due to extension, which varies as the surface integral of ^W2 over the middle surface, being, nevertheless negligible in comparison with that due to bending, which varies as the surface integral of /r"NY,. Mi Basset and Professor Lamb both suggest that this may be the solution of the difficulty in the case of vibrations also, and their n-Milts point to a method of approximation which might be applied to the general case, and such that it could be verified by mathematical analysis that Lord Rayleigh's solution, founded on an assumed t \ p>< -. is actually a very close approximation to the state of things in any part of a vibrating bell not very close to a free edge. It may be as well to point out what parts of the theory put forwaid in my paper specially require revision. (1.) On p. 500 the alteration suggested in Kirchhoff' s theory is erroneous ; the quantities «', v, w' are functions of «, /3, and their differential coefficients must be intro- duced as by Kirchhoff, and afterwards neglected ; this correction makes no difference to any of the n suits. (2.) On p. 503. Art. 4, the " products " neglected are such as occur in the equations when account is taken of the fact that the axes of reference are really not in fixed directions. If they had been retained, the part of the potential energy which is multiplied by A3 would have contained terms depending on the extension as well as terms depending on the bending. Mr. Basset has obtained, by a different method, the form of this function for cylindrical and spherical shells, with these terms expressed. It follows that the form given for the potential energy in equation (12), p. 505, is only correct in case either (a) the shell is unextended, when its second line vanishes, or (6) the extension is the important thing, when its first line may be neglected ; but it would most probably be sufficiently exact for the application of a method of approximation. (3.) The first paragraph of Art. 13, ]>. •''-.' 1, is wrong, and so are all other paragraphs to the same effect ; viz., it is incorrect to conclude that, because a^ a.-,, w do not every- where vanish, therefore W-Jis is infinitely small in comparison with \\ .,h. It appears, on the contrary, that the values of r. W. Marcet On the (7/«v/< /.-,// [.Jan. 15, CC. O) U ID ^m 1891.] Phenomena of Human Respiration. 105 The results from all these experiments will be found disposed in the form of tables (pp. 113 — 116). I shall first give a short account of the method adopted in the pre- sent inquiry, then describe the experiments, and finally state the results with which they have been attended. Two bell-jars were made use of. The air, in every one of the experiments quoted in this paper, was inspired through the nose and expired through the mouth, a mode of breathing easy to acquire, and soon becoming perfectly natural ; the person under experiment assumed the recumbent position in a deck- chair, with the feet resting on a stool. It was necessary to begin by determining the volumes of air and weights of carbonic acid expired normally, or in ordinary breathing, with the object of using 'these figures as standards for comparison. I need not say that every precaution was taken to obtain correct data on ordinary breathing. Next, the other bell-jar was supplied with atmospheric air to be re-breathed. A correction might have been introduced for the CO2 naturally present, but from its small propor- tion this correction was thought unnecessary. On no occasion was the laboratory used for the evolution of acids or alkalis, and its ventilation was kept up by one or two open windows. After re-breathing 35 litres of air during five minutes, the person under experiment was placed in communication with the other bell- jar, in such a manner that no air whatever was lost, or, in other words, while fresh air was inspired, the expiration following imme- diately the last expiration of re-breathed air was collected in the other bell-jar, now emptied of the expired air it formerly contained. While this bell- jar was being filled, the re- breathed air, from the other bell- jar (after its volume had been read, and temperature taken), was driven into an india-rubber bag faced with oil-skin, to prevent any loss of any C02 by diffusion. This bag had been kept flattened down between boards weighted with a piece of iron weighing 20 Ibs., a precaution taken to empty perfectly the bag before it was used for storing the re-breathed air. The bell-jar, having thus discharged its contents, was ready to be used afresh. The person expired from 34 to 38 litres of air immediately after the re-breathing stage of the experiment, and he was now placed in com- munication with the empty be 11- jar ; there was no loss of expired air through this passage from one bell-jar to another, and while fresh air was inhaled, the air expired was entirely collected, to the extent of from 34 to 38 litres, for subsequent analysis. A chronograph showed, to a second, the time required in the various stages of the experi- ment. Thus the whole history of the effects of re-breathing air was obtained, being divided into four stages : — 1st, natural respiration ; 2ndly, air 10H Dr. W. Marcet. On the Chemical [Jan. 1.% re-breathed ; Srdly, air expired immediately after re-breathing ami witb the inspiration of fresh air; 4thly, air breathed while no longer under the direct influence of re-breathing. The above is a general sketch of the investigation. I must nmv beg leave to go into the details of the work. The diagram on the next page illustrates the disposition of the instrument. The person under experiment, in the recumbent position in a deck- chair, held in his right hand an india-rubber tube connected with the bell-jar through a double-way cock, as I have explained in my last paper to the Royal Society. The cock was turned in such a position that the air inspired through the nose was expired into the open air, a little flag showing the movement of the expired air through, the tube. The experiment begins with the operator expiring through this tnbe into the external air. When respiration has become perfectly quiet and regular, the double-way cock is turned during an inspiration, and the air of the next expiration is collected in the bell- jar, which begins its ascending course. At the same time the hands of a chronograph are set in motion. After about 36 litres of air have been expired, the tube leading into the bell-jar is closed at the end of an expiration, and the chronograph is stopped. Some trouble was experienced in obtaining similar volumes of air' expired in a given time, say, about every seven minutes. I have come to the conclusion that most people do not breathe, even when perfectly still, exactly the same volume of air in a given time, and after an experience of many years, it was found that the best plan was to repeat the breathing two or three times, or more, in succes- sion, and to take, according to circumstances, either the mean of the different experiments, or the result of the last made. Any experiment differing widely from the others was rejected. The air collected finally was read off on the scale attached to the bell-jar, its tempera- ture was taken, the barometer read, and the air was analysed for the determination of its carbonic acid, by the same method as that which has been described in the paper in the ' Philosophical Transactions ' already referred to. The air left in the bell-jar was then driven out, and the jar made ready for further use. The next part of the work is the re-breathing. Perhaps half an hour has elapsed since air was first collected for the determination of CO2 in normal breathing ; during that time the person under experi- ment has remained perfectly still in the deck-chair. The bell-jar, which has not yet been used, is now thoroughly rinsed with common air and filled with air to the extent of 35 litres. It carries an indi:> rnbber tube, connected with the dome of the jar and supplied at thn end with a fork-shaped nose-piece (see diagram). This nose-piece has been ascertained to fit the nostrils of the operator, air-tight ; a second india-rubber tub?, with a mouth-piece at one end, is connected 1891.] Phenomena of Human Respiration. 107 at the other with a U'saaPe(^ pipe> opening under the bell-jar in the ordinary way. The bell-jar holding 35 litres of air is perfectly counter- poised, so that the operator moves it up and down unconsciously in the act of respiration, while the oil-gauge on the bell-jar registers VOL, XLIX. I 108 Dr. W. Marcet. On the Chemical [Jan. 15, barely from 1 to 2 mm. of difference of pressure, which is inappre- ciable. Placing the nose-piece in his nostrils, the operator breathes through his month for a few seconds, then he takes the mouth-piece in his mouth, and inhales the air of the bell-jar through the nose-piece, the bell -jar falling ; at that very instant the chronograph is started. The next expiration is from the month through the U-tube into the bell- jar, and so on, the air re-breathed circulating through the bell-jar. After five minutes have elapsed, every attention is given to stop the inspiratory tube and arrest the chronograph at the very end of an expiration, while another assistant opens the double-way cock, con- nected through tubing with the operator, and disposed so as to lead the air now expired into the other bell-jar ; the operator drops the nose-piece and takes an inspiration of fresh air, through the nose, then he expires out of the mouth into the empty bell- jar. He was, perhaps, beginning to feel a little uncomfortable ; sometimes a slight sensation of want of air was experienced, but not always, and one of my subjects hardly noticed any effect. I think I was affected most of the four who submitted to experiment, although it repeatedly happened that I felt no discomfort of any kind, beyond perhaps a slight want of air. Fresh air is inhaled with an undoubted sensation of comfort, and the volume of this air is in marked excess of the volume inhaled in ordinary breathing. During the first two or three minutes, large volumes of fresh air are inspired, then the breathing quickly subsides, and before 36 or 37 litres have been expired it has apparently resumed its usual rate, with the disappearance of all feeling of discomfort. I have stated above that the air re-breathed had been transferred from the bell-jar into an india-rubber bag, allowing the bell- jar to be utilised for collecting the air expired in the last stage of the experi- ment. The india-rubber tube and double- way cock were so arranged that by turning the cock the operator was placed in connexion with the empty bell-jar, and during an inspiration of fresh air the cock was turned, when the expired air was directed into that bell-jar. The rate of breathing had now become all but natural, or the same as at the beginning of the experiment, giving indications the effects of re-breathing had apparently passed away ; this question was to be settled by the analyses. There were consequently four different samples of expired air to be submitted to analysis for the determination of the carbonic acid they contained. The first sample was frbm air expired normally, the second from air re-breathed, the third from air expired immediately after re-breathing, the fourth from air expired after apparent recovery from the effects of breathing impure air. By the time breathing in the closed vessel had commenced, the air expired normally had already been shaken with barium hydrate; 1891.] Phenomena of Human Respiration. 109 samples from the bag and other two bell-jars were treated in the same way. The next day the barium carbonate had subsided, and the clear fluid was titrated according to Pettenkofer's method. The reductions to dryness, to 0° and 760 mm., were speedily made with the help of the table I have given in the paper previously referred to. Let us now follow the changes occasioned by the re-breathing of 35 litres of air for a period of 5 minutes ; there were a few additional seconds included, as the re-breathing had to be stopped at the end of an expiration, which of course might not exactly correspond with a lapse of five minutes. The following are the mean percentages of C03 contained in the bell-jar after its air had been re-breathed : — Myself. after 5 m. 2 sec. 3'42 per cent C02. Mr. Russell „ 5m. 4 sec. 3'87 „ „ Mr. Hoskins ,, 5 m. 10 sec. 3'44 ,, „ W. Alderwood ,, 5 m. 5 sec. 3*29 „ ,, consequently in every case the air was becoming considerably vitiated ; yet it was only in the last minute that an unpleasant sensa- tion, if any, was felt. If we compare the amount of carbonic acid expired by re-breathing 35 litres of air for five minutes with the amount of carbonic acid which would have been expired in the same time in ordinary breath- ing, we find invariably less C02 in the re-breathed air than in rormal respiration ; this is shown clearly in the following table, in which the C02 expired in ordinary breathing has been calculated for the time taken in the re-breathing stage of the experiment. Time. CO2in re- breathed air. CO2 expired normally in same time. Relations of CO2 ex- pired in re-breathed air to CO2 expired in natural breathing. Myself 5 m. 2 sec. 2 '135 2-224 1 to 1 -041 Mr. Russell 5 m. 4 sec. 2-418 2-797 1 to 1 -157 Mr. Hoskins 5 m. 10 sec. 2-151 2-428 1 to 1 -221 W. Alderwood. . . . 5m. 5 sec. 2-066 2-221 Ito 1-075 Mean 5 m. 5 sees. 2-192 2-417 1 to 1 -123 It follows that there is always less carbonic acid expired in a given time when air is re-breathed than in ordinary breathing. In the present experiments the mean proportions varied for four different persons between 1 to 1-041 and 1 to V221 ; or, in other words, a mean of 9*3 per cent, carbonic acid which would have been expired in a certain time in ordinary breathing is found to have disappeared in 35 litres of air re-breathed during the same time. I 2 110 Dr. W. Marcet. On the Chemical [Jan. 15, [This amounts to 225 c.c. C03, which have been retained in the blood ; but it occurs to me that less oxygen may possibly be consumed from re-breathed air than from fresh air, although in my experiments re-breathing is hardly carried far enough to admit of such a contin- gency.— Jan. 22.] We find, by a consideration of the next table, that the reduced elimination of carbonic acid in re-breathed air is regulated in a marked degree by the weights of C02 expired in ordinary breathing. COj produced by re-breatlung. COj eipired in ordinary breathing in the same time. W. Alderwood 2 '066 grams 2 '221 grams Myself 2-135 , 2 '224 Mr. Hoskins ........ 2 -151 2-428 Mr. Russell 2-418 2-797 Thus it is seen that the CO2 in re-breathed air and in ordinary breathing increase together from the lowest to the highest figures. This might have been expected, as the whole experiment must be con- trolled more or less by the phenomena of ordinary breathing for each of the persons under experiment. There is another point of interest to be noticed with reference to the re-breathed air in the present experiment — the volume of this air, which originally was 35 litres, is no longer 35 litres at the con- clusion of the experiment, but has undergone a slight reduction. The enquiry into this portion of the subject was not found so simple as it appeared to be at first, and, as the work progressed, precautions against errors had to be taken which had not been apparent until a late period of the investigation. I, therefore, prefer to leave this part of the subject for future consideration. It has been stated that after re-breathing for five minutes the air of the bell-jar, and then admitting fresh air into the lungs, an in- creased volume of air was inhaled attended with the expiration of a greater amount of carbonic acid than in ordinary breathing. This will be seen in the following table, showing, for the same lapse of time, the mean results obtained on four different persons for ordinary respiration and while inhaling fresh air, immediately after the re- breathing stage of the experiment. A consideration of these tables shows, with reference to the C03 expired, that there was invariably an excess, after re-breathing air for five minutes, over the weight expired in the same time in normal respiration; the mean relation being 1 to T237. In the case of 1891.] Phenomena of Human Respiration. Ill C02 before re-breathing calculated on time after re-breathing. Time. Before re-breathing. CO2, grams. After re-breathing. CO2, grams. Relation. Self 5 m. 40 sec. 2-474 3-134 1 to 1 -267 Mr Russell 4 m. 41 sec. 2-507 3-224 1 to 1 -294 Mr. Hoskins. • . • • . 5 m. 26 sec. 2-802 3-614 1 to 1 '290 W. Alderwood .... 6 m. 57 sec. 3-018 3-311 1 to 1 -097 Mean ...... 5 in. 41 sec. 2-700 3-326 1 to 1 -237 Litres of Air expired before re-breathing calculated on time after re-breathing. Before re-breathing. After re-breathing. Relation. 26-56 24-96 26-24 29-17 33-93 35-70 35-27 34-34 1 to 1 -278 1 to 1 -430 1 to 1 -344 1 to 1-177 26-73 34-81 Itc 1-307 W. Alderwood, who was the least affected of the four persons under experiment, the excess of C02 after re-breathing, amounting to 1 to 1'097, is the smallest. A similar remark applies to the volumes of air expired ; they are invariably increased after re-breathing, or while the person under experiment is still under the influence of the want of air ; the mean relation is 1 to 1'307 ; again, in the case of W. Alderwood the increase is the smallest, the proportion amounting to 1 to 1-177. The excess of C02 and of air expired when fresh air is breathed immediately after the re-breathing stage of the experiment must be due in a great measure to the increased amount of carbonic acid retained in the blood, together with an instinctive desire of taking into the lungs increased volumes of air, in order to rid the blood of the carbonic acid it has retained. We now have to deal with the air expired finally or in the bell-jar filled at the termination of the experiment. The mean volumes of air and weights of C02 expired per minute will be seen to approxi- mate to the corresponding volumes and weights expired in ordinary breathing to such an extent that respiration may be considered as having returned to the normal condition. 112 Dr. W. Marcet. On the Chemical [Jan. 15, Table showing the Volumes of Air and Weights of C03 expired in the final stage of the experiment compared with the corresponding volumes and weights expired normally. Self Vol. air expired per minute unreduced. Weight CO, expired per minute. Difference. Normal. Last stage of experi- ment. Normal. Last stage of experi- ment. Vols. air. Weights. 4-687 5-195 4-954 4-197 4-935 5-546 4-986 4-276 0-442 0-552 0-470 0-437 0-457 0-550 0-454 0-422 + 0-248 + 0-351 + 0-032 + 0-079 + 0-015 -0-002 -0-016 -0 -015 Mr. Kussell . .. Mr. Hoskins . . W. Alder wood. Means 4-758 4-936 0-475 0-471 + 0-178 = 3-6 per cent, increase vol. air. -0-004 This table shows unmistakably that the respiration had again become normal before or by the end of the last stage of the ex- periment ; the C02 is all but exactly the same, while there is a very slight increase by 3'6 per cent, in the volume of air expired, indicat- ing that there was perhaps an instinctive tendency to continue breathing a volume of air slightly larger than usual, although the COo expired was the same as in normal respiration. The following are the results obtained from the present inquiry : — 1. On re-breathing air in a closed vessel less carbonic acid is expired within a given time than in ordinary breathing. 2. Those persons who emit most CO2 in re-breathed air are those who expire most air and COo in the same time in ordinary breathing, and mce versa 3. On re-breathing 35 litres of air in a closed vessel for a period of five minutes, the volume of this air undergoes a slight reduction. 4. When fresh air is taken into the lungs immediately after re- breathing air in a closed vessel, the volumes of air breathed and weights of C02 expired are greater than in ordinary breathing. 5. The effects produced on the chemical phenomena of respiration by re-breathing 35 litres of air in a closed vessel for a period of five minutes have passed away in less than six minutes after the breathing of fresh air has been resumed. It may be added that the number of experiments is insufficient to admit of any inquiry into the influence of barometric pressure on respiration. The tables showing the general results of the experiments are as follows : — 1891.] Phenomena of Human Respiration . 113 et-l j,«g CO CO rH rH CO CD OS __; O 5$ rt OS O CO t^ O CO 00 |"S ^I'fl OS OS O OS OS O rH rH oj I'l s-s-sc? §O N o US US ^ US US •<*! us 1 rH 1> .2 ^00 O CO OS 'M 00 y -^ us us i> oo w us S § ft'g bCO O O O O O 0 ^ llt-^d «s •S P/§ g §30 CO US CM CD CO 99 oo 03 a S 'd !•< -s 2 •1^* rH .I** CO X>» rH cp 11 ^. .g 1 1 H fi ^.a-|J os os os os os o rH os ii a as 1110" rH US CO 00 rH US J j"l aoo o o o o o o T5 IP^il . rH CO rH (M rH CO 0 {^1 ^ rH _^ ?H ^ rH CO US 00 CO ^j4 1 r< ~ S | * ® o -rt S co co co co co eo eo E PJ r» ^3 «5 60 2 O ' ^ O 00 Q OS OS OS 00 CO rH O -* O rH O rH US US US US US US CD rH US a fl >^ "o £ O g a 5 « 3 ^ i> co us os co eo s °|1|&'a 6CO O O O O O 0 03 w . p us p oo us .cp 2 1> us ^ oo os oo Q co ** -^i us us us us US us "1 a (M US t» 00 N CO co us rH .2 CC CO US CO CO CO co a t^5© a< rH IN eo •*? us co S3 • °0 3 114 Dr. W. Marcet. On the Chemical [Jan. 15T "S 1U il . "C ® O5CVC". OSOJOC5OSOO o I >o ooooooooo b ~f „. \ ~ f. ,. C. O 05 O5 G} O . >0 I 8 { oo i» t» t» op ^- i> t~ 10 ooooooooo b b §> 3 I v 10 OO• aoaoocoooooiooooaoo ao iO kQ N e? jb oboobbboo o .— j- ; i- •-. -M i- j^ ri r: o c • • ° ** t^St^t^t^t^t*^^ ooiaot^cooioiat^ 11 §1 r j illll *i S M ^9 - w. » -? l> . t£.S cO §0 i K d, II 1891.] Phenomena of Human Respiration. 1 I '4 & a' IM O 4¥ assss^gg ss eo b»£'S,l OCSOOO5Or-li-l iOO 0 •§ § 38* II >- -ti _J c« » a oO SS^SfeSS^ ifeS eo CJ S H .= 0 <* « M Igftj SDO ooooooo* oo o 1 iljfc|£ JO ajNCOjO^OOCOjH o 04 K .2 * 1 3 "•§ I O OO5O5O--IOOOO o ^ 60 J>*o •" ,0 1~l li *^ -S-5 *• « a oQ 8 gg883Sg§?§ S W. ^.XOXOiO^^^^^ * o -9 |£ 'a, il siiiiiSil co 1-1 co I m MO OOOOOOOOO o 1 * -*3 -?* ^ rt O i © § o g -g ri slgg^fe^^SS^^S 5 i £ CU ^ — co 1 f £ I7| 1*1 — ~— r: £ S t- ocouswiOOcoeooo o IO olumes rec •2 ^-^1, ;, Occacjo.co.53?o^g co o» § 1 '3s2 OOO5O5O5O5i-iOOiOC5 1— 1 1— 1 1— < 1— i I— 1 O5 I • 0 CO 1 ig 1 1 g 1 1 g 1 1 a s •4 to ^ »• N»0^aOOtf>NOOOiO co 31 °§^§S§^SS2SS S i-f I— 1 1— 1 a 116 Chemical Phenomena of Human Respiration. [Jan. 15, o 1* - C a. •3 «"? -S Itfi «• ^* ^J* ^* ^r ^f "^ CO CO ^* 00 &CO OOOOOOOOO 1 1 X 0) 13 S 'O i 2.S 11 XOOC5OJC5C2C5O5C1 g"3d £ t-0 a - *, CXO OOOOOOOOO I 2 .is - S^ cf .; J5-3.sgs 2 «•£ S c^= •s. s • «B Sao ST. rr OOOOOOOOO ff 31 S 1891.] Presents. 117 The foregoing tables suggest the following remark : — " The volumes of air expired for 1 gram CO2 immediately after re-breathing air vary but slightly from the corresponding volumes of air emitted in ordinary breathing ; in every case except one, the volumes of air are & little higher immediately after re-breathing." Presents, January 15, 1891. Transactions. Birmingham: — Mason Science College. Calendar, 1890-91. 8vo. Birmingham 1890. The College. Bordeaux : — Societe de Medecine et de Chirurgie. Memoires et Bulletins. 1889. Fasc. 3-4. 8vo. Bordeaux 1890. The Society. Boston : — American Academy of Arts and Sciences. Proceedings. New Series. Vol. XVI. 8vo. Boston 1889. The Academy. Breslau: — Schlesische Gesellschaft fur Vaterlandische Cultur. Jahresbericht. 1889. 8vo. Breslau 1890. The Society. Brighton : — Brighton and Sussex Natural History and Philosophi- cal Society. Abstracts of Papers read, together with Annual Report, 1888-90. 8vo. Brighton. The Society. Brooklyn: — Brooklyn Library. Thirty-second Annual Report. 8vo. Brooklyn 1890. The Library. Brussels : — Societe Royale Malacologique de Belgique. Annales. Tome XXIV. 8vo. Bruxelles 1889 ; Proces-Verbaux. Tome XVIII. Tome XIX. Janvier— Aout. 8vo. Bruxelles 1889-90. The Society. Buitenzorg : — 'S Lands Plantentuin. Mededeelingen. Stuk 7. 8vo. Batavia 1890 ; Verslag. 1889. 8vo. Batavia 1890. The Director. Cambridge, Mass. : — Harvard College. Museum of Comparative Zoology. Bulletin. Vol. XX. No. 3. 8vo. Cambridge 1890. The College. Harvard Univei-sity. Bulletin. Vol. VI. No. 3. 8vo. [Cam- bridge] 1890. The University. Catania : — Accademia Gioenia di Scienze Naturali. Bullettino Mensile. Fasc. 13-14. 8vo. Catania 1890. The Academy. Copenhagen : — Academic Royale. Memoires (Classe des Sciences). Vol. VII. Nos. 1-3. 4to. Copenhague 1890. The Academy. Cracow : — Academie des Sciences. Bulletin International. Comptes Rendus des Seances. Octobre — Novembre, 1890. 8vo. Cracovie. The Academy. Danzig : — Naturforschende Gesellschaft. Schriften. Bd. VII. Heft 3. 8vo. Danzig 1890. The Society. Presents. [Jan. Transactions (continued). Delft: — Ecole Poly technique. Annales. Tome VI. Livr. 1. 4to. Leide 1890. The School. Dublin : — Royal Irish Academy. " Cunningham Memoirs." No. 6. On the Morphology of the Duck and the Auk Tribes. By W. K. Parker, F.B.S. 4to. Dublin 1890. The Academy. Royal Society of Antiquaries of Ireland. Journal of the Proceedings. Ser. 5. Vol. I. No. 3. 8vo. Dublin 1890. The Society. London : — British Astronomical Association. Journal. Vol. I. Nos. 1-2. 8vo. London 1890. The Association. British Pharmaceutical Conference. Year-Book of Pharmacy and Transactions, 1889-90. 8vo. London 1890. The Editor. Entomological Society. Transactions. 1890. London. Institute of Brewing. Transactions. Vol. IV. London 1890. Institution of Mechanical Engineers. No. 3. 8vo. London. Part 4. 8vo. The Society. No. 2. 8vc The Institute. Proceedings. 1890. The Institution. London Mathematical Society. Proceedings. Vol. XXI. Nos. 377-380. 8vo. [London] 1890. The Society. Odontological Society of Great Britain. Transactions. Vol. XXIII. No. 2. 8vo. London 1890. The Society. Photographic Society of Great Britain. Journal and Trans- actions. Vol. XV. No. 3. 8vo. London 1890. The Society. Royal Institute of British Architects. Transactions. Vol. VI. 4to. London 1890. The Institute. Royal Medical and Chirurgical Society. Medico-Chirurgical Transactions. Vol. LXXIII. 8vo. London 1890. The Society. Royal United Service Institution. Journal. Vol. XXXIV. No. 154. 8vo. London 1890. The Institution. Society of Biblical Archaeology. Proceedings. Vol. XIII. Part 2. 8vo. London 1890. The Society. Milan : — Reale Istituto Lombardo di Scienze e Lettere. Memorie (Classe di Lettere e Scienze Storiche e Morali). Vol. XVII. Faec. 2. Vol. XVIII. Faac. 2. 4to. Milano 1890 ; Rendi- conti. Ser. 2. Vol. XXI-XXII. 8vo. Milano 1888-89. The Institute. Journals. Boletin de Minas Industria y Constmcciones. Ano 6. Num. 3-8. 4to. Lima 1890. La Escuela de Ingenieros, Lima. 1891.J Presents. 119 Journals (continued). Canadian Record of Science. Vol. IV. No. 4. 8vo. Montreal 1890. Natural History Society, Montreal. Galilee (Le) 1890. Nos. 11-12. 8vo. Pam 1890. The Editor. Horological Journal. Vol. XXXIII. Nos. 388-389. 8vo. London 1890-91. British Horological Institute. Nature Notes. Nos. 11-32. 8vo. London 1890. The Editors. Naturalist (The) No. 185. 8vo. London 1890. The Editors. Revista do Observatorio. Anno 5. Num. 10-11. 8vo. Eio de Janeiro 1890. The Observatory, Bio de Janeiro. Revue Medico-Pharmaceutique. Annee 3. Nos. 6-12. 4to. [Con- stantinople] 1890. The Editor. School Calendar (The) 1890. 8vo. London, Messrs. Bell and Sons. Scientific Memoirs by Medical Officers of the Army of India. Part 5. 4to. Calcutta 1890. The Government of India. Stazioni Sperimentali Agrarie Italiane (Le) Vol. XVIII. Fasc. 6. Vol. XIX. Fasc. 1-5. 8vo. Asti 1890. R. Stazione Enologica, Asti. Symons's British Rainfall, 1889. 8vo. London 1890. Mr. G. J. Symons, F.R.S. Technology Quarterly. Vol. III. Nos. 2-3. 8vo. Boston 1890. Massachusetts Institute of Technology, Boston. University Studies. Vol. I. No. 3. 8vo. Lincoln (U.S.) 1890. The University of Nebraska. Victorian Year-Book. 1888-89. 8vo. Melbourne 1889. The Government of Victoria. Zeitschrift fur Naturwissenschaften. Bd. LXIII. Heft 2-5. 8vo. Halle 1890. Naturwissenschaftlicher Verein, Halle. Bronze Medallion Portrait, commemorative of J. E. Gray, F.R.S. , and M. E. Gray. Mr. W. T. Thiselton Dyer, F.R.S. 120 Mr. T. Andrews. [Jan. 22, January 22, 1891. THE ASTRONOMER ROYAL, V.P.R.S., in the Chair. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read : — I. " On the Unsymmetrical Distribution of Terrestrial Mag- netism." By HENRY WILDE, F.R.S. Received Novem- ber 20, 1890. [Publication deferred.] II. "The Passive State of Iron and Steel. Part II." By THOS. ANDREWS, F.R.SS.L. and E., M.Inst.C.E. Received October 24, 1890. In Part I of this research ('Roy. Soc. Proc,,' vol. 48, p. 116), the author showed the influence of magnetisation on the passive state of iron and steel, and he has now the pleasure of communicating to the Royal Society the results of a further study of certain temperature and other conditions affecting the passivity of these metals in con- centrated nitric acid. The experiments of Series III, in this paper, relate to the effect of temperature, and the observations of Series IV refer to the influence exerted by nitric acids, of varied concentration, on the passive condition of iron and steel. SERIES III. Effect of Temperature on the Passivity of Iron and Steel. The bars selected for these observations were unmagnetised polished rods, which had been previously drawn cold through a wortle ; a pair of bars of each metal were cut adjacently from one longer bar, and then placed securely in the wooden stand, W ; each bar was 8 j- inches long, 0'261 diameter. The JJ-tube containing 1^ fluid oz. of nitric acid, sp. gr. 1'42, was rigidly placed in an arrangement as shown on fig. 3. One limb, A, was surrounded by a tank containing water, the other limb, B, by a tank of the same capacity, containing powdered ice; the arrangement was such that the water-tank could be heated by a 1891.] 1 he Passive State of Iron and Steel. 121 Bunsen burner, and its temperature slowly raised, whilst the ice-tank was kept full of powdered ice. A non-conductor of wood was put between the ends of the two tanks so as to prevent the melting of the ice ; the bottom or bent portion of the (J -tube was also enclosed in a thick non-conductor of wood. A thermometer, T, was placed in the water-tank. The bars were in circuit with the galvanometer, and soon after immersing them in the nitric acid heat was applied to the water-tank, and the temperature of the nitric acid in that limb of the U -tube slowly raised to the temperatures required, whilst the acid in the other limb of the U^ube was meanwhile maintained at a tem- perature of 32° F. The arrangement will be understood on reference to fig. 3, and the electro-chemical results obtained are graphically recorded on> Diagram L FIG. 3. 122 Mr. T. Andrews. DIAGRAM I. [Jan. 22, Current between two bright " passive " bars of the same composition, one in warm, the other in cold, nitric acid sp. gr. 1*42. The electro-chemical position of the bar in the warm nitric acid was positive. •••••••••••••••••••I iM •••••••••••mi •*• S ••"*• £ 0-04 •»••••••••• •••••! !••••••••••••••! ••••••••••••••I •••••••••••••••I ••••••••••••••I ••••••••••••••I «••••••••••! •••••••••••I • •••••••I ••••••••I \ys iKSssssrr ••*•••• mmmtm\ ••••••'!••• mmmmmwmmmm* •rin Miam tin •• • !«• I mA 1PSHI (••••ft m ••••••IB • IBUBI liBBiiiiiiii Difference of temperature between the nitric acid in Tubes A and B, see Fig. 3, in degrees Fahrenheit. Curre A gives the E.M.F between two wrought iron bars, and Curve B gives the E.M.F. between two cast steel bars under the conditions recorded. The above experiments indicate that the wrought iron was less passive in wnrm nitric acid than the soft cast steel ; the average E.M.F. of 94 observations with wrought iron was 0*030 volt ; whereas, in the case of the 94 observations on cast steel, the average E.M.F. was only O'OIO volt. It will be seen from the above diagram that the behaviour of the steel, under the conditions stated, was more irregular than that of the wrought iron. In the whole of the above series of experiments on Diagram I the nitric acid was raised to a temperature of 175° F. ; the cold nitric acid in the limb of the JJ-t-ube A remained perfectly colourless, and the steel or iron therein absolutely passive ; but the steel or iron in the warm nitric acid in tube A commenced to be gradually acted upon as the temperature increased, a pale yellow tint beginning to appear in 1891.] The Passive State of Iron and Steel. 123 the solution in the tube A shortly after commencement. Wben the temperature of about 170° to 175° P. was reached a faint evolution of gas in the form of bubbles was manifest, adhering to the steel, in the warm tube only. No powerful solvent action or violent evolution of nitric oxide gas, however, occurred in any of these experiments even up to the temperature of 175° F., and these experiments were not continued beyond this temperature. These results show that iron or steel does not fully lose its passivity up to a temperature even of 175° F., though the passivity is shown to have been considerably modified by temperature only. The critical point of temperature of transition from the passive to the active state is therefore higher than 175° F., and is shown in the experiments of Part I, Series II, Table II, to have been about 195° F. SERIES IV. The Passivity of Iron and various Steels increases with the Concentration of the Nitric Acid. Schonbein considered that, " by immersing an iron wire in nitric acid 1'50 sp. gr., it became likewise indifferent to the same acid of T35 sp. gr.," and to all outward appearance this is so. Scheurer-Kestner considered that the passivity of iron was not de- pendent on the greater or less degree of saturation of the acid. The author, however, ascertained by the delicate electro-chemical mode of experimentation employed, and hereafter referred to, that the pas- sivity is materially influenced according to the concentration of the nitric acid. The following experiments indicate that the property of passivity in iron is not absolutely fixed or static, but that its passivity is modi- fied to a certain extent in relation to the strength of the nitric acid used. The general modus operandi was generally similar to that pre- viously employed. Pairs of unmagnetised polished steel bars 6 inches long, and 0'310 inch diameter, each pair be"ing of the same kind of steel, and cut adjacently from one longer bar, were placed as before in the wooden frame W, fig. 4, and then instantly and simultaneously immersed in nitric acids, of two different degrees of concentration, contained in the U't°be arrangement, one limb of the U'^11^6 con- taining red fuming nitric acid of sp. gr. 1'50, the other containing nitric acid of sp. gr. T42, circuit being made through the galvano- meter in the usual manner. The results, the average of repeated, experiments in each case, are given on Table III, and show that the passivity of iron increases considerably with the strength of the nitric acid. VOL- XLIX. 124 Mr. T. Andrews. Table III. [Jan. -1-1. Current between two bright "pa««ve" wrought iron or various steel bars of the same composition, one in cold nitric acid sp. gr. 1*50, the other in cold nitric acid sp. gr. r 12. The electro-chemical position of bar in weaker acid positive, except Time otherwise stated. from E.M.F. in volt. com- mence- in. 'lit of ex- periment. Wrought iron. Soft cast steel, combined carbon Hard ca«t steel, combined carbon Soft Bessemer steel, combined carbon Tungsten steel, combined carbon 0-57 per cent. 1-60 per cent. 0'55 per cent. 1'75 per cent. seconds. 0 0-086 0-041 0-055 0-055 0-038 30 0-077 0-040 0-055 0-052 0-038 miiiutes. 1 0-076 0-036 0-054 0-053 0-041 2 0-074 0-036 0-053 0-056 0-043 3 0 073 0-038 0-053 0-058 0-048 4 0-072 0-040 0-052 0-060 0-048 5 0-072 0.0 tl 0-052 0-061 0-049 n 0-071 0-041 0-050 0-067 0-050 10 0-069 0 041 0-049 0-071 0-050 15 0-066 0-040 0-048 0-074 0-U50 20 0-064 0 037 0-046 0-077 0-049 25 0-002 0-035 0-043 0-074 0-0 19 30 0-060 0-034 0-042 0-072 0-048 35 0-059 0-033 0-040 0-071 0 048 40 0-058 0-031 0-038 0-071 0-047 45 0-056 0-030 0-038 0-070 0-047 50 0-055 0-029 0-036 0-068 0-046 55 0-054 0-029 0-036 0-067 0-046 hours. 1 0-053 0-028 0-035 0-066 0-045 11 0-051 0-025 0-034 0-061 0-044 2 0-049 0-022 0 033 0-058 0-043 2* 0-048 0-020 0 -033 0-055 0-041 3 0 047 0-019 0-033 0-052 0-041 4 0-046 0-018 0-034 0-050 0-043 5 0-043 0-017 0-OH4 0-049 0-040 6 0-041 0 016 0-034 0-048 0'038 7 0-041 0 013 0-034 0-047 0-037 8 0-041 0-013 0-034 0-047 0-037 16 0 040 0-009 0-030 0-017 0-037 18 0-040 0-006 0-029 0-046 0-037 20 0 040 0-008 0-029 0-046 0-038 21 0 040 0-029 0-031 0-040 22 0-040 0 024 0-031 24 0-038 0-019 0-013 26 0-038 0-016 0-013 28 0-039 0-013 0-013 29 0-038 0-012 0-013 30 0-040 0-011 0-013 40 0-042 0-006 0 024 45 0-034 1891.] The Passive State of Iron and Steel. FIG. 4. 125 The steel rods selected for this set of experiments were of the kinds given on Table IV ; they were drawn cold through a wortle, and were of the general physical properties and chemical composition given on Tables IV and V. The reduction of E.M.F. towards the close was probably owing to partial diffusion between the two acids of different concentration. The above results show that wrought iron was less passive in the weaker acid than most of the steels, the soft Bessemer steel being found similar in passivity to the wrought iron. The average E.M.F. was as follows : — With wrought iron, 0'054 volt ; soft cast steel, 0'028 volt ; hard cast steel, 0*036 volt ; soft Bessemer steel, 0'059 volt ; tungsten steel, 0'039 volt. (26 The Passive State of Iron and Steel. [Jan. ~2: | o | 8?888 0 H e 1 •8 8 c Ii „• ss fe a S ^"3 -"3 §gg o^a * £ £ e^ £ a |£ *• 8 8828 • 00 •< e| *J CO »» U5 l>- h- <£> X -f 7^ ~* g -*^O 005 1 1 B O ».- J £§ IH O SI » SO _ : i _ — i - 9 £. § .5 B c 0 . «- •= V O> Oft O5 d UO .2* *• . .: "S N e j s J 1— 1 >— 1 pH t— b 'o b b s m a ! ::::? 2 £3 ja 1 5 •** c 3*1" B fi CO i|||i o ES a — — C4 H •a •§ « OS OJ O 00 N O » c p 1 ^ * B £ r-l t^ CO «0 O *>. •* 00 ^ 'N O «H .-1 N l> 1 S 1 1 OT — r. i B g, O O O O O 1 - — u i Q -si o boo H | So co '* >o O CO tO •>! t^ 80 00 1 ^ B J S § £ oj 2 B SO . £ : a f Q Wrought iron (Wo Soft cast steel Hard cast steel .... Soft Bessemer steel. Tungsten steel "S js * 3 * ^ 2 5 • 2 c r- 1 Q Wrought iron (Wort Soft cast steel Hard cast steel Soft Bessemer steel . Tungsten steel 1891.] Presents. . 127 Presents, January 22, 1891. Transactions. Baltimore : — Medical and Chirurgical Faculty of the State of Maryland. Transactions. Session 92. 8vo. Baltimore 1890. The Faculty. Boston : — Society of Natural History. Memoirs. Vol. IV. Nos. 7-9. 4to. Boston 1890; Proceedings. Vol. XXIV. Parts 3-4. 8vo. Boston 1890. The Society. Brussels : — Academic Royale des Sciences, des Lettres et des Beaux-Arts de Belgique. Annuaire. 1891. 8vo. Bruxelles. The Academy. Cambridge, Mass. : — Museum of Comparative Zoology, Harvard College. Annual Report, 1889-90. 8vo. Cambridge 1890. The Museum. Colombo: — Museum. Reports of the Director, 1888-89. Folio. \_Colombo.~] The Museum. Copenhagen : — Academic Royale. Bulletin. 1890. No. 2. 8vo. Copenliague, The Academy. Edinburgh: — Botanical Society. Transactions. Vol. VIII — XVII. 8vo. Edinburgh 1866-89. The Society. Royal Society. Proceedings. Vol. XVII. Pp. 129-192. 8vo. [Edinburgh 1890.] The Society. Essex Field Club. The Essex Naturalist : Journal of the. Vol. IV. Nos. 4-9. 8vo. Buckhurst Hill 1890. The Club. Leipsic : — Astronomische Gesellschaft. Vierteljahrsschrift. Jahrg. 25. Heft 2-3. 8vo. Leipzig 1890; Catalog der Astronomisch en Gesellschaft. 1. Abtheil. Zone + 1° bis + 5° ; Zone +55° bis +65°. 2 Parts. 4to. Leipzig 1890. The Society. Konigl. Sachs. Gesellschaft der Wissenschaften. Abhandlungen (Math.-Phys. Classe). Bd. XVI. Nos. 1-2. 8vo. Leipzig 1890; Abhandlungen (Philol.-Histor. Classe). Bd. XI. No. 7. 8vo. Leipzig 1890 ; Berichte. (Math.-Phys. Classe) 1890. Nos. 1-2. 8vo. Leipzig ; Berichte (Philol.-Histor. Classe). 1890. No. 1. 8vo. Leipzig. The Society, London : — Pathological Society. Transactions. Vol. XLI. 8vo. ' London 1890. The Society. Milan: — Societa Italiana di Scienze Natnrali. Atti. Vol. XXXI. Fasc. 1-4. Vol. XXXII. Fasc. 1-4. 8vo. Milano 1888-89. The Society. Moscow : — Societe Imperiale des Naturalistes. Bulletin. 1890. No. 2. 8vo. Moscou. The Society. K 2 128 t Present*. [Jan :>2, Transactions (continued). Nottingham : — University College. Calendar. 1890-91. 8vo. Nottingham. The College. Paris: — Museum d'Histoii-e Natnrelle. Nouvelle Archives. Ser. 3. Tomes 1-2. Fasc. 1-2. 4to. Paris 1889-90. The Museum. Societe Entomologique de France. Annales. Ser. 6. Tome IX. Nos. 1-4. 8vo. Pom 1890. The Society. Societe" Franchise de Physique. Seances. Mai — Juillet, 1890. 8vo. Paris. The Society. Socie"te" Geologique de France. Bulletin. Ser. 3. Tome XVI. No. 11. Tome XVIII. Nos. 1-4. 8vo. Paris 1888-90. The Society. Penzance : — Royal Geological Society of Cornwall. Transactions. Vol. XI. Part 4. 8vo. Penzance 1890. The Society. Philadelphia : — Academy of Natural Sciences. Proceedings. 1890. Part 2. 8vo. Philadelphia. The Academy. Prague : — Konigl. Bohmische Gesellschaft der Wissenschaften. Abhandlungen (Math.-Naturw. Classe). Folge 7. Bd. III. 4to. Prag 1890 ; Abhandlnngen (Philos. Geschicht. n. Philol. Classe). Folge 7. Bd. III. 4to. Prag 1890. The Society. Rome : — Accademia Pontificia de' Nuovi Lincei. Atti. 1890. Sessione 3. 4to. Roma. The Academy. Turin : — Reale Accademia delle Scienze. Memorie. Ser. 2. Tomo XL. 4to. Torino 1890. The Academy. Vienna : — Anthropologische Gesellschaft. Mittheiluugen. Bd. XX. Heft 1-2. 4to. WienlSW. The Society. K. Akademie der Wissenschaften. Anzeiger. 1890. Nos. 12-24. 8vo. Wien. The Academy. K.K. Geologische Reichsanstalt. Abhandlungen. Bd. XV. Heft 2. 4to. Wien 1890 ; Jahrbuch. Bd. XL. Heft 1-2. 8vo. Wien 1890; Verhandlungen. 1890. Nos. 6-13. 8vo. Wien. The Institute. Observations and Reports. Adelaide : — Botanic Garden. Report on the Progress and Condi- tion of the Garden. 1889. Folio. Adelaide 1890. The Direct Post Office and Telegraph Department. Rainfall in South Australia and the Northern Territory during 1887, with Weather Characteristics of each month. Folio. Adelaide. 1888 ; Report on the Telegraphic Determination of Australian Longitudes. Folio. [Adelaide 1886.] The Department. 1891.] Presents. 129 )bservations, &c. (continued). Albany : — University of the State of New York. Annual Report of the Regents of the New York State Library for the year ending September 30, 1889. 8vo. Albany 1890 ; Annual Reports of the New York State Museum of Natural History, 1887-89. 8vo. Albany 1888-90. The University. Berlin : — Stern warte. Circular. No. 334. 8vo. Berlin 1890. The Observatory. Bombay : — Colaba Observatory. Report for the year ended June 30, 1890. Folio. [Bombay] 1890. The Observatory. Meteorological Office. Brief Sketch of the Meteorology of the Bombay Presidency in 1889-90. Folio. Bombay. The Office. Brisbane : — Registrar- General's Office. Statistics of the Colony of Queensland for the year 1889. Folio. Brisbane 1890; Vital Statistics, 1889. Folio. Brisbane 1890. The Registrar- General. Columbus : — Ohio Meteorological Bureau. Report for September, 1890. 8vo. Columbus. The Bureau. Cordova : — Observatorio Nacional Argentine. Resultados. Vol. XII. 4to. Buenos Aires 1890. The Observatory. Edinburgh : — Royal Observatory. Circular. No. 12. 4to. [Sheet] 1890. The Observatory. Geneva : — Observatoire. Resume Meteorologique de 1'Annee 1889. 8vo. Geneve 1890. The Observatory. India : — Geological Survey. Records. Vol. XXIII. Part 4. 8vo. Calcutta 1890. The Survey. Milan: — Reale Osservatorio di Brera. Pnbblicazioni. No. 37. 4to. Milan 1891. The Observatory. Montevideo : — Observatorio Meteoroldgico del Colegio Pio de Villa Colon. Boletin Mensual. 1890. Nos. 6-7, 11. 8vo. Monte- video. The Observatory. Moscow : — Observatoire. Annales. Ser. 2. Vol. II. Livr. 1-2. 4to. Moscou 1890. The Observatory. Paris : — Bureau International des Poids et Mesures. Travaux et Memoires. Tome VII. 4to. Paris 1890 ; Comptes Rendus des Seances de la Premiere Conference Generale des Poids et Mesures, 1889. 4to. Paris 1890. The Bureau. Ministere des Travaux Publics. Service des Topographies Sou- terraines. Etudes des Gites Mineraux de la France. Bassin Houiller et Permien d'Autun. Fasc. 2. Flore Fossile. Premiere Partie. Texte et Atlas. 2 vols. 4to. Paris 1890. Ministere des Travaux Publics, Paris. K 3 ISO Prof. G. H. Darwin. [Jan. L'(.», January 29, 1891. Sir WILLIAM THOMSON, D.C.L, LL.D., President, in the Chair. The Presents received were bud on the table, and thanks ordered for them. The Bakerian Lecture was delivered as follows: — BAKERIAX LECTURE. — *• On Tidal Prediction." By G. H. DARWIN, F.R.S., Plumian Professor and Fellow of Trinity College, Cambridge. Received December lli, iKiH). (Abstract.) At most places in the North Atlantic the prediction of high and low water is fairly easy, because there is hardly any diurnal tide. This abnormality makes it sufficient to have a table of the mean fortnightly inequality in the height and interval after lunar transit, supplemented by tables of corrections for the declinations and parallaxes of the disturbing bodies. But when there is a large diurnal inequality, as is commonly the case in other seas, the heights and intervals, after the upper and lower lunar transits, are widely different ; the two halves of each lunation differ much in their cha- racters, and the season of the year has great influence. Thus simple tables, such as are applicable in the absence of diurnal tide, are of no avail. The tidal information supplied by the Admiralty for such places consists of rough means of the rise and interval at spring and neap, modified by the important warning that the tide is affected by diurnal inequality. Information of this kind affords scarcely any indication of the time and height of high and low water on any given day, and must, I should think, be almost useless. This is the present state of affairs at many ports of some importance, but at others a specially constructed tide-table for each day of each year is published in advance. A special tide-table is clearly the best sort of information for the sailor, but the heavy expense of prediction and publication is rarely incurred except at ports of first- rate comme cial importance. There is not, to my knowledge, any arithmetical method in use of computing a special tide table which does not involve much work and expense. The admirable tide-predicting instrument of the Indian 1891.] On Tidal Prediction. 131 Government renders the prediction comparatively cheap, yet the instrument can hardly be deemed available for the whole world, and the cost of publication is so considerable that the instrument cannot, or at least will not, be used for many ports at remote places. It is not impossible, too, that national pride may deter the naval authorities of other nations from sending to London for their predictions, although the instrument may, I believe, be used on the payment of certain fees. The object, then, of the present paper is to show how a general tide table, applicable for all time, may be given in such a form that any one with an elementary knowledge of the Nautical Almanac may, in a few minutes, compute two or three tides for the days on which they are required. The tables are also such that a special tide- table for any year may be computed with comparatively little trouble. Any tide-table necessarily depends on the tidal constants of the particular port for which it is designed, and it is supposed in the paper that the constants are given in the harmonic system, and are derived from the reduction of tidal observations. Where the obser- vation has been by tide-gauge, the process of reduction is that explained in the Report to the British Association for 1883, but where the observations are only taken at high and low water, a different process becomes necessary. I have given in a previous paper a scheme of reduction in these cases.* At ports not of first-rate commercial importance observation has rarely been by tide-gauge, and thus it is exactly at those ports, where the method of this paper may prove most useful, that we are deprived of the ordinary method of harmonic analysis. On this account I regard the previous paper as preliminary to the present one, although the two are logically independent of one another. In the harmonic method the complete expression for the height of water at any time consists of a number of terms, each of which involves some or all of the mean longitudes of moon, sun, lunar and solar perigees ; there are also certain corrections, depending on the longitude of the moon's node. The variability of the height of water depends principally on the mean longitudes of the moon and the sun and to a subordinate degree on the longitude of lunar perigee and node, for the solar perigee is sensibly fixed. There are, therefore, two principal variables, and two subordinate ones. This statement suggests the construction of a table of double entry for the varia- bility of tide due to the principal variables, and of correctional tables for the subordinate ones ; and this is the plan developed in the paper. The mean longitudes of the moon and sun are not, however, con- venient as variables, and accordingly the principal variables in the * ' Hoy. Soc. Proc.,' 1890, vol. 48, p. 278. 1 :'•:.' On Tidal Prediction. [Jan. 29, tables are the time of moon's transit and the time of year ; whilst the subordinate variables are the moon's parallax and the longitude of her node. The tide-table, then, consists of the interval after moon's transit and height of high and low water, together with nodal and parallactic corrections, computed for every 20™ of moon's transit, and for about every ten days in the year. Each table serves for the two times of year at which the sun's longitude differs by 180°, and they may be used without interpolation. The nodal correctional terms consist of two times and of two heights, which are to be multiplied by the cosine and sine of the longitude of the moon's node, to give the total nodal corrections to the interval and height. The parallactic correc- tional terms consist of a time and a height, which are to be multi- plied by the excess above, or defect below 57' of the moon's parallax at moon's transit to give the total parallactic corrections to the inter- val and height. I had hoped that less elaborate tables might have sufficed, but it appeared that, at a station with very large diurnal inequality, the changes during the lunation, and with the time of year, in the interval and height are so abrupt and so great, that short tables would give very inaccurate results, unless used with elaborate interpolations. It is out of the question to suppose that a ship's captain would or could carry out these interpolations, and it is therefore proposed to throw the whole of that work on to the computer of the table. Such a paper as this can only be deemed complete when an example has been worked out to test the accuracy of the tidal prediction, and when rules for the arithmetical processes have been drawn up, forming a complete code of instructions to the computer. The port of Aden was chosen for the example, because its tides are more complex and apparently irregular than those of any other place which, as far as I know, has been thoroughly treated. The arithmetic of the example was long, and was re-arranged many times. An ordinary computer is said to work best when he is igno- rant of the meaning of his work, but in this kind of tentative work a satisfactory arrangement cannot be attained without a full compre- hension of the reason of the method. I was therefore fortunate ii securing the enthusiastic assistance of Mr. J. W. F. Allnutt, and owe him my warm thanks for the laborious computations he has carried out. After computing fully half the original table, he made a comparison for the whole of 1889 of our predictions with those of the Indian Government. Without going into the details of this com- parison, it may be mentioned that the probable error of the discrepancy between the two tables was 9™ in time, and 1'2 inches in the height of high water ; that there were reasons to expect some systematic difference between the two calculations, and that all the considerable 1891.] Presents. 133 errors of time fall on those very small rises of water which are of frequent occurrence at Aden. I have made two other comparisons, one with the Indian predictions of 1887, and the other with actuality of 1884. In the latter case, when a few very small tides were omitted, the probable error was 7m in the time, and 1'4 inches in height. It is concluded from these compari- sons that, with good values for the tidal constants, the tables lead to excellent predictions, even better than are required for nautical pur- poses. It is probable that this method may be applied to ports of second- rate importance, where there are not sufficient data for very accurate determination of the tidal constants. Suggestions are made for very large abridgment of the tables in such cases, accompanied, of course, by loss of accuracy. The question of how far to go in each case must depend on a variety of circumstances. The most important consideration is, I fear, likely to be the amount of money which can be expended on computation and printing ; and after this will come the trustworthi- ness of the tidal constants, and the degree of desirability of an accu- rate tide-table. The aim of the paper has been to give the tables in a simple form, and if, as seems certain, the mathematical capacity of an ordinary ship's captain will suffice for the use of the tables, whether in full or abridged, I have attained the principal object in view. Presents, January 29, 1891. Transactions. Albany : — New York State Museum of Natural History. Bulletin. Nos. 7-10. 8vo. Albany 1889-90. The Museum. Amsterdam : — Koninklijke Akademie van Wetenschappen. Ver- slagen en Mededeelingen. Afd. Natuurkunde. Deel VI. 8vo. Amsterdam 1889. The Academy. Baltimore : — Johns Hopkins University. Circulars. Vol. X. Nos. 83-84. 4to. Baltimore 1890; Studies from the Biological Laboratory. Vol. IV. No. 7. 8vo. Baltimore 1890 ; Studies in Historical and Political Science. Series 8. Nos. 5-12. 8vo. Baltimore 1890 ; Annual Report of the University. 1890. 8vo. Baltimore. The University. Peabody Institute. Annual Report. 1890. 8vo. Baltimore. The Institute. Basel: — Naturforschende Gresellschaft. Verhandlungen. Bd. IX. Heft 1. 8vo. Basel 1890. The Society. 134 Presents. [Jan. 2« Transactions (continued). Berlin : — Gesellschaft fur Erdkunde. Verhandlnngen. Bd. XVIT. Nos. 8-9. 8vo. Berlin 1890 ; Zeitschrift. Bd. XXV. Heft 5. 8vo. Berlin 1890. The Society. Cambridge, Mass.: — Museum of Comparative Zoology, Harvard College. Bulletin. Vol. XX. No. 4. 8vo. Cambridge 1890. The Museum. Cracow : — Academie des Sciences. Bulletin International. Comptea Rendns des Seances. Decembre, 1890. 8vo. Cracovie 1891. The Academy. Kew : — Royal Gardens. Bulletin of Miscellaneous Information. No. 49. 8vo. London 1891. The Director. London : — British Museum. Catalogue of Printed Books. Leman — Le Prestre, Le Pr6tre — Levakovsky, Victoria — Virgilius. Folio. London 1890. The Trustees. Quekett Microscopical Club. Journal. Ser. 2. Vol. IV. No. 28. 8vo. London 1891. The Club. Montreal : — Fraser Institute. Annual Report. 1889-90. 8vo. Montreal 1890. The Institute. Perugia: — Accademia Medico-Chirnrgica. Atti e Rendiconti. Vol. II. Fasc. 2-3. 8vo. Perugia 1890. The Academy. Santiago : — Deutscher Wissenschaftlicher Vereiu. Verhaudlungen. Bd. II. Heft 2. 8vo. Santiago 1890. The Society. Siena: — R. Accademia dei Fisiocritici. Atti. Ser. 4. Vol. II. Fasc. 3-4, 7-8. 8vo. Siena 1890. The Academy. Stockholm: — Kongl. Vetenskaps Akademie. Ofversigt. Arg. 47. Nos. 4-9. 8vo. Stockholm 1890. The Academy. Sydney : — Australian Museum. Records. Vol. I. Nos. 2-5. 8vo. Sydney 1890; Descriptive Catalogue of the Nests and Eggs of Birds found breeding in Australia and Tasmania. 8vo. Sydney 1889 ; Catalogue of the Australian Birds in the Museum. Part 2. 8vo. Sydney 1890 ; Supplement to tl Catalogue of the Australian Accipitres or Diurnal Birds Prey in the Museum. 8vo. Sydney 1890. The Musec Royal Society of New South Wales. Journal and Proceedinj Vol. XXIII. Part 2. 8vo. Sydney 1889. The Socic Venice : — Reale Istituto Veneto di Scienze, Lettere ed Arti. At Ser. 7. Torno I. Disp. 1-9. 8vo, Venezin. 1889-90. The Institut Vienna: — Anthropologische Gesellschaft. Mittheilnngen. Bd. . Heft 3-4. 4to. Wien 1890. The Socic 1891.] Presents. 135 Observations and Reports. Buda-Pesth : — Konigl. Ungar. Central- Anstalt fiir Meteorologie und Erdmagnetismus. Jahrbiicher. Bd. XVII. 1887. 4to. Budapest 1889. The Institute. India:— Tide Tables for the Indian Ports for 1891. Parts 1-2. 12mo. London. The India Office. I Kiel : — Konigl. Sternwarte. Publication. V. 4to. Kiel 1890. The Observatory. London : — Meteorological Office. Daily Weather Reports (Bound copy) July to December, 1889. 4to. London; Weekly Weather Reports. Vol. VII. Nos. 27-53, with Quarterly Summary. 4to. London; Summary of the - Observations made at the Stations included in the Daily and Weekly Weather Reports. April to August, 1890. 4to. London; Quarterly Weather Report. Part 2. April-June, 1880. 4to. London 1890; Meteorological Observations made at Sanchez (Samana Bay), St. Domingo, 1886--88. 4to. London 1890; Meteorological Observations at Stations of the Second Order for 1886. 4to. London 1890. The Office. Nautical Almanac Office. The Nautical Almanac for 1894. 8vo. London [1890]. The OfEce. Navy Medical Department. Statistical Report of the Health of the Navy. 1889. 8vo. London 1890. The Department. Melbourne: — Mining Department. Annual Report. 1889. Folio. Melbourne ; Report and Statistics for the Quarters ended 31st March and 30th June, 1890. Folio. Melbourne. The Department. Observatory. Monthly Record. January to June, 1890. 8vo. Melbourne. The Observatory. New South Wales : — Geological Survey. Memoirs. Palaeontology. No. 8. 4to. Sydney 1890 ; Records. Vol.11. Parti. 8vo. Sydney 1890. The Department of Mines, Sydney. New Zealand : — Colonial Museum and Geological Survey. Reports of Geological Explorations during 1888-89. 8vo. New Zealand 1890; Studies in Biology for New Zealand Students. 8vo. Wellington [1889] ; Twenty-fourth Annual Report on the Colonial Museum and Laboratory. 8vo. New Zealand 1890; Catalogue of the Colonial Museum Library. 8vo. New Zealand 1890. The Director. Nice : — Observatoire. Annales. Tome II. 4to. Paris 1887. The Observatory. Norway : — Norwegische Commission der Europaischen Grad- messung. Geodatische Arbeiten. Heft 6-7. 4to. Christiania 1889, 1890. The Commission. 186 Observations and Reports (continued). Paris: — Service Hydrographique do la Marine. Annales Hydro- graphiquos. Ser. 2. Annee 1890. 8vo. Paris. The Sei Service Hydrometriqne da Bassin de la Seine. K.'.-uiur des Observations Centralists pendant 1'Annee 1889. 8vo. Ver- sailles 1890 ; Observations sur les Coni-s d'Eau et la Plnie Centralisees pendant 1'Annee 1889. Folio. Versailles. The Service. West Point, N.Y.— U.S. Military Academy. Official Register. 1890. 8vo. [West Point.] The Academy. 1891.] Presents. 135 Observations and Reports (continued). Buda-Pesth : — Kb'tiigl. Ungar. Central-Anstalt fiir Meteorologie und Erdmagnetismus. Jahrbiicher. Bd, XVII. 1887. 4to. Budapest 1889. The Institute. India:— Tide Tables for the Indian Ports for 1891. Parts 1-2. 12 mo. London. The India Office. Kiel :— Konigl. Sternwarte. Publication. V. 4to. Kiel 1890. The Observatory. London : — Meteorological Office. Daily Weather Reports (Bound copy) July to December, 1889. 4to. London; Weekly Weather Reports. Vol. VII. Nos. 27-53, with Quarterly Summary. 4to. London ; Summary of the Observations made at- the Stations included in the Daily and Weekly Weather Reports. April to August, 1890. 4to. London; Quarterly Weather Report. Part 2. April-June, 1880. 4to. London 1890; Meteorological Observations made at Sanchez (Samana Bay), St. Domingo, 1886-88. 4to. London 1890; Meteorological Observations at Stations of the Second Order for 1886. 4to. London 1890. The Office. Nautical Almanac Office. The Nautical Almanac for 1894. 8vo. London [1890]. The Office. Navy Medical Department. Statistical Report of the Health of the Navy. 1889. 8vo. London 1890. The Department. Melbourne : — Mining Department. Annual Report. 1889. Folio. Melbourne; Report and Statistics for the Quarters ended 31st March and 30th June, 1890. Folio. Melbourne. The Department. Observatory. Monthly Record. January to June, 1890. 8vo. Melbourne. The Observatory. New South Wales : — Geological Survey. Memoirs. Palaeontology. No. 8. 4to. Sydney 1890 ; Records. Vol.11. Parti. 8vo. Sydney 1890. The Department of Mines, Sydney. New Zealand : — Colonial Museum and Geological Survey. Reports of Geological Explorations during 1888-89. 8vo. New Zealand 1890 ; Studies in Biology tor New Zealand Students. 8vo. Wellington [1889] ; Twenty-fourth Annual Report on the Colonial Museum and Laboratory. 8vo. New Zealand 1890; Catalogue of the Colonial Museum Library. 8vo. New Zealand 1890. The Director. Nice: — Observatoire. Annales. Tome II. 4to. Paris 1887. The Observatory. Norway : — Norwegische Commission der Europaischen Grad- messung. Geodatische Arbeiten. Heft 6-7. 4to. Christiania 1889, 1890. The Commission. VOL- XLIX. L On the Chief Line in the Spectrum of tl« \>'»dr by a special membrana hyaloidea, as was formerly supposed." Then, "At the ora serrata the several concentric layers of the cortex (of the vitreous) are so crowded together that the surface of the nucleos is separated from the limitans only by a very thin but plainly fibr< us layer. The fibres of this layer run parallel to the surface of the \ iiieous in wavy bundles, and are .not unlike bundles of connective tigsae=. The entire layer, thus changed, finally turns and passes towards the axis of the eye, thus completely covering the anterior snrface of the vitreous. Since we here, in fact, have not a single but several layers crowded together, and only loosely united with one another, it is easy to see how one might suppose that behind the lens there lay a special membrane covering tlie corpus vitreum, especially since the most superficial of these layers is perfectly smooth." Finally, " The tissue of the vitreous is here condensed to form a limiting layer, in the same manner as Bowman's membrane is formed by a condensa- tion of the snbstantia propria of the cornea ; an independent membiane — the hyaloidea — does not exist at this place." What occurs to me then, considering the eminence of the authori- ties on each side of the question, is that the methods of demonstration have not been sufficiently conclusive. After seeing it as I have seen it, nnd shown it to others, I cannot for one moment doubt its existence, for the proof of its existence could not possibly be more conclusive — if c;m even be dissected off and examined in any perfectly fresh unaltered ox eye. As Aeby has already:, I find, published, the eyeball is best left to decompose for some twenty-four "hours or longer, according to the external temperature, and then, on opening the sclerotic and choroid tissues carefully with fine blunt-pointed scissors, the vitreous and lens, nnited by the suspensory ligament, drop out in a mass, or at least nre very easily expressed. The suspensory ligament is now snipped all round, and the lens in its capsule removed. When this has been done, according to the one side, the bed of the 1891.] On the Fossa Patellaris of the Corpus Wtreutn. 1.39 lens — the fossa patellaris — and the posterior wall of the canal of Petit (now opened up) would be bounded or lined immediately by the substance of the corpus vitreum. According to the other side — with which I entirely agree — there stretches from side to side a distinct membrane, so that iu no part of its extent does the substance of the corpus vitreum reach the surface. Let me now proceed to the proofs, which are of various kinds — chemical, optical, and mechanical. Chemical Pigments.— Aniline dyes and picrocarmine stain the capsule of the lens, the hyaloid, and other such elastic membrane?. When the fresh corpus vitreum is so stained — and I prefer strong picrocarmine for some three minutes,, then washing in copious water — the hyaloid is perfectly well seen floating in water, with its wrinkles on distortion and its well-defined free edge at a puncture. Exactly the same appearance is seen on the front of the corpus vitreum — here there is something that stains deeply and that wrinkles. Moreover picrocarmine stains the hyaloid membrane and the vitreous substance differently : the former is red and the latter is yellow. The same difference is seen at the edge of a puncture in the floor of the patellar fossa: the red membrane is quite distinct from the yellow vitreous substance. Optical. — If, by means of a lens, the sun's rays be concentrated upon the hyaloid membrane, it is seen to have a fluorescent appear- ance, somewhat as if the surface had been bathed in a solution of quinine sulphate. That this fluorescent appearance is due to the lyaloid is obvious when the concentrated rays are made to fall on a puncture in the hyaloid membrane. The vitreous substance itself has no such appearance, but is clear and glassy, .so that the puncture is beautifully seen, and the edge of the hole is sharp and well defined. Exactly the same appearances are obtained when we examine the front of the vitreous ; the fluorescence is here too, and the difference between this appearance and that of the vitreous substance showing through the puncture is very marked. Mechanical. — When a blunt-pointed instrument is gently pressed upon the hyaloid membrane and then removed, the substance recoils simply, perhaps leaving a dimple for a little time; but, on- pressing more firmly, there comes an instant when the instrument suddenly sinks ; one has the impression that a membrane has been punctured, and that behind the membrane the substance is soft and inelastic.. This impression is at once supported on squeezing the mass of the vitreous between the fingers ; a little elevation of the vitreous substance is projected like a pimple through the opening in the membrane, and recedes when the pressure is withdrawn. When this is repeated in the front of the vitreous, the results are identical. So far, I have not mentioned anything which might not be equally well explained by supposing the existence of a dense superficial layer 140 On the Fossa Patellarin of tl,, \'iin'mn. [F<-!.. ."•. of the vitreous substance, but the membrane is no such thing; it is a true membrane; it can readily be isolated, stained, submitted to microscopical examination, Ac. Even with the unstained vitreous, it is quite easy to introduce a blunt instrument through a puncture in the membrane and, by working the instrument about under the surface, to detach the membrane from the surface of the vitreous substance. When this has been done, a bell of air blown under it displays the membrane to good advantage as a delicate, elastic, smooth, apparently structureless, perfectly transparent sheet of tissue, answering most completely to the terra " hyaloid." Though delicate, it is yet strong enough to support the whole weight of the vitreous when a blunt in- strument is put into it. When, the bounding membrane remaining intact, the vitreous is squeezed so as to bulge its anterior face, that face does not bulge equally all over its extent. The centre of the anterior face projects more than the peripheral ring. The central projected part corre- sponds to the fossa patellaris, where, as I shall show, the patellar mem- brane is thin, while the peripheral ring forms the back wall of the canal of Petit, and here the membrane is comparatively thick. The transition from the peripheral to the central parts is fairly sudden, for the central elevation rises from a distinct line corresponding to the inner margin of the peripheral ring. The canal of Petit is, therefore, a true canal. If the vitreous be inverted over the mouth of a test-tube (with a hole in the bottom of it) of about •£ inch diameter, and tied over it with a thick silk thread, and afterwards with a rubber band, the superficial part of the hyaloid and greater mass of the vitreous is cut through. If now the vitreous substance be carefully pulled off by forceps, or if the test-tube be set upright in a beaker, and water poured into the beaker, the water rising in the tube will bulge the membrane so that the vitreous substance will drain off it in an hour or so. The membrane thus isolated is toughened by exposure over night, so that such a membrane, though it looks like a mere film, yet sustained no less a pressure than 40 inches of water ; others sustained 22, 28, 34 inches, and so on, even after having been dead for days. If the membrane be snipped all round its periphery, it can be detached as a whole from the subjacent vitreous substance. When it has been removed, little tags of deeply-staining material are sometimes seen projecting from its deep face ; these, I have thought might be vestiges of the hyaloid artery ; but, whether these are there or not, there is little or no adhesion between the membrane and the vitreous substance. When removed, and its deep surface brushed under water remove any adherent vitreous substance, it is seen to be a hyaloic 1891.] Suspensory Ligament of the Crystalline Lens, fyc. 141 membrane with a thin centre and thick periphery. Under the micro- scope it is structureless. On removal it, of course, stains deeply, and thus can be readily examined. When one attempts to raise it outwards towards the hyaloid mem- brane and suspensory ligament, one may succeed as far as the origin of the suspensory ligament, but behind this point it is so firmly adherent to the vitreous substance that it cannot be raised. The notion of a membrane in front of the vitreous is supported by the behaviour of the vitreous body with its investing membranes intact in water ; it will remain many days with its form quite un- changed, and during all this time it may be handled without injur- ing it. But if the membranes be cut so as to expose the vitreous substance to the action of the water, this substance protrudes and has a cloud-like outline very different from the sharp, definite outline or surface at the uninjured anterior face of the vitreous body where still covered by membrane. Now there is never any of this cloud-like indefinite outline or surface at the uninjured anterior face of the vitreous body. I infer, therefore, that it is not vitreous substance that here comes into contact with the water, but that it is a mem- brane that is not notably acted on by water. After all these facts and considerations, I cannot doubt that there is in the perfectly fresh unaltered eye a membranous structure behind the posterior layer of the lens capsule, and that this structure has all the properties of a distinct membrane resembling the hyaloid, but differing in many respects from vitreous substance. I need say nothing here as to the immense importance in many questions of ophthalmological practice of a definite knowledge of the existence or non-existence of a membrane limiting the vitreous body anteriorly. [Note added January 15, 1891. — Since the above was sent in, I have had an opportunity of examining a series of sections of the entire human eyeball, made by Dr. Sheridan Delepine, and in all of these sections the membrane is distinctly seen in situ.] IV. "On the Connexion between the Suspensory Ligament of the Crystalline Lens and the Lens Capsule." By T. P. ANDERSON STUART, M.D., Professor of Physiology in the University of Sydney, N.S.W. Communicated by Professor SCHAFER, F.R.S. Received January 12, 1891. I have not been able to get a too precise statement as to the nature of this connexion, but Quain (9th ed.) says the suspensory ligament is "firmly attached" to the capsule; in another place Quain says it 'joins " it. Speaking of " suspensory fibres of the lens," Quain says 1 1'2 Suspensory /./'./•////<•/<£ of the Crystalline Lens, $c. [Fel>. .">. that some of these " pass into continuity with the posterior capsule.'' Tims "attachment," "joining," and "passing into continuity the expressions used to indicate the connexion. It is true that t la- last is employed with regard to the suspensory fibres, but since t i as described, are, like the suspensory ligament, derived from the hyaloid membrane and pass like it to the lens capsule, I think we may assume that the author in " Quain " regards them — fibres and ligament — as of like nature and mode of union with the lens capsule. Sehwalbe (' Anatomie der Sinnesorgane ') says the capsule is firmly united (venoachsen) with the zonula. Later, he speaks of the outer or zonular layer of the lens capsule being joined (i» Verbindung) to the zonula ; then again of its firm connexion (fester Zusammenhang) with the zonula when he uses this intimate union as an argument in favour of the zonular layer of the capsule being of connective tissue origin. In describing the zonula he says that its parts fuse (ve>~- ar^meZzfln) with the capsule without any perceptible line of demarcation, and probably form the above-mentioned zonular layer. Finally, the mode of fusion is as follows : The coarser bundles break up into a network of finer fibrils, which spread out on the surface of the capsule and, becoming pointed, lose themselves (sick verlieren) in the sub- stance of the capsule. From the various statements, I think it is clear that the general notion is that there is a direct continuity of substance between the suspensory ligament and the capsule. Now the observation which I ain about to describe seems rather to indicate that the suspensory ligament is only cemented to the capsule. , Upon opening some ox eyes that were in' an advanced state of decomposition, I found that the lens was quite free in the interior of the eyeball ; and, on examining it, I found that it was still enclosed in its capsule. This freeing of the lens I find to be the rule in such cases. On opening the capsule, the lens substance escaped, and on washing and staining the capsule with piorocarmine and other dyes, and on examining it in various ways, I have failed to find any roughnet-a ot surface, difference of thickness, or, in short, any indication of a rup- ture of tissue. The zonula seems to come away intact : is not broken or torn away. In fact, the decomposition seems to weaken the cohesion of eome cement substance by which the zonula adheres to the surface of the lens capsule. This observation seems to weaken the argument for an outer layer of the capsule being of connective tissue origin, and it may throw some light on cases of solution and atrophy of the suspensory liga- ment, on cases of detachment of the ligament from its insertions, and on cases of luxation of the lens. In any case it has a very direct bearing on the still unsettled question of the development of the lens capsule. 1891.] On the Form of the 'thorax. 143 V. " A simple Mode of Demonstrating how the Form of the Thorax is partly determined by Gravitation." By T. P. ANDERSON STUART, M.D., Professor of Physiology in the University of Sydney, N.S.W. Communicated by Professor SCHAFER, F.R.S. Received January 12, 1891. It is a well-known fact that the quadrupeds have the transverse gectiou of the thorax elliptical with the long axis vertical. This form of thorax, more or less, is possessed also by the human foetus. As the erect posture is gradually assumed in the development of species and of the human individual the ventro-dorsal and transverse diameters approximate to each other, and then, the process continuing, in the adult the transverse diameter exceeds the aiitero-posterior. That these aro the forms proper to the thorax when under the influence of gravitation alone is seen by holding a hoop made of a strip of ordinary crinoline steel ^ inch wide and about 6 feet long, so that its plane is vertical ; its form is that of an ellipse. Now grasp the hoop firmly between the fore-finger and thumb of one hand, and gradually turn the internal face of the portion grasped till it looks straight forwards. The front part of the hoop will, of course, be lower, corresponding in some measure to the slope of the ribs, &c. At the same time the diameters approximate to each other. Con- tinue the tuining till the face that looked straight forwards looks upwards and forwards, so that in fact the plane of the grasped portion corresponds to that in which the lower dorsal region of the vertebral column of man lies. The slope of the ribs is lessened, but the interesting points are that the transverse diameter exceeds the antero-posterior, and the exact curve and direction of the surface of the lower ribs are reproduced. Then are seen the twist in the long axis of the rib and likewise that great hollow on each side of the \ertebral column which is so marked a feature in the human thorax. I do not overlook the fact that the conditions in the organism aie not just the same as they are in this simple hoop ; but I think it will be conceded that where there is a force so constant and so potent in its action as is that of gravitation it will be yielded to by the organism unless there be some good reason to the contrary. Now there does not seem to me to be any such reason here, and it is interesting to observe how closely the thorax of the animal follows the lines of the hoop of steel when the conditions as to gravitation are the same. I am thus led to suspect that gravitation has had a larger share than is usually thought in moulding the form of the vertebrate thorax both in health and disease. 144 Dr. Johnson. On Asphyxia and [Feb. Any strip of elastic material will do for the above if the length be suitable — one readily finds the proper length by trying larger and smaller circles. VI. "On the Physiology of Asphyxia, and on the Anaesthetic Action of Pure Nitrogen." By GEORGE JOHNSON, M.D., F.R.S. Received January 26, 1891. (Abstract.) The main object of this paper is to bring forward additional evidence in support of the theory that the immediate cause of death in cases of asphyxia is the arrest of the pulmonary circulation. I have express my obligation to my friend Mr. Charles James Martin, MJ B.Sc., Demonstrator of Physiology in King's College, for the time labour which, by my request, he has bestowed in the performance of numerous and various experiments, the results of which will, I thinl throw much light upon the complex phenomena of asphyxia. It right to mention that Mr. Martin is not responsible for my interpr tion of the results of his experiments. All the experiments were performed on animals under the inflnc of anaesthetics, and every animal was finally killed by deprivation air. Animals— rabbits, cats, and, in a few cases, dogs — were asphyxiated either by ligature of the trachea, by the paralysing influence of cnrara, or by causing them to inhale a gas containing no free oxygen, viz., nitrons oxide, pure nitrogen, hydrogen, and carbonic acid gas. In all these experiments, re-inspiration of the gases was avoided by allowing the expired gas to escape through a "J"'^11^6 fixed iQ the trachea. During the performance of the experiments, in most cases, tl chest and pericardium of the animals were opened so that the relative fulness of the cavities might be readily observed. In all the experi- ments, the results, as regards distension of the heart's cavities, were essentially the same, no matter whether the air was simply exclude or whether an azotic gas (i.e., a gas, not in itself poisonous, but unable to support life) was substituted for atmospheric air ; the onlj difference being that when an azotic gas is inhaled the phenomei are far more rapidly produced, in consequence of the more speedj displacement of oxygen from the lungs. The principal changes in the heart's cavities were, first, distensior of the left cavities ; second, enormous distension of the right cavities with diminished distension of the left, the circulation being apparently arrested by the inability of the right cavities to empty themselves, in 1 89 1 .] A nccxtlictic . 1 ction of Pure Nitrogen. 145 consequence of obstruction in front. That the arrest of the circula- tion is not due to paratysis of the heart's walls, by the circulation of venous blood through its tissues, seems to be proved by the follow- ing1 experiment. Into the trachea of a small dog, with the chest and pericardium opened and kept alive by artificial respiration, a glass ~f"-tube was introduced, through which pure nitrous oxide was passed into the lungs, whilst the expired gases escaped into the air. As usual, first the left then the right cavities became distended, and in one minute the heart's action had nearly ceased, with over-distension of the right side. Then inhalation of nitrous oxide, impregnated with the vapour of nitrite of amyl, was substituted for pure N2O, by means of a two-way stopcock, and the result was that almost immediately the distension of the right cavities began to subside, and in two minutes they had nearly re- gained their normal size. The explanation is, that the circulation, having been arrested by the contraction of the arterioles, was, for a time, restored by the paralysing influence of nitrite of amyl upon those vessels, while atmospheric air was strictly excluded. Additional evidence of the influence of the arterioles in arresting the circulation during the progress of asphyxia is derived from the fact that a sufficient dose of such agents as are known to paralyse the arterioles, e.g., curara and atropine, prevents over-distension of the heart's cavities, and considerably prolongs the life of the animal. This is conclusively shown by experiments performed by Mr. Martin, the details of which are given in the paper of which this is an abstract. It has been suggested that the distension first of the left then of the right side of the heart in asphyxia is the result solely of systemic arterial contraction, the impediment acting backwards from the left side of the heart, through the lungs, to the right cavities and the systemic veins. The main objection to this theory is the fact that, when the chest is opened immediately after death from asphyxia, the lungs are found extremely pale, from anaemia of their minute vessels, and in a corresponding degree collapsed. Backward pressure from the left side of the heart, sufficient to greatly distend the right cavities, must of necessity involve engorgement of the pulmonary capillaries. That there is a certain amount of backward pressure from the primary distension of the left heart, extending as far as the pulmonary veins, would seem to be proved by observations made by Mr. Martin to the effect that a manometer in a branch of a pulmonary vein indicates an early and continuous increase of pressure during the progress of asphyxia ; but that this backward pressure does not extend to the right side of the heart is shown by the fact that in the Dr. Johnson. On Asphyxia and the 5, last stage of asphyxia, while the right cavities are in a state of extreme distension, the left are, as a rule, flaccid and comparatively empty, the lungs themselves, us before mentioned, being extremely anamiic and collapsed. The condition of the heart's cavities in t In- successive btagcs of asphyxia was clearly shown by an experimei which Dr. Rutherford performed in my presence in 1873. Tl details of this experiment are given in my paper (see diagram with tracing). The true explanation of these facts appears to be that, daring the latter stages of asphyxia, the pulmonary arterioles contract, and cause the extreme distension of the right cavities with anaemia of the pulmonary capillaries, and a corresponding defective supply to the left cavities of the heart. The continued increase of pressure in the pulmonary vein, obsc-r . <••! by Air. Martin, may perhaps be accounted for by the fact that in tho last stage of asphyxia the suction power of the left auricle is im- paired, partly by anaemia of the cardiac tissue, consequent on the contraction of the arterioles — both pulmonary and systemic, tl coronary included — and partly by the fact that the small amount blood with which it is supplied is more or less completely dt oxidised. [I venture further to suggest the following explanation of tt increased blood pressure which has been observed to occur in the pulmonary veins during the successive stages of asphyxia. During the first stage, when the left cavities of the heart are over-distended, as seen in Dr. Rutherford's experiment, there would be a backward pressure extending through the pulmonary veins and capillaries, even, perhaps, to the branches of the pulmonary artery ; but this backward pressure from the left side of the heart must obviously cease when, in the last stage of asphyxia, those cavities are nearly empty of blood. When, however, portions of the ribs are removed in order to introduce a manometer into one of the pulmonary veins, new and artificial cause of obstruction to the pulmonary veiioi circulation is introduced. The collapse of the lung, which results from the breach in the che wall, compresses the thin-walled pulmonary veins more than corresponding arteries, and so increases the intra-venous pulmonf pressure. It is an acknowledged fact that the comparatively slight compression of the pulmonary veins which occurs towards the end of a normal expiration lessens the flow of blood into the left side of tl heart.* It is obvious, however, that the pulmonary venous obstruc- tion thus caused must be very much less than that occasioned by the extreme collapse of the lung which results from an opening in the wall of the chest.— March 3, 1891.] * See Dr. M. Foster's ' Phjsiology,' 5th edition, p. 61S. 1891.] Ana'iithetic Action of Pure Nitrogen. 147 Drs. Bradford and Dean have proved not only the existence of pulmonary vaso-motor nerves, but also that they leave the cord higher up than the systemic vaso-motor nerves (vide ' Roy. Soc. Proc.,' vol. 45). These authors remark that " it is probable that the pulmonary vaso-motor mechanism is but poorly developed, compared with that regulating the systemic arteries." It would indeed be an incredible physiological anomaly if the vessels of an organ, through which the entire blood of the body has constantly to pass, had not the same regulating and resisting power, compared with the force of the right ventricle, as that possessed by the systemic arterioles. Mr. Martin has found by introducing a manometer into a branch of the pulmonary artery of a moderate sized cat, while the remaining branches were suddenly obliterated, that the blood pressure was rather more than doubled, rising from 17 mm. to 36 mm. of mercury. Mr. Martin also found that, during the last stages of asphyxia, the pressure in the pnlmonary artery is nearly doubled, while that in the carotid is rapidly falling. No experiment that has hitherto been devised can accurately measure the resisting power of the pulmonary arterioles or the actual force of the right ventricle, for the reassn that the arrest or great diminution of the pulmonary circulation weakens the muscular walls of the heart by cutting off the Wood supply through the coronary arteries.* The increase of systemic arterial blood pressure, which instantane- ously follows re-admission of air into the lungs, after the circulation had been almost completely arrested by exclusion of air, seems to prove that the heart's walls are not paralysed by venous blood. On the other hand, such a speedy restoration of the circulation is at once explained by the sudden removal of the obstruction which had been caused by the contracted pulmonary arterioles. * [Since this paper was communicated to the Royal Society, Dr. M. Foster has done me the favour to refer me to a paper by Professor Knoll (" Der Blutdruck in der Arteria pulmonalis," 'Sitzber. Akad. Wiss. zu Wien,' vol. 97, Abth. 3, p. 207). Dr. Knoll endeavours to measure the normal blood pressure in the pulmonary artery of the rabbit by dividing the sternum, opening the pericardium, and intro- ducing a tube into the pulmonary artery without wounding the pleura. Thus, the blood pressure is observed while normal respiration is carried on. Dr. Knoll, however, admits that the atmospheric pressure, consequent on the opening of the mediastinum, cannot be without some influence upon the circulation, •o that even this careful and difficult mode of procedure is not free from sources of error.— March 3, 1891.] 148 Dr. Johnson. On A*j>/ti/.i-<'t •//<. 461. 1891.] On certain Ternary Alloys. Zinc dissolved by Bismuth. 157 550—650°. 650—750°. 750—850°. 14-03 14-42 15-27 14-05 14-62 16-59 16-19 16-26 " " " Average 14-04 14-52 15-83 Bismuth dissolved by Zinc. Percentage of bismuth in alloy. . . Average 2-20 2-24 2-24 2-60 2-44 2-60 2-22 2-42 2-52 From these figures it results that the following percentages of zinc and bismuth respectively are dissolved for the mean tempera- tures 650°, 750°, and 800°. Zinc dissolved by Bismuth. Range 550 — 650° 14-04 Eange 650 — 750° 14-52 650 750° 14-52 750- 850° 15-83 Eange 750—850° Approximate "| mean temp. I Average . . 14-28 Mean temp, of "I 750°.. 15-18 Mean "1 temp. [• 15-83 of 650J \ of 800° J Bismuth dissolved by Zinc. Range 550 — 650° 2-22 Range 650 — 750° 2-42 650 — 750° 2'42 750 850° 2 '52 Range 750— 850°j Approximate! mean temp, y Average . . 2-32 Mean temp, ofl 750°....T... / 2-47 Mean ~| temp. [• 2 -52 of 650° J of 800° J Hence, while the solubility of bismuth in zinc increases between 550° and 800° to an extent only just measurable and barely outside le limits of experimental error, that of zinc in bismuth increases i.ys Dr. Alder Wright and Mr. C. Thompson. [Fob. IL>, in a much more marked fashion. The formula Zn413i7 requires Zn = 15*1, and Bi = 84'9 per cent. Mixtures of Bismuth, Zinc, and Tin. Two scries of experiments were made, one at a temperature rang, ing between 600° and 700°, and averaging near to 650s ; the other ranging between 700° and 800°, and averaging near to 750°. The results indicate that in presence of tin the solubility of zinc in bismuth and that of bismuth in zinc are both materially increased by incre- ment of temperature. A few experiments at a somewhat higher temperature, averaging near 800°, were also made, the results of which indicated a notable further increment in solubility ; but, as considerable difficulty was experienced in getting even moderately concordant figures at this higher temperature, these observations were not carried far enough to enable average curves to be deduced. In every case the mixture of metals employed contained equal quantities of bismuth and zinc with varying proportions of tin ; as in the case of the lead-zinc-tin alloys previously described, the effect of volatilisation and oxidation caused a small decrement in the proportion of zinc present in the compound ingots ultimately obtained relatively to the other two metals contained therein, especially in the experiments at the higher temperatures. In analysing the alloys prepared, we found that the method of analysis used for lead-zinc-tin alloys could not be adopted without modification, because the stannic oxide formed by the action of nitric, acid on the alloys retained variable amounts of bismuth in such a condi- tion as not to be removed by copious washing with dilute nitric acid, or even by boiling therewith.* In some instances we weighed the crude stannic oxide retaining bismuth, and then fused it with sodium carbon- ate and sulphur, whereby sodium sulphostannate was formed, soluble in water, and bismuth sulphide insoluble therein. By precipitating the stannic sulphide by means of hydrochloric acid from the aqueous solu- tion, and cautiously roasting it, the corrected weight of stannic oxide was obtained ; this we found always concorded sensibly with the weight deduced by converting the undissolved bismuth sulphide into oxic (by dissolving in nitric acid, precipitating boiling with ammonium carbonate, and igniting the precipitate), and subtracting the weight of this from that of the crude stannic oxide. In other cases, we dissolved the alloy in hydrochloric acid containing a little nitric acid, diluted and treated with sulphuretted hydrogen, separating the tin * It is noteworthy that no trace of lead appears to be thus retained by stannic oxide when alloys containing tin and lead are treated with nitric acid ; on the other hand, when alloys containing antimony and lead are similarly treated, the undis- Bolved antimony oxide retains a notable amount of lead, just as stannic oxide retains bismuth. 1891.] On certain Ternary Alloys. 159 and bismuth thus precipitated with ammonium sulphide. Check experiments made by both methods yielded sensibly the same tin percentages. In order to determine the zinc after removal of bismuth and tin, we first precipitated it as sulphide, then dissolved in hydro- chloric acid, and precipitated as carbonate, finally igniting and weigh- ing as oxide ; this method of treatment being adopted to prevent lime, &c., derived from the vessels used being weighed with the zinc, as would have been the case had the precipitation as sulphide been omitted. Any traces of oxide of iron contained in the zinc oxide were subsequently estimated and subtracted. The following figures were derived from the examination of twenty- one compound ingots, the percentages being reckoned upon the sum of the weights of tin, bismuth, and zinc found as 100. With some of the lighter alloys, where zinc was the main constituent, only the tin and bismuth were determined, and the zinc taken by difference. Series I. Temperature 600—700°. Heavier alloy. Lighter alloy. Excess Percentage of tin of tin percentage in mixture in lighter before fusion. Tin. Bismuth. Zinc. Tin.v Bismuth. Zinc. alloy over that in heavier. 0 0 85-72 14-28 0 1-32 97-68 0 2-5 3-23 80-27 16-50 1-98 3-45 94-57 ! -1-25 5-0 6-35 75-82 17-83 3-97 4-21 91-82 -2-38' 8-3 10-38 70-52 19-10 6-35 5-53 88-12 -4-03 13-2 14-35 62-24 23-41 8-50 8-04 83-46 | -5-85 15-9 18-01 56-10 25-89 10-24 10-90 78-86 -7-77 18-7 20-50 47-02 32-48 Series II. Temperature 700—800°. Heavier alloy. Lighter alloy. Excess Percentage of tin of tin percentage in mixture in lighter before fusion. Tin. Bismuth. Zinc. Tin. Bismuth. Zinc. alloy over that in heavier. 0 0 84-82 15-18 0 2-47 97-53 0 5-3 6-29 76-20 17-51 4-24 5-24 90-52 -2-05 7-1 8-81 72-34 18-85 5-40 6-08 88-52 -3-41 8-8 10-35 67-71. 21-94 6-29 7-35 86-36 -4-06 12-3 14-72 59-99 25-29 9-60 9-65 80-75 -5-12 15-3 16-87 54-03 29-10 11-57 12-62 75-81 -5-30 L60 Dr. Alder Wright and Mr. C. Thompson. [Feb. On plotting these figures as curves it is noticeable that, whilst the distribution of the tin between the heavier and lighter alloys formed is only slightly different according as the temperature is 650° or 750°, in each case the curve is of an entirely different character from that deducible from the previous experiments with lead, zinc, and tin. Instead of rising above the base line to a maximum and then falling again, ultimately crossing the base line and passing below it, each curve lies completely below the base line. Curves Nos. 1 and 2, fig. 1, FIG. 1. Percentage of Tin in Heavier Alloy . respectively represent the above values at 650° and 750° ; whilst No. 3 represents the corresponding curve obtained (Part I) with equal pro- portions of lead and zinc in the original mixtures at near 650° ; in each case the abscissae are the percentages of tin in the heavier alloys, whilst the ordinates are the excesses of the tin percentages in the lighter alloys over the corresponding percentages in the heavier ones. On the other hand, on plotting the curves representing the solu- bility of zinc in bismuth-tin (percentages of tin in heavier alloys as abscissae, and those of zinc as ordinates), and of bismuth in zinc-tin (percentages of tin in lighter alloys as abscissae, and those of bismuth as ordinates), it is obvious that the solubility increases in each case 1891.] On certain Ternary Alloys. 101 with the temperature, and that the amount of bismuth dissolved by zinc, or vice versa, regularly increases as the amount of tin present increases, just as in the case of the corresponding alloys containing lead instead of bismuth. Figs. 2 and 3 represent the solubility curves, the FIG. 2. curves marked 1 and 2 respectively indicating the values obtained at 650° and 750° ; the dotted lines connect the actual points of observa- tion, whilst the continuous lines represent the smoothed mean curves thence deduced. The following solubility tables are derived from these mean curves. 162 Dr. Alder Wright and Mr. C. Thompson. [Feb. 12, Fro. 3. t^mimimmf^mm^mmm^mmm^mmm^mmm^m^m mmmmmvAmmm IB'JB !•••••••'/ :s:ss mean pjgsnssr Qfl 11 Solubility of Zinc in Bismuth-Tin. At near 650°. At near 750°. Percentage Percentage Difference Percentage Difference of of for of for tin. zinc. 1 per cent. zinc. 1 per cent. 0 14-28 _. 15-18 2 15-20 0-46 16-10 0-46 4 16-20 0-50 17-10 0-50 6 17-30 0-55 18-20 0-55 8 18-50 0-60 19-50 0-66 10 19-80 0-65 21-00 0-75 12 21-20 0-70 22-80 0-90 - 14 22-70 0-75 24-90 1-05 16 24-30 0-80 27-50 1-30 17 25-15 0-85 29-40 1-90 18 26-20 1-05 32-00 2-60 19 28-10 1-90 — — 1 20 31-00 2-90 — 1891.J On certain Ternary Alloys. Solubility of Bismuth in Zinc- Tin. 163 At near 650°. At near 750°. Percentage of Percentage Difference for Percentage of Difference for tin. bismuth. 1 per cent. bismuth. 1 per cent. 0 2-32 _ 2-47 _ 1 2-80 0-48 3-05 0-58 2 3-30 0-50 3-70 0-65 3 3-80 0-50 4-40 0-70 4 4-30 0-50 5-15 0-75 5 4-80 0-50 5-95 0-80 6 5-35 0-55 6-80 0-85 7 6-10 0-75 7-70 0-90 8 7-20 1-10 8-65 0-95 9 8-70 1-50 9-70 1-05 10 10-70 2-00 10-90 1-20 11 — 12-20 • 1-30 On comparing these mean curves with those described in Parts I and II, obtained with lead-zinc-tin alloys, it is evident that the solu- bility of zinc in bismuth is always greater than that in lead, whether tin be absent or present to a given extent in each case ; and that, in the latter case, the rate of increment in the solubility of zinc in bismuth the proportion of tin present increases is more rapid than the corresponding rate of increment in the solubility of zinc in lead, 'recisely similar remarks apply to the solubility of bismuth in zinc. Mixtures of Bismuth, Zinc, and Silver. It has already been mentioned in Part II that mixtures of bismuth, zinc, and silver show the same remarkable behaviour as analogous mixtures of lead, zinc, and silver, leading to the conclusion that two definite compounds of zinc and silver are formed under appropriate conditions, indicated respectively by the formulae AgZn5 and Ag4Zn5 ; of which the first is characterised by being capable of dissolving more lead (or bismuth) than can either pure zinc or the second compound, and of being more soluble in lead (or bismuth) than either of these ; also of being somewhat unstable, so that when a solution of lead (or bismuth) in AgZn5 is kept molten for a long time it breaks up forming zinc and Ag4Zn-, which being unable to dissolve all the lead originally present, causes the separation of lead from the liquid metal as a heavier alloy containing a little zinc and silver in solution. The second com- pound Ag4Zn5 is characterised by the peculiar red colour assumed by a recently cut or filed surface exposed to the air for awhile, and by 164 Dr. Alder Wright and Mr. C. Thompson. [Feb. the circumstance that it is less soluble in lead (or bismuth), relatively to the zinc present, than either pure zinc or a mixture of zinc and silver in any other proportion. Three series of experiments were made exactly corresponding with those previously described with lead-zinc-silver alloys in Part II; in each case the temperature was as near 750° as could be managed, ranging between 700° and 800°. The analysis of the alloys was made by dis- solving in nitric acid, diluting, precipitating silver by hydrochloric acid, and washing the precipitate by decantation with hot dilute hydro- chloric acid, in case any bismuth oxychloride might have separated. The filtrate was evaporated to a small bulk and treated with water, and the filtrate from the bismuth oxychloride formed treated with sulphur- etted hydrogen ; the bismuth in the sulphide and oxychloride thus obtained was determined by converting the joint precipitates into oxide by dissolving in nitric acid, precipitating boiling with ammonium carbonate, and igniting. The zinc was determined as in the former alloys, and courected for small quantities of iron derived from the crucibles, &c. Series I.— Time of fusion, 8 hours. Temperature 700—800°. Percentage Excess of of silver Heavier alloy. Lighter alloy. silver percentage in mixture in lighter before alloy over that in fusion. Silver. Bismuth. Zinc. Silver. Bismuth. Zinc. heavier. 0 0 84-82 15'18 0 2-47 97-53 0 2 0-04 85-05 14-91 3-83 4-17 92-00 3-79 4 0-20 84-39 15-41 10-44 5-71 83-85 10-24 6-25 0-96 79-09 19-65 14-38 7-16 78-46 13-42 8-75 2-29 74-09 23-62 17-19 10-60 72-21 14-90 12-5 3-32 76-48 20-20 22-36 13-39 64-25 19-04 14 3-49 77-95 18-56 26-42 11-04 62 54 22-93 15-5 4-56 74-92 20-52 30-30 6-40 63-30 25-74 18 4 95 76-10 18-95 34-18 5-63 60-19 29-23 21 6-08 79-28 15-64 37-06 5-34 57-60 31-98 25 6-84 77-24 15-92 38-80 5-93 55-27 31-96 31 8-98 77-99 13-03 46-31 8-67 45-02 37-33 33 12-71 76-19 11-10 47-94 10-05 42-01 35-23 36 14-39 75-24 10-37 48-50 10-50 41-00 34-11 38 22-96 62-72 14-32 51-34 14-34 34-32 28-88 39-5 23-10 61-30 15-60 51-78 15-41 32-81 28-68 40-5 29-27 53-08 17-65 — — — — 45 39-90 41-03 19-07 ~~ — — — The above figures were derived from a series of twenty-eight coi pound ingots, each prepared from equal weights of zinc and bismut with varying proportions of silver. They show almost exactly tl 1891.] On certain Ternary Alloys. 165 same peculiarities as the corresponding series obtained with lead, zinc, and silver described in Part II ; thus the silver-distribution curve is of sensibly the same character, the excess of silver in the lighter alloy over that in the heavier being at first extremely great, but later on lessening, until a maximum elevation of the curve above the base line is attained, after which the curve again descends. Curve No. 1, fig. 4, indicates this, No. 2 being the corresponding curve from the FIG. 4. lead-zinc-silver alloys (Part II), the abscissae in each being the per- centages of silver in the lighter alloys, and the ordinates the ex- cesses of silver percentage in the lighter alloys over those in the heavier ones. Similarly, the curve traced out by plotting the silver and bismuth percentages in the lighter alloys as abscissae and ordinates respectively (No. 1, fig. 5) exhibits the same feature of rapid rise to a maximum, subsequent fall to a minimum but little above the starting level, and later continuous rise. The position of the first maximum, moreover, is close to that indicating the relationship AgZn5, just as with the former alloys. Silver. Zinc. Ratio of zinc to silver. 22-36 64-25 1 to 0-348 Calculated for AgZn5 1 to 0'332 1«6 Dr. Alder Wright and Mr. C. Thompson. [Feb. 12, Fio. 5. Further, those alloys where the silver and zinc present were approxi- mately in the proportions denoted by Ag4Zn- showed the same marked reddish hne on exposure to the air for a short time, after filing bright, as was observed with the analogous lead-zinc-silver alloys ; thus the two alloys containing the following percentages showed it strongly — Silver. 47-94 51-34 Bismuth. 10-05 14-34 Zinc. 42-01 34-32 Ratio of zinc to silver. 1-14 1-49 Mean 1'315 Calculated for Ag4Zn5 1*33 as also did some others, the compositions of which lay betwt these limits, which correspond respectively with 84 per cent, of Ag4Znt with a little excess of zinc and some bismuth, and with 80 per cent, of Ag4Zn6 with excess of silver and some bismuth. On the other hand, alloys containing somewhat larger excesses of silver or zinc showed only a much paler tint, whilst little or no coloration was visible with alloys where the percentage of Ag4Zn5 fell below about 65 per cent. We prepared some binary alloys of silver and zinc consisting mainly of Ag4Zn6, with but small excess of either silver or zinc ; these showed the coloration strongly. 1891.J On certain Ternary Alloys. 167 Again, the curve obtained by plotting the silver and zinc percent- ages in the heavier alloys as abscissae and ordinates respectively exhibits (No. 1, fig. 6), first, a rapid rise in the quantity of zinc pre- sent, followed by a fall to such an extent that the zinc present, reckoned per unit of bismuth, diminishes down again to an amount considerably below that present in the binary bismuth-zinc [alloy con- taining no silver ; a minimum of zinc is finally attained, after which the zinc present relatively to the bismuth rises continuously. VOL. xux. N 168 Dr. Alder Wright and Mr. C. Thompson. [Feb. 12, Silver. Himmith. Zinc. Zinc per unit of l«i-mnt}i. 0 M4-82 15-18 0-179 2-29 74 -Of) 23*02 (maximum) 0-318 4-95 76-1" 18-95 0 - 6-84 77-21 0*1 S MS 77-99 13-03 O-lf.7 12-71 76-19 11-10 0-145 14-39 75-24 l()-:<7 (minimum) 0-138 22-96 63-72 O-i. 29-77 53-08 17 65 0 -332 39-90 41 -JM 168 This reduction of zinc to a minimum is far more strongly marked than in the case of the lead-zinc-silver alloys ; the point where it occurs is not far from that where the silver and zinc present are in the ratio indicated by the formula Ag4Zn5. Silver. Zinc. Ratio of zinc to silver. 14-39 10-37 1 to 1-39 Calculated for Ag4Zii- 1 to 1 '33 Whence it may be concluded that, whereas AgZn5 is much more soluble in fused bismuth than pure zinc (relatively to the zinc present in each case), the same is not the case with the compound Ag4Zn6, which dissolves in bismuth to a much less extent than would zinc alone in the absence of silver. Series II was prepared in precisely the same way as the correspond- ing series with the lead-silver-zinc alloys ; i.e., mixtures of the three metals were made and fused for eight hours as in Series I ; the com- pound ingots thus obtained were cut in two so as to separate from one another the lighter and heavier alloys thus formed, and the former parts separately fused at the same temperature (700 — 800°) for Series II. — Limiting Composition of Lighter Alloys. Silver. Hi.-miitli. Zinc. 3-93 2-95 93-12 1372 4-15 82-18 21-24 4-83 73-93 33-27 4 89 61-84 37-50 5-34 57-16 41-43 5-90 52-67 48-02 11-12 40-86 52 01 16-47 31-52 1891.] On certain Ternary Alloys. 169 another eight hours. In this way a farther separation was brought about in the case of the alloys prepared with smaller proportions of silver, but no material alteration in the case of those made with larger proportions, just as with the lead-silver-zinc alloys. On plotting the results, a curve was obtained (No. 2, fig. 5) from which the first maximum, at approximately the point representing the com- pound AgZn-, had completely disappeared, as had also the subsequent fall, the curve exhibiting a progressive rise from beginning to end. Series III was similarly made with the heavier alloys thus sepa- rated from the lighter ones ; the results, when plotted (curve No, 2, fig. 6), showed that the abnormally large percentages of zinc observed in the earlier part of the series had disappeared, whilst the diminution in amount of zinc dissolved relatively to the bismuth present down to a minimum and subsequent rise again was still well marked, the position of the minimum corresponding, as before, with a ratio of zinc to silver not far from that indicated by the formula Ag4Zn-. Series III. — Limiting Composition of Heavier Alloys. Silver. Bismuth. Zinc. Zinc per unit of bismuth. 0 84-82 15-18 0-179 5-42 80-62 13-96 0-173 7-65 80-70 11-65 0-144 11-71 78-00 10-29 0-132 13-14 17-98 77-85 71-00 9-01 11-02 0 '116 (minimum) 0-155 22-96 62-70 14-34 0-228 25-11 61-39 13-50 0-220 Position of minimum : — Silver. Zinc. Ratio of zinc to silver. 1H-14 9-01 1 to 1-45 Calculated for Ag4Zn5 1 to 1'33 „ AgZn 1 to 1-66 The following tables represent the mean solubility curves deduced all the preceding results, omitting the earlier alloys in Series I, rhere, owing to the presence of undecomposed AgZn6, excess of lead ras present in the lighter alloys, and excess of zinc in the heavier ics. N 2 170 Dr. Aider Wright and Mr. C. Thompson. [Feb. 12, Solubility of zinc in bismuth -silver. Solubility of bismuth in zinc-silver. Percentage of silver. Percentage of zinc. Difference for 1 per cent. Percentage of silver. Percentage of bismuth. Difference for 1 per cent. ! 0 15-18 _ 0 2-47 1 14-70 -0-48 5 2-82 0-07 2 14-20 -0-5 10 3-17 0-07 5 12 -70 -0-5 15 3-52 0-07 6 12-25 -0-45 20 3-87 0-07 11 10-00 -0-45 25 4-27 0-08 12 9-65 -0-35 30 4-67 0-08 IS 9-50 -0-15 35 5-07 0-08 14 9-50 0 36 5-15 0-08 15 9-65 -I-0-16 37 5-23 0-08 16 10-00 + 0-35 38 5-40 0-17 17 10-50 + 0-5 39 5-70 0-30 18 11-20 + 0-7 40 6-10 0-40 19 12-00 + 0-8 41 6-50 0-40 21 13-60 +0-8 42 7-00 0-50 22 14-30 + 0-7 43 7-50 0-50 23 14-95 + 0-65 44 8-00 0-60 2* 15-50 + 0-55 45 8-60 0-60 25 16-00 +0-5 46 9-20 0-60 2»! 16-40 +0-4 47 9-90 0-70 27 16-80 +0-4 48 10 -r>o 0-70 28 17-10 -(-0-3 49 11-40 0-80 n 17-70 +0-3 50 12-30 0-90 31 17-90 +0-2 51 13-70 1-40 32 18-10 +0-2 52 16-30 2-60 33 18-25 -I-0-15 3(3 18-70 -1-0-15 37 18-80 +0-1 40 19-10 40-1 On comparing together the relative effects on the solubility of; bismuth in zinc and of zinc in bismuth produced by the simultaneous presence of tin or of silver the same general result is deduced as in the case of lead-silver-zinc and lead-tin-zinc alloys, viz., that in each instance the solubility is considerably more increased by the presence of a given proportion of tin than by that of the same amount of silver. If 100 parts of zinc can take up m parts of bismuth in presence of x parts of tin (or silver), and if 100 parts of bismuth can take it, parts of zinc in presence of « parts of tin (or silver), then the lollowing tables give the correlated values of m, n, and a?, these values being minima in the case of alloys containing silver, i.e., being deduced i'l-oiu those experiments where the influence of the presence of the com- pound AgZn5 in increasing solubility was eliminated. 1891.] On certain Ternary Alloys. 17J Zinc dissolved by 100 parts Bismuth dissolved by of bismuth in presence of x parte 100 parts of zinc in presence of of tin (or silver) . x parts of tin (or silver). a.-. Tin Tin Silver Tin Tin Silver at 650°. at 750°. at 750°. at 650°. at 750°. at 750°. n. Diff. ». Diff. w. Diff. m. Diff. m. Diff. m. Diff. 0 16-8 — 17-9 — 17 '9 — 2-37 — 2-53 2-53 — 2'5 18-5 1-7 19 -6 1 -7 16-8 -1-1 3 -70 1 -33 4 -30 1 '77 2-75 0-22 5 20-3 1-8 21 -4 1 -8 15-8 -1-0 5-20 1-50 6 -20 1 -90 3 -00 0 -25 7-5 22-3 2-0 23-5 2-1 14-9 -0-9 7-00 1-80 8-40 2-20 3-25 0'25 10 24-4 2-1 26-0 2'5 14-0 -0-9 9 '50 2 '50 10-80 2-40 3-50 0'25 12-5 26-6 2-2 28-5 2-5 13-2 -0-8 13 '40 3 '90 13-70 2-90 3-75 0-25 15 28-9 2-3 31 -1 2 -6 12-6 -0-4 17-00 3-30 4-00 0-25 17-5 31-3 2-4 34-0 2-9 12-3 -0-3 4-25 0-25 20 33-7 2-4 37 '2 3 -2 12-8 +0-5 4-50 0-25 22-5 36 '3 2 -6 41 -2 4 -0 13-8 +1-0 4-75 0-25 25 39-1 2-8 46-2 5-0 15-3 +1-5 5-00 0'2r» 27-5 42 -0 2 '9 52-3 6-1 17-2 +1-9 5-25 0-25 30 45-0 3-0 19-3 +2-1 5 -50 0 -25 :55 52-1 7-1 22-8 +3-5 6-00 0-50 40 61-8 9-7 25-8 +3-0 6-50 0-50 50 30-7 + 4-9 7-60 1-10 60 34-7 +4-0 8 -90 1 -30 70 38 2 +3-5 10-50 1-60 80 41-4 +3-2 13 -00 2 -50 90 44-5 +3'1 16-10 3-10 100 47-5 +3-0 19-60 3-50 The curves indicated by the continuous lines in figs. 7 and 8 repre- snt these numbers, the dotted lines representing the analogous curves iescribed in Part II, obtained with lead-zinc-tin and lead- zinc- silver illoys. In fig. 7, curve No. 1 indicates the amounts of zinc dissolved it 650° by 100 parts of bismuth in presence of x parts of tin, whilst To. 2 represents the corresponding amounts dissolved at the same jmperature by lead. Nos. 3 and 4 similarly represent the amounts )f zinc dissolved at 750° by bismuth and at 800° by lead respectively, fos. 5 and 6 indicate the amounts of zinc dissolved in presence of parts of silver by 100 parts of bismuth at 750° and of lead at 800° respectively. In fig. 8, curves Nos. 1 and 2 respectively represent the amounts of bismuth and lead dissolved by 100 parts of zinc in presence of x parts of tin at 650°. Nos. 3 and 4 represent similarly the bismuth dis- solved at 750° and the lead at 800° respectively. Nos. 5 and 6 indicate the bismuth dissolved at 750° and the lead at 800° in pre- sence of x parts of silver. 172 Dr. Alder Wright and Mr. C. Thompson. [Feb. li'. Bp •&••••••« BH •• !•••• •••••••••• ill \m mm EHI MMHiHH ••••I ••••I mmm ••• mm 0 SlMHH •••••••• S^flM KWBNEVI of TZ. 1891.] On certain Ternary Alloys. 173 174 Dr. Wright .-mil M- >si>. Thompson and Leon. [Feb. III. "On Certain Ternary Alloys. Part IV. On a Method of Graphical Representation (suggested by Sir G. G. Stokes) of the way in which certain Fused Mixtures of Three Metals divide themselves into Two different Ternary Alh>\s: with further Experiments suggested thereby." My C. R. ALDER WRIGHT, D.Sc., F.R.S., Lecturer on Chemistry and Physics in St. Mary's Hospital Medical School ; C. THOMPSON. F.I.C., F.C.S. ; and J. T. LEON, B.Sc., F.C.S., Assistant Lecturer on Physics and Demon- strator of Chemistry in St. Mary's Hospital Medical School. Received January 29, 1891. A method of graphically representing the results of the experi- ments described in the previous portions of these researches been kindly suggested to one of us by Sir G. G. Stokes, founded on a principle which he regards as self-evident. We subjoin a note which he has been so good as to draw up for us, explaining the application of this method, and then describe some further experiments which we have instituted with a view to test the correctness of the assumed principle. Note on a Graphical Representation of the Results of Dr. Alder Wright's Experiments on Ternary Alloys. By Sir G. G. STOKES, Bart., F.R.S. Suppose three liquids such as water, ether, and alcohol, of which the third is miscible in all proportions with either of the others, are mixed together, the temperature being1 kept constant. According to circumstances, the mixture forms a single liquid mass, or separates into two. In the latter case, if we suppose that the liquids had been merely gently poured together, and imagine the upper and under portions separately to be homogeneous to start with, this state of things would not remain ; an alteration of composition would take place close to the surface of separation on both sides, depending on the relative solubilities, Ac., of the ingredients. If now the two altered strata were mixed up with the rest of the portions to which they respectively belong, the same thing would go on again, and so on till a condition was reached in which what we may call an equilibrium of composition on the two sides of the surface of separation had been attained. As this equilibrium depends only on the molecular forces, which are insensible at sensible distances, it is evident that the equilibrium would not be disturbed by removing a part of either the upper or the under liquid, or by adding to it liquid of exactly the 1891.] On certain Ternary Alloys. 175 ime composition as itself. This final state would take place only [try slowly in the manner conceived above ; but if the mixture be pell agitated the total surface of separation, where alone the change composition can go on, is greatly increased, and, moreover, the altered strata are mixed up with the rest of the liquids to which they respectively belong, so that the final state is reached comparatively quickly. I think I have seen an experimental verification of this anticipation, namely, that equilibrium depends only on the composi- tions of the upper and lower mixtures, and not on their quantities, in a French serial, but I have not the reference. The same principles would apply to ternary alloys, which form a homogeneous mass, or separate into two, as the case may be ; but of course the difficulty of preserving a constant temperature is much greater, as well as that of giving sufficient agitation to bring about the final condition. It seemed to me that, for giving an insight into the results of experiments with ternary alloys, a mode of graphical representation might be usefully employed which is already well known. It is the same as that which Maxwell used for the composition of colours, at least with one slight addition. In this way the whole of the circum- stances of the experiment, so far as they are material, would be exhibited to the eye. Let A, B, C be three liquids, such as water, ether, alcohol, or else lead, zinc, tin, in fusion, of which the third (which for distinction may be called the solvent) may be mixed in all proportions with either the first or the second. Take a triangle, ABC (fig. 1), which may be of FIG. 1. 176 Dr. Wright and Messrs. Thompson and Leon. [Feb. any form, but is most conveniently chosen eqnilateral ; and, to repre- sent the composition of any mixture of the three, imagine weight - equal to those of the substances A, B, C placed at the points A, B, C, and find their centre of gravity, P. To each different set of propor- tions A : B : C (the letters here denoting weights) will correspond a different position of P, which point will serve to represent to the ej the composition of an actual or ideal alloy (supposing the substances to be metals) formed of the three metals in the given proportions. If the quantity of the solvent be sufficient, P will represent on tht diagram the composition of an actual alloy. If it be insufficient, tl alloy represented as to composition by P will be ideal only ; and attempting to form it the mass will separate into two layers. If w( suppose the agitation to have been sufficient, there will be equilibriui of solution at the surface of junction, and the mass will have reacht its final state. Supposing this condition to have been attained, the two portions be analysed, and the points Q, R representing tl compositions be laid down on the diagram, and joined by a straight line. From the construction, this line must pass through the poii P if there has been no loss by volatilisation or oxidation. Let same thing be done for several other proportions of the ingredient Then the points Q, R will lie in a curve aQLR6, cutting AB in tv points a, b, which represent, the first, a saturated solution of B in the second, a saturated solution of A in B. Call this curve tl critical curve, and the lines such as QR tie-lines, or simply ties. Tl the critical curve and the system of ties will represent the compl result of the experiments, supposing them to have been exactly Alloys of a pair may conveniently be called conjugate. Intermedij tie-lines may be interpolated by eye ; or if we prefer we may sul tute for the system of ties their envelope, on which plan the resnl of the experiments would be completely represented by two curve the critical curve and the envelope. The critical curve separates mixtures of which alloys can actually be formed from those on attempting to form an alloy of which the mass separates into two layers. In the latter case, if through P draw a tangent to the envelope, cutting the critical curve in Q, the points Q, R will represent the compositions of the portions int which the mass separates, while their weights will be as PR to PQ. If L be the limiting position of the chord QR, or, in other words, the point of contact with the critical curve of a common tangent to it and the envelope, as P tends to coincide with L, the two strata into which the mass separates tend to become identical in nature. If we take a mixture of A and B, represented by a point c in aft, and con- tinually increase the quantity of C from 0, the point P will ascend from c towards C until it reaches the critical curve. At this stage the quantity of the second alloy has just dwindled away to nothing, 1891.] On certain Ternary Alloys. 177 its nature, so long as there was any of it left, differing from that of the other alloy. If, however, the point c lies in the line CL, on increasing the quantity of C the two alloys merge into one. On communicating to Dr. Alder Wright this mode of graphical representation, he tried it on a large scale on the results of two pairs of series from the former experiments. In one pair the temperature was 650°, and the proportion by weight of zinc to lead was 2 to 1 in the first case, and 1 to 2 in the second. In the other pair the weights of zinc and lead were equal, and the temperature 650° in one case and 800° in the other. In the first pair the agreement of the critical curves was very good, but the agreement in the direction of the ties was not by any means equally good. In the upper part of the figure, corresponding to the case in which there was a con- siderable quantity of tin, though not enough by any means to pre- vent the formation of two layers in the entire mass, the difference of inclination ranged to about 5", the ties in the first case being inclined to those in the second as if they had been turned round in the direc- tion of a line passing through the lead corner of the triangle, and turning round in the direction from lead- zinc to lead-tin. In the second pair of series in which the weights of lead and zinc were equal, and the temperature was 650° in the first case and 800° in the second, the critical curve for 800° was of the same general character as that for 650°, but lay a little inside it, which is just what was to be expected, on account of the increase of solubility attending the higher temperature. Moreover, the critical curve for 650° agreed very fairly with those for the same temperature in the first pair, notwith- standing the difference in the proportion of lead to zinc in the three cases. I had not anticipated the greater accordance existing between the critical curves in different cases for the same temperature than that shown in the direction of the ties. But, when the plottings revealed it, it seemed to me that the cause was not far to seek. When the molten mass has as yet been but slightly stirred, the superposed alloys, supposed to be severally homogeneous, will most likely be represented on the diagram by points, one or both of which lie out- side the critical curve. In this condition an alloy represented by an external point, having the metal C to spare, will be capable of dis- solving bodily a portion of the other. This process accordingly, being something analogous to the solution of a salt till saturation is obtained, will go on as the stirring proceeds, and be sensibly complete in a moderate time. The two alloys will then be represented by two points lying on the critical curve. Such alloys may be said to be associated. But the passage from merely associated to truly conjugate alloys, as the stirring proceeds, is likely to be decidedly slower. For now neither alloy can bodily dissolve any portion, however small, of 17* Dr. Wright and Messrs. Thompson and Leon. [Feb. the other ; there can only be an interchange of constituents across surface of separation. The critical curve may be otherwise defined as the curve expressing the saturation of the solvent C with a mixture in given variable pro- portion of the remaining substances A, B. That it is really such, little consideration suffices to show. The determination according of the critical curve furnishes us with definite information, even though we do not go into the ulterior question of the condition of conjugation. Perhaps the attainment of true conjugation might involve more stirring than wonld be practically feasible with molten metallic mix- tures. The most hopeful way would seem to be to fuse the mass at a higher temperature than that intended for the experi- ment, stirring it well, and then let down the temperature to that intended, stirring all the time, and avoiding too rapid a fall of temperature. If truly conjugate alloys were obtained, and portions of each we taken and fused together at the temperature at which the allc were made, the compositions ought to be the same as before. But the alloys were merely associated, then, even if the stirring in the second part of the experiment were sufficient to ensure conjugation, the compositions wcnld not be the same as the original, nor wonld they be independent of the proportion of the two alloys which the operator took for fusing together. The triangular method of representation described by Sir G. Stokes in the above note obviously possesses several advantages, ii much as it represents in one diagram simultaneously a number of results which the ordinary curves drawn with abscissae and ordinates can only partially indicate, consequently necessitating several different curves being drawn in order to represent graphically the entire set of results ; thus the two branches of the "critical curv*-,' obtained by directly plotting the figures yielded on analysis of the lowest and uppermost portions respectively of the compound ingot formed (in the case of a mixture separating into two different ternary alloys), represent the two solubility curves (e.g., of zinc in lead-tin and of lead in zinc-tin), whilst the " ties " or " tie-lines" indicate, according as they slope to one side or the other, the relative propor- tions of the " solvent " (e.g., tin) in the heavier and lighter alloys ; so that, when (as in the case of mixtures of lead, zinc, and tin) with certain proportions of "solvent " the heavier alloy, and with other pro- portions the lighter one, contains the larger percentage, this variation is at once indicated to the eye by the change in direction of slope of the tie-lines (compare fig. 3). Further, when once the critical curve for 1891.] On certain Ternary Alloy a. 179 given temperature has been laid down, it is at once evident by inspec- tion whether a given mixture of metals will furnish a "real " alloy (not separating into two different ternary mixtures), or only an " ideal" alloy (i.e., one not capable of existence, and consequently separating into two different ternary alloys) ; for, in the one case, the centre of gravity of the weights of the three metals respectively placed at the angles of the triangle will fall outside, and, in the other case, inside, the space enclosed between the critical curve and the base of the triangle. Again, any abnormal results due to the formation of definite chemical compounds (such as the silver-zinc compounds AgZn5 and Ag4Zn5, shown to exist by the experiments described in Parts II and III) are equally indicated by the irregularity of the outline of the critical curve deduced : thus fig. 2 indicates on Sir G. G. Stokes 's - Fie. 2. / 1 a d. Zin.r rstem some of the results obtained with zinc-lead-silver al]o}Ts Jart II, ' Roy. Soc. Proc.,' vol. 48, p. 33, Series I) ; the branch of bhe critical curve corresponding with the lighter alloys obviously idicates the first maximum of dissolved lead (at a point near to that jrresponding with AgZn), the subsequent fall, and the point where larked increment again becomes apparent (near that corresponding 180 Dr. Wright and Messrs. Thompson and Leon. [Feb. 12, with AgtZn5) in the same way as the abscissa and ordinate curve shown in fig. 5, Part II, p. 35. It is noteworthy, however, that « hi 1st the direction of the slope of the ties indicates that throughout the lighter alloy contains more silver than the heavier one, the triangular graphical representation does not clearly indicate that the difference in silver percentage between the lighter and heavier alloys rises to a maximum and then diminishes again, as is distinctly shown In i lie ordinary method with abscissae and ordi nates, as depicted in tig. 4, Part II, p. 35.* Precisely the same remarks apply if the analogous results obtained with bismuth-zinc-silver alloys described in Part III are similarly plotted. In addition, however, to the employment of this improved method of graphical representation, Sir G. G. Stokes deduces from a priori considerations an important general principle, viz., that when sufficient amount of intermixture of the constituent metals has taker place a state of equilibrium is arrived at (the temperature being Constant throughout), such that the presence of one ternary alloy in no way affects the composition of the other ; so that the addition or subtraction of a further quantity of either alloy, or of any mixture of the two, does not affect the compositions, but only the relative quantities present, of the two alloys; whence, if any given weights of the two fused alloys be intermixed, the same weights of the same alloys will separate again from one another by gravitation on standii If. therefore, two given alloys, A and B, be thus related (truly jugate), and in any particular experiment carried out until equilibrium is reached one of these alloys, A, be formed, the other alloy, B, must necessarily be also produced ; and this must be the case no matter what may have been the relative proportions subsisting between three metals in the mixture originally employed. It appeared to us of considerable interest to examine from the experimental point of view whether this general principle can be * [Sir G. G. Stokes has pointed out to me that the diagram, fig. 1, shows at one* that, inasmuch as the difference between the percentages of the solvent in two con- jugate alloys vanishes for the pair, a, b, being nil for each, and again for the pair which merge into one, represented by the point L, it must necessarily be a maximum for some intermediate pair ; and also that, in order to preserve the con- tinuity of conditions, we must, in crossing L, pass from the upper alloy to the lower, and rice versa. Hence, if the entire system of ties could be determined, so as to obtain every possible pair of conjugate points lying, one on one side, the other on the other side, of L, and if these values were plotted on the abscissa and ordinate system, the curve representing the difference between the percentages of the solvent, after having ascended and attained a maximum elevation, must descend again to the base line at a point corresponding with L. If we wish to con- tinue the curve beyond that point, we must now take the ordinates negative instead of positive, the same in magnitude as before, and the curve having crossed the base line, and attained a minimum elevation, will ultimately ascend again to the final l>oint on the base line.— C. R. A. W., February 25, 1891.] 1891.] On certain Ternary Alloys. 181 verified in practice, or whether interfering causes prevent anything more than demonstrations of approximate correctness being obtained ; the more so that some of the results previously obtained by two of us do not appear to be in harmony with Sir G. G. Stokes's proposition. In Part I (' Boy, Soc. Proc.,' vol. 45, p. 461) three series of experi- ments were described, made with lead, tin, and zinc, where the ratio of lead to zinc was 2 to 1, 1 to 1, and 1 to 2, in the three series spectively ; and the figures obtained led us to the conclusion that, rhilst an indefinite number of different mixtures may be prepared, one of which will give the same heavier alloy, the lighter alloy simultaneously formed will be different in each case; and conversely: " a deduction obviously incompatible with Sir G. Gr. Stokes's proposition. On the other hand, it is argued by Sir Gr. G. Stokes that these experi- ments do not necessarily prove anything more than the extreme difficulty experienced whilst making experiments with fused metals in obtaining such an intimate intermixture as to bring about the condition of perfect equilibrium between the two alloys formed in any given instance ; and that, in point of fact, the differences observed in the compositions of the various lighter alloys associated with a given heavier one, or vice versa, are not greater than might reasonably be expected were equilibrium not perfectly attained in some or all of the observations. Further, the fact that the differences are always in the same general direction tends to indicate that some constant interfering cause is at work ; thus, when curves were plotted (Part I, fig. 5, p. 476) with the tin percentages in the heavier alloys as abscissae, and the excesses of tin percentage in the lighter alloys over those in the heavier ones as ordinates, the curve deduced from the series of experiments where the ratio of lead to zinc in the original mixture of metals was 2 to 1 underlay that similarly obtained in the second series, where the ratio was 1 to 1, which again underlay that deduced from the third series, where the ratio was 1 to 2 ; whereas all three curves should have coincided were Sir G. G. Stokes's proposition correct, and all interfering causes completely eliminated. An analogous result is obtained when the analytical figures are plotted on Sir G. G. Stokes's triangular system. Fig. 3 represents the plottings thus obtained of the two series where the ratio of zinc- to lead was 2 to 1 and 1 to 2 respectively (Part I, 'Boy. Soc. Proc.,' vol. 45, Series IV, p. 474, and Series VI, p. 475) the temperature throughout being near to 650°. The ties in the first case are indi- cated by dotted lines, and in the second by continuous ones. Obviously the critical curves deduced from the two sets of observa- tions respectively do not differ very markedly ; but the angles of slope of the ties are not identical, so that a given heavier alloy is not conjoined with the same lighter one (nor vice versa) in the two cases ; whilst the direction of the variation is the same throughout. Dr. Wright and Messrs. Thompson and Leon. [Feb. FIG. 8. In order, if possible, to obtain experimental evidence of the truth or otherwise of the general proposition arrived at by Sir G. G. Stokes, as well as some explanation of the deviation therefrom of these previous results, we first of all carried out various further experi- ments with mixtures of lead, zinc, and tin, employing additional precautions to minimise errors due to imperfect intermixture, more especially by continuing for much longer periods of time the process of agitation of the fused metals by vigorous stirring; the results, however, did not differ materially from the previous ones, and indicated generally that the composition of the heavier alloj practically obtained associated with a given lighter one, or vice vend, was subject to fluctuation within certain not very wide limits, according to the proportion subsisting between lead and zinc in the original mixture employed; but whether this result was brought about by interfering causes, or was possibly due to the not absolute correctness of Sir G. G. Stokes 's principle, the experiments did not unable us to decide. In the hope of eliminating disturbing causes, we next endeavoured to carry out analogous observations at the ordinary temperature with liquids not metallic in their nature, bat resembling the metals tin, lead, and zinc from the point of view of 1891.] On certain Ternary Alloys. 133 their relative solubilities, i.e., two of the liquids being only miscible together to limited exteuts (like lead and zinc), whilst the third was miscible in all proportions with either of the others separately. The difficulty of making sufficiently accurate analyses of the ternary mixtures thus obtained prevented our using several such groups of liquids, which at first sight suggested themselves, more particularly mixtures of alcohol, -water, and ether ; but we found that chloroform, water, and glacial acetic acid fulfilled all the necessary conditions ; so that, when a mixture of equal weights of the first two with not too large a proportion of the third was well agitated and allowed to stand, it separated into two ternary solutions exactly correlative with the ternary alloys previously examined ; the heavier one consisting chiefly of chloroform with some of the acetic acid and an amount of water proportionate to the acetic acid present ; the other consisting mainly of water with the rest of the acetic acid, and more or less chloroform dissolved therein. Calling any given such pair of conjugate mixtures A and B respectively, we found that the general principle deduced by Sir 0. G. Stokes could be verified with sensible accuracy with these liquids • on agitating together A and B in various proportions, each liquid separated out again unchanged in each case, no matter whether A was used in large excess of B, or vice versa. On the other hand, when two different alloys, A and B, were made of lead, tin, and zinc in such proportions that one was approximately conjugate to the other as indicated by the previously recorded observations, we did not succeed in getting anything like such sharp results ; experiments where 2 parts of A to 1 of B were mixed together, and treated side by side with a mixture of 1 part of A to 2 of B, did. not give quite the same results in the two cases, the differences being considerably larger than anything attributable to ars of analysis and such like sources of inaccuracy. Mixtures of Chloroform, Water, and Acetic Acid. The analysis of such mixtures we found could be carried out with siderable accuracy and . ease in the following way ; a weighed irtion of the mixture (contained in a stoppered bottle) was diluted with water, and titrated with a fresh caustic soda solution accurately standardised, using phenolphthale'm as indicator. Another portion, eighed in a flask or bulb tube containing a. little water, was then ibmitted to -the action of a current of dry air sucked through it, e issuing gases and vapours being made to pass through a pumice- stone and sulphuric acid drying tube. When constancy of weight was attained, and all chloroform had been removed, the loss of weight of e entire apparatus represented the chloroform ; whilst the gain in 'ht of the apparatus (as compared with its weight before intro- VOL. XLIX. 0 s 184 Dr. Wright and M< mn. Hkompeon .-md Leon. [Feb. 12, ducing the mixture) represented the water and acetic acid jointly, from which the water was obtainable by subtracting the weight of acetic acid deduced from the previous titration. A number of pre- liminary experiments showed that the sulphuiic acid drying tnl sufficed to retain all traces of acetic acid carried away by the current of air, whilst, on the other hand, it did not permanently absorb chloroform, and did not sensibly act on the chloroform so as to bi it up, or hydrolyse it into hydrochloric and formic acids, iJch proportions as to produce two masses of approximately the composition of a pair of conjugate alloys, and these alloys were then mixed together and well stirred, a nearer approxima- tion to truly conjugate compositions might be attained. We tried several experiments in this direction, but the results were far less sharp and well defined than those obtained with chloroform, wate,r, and acetic acid, where a much more thorough intermixture by agita- tion in a closed vessel could be readily effected. Thus, in one set of experiments we first prepared two alloys of approximately conjugate composition for a temperature of about 800° (Part II, ' Boy. Soc. Proc.,' vol. 48, p. 29), viz. :— 1891.] On certain Ternary Alloys. 191 Tin. Lead. Zinc. Heavier alloy 29-5 50-0 20-5 Lighter alloy 28'5 13-0 58-5 Two parts of the first and one of the second were then melted in two separate crucibles, and the contents of one crucible poured into the other, and well intermixed by vigorous stirring for some minutes; the whole was then poured into a red-hot narrow clay crucible, and maintained at near 800° for 8 hours in the lead bath. Simultaneously, a second clay test-tube was heated, containing a similarly prepared mixture of one part of the first alloy to two of the second. The compound ingots ultimately obtained were analysed with the following results, obviously showing much less close agree- ment than in the case of the chloroform, water, and acetic acid ; more- over, the difference in tin percentage between top and bottom underwent changes in opposite directions to extents closely com- mensurate with those calculable from the values deduced in Part I for the differences in the curves obtained according as lead or ziuc predominated in the original mass, or as the two were present in equal proportions. Heavier end. Lighter end. Excess of tin percent- age in lighter over that in heavier. Tin. Lead. Zinc. Tin. Lead. Zinc. parts of first alloy to 1 of second 30-16 28-05 + 2-11 47-09 52-34 -5-25 22-75 19-61 + 3-14 26-39 28-76 -2-37 11-41 11-69 -0-28 02-20 59-55 + 2-65 -3-77 4-071 4-48 part j of second alloy to 1 of first Difference . . Similarly, in two other sets of experiments, the following tin per- sntages were obtained, again showing a notable divergence in the suits according as the heavy alloy was employed to doubl he ctent of the lighter one, or only half. 192 On certain Ternary Alloys. [Feb. 12, M. • n .. f end. . Lighter end. Excess in lighter And. i Heavier end. Lighter end. BZOMI in lighter end. 2 parts of first heavier alloy to 1 of lighter. 15-39 17-51 + 2-12 I':!'!', 23-39 -0-08 2 parts of first lighter alloy to 1 of heavier. Difference 15-07 + 0-32 19-56 —2 05 + 4-49 2-37 22 -57 + 0-88 25-41 —2-02 + 2-84 2'90 In every case the same general result is noticed, that when tl two approximately conjugate alloys are intermixed in such proportic that lead predominates over zinc in the total mass, or vice versa, differences in tin percentage between the two ends of the compounc ingots formed are of the same kind as those observed in Part I wii original mas-es containing lead and zinc in different ratios : that when lead predominates a point is obtained belonging to curve underlying that pertaining to cases where zinc predominates ; whence it appears pretty certain that, whatever the causes may bej that prevent truly conjugate alloys from being obtained under the conditions of the one set of experiments (whether incomplete inter- mixture, or something else), they also operate in the other series observations. Taking into account, however, the fact that in the experiment with chloroform, water, and acetic acid truly conjugate mixtures wer obtained when a sufficient amount of intermixture by agitation occurred, but not till then, the final conclusion appears to be warrant thai the proposition set forth, by Sir Q. G. Stokes is a perfectly correct and that the divergences noticed in certain of the alloy experiment are due to the inherent nature of the case as regards the difficulties in the way of obtaining sufficiently complete intermixture : possibly these difficulties might be overcome by enclosing the fused mixtures of metals in a stoppered vessel or crucible-flask of clay, and agii this by long continued shaking about, whilst keeping it sufficiently hot in some kind of muffle furnace ; bat the appliances at our dis- posal have not permitted us actually to decide this point experi- mentally. The difficulty of carrying out such experiments is further enhanced by the circumstance that metallic alloys, when intermixed by vigorous agitation, do not appear to separate again from one another anything like so readily as such substances as chloroform and water or ether and water; small vesicles or droplets of the b< alloy remain suspended in the lighter one (and vice versi) for long 1891.] On the Structure of Amoeboid Protoplasm, Sfc. 193 periods of time, necessitating the maintenance of a nearly equable temperature, and the remaining at rest for many hours, before the top part of the mass becomes sensibly free from suspended portions of the heavier alloy, and the bottom part from similar portions of lighter alloy. The analytical numbers obtained on examining different layers of the compound ingots prepared in the experiments described in the earlier parts of these researches long ago convinced us of this ; but, in addition, an actual visible presence of suspended particles of one alloy in the midst of another, even after 8 hours tranquil fusion, may be often observed in the case of silver-lead-zinc and silver-bismuth alloys \\here the proportions of metals used are such as to form mixtures containing considerable amounts of Ag4Zn5 : by the aid of a lens, or even with the naked eye, red particles disseminated through a much lighter coloured matrix can often be distinguished on examining the central portions of an ingot that has been filed smooth and bright, and then kept for awhile so as to allow the red tinge to develop. " On the Structure of Amoeboid Protoplasm, with a Com- parison between the Nature of the Contractile Process in Amoeboid Cells and in Muscular Tissue, and a Suggestion regarding the Mechanism of Ciliary Action." By E. A. SCHAFER, F.R.S. Received January 26, 1891. It has been shown by the researches of numerous histologists, of rhom Heitzmann and Frommann, and, in this country, Klein, must be skoned the pioneers, that the protoplasm of many cells exhibits the ippearance of a network containing an apparently homogeneous iterial in its meshes. The network is known as the reticulum or Bioplasm, the clear material in its meshes as enchylema (Carnoy) jr hyaloplasm. In many cells it is not difficult to observe this structure even without the addition of reagents, but in amoeboid cells ich as the white blood corpuscle and the amoeba it is less obvious, id its presence has not been generally conceded. Recently, afessor Strieker* has published a photograph of an amoeboid white lood corpuscle, taken instantaneously by aid of the electric light, rhich shows the reticular appearance in quite an unmistakable iner; it must be granted, therefore, that the amoeboid white, lood corpuscle also has this structure. Previously to the appearance of Professor Strieker's photograph, I id myself for some time been engaged in investigating the structure amoeboid cells with the aid of photography. Being unprovided * ' Wiener Medic. Jahrb.,' 1890. 194 Prof. E. A. Schaf< r [Feb. IL>, with the appliances necessary for photographing by the electric light, I was unable to obtain instantaneous photographs, and could not photograph the corpuscles while actually living and moving. I accordingly adopted a method of suddenly killing the corpuscles whilst still in the amoeboid condition with their pseudopodia extended. It is well known that with most methods which are employed to fix the white blood corpuscles there is time for a contraction of the protoplasm to be produced, so that the pseudopodia are withdrawn and the corpuscle becomes spherical. The method which I have used consists in the instantaneous application of a jet of steam to the surface of the cover-glass. A preparation of blood, preferably from the newt (Triton cristatus), is made either in a moist chamber or in the usnal way on a glass slide. In a short time the white corpuscles become highly amoeboid and throw out psendopodia, which may- spread themselves in a thin layer upon the cover glass in a manner which is perfectly adapted for their being accurately observed. If the steam be now turned on for an instant, the cells are suddenly killed, and remain exactly in the condition in which they happened to be when the heat was applied. They can be examined and phot graphed thus, or may first be stained by luematoxylin, with or with- out being previously treated with alcohol. In all cases they exhibit the same general structural appearances, and these appearances can even be detected, but with greater difficulty, in the cell whilst still living. Leaving the nucleus, which beautifully exhibits the karyoplasmic network, out of consideration, the most striking point in all amoeboid white corpuscles thus prepared is the contrast between the proto- plasm of the body of the cell and that of the pseudopodia. For whilst the former exhibits, according to focus, either a finely punctated or a reticular aspect, and stains decidedly with hiemato- xylin, the pseudopodia exhibit not the faintest trace of structt and re-main almost entirely unstained. In other words, the protoplasm is composed of two morphologically distinct parts, one which exhibits a reticnlar arrangement and has an affinity for hsematoxylin, and another which shows to the best optical appliances no structural arrangement, and is also chemically different, as is shown by its behaviour to staining reagents. The observation here recorded is not an isolated one. Almost all observers who have given special attention to the matter have failed to detect a reticular structure in pseudopodia, whether of amoeboid cells of higher organisms or of the Bhizopoda. To Butschli's theory of the structure and activity of protoplasm,* whereby he endeavours to show that the reticular appearance and amoeboid phenomena may be explained on the assumption that protoplasm is » ' Heidelberg Verhandlungen,' 1890 ; and ' Biologisches Centralblatt,' 1890. 1891. J On the Structure of Amoeboid Protoplasm, 8fc. 195 not an actual network with enchylema, bnt rather a frothy mixture of two dissimilar substances, this absence of all apparent structure in pseudopodia offers an admittedly serious difficulty, which he en- leavours to surmount by assuming that the same frothy structure is sally present in the pseudopodia as in the body of the cell, but that owing to thinning out it cannot be detected. But apart from the unlikelihood of our not noticing such structure in the pseudopodia if it were really present, since they are especially well adapted for minute observation, the reticular and the homogeneous substances should, according to this assumption, pass gradually the one into the other, for the thinning-off of the pseudopodia is frequently gradual. The contrary is, however, the case. The line of demarcation of the reticular substance is always quite sharp, and does not thin off into the homogeneous substance of the pseudopodia. Strieker's photograph is also really evidence in the same direction. The corpuscle taken is spherical or nearly so, i.e., is in the contracted andition. It has, however, one small pseudopodium. This is abso- itely without structure ; it is the spherical part of the cell which lows the reticulum. It is well known that if white corpuscles (and contracted amoeboid ?ells generally) are artificially stimulated, they are always spherical. The spherical form is, in fact, the contracted condition ; it is only in the absence of any obvious source of excitation that the corpuscle >ws out pseudopodia. The spherical condition is immediately produced by electrical or mechanical stimuli ; no doubt, the constant icchanical stimulation which the cells receive in the circulating lood maintains them in the spherical form which they always diibit whilst moving within the blood-vessels. Possibly, also, the Dntact of a foreign particle, causing the contraction and with- Irawal of the protoplasm which it touches, and the consequent iception of the particle, is another instance of mechanical stimula- tion. Now, in the contracted corpuscle, the whole cell appears reticular, id the reticulation is even better marked, i.e., coarser, than that sen in the spread out corpuscle. The pseudopodial protoplasm or iyaloplasm has, in fact, been withdrawn into the meshes of the imework or spongioplasm. The protoplasm of such an amoeboid cell as the white blood rrpuscle may, therefore, be regarded as composed of two distinct ibstances, spongioplasm and hyaloplasm. Spongioplasm has a reti. sular or sponge-like arrangement, an affinity for staining fluids, is firmer than the hyaloplasm (but, perhaps, not actually solid), and is, in all probability, highly extensile and elastic. Hyaloplasm, on the 3ther hand, is structureless, has little or no affinity for stains, and is lighly labile and fluent. It is by the active flowing of the hyalo- 196 Prof. E. A. Schafer. fFeb. plasm, not by the contraction of the spongioplasm (as conceived Carnoy*), that the movements of cells are produced.f Of the t substances, the hyaloplasm is the more active, the spongioplasm more inert. The spongioplasm forms, in fact, a sort of framewi supporting the hyaloplasm, and into which under the influence stimuli the hyaloplasm becomes wholly withdrawn. To adopt Brnecke's well-known terminology, the hyaloplasm is the zooid, the spongioplasm its oscoid. Whether one or other of these two substances is ever wholly absent from the protoplasm of cells is a question which cannot at present be decided. There are cells and unicellular organisms, both animal and vegetable, in which no reticular structure can be made out, and these may be formed of hyaloplasm alone. In that case, this must be looked upon as the essential part of protoplasm. So far as amoeboid phenomena are concerned, it is certainly so ; but whether the chemical changes which occur in many cells are effected by this or by spongioplasm is another question. Certainly, the reticulnm is always very well marked in cells in which considerable chemical changes are produced, e.g., gland cells. The movements within plant cells must also be regarded as due the flowing of hyaloplasm. It is, indeed, impossible to conceive t the contraction of a reticulum could produce the circulation of protoplasm which is seen within a cell of Valltsneria. How t flowing is produced is an entirely different question, and one w must at present remain unanswered. If now we compare the structure of protoplasm with that striated muscle, we find many points of coincidence. As is we known, the muscle columns of the wing muscles of insects ("wing- fibrils " of authors) are divided by transverse partitions (membranes of Krause) into a series of segments (sarcomeres, Aluskel-kastchen. of Krause), each of which contains a sarcous element or disk of anisotropous sarcous substance (which is really formed of two halves, their junction being often visible as the line of Hensen), and a homo- geneous isotropous substance, which in the extended muscle occupies the intervals between the sarcous element and the transverse mem- brane. As I have elsewhere recently shown,J the substance of the sarcous element is penetrated by pores or canals which extend in each half of the element as far as the line or plane of Hensen, and which are occupied by clear substance continuous with the homogeneous sub- stance of the intervals. The substance of the sarcous element stains with heematoxylin and similar reagents, while the homogeneous substance of the clear intervals remains unstained. When the * ' Biologie Cellulaire,' 1886. t Of. Leydig, ' Zelle u. Gewebe,' Bonn, 1885. J ' Monthly International Journal of Anatomy and Physiology,' voL 8, 1891. 1891.] On the Structure of Amoeboid Protoplasm, tyc. 197 muscle contracts, the homogeneous substance passes from the intervals into the pores of the sarcous element, and thus enlarges the latter, while the clear intervals are proportionately shortened, so that in extreme contraction they may disappear, and the swollen and bulged sarcous element may almost abut against the tranverse membranes. On the other hand, when the contraction passes off, and the 'muscle becomes extended, the homogeneous substance passes out of the pores of the sarcous element into the clear intervals ; the latter become manifest, and the sarcous element proportionately diminished in bulk. It is hardly possible that the resemblance of these changes to those which occur in the protoplasm of an amoeboid cell is merely accidental — difficult not to believe that the perforated sarcous substance is the spongioplasmic " cecoid," the clear labile substance the hyaloplasmic " zooid." This conception of the structure and mode of activity of the amoeboid cell and of muscle, whilst bringing them under exactly the same category, and thus tending to simplify our ideas regarding con- tractile phenomena, may also serve to aid in the elucidation of certain uestions in connection with those phenomena which have long 'resented difficulties to the physiologist and pharmacologist. For pie, with regard to the movements of amoeboid cells, the question has been frequently discussed, and never satisfactorily answered, whether we are to regard the withdrawal of the pseudo- podia into the body of the cell as the condition of rest, and the protrusion of the pseudopodia as the condition of activity, or vice versa. Viewed by the light of the above observations, it is clear that neither state is to be regarded as a resting condition ; both are mani- festations of activity ; both are produced by flowing of the hyaloplasm, limilarly, in the case of muscle, the passage from the contracted to e extended condition can no longer, as is so frequently assumed, be >ked upon as a merely passive change of state, but must be rded, no less than in the case of the passage from the extended to e contracted condition, as produced by flowing of hyaloplasm. In .e one case this flows into pores of the spongioplasm — this is the ndition called contraction, and ordinarily regarded as the active ,te ; in the other case there is a flowing of the hyaloplasm out the pores of the spongioplasm, by which movement the condition extension is determined. That different chemical and electrical anges accompany, perhaps determine, these different directions of movement is well known. It is also known that the process of exten- ion is influenced by drugs, independently of the action they may :ert upon that of contraction (Brunton, Ringer). But whether the ihemical and electrical changes, and those produced by drugs, occur in the hyaloplasm, or in the spongioplasm, or in both substances, is a uestion which, as in the analogous case of the amoeboid cell, cannot On the Structure of Amceboid Protoplasm, fyc. [Feb. 12, at present be decided. The same remark may be made with respect to the question of active participation by the spongioplasm in the pro- duction of the movements of the hyaloplasm. It is, however, quite r.-rt-iiu from the observation of the movements of the hyaloplasm of psendopodia, which may actively flow in different directions, even when far removed from the spongioplasm, that it is the hyaloplasm which is to be regarded as the physically active part of protoplasm, and therefore also presumably of muscular substance. Lastly, there is another form of protoplasmic activity, viz., ciliary motion, which cannot be left out of consideration in any attempt to explain the manner in which the contractile manifestations of proto- plasm are produced. On this matter I have no new facts to record, and the suggestion therefore that I have to make must be under- stood to be a purely theoretical deduction from analogy, and not] based upon actual observation. At the same time it does not, so far as I know, stand in contradiction to any known fact, suggestion is briefly this : — If we suppose that a cilium is a hollow curved extension of the cell, occupied by hyaloplasm, and invested by a delicate elastic membrane, then it must follow that if there be aj rhythmic flowing of hyaloplasm from the body of the cell, into out of the cilium, an alternate extension and flexion of that pi would thereby be brought about. The movement would in fact be] produced by an action which would be practically the same as that by which the amoeboid movements of cells and the contraction and extension of muscle are probably effected. The same result might be got, supposing the cilium to be a straight and not a curved extension oi the cell, if the enveloping membrane were thicker (or otherwise less . extensible) alorg one side than along the other. This assumption would also enable one better to account for the spiral direction of the movement of certain cilia ; for this form of movement would be produced if the line of lessened extensibility in them were to pass in a corkscrew fashion along the cilium in place of straight along one side, as might be assumed for ordinary cilia. 1891.] The Pathogenic Fungus of Malaria. 199 V. "On the Demonstration by Staining of the Pathogenic Fungus of Malaria, its Artificial Cultivation, and the Results of Inoculation of the same." By Surgeon J. FENTON EVANS, M.B. Communicated by Professor VICTOR HORSLEY, F.R.S. (From the Laboratory of the Brown Institution.) Received February 7, 1891. (Abstract.) The discovery of organisms constantly concomitant with manifes- tations of malaria was made by Laveran in 1880. His researches have since been corroborated and amplified by numerous observers in different parts of the world, amoug whom must be mentioned, Marchiafava, Celli, Golgi, and Guarnieri, in Italy ; uncilman, Osier, and James, in America ; and Vandyke Carter, in dia. The foreign structures which all of the above-named inves- igators agree in finding in the blood during or after attacks of ague ay be grouped into the following classes : — 1. " Cystic" bodies or spores, 2 to 11 [t in diameter, round, trans- parent, encapsuled bodies of variable dimensions. 2. Crescentic bodies, 8 to 9 /* long and 3 fi broad. 3. Plasmodia malariee, organisms as variable in size as the " cystic " bodies or spores, possessing the power of amoeboid movement, and so closely associated with the red blood corpuscle that hitherto the majority of observers have con- sidered them to be parasites situated within the red blood cells. 4. Mobile filaments, 21 to 28 /* long. Despite the general concord of the observations, the subject has not advanced beyond the stage of recognition of these structures in the blood, and that, too, only while in the fresh state. No method had hitherto been discovered of preparing permanently stained specimens of the organism. It had never been isolated or classified, nor when thus separated had its pathogenic qualities ever been tested by experiments on lower animals. It was thus clear that much remained to be done, and in the paper are recounted the attempts made to place the subject on a satisfactory footing. The author has found that it is possible to stain the or-" ganisms with an anilinised alkalised solution of rosanilin hydro- chloride after treatment with bichromate of potash, and after treatment with dilute sulphuric acid by an anilinised alkalised »'ution of Weigert's acid fuchsin. TOL. XLIX. p 200 Pre*ent*. [Feb. 12, Another method of staining consisted in the saturation of the tissue with a copper salt and its redaction by sulphuretted hydrogen pre- vious to coloration with anilinised alkalised acid fnchsin. By these staining methods the organisms have been demonstrated in the blood, and also in the tissues. And some new, hitherto un- recognised features are described, among which may be mentioned what appears to be the germination of the spore in the blood, the existence of a comma-shaped body and of mycelium in the spleen and Peyer's glands, and the localisation of the plasmode, i.e., in relation to the blood corpuscles. The isolation of the organism and its artificial cultivation have been successfully carried out, and it is shown that this result entirely depends for its success upon the fact that the nutrient media must be previously treated with living blood, i.e., before rigor mortis has set in. Alteration in the chemical composition of the nutrient medium, consisting in the addition of glucose, together with iron or haemo- globin or fresh blood, to the non-peptonised beef broth, elicited the interesting fact that, under these circumstances, the organism can pass to a more highly developed state, displaying the structure and fructification of a highly organised fungus, but differing in certain important features from any fungus hitherto described. Inoculation of guinea pigs, monkeys, and rabbits with the growths in various nutrient media has produced a frequently fatal disease, which, although not characterised in these animals by the symptoms of classical intermittent fever, yet displayed in a number of instances a definitely intermittent character. It was further, whatever its clinical character, invariably accompanied by the appearance of the characteristic organisms in the blood drawn after death from the right ventricle. It is accordingly concluded that the malarial fungus is capable of being cultivated outside the body and has been proved, to posse pathogenic qualities. Presents, February 12, 1891. Transactions. Brisbane : — Royal Geographical Society of Australasia (Queenslant Branch). Proceedings and Transactions. Vol. V. Part 2. 8\ Brisbane 1890. The Society. Buenos Ayres : — Museo de Productos Argentines'. Boletin Mensuj Ano III. Num. 31. Resultados Botanicos de Esploracione hechas en Misiones, Corrientes, . In the application that wo have to make of these equations, fa, fa, *i, i'a will represent respectively currents and electromotive forces in the battery and telephone branches of the combination. The re- ciprocal property may then be interpreted as follows : — If *» = 0, and fa = n*» (2). B3-AC In like manner, if we had supposed *i = 0, we should have found B fa = B2-AC (3), showing that the ratio of the current in one branch to an electro- motive force operative in the other is independent of the way in which the parts are assigned to the two branches. We have now to determine the constants A» B, C in terms of the electrical properties of the system. If fa be maintained zero by a suitable force *2, the relation between ^i and *i is *i = -Afa. In our application, A therefore denotes the (generalised) resistance to an electromotive force in the battery branch, when the telephone branch is open. This resistance is made up of /, the resistance in the battery branch, and of that of the conductors a+c, b + d combined in parallel. Thus, (~ i_-\ fiA_j\ (4). Inlikemanner, C = a+o+c (4'). To determine B let us consider the force ^j which must act in e in order that the current through it (fa) may be zero, in spite of the operation of iv We have 1rt = Ufa. The total current fa flows partly along the branch a+c, and partly along 6 + d. The current through a + c is 1 a + c — a+c a+6+c+a b + d 1891.] Application to Periodic Electric Currents. 207 and that through b + d is (q + c) -<^i /gx a+b+c+d The difference of potentials at the terminals of e, supposed to be interrupted, is thus a+b+c+d be — ad /HV or B = — TT— -—7 ................. (')• a+b+c+d By (4), (4'), (7) the relationship of ^i, i^ to T^I, ^2 is completely determined. The problem of the bridge requires the determination of the cur- rent yr2, as proportional to ir1, when 1rt = 0, that is, when no elec- tromotive force acts in the bridge itself, and the solution is given at once by simple introduction into (2) of the values A, C, B from (4), (4'), (7). If there be an approximate balance, the expression simplifies. For be — ad is then small, and B2 may be neglected relatively to AC in the denominator of (2). Thus, as a sufficient approximation in this case, we have ad — be . 1^ a + b + c + d ,x " a+b+c+d J in agreement with the equation used by Mr. Heaviside for simple resistances. The following interpretation of the process leads very simply to the approximate form (8), and may be acceptable to readers less familiar with the general method. Let us first inquire what E.M.F. is necessary in the telephone branch to stop the current through it. If such a force acts, the conditions are, externally, the same as if the branch were open, and the current y^ in the battery branch due to an E.M.F. equal to ^ in that branch is i^/A, where A is written for brevity as representing the right-hand member of (4). The difference of potential at the terminals of e, still supposed to be open, is found once when y^ is known. It is equal to : ex (5) — ere B is defined by (7). In terms of ^i the difference of poten- tials is thus B^i/A. If e be now closed, the same fraction expresses e E.M.F. necessary in e in order to prevent the generation of a rrent in that branch. i'os Lord Raylcigh. On the Bridge Method in its [Feb. The case that we have to deal with is when *i acts in /, and there is no E.M.F. in e. We are at liberty, however, to suppose that two opposite forces, each of magnitude Bi^/A, acts in e. One of these, as we have seen, acting in conjunction with *, in /, gives no current in e; so that, since electromotive forces act independently of one another, the actual current in e, closed without internal E.M.F., ia simply that due to the other component. The question is thus re- duced to the determination of the current in e due to a given E.M.F. in that branch. So far the argument is rigorous ; but we will now suppose that we have to deal with an approximate balance. In this case an E.M.F. in e gives rise to very little current in /, and in calculating the cur rent in e we may suppose / to be broken. The total resistance to the force in e is then given simply by C of equation (4'), and the approxl mate value for ^-2 is derived by dividing — B*,/A by C, as we found in (8). A continued application of the foregoing process gives W^i in the form of an infinite geometric series : — This is the rigorous solution already found; but the first term ol the series suffices for practical purposes. The form of (8) enables us at once to compare the effects of inci incuts of resistance and inductance in disturbing a balance. For ad = be, and then change d to d + d1 where d' = d\ + id't. The valu« of Y^z/^i is proportional to d', and the amplitude of the vibratoi current in the bridge is proportional to Mod d', that is, \/(^V+dV). Thus d\t d't are equally efficacious when numericallj equal. The next application that we shall make of (8) is to the general- ised form of Schwendler's problem. When all else is given, hoi should the telephone, or other receiving instrument, be wound order to get the greatest effect ? If by separation of real and imaginary parts we set the factor in the denominator of (6) with which we are concerned becomes and the square of the modulus is given by Mod2 = (ei + ri)l + (ej+r,)* (10). 1891.] Application to Periodic Electric Currents. 209 In this equation et, rt are essentially positive, while e2, r2 may be either positive or negative. If et and e2 are both at disposal, the minimum of (10), corresponding to the maximum current, is found by making ei = 0, 62 = — r-i ............ (11). But this is not the practical question. As in the case of simple resistances, what we have to aim at is not to render the current in the bridge a maximum, but rather the effect of the current. Whether the receiving instrument be a galvanometer or a telephone, we cannot in practice reduce its resistance to zero without at the same time nullifying the effect desired. We must rather regard the space available for the windings as given, and merely inquire how it may best be utilised. Now the effect required to be exalted is, cceteris paribus, proportional to the number of windings (m) ; and, if the space occupied by insulation be proportional to that occupied by copper, the resistance varies as m2. So also does the inductance ; and accordingly, if the instrument be connected to the bridge by leads sensibly devoid of resistance and inductance, (12), where ej, e2 are independent of m. The quantity whose modulus is to be made a minimum by variation of m is thus i (r2 + mze2) . m m and we have » This is a minimum by variation of m when Mod («•! + «-,) = Mod (eJi+tez) .......... (13). We may express this result by saying that to get the best effect the instrument must be so wound that its impedance is equal to that of the compound conductor r^ + irz. If for any reason the inductances can be omitted from consideration, then the resistance of the instru- ment is to be made equal to rj, in accordance with Schwendler's rale. The case of the "battery" branch may often be treated in like manner. As Mr. Heaviside has shown, if a number of cells are 210 Lord Rayleigh. On the Bridge Method in its [Feb. 19, available for ordinary resistance testing, they should be combined, that their resistance is equal to that («i) of the corresponding coi bination of wires in parallel. Periodic currents may be conceived arise from the rotation of a coil in a magnetic field of given streng If the space occupied by the windings of the coil be supposed to given, their number m will be determined by the condition of eqi impedances. Thus, if (q + c) (b + d) _ (14) Mod (/i + t/i) = Mod (*,+ «,) (15) in analogy with (13). The above is the solution of the problem, if the coils of the sendii and receiving instruments represent the whole of their respectii branches, and are limited to occupy given spaces. The inductanc and resistances cannot then be varied independently. But tht would often be no difficulty in escaping from this limitation. Tl inclusion of additional resistance, external to the instrument, only do harm ; but the case is otherwise with inductance, positive negative. If the inductance of the instrument added to r2, or to be positive, the total inductance may be reduced to zero by the ins tion of a suitable condenser, and this without material increase resistance. If the inductance be already negative, the remedy is so easily carried out; but, theoretically, it is possible to add necessary inductance without sensible increase of resistance, greater the frequency of vibration, the more feasible does this COT become. We may, therefore, without much violence, suppose tl the inductances of two branches can be reduced to zero with< additional resistance. Thus, , = 0, and the condition of maximum efficiency of the transmitting receiving coils is then given by Schwendler's rule, *i = fit fi = *i (!' These suppositions form a reasonable basis for further investif tion ; but conclusions founded upon them will be subject to examination, especially in extreme cases. We may also now introdi the promised simplification, a = c, b - d (II in accordance with which (8) becomes d-b 46 (19) 1891.] Application to Periodic Electric Currents. 211 Also i-i + «» = £(a + &) =i(ai + &i)+i*(a» + &») ---- (20). 2(o1+taa) ( ^ (ai + &i) (0261 + 0162) — 0*2 + 62) (ai 61 — 0262) XO-IN ' It may be well to examine, first, the consequences of (19), in the case of simple resistances. Here «! = 2o161/(o1 + 61), s2 = 0 (23). .n accordance with the plan proposed, we are to make e^ = 0, = 0 ;* ei = r, fi = Si. Our equation then becomes I /2 Here ai is still at disposal, and we see that according to (24) it ought to be diminished without limit. This conclusion does not harmonize with one obtained by Mr. Heaviside.f It must be ob- served, however, that ai = 0 is unpractical, involving, as it does, ' *i = 0, /! = 0. Even according to (24) there is little to be gained by diminishing a^ below, say, \ l>\. In this case |6i, /l = 51 = |61 ---- (25). uch an arrangement as (25) may be recommended for practical use. When bi is large, there may be advantage in taking a^ relatively smaller than in the above example. In such cases we approach the limiting condition of things, and have approximately fi = st = 2«! ............ (26), T5T ................. (27)' And the smallness of /i in comparison with bi may sometimes be a convenience. * These conditions require no attention in galvanometric testing with steady currents, being satisfied by p = 0, independently of the nature of the instrument. t Loc. cit., p. 120, " In conclusion, if, to measure a certain resistance, the best resistances for the galvanometer, battery, and the three sides, a, 5, c, were required, then we should have to make a = b = c = d = e =f." 212 Lord Rayleigh. On the Bridge Method in its [Feb. 10, The next remark tbat has to be made is that, even when the con- ductors, b and ; and, secondly, the introduction of extraneous condensers,* even with interchange, into the branches to be accurately compar may be a complication unfavourable to success. We will now resume the consideration of (19), supposing that ---- (28), (29), e — e!+e2 = n — tr2, srj + tj = «,— «-„ r,, *i, *2 being given by (20), (21). Thus, 16 and the question before us is how to make the modulus of the second fraction on the right a maximum by variation of a. In the de- nominator of this fraction r, and *i are real, and the modulus of b is v/(&i2 + &22). For the numerator we have 2(*,— i'go) a b so that PI i I , ~ ' " Also from the definition of « so that Thus and this is to be made a minimum by variation of 01, a^. IT •• (30), * The use of condensers or electromagnet! in the branches e and f stands, course, upon a different footing. 1891.] Application to Periodic Electric Currents. 213 We shall show presently that (30) can be reduced to zero; but for the moment we will so far limit the generality of a1} 0% as to suppose that «! = xbi, 02 = rb2, x being real and positive. (30) then reduces to \ &i2(l + aj) ; and by (29) Mod (d — 6) - \t 3 i /T Mod *• =: - Accordingly, the maximum sensitiveness cannot be attained until « is reduced to zero, so that al5 03 vanish. (31) may be regarded as a generalised form of (24), free from the limitation that 62 = 0, pro- vided a? be so taken that a^/b^ = a\fb\. We will now suppose in (30) that a\ and a? are both small, and in the first instance that b\ is finite. We have ..(32); and this reduces ultimately to its first term, depending upon the ratio only of ai and az. The expression vanishes if cti : a% be small enough, so that (30) can certainly be thus reduced to zero. It is remarkable that the expression for the sensitiveness should be capable of becom- ing infinite by suitable choice of «2. If we first suppose that a? is i absolutely zero, and afterwards that a-i diminishes without limit, the ultimate value of (32) is | &1v/0»i2+&22)» ™ place of zero. From the practical point of view, these conclusions from our equations are not particularly satisfactory. We began with certain ^proposals which, in ordinary cases, could be carried out ; but in the end we are directed to apply them to an extreme and impossible state of things. We have found, however, in what direction we must tend in the search for sensitiveness; and useful information may be gathered from (32). In practice ax could not be reduced below a certain point. The question may then be asked, what is the best value of a2, when a! is given ? From (32) we find at once that ............. (33), 0i then becoming 61 2-f 2aJ)i(ai k °> l + 6») (M From (37) we see that the increase of Oj is favourable, especially if the sign be the same as of 6a. Even if a? = 0, (37) now assuming the form )TT«- • (4°) 1891.] Application to Periodic Electric Currents. 215 can be reduced to zero by taking cti small enough. But of course (37) ceases to be applicable unless fej be small relatively to a^ In correspondence with (40), e> = % 01, e2 = — i fc2 (41) ; As an example of (37), suppose Then (37) = — nearly. 640 Also approximately If 62 represent the stiffness of a condenser, /2 must be a positive inductance, and its magnitude, relatively to /i, would probably con- stitute a difficulty. As an example, with a^ equal to zero, take td\ = -jJjj &2» fl2 == 0. en (37) = (40) = ^ b? nearly, and * 2 &2> /I = I *2> /2 = — To o far as the general theory is concerned, it is a matter of indif- ference whether the indicating instrument be in the branch e, or in /. The latter corresponds to the connections in De Sauty's method of testing condensers by means of the galvanometer. In practice, more space would probably be available for the coils of a transmitting instrument than of the receiving instrument, at least, if the latter be a telephone ; and this would tell in favour of choosing that branch for the transmitter which should have the larger time constant (L/R). To get an idea of the relative capacities, resistances, and induct- ances involved, we must assume a particular pitch. A frequency suitable for telephonic experiments is 1000 per second, for which p = 2000 TT. Thus, if the value of a2 for a condenser of capacity C, and for an inductance L, and that of ax for a resistance B, are all numerically equal, BR = 2OOOn-L = 1 R be 1 ohm, equal to 109 C.G.S., the corresponding capacity is l'6xlO~13 C.G.S., equal to 160 microfarads, and the corresponding OL. XLIX. Q 2000 TrC' 21 G On the Bridge Metliod and Periodic Currents. [Feb. I1.1. inductance is TSxlO* C.G.S. Again, if C be one microfarad, equal to 10- M C.G.S., R is 160 ohms, and L ia 2'5 x 107 cm. In the preceding calculations e and / are supposed to be adjusted to the values most favourable to the effect in the receiving instru- ment. A question, which arises quite as often in practice, is how to make the best of given instruments. The full answer is necessarily somewhat complicated ; for there could be no objection to the inser- tion of a condenser for example, if the sensitiveness could be im- proved thereby. In what follows, however, the transmitting and receiving branches will be supposed to be fully given, so that e and / are known complex quantities ; and the only question to be considered is as to the most suitable value of a, assumed to be equal to c. For this purpose the modulus of the second fraction on the right in (19) is to be a maximum, or that of is to be a minimum, by variation of a. The problem thus arising of determining the minimum modulus of a function of a complex quantity may be treated generally. Let F (z) = F (x + iy) = 0 and let it be required to find when the modulus2 of F (z), viz.,. , is a minimum by variation of x,y. We have ax And in general _ dx dy +* = o .... (4*). ay dy dtp _ dy- Ty~ ~te In oi-der that (44), (45) may both obtain, we must have eit 0- + yr2 = o, or else T~ — ®» ~T~ *"~ ®> ~j~ dx dy dx The latter conditions are equivalent to A dy For example, let F(z) = where a, ft are complex constants. (46). (47), 1891.] Influence of Pressure on the Spectra of Flames, 217 The application of (46) gives and Ft*) = {1+/O/:})}2 .............. (49). We see then that the modulus of (43) will be a minimum^ when (50)' and in taking the square root the ambiguity must be so determined as to make the real part of a positive. Equation (50) coincides with that obtained by MIN Heaviside for the case where all the quantities axe real. II. " On the Influence of' Pressure on the- Spectra of Flames." By G. D. LIVEING, M.A., F.R.S., Professor of Chemistry, and J. DEWAR, M.A., F.R.S., Jacksonian Professor, University of Cambridge.. Received January 22> 1891. "We have already described (' Phil. Trans.,*" A, 1888) the remarkable pectrum of the oxy -hydrogen flame burning at the ordinary atmo- iheric pressure. Recently we have examined the spectrum of the me flame at various pressures : hydrogen burning in excess of xygen up to a pressure of 40 atmospheres, said oxygen in excess of hydrogen up to a pressure of 25 atmospheres, also that of the mixed gases burning in. carbonic acid gas. The apparatus employed was an adaptation of one of the tubes id in oar experiments on the absorption spectra of compressed .ses ('Phil. Mag.,' September, 1888, and 'Roy. Soc. Proc.,' vol. 46, p. 2:22). It consisted of a steel cylinder, about 50 mm. in internal diameter and 225 mm. long, fitted at one end with a quartz stopper, in the annexed figure, and with a jet, &,. for burning the gas, pted by a properly fitting union joint to the opposite end. There ere two tubes, c and d, connected to the cylinder at the sides, of hich one, e, served for the introduction of gas, while the other, d, fitted with a stopcock and was used to draw off the water formed, to reduce the pressure of the gas in the cylinder if that was ired. The flame was observed, nearly end on, through the quartz pper. The whole apparatus was kept cool by a stream of cold ter running on to a sponge cloth wrapped round the cylinder. In course of the tube conveying gas to the jet b was interposed a all cylinder, e, in which sodium was placed, and by heating this, e gas entering could be charged with sodium vapour. Q 2 218 Profs. G. D. Liveing and J. Dewar. [Feb. 19, The gases were supplied from steel cylinders into which they had been compressed, and the pressure was registered by a gauge attached to the tube by which the gas entered the experimental cylinder. Commercial compressed gases were used, containing a sensible per- centage of air. When hydrogen was the gas forming the burning jet, it was lighted at the end of the tube 6 before introducing it into the experimental cylinder. When it was desired to have a jet of oxygen burning in hydrogen, this could be managed by introducing oxygen through the second tube and increasing the supply of hydrogen until the flame passed over to the oxygen jet. The same result was some- times attained by first filling the experimental cylinder by a gentle stream of hydrogen "through the side tube c before the end with the tube ft was screwed on ; the hydrogen as it issued was then lighted, and the jet, with a gentle stream of oxygen issuing, inserted and screwed down. The stopcock s was kept open until this was done, and then by closing s, and admitting more gas from the reservoirs, the pressure in the ^experimental cylinder oould be increased at pleasure. Hydrogen Burning in Oxygen. The first observations were made with a jet of hydrogen burning in oxygen. As the pressure rose, the luminosity of the flame in- creased, as long ago described by Frankland (' Experimental Researches,' p. 905). The colour of the flame, viewed end on, was yellow, as if it contained sodium ; but, on examining it with a spectroscope, it was found to give a continuous spectrum intersected by many shaded bands, and the D lines of sodium were only faintly present. The shaded bands were faint at a pressure of 5 atmo- spheres, but at pressures of 20 atmospheres and upwards they came oat strongly. They were evidently the absorption bands of N0£» 1891.] Influence of Pressure on the Spectra of Flames. 210 derived from the residue of atmospheric air mixed with the condensed gases. We took a photograph of them, and on comparing1 this with a photograph of the N02 bands, we found the two to be identical. Except for the bands, and the bright lines of sodinm, the spectrum appeared to be continuous, and to extend from about X 6200 to X 4150, with the brightest part about X 5150. It increased in brilliance as the pressure increased, as well as- in extent, being visible at 3 atmospheres pressure from about X 6720 to X 4040. The greater distinctness of the N02 bands at the higher pressures was due both to the greater brightness of the continuous spectrum and* to the greater quantity of NO2 formed. A large quantity of water accu- mulated in the experimental tube, and when this was drawn off by the stopcock s, it effervesced with escape of NO, and was found to be strongly acid. A specimen titrated was found to contain very nearly 3 per cent, of nitric acid. The observations were continued up to a pressure of 4*0 atmospheres-. There was no indication that the con- tinuous spectrum had any connexion with the line spectrum of hydrogen. There was no increase of brilliance in the neighbourhood of the C, F, or G lines of hydrogen. The characters of the spectrum were, however, better seen in the absence of NO2, and will be de- scribed in the next section. Oxygen Burning in Hydrogen. In this case the colour of the flame was very different from that of lydrogen burning in oxygen^ Instead of being yellow, it appeared, the unaided eye, to have a lavender hue. In the spectroscope it showed a perfectly continuous spectrum, brightest in the green, about the region of the Frannhofer line 6, and very gradually fading away on either side. On the red side it could be just traced up to about X 6150, and on the violet side to about X 4285, at ordinary pressures. The sodium lines were absent. With increase of pressure it in- creased very much in brightness, and at 8 atmospheres pressure it could be traced as low as X 6630 and as high as X 3990. The dispersion used was that of a direct- vision spectroscope (such as was described by usr ' Boy. Soc. Proc.,' vol. 41, p. 449), equivalent to three prismd of white flint glass, but the collimator and telescope very short, so as to obtain plenty of light. With less dispersion, 3rhaps, the continuous spectrum might have been traced further. >hotographs, however, showed that it scarcely extended into the Itra- violet. There was no indication that this- spectrum was due to expansion of the lines of either the first, or second, spectrum of lydrogen. It is true that the maximum brightness (which could not determined with any great accuracy) was not very far from F, but indication of any second maximum in the neighbourhood of either 220 Profs. G. D. Liveing and .T. Dewar. [Feb. 19, C or G, or anywhere else, could be detected. The pressure was carried up to 12 atmospheres, and at this pressure the visible Spectrum was brilliant, but, in the ultra-violet, photographs showed that the spectrum consisted only of what we have called the " water- spectrum," very strong and sharp. The lines of this spectrum showed no signs of expansion even at a pressure of 12 atmospheres, and, though much more intense than at ordinary pressures, remained •clearly defined. Observations were continued .with the eye up to 25 atmospheres pressure, but no trace of emission, or absorption, corresponding to •either spectrum of hydrogen could be detected, and it is doubtful if either spectrum can 'be produced in such a flame. Since the formation •of steam from its component gases is attended with a diminution of volume, increased pressure will increase the stability of the com- pound, and the flame will contain a larger proportion of steam, as well as have a higher temperature, than at ordinary pressures. The water formed when the flame was a jet of oxygen burning in hydrogen was found to be alkaline, and to contain ammonia. But the proportion of ammonia was much less than the proportion of nitric acid formed when the jet was hydrogen burning in oxygen ; a specimen titrated contained 0'004 per cent, of ammonia. Affects of (Pressure- on the Sodium Spectrum. In order to see what effect would be produced by incr pressure on the spectrum of other substances in "the 'flame, charged the hydrogen with sodium vapour by making it pass, befor entering the experimental cylinder, through a «mall iron cylinder, -• in the figure, containing metallic sodium, heated by a lamp. As the D lines of sodium are very easily expanded and self-reversed in flame at ordinary pressure, some- care was needed to discriminate the effects which were really to be ascribed to pressure. The gas was easily charged with sodium vapour, and "when burning in oxygen, not only the D lines, but the citron and green pairs, and sometimes blue pair (X 467), and the orange pair (X 616), were well seen ; bt we could not find that they were expanded by increase of pressure. A sudden change of pressure generally produced an expansion, but it did not last; the lines fined down again when the pressure was steady, whether that pressure was high or low. These experiments were continued up to a pressure of 40 atmospheres without any definite Effect on the width of the lines* which could be ascribed to •the pressure. It may be said that at the higher pressure the evaporation of the sodium would be slower, and so the proportion of sodium vapour to hydrogen be dimini&hed ; also, when the lines are diffuse at the 1891.] Influence of Pressure on the Spectra of Flames. 221 edges to begin with, it is extremely difficult to judge whether there is any expansion. At all events, we may say that there is no expansion produced by pressure at all comparable with that produced in a flame at ordinary pressure by increasing the quantity of sodium in the flame. We noticed, however, that the presence of sodium, which produces a feeble continuous spectrum in a flame at an ordinary pressure, seemed to increase the continuous spectrum of the flame under pressure, especially in the orange and green. Oxy-hydrogen Jet in Carbonic Acid Gas. For this experiment a two-branched tube (the upper one in the figure) was used. The jet of mixed oxygen and hydrogen was first lighted and introduced into the experimental cylinder while the latter was full of air and the stopcock s open. The air was then replaced by CO., entering by the tube c. The effect of this was at once to brighten the flame and change its colour from yellow to blue. Seen in the spectroscope, the change consisted in an increase of continuous spectrum, especially towards the more refrangible end. When the stopcock s was closed so that the pressure rose in the experimental cylinder, the flame increased in brightness, but there was no other change in the spectrum. It remained continuous with no bright or dark lines, or bands, except the D lines of sodium. It resembled an ordinary flame of CO. The jet would not burn in C02 unless there was some excess of oxygen, and even with an excess of oxygen we could not get it to continue to burn in CO2 at a pressura higher than 2 atmospheres. Ethylene in Oxygen. A jet of ethyl ene burning in oxygen gave, when the flame was small, the usual candle-flame spectrum, together with a band in the indigo (X 431) shading towards the violet ; but as the pressure was increased the continuous spectrum brightened and completely over- powered the bands, and at the same time the absorption spectrum of N02 appeared. We carried the pressure up to 33 atmospheres, and at that pressure the flame seemed to give nothing but a continuous 3ctrum, intersected by the absorption bands of NO2. In our tube, flame was viewed almost directly end on, and it is possible that if re had seen the flame sideways, we might have detected the hydro- irbon flame spectrum near the nozzle. At the high pressure much separated. We tried burning a mixture of ethylene and oxygen, le mixed jet burnt well in air and, when the supply of oxygen was ifficient, gave the hydrocai'bon flame spectrum. In the experi- ital tube in oxygen, the jet burnt well at the atmospheric pressure, •2-22 Profs. G. D. Liveing and J. Dewar. [Feb. 19, but we failed to get it to continue burning when the pressure was increased. The shaded band, commencing with a sharply-defined edge about \ 431, seems to be independent of the pressure, and has been before observed in a gas flame (Huggins, 'Roy. Soc. Proc.,' vol. 30, p. 580). In fact, the only effect of pressure in this, as in the former cases, seemed to be the increase of the continuous spectrum. Cyanogen and Oxygen. As we could not obtain cyanogen at such pressures as we had used in the case of the other gases, we were obliged to content ourselves with exploding mixtures of cyanogen and oxygen in an iron bottle, fitted with a quartz stopper like that of the experimental tube above described. The bottle, having been exhausted by an air-pump, was filled with the mixture of gases, and exploded by an electric spark. With less than 3 vols. of oxygen to 1 vol. of cyanogen, there was always a considerable deposit of carbon, which covered the quartz and impeded vision ; but, with 3 vols. of oxygen to 1 of cyanogen, the carbon was all burnt. Notwithstanding the brilliant banded spectrum of a flame of cyanogen in oxygen at ordinary pressure, nothing but a continuous spectrum could be seen in the flash of the exploded gases, except the ubiquitous D lines of sodium. The continuous spectrum was bright. Photographs showed a continuous spectrum with lines of iron, calcium, potassium, and sodium, but no cyanogen or carbon bands, or carbon lines. When a little hydrogen was added to the mixture of gases, no trace of the hydrogen red or green line could be detected in the spectrum of the exploding gas. In every case, the prominent feature of the light emitted by flames at high pressure appears to be a strong continuous spectrum. There is not the slightest indication that this continuous spectrum is produced by the widening of the lines, or obliteration of the equalities, of the discontinuous spectra produced by the same at lower pressures. On the contrary, it seems to be developed inde- pendently. This is, on the whole, quite in accordance with what would be expected, considering that under pressure the molecules of the gases have much less freedom, encounters amongst them are much more frequent, and they have much less chance of vibrating independently, and of taking up exclusively, or chiefly, the funda- mental rates of vibration which are natural to them when free. Their condition, during a large part of any given time, approximates to that of the molecules of a liquid, and their spectra approximate to that of a liquid to at least a like extent. On the other hand, the higher temperature which, in many flames, attends an increased pressure ought to give some intensity to the special radiation which the molecules emit during their time of free motion ; and this we have 1891.] Influence of Pressure on the Spectra of Flames. 223 noticed to occur in the principal sections of the discontinuous spectrum of the oxy-hydrogen flame. Whether the continuous spectrum is due to the mutual action of the molecules of the com- pressed gases may perhaps be best determined by some photometric measures of the rate at which the brilliance increases with the pressure. Frankland ('Exp. Researches,' pp. 892 et seq.) has made some such measures, but not safficient to solve the question. We have made an attempt to measure, not the total intensity of the light, but that of rays of definite refrangibility. Photometry of Oxy-Hydrogen Flame under Pressure. The apparatus used for these measures was a spectro-photometer of the pattern employed by Crova (' Annales de Chimie,' ser. 5, vol. 29, p. 556). In this, the rays of one of the sources of light to be com- pared are passed through two Nicol's prisms, and then reflected into one half of the slit of the spectroscope, while the light from the other source passes directly into the other half of the slit. By turning one of the Nicol prisms, the light from the first source can be reduced at pleasure, and any small section of the spectrum can be separately observed by cutting off the rest by means of a shutter in the eye-piece. We found it by no means easy to get good concordant observations. A much larger vessel was used than for the earlier experiments, one which contained several litres, and so we may presume a more uniform pressure was maintained within it. The results of the best series of observations on the photometric intensity of the jet of oxygen burning in hydrogen are given in the following table. The comparison light was a petroleum lamp. 1. 2. 3. 4. 15 Ibs. 3° 274 30 x 32 = 270 35 7 1485 30 x 72 = 1470 55 11 3641 30 x II2 = 3G30 75 . 14 5853 26 x 152 = 5850 95 19 10600 29 x 192 = 10469 The first column gives the pressure of the gas, the second the lean of four to six observations of the angular deviation of the Nicol's nsms from the position of complete extinction, for each pressure. The third column gives the squares of the sines of the angles in the ind column multiplied by 100,000. It will be seen from the last column that the numbers in the third jlumn, which should be proportional to the photometric intensities '2'1 1 Influence of Pressure on the Spectra of Flames. [Feb. 19, at the respective pressures, are approximately proportional to the squares of the pressures. This may be taken to indicate that the brightness of the continuous spectrum depends mainly on the mutual action of the molecules of gas. A series of similar observations on hydrogen burning in oxygen gave somewhat different results, tabulated below : — 1. 2. 3. 15 Ibs. 6° 1093 35 13 5060 55 18 9549 75 22 14033 95 28 17861 The flame was brighter than thafc of oxygen burning in hydrogen at ordinary pressure, but the rate of increase with increased pressure was not so rapid as in the former case. It seems as if the continuous spectrum were made up of two parts, one varying as the square of the pressure, and another according to some other law. The flame is evidently not the same in the two cases. The products of combustion derived from the small quantity of air are different, and also the hydrogen jet always showed the presence of sodinm, sometimes calcium. The appearance of the flame was also different; the hydro- gen jet being faintly visible and yellowish in the elongated part, whereas the light from the oxygen jet was concentrated near the base, the point being invisible. The measures of which the means are tabulated above were also less concordant than the corresponding measures for the oxygen jet. We were unable to carry our measures beyond a pressure of 95 Ibs., because at higher pressures a cloud was formed in the apparatus which prevented our seeing the flar directly. We hope to prosecute these measures with flames of oth< gases, and, if possible, at higher pressures. The conclusions to which our experiments have led seem incoi sistent with those which have been drawn from Pliicker and Hittoi well-known observations on the widening of the hydrogen lines in vacuous tubes with a residue of hydrogen when that residue increases. That the widening of the lines in a Pliicker's tube results from increasing the density of the residue of hydrogen in the tube cannot be gainsaid, but we are wholly ignorant of the mechanism by which the gas is lighted up by the electric discharge. It is sometimes assumed, but without any sufficient reason, that the energy of the electric current is first converted into heat, and then in turn into 1891.] Focometry of Lenses and Lens-Combinations. 225 radiation ; but the electric energy may equally well be directly con- verted into the motion of radiation. As a fact, we nave never yet been able to obtain either the emission or the absorption spectrum of hydrogen without the aid of an electric current, so that, in reasoning on this spectrum, we are much more in a region of speculation than when treating of flames. Whether the hydrogen lines, bright or dark, in the solar spectr,un» are produced directly by the high temperature of the sun, may even be called in question. And though we may admit that the density of the hydrogen in the sun's atmo- sphere, outside the photosphere, is but slight, it does not follow that the total pressure of all the gases forming that atmosphere is so very .small as Messrs. Frankland and Lockyer (' Boy. Soc. Proc.,' vol. 17, p. 288) have, from the width of the lines, concluded it to be. After all, it is not so easy to connect the temperature, even of a flame, with its radiation, for it is only when the condition of a gas is steady that we can assume that there is a definite relation between the motion of agitation, on which temperature depends, and the vibratory motions, on which radiation depends. In speculating on such questions, chemical, as well as electrical, changes must not be lost sight of, although the latter may be more -directly concerned in radiation. Experiments which we have commenced upon the arc in an atmosphere of compressed gas tend to the same conclusion. It does not appear that the metallic lines in the arc are sensibly affected by a steady pressure up to 15 atmospheres. The details of these observa- tions, which are complicated by the variation of resistance with ige of pressure, we -defer until the experiments are finished. [I. " On the Focometry o'f Lenses and Lens-Combinations, and on a new Focometer." By SILVANUS P. THOMPSON, D.Sc., B.A., Professor of Physics in the City and Guilds Technical College, Fiiisbury. Communicated by Professor G. CAREY FOSTER, B.A., B.Sc., F.R.S. Received February 4, 1891. (Abstract.) Few of the accepted methods of focometry take into account the stance between the two principal points (or Gauss points) of a lens, afford the means of measuring this distance, as well as the true. il length, and some of them are open to the objection that they jessitate troublesome double adjustments. Of these methods the ithor gives a brief categorical review. He has devised a method in which there are no double adjustments, measurements of the size of optical images, no assumptions as to 226 Focometry of Lenses and Lens- Combinations. [Feb. 10, the approximate positions or distance apart of the two principal points, but in which both the true focal length and the width between the principal points are determined by direct measurements of lengths. The principle of the method is as follows : — Beyond the principal focal points on each side of the lens, at distances equal to the true focal length, are two points which are conjugate to one another and symmetrically situated at twice the true focal length from the two principal points. These may be called the symmetric points : and the planes drawn through them orthogonally to the principal axis may be called the symmetric planes. They are planes of unit magnification, and possess the known geometric property that the ordinate in one of these planes of the point of intersection of any incident ray is equal in magnitude, but opposite in sign, to the ordin- ate in the other plane of the point of intersection of the emergent ray. Let AB be the lens or combination of lenses, F,F2 the principal foci, H^fclj the principal points, SjSj the symmetric points. Then the true focal length is F2H2 = FjH, = F^ = F2S2. 5i\L f Suppose a parallel beam to be sent from left to right through AB ; an image will be formed at Fj. Let the light then be sent from right to left forming an image at F2. Suitable transparent micrometers are placed to receive these images and to ascertain their precise position in space. A graduated bench is provided upon which the lens and the micrometers are placed so as to read off the distances between these points. A gearing is provided, namely, a right- and left-handed screw, by means of which, when the two micrometeru have been placed at FT and F2 and clamped to the screw, they can be moved by the experimenter at exactly equal rates outwards, so that when one arrives at St the other arrives at S3. This is known by observing in one micrometer the exact image of the other of equal size. The distance through which the micrometers have each been displaced is equal to the true focal length ; and the distance H , H., between the two principal points is found by reckoning backwards from Fj and F2 distances equal to the focal length so found. The positions of the two principal points can then be marked upon the outside of the tube of the objective. These principles are embodied in an instrument described in the 1891.] The Numerical Registration of Colour. 227 paper, and called a focometer. It has been constructed to the author's designs by Messrs. Nalder Brothers, to whom sundry of the mechani- cal details are due. The paper also describes the results obtained with the focometer upon various lenses, some of them being microscope objectives, others camera lenses. The author finds in several of these lenses that the principal planes are crossed : the distance between the symmetric points being less than four times the focal length. In some other lenses which are achromatic in respect of bringing all rays to a com- mon principal focus, the positions of the principal planes are different for rays of different colours. In one lens, a microscope objective by Reichert, the principal planes are not only crossed but are actually at a greater distance apart than the two principal foci. The paper is accompanied by a sheet of full-size drawings showing the construc- tion of the instrument and its details. [V. " The Numerical Registration of Colour. Preliminary Note." By Captain W. DE W. ABNEY, C.B., R.E., D.C.L., F.R.S. Received February 6, 1891. The Committee of the Royal Society on Colour Vision having put ito my hands the determination of the colour of certain signal glasses, memorandum was drawn up on the method of the numerical regis- ition of colours and submitted to them. They considered that it lould be submitted to the Royal Society, and having slightly modified, it, it is presented as a preliminary note of a part of a paper which will be subsequently submitted by General Festing and myself as Part III of " Colour Photometry." It must be premised that a colour is determined when its hue, its purity, and its luminosity are known, the last constant being its comparison with the white light before its passage through a trans- parent coloured body, or with white light reflected from a white surface if it be an opaque coloured body such as a pigment. There has hitherto been a certain amount of difficulty on the part of normal-eyed persons in stating the exact hue of compound colours in terms of any standard ; in fact, I believe, except by the method given in the Second Part of " Colour Photometry " (' Phil. Trans.,' A, 1888), there has been no exact means indicated of reproducing a colour from measurements made. The method which will be described can take the place of the previous plan for certain purposes, more particularly when it is the impression on the eye which has to be considered. Any colour can be reproduced from the registration numbers with the greatest exactness. To pei-sons who are totally colour-blind to one sensation, viz., the Capt. W. de W. Abney. [Feb. in. green or the red, the matching of a compound colour with a simple one in the spectrum should possess no difficulties. Taking the trichro- matic theory of three sensations for the normal-eyed person, it is evident that only the following classes of sensations are possible in the normal-eyed, the green colour-blind, and the red colour-blind : — Normal eye. Red Green Violet Mixtures of red and green Mixtures of red and violet Mixtures of green and violet Mixtures of red, gieen, and violet Green colour-blind. Red — Green. Violet. . Violet. Red colour-blind. Mixtures of and violet. red — Mixtures of green and violet. If we take as a type of colour-blindness the green colour-blind person, we see that every colour in the spectrum must be either red, violet, or these colours mixed with more or less white light, since these two sensations when e-xrited in certain proportions give the sensation of white. At one place, which is commonly called th« neutral point, these proportions are such that there is the impression of white light ; it follows that, between this neutral point and each end of the spectrum, the rays are mixtures of violet and white or red and white, the dilution of the colours varying from no white to all whit As every compound colour must be a mixture of the same two colours ii certain proportions, it follows that the green colour-blind person match every compound colour with some one ray of the spectrum, and that every colour must to him be either red or violet, diluted with different proportions of white light. In the same way, a person who is colour-blind to the red match any colour with a single spectrum colour, and he will see it as green or violet diluted with more or less white light. This can be readily understood, but it is not quite so plain how any colour sensa- tion felt by the normal eye can be referred to the spectrum. The following is an outline of the reasoning which leads up to method of registration employed : — If we take three rays in the spectrum — one in the red between and the red lithium line, which we will call R, another in the green between F and b, which we will call G, and a third in the violet neur G, but on the H side of it, and which we may call V — then, by vary- ing their intensities (which is equivalent to varying the luminosities) 1891.] The Numerical Registration of Colour. and mixing them, we can give the same impression to the eye that any compound colour gives, and that of any intermediate simple spectrum colour but very slightly diluted with white light. With these same three colours, but in different proportions, we can also give the impression of white light to the eye. The intermediate spectrum colours between the green and the violet rays selected, when slightly diluted, are imitated by mixing these rays together in different proportions, and similarly those lying between the red and the green by mixing together these rays in different proportions — and there is some ray present in the spectrum which, when very slightly diluted with white light, has the same colorific effect on the eye as the mixtures of the pairs V and G and G and R in any pro- portions whatever. Let the luminosities of the rays R, G, and V, which give the im- pression of white light, be a, &, and c units respectively, and p, g, and r those which give that of the colour which has to be registered and reproduced. We then get the following equations — where W is white, w its luminosity, Z the colour, and z its luminosity — wW ................ (i); pR + qG + rV =zZ .................. (ii). Then evidently — (a + J + e) = w, and Let p = ata, q = fib, r = ntity of white light, as the above mixture of Fand G — let us call it X and its luminosity x \x being evidently equal to (ft — «)& + (bviously, one which would involve the investigation of the excita- 3ry changes occurring in the fibres of the spinal cord when the jrtex cerebri is stimulated. We must at once assume that the motor }ide of the central nervous system is practically divisible into three ;ments. (1.) Cortical centres. (2.) Efferent (pyramidal tract) Ibres, leading down through the internal capsule, corona radiata, and spinal cord. (3.) Bulbo-spinal centres contained in the medulla and the spinal cord, and forming the well-known nuclei of the cranial and ilso of the spinal motor nerves. It had already been determined, both by direct observation and by ie graphic method (1), that certain areas of the cortex were con- xected with definite movements of various parts of the body, and (2) it while the complete discharge of tho cortical apparatus was 236 Mr. F. Gotch and Prof. Victor Horeley. [Feb. 2( followed by a very de6nite and characteristic series of contractions of the muscles in special relation with the particular point excited, tin- effectual removal of the cortical central mechanism and subsequent rvriiiition of the white fibres passing down through the internal cap- sule, «fec., led to the production of only a portion of the effect pre- viously obtained from the uninjured brain. This method of observation in no wise showed what processes were actually occurring in the spinal and other nerve fibres, and although the ablation of the cortical centre to a certain degree suggested the extent to wli ;ch the cortex acted, nevertheless it did not afford an exact demon- tration of the same. Moreover, the data which the graphic method furnished were precluded, through their being muscu- lar records, from determining what share, if any, the lower bulbo- spinal central nerve cells took, either in the production of the charac- teristic sequence of contractions or in the modification, whether in quality or in force, of the descending nerve impulses during their transit. It seemed to us that the only way to approach this subject would be to get, as it were, between the cortex and the bnlbo-spinal system of centres. This would be accomplished if some means were devised of ascertaining the character of the excitatory, processes occurring in the spinal fibres of the pyramidal tract when, upon exci- tation of the cortex, nervous impulses were discharged from cortical cells, and travelled down the cord. The question as to the extent to which it is possible to obtain physical evidence of the actual presence in nerve fibres of excitatory processes, and thus to arrive at reliable data for the comparison of their amounts, is one which up to the present has been answered only indi- rectly, and that in two ways : first, by the extension of Helmholtz's classical experiment of determining the rate of transmission, and, secondly, by observing those variations in the electrical state of nei fibres which Du Bois-Reyniond discovered to be an invariable comitant of the excitatory state. As will subsequently be shown the historical retrospect, it is well known, through the researches Dn fiois-Reymond and others, that the fibres of the spinal cord, j as nerve fibies in the peripheral trunks, are characterised by showing, when uuexcited, an electrical difference between their longitudinal surface and cross sections ; and, furthermore, that when excited, a well-marked diminution of this resisting electrical state is produced in the fibres of the cord, as in those of nerve trunks. Now, since such excitatory variations in the electrical state are presumably paral- lel in time and amoant with the presence in the nerve of the series of unknown processes, termed excitatory, which a series of stimuli evokes, it was reasonable to presume that, if the cortex were dis- charging a series of nerve-impulses at a certain rate down the pyramidal tract, there wonld be a series of parallel changes in the 1891.] On the Mammalian Nervous System. 237 e'ectrical condition of the fibres in the cord tract, and that, with a suitable apparatus for responding to such changes, these might be both ascertained and recorded. The accomplishment of a further purpose, viz., the localisation of both paths and centres by ascertaining the excitatory electrical effects in relation with them, was one of the main objects we had in view. In carrying it out, we found it was unnecessary to employ the electrometer, and, in fact, that it was ad- vantageous to use the galvanometer, the record of which would be more easily and more accurately noted, since its graduation admits of far higher magnification. Moreover, with this instrument it was possible, by employing a series of stimuli, of known number and duration, to obtain quantitative results of definite comparative value, as will be shown further on ; and thus, to compare both the size of different central paths and the amount of nervous energy discharged along the same path from different sources. The plan upon which the full paper is framed is, first, to give an historical retrospect of the work of authors who have opened up the study of electrical changes in the central and peripheral nervous system ; second, to describe at length our mode of experimentation, rith special reference to the modifications which we have introduced, len to compare roughly the results we have obtained by our present lethod with those which had been previously ascertained by the iphic method, and so introduce the description of the facts which have discovered, elucidating the physiology of the spinal cord, both its relation to the higher centres and to the peripheral nerves. 2. Experimental Procedure. The observations were in all cases made on etherised animals (cat id monkey), with due regard to the special influence of the anaes- letic. The operative procedure was so designed as to provide for litable exposure of a particular region of the nervous system for excitation, and of another part in which the electromotive changes evoked by the stimulation may be observed. The relative parts were follows : — Part eiposed for Excitation.. Part exposed for Observation. Brain (cortex and corona radiata). . - . and spinal cord. Do. do. do. .... and mixed nerve. Spinal cord and spinal cord. Do and mixed nerve. Mixed nerve and spinal cord. Spinal roots do. do. Posterior roots and mixed nerve. The excitation was either electrical, chemical (i.e., with absinthe id strychnine), or mechanical. In the former instance the duration 238 Mr. F. Gotcb. and Prof. Victor Horsley. [Feb. 2t and intensity were specially determined. The records were made by a Thomson high -resistance reflecting galvanometer, and a Lippmanii's mercurial capillary electrometer. The tissue, whether nerve or spinal cord, was so arranged for obser- vation as to be always suspended in the air, one end remaining in connexion with the animal ; consequently any error due to cnri-ent deviations from the rest of the body could only have a slight and unipolar effect. 3. Resting Electrical Difference between the Cut Surface of the Tissue and its Uninjured Longitudinal Surface. The average amounts of this difference in the tissues observed were as follows : — Cat. Monkey. Nerve (69 cases), 0-01 Daniell ... (12 cases), 0'005 Daniell. Root (5 cases), 0'025 „ Cord (50 cases), 0-032 „ ... (9 cases), 0'022 We have observed that the cord difference is greater when that tissue is in connexion with the higher centres, and that it rises after excitation. An important fall of the difference is to be remarked in all three tissues as a direct result of systemic death. 4. Electrical Changes in the Spinal Cord evoked by Excitation of Cortex Cerebri and Corona Radiata. We further discuss in our full paper the following points additic to those described in our previous communication, and which hai resulted from the observation of the above changes: — (a.) Localisation of cortical areas of representation in relation the various regions of the cord. (i.) Bilaterality of representation in the central nervous system, as evidenced by the electrical changes in the two halves of the spinal cord, consequent upon excitation of the brain or cord. 5. Electrical Changes in the Spinal Cord when Evoked by Direct Excita- tion of its Fibres, after Severance from the Encephalon. We have by employment of this method ascertained the proportion- ate existence of direct channels in the various columns of the spinal cord, our design embracing the quantitative comparison of the elec- trical changes (and so indirectly of the nerve impulses) which are transmitted as a result of minimal excitation of the fibres. To further control our observations on these points, we have also determined the 1891.] On the Mammalian Nervous System. 239 extent of interruption in any given channel by intervening sections of the same. As an extension of this subject, we have investigated the concurrent spread of nervous impulses to collateral paths, and probably to centres, when this further condition is introduced by increase in the stimulus. The above results have been obtained in the case of both ascending and descending impulses. Among other general conclusions from this division of our research are the following : — (1.) High degree of unilaterality of representation in the spinal cord. (2.) Spread of impulses from one posterior column to another and from one posterior column to its neighbouring lateral column through centres. 6. The Relation of the Paths and of the Bulbo-Spinal Centres in the Spinal Cord to the Peripheral Nerves and their Roots. We have investigated this important relationship in the following modes : — (I.) The Electrical Changes in the Spinal Cord evoked by Excitation of a Mixed Nerve or its Roots. — The chief conclusions which have been deduced from the results of these experiments, by means of minimal excitation and the employment of the method of blocking by inter- vening sections, include the following : — (1.) Complete obstruction offered to centripetal impulses reaching the cord by the central end of the anterior root. (2.) Mode of conduction, direct and indirect, in the cord of centri- petal impulses passing up the posterior root. (3.) Localisation of the direct path of afferent impulses in the pos- terior column of the same side as that of the nerve or root excited. (4.) Localisation of the indirect path of afferent impulses in the posterior columns of the same and the opposite side and the lateral [•olumn of the same side as that of the nerve excited. (5.) Proportionate development of both systems of paths in the two sides of the cord. Expressed in percentages of the total transmission, this proportion as follows : — Posterior column of same side as the excited nerve.. . 60 p. c. Lateral column of same side as the excited nerve 20 „ Posterior column of opposite side to the excited nerve 15 ,. Lateral column of opposite side to the excited nerve . . 5 „ (II.) The Electrical Changes in a Mixed Nerve or its Roots evoked by 240 Presents. [Feb. Excitation of the Spinal Cord. — Whereas in the foregoing series (I) MV dealt only with ascending impulses, we proceeded to investigate the distribution of descending impulses by observing the above-named changes when the individual columns of the cord are excited by minimal and later with more intense stimuli, controlling our results by the method of intervening sections. We can summarise the effects observed as follows : — (1.) Marked quantitative diminution suffered by impulses, leaving the spinal cord by the anterior roots, whether originating in the cortex cerebri, corona radiata, or the lateral columns of the cord. (2.) Localisation of direct transmission of impulses in the posterior column and passing out into the posterior roots of the same side. (3.) Proportionate development of the direct and indirect paths in the individual columns of the cord, passing out into the mixed nerve of the one side. (4.) Effects observed in the posterior roots when the bulbo-spinal centres are excited either by strychnine or electrically (kinaesthesis). Finally, the chief general principles elucidated by this research may be stated as follows : — (1.) Unilateral character of the representation of function in the paths of the central nervous system. (2.) The physiological characteristics of the regions of a nerve centre : — (a.) The kinsesthetic activity of the afferent region of the centre. (6.) The obstruction offered by the efferent region, including the field of conjunction, to the transmission of impulses through the centre. Presents, February 26, 1891. Transactions. Baltimore : — Johns Hopkins University. Studies in Historical Political Science. Series 9. No. 1 — II. 8vo. Baltimore 1891 The Univenrit Cracow : — Academic des Sciences. Bulletin International. Comj liendus des Seances. 1891. No. 1. 8vo. Cracovie. The Acader Delft : — Ecole Polytechnique. Annales. Tome VI. Livr. 2. Leide 1890. The Dublin : — Royal Irish Academy. Transactions. Vol. XXK Part 14. 4to. Dublin 18i)l ; Proceedings. Ser. 3. Vol. I. No. 4. 8vo. Dublin 1891. The Academy. 1891.] Presents. 241 Ti-ansactious (Continued). Klausenburg : — Erdelyi Muzeum-Egylet. Ertesito. EVfolyam XV. 8vo. Kolozsvdrt 1890. The Museum. London : — Institution of Mechanical Engineers. Proceedings. 1890. No. 4. 8vo. London 1890. The Institution. Royal Meteorological Society. The Meteorological Record. Vol. X. No. 38. 8vo. London 1891. The Society. Royal Statistical Society. Journal. Vol. LIII. Part 4. 8vo. London 1890. The Society. St. Bartholomew's Hospital. Reports. Vol. XXVI. 8vo. London 1890. The Hospital. Society of Antiquaries. Archjeologia. Vol. LII. (Second Series. Vol. II.) 4to. London 1890. The Society. Mexico : — Sociedad Cientifica " Antonio Alzate." Memorias y Revista. Tomo IV. Num. 3-4. 8vo. Mexico 1890. The Society. Prague : — Kb'nigl. Bohmische Gesellschaft der Wissenschaften. Spisuv, &c. Cislo III— V. 8vo. v Praze 1890 ; Die Specu- lative Idee der Freiheit ; von J. H. Loewe. 8vo. Prag 1890. The Society. Rome : — Accademia Pontificia de' Nuovi Lincei. Atti. Anno XLIII. Sessione 4-6. 4to. Roma 1890. The Academy. I'll' Present*. Observations and Reports (continued). Mining Department for the Quarter ended 30th September, 1890. Folio. Melbourne. The Department. Public Library, Museums, and National Gallery of Victoria. Report of the Trustees for 1889. 8vo. Melbourne 1890. The Librarian. Monnt Hamilton : — Lick Observatory. Publications. Vol. I. 1887. 4to. Sacramento ; Reports on the Observations of the Total Eclipse of the Snu of January 1, 1889. 8vo. Sacramento. The Observatory. Sydney : — Australian Museum. Annual Report. 1890. Folio. Sydney. The Museum. Department of Mines. Annual Report. 1889. Folio. Sydney, Memoirs. Palaeontology. Nos. 3-4. 4to. Sydney 1890. The Department. Observatory. Meteorological Observations. January to August, 1890. 8vo. [Sydney] ; Results of Meteorological Observa- tions made in New South Wales during 1888. 8vo. Sydney 1890 ; Results of Rain, River, and Evaporation Observatioi made in New South Wales during 1889. 8vo. Sydney. The Observatory. Gaudry (A.) Le Dryopitheqne. 4to. Paris 1890. The Author. Hinde (G. J.) On a New Genus of Siliceous Sponges from the Lower Calcareous Grit of Yorkshire. 8vo. [London] 1890. j With one other Excerpt in 8vo. The Author. Jones (T. R.), F.R.S. On some Fossils from Central Africa. 8vc Hertford 1890 ; On some Bivalve Shells from the Karoo For tion, South Africa. 8vo. Hertford 1890. The Authc Kirkpatrick (J.) [Biographical Sketches of the Honorary Doctors Laws, presented to the Chancellor of the University of Edii burf. Carus-Wilson. Table I. Laboratory No. 0. V. U. 0,. v,. U,. th t»iv«'s the values of 0, deduced by measurement in each case; tl 7th gives ^pO ; the 8th gives wt, the area of the specimen in the shearing experiment; and the 9th column gives «, the intensity of shearing stress at rupture in the shearing experiment. It will be seen that in every case \pO is very nearly equal to *, i.e. the shearing stress at rupture in a tensile experiment is very nearly equal to the ultimate resistance to shearing in a pure shearing experi- ment. There are, however, two points to be considered before accepting the result of these experiments. The distribution of stress over the section of rupture in the tension experiment has been assumed constant, whereas it is not actually so. I find, by actual measurement, that the area of a plane section at 45° to the axis passing through the centre of the narrowed section bears to the area of a parallel plane passing through a point on the circum- ference, the ratio of 100 to 108, in a bar which has contracted 50 per cent., so that the shearing stress is rather greater at the centre, and hence the value of %p, given above, is tpo small by about 4 per cent. On the other hand, it has been pointed out to me by Professor Darwin that the distribution of stress in the shearing experiment is probably not uniform, being greater in the neighbourhood of the application of the stress. Experiments were made with two pieces of Lowmoor iron, cut off the same bar, and prepared as shearing specimens in the ordinary way, and tested in double shear, one with an area to be sheared of twice 1'039 square inch, and the other of twice 0'322 square inch. Tl result was as follows : Large section, shearing stress at rupture — (i) 18*7, (ii) 18'9 ; mean, 18'8 tons per square inch. Small sectioi stress at rupture — (i) 20'1, (ii) 20'6 ; mean 20'35. Giving the latt as 8*2 per cent, stronger than the former. The smaller the section tl more uniform will be the stress, and with the small section employe in the experiments quoted in Table III the stress is probably nearlj uniform. It would seem, then, that the possible errors due to the uneqnt distribution of stress in the tensile and shearing experiments woulc nearly balance one another, and that we may regard these results tending to confirm the theory that the greatest shearing stress is tl proper measure of the tendency to break.* * I have made experiments of a similar kind on cast iron. Great care was taken i casting to secure uniformity, by casting the bars upright and cutting off the spongy top ; they were cast with two heads which were turned to fit spherical seat ings. The shearing specimens were cut off bars from the same cast. The bars in tension were 10 inches long between the shoulders, and turned throughout their length. The Rupture of Steel l>y Longitudinal Stress. 253 It will now be necessary to enquire how far the appearance of the fracture of a steel bar affords evidence of its having broken by shearing. In a bar of circular section and uniform thickness throughout its length, every plane at 45° to the axis opposes an equal resistance to the tarigential stress caused by direct tension. Hence, there is no one plane or planes along which the bar would be more ready to break by shearing than along any other plane, provided that the material was of uniform strength throughout. If, however, the bar be gradually thinned at a certain point, this will no longer be the case ; it has been shown on p. 252, that the area of a plane at 45° to the axis passing through the centre of the narrowed section is less than the area of a plane passing through any other point in that section ; hence, there will be a surface formed by a complete cone of 45°, with apex at the centre of the narrowed section, which will oppose a less resistance to rupture by shearing than any other similar cone with apex at any other point. This cone is shown in section in fig. 6 at gof — aob. We should then expect to find rupture result in a fracture formed by a cone and crater, or, since there is nothing to determine along which part of the cone rupture will take place, we may expect to find the cone irregularly broken up, part on one end, and part on the other. This narrowing of girth at one point always accompanies the rupture of soft steel, and we invariably find such a cone and crater ; figs. 5 and 6, Plate 2, and 6 and 7, Plate 3, are good examples. [Note. — The rupture of cast iron in compression by shearing is of course well known. Fig. 2, Plate 2, shows the cone of shearing very well.] In flat bars of soft steel, this shearing action is still more marked. Here the surface of the least resistance is a plane at 45° to the axis and making 90° with the thin side of the bar ; it is evident that in a bar whose width is considerable compared with its thickness, and which has suffered considerable local contraction, this plane has the least area of all planes at 45° to the axis passing through any point in Tension . , Shearing Sectional area. r 1-047 \0-980 f 0-317 \0-327 Breaking stress. Tons per sq. inch. 10-40 10-40 6-14 4-78 Mean ditto. 10-40 5-46 The ratio of the former to the latter breaking stress being 1*9. The mean crushing stress was 41'5 tons per square inch ; diameter of specimen, 0-875 inch; length, 1'5 inch. In the ' Proceedings of the Institution of Civil Engineers,' vol. 90, p. 406, Messrs. Platt and Hay ward give results of shearing and tensile tests of cast iron, from which it appears that the ratio of the breaking stresses is 2'2. 2M The Rupture of Steel by Longitudinal Strest. FIG. 6. the contracted section. The result is, that in flat bars of soft steel the fracture is almost invariably as shown in figs. 4 and 5, Plate 3. Fig. 8, Plate 3, shows a flat bar of soft steel about to rupture by shearing along a plane _|_ the width of the — resulting no doubt from an accidental weakness in that direction. In the cases considered above, the steel has been of sufficient]] uniform quality to allow of the fracture taking place over a surfs of least resistance to shearing ; but, unless this condition be fulfill* the form of the fracture will be quite different. Figs. 7 and 8, Plate 2, show the fracture of a brass bar wher the plane of least resistance to shearing has been determined by punch mark (opposite the arrow) on the surface. Fig. 1, Plate 2, shot a steel bar where the apex of the cone is at the circnmferenc owing to the presence of a weak spot there. Every fracture is caused by the presence of a more or less wt defined weak spot; the stress is greatest at this spot, and the matei tends to tear in a plane J_ the axis passing through this spot, tearing action can be observed by drilling a small hole in a stt plate, and straining it. The plate pinches in near the hole, at gives way first on each side of the hole, and then tears right The experiment may be stopped before the tear has reached sides. When the steel is hard, this tearing continues in the plane Wilsaru Proc. Roy. Soc. Vol. 49 PI II. Cdrvue Wileon,. Proc. Roy. Soo. Vol. 49. PL Hi Photometric Observations of the Sun and Sky. 2 5- 5 which it commenced, i.e., perpendicular to the axis ; but when the steel is soft, the plane of the tear gradually tilts over and coincides with the surface of least resistance to shearing, i.e., becomes inclined at 45° to the axis. Now, at rupture, an originally soft bar is harder in the centre of the narrowed section than at the circumference, where the drawing out has been less ; hence, fracture commences at the centre perpen- dicular to the axis, and tears outwards until it reaches the softer material, when it will continue along a surface of least resistance to shearing, i.e., along a surface formed by the intersection of two cones. Hence, we find the fracture of a soft steel bar consisting of a crater with a more or less extended base ; see figs. 5 and 6, Plate 2, and 6 and 7, Plate 3. The harder the steel, at the outset, the broader will be the base of the crater, until, in very hard steels, there is only a rim or crown left round the edge ; and in the hardest steels all trace of the surface of least resistance to shearing disappears. [Note. — I have employed the term " hard " in the sense usually understood, i.e., where the " hardness " is measured by the value of the limit of elastic resistance.] "Photometric Observations of the Sun and Sky." By WILLIAM BRENNAND. Communicated by C. B. CLARKE, F.R.S. Received October 30,— Read December 11, 1890. 1. In the publications of the Society from 1859 to 1870, many com- munications by Sir Henry Eoscoe on this subject will be found. Of these, the most important bearing directly on my observations are — a. Bunsen and Roscoe, " On the Direct Measurement of the Chemical Action of Sunlight," in ' Phil. Trans.,' 1863, pp. 139-160. It is proved, inter alia, that equal shades are produced in photo- graphically sensitised paper by equal products of intensity of light X time of insolation. The preparation of a photographic paper which shall always possess the same degree of sensitiveness is carefully described. b. Roscoe, " On a Method of Meteorological Registration of the Chemical Action of Total Daylight," in « Phil. Trans.,' 1865, pp. 605- 681 [Bakerian Lecture]. The law is stated, inter alia, that light of intensity 50 acting for L second has the same effect as light of intensity 1 acting for 50 seconds. The mechanical arrangement for exposing the paper horizontal, or by the aid of a vertical drum, is explained. 256 Mr. W. Breimaml. Tables are added of half-hourly readings at Manchester, givi al actinic effects for different seasons of the year, &c. e. Roscoe and Baxendell, " On the Relative Chemical Intensities of direct Sunlight and diffuse Daylight at different Altitudes of the Sun." in ' Boy. Soc. Proc.,' vol. 15, 1866-67, pp. 20-24. By "total daylight" is meant the whole resultant action of the Sun and sky on paper exposed horizontally. By "diffuse daylight" is meant the same action when the Sun w stopped out. The "direct sunlight" was taken as the difference between I two ; it does not appear to have been observed directly. d. Roscoe, " On the Chemical Intensity of Total Daylight at Kew and Para," in ' Phil. Trans.,' 1867, pp. 555-570. e. Roscoe and Thorpe, "On the Relation between the Sun's Alti- tude and the Chemical Intensity of Total Daylight in a Cloud Sky," in ' Phil. Trans.', 1870, pp. 309-316. 2. My observations made at Dacca, in 1861-1866 (repeated Milverton, in Somersetshire, during the last year), were made in entire ignorance of the work of Sir H. Roscoe ; his results, therefore, so far as they agree with mine, afford an independent support to mj theory. My experiments have been directed largely to ascertaining the laws of the distribution of the actinic power in the sky, and thus the work of Sir H. Roscoe overlaps mine at particular points only. So also Roscoe has taken numerous observations of the sky more less clouded ; I take no observation except when the sky is clear, as find even a very slight haze to produce large differences in the measurements, and to bring into the numerical results complications that 1 have not at present attempted to deal with. 3. The method of measurement I adopted, is the darkening pro- duced in sensitised photographic paper ; for this effect I accept Roscoe's term of " the chemical action." My method of measurement differs from that of Roscoe in one important point : I use strips cut from one uniform sheet of ordinary photographic paper; all my measurements are so far relative, and I obtain the same numerical results (ratios) with any paper. I compare ultimately the effect of the Sun and of a candle on this same paper. Roscoe, by preparing special paper with definite proportions of nitrate of silver, Ac., depends on thus reproducing paper of exactly the same sensitiveness. I make each measurement numerically (as did Roscoe) by comparing the shade produced with some standard blackness. 4. I assume that in the burning of a stearine candle, the " chemical action " is proportional to the material consumed. I have taken as my unit (i) of measure of chemical action, the darkening produced at a distance of 1 inch from the wick of the candle, when 100 grains were consumed, which, in the candle I used in India, occupied about Photometric Observations of the Sun and Sky. 257 47. minutes. [I am here narrating the course I pursued in com- mencing these observations at Dacca ; I very soon discarded the candle, as I was able, by the aid of my table given below, to recover the unit of measurement by a Sun observation.] 5. I form a strip of photographic paper about f inch deep into a circular ring, placed inside a metal cylinder 3 inches in diameter. I place now my standard candle eccentrically, at a distance of I inch from the surface, and burn the 100 grains of stearine. I thus get a strip which is gradually coloured from the point nearest the centre (where the intensity is unit i) to the most remote point (where the intensity is j i). By calculating the distances of various points of the ring from the wick, the intensities corresponding to these dis- tances can be marked. I exhibit a small strip (of somewhat dif- ferent dimensions) so calibrated to show a ocale of intensities ; it has lost its original shade in consequence of fixing and toning. For actual purposes of measurement, a strip is used in its original unfixed state. 6. My earlier observations on the chemical action of the Sun and sky, were made in Bengal, with a " mica actinometer." In this, small squares of one sheet of sensitised paper were covered by 1, 2, 3, 4 .... thicknesses of mica cut from the same plate ; the sheet of paper then exposed to any light for a certain time gave me a series of chequered shades. To measure the effect of the Sun or of any portion of the sky, I noted the time necessary to darken the paper till it matched one of the squares in blackness. This instrument I have long since laid aside, as I have superseded it by better ; but by its aid in 1863 I was led to the attempt of measuring the chemical action of the Sun, in a clear sky, for each degree of the Sun's altitude, so as to form a table of constants, which would render a direct reference to the candle power unnecessary. 7. I have made an instrument (fig. 1) similar to one employed in India. The plane on which to expose the sensitised paper has iotions in altitude and azimuth ; a perpendicular style is placed at corner ; and, by shifting the plane until the style casts no shadow, ie plane can be adjusted at right angles to the Sun's rays, and the Sun's altitude can be read by a brass Gunter's quadrant. A slide lich covers the strip of sensitised paper, is made to move uniformly the plane, by means of a string passing over a pulley attached to a it in a column of water in a long cylinder (the one used in India was a rain-gauge) ; the float descends as the water is drawn off by a stopcock at the bottom of the cylinder. Lines can be drawn on a gauge pasted on the plane, beside the longitudinal slit, in which is t posed the sensitised paper, corresponding to the motion for 1, 2, 3, . . 20 seconds ; also a second gauge has been drawn for a larger p giving quicker motion. By simply moving the sensitised paper 254 Mr. W. Brennand. Fio. 1. laterally, a fresh portion of it is brought under the longitudinal and the observation can be immediately repeated, several times if desired. 8. By comparing the darkening produced in the paper in graphs 5 and 7, we easily show that we have to expose the paper fot times as long to produce the effect caused by diminishing the distance one half ; and that a light of intensity 4 acting for 1 second has the same effect as a light of intensity 1 acting for 4 seconds. This think might have been assumed ; Bnnsen and Roscoe, in their pa{ (1863) above cited, have, however, taken great pains to prove it. 9. My early experiments were designed to test the total effect the sky and Sun for photographic purposes. I have always experi- mented mainly by exposing the paper at right angles to the Sun's raj Roscoe on the other hand, exposes his paper in a horizontal plane. It will be seen below, that theoretic considerations have led me to another method of observation, which gives directly the measure of effect really desired, and does not require a clear heavens down to horizon on all sides (the Octant Actinometer). I give as a firsi example of my experiments the following table (A). The observatic Photometric Observations of the Sun and Ski/. 259 was taken on 21st December, 1868, on the roof of my house at Dacca, the sky being perfectly clear. The paper was exposed at right angles to the Sun, thus giving the effect of the Sun, together with the total effect (resolved on the plane at right angles to the Sun) of that portion of the visible sky within 90° of the Sun. Table A. Number of Length in Chemical Sun's Time of seconds per • inches of strip action altitude. observation. inch in motion for constant measured in of slide. shading, C. unit I. 11° 0' 7h 41m A.M. 11-0 I, . 1-.52 0-06 14 0 8 2 12-0 1-2 0-07 19 0 8 31 6-2 1-8 0-088 24 46 9 17 6-0 1-26 0-132 29 0 9 33 7-25 0 74 0-186 32 0 34 30 36 48 39 0 41 30 41 40 42 20 42 30 9 51 10 12 10 26 10 54 11 22 11 35 11 50 12 0 6-7 6-0 6-7 6-5 6-5 6-7 6-7 6-25 0-77 0-82 0-68 0-683 0-625 0-59 0-56 0-6 0-192 0-203 0-219 0-226 0-24 0 -2525 0-266 0-269 The number in the fifth column in this tahle. is the reciprocal of the nroduct o the two numbers in the third and fourth columns. hus, taking the last but one observation, 6-7 xO:56 = 3752, wm = °'266- The constant C of shading used as the standard of comparison was the tint produced in the same paper by the candle burning 47 minutes at 1 inch distance. Hence, the unit I here employed was 47 x 60 times i the unit in paragraph 4 above. .11 order to get a deeper shade of darkening in the first two obser- ions, when the Sun was low, a smaller stopcock was used than in succeeding observations. In each of these observations, the actual velocity of the slide was rved by an assistant with a watch. As explained in paragraph 7, is constant can be obtained more easily and exactly by a gauge, asted on the plane beside the slit, graduated for the stopcock 200 Mr. W. 10. The observations of Table (A), and numerous other similar observations, were taken with great care, the strips being read i In- same evening. The strips taken on separate days, were also compared •with each other; it was thus found that the numerical values for flu- chemical action were the same, with different paper, and with different candles. In England, I have, within the last two years, made similar observations to those at Dacca twenty-five years ago, and I submit three of the strips taken ; these have been fixed, and have conse- quently changed both in density and in colour, and are submit merely for explanation. The photographic sensitised paper, now pre- pared in England, keeps in the dark for months unchanged, and renders constant reference to the candle standard unnecessary. But by the aid of the table (B) which immediately follows, I could always in 1889 and 1890 recover the standard unit, by an observation of the Sun better than from the candle. 11. The chemical action of the Sun alone, is got in a dark room, arranging a vertical slit, so that the Sun's light falls exactly down the strip of paper, which I expose at right angles to his rays. To get the chemical action of the Sun and sky (i.e., the portion of the visible sky within 90° of the Sun) together, the exposure is completely in the open. The chemical action of the sky (i.e., the resultant actioi on the plane at right angles to the Sun of that portion of the visibl sky within 90° of the Sun) is got by an exposure in the open, a vertical stick having been arranged so that its shadow should just cover the exposed strip. As I took each of these three kinds of observations, giving mnnr rical results «, /3, 7 respectively, I was enabled from the simpl formula «-|- vation, the table itself being deduced from a very large number experiments. Sir H. Roscoe believes (Bakerian Lecture, 1865) that he brought the errors due to matching shades to within 2 per cent, correct ; and in graduating strips, the mean error was found by him not to exceed 1 per cent, of the measured intensity. I am not satisfied that my separate observations were always so closely accurate in the matching of shades. I employed my daughters independently, to match shades, and compared them with my own reading, and found that the readings sometimes differed more than 2 per cent. The photographic paper employed, varied somewhat in tint ; ths exposed to the candle being a little redder than that exposed to tt Sun and sky ; the same intensity in the darkening was sought every case. 1 suppose the difference in tint to have been due to heat of the candle. 16. The effect of the sky observed, was that due to the effect each elemental area of it multiplied by the sine of the angle between that elemental area and the normal to the plane of exposure, these infinitesimal effects being summed throughout the visible sky within 90° of the Sun. The chemical action of the sky (i.e., of the portion of it thus in- cluded) is seen to be half that of the Sun at 45° altitude ; and at altitudes of the Sun below 13°, where little more than half the sky is included in each observation, to be greater than that of the Sun. 17. I found the chemical action of the Sun, exactly the same fo the same altitude, at all seasons of the year and at all hours of day, as far as the experiments went at Dacca, and I find in Somer shire the same chemical action of the Sun at the same altitude as Dacca. I have not been able to get exactly the same candle I used at Dacca ; and a difference in the composition of the stear might possibly cause a small difference in the results, but I belie not one of much importance. [The observations in Table J below in the postscript show that difference is absolutely nil. — "27th October. 1890.] In the ' Phil. Trans.,' 1867, pp. 558—562, Roscoe says that for eqi altitudes of the Sun the chemical intensities are equal ; and he sumes " that the same " relation between the Sun's altitude and chei cal intensity holds good at Kew, Heidelberg, and Para." These result of Roscoe are confirmed by my observations ; he obtained them onlj by "averaging" numerous observations taken at Kew, and assumii that the effects of cloud, 3 _ Photometric Observation* of the Sun and Sky. 265 The readings of the chemical action are taken in terms of the unit of candle power, and were compared also with a graded Sun-strip, made at the same time from the same photographic paper by the water-motion actinometer, fig. 1. The observations given by the barrels at 170° and 10° are too low, doubtless owing to haze so near the horizon. No observation could be made with the barrel at 40°, because the Sun could not be kept out of it. The observation made by the barrel at 20" is (apart from com- parison with computed value) evidently erroneously large. I give the table as an early observation that shows well that there is a point of minimum sky intensity at 90° from the Sun. It also appears that if ia represent this intensity for the altitude » of the Sun (= 0'12), then the intensity of the sky at a point 6 from the Sun is given (roughly only according to this table) by the formula •ia cosec 6. This observation was made in the plane of symmetry : it turns out that the value, ia cosec 6, gives the intensity very accurately, in whatever plane 9 be measured from the Sun. I would note once more that my observations are largely compara- tive, and the results obtained are independent of the unit : it is not accessary to reduce the readings in this table to the one- second unit. 20. For any altitude of the Sun («), the chemical action of the sky a minimum at all points of a great circle 90° from the Sun, the jlane of which is the plane of minimum intensity (ia). And at this loment, the chemical action of the sky at any point distant 0 from Sun is given with great accuracy by the formula ia cosec 6. As the whole of the mathematical developments of this paper are junded on this law, I have been careful not only to verify it by inmerous observations both at Dacca and in Somersetshire, but also vary the form of the observations in every way I could devise. 21. Thus, the mitrailleuse has been placed in the plane of minimum itensity : in this case, all the barrels give accurately the same read- ier, except that those bai'rels 10° from the horizon read rather lower, I anticipated they would ; there must nearly always be some haze jar the horizon. Next, the mitrailleuse was placed at various angles with the plane symmetry, by turning it round the line joining one of its tubes nth the Sun. The observed chemical actions agree well with cosec 6. Next, by means of stops, I made the aperture of each irrel of a mitrailleuse to bo c sin 0, where 9 is the distance of the sis of the barrel from the Sun. This mitrailleuse being exposed, T 2 266 Mr. W. Brennand. the barrel with aperture c sin o being directed to the Sun, the circular darkened spots were found to be very accurately of uniform depth. Further, I calculated the times of exposure, for a (particular) mitrailleuse which ought, on the law i* cosec 0, to give a uniform tint. I exposed this mitrailleuse for these calculated times, first in the plane of symmetry, afterwards in a plane inclined to it at an angle of 52° ; the results agreed closely with my anticipation, and show to cosec 6 to be a very good approximation. 22. I have therefore made full use of the expression t'0 cosec 0 for the chemical action of the light of the sky in a circle distant 0 from the Sun (whose altitude is «). In carrying out integrations which include the portion of the sky actually occupied by the Sun, we do not, by employing this formula, introduce any infinite expression ; for each circular band of the sky of small breadth cd distant 0 from the Sun has an area 2ir sin 9 dO\ the chemical action of such band is therefore 2w u dO : so that the total chemical action thus attributed to the sky in the area occupied by the Sun's disk would be inappreciable. 23. Bunsen and Roscoe (' Phil. Trans.,' 1859, p. 891) determined chemically the action of the rays falling from a measui-ed portion of cloudless sky situated near the zenith, and then compared the visual luminosity of this same portion of zenith sky with that of the total heavens. They say " the amount of light chemically measured, Photometric Observations of the Sun and Sky. 267 which falls from the same surface of zenith sky, multiplied by the preceding ratio, must give the chemical action which the whole sky would produce on a horizontal unit of surface." I have below in one or two points only attempted to institute a numerical comparison between the results of Sir H. Boscoe and my own ; considering the great difference in our methods, I am not surprised that no good coincidence in the results can be established. DIAGRAM 1. 24. Having given ia the chemical action in the circle of minimum intensity, to calculate the total chemical action of the sky on a plane sxposed at right angles to the Sun. (N.B. — ia is a constant for this calculation, but it varies with « the Ititude of the sun). Let the figure (Dia. 1) represent a projection on the plane of sym- letry, S being the Sun, Z the zenith, HRYH' the horizon, AYX the lane of minimum intensity, SH = » the Sun's altitude. Let 9 be the angular distance from the Sun of the elementary zone Mr. W. Brennan-1. QR, and 0 the angular distance of an element in the zone QR from SQ. Denote by I, the chemical action exerted by a circular area x of the sphere, on the plane at right angles to the Sun. The area of an element will be rf0 dO sin 0, the intensity of the chemical action will be i« cosec 0. The angle between the normal to the element considered and that to the plane AYX is 0. . ' . d . I, = d0 d$ sin 0 x ta cosec 0 x cos 0 d . de . COB 0 = 2jn'«sin0. o Or, for the whole hemisphere, of which the Sun is the pole, from which, to get our desired result, we have to subtract the chemical action I, of the gore XYH. nRSH p— cos 0.d0.d = 2ia RSH cos 0 . dO. -RSH - a (cos RSH = tan SH cot SR = tan * cot 0). .•.I0 = 2ia cos"1 (tan * cot 0) cos 0 dO J a. w = 2r. [Lim T (cos'i (tan « cot 0) sin 0} - [* , ^""^ "I L • Jav/(l-sec2«cos2(?)J _ 2. Tw-_ f1 tan a. . dO "| " aL^~| v/(l-sec2«cos2e)J' Whence, subtracting this from equation (Q), This expression cannot be integrated in finite terms, but, by using : formula of reduction in series, it gives which is the formula I have used in numerical computations. IH~^ is the numerical value in the column headed "Sky alone" in Photometric Observations of the Sun and Sky. 2(39 "able B, which is thus brought into direct verification with ?'a, observed by the mitrailleuse. An example of the actual calculation of ia. is added in Appendix B, not for publication. 25. The values for Iu — IG for different altitudes of the Sun in Table B are much the most trustworthy observations, and are the leans obtained from a very large number of observations. I have, therefore, by the formula obtained in the last paragraph (24), in- versely calculated the value of ia. for every 5° within the limits 5° to 40°, and placed them in Table D. Table D. ia calculated from Table B Sun's altitude. (column headed " Sky alone"). 5° 0 -00329 10 0 -00681 15 0 -00928 20 0 -01073 25 0 -01144 30 0 -01188 35 0 -01205 40 0 -01218 45 0 -01213 50 0 '01209 55 0 -01204 60 0 -01200 65 0 -01195 26. Theorem. — On the resolution of the chemical action of the sky in a direction perpendicular to any plane. The figure (Dia. 2) is supposed an orthographic projection of the /isible hemisphere on the plane of the horizon ; S being the Sun, Z the zenith, HSZM the projection of the plane of symmetry, M'MI that )f the plane of minimum intensity, and M'SI that of the plane through at right angles to each of the other planes (which I call the plane )f the Sun's altitude). These three planes, when produced, divide le sphere into eight quadrantal surfaces, of which SMI is one. In le quadrantal triangle SMI, S, M, I are the poles of the opposite sides. Let the polar coordinates of P (an element of the surface) be 'SZ = 0 and SP = 0. Then, as before, the element will have an area dO. sin 0 = ia. df}>. dO. Let the planes OSM, OSI, and OIM (O being the centre of the ^misphere) be taken as coordinate planes ; OS, OM, 01, the three axes 270 Mr. W. Brennand. DlAOKAM 2. of coordinates ; and suppose through P the three quadrants to be drawn from S, M, I, to the opposite sides, meeting them in «, w, » respectively. Then the normal chemical action i* tZ0. do may be resolved in three directions parallel to SO, MO, 10 ; and the three components in these directions will be respectively ia. drfr dd sin Px, ta <70 dd sin Pm, t« eZ0 do sin P*. Call these respectively rf2U, tPV, d?W. We have nncl hence sin Pm = sin 0 cos 0, sin Pt = sin 0 sin 0, U = i* II f the gore HYX ; which will be found to be no difference at all ; as the values of the chemical action of each element in the subtracted )re are equal to those for a corresponding element in the added )re, with the same sign and angles of resolution on the horizontal slane. Hence we must have — (Qz) = (Q,) = 2ia (IT sina+2 cos a) (Y). Ls this is a result of the first importance, I submit at the end of this >aper in an Appendix, not for publication, the work by which I first rrived at the equation (Y) by laborious transformation of the elliptic integrals, which are reduced finally so that two terms, each irre- lucible by integration in algebraic form, destroy each other. 30. The results thus arrived at by employing the law of the jsecant are so neat that a suspicion may arise that the law may lave been assumed as one lending itself to mathematic manipu- ations. I may be permitted, therefore, to state, that the law was arrived it, more than twenty-two years ago, by experiment simply, and the ibject soon after laid aside. The present mathematic investigations only recommenced within the last two years, in order to in- titute a comparison between my old Dacca observations and those Sir H. Roscoe. 31. In 'Phil. Trans.,' 1870, p. 314, Sir H. Roscoe gives a table showing the total chemical action of diffuse daylight (i.e., of the ie sky, the Sun being stopped off) on horizontally exposed paper. These observations were taken in Portugal, with a perfectly clear sky, and I therefore select them for comparison with the foregoing theory and observed values of constants. T 3 •21-2 Mr. \V. JJn.-niiaiul. Columns 1 and 2 arc copied from lloscoc, I.e. ; column 2 gives my Qz = 2Jo (ir sin a, + 2 cos «). In column 3 I give /a, calculated from this equation. In column 4 I place the values of ia obtained from table B, the " sky alone " column, by the aid of the formula at the end of Art. 24. In the 5th column the values in column 4 are brought up by pro- portion for comparison with those in column 3, taking the observa- tion at altitude 42° 13' as the best ; i.e., increasing all the numbers in the ratio of 121 to 160. Table E. 1. 2. 3. 4. 5. Sun's altitude. Diffuse daylight. ia calculated from 2. i'0 calculated from Table B. Values in Column 4 brought up. 9° 61' 0-038 0-0078 0-0068 0-0090 19 41 0-062 0-0105 0 -0107 0 -0141 31 14 o-ioo 0-0150 0-0118 0-0156 42 13 0-115 0-0160 0-0121 0-0160 53 9 0-126 0-0)70 0-0121 0-0160 61 8 0-132 0-0177 0-0120 0 -0159 64 14 0-138 0-0187 0-0120 0 -0159 The discrepancies do uot appear at first sight great between the results of Sir H. Roscoe and my own. But his observations would show the maximum value of ia attained when the Sun was at or near the zenith, mine that this maximum occurs when the -Sun is about 45° OP 50° altitude. It is true that in the Dacca Table B, the actual observations ext only to 45° or thereabout, and that the values for altitudes of tl Sun above 45° are only filled in hypothetically ; but my established observations at Dacca, for altitudes of the Sun from 30° to 45°, show directly that at altitudes of the Sun of 45° or 50° value of ia would reach a maximum. In my Dacca observations, each additional 5° to the Sun's altitude brings into effect an additional 5° gore of the sky. It is therefore clear (apart from the law ig = ia cosec 6 and the integrations con- sequent thereon) that ia will have a maximum value when «, the Sun's altitude, is about 50° or 60°. I am not surprised that so considerable a discrepancy results from a comparison of the observations. In a single series of observations, the incidental errors of reading, &c., would introduce into the small numbers given in column 3 sufficient differences to alter entirely the law indicated for ia. Photometric Observations of the Sun and Sky. 273 32. Since in table E the value of ia for « = 42° 1 3' is found from Roscoe's observations to be 0 016, from mine to be 0'012, it follows that Roscoe's unit of chemical action is yf of my Dacca candle unit. This is merely a first attempt to correlate these units. 33. The resultant chemical action of the sky on a horizontally exposed piece of paper, the Sun's altitude being «, is found = (2w sin a. + 4 cos «)t'a. This vanishes when 2-n- sin a. + 4 cos « = 0, 2 t.e., when tan « = — _, 77- * = -32° 29'. This gives an absolute value for twilight, supposing daylight to ease when the diffused daylight of Roscoe entirely vanishes. The extreme limit at which twilight has been certainly observed is when, the Sun was 24° below the horizon ; at which time the formula ta(27r sin a, + 4 cos x) would show the chemical action of diffuse day- light to be only -^ part of wrhat it was just after sunset. In other words, the formula «a(27T sin » +4 cos «) . gives a very good agreement with the observed duration of twilight, supposing, that is, the illumination and the chemical action to follow uch the same laws in this extreme case. 34. Taking up the expressions for U, V, W at the end of Art. 26, I integrate them for the octant of the sphere contained by the three coordinate planes, viz., the plane of symmetry, the plane of minimum intensity, and the plane of the Sun's altitude ; i.e., I take 0 and 6 each from 0 to \TT • which gives . [V] = [W]'= suggested the construction of the octant actinometer, which requires only one-fourth of the visible sky 'to be clear for observation, and gives the value of ia. directly, requiring no calculations of re- duction. 135. The octant actinometer (fig. 3) consists of three quadrantal ancs, MOS, MOI, and IOS, joined at their edges so as to form a hollow trihedral, and mounted so that one of the edges, OS, can be brought to int to the Sun, and the plane MOI will then coincide with the >ne of minimum intensity. The instrument has another adjustment 274 Mr. \V. Brennand. Fio. 3. by which it can tarn round OS as an axis, and if one of the planes MOS, IOS be brought to coincide with the plane of symmetry, tl other will coincide with the plane of the Sun's altitude. I take a small square (diagram 3) of sensitised paper and cut along CO ; then, slipping the part COB under AOC, so that B coil DlAGKAM 3. Photometric Observations of the Sun and Ski/. 275 cides with C, it forms a rectangular trihedral of sensitised paper. This is placed in a small exposure trihedral of cardboard, and covered by a thin metallic trihedral in the trihedral angle of the octant. (I make several of these trihedrals of sensitised paper, so as " in the field " to take quickly a series of observations.) The trihedral of sensitised paper is, of course, carefully covered up till the instrument is in adjustment; if then exposed to the action of the sky for (say) 30 seconds, the readings on the quadrantal planes MOS and IOS will be each 30 ia, and that on the quadrantal plane MO I will be 30 . ^TT . '9 seconds. I therefore used this snnstrip for the observations in he preceding table. I infer that, at least at 12h 8m, the sky on the 1th October was really clear. Some of the values in this table are igher than those obtained by computation for ia. Mr. \V. Table H. — Octant Observations at Milverton, Somerset, 1890. Time. Sun's altitude. v-[W], [U]. 10th Oct., llh 15ro 31° 0' 0 -0237 0 'C293 12 19 81 45 0 -0225 0 -0 '70 2 11 25 10 0'0130 0-0171 llth Oct 12 10 31 15 0'0226 0-0312 1 8 29 80 0-0150 O'(250 1 44 27 30 0-0120 0 -0298 2 13 24 20 0 -0120 0-0208 3 9 19 0 0-0104 0 '0208 3 43 14 30 0-0094 0 '0156 4 22 8 45 0-0052 0-0073 69 Sunset. 0-0013 0-0033 On the 13th October, 1890, I made a series of octant observations ; but, as I donbted whether the sky was really clear (t.e , as the clear sky of Dacca in the cold weather), I made a series of sunstrips, under : — Table J. Time. Sun's altitude. Exposure for candle unit (Milrerton). Exposure for same (Dacca). 1890. 13th Oct., llh 12 12 1 3:>m . . . 0 ... 33 ... 5 .. 30° 15' 30 30 29 45 28 45 9 -0 sees. 9-2 9-4 0-75 9 -25 sees. 9-2 9-4 9-75 1 2 2 35 ... 13 ... 54 ... 27 45 23 30 19 15 16-0 14-75 19-0 10-0 12-0 15-0 In the first four observations, the sky was apparently, and dont less really, clear ; in the three latter observations, some slight invisible cloud over the Sun produced great changes in the sunstrips. From the exact coincidence in the readings in the four first obser- vations, at Dacca and Milverton, I think it follows (1) that there was no material difference in my candles at Dacca and Milverton ; (2) that the chemical action of the Sun at the same* altitudes was the same at Dacca and Milverton. It is also clear that the number of really fine hours of sky in England (i.e., when it can be compared with the Dacca cold- weather sky) is very small — perhaps not a score in the year. And further that, in a great many apparently clear skies in England, there is Photometric ObservAtims of ilic Sun and Sku. 279 present some haze, visible or invisible, that affects the readings of the chemical action on sensitised paper very largely, even to 50 per cent. The octant observations, the intensities estimated on the first of the above strips, are as follows : — Table K. Time. | Sun's altitude. 1 [V] = [W]. 1890. 131 h Oct., I2h 4*» ! 30° 45' 0 -0268 1 8i .... I 28 30 0-0267 1 39 , 27 30 0 -0251 2 181 ! 23 15 0 -0244 2 59 J 18 30 0 -0216 '/, 24 1 15 45 0 -0194 4 m 9 45 0-0055 4 48 3 0 0 '0041 The values of [V] = [W], being so much greater than I expected, me to imagine that, though the sky was apparently clear, the observations might have been affected by the hygrometric state of the atmosphere. There had been a fog in the morning, and the air ras, though translucent, saturated all the afternoon. The next day, the 14th October, was a similar day (fog in the loruing), and I commenced octant observations much earlier in the dng. The results are given in the following table : — Table L.— Octant Observations, 14th October, 1890. State of sky. Time. Sun's altitude. [V] = [W]. [U]. ' Clear sky, but slight fog family to be -\ seen. flh 38m A.M. 10 8 10 39 11 2 11 32 12 1 P.M. 12 30 22° 48' 25 15 27 30 29 0 29 45 30 45 •SO 0 0 -0217 0 -0235 0 "0272 0 -0217 0-0217 0 -0272 0-0290 0 -0217 0-0254 0 -0272 0 -0326 0 -0326 0 -0399 0-029 Light fleecy clouds / in the sky octant. \ 1 0 1 30 29 0 27 30 0 -2540 0 -3080 0-3990 0 -0435 Clear, but still faint"! clouds. j 2 19 24 0 0 -2720 0-2720 Clear 2 45 21 0 0 -0210 0 '3290 Partial clouds j 3 15 4 0 37 15 11 30 0 -0163 0 0091 0 -0355 0 -0127 •280 Photometric Obnert'ations of the Sun and Sky. The effect of the faint fog in increasing the value of [V] = [W] is plainly seen in the morning observations. The effect also of a very few faint fleecy clouds is seen in the increase of [V] and of [U] for the observations at lh Om and lh SO™, before which no clouds had been visible. The air was saturated the whole day. The candles which I used in all these observations, were the " Belmont Sperm," supplied to me so as to burn 100 grs. in 47 minutes. Pliotometric Observations of the Sun and Sky. 279 present some haze, visible or invisible, that affects the readings of the chemical action on sensitised paper very largely, even to 50 per cent. The octant observations, the intensities estimated on the first of the above strips, are as follows : — Table K. Time. Sun's altitude. [V] = [W]. 1890. 13th Oct., 12h 4Jrm .. 30° 45' 0 -0268 1 8* 28 30 0-0267 1 39 27 30 0-0251 2 18i 23 15 0 -0244 2 59 18 30 0 -0216 3 24 15 45 0 -O194 4 11* 9 45 0-0055 4 48 3 0 0 -0041 The values of [V] = [W], being so much greater than I expected, d me to imagine that, though the sky was apparently clear, the observations might have been affected by the hygrometric state of the atmosphere. There had been a fog in the morning, and the air J, though translucent, saturated all the afternoon, he next day, the 14th October, was a similar day (fog in the morning), and I commenced octant observations much earlier in the morning. The results are given in the following table: — Table L.— Octant Observations, 14th October, 1890. State of sky. Time. Sun's altitude. [V] = [W]. [U]. r Clear sky, but slight fog family to be •{ seen. I. 9h 38™ A.M. 10 8 10 39 11 2 11 32 12 1 P.M. 12 30 22° 48' 25 15 27 30 29 0 29 45 30 45 30 0 0 -0217 0 -0235 0 '0272 0 -0217 0-0217 0 -0272 0 -0290 0 -0217 0-02.- 4 0 -0272 0 -0326 0-0326 0 -0399 0 029 Light fleecy clouds ( ^in the sky octant. \ 1 0 1 30 29 0 27 30 0-2540 0 "3080 0-3990 0 -0435 |Plear, but still faint "1 clouds. J 2 19 24 0 0 '2720 0 -2720 Clear 2 45 21 0 0 '0210 0 -3290 Partial clouds -| 3 15 4 0 17 15 11 30 0-0163 0 0091 0 -0355 0 -0127 VOL. XLIX. 28U Prof. E. A. Schafer. On the Minnie Structure of the The effect of the faint fog in increasing the value of [V] = \V is plainly seen in the morning observations. The effect also of very few faint fleecy clouds is seen in the increase of [V] and [U] for the observations at lh 0™ and lh 30™, before which no cloi had been visible. The air was saturated the whole day. The candles which I used in all these observations, were thi " Belmont Sperm," supplied to me so as to burn 100 grs. iu minutes. " On the Minute Structure of the Muscle-Columns or Sarc styles which form the Wing-Muscles of Insects, liminary Note." By E. A. SCHAFER, F.R.S. Receiv December 15, 1890,— Read January 8, 1891. [PLATBS 4 & 5.] The fibres of the wing-muscles of most insects are made np readily separable longitudinal elements, which are often called t! " wing-fibrils," although several observers have remarked the exi ence of an apparently fine fibrillation in them. To avoid ambigui I shall employ the term " muscle-columns " (Muskel-tdulchen, K liker), or its equivalent " sarcostyles,"* to designate these elemen They are united together to form the fibres by a not inconsiderab amount of granular interstitial substance (sarcoplasm, Rollett This substance has been regarded (Ram<5n y Cajal) as the true tractile material of the muscles, but it is easy, nevertheless, observe the contraction of the sarcostyles, isolated in white of e, a fact which has been pointed out by more than one writer on subject (Merkel, Kolliker). If an insect of which the wing-muscles are of the cha above described is cut open and placed in alcohol of about 90 p for twenty-four hours or more, and is afterwards transferred glycerine, the sarcostyles of the wing-muscles can be isolated examined without difficulty; they exhibit almost every phase extension and retraction (or contraction), and the usual appearani of alternate dark and light transverse bands, with a fine li traversing each light band. When stained with dyes, such haematoxylin, the dark bands are found to take the staining m intensely ; the fine transverse lines are much less stained, and clear bands hardly at all. The various parts of the sarcoflM evidently differ from one another in their behaviour to staining reagents, and the transverse striation is not to be explained by thi effect of the varicosities of the sarcostyle upon the light transmittet * £ap(, flesh, ari>\o(, a column. Muscle- Columns which form the Winy-Muscles of Insects. 281 through it (Haycraft) ; moreover, many of the sarcostyles show no such varicosities. A more valuable, because more sharply selective, method of staining is that recommended by Bollett (' Wien. Akad. Denkschr.,' vol. 51) for alcohol-glycerine muscles. This consists simply in the after- application of the gold-formic method to the tissue. In place of treating the fresh muscle with, chloride of gold and afterwards with formic acid, the alcohol muscle, which has been afterwards steeped in glycerine, is taken. If fresh muscles are thus treated, the sarcoplasm alone is stained, the earcostyles remaining colourless (or they may be entirely dissolved by the action of the formic acid). In this way, in the leg-muscles, the of ten- described appearance of a network is obtained. But if the alcohol- glycerine muscle be taken, the reduction of the metal takes place in the sarcostyles, and almost exclusively in their dark bands, so that, while the interstitial sarcoplasm and the clear bands of the sarcostyles remain clear and colourless, the dark bands of the sarcc- styles are deeply coloured of a tint varying from an intense purple- red to a faint purple-blue. Rollett recommends the application of this method to the study of the structure of the leg-muscles, but it is still better applicable to that of the wing-muscles, since it brings out in them, with a clearness which renders the application of the photo- graphic method comparatively easy, points of structure which, up to the present, with the usual methods of investigation, have remained 3ure. Jefore describing the special points which are thus capable of elucidation, it is necessary to adopt names for the several parts of the sarcostyle. For the more or less cylindrical disk which forms the dark band I shall retain the name " sarcous element," without thereby intending to imply that it accurately corresponds to the part to which that name was originally applied by Bowman ; in a general sense, I believe that it will be found to do so. The term represents, on the whole, the Querscheibe of the German, the disque epais . of French, authors. The fine line which bisects the light band I shall term "transverse membrane" (Quermembran, Krause ; Zwischen- schcibe of German authors; disque mince of French writers). The light space separating the ends of the sarcous elements from the transverse membranes may, for the present, be simply spoken of as the "clear interval;" it corresponds with the isotropons substance of authors. The segment of a sarcostyle comprised between two transverse membranes may be termed " muscle-segment " or " sarco- mere " (Muskelkdstchen, Krause). The relative amount of the sarcomere occupied by its several parts varies with the degree of extension or retraction (? contraction) of the tissue. In the retracted condition (figs. 1 and la) the sarcostylp, which is relatively thick and moniliform, appears formed almost u 2 282 Prof. E. A. Sclmfer. On tJie Minute Struct ,trf of tlir entirely of the sarcons elements, which are distinctly bulged, and arranged closely succeeding one another with but narrow clt intervals between them. In these very narrow clear intervals the later ally-stretched and thinned-out transverse membranes cannot be seen unless the sarcons elements are forcibly dragged somewhat apart ir the process of isolating them ; if this is done the transverse nu branes become visible (figs. 2 and 2a). In moderately extende sarcostyles (fig. 5) the sarcous elements are more separated from or another, the clear intervals being correspondingly longer and tl transverse membranes distinct. In greatly extended sarcostyles (figs. and 3a) the sarcous elements are not only lengthened and rauc narrowed, but show a tendency to separate in the middle into halves, leaving a space between them. The clear intervals are lengthened, and the transverse membranes are thickened ; the whol sarcostyle being narrowed. It may be inferred, from the separatk of the sarcous element, that it is really constituted of two halves, wl in the retracted fibre abut against one another in the middle of muscle segment, bat in the extended fibre are separated from or, another. Indications of this separation can be made out even in the noi extended sarcous clement, as in some of those represented in fig. Whether or not there is a fine membrane between the two hah as described by Hensen, my preparations do not enable me to det mine. Nor have I been able to observe in them the farther tion, with still farther extension, of separate disks (accessory dii Nebenscheiben) from the ends of the sarcous elements, a separatk which has been described and figured by several good observers. In the preceding statements and descriptions there is nothing tl is altogether novel or that has not been described with sufficit clearness by previous authors. But the application of photograph leaves no room whatever to doubt the accuracy of those descrij tions. .There is, however, one essential point of structure which I have 01 seen clearly in preparations made by this method, and which is distinctly shown in the photographs. Various authors (Wagem Krause, Kolliker, van Gehuchten), as before said, have described fibrillation of the sarcostyles of the wing-muscles ; or at least a lonj tudinal striation of the sarcous elements, with a dotted appearance the transverse membranes. This striation is very plain in several those wing-sarcostyles which are here photographed, and also in others which are similarly prepared. It is even plainer under 1 microscope than in the photographs, because the mass of red-stair substance which forms the sarcous elements allows hardly any actinic light to reach the photographic plate, and the sarcons elements, well stained, look, therefore, nearly uniformly black on the posit ivt-. It is very difficult, however, to trace the longitudinal striatiou> Muscle- Columns which form the Wing-Muscles of Insects. 283 through the clear intervals under the microscope, and I was at first disposed to believe that it was confined to the sarcous elements. But the first photograph which was taken showed faintly, but unmistak- ably, that it extended also through those intervals. This can also be detected at certain parts of those photographs which are here repro- duced. The longitudinal striation, therefore, although by far the most marked in the sarcous elements, extends through the whole length of the sarcostyle. It might, therefore, be supposed to represent a fibrillation of the sarcostyle, and this is the view which has been taken by all previous authors who have noticed the appearance. They have supposed the muscle-column to be constituted of a number of juxtaposed fibrils, each of which is composed of successive alterna- tions of the substance composing the sarcostyle, each one, therefore, being composed, in the middle of each segment, of a rod-like portion of the sarcous element ; at either end of this, and continuous with it, of a portion of the substance of the clear interval ; and, lastly, at the ends of the segments, of a portion of the transverse membrane. The sarcons element is, according to this view, formed by the juxta- position of a number of rod-like elements, which are stained by hsematoxylin and similar methods (amongst which must be reckoned this alcohol-gold method) ; the clear intervals being formed of continua- tions of these rod-like elements, which are, however, of a different chemical nature since they do not take these stains, and exhibit differ- ent optical properties ; and the transverse membranes of minute, dot- like elements having, again, different chemical and optical properties from the other parts. (The accessory disks, since they are inconstant, may, in this brief preliminary communication, be left out of account.) But the optical sections of the sarcostyles (figs. 6, 7a, S, and 8a), i.e., more especially of their sarcous elements, which, in teased preparations of muscles prepared by the alcohol-gold method, are frequently set free in the preparation, and are seen lying, as often as not, upon one surface, show conclusively that the above supposition regarding the fibrillar constitution of the sarcostyles is entirely erroneous. The sarcous elements are not made up of a bundle of rods, but are formed of a continuous substance (sarcous substance), staining with haematoxylin and with gold after hardening in alcohol, which sub- stance is pierced by tubular canals which open at each end of the sarcous element, and in its middle abut against one another at the plane of Hensen's line. The optical section of each sarcous element shows a dozen or more of such canals, and the contents of these canals are, to all appearance, freely continuous with the transpa- rent, colourless substance of the clear intervals ; this can be made out in the longitudinal views. The longitudinal striation of the sarcous element is due to this canalisation ; that of the clear interval to a prolongation of delicate lines (which may, perhaps, represent 284 Prof. E. A. Schafer. On the Minute Structure of the thin septa) of the sarcons substance through the clear interval to the transverse membranes. The whole sarcostyle appears to be itse enclosed by a membrane of extreme delicacy. If we assume, as is to all appearance the case, that the substance the clear interval is of a fluid or semi-fluid nature, the above view the constitution of the sarcostyle, which is illustrated with nnmi takable clearness in the photographs, enables one to form a tolerabh reasonable idea as to the physical change which may occur when th sarcostyle passes from the condition of extension to that of retraction and vice versd. For if the sarcostyle be extended, the sarcous element being marrowed and laterally compressed by the extending force, th fluid which is contained in their canals will become squeezed out, an will pass into the clear intervals, while, at the same time, the procesi of extension will elongate the sarcoas elements and separate then further from the transverse membranes. With further extension, separation of the sarcons element in the middle may also occur some of the expressed fluid passing into the interval between the tw halves.* On the other hand, when the extended sarcostyle becomes retracte* (? contracted), the sarcous elements swell and the clear interval become shortened so as eventually almost to disappear. This can onl be effected by the absorption of the homogemeous substance of th clear intervals into the sarcous element, and in all probability it i imbibed into the canals or visible pores of the sarcous substance The process may, in fact, be roughly compared with that which woul occur with a series of pieces of sponge, placed at short intervals, in thin- walled elastic tube filled with fluid. If the tube were extender the fluid would be squeezed out of the pores of the sponge, am would go to increase the volume of that in the intervals ; on relaxin the extending force, the fluid would be re-imbibed by the sponge, an< the intervals would be diminished. This comparison is not intend* as an explanation of the mechanism of muscular contraction, bu merely as an illustration of the physical changes which may reason ably be supposed to accompany the varying conditions of extension o the muscle. The subject of this preliminary communication is treated of m fully in a detailed account of the structure of muscle which wil shortly appear in the ' International Journal of Anatomy and Ph logy.' Since, in that account, I shall have occasion to refer * This separation does not always occur with continued extension, for in carcostyle photographed in fig. 4 the sarcous elements of the extended part, although they show the effect of traction in their elongation and narrowing, are not separated and contracted in the middle, as in the sarcostyle shown in fig. 3, but are even slightly bulged at the centre. There appears, however, a slight tendency for ll.ci.- ends to separate as (? accessory disks). Muscle-Columns which form the Wing-Muscles of Insects. 285 considerable length to the views and statements of other recent writers on the same subject, and to indicate the bearings of these observations upon the wing- muscles on the more intricate subject of the structure of the leg-muscles of insects, and of the ordinary skeletal muscles of vertebrates, I have omitted such references and indica- tions from the present notice. I may simply state, however, that for reasons which are given at length in the article above referred to, I regard the structure of the wing-muscles of insects as furnishing the key to the understanding of muscular structure in general, and I believe that it is possible to draw a comparison detail for detail between the two kinds of muscle which shows a complete correspond- ence in all essential particulars. DESCRIPTION OF THE PHOTOGRAPHS. (PLATES 4 AND 5.) All the figures upon these plates are photographs of parts of sarco- styles of the wing-muscles of the common wasp, which had been prepared and stained by the method mentioned on page 281. In specimens thus prepared there is a considerable amount of variation in the degree to which the sarcostyles, and even the sarcous elements of the same sarcostyle, are swollen by the dilute formic acid, into which the muscle is placed after having been acted upon by gold chloride. This is noticeable in fig. 8, a part of which is further magnified in 8a, where, in the same sarcostyle, some of the sarcous elements are narrow, and others wide. The latter do not, I believe, belong to contracted or retracted portions of the sarcostyle, but are merely more swollen by the acid, probably because they happened to be less fixed, i.e., coagulated by the previous treatment with alcohol and gold. It is noticeable also that these more swollen sarcous elements are fainter in the photographs ; this is due to the fact that they are always of a bluish tint; whereas the less swollen sarcous elements are deep-red, and hence come out nearly black. The former, however, show the longitudinal striation, i.e., canalisation, better than the latter. It must further be stated that the extension of the sarcostyles shown in fig. 8 has been produced in teasing the preparation with needles by the demi-desiccation process ; it is quite different from the extension shown in figs. 3 and 4, which has been brought about in the living tissue prior to the advent of the hardening fluid. The sarcostyles represented in figs. 1 and 3, and the lower part of fig. 4, have been specially selected to illustrate the characteristic appearances of retraction (? contraction) and extension, because they were very distinctly red-stained and showed neither distortion from being swollen by acid nor dislocation from mechanical stretching after hardening ; all the other sarcostyles rthich are shown in the photograph exhibit such distortion or disloca- tion to a greater or less extent. On the Winy-Mutclex of Insect*. PLATE 4. Fig. 1. Part of a sarcostyle which has become fixed in the retracted (? contracted) condition. — Fig. la. The same, more magnified. Fig. 2. Part of a retracted sarcostyle, showing a slight mechanical dislocation of some of the sarcous elements, which has been produced after hardening. — Fig. 2o. The same, more magnified. Fig. 3. Part of an extended sarcostyle. — Fig. 3a. The same, more magnified. Fig. 4. Portion of a sarcostyle, which, at one end, is much extended, at the other moderately extended, these conditio: having probably been present before hardening. The middl part is somewhat dislocated, probably after hardening. — Fig. 4a. The same, more magnified. PLITB* 5. Fig. 5. Parts of three moderately extended sarcostyles, wil granules of the sarcoplasm lying between them. Fig. 6. Part of two adjacent sarcostyles, somewhat swollen by tl formic acid. The upper terminal sarcous element of each one is swollen and flattened out, and is lying obliquely, < having been probably touched by the needle in teasing ihc muscle. These show, especially the right-hand one, tht tubular structure of the sarcous elements. Fig. 7. Two sarcous elements lying free : one is represented ii profile, the other in optical section. Fig. 8. Photograph of part of a microscopic field, containing number of more or less broken-up sarcostyles, and showing several of the sarcous elements lying flat, and others in profile. The tubular or canalised structure is very evident. (Tl globules represented are oil-drops which had accidently into the glycerine in which the specimen was mounted.) Fig. 8a. Middle part of the above photograph, enlarged; *, «, sarcous elemeuts in profile view. Those to which the lett are adjat.-ent show the line where separation occurs when tl sarcostyle is extended (as in figs. 3 and 3u). Some of the other (bluer) acid-swollen elements, which come out less darkly in the photograph, exhibit the canalisation better. «', «', sarcous elements seen on the flat, i.e., in optical section ; o, o, a« i- dental oil-globules. Figs. 1 to 8 are photographs taken with Zoiss's 1'30 aperture, 2-min. homogeneous achromatic objective, and with projection ocular. They are magnified 870 diameters. Figs, lo, 2a, 3a, &c., are enlarge- ments from the same negatives. They represent the tissue elements 'luaguified 2300 diameters. Stoc.jKQy.tioc, 1. I 3. 2. I I I s I s m 4,0, ' m - Proc.Xoy. She. Vol.4&PL6 On the Minute Structure of Striped Muscle, fyc. 287 " On the Minute Structure of Striped Muscle, with Special Reference to a New Method of Investigation, by means of ' Impressions ' stamped in Collodion." By JOHN BERRY HAYORAFT. M.D., D.Sc., F.R.S.E. Communicated by Dr. KLEIN, F.R.S. (From the Physiological Laboratory, Univ. Edin.) Received January 2, — Read January 8, 18yl. [PLATE 6.] Historical. Curiously enough many of the early microscopists — Schwann for instance — recognised that the fibrils of a muscle are not simply threads of uniform thickness, like those of connective tissue : they were able to demonstrate their varicose character, even with the imperfect lenses ac their command. They concluded — of course without any experimental proof — that the cross striping of the fibrils, and, therefore, of the fibres themselves, was an optical expres- sion of such varicosity. But Bowman, while believing apparently that the striping was optical, and comparing the muscle fibril to a beaded rod of glass, succeeded in breaking up the fibrils into little segments. According to his view, these " sarcous elements," as he termed them, joined end to end by cement, constituted a muscle fibril. He further believed that each sarcous element coincided in position with one of the alternating stripes, the other kind of stripe corresponding with the position of the cement joining the segments together. But no sooner had histologists begun to associate the cross-striping with structural differences along the fibrils, than their varicosity was almost entirely lost sight of, and every new stripe (and many were discovered by Dobie, Hensen, and others) was gratuitously assumed to mark the position of some new structure. There was, however, much to excuse what might at first sight appear to have been a great want of critical acumen, for the applica- tion of staining reagents appeared to bring out alternating differences of structure along the fibre. Thus, with logwood or picrocarmine or eosine, the clear stripe (isotropic bands), the dark stripe (Querscheibe; disque epais), the band of Hensen (Mittelscheibe ; disque median), and Dobie's line (Querwand ; strie mince), all appear to take on the stain in different degrees, so much so that, in specimens successfully prepared, some stripes appear deeply stained, others hardly at all. Then, again, Brllcke and other investigators demonstrated that the fibrils consist of alternating parts, some of which appear to be doubly, and others singly, refracting. Overwhelmed by what appeared to be such a mass of evidence, the Dr. J. B. Haycraft. histologist of ten or twenty years ago felt bound to assume that the fibril was a very complicated structure, and he never doubted that a muscular fibril consists of a series of alternating and recurring struc- tures. It then became his duty to find out what these structures really might be, and what part they play during a muscular contraction. The lines of Dobie are often seen as narrow dark bands, which were believed to be membranes (Querwand), and it was held that these membranes separated up the fibrils into little boxes (Mnskel- kastchen), so that a fibril consists, according to these authorities, of a series of little boxes, joined end to end, containing the substances whose position was marked by the other stripes. Certain of these stripes (the dim ones) were considered to mark the position of solid or relatively more solid substances, and the other stripes (the clear ones) to consist of fluid or relatively less solid substances. The appearance of the stripes, the staining, and their action on polarised light gave, at any rate, some colour to this hypothesis, for the dim stripes appear to have more substance than the clear stripes ; they appear to stain with reagents, and to doubly refract light, which latter property is certainly seen in some solids. The light stripes, on the other hand, appear deficient in substance and solidity, they stain less readily, and they simply refract light (a property common to all liquids, and some solids). The Muskelkastchen hypothesis seemed, therefore, feasible enough, and having under their microscopes little boxes containing more solid and less solid parts in alternating layers, Krause, Merkel, Engelmann, and others, sought to explain, each in his own way, the most obvious phenomenon of contractility, namely, the shorten- ing and thickening of the contractile tissue, as beiug due to the interaction of these structures. Histologists are accustomed to observe osmotic changes, the swelling up and the shrinking of red blood-corpuscles, for instance, and to see the resulting alterations of form. Under these circumstances it was not unnatural for them to suppose that during contraction the more solid parts of the Mnskelkastcben imbibed fluid from the less solid parts, in such a way as to alter the shape of the muscle box, making it shorter and thicker, and causing, in consequence, the whole fibre to change in the same way. In apparent support of this theory, the stripes in the muscle boxes change their relative thickness, and alter in appearance, in the manner so carefully described by these observers. There seems, in fact, only one objection to this osmotic theory which would at once present itself to the eye of the critical observer ; it is the time take by the process, for osmotic changes are slow in their very nature, ant the muscles of an insect's wing can contract over a hundred times a second. On the Minute Structure of Striped Muscle, Sfc. 289 Personal Observations lefore the Year 1880. More than ten years ago it was my duty, as a young teacher, to make myself familiar with the current literature bearing upon the structure and function of muscular tissue. Even then the number of publications was very great, and I can now recall the despair with which I tried to get a grasp of a subject about which no two observers could be found to agree. While endeavouring to verify some of the statements I had read, I found out for myself that the fibrils are iu reality varicose threads of tissue, presenting alternate swellings and constrictions of their substance. At once the conviction forced itself upon my mind that the striping might after all be an optical expres- sion of the form of the fibrils, and have nothing whatever to do with their internal structure ; and it was not until my results were in manuscript form, and ready for publication, that I got access to the older and almost forgotten literature in which I found the same views freely expressed, although without any attempt at their proof. When I had made certain that, both in the fresh, and in the prepared muscle, the fibrils are invariably varicose, then I felt that the position of the subject was as follows. Such fibrils are bound to be cross- striped like all other objects of similar shape, viewed by transmitted light. It may be that the cross-striping observed is due to the vari- cosity alone, or to the varicosity and to .co-existing structural differ- ences as well ; and, under these circumstances, before we are in a position to take any further step in an investigation into the nature of the muscular fibre, it is imperative to eliminate the appearances due alone to varicosity. My first endeavour was to ascertain whether there are any stripes that do not correspond in their position with inequalities in the thick- ness of the muscular fibrils. Of course in many cases it is difficult, especially if the fibrils or fibres are somewhat distorted, to make out the border clearly ; but in good specimens, in a suitable position for study, I found that the striping, both in the contracted and uncontracted fibre, corresponds invariably to either thickenings or constrictions of the fibrillar sub- stance, and in this investigation the muscular tissue of many repre- sentative species, both Vertebrates and Invertebrates, was examined. The broad dim stripe occupies the position of a thick bulging part of the fibre, and Hensen's stripe, when present, corresponds to the posi- tion of a shallow depression in its centre. The clear stripe lies in the constrictions of the fibril and Dobie's line corresponds with a tiny swelling in its centre. In addition, the stripes can be reversed by altering the focus, just as is the case with a little varicose glass thread, the scale of a Lepisma, or the shadow in the centre of a red blood-corpuscle ; indeed Bowman 290 Dr. J. B. Haycraft. Fio. 1. Bowman'* element*. Qucrscheibe. Mittelscheibe. Hensen't line. Querwand. Dobie's line. Isotropic ! clear stripe. Part of a muscular fibril is represented in this figure, and it will be noticed that the striping of the fibril corresponds with the position of inequalities in its thickness. actually described the striping in the reverse focus to that generally adopted, calling " clear " what we speak of as the " dim " band. A very simple method of determining exactly what part varicosity plays in the production of the cross-striping then suggested itself to my mind ; it was to immerse the fibrils in a fluid having the same refractive index. Under these circumstances it is obvious that these stripes, which are due to varicosity alone, will disappear, bat the striping will become even more marked, if there are alter- nating structures along the fibre possessed of different refractive indices. At Professor P. G. Tait's suggestion, I placed the fibres in a mixture of alcohol and oil of cassia, varying the proportions until 1 approximated to the refractive index of the fibrils. The striping never entirely disappeared, bat it grew fainter and fainter, and I am inclined to explain the partial failure of this experiment on the grounds that, unlike a glass rod, the muscle fibres imbibed the medium in which they were embedded. As a result of this slow imbibition, the refractive index of the fibres would be constantly altering, and it would be a matter of the greatest difficulty to make it exactly the same as that of the surrounding medium. In addition to this, coagulation would be almost certain to take place within the fibrils, destroying their optical uniformity. While looking upon the results I had obtained as valuable but not conclusive evidence, I sought to solve the problem in another way. 1 took the living muscle of a Crab or Fly, and, while examining it under the microscope, I pressed down the cover-glass with On the Minute Structure of Striped Muscle, $•<•. 291 needle. Under these circumstances, those fibres -which were pressed upon lost their cross-stripes, and looked extremely like connective tissue. Of course it might be urged that the fibres were by this pressure entirely disorganised, and no conclusions can legitimately be drawn from the. experiment, but to this it can be replied that if there really are little bands of tissue so clearly distinguishable from each other, as those who hold the MusJcelkdstchen hypothesis believe, these or their traces should be found scattered about throughout the pre- paration. In point of fact, as yon press upon the cover-glass the stripings gradually disappear with increased pressure, and in the ill- defined fibrillated structure that remains there are no traces of the broken Muskelkastchen. And finally, if more proof is wanted, it is possible by means of a screw, which raises or lowers the cover-glass, first to press upon the fibres and cause the striping to disappear, and then on raising the cover-glass to cause them to reappear once more. We can only explain this result on the assumption that the varicose fibrils are flattened out, and that the striping caused by their vari- cosity disappears in consequence. There were, however, three important facts which had to be thoroughly accounted for, before it could be affirmed that the fibrils do not consist of the alternating structures supposed to exist ; these facts were the effect of cleavage, of staining and the action of polarised light. The muscle fibrils can be broken across into the sarcous elements described by Bowman ; but a careful study of the question soon convinced me that the cleavage is always across the thinnest parts of the fibrils, taking1 place in the substance of the clear stripe. If Dobie's line is at all marked, the cleavage takes place near the little swelling which corresponds to it, and through the substance of the clear stripe. Reference to fig. 1 will at once show that here we have to deal with the thinnest part of the fibrils, and it is there- fore begging the question to assume anything over and above this mechanical reason for the cleavage, for every varicose rod will break ross at its thinnest part. The phenomenon of transverse cleavage cannot therefore be taken in itself as an argument in favour of structural differences along the fibrils. The appearances seen in stained preparations can also, I pointed out, be satisfactorily explained on the varicosity hypothesis. We find that whatever else is employed, and at whatever focus you adopt in your examination, those stripes which in the unstained preparations appear dim also appear to take on the stain, while those stripes which appear clear and bright are unaffected by it. In fact, the difference in colour is entirely a question of " saturation," for whenever there is a flood of light, as in a clear stripe, the colour of the fibre at that part becomes unsaturated by it. It is easy to convince oneself practically of this fact by the examination of varicose threads of faintly coloured 202 Dr. J. B. Haycraft. glass t'n a ray of parallel light. Rods of faintly tinted glass of the same shape as the muscle fibres, having tiny globules — Dobie's lines — and broader swellings for the dim stripes, when examined under the microscope, or in the field of a lantern, give as strong colour differentia- tions as any muscle fibres, the constrictions coming out quite colour- less, while the dim band and Dobie's line are sharply brought out by their deepened colour.* One of the chief faults of which I was guilty when publishing these results in 1880 was that I did not sufficiently lay stress on the appearances presented by a coloured or colourless varicose thread of glass when placed in the path of a parallel ray of light. It is quite different from the same thread when examined in diffuse daylight, for in the latter case a hundred images fall upon the retina at the same time, and the striping and colour differentiations are confused. One can see little appearance of striping, and if the glass is coloured it may appear very much of the same tint ; place it in a lantern, or even lay it down on a piece of white paper, and the picture is quite different. As one is accustomed to view objects in diffuse daylight, one is not prepared to interpret correctly the character of such an object when viewed through a microscope : the clear well-defined bands and colour differentiations of a muscle fibril are not the ap- pearances of a varicose thread as seen in diffuse daylight, but they are those of a similar fibre observed in parallel light when practically a single image falls upon the retina. Lastly, we come to the action of polarised light, and here at once the phenomena by no means prove structural differentiation, along the fibre. There are many questions which lead to complication. We have the varicosity of the fibril, which will alter the path of the polarised beam and produce apparent differences along the fibre when there may be in reality none at all. Then we have as a complication the interfibrillar substance, which is simply refracting, and which is chiefly lodged in the neighbourhood of the clear stripe. I was not prepared to say, under these circumstances, what is the action of polarised light on the fibrils, nor do I wish to commit myself now : it is sufficient to say that, even if we grant that alternating singly iso- tropous and doubly refracting anisotropic bands exist along a fibril, it does not follow that these are bands of more solid and less solid material : the whole difference may be due to molecular tension. A fibre of such a shape, as was pointed out to me both by Professor Stokes and by Professor P. G. Tait, is almost bound to possess altern- ating parts in different conditions of molecular tension, and give the familiar appearances when examined by polarised light. * In doing this experiment, onlj faintly tinted glass must be used, and, aa this is difficult to obtain, I generally use hollow varicose tubes of white glass filled with coloured fluid. On the Minute Structure of Striped Muscle, fyc. 293 A paper containing the above results was presented to the Royal Society of London by my kind friend Professor E. Klein, and was printed in the ' Proceedings ' of 1880, and in the ' Quarterly Journal of Microscopical Science,' 1881, and in this paper I ventured to assert that I had been able to explain the appearances generally considered to indicate structural differences -in the course of the fibrils as being due to the varicosity of the fibrils themselves. I further stated that of course structural differences might exist, but that the proof of their existence was not as yet forthcoming. My views were received in many quarters with kind consideration, but they were only very partially accepted. For my own part, as soon as I had published them I resolved not to think about the subject again for some years, when, with more matured experience, I might return to its consideration and picking up the threads that I had dropped unravel them with a more skilful hand. Recent Investigations with the Collodion Impressions. Last winter (1889-90) an idea occurred to me which led once more to my examination of the subject. It struck me that if I could " stamp " some soft transparent solid with muscle fibres it might be possible to obtain impressions of the fibres on the soft material. If these impressions had smooth unstriped depressions corresponding to the fibres, this would indicate that the striping was caused by struc- tural differences within the fibrils ; if, however, the impressions were striated, this could only be explained on the ground that the striation of the "stamp" — the muscle — was caused by the/orm of the fibrils, which form and which striation were transferred to the soft material in the process of stamping. It seemed improbable that I should succeed in getting faithful im- pressions of such microscopic objects, yet I felt that it would be well worth while making the attempt, for the results if obtained would be lost conclusive. I experimented with every substance that I could link of, using wax of various kinds, glass, gelatins, glycerin jelly, transparent soaps, &c. Once or twice I thought that I had obtained rery partial success, but my difficulties were great, for when- ever I hit upon a substance like gelatin, for instance, which would in intimate contact with the fibrils, it invariably came away with lem when they were removed. I worked at the subject for months, rying every expedient which suggested itself to me, and in July, L890, I at last succeeded beyond my most sanguine anticipations. It occurred to me that perhaps collodion might be of service, for a thin layer dries quickly and forms a beautifully smooth transparent 1m. I accordingly prepared a film by allowing a drop of collodion fall upon a elide, and tilting the slide so that it flowed over it in 204 Dr. J. B. Haycraft. a layer of uniform thickness. When still somewhat moist I pressed against the film some roughly teased muscle fibres held on my finger tip. They came away quite readily when the finger was removed, leaving little " rnta " in the collodion obvious to the nnaidod eye. On examining these ruts with the microscope I found what I at first thought were actual muscular fibres still adhering to the collodion film, showing the fibrils and every detail of the cross striping with remarkable clearness. The ruts contained, however, no trace of muscular tissue when examined by the naked eye, for the slightest trace of muscle is at once recognised by its opacity. On looking at the specimen a few minutes afterwards, what was my surprise to find that all the appearances I had just seen had completely vanished, the ruts had disappeared, and the collodion film was flat and smooth. The explanation was very soon found, and no doubt remained that what I had at first actually mistaken for muscular fibres were it reality their " impressions," their subsequent disappearance beinj due to the contraction of the film, as it dried, pulling out every in- equality in its surface. It is very instructive to watch one of these collodion impressions ; at first clearly cut, with every stripe sharply defined, they gradually fade, and perhaps in five or ten minutes they disappear entirely. Sometimes a portion of a fibre really remains sticking to the col- lodion ; it is at once recognised by its great opacity. What astonished me almost as much as the perfect reproduction in the impression of every cross stripe was the ease with which these impressions can be made. One can hardly fail to obtain them, and at the International Congress in Berlin, while demonstrating the subject to the members of the Physiological and Anatomical Sections, I made over one hun- dred preparations — few of which were failures. Not only can one stamp with hardened muscle, but the fresh tissue can itself be used. Of course the fresh tissue is soft and does not make so good a stamp, the results are not so striking, but they are quite evident. In making impressions of a fresh muscle one can take a piece of muscle, say from a Rabbit, cut it through in the direction of the fibres, and press the cut edge for a second or so against the collodion film, which must be very soft : one rarely examines the film without getting some trace of an impression upon it.* If the impressions are examined with a high power, say 600 diameters, the following details can be made out. Each fibril, if a hardened * One can get impressions of other tissues, bone, tooth, hair, &c. A section of dry bcne comes out Tery well, and one can see in the impression the " set " of the lamellae, the lacunae and their canaliculae, and every detail with marvellous clear- ness. If a still moist film be pressed against the back of the hard, and then ex- amined, one sees the impressions of the imbricated scales covering the hairs on back of the hand far clearer than in the original. On the Minute Structure of Striped Muscle, SfC. 295 preparation be used for stamping, makes its own individual impres- sion in the collodion, which rises between the fibrils in the place of the interfibrillar substance, which has, of course, been removed in the ordinary preparation of the tissue. When the muscle is pulled away the impressions of the individual fibres can readily be made out, and the borders of the little varicose hollows are plainly to be seen ; the cross-striping, which can here only be due to the form of the impres- sion, is exactly the same as that of the muscle itself. To put it in another way, we have varicose threads of air, within surrounding collodion in the place of varicose threads of muscle surrounded by balsam or Farrant, and varicosity, the only common factor in the two cases, is alone the cause of the striping observed in each. Not only are the broad stripes well marked, but one can see with even greater ease than in the muscle itself the lines of Dobie and of Hensen. In the fresh muscle I have only once or twice seen the outlines of the fibrils with any degree of distinctness, but the stripings are more readily seen ; yet one would hardly expsct to get such good results from fresh muscle, both on account of its softness and from the fact that the fibrils are covered by sarcolemma. If the collodion be tinted, say with magenta or Bismarck-brown, impressions can be made in this coloured medium, and these show in beautiful detail the apparent stain differentiations observed in muscle. The broad dim stripe comes out red and appears like a solid, well-defined band, and the clear stripe in successful preparations appears by contrast devoid of colour. It will be seen from the above experiments that, as the stripings are all optical effects of varicosity, the very foundations of the Muskelkastchen hypothesis are removed, and we now come to the consideration of the phenomena of contraction. An " impression " of a muscular fibre shows in evert/ detail the appear- ances characteristic of the muscle used to stamp it, in whatever state of contraction or relaxation it may happen to be. — If a piece of muscular tissue, hardened in alcohol in the extended position, be examined under the microscope and its details studied, and if an impression of it be then made, the impression will show the same details that it shows. The same holds good for the contracted or semi-contracted fibre. Photograph I was very kindly taken for me by my friend Dr. Carrington Purvis, and shows the appearances presented by a Crab's muscle in a state of extension. The little varicose fibrils are seen separated by little varicose dark lines, the latter being the optical sections of the interfibrillar substance. Photograph II* is taken from an " impression " of a muscle in a * The photographs of the " impressions " were taken by my friend Dr. Eding- ton, to whose skill and interest I am much indebted. As the " impressions " only last about five or six minutes, and as with ordinary illumination an exposure of VOL. XLIX. X Dr. .1. I'. H.-.yrraft. similar condition, and it will be noticed that tin- appearance is essentially the same, except that the stripes are reversed, the little dots forming Dobie's line and the dim bands coming out bright, and the clear stripe appearing dark; the slightest alteration of the would have reversed the photograph and have given the ordi appearance. A contracted fibre has quite another appearance, for not only the cross-stripings much nearer together, but they have changed character. Without going into detail, at present, it is sufficient say that alternately dark and light stripes are seen, and that Dobie's line, so constant a feature in the extended fibre, is longer to be seen in the contracted condition ; the stripes, moreovi have altered in thickness relatively to one another. Now it is n less to again point out that the change in the striping has hithe been held to indicate changes within the fibrils of the nature osmosis, the stripes being taken to represent actual structures. Bo if an impression be taken of a muscle killed in contraction it showi every detail of a muscle in that condition, as photograph III, tak from a collodion impression, very well indicates. (In this photogra the clear stripes come out clear, and the dark stripes dark, just as the original muscle, but of course the appearance could be reve: by altering the focussing.) It follows that when a muscle passes into a condition of contracti the changed appearance is entirely due to a change in its form, and I have frequently stamped muscles which show in the same fibre boi the contracted and uncontracted state with the intermediate s These intermediate changes come out perfectly in the " impressions,' so that one can positively affirm that the striping is due to form, every change in striping observed during contraction depends upon some change of form too. Of course the imbibition theories of Kranse, Merkel, and Engelmann are no longer tenable, since the facto on which their theories were founded have received another explana- tion. The Muskelkastchen was evolved on the supposition that the cross stripes correspond to membranes and layers of tissue along the fibres, whereas the impressions prove that they are due to variations in the thickness of the fibrils in different parts of their course. The imbibition theories were evolved on the supposition that the changes in the striping observed during contraction are due to alterations in from ten to fifteen minutes is required, our first attempts were not as successful as might huve been desired, and those exhibited in Berlin were decidedly faint and wanting in density. Dr. Edington subsequently, adopting a suggestion of Mr. Forgan, used magnesium light in the place of the ordinary oil lamp, burning about one foot of the thin riband in the optical axis of the apparatus. This exposure, lasting only a few seconds, gave us very beautiful negatives, from which tin- photo- f riTure plate was taken. On the Minute Structure of Striped Muscle, fyc. 297 the relative quantities of fluid held by the substances producing the striping. Inasmuch, however, as the changes in the striping are due to changes in form of the fibrils, the very foundation of these theories has been removed. The Author's Views as to the Structure of Striped Muscle. Before proceeding further I would venture to state what I think we are in a position to affirm respecting the structure of striped muscle. The fibres consist of fibrils generally grouped together in bundles and separated from each other by interfibrillar matter. As tho fibrils are varicose, and have a different refractive index from the interfibrillar matter in which they lie. they, in consequence, present the optical striping possessed by all such bodies under similar circum- stances, and we have no reason to suppose that this striping has any other interpretation. The fibrils, from whatever point we look upon them, are composite structures, and their varicosity indicates this quite clearly. Each fibril has practically undergone segmentation into a series of tiny particles, although there is no evidence that these are separated from one another by membranes, or any other anatomical structures, and each little bit contracts on its own account so as to thicken and shorten. Although we know absolutely nothing as to what there is within each fibril, yet the condition of parts, whatever it may be, is probably the same in every Dobie's line, or in every dim or light stripe. Each light stripe may merely consist of contractile tissue in a different state of tension from that in the position of the dim stripes, and if so, that may partly interpret the polariscopic phenomena, but beyond the fact that a difference exists we are not in a position to make a further affirmation. When we study the change in form which these little segments undergo in passing from the relaxed into the contracted condition we come upon several curious facts, the interpretation of which is at present very difficult. Some muscles, and especially those of some of the lower Vertebrates appear to be very simple in form, and to undergo very simple changes during contraction. I hope to enter into greater detail in a subse- quent paper, but in the meanwhile I would simply state that the fibrils seem to be devoid of the tiny swellings which form the line of Dobie. The fibrils, therefore, possess simply alternate swellings (dim stripes) and constrictions (clear stripes). During contraction, the swellings become more marked as the fibrils shorten, the change being represented in fig. 2. In this case the dark stripes of the contracted fibre are at just the same parts of the fibril as in the relaxed condition. In other in most of the Arthropoda, for instance, the stripes are ersed, as already so well described by the German histologists. x 2 Dr. .1. I'.. Ih.vrrafr. Fio 2. & a FIG. 3. Jf C fl ¥• I'm. '2 (R) represents a relaxed fibril with a pin, A During its contraction (C), as the fibril simply otherwise changing its shape, the needle A is stripe. FIG. 3 (R) represents n relaxed fibril with a pin, A, and another pin, S, sticking into the swelling When contracting (O), the fibril is profoundly sticking into the clear stripe, and the pin R into , sticking into the dark strij shortens and thickens withe still seen sticking in the dai , sticking into the dark strij in the position of Dobie's lin modified in shape, the pin the centre of the dark stripe. The reason is that, during contraction, the fibrils change thei shape in such a manner that the parts which previously bulged no become the thinnest part (fig. 3). As the fibrils begin to cout the substance of the clear stripe becomes an eminence ins of a depression, and the little bulging part forming Dobie's li becomes smoothed out and gradually obliterated. The dark stri on the other hand, becomes the constriction in the case of tl contracted fibre, and, of course, appears now as a clear band. These points can only clearly be made out by studying all the int mediate conditions between complete contraction and relaxation, they are best seen in the living muscle fibres on which waves contraction are still slowly passing ; one may see them, too, upon the muscle impressions. I have never happened to make an impression of a fibre showing a series of these intermediate stages in a short piece of a fibre while engaged with Dr. Edington in photographing them, but fig. 4 shows very well the appearance ; it is a careful drawing of a Crab's muscle in a state of contraction, but bent at an angle so that the convex side is artificially extended. The Dobie'ft lines on the extended side are seen gradually to thin away, and gradually disappear on the contracted side, while the surrounding bands which appear as clear depressions gradually become dim elevations. Of course, this change of form leads to the shortening of the fibrils, but it is at present difficult to say why this reversal of the vari should occur ; at present, we have to accept it as an unexplained fact. On the Mini it I', Structure of Striped Muscle, $-c. 299 Fio. 4. drawing of a living and contracted Crab's muscle, which has been bent round and artificially extended on its convex lower border. The transitions between the relaxed and contracted parts are well seen. Dobie's lines (D) gradually fade away as you pass to the contracted condition, becoming invested by and then replaced by the dark stripe of the contracted condition. The dark stripe of the relaxed part (_B) fades away, and is replaced by the light stripe in the contracted part. any of the German histologists have described a condition observ- able before the muscle has completely contracted (Uebergangsstadium), irfcwhich all striping has disappeared, and this Merkel and Engelmann each explains on his own imbibition theory. Now, one can dog- matically affirm that in the greater number of fibres of which the tissue is in one part contracted and another part relaxed, and in which the intermediate stages are plainly visible, as in fig. 4, for instance, not a trace of such a condition is visible ; it is therefore not an essen- lly intermediate phase. I have had the privilege of seeing fessor Engelmann's preparations, and here it is seen, and in my n I occasionally come across it; but what I have invariably observed is this, that it is never seen in a fresh preparation free and unattached to cover-glass or slide. It frequently happens that fibres Jome pressed and otherwise fixed, and then it appears that when y shorten, the contracted part pulls upon the still extended portion, and diminishes by so doing the varicosity of the fibrils, and, in. consequence, the striping which depends upon it. The effect is ly the same as that produced by flattening out the fibres by ssing on the cover-glass ; in one case the varicosity is diminished obliterated by a pull in the length of the fibril, in the other case y pressure applied to its sides. One may, at any rate, state that in the vast majority of cases, as the varicosity becomes reversed, the ils never become uniform threads of tissue, for, as the dim stripe flattening out, eventually to form a depression, the clear stripe, ;h Dobie's line still visible in its centre, is becoming a ridge. ::: 300 Dr. J. B. Hay era It. The Interfilrillur Substance. The interfibrillar substance is not usually held to have the propc of contractility, aud it appears to me that the arguments based on its fancied homology to a cell network recently brought forward, espe- cially in England, can hardly be said to prove the contrary ; I hope to refer to this subject in a subsequent paper, to be devoted to the com- parative histology of muscle. From the varicose character of the fibrils, it follows that the interfibrillar substance is of the nature of a matrix or bed of tissue perforated by varicose tubes. It is like honeycomb minus its transverse partitions, or, better still, like mitrailleuse ; we have, however, to imagine the walls of the honej comb of variable thickness, sometimes thicker and sometimes thinne and the analogy is complete. In optical section, as when we fc a piece of muscle, this interfibrillar honeycomb will appear as photograph I or fig. 5. FIG. 5. Two fibres are represented, A and S. The interfibrillar substance is sti represented by the varicose lines ; the outlines of the fibrils are faintly sented at the borders of the figures. In A the fibrils possess well- Dobie's lines ; the swellings of the fibrils causing them are seen, Z>. In sequence, the cement matter forming single masses in B is in A divided two sets (heads of Schafer's muscle rods). In B Dobie's lines are not In diagram the cross-striping! of the fibrils has been omitted for the simplicity. Here the fibrils are left blank, and the interfibrillar substance represented by dark varicose lines, the optical sections of the loi tudinal walls of the honeycomb. The walls are thick opposite tl position of the constrictions of the fibrils which lie within the honey- comb, and thin wherejthe bulgings come. When a Dobie's bulge is present as at A, the bulgings, corresponding to the clear strip' divided into two (Schafer's muscle rods) ; but when Dobie's lim- is not well marked, we have the appearance seen at B. Of con; will be understood that where these thickenings of the honeycomb On the Minute Structure of Striped Muscle, SfC. 301 occur the fibres are encircled by a thicker band of int9r6brillar sub- stance, that the little beads or swellings in the diagrams are merely optical sections of the thicker parts of the honeycomb. These thickened portions, when very strongly differentiated from the fibrils, as by the gold method, may appear like transverse bars running across the fibrils in the region of the clear stripe, and the whole structure has unfortunately been misinterpreted by some observe! s into a network, the transverse links of which are the encircling and thickened parts of the honeycomb, while the longitudinal threads are the lines really marking the optical section of the honeycomb tubes. If any threads of tissue are to be actually seen, I quite agree with Professor Klein in ascribing them to precipitation within the inter- arillar honeycomb. The Physiological Explanation of the Varicosity. I may not unreasonably be asked to supply some hypothesis of my n in place of the exploded theories of imbibition, for, if we simply iew a muscle fibre as consisting of varicose fibrils, we have a bare lorphological fact without any physiological significance. Before oing this, I will venture to clear up one misunderstanding which has arisen concerning the morphological difference between striped and triped muscular tissue, although this question will, I hope, be ire fully discussed in a subsequent paper. The unstriated muscle is generally described as a nucleated spindle, presenting fine longitudinal fibrillation, and devoid of a true sar- colemrna, while the striped or voluntary fibre is described as a ;rillated thread of contractile tissue, invested by a sarcolemma derneath which numerous nuclei are placed. The heart muscle is generally looked upon as a tissue intermediate between the two. ut authors to whom we owe these ideas, have restricted their quiries to the Vertebrate histology alone. It is necessary to pass the region of comparative histology, before we can thoroughly >mprehend the subject. If we do this, we shall find that there are o chief varieties of fully differentiated muscular tissue. First of , there is the nucleated spindle devoid of sarcolemma and made tip fibrils cemented together, and we notice that these spindles may be iped or unstriped, the difference depending upon the rapidity of their traction. They are found in most divisions of the animal kingdom ; us, in the adductor muscles of Cardium, Pecten, Lima, rapidly iving Lamellibranchs, we have nucleated and striped spindles ; ese occur in the heart muscle of the Frog and many other animals, hile non-striped spindles are found in parts of the circulating and igestive systems where less active movements are required. Then again, there is another type of muscular tissue, consisting of 302 Dr. .1. I',. Haycraft. rylindrical threads, sometimes inv. .>tc should remain mixed, until one solvent has been entirely removed. The accompanying diagram will make this clear. The sinuous curve ABODE may represent either continuous change from <: liquid along an isothermal on decrease of volume, or it may 1891.] Some Suggestions regarding Solutions. 307 represent a similar continuous change from saturated solution to dissolved substance on increase of concentration. Mr. Aitken's experiments on the cooling of air containing water- vapour have shown us that it is possible to realise a portion of the curve AB ; the phenomenon of " boiling with bumping " constitutes a practical realisation of a portion of the curve DE ; and we may profitably inquire what conditions determine such unstable states with solvent and solvent. Regarding the portion of the curve AB, I think that no reasonable doubt can be entertained. It precisely corresponds to the condition of supersaturation. In the liquid-gas curve, the volume is decreased constant temperature without separation of liquid ; in the solvent- jlvent curve the concentration is increased without separation of the jlvents. Dr. Nicol has shown that it is possible to dissolve dry >dium sulphate in a saturated solution of sodium sulphate to a very jnsiderablo extent without inducing crystallisation ; and here we we a realisation of the unstable portion of the curve AB. In the 3-liquid curve pressure falls with formation of a shower of drops ; the solvent-solvent curve crystallisation ensues, and the solvents jparate. The phenomena are, however, not completely analogous ; ae complete analogy would be if the temperature were so low that the substance in the liquid-gas couple were to separate in. the solid, lot in the liquid, state. This, so far as I am aware, has not been tperiinentally realised, but one sees no reason why it should not be sible. I have some hesitation in offering speculations as to the state of itter at the portion of the continuous curve DE. It may be that corresponds to a syrupy or viscous state. Cane-sugar at a loderate temperature dissolves water ; indeed it is possible to obtain solution of 1 per cent, of water in molten cane-sugar. And such a alution, if quickly cooled, remains a syrup. But it can be induced crystallise by the presence of crystals. Thus, in such a mixture if sugar and water, a few grains of crystalline sugar cause the fhole mass to crystallise, and water saturated with sugar and sugar sparate into two layers. Here, again, a complete analogy fails us, it is a solid which separates. As we know nothing of the osmotic ssure of a syrup, the analogy is a defective one ; but it is probable that a dilute solution of sugar would pass continuously into a syrup :>f pure sugar by evaporation of the solvent, and analogy would lead the supposition that the syrup coincides with the unstable state of le liquid. I would, therefore, offer the analogy between the syrupy md the supercooled states as a tentative one ; it lacks foundation in 3th cases. One point remains to be mentioned. I have for the past nine lonths, in conjunction with Mr. Edgar Perman, been determining 806 Mr. F. E. Beddard. On a new Form of [Mar. the adiabatic relations for liquid and gaseous ether: the rise pressure and temperature when volume is 'decreased without escaj of heat. It is obvious that similar relations are determinable for solutions, and probably with much greater facility. M. Alexeeff has made some measurements which might be utilised for this purpose ; but they are far too few in number, and, moreover, the necessary- data as regards osmotic pressure are wholly wanting. It would be possible by a series of differential experiments to ascertain the evolution of heat on increasing concentration, and so to arrive at a knowledge of the speci6c heats of the solution at constant osmotic pressure, corresponding to the idea of specific heat at constant pressure ; and also of specific heats at constant concentration, corre- sponding to specific heats at constant volume. I do not know whether such researches would yield as accurate results as those wej are at present carrying out, but they are at least well worthy of attention. 1 1. " Preliminary Notice of a New Form of Excretory Organs it an Oligochsetous Annelid.". By FRANK E. BKDDARD, M. Prosector of the Zoological Society. Communicated Professor E. RAY LANKESTER, M.A., LL.D., F.R.J Received February 19, 1891. So far as our knowledge of the Oligochaeta goes at present, excretory system appears to consist either of one or more pairs separate nephridia in each segment, or of a diffuse, irregularlj arranged system of tubules with numerous external pores upon segment, and often with numerous ccelomic funnels in each segment there may or may not be a connexion between the tubes of success^ segments. All the aquatic Oligochaeta have nephridia of the kind ; a large number of the terrestrial Oligochaeta have nephridia the second kind ; there is occasionally in the latter forms a specialie tion of part of the diffuse nephridial system into a pair of Is nephridia ; these species connect the two extremes. But in all tht Worms the nephridia are contained in the ccelom, though some of tl connecting branches may be retroperitoneal ; the ducts which lead the exterior may branch in the thickness of the body wall, but tl does not seem to be any extensive ramification and anastomosis of the tubes in the muscular layers of the body wall.* I have recently found a remarkably different arrangement of the nephridia in an Annelid belonging to a new genus of Eudrilidae. This family is chiefly noteworthy on account of the remarkable modi- » ' Quart. Journ. Micr. Sci.,' vol. 28, PI. XM, fig. 1, n, and fig. 2. 1891.] Excretory Organs in an OUgoehcetou* Annelid. 309 tications of the reproductive organs, and the present genus is no exception to the rule in that particular ; but it shows a further peculiarity in the structure of the nephridia ; the arrangement of these organs in the clitellar region of the body is unique amon^ Annelids, and is to a certain extent suggestive of the condition of the organs supposed to be nephridia in certain Nematoidea. Throughout the body generally, as in other Eudrilids, the nephridia are paired ; in the genital region I was struck, on dissecting the worms, by the apparent absence of nephridia. Sections through the body wall in this region show that the longitudinal and transverse muscular layers are traversed by a system of peculiar canals not at all like nephridia in appearance. These canals are not mere clefts between the muscular fibres, such as Kiikenthal has described in his paper " Ueber die lymphoiden Zellen der Anneliden ;"* such lymph spaces I have found a good many Oligochaeta, but they never possess a definite wall. On ic contrary, the canals which I describe here have a definite darkly- lining wall, with nuclei here and there. They resemble the blood sssels very closely, and might easily be confounded with them. These vessels are arranged in a longitudinal and a transverse series tith numerous branches and interconnexions. The longitudinal luscles are imbedded in a nearly homogeneous, transparent, connec- ive tissue, which is of some thickness between the peritoneal 3ithelium and where the muscular fibres end. It is in the latter 3t of tissue that the four principal longitudinal trunks run. corre- jnding in position to a line connecting the four successive pairs of stae ; there appear to be smaller longitudinal trunks, but the four icipal ones run through several segments without a break ; these jgitudinal trunks are connected with a metamerically repeated stem of transverse vessels ; these lie between the transverse and )ngitudiiial muscular coats, and appear to run right round the body, ley are of considerable calibre, but not so wide as the longitudinal iks ; I could not detect any ciliation anywhere, and their walls extremely thin. They give off numerous branches, which traverse ie body wall in every direction, and form a finer meshwork of ibules ; some of the branches run towards the epidermis, and Ithough I could not detect in transverse sections the actual orifices, account of the fineness of the tubes, I could make out at frequent sints a slight modification of the epidermis which seemed to arrespond to an external pore. Upon fragments of the chitinous cuticle being stripped off and tamined with a high magnifying power, the orifices were quite plain, ley were much smaller than the nephridiopores of Pericliceta, but )t so minute as to be confounded with the pores of the gland cells the epidermis. * ' Jenaische Zeitsclir. f. Naturw.,' vol. 18 (1885), p. 310. f 310 ><>rii '>;•./.'//.-• hi 'in Oligochafotu Ann>'/i, increased excitability, greater diffusion of stimuli with diminished power and definiteness of movement. Thus slight stimuli in the frog produce movement more readily in the poisoned than in the normal condition, bat the movement, instead of being limited to one limb, vigorous and steady, is diffused over several limbs, feeble and tremulous or jerking. In frogs, the tremors or jerking always occur on attempted move- ment, and sometimes, to a slight extent, when at rest. If the done be large, they are succeeded by paralysis. Absorption of the drug is slow and irregular, and it may cause local rigor of the muscles. The heart remains long irritable. Haloid radicals do not modify the action of benzene to the same extent as they do that of ammonia, but they do so in somewhat the same direction as the authors described in their former paper on thU subject. Monochlorobenzene affects the spinal cord more than benzene, causing spasm and rapid diminution of reflex. It also weakens the circulation, but does not seem to affect motor nerves or muscles more than benzene. " The bromo- and iodo-compounds have a more power- ful paralysing action on the cerebrum than benzene and chloi benzene, and the compound of iodine with benzene, like its compounc with ammonia, appears to have a special tendency to paralyse motoi nerves, muscles, and cerebral reflexes, and to depress the heart. Heat accelerated and cold retarded the action of the substances. The substitution of alcohol radicals for hydrogen in bcnzem appears to modify its action in much the same way as one woulc expect from a general consideration of the properties of the alcohc group, which, as a rule, have a sedative action on the nervoi system. The compounds of benzene with alcohol radicals produce U tremor, less hyperaesthesia, and greater lethargy than the halog compounds. The circulation is little affected by them. They hai little action on muscle or nerve, but act more powerfully on the nei than on the muscle. Their action appears to be more fleeting ttu that of the halogen compounds. Trimethylbenzene (mesitylene) more active than methyl- or dimethyl-benzene. In poisoning dimethylbenzene a curious increase of reflex action was observe after it had almost gone, and spontaneous movement had quit gone. Substitution of hydrogen by hydroxyl increases the tendency convulsions. These are due to the action of the substances on spinal cord and not on the cerebrum ; they occur independently voluntary movement, except when the dose is very small, and tinne almost unchanged after destruction of the cerebrum. Slight tremor may occur before destruction of the cerebrum, but it is greatly masked by the powerful contractions referred to. The position of the 1891.] Chemical Constitution and Physiological Action. 313 hydroxyl groups in the di- and tri-oxybenzenes affects their physio- logical action. Para-oxybenzene (resorcin) has an action similar in kind, but weaker than the ortho- and meta-oxybenzenes (hydro- quinone and pyrocatechin). The most characteristic feature of its action is the occurrence, at nearly regular intervals, of clonic con- vulsions, which never become tonic or tetanic, and are due to the action of the drug on the cord. They are abolished by the action of curare, even in a limb protected by ligature from the action of both poisons. Strychnine produces tetanic spasm in a frog poisoned by resorcin, if the symptoms due to the latter drug are only imperfectly developed, but does not do so if the clonic spasms have become well marked. Large doses cause paralysis, destroying the irritability and conducting power of the cord. Trioxybenzene (1:2: 3-pyrogallol) produces more lethargy than resorcin, less tremor o» movement, and little spontaneous jerking. Its power to produce immediate symptoms the frog is only one-fourth or one-fifth that of* resorcin, but it is almost exactly equal to it in its ultimate lethal power: Amidobenzene (anilin) may be regarded either as benzene with one ydrogen replaced by amidogen, NH3, or as ammonia in which one ydrogen is replaced by phenyl, C6H5. In conformity with this con- titution, the symptoms produced by it differ from those of benzene d resemble those of ammonia in the tendency to more violent pasm and to greater paralysis of muscle and nerve. They differ •om those of ammonia, in the fact that the convulsions never assume he form of true tetanus, the tetanic spasm which the ammonia group ould produce being broken up, so to speak, by the action of the henyl. With the exception of the hydroxyl compounds, amido- enzene causes the most rapid occurrence of motor phenomena. It roduces great tremor after a spring and active incoordinate move- ent, but no tonic spasm. Nitrobenzene causes lethargy with creasing tremor on movement, and early abolition of reflex action. The effect of several benzene compounds on reflex time was bserved. The oxybenzenes could not be tested on account of the mtaneous jerks to which they give rise. The general action is to use a lengthening in the reflex time, but a primary shortening was bserved frequently in the case of chlorobenzene, slightly in methyl-, imethyl-, and ethyl-benzene. In producing muscular rigor, chlorobenzene is considerably more werful than the bromo- or iodo-compound, and is intermediate in •ength between methyl- and dimethyl-benzene. Of the methyl- nzeiies, the methyl- is the strongest, the dimethyl- next, and the tri- ethyl- weakest. The action of these compounds on muscles is, therefore, inversely to the amount of methyl substituted for hydrogen, in the benzene molecule. Ethyl benzene is nearly the same strength methyl, and stronger than the dimethyl or trimethyl com- Y 2 314 Profs. J. T. Cash and W. R. DunMun. [Mar. 5, pounds. Amidobenzene and nitrobenzene are less active in producing rigor. The respiration is considerably and early affected in warm-blooded animals (cats) by benzene and its compounds. There is usually a primary acceleration, followed by slowing. The "heart appeared to stop before the respiration in poisoning by benzene and its haloid compounds, by ethylbenzene, amidobenzene, and nitrobenzene, whilst respiration usually failed before the heart, or nearly at the same time, in poisoning by the methylbenzenes and oxy benzenes. The first effect of the benzene compounds on the pulse or on blood pressure is usually a quickening of the pulse and a rise in the pres- sure. This is followed by slowing of the pulse and fall of the pressure. In their preliminary communication in 1887, the authors directed attention to the curious resemblance between the tremor caused by benzene and some other aromatic substances in frogs and the symptoms of disseminated sclerosis in man. In the present paper, they point out also the likeness between the violent slapping move- ments caused in the frog by some of the haloid compounds of benzene, as well as by amidobenzene, and the symptoms of locomotor ataxy in man. IV. " The Physiological Action of the Paraffinic Nitrites con- sidered in connexion with their Chemical Constitution. Part I. The Action of the Paraffinic Nitrites on Blood Pressure." By J. THEODORE CASH, M.D., F.R.S., Professor of Materia Medica in the University of Aberdeen, and WYNDHAM R. DUNSTAN, M. A., Professor of Chemistry to the Pharmaceutical Society of Great Britain. Received March 4, 189L (Abstract.) •CONTENTS. I. Introductory. II. Description of the Nitrites and of the processes used in preparing them. III. Action of Anijl Nitrite. Description of the Method of Investigation. IV. Action of other Paraffinic Nitrites contrasted with that of Amyl Nitrite. V. General Summary of Blood Pressure Experiments. VI. General Consideration of the Modification «f Nitrite-action induced by Splanchnic Stimulation and Section. VII. Action of Nitrites on the Human Subject. The present investigation was commenced three years ago, in order to throw further light on the mode of action of the paraffin ic nitrites when introduced into the animal organism, and particularly to deter-. 1891.] The Physiological Action of the Paraffinic Nitrites. 315 mine in what manner this action is conditioned by the different chemical constitution of the various nitrites employed. Since the chemical constitution of these compounds is well established, and their molecules are comparatively simple in structure, and, moreover, as their principal physiological effects are capable of accurate quanti- tative study, it seemed likely that the inquiry would furnish valuable pharmacological results. Our knowledge of the physiological behaviour of the organic nitrites has been almost wholly derived from the study of amyl nitrite, which has been observed to produce a similar but far greater effect than its lower homologue ethyl nitrite, whose action, however, has not hitherto been so closely examined as that of the amyl com- pound. Unfortunately it seems certain that the results which have been obtained with amyl nitrite are to a large extent vitiated by the circumstance that, as a rule, insufficient pains have been taken to procure the nitrite in a chemically pure state, whilst, in addition, the usual mode of administration has been such that it is impossible to determine exactly how much of the compound has actually been inhaled. It is believed that both these sources of error have been obviated in the present research. The exact composition of each substance was known, and a special apparatus was devised for ensuring the inhala- tion without loss of a definite amount of nitrite, through the trachea in animals, and through the nostrils in the human subject. In this, the first part of the communication, an account is given of the principal work which has already been done on this subject, and this is followed by a brief description of the method by which the litrites have been prepared and their purity ascertained. The physiological actions which have been made the subject of special study are those on blood pressure, pulse, and respiration, whilst the 'action on striated muscular fibre has also been fully examined. The present paper deals almost entirely with the action of various nitrites on blood pressure, and with the special apparatus used in studying it. A subsequent paper will have reference to the action of these same nitrites in producing contraction of striated muscle, and will conclude with a discussion of the whole of our results, both in their chemical and physiological aspects. The nitrites have been prepared by the reaction of the correspond- ing alcohol, previously purified, with sodium nitrite in bhe presence of dilute acid. This has proved to constitute a satisfactory plan of pre- paring the entire series of nitrites with which we have worked. The liquid nitrites, after having been thoroughly washed and dried, were repeatedly distilled, in some cases under reduced pressure, until a liquid boiling at a constant temperature was obtained. Proof that the liquids thus obtained had the composition of the required nitrites 316 Profs. J. T. Cash and W. K. Dunstan. [Mar. 5, was furnished by analysis. The nitrites which we have prepared are those of methyl, ethyl, primary propyl, secondary propyl, primary butyl, secondary butyl, tertiary butyl, isobutyl, «-amyl, /9-amyl, and tertiary amyl. Certain- of these nitrites were prepared by us for the first time, while of those which had already been described some have been found to. possess different physical properties to those usually ascribed to them. For the purposes of administration, a known volume of each nitrite was taken. The relative density of each substance having been previously determined, the weight corresponding to the volume taken was readily calculated, and from this was ascertained the amount of the active nitrite group (N03) present. The apparatus for recording alterations in blood pressure consisted of a mercurial manometer writing upon a slowly rotating drum, and a Pick's kymograph writing upon a more rapidly revolving Balzac's cylinder. These manometers could be employed together or sepa- rately, but, as a rule, when pressure and number of pulsations only were being observed, both were kept open. The advantage of the arrangement is that a considerable period of time is represented by a short lineal movement on a small drum, whilst on the quick one the pulse can be reckoned and the course of the rapidly occurring varia- tions of pressure studied. Respiration was recorded on a registering Marey's tauibour attached to a double tambour placed on the thorax of the animal. An electrical signal, in connexion with a key and Darnell's cell, was placed beneath the point recording the blood pressure in order to mark the time of administration of nitrite. In cases where vagus, splanchnic, -or sciatic stimulation was employed, a double key -admitted the faradic current from the secondary coil of a du Bois- Raymond's indactorium-to the electrodes on which the nerve rested, while at the same time it closed the signal circuit indi- cating the length of stimulation. The following represents the course of the nitrite administration. The blood pressure being steady, the clockwork of the quick drum was started so as to bring it up to full speed before the cylinder was made -to rotate by sere-wing up the friction wheel. The nitrite was then introduced into the side tube of the inhaler ; an arrange- ment of valves permitted inspiration only to take place through this tube. The cylinder was started, ariti after a sufficient record of the pulse and respiration for the time being had been recorded, the nitrite was administered, the time of administration being recorded. A sufficient time having elapsed for inhalation, the air-tube of the inhaler was opened, the quick drum being permitted to run as long .as was necessary for the purpose of recording the changes in pulse and pressure. During- the recovery of pressure an occasional record of pulse and respiration was taken on the quick drum, corresponding marks being made on the slowly revolving cylinder. 1891. J T/ie Physiological Action of tie Paraffinic Nitrites. 317 It is well established that small doses of amyl nitrite canse a fall of blood pressure, resulting chiefly, if not entirely, from a powerful dilatation of the arterioles, reducing peripheral resistance to a great extent. Two distinct views have been advanced as to the cause of the dilatation. Filehne maintains that his experimental results de- monstrate the dilatation to be due, not to a local action on the walls of the vessels, but to the direct action of the nitrite on the vaso-motor centres. On the other hand, Brunton, and also Mayer and Priedrich, believe they have shown that the dilatation is the result of a direct action on the walls of the vessel, and is independent of any effect on the central nervous system. After discussing the experiments of Filehne, Branton, and Mayer, an account is given of the experiments made by the authors to eluci- date this question. These were made with cats, but control experi- ments with rabbits afforded the same results. In the first series the head of the animal was entirely cut off from the circulation, yet inha- lation of pure amyl nitrite (-sV-b. c.c.) caused a rapid fall of pressure, the lowest point reached exactly corresponding with that noticed in an immediately preceding experiment, in which the head was included in the circulation. In the second series all the arteries passing to the head were temporarily ligatured, and salt solution containing dis- solved amyl nitrite (gVth c.c.) injected through the distal end of the carotid artery, one of the jugular veins being opened so as to admit of an escape of blood and hinder the production of a possibly abnormal intravasealar tension in the brain. The same effect was constantly observed ; the blood pressure rose, and not until the clamps were removed did the fall of pressure of the usual character occur, ["here is thus no indication of the characteristic nitrite effect, so long is the vessels are ligatured, although the nitrite must have passed to the medulla oblongata by vascular anastomosis, and therefore to the chief vaso-motor centre. By the injection of Berlin blue, it was demonstrated that access could be gained to the medulla through this channel. The conclusion that the nitrite effect is the result of an 3tion on the vessels, and not on the central nervous system, was con- firmed by observations on the effect produced by nitrites after splanchnic stimulation and section. Splanchnotomy is attended with a considerable reduction of pressure, and if nitrite be admi- nistered when this is at its minimum, a further redaction occurs, which, however, is not so great as that observed before section. But if administration of nitrite be delayed until the occurrence of one of the temporary elevations of pressure which are observed from time to time, the fall of pressure closely approximates to that produced before splanchnotomy. Simultaneous splanchnic stimulation and nitrite inhalation also cause a normal fall in pressure. In experiments with the human subject, an accurate record was 318 Physiological Action of the Parajfinic Nitrites. [Mar. 5, taken of the pulse-rate, after inhalation of a known quantity of nitrite. A mask inhaler was specially devised, so as to avoid loss of substance daring inhalation. It consisted of a conical metal box covering the month, and fitting accurately on the bridge of the nose by the aid of a hollow rubber border, which could be distended by injection of air. It is provided with three tubes opening out of a common trunk in the front of the mask ; one of these was not fur- nished with any valve, but the two lateral tubes had each one valve, opening inwards and outwards respectively. The tube intended for the inspiration of nitrite had a continuation of india-rubber, in the middle of which a glass bulb was inserted for the reception of the nitrite. Spring clamps were placed on either side of the bulb. The mask having been adjusted to the face, and respiration being regular through the valvular tube, the drum was started at full speed so as to record the normal pulse rate, and the inhalation tube was opened by removing the clamps on either side of the bulb at the same time as the interior tube was closed. The time of inhalation was recorded by a signal marker. There is a considerable variation on the part of individuals to nitrite effect, the acceleration of the pulse in the case of those of neurotic tendency being much greater, and the time of its con- tinuance much less than in that of a lymphatic subject. The order of activity (extent of acceleration) for various nitrites deduced from a large number of experiments is (1) a-amyl ; (2) /J-amyl ; (3) iso- butyl ; (4) secondary butyl ; (5) primary butyl ; (6) secondary propyl ; (7) primary propyl; (8) ethyl ; (9) methyl. The action of each paraffinic nitrite has been closely contrasted with that of amyl nitrite. The results may be broadly summarised as follows : — All the nitrites examined produce, in whatever way administered, a reduction of blood pressure, variable, however, according to the compound employed in its extent and in its progress, as well as in the ensuing recovery. A pulse acceleration usually accompanies and succeeds the fall upon inhalation, the extent of inhalation varying in the case of indi- vidual nitrites. The acceleration is less upon intra-vascnlar injection, especially intra-arterial injection, than when administration is by inhalation ; a distinct retardation of pulse is frequently produced by the former method, especially by carotid injection. The extent of acceleration appears to be less in the case of cats than in the human subject. The respiration is affected (1) temporarily during and immediately subsequent to inhalation, in various degrees by the different nitrites, and (2) permanently by the repeated administrations of the same or different nitrites. 1891.] On the Structure and Development of Dentine. 319 As regards the principal effect, reduction of blood pressure, the activity (extent of reduction) of the various nitrites takes the follow- ing order when equal volumes are administered to animals by inha- lation : — (1) secondary propyl ; (2) tertiary butyl ; (3) secondary butyl, (4) isobutyl, nearly equal ; (5) tertiary amyl ; (6) «-amyl, (7) /3-amyl, nearly equal ; (8) methyl ; (9) butyl ; (10) ethyl ; (11) propyl. The order is somewhat modified when the nitrites are given by intra-vascular injection. When the duration of the sub-normal pressure is considered, the order is nearly the reverse of that given above, the effect of methyl nitrite being the last, and that of secondary propyl nitrite one of the first, to disappear. In contrasting the results of the measurement of pulse acceleration produced by these nitrites, it is noticed that their activity in thia respect does not follow the same order as that in reducing blood pressure, the amyl nitrites in particular occupying a higher position in the table. The causes of these differences will be considered in the second part of this paper, in conjunction with a discussion of the relation of the chemical con- stitution of the nitrites to the physiological effects now described, and also to those produced in striated muscle, a description of which will form part of the subsequent communication. In order that the physiological data might be placed on an abso- lutely satisfactory basis for chemical discussion, we determined at the commencement of last year to repeat all the more important physio- logical experiments. This necessitated the labour of preparing fresh specimens of the nitrites. The results of these confirmatory experi- ments have been in every respect satisfactory, since they differed in no important respect from those previously obtained. The chemical part of this enquiry has been conducted in the Research Laboratory of the Pharmaceutical Society,, in London, whilst the physiological experiments have been made in the Pharma- logical Laboratory of the University of Aberdeen.. Some Points in the Structure and Development of Dentine." By J. HOWARD MUMMERY. Communicated by 0. S. TOMES, F.R.S. Received February 7, 189L (Abstract.) e purpose of the present paper is to show that there are appear- s in dentine which suggest that it is formed by a connective tissue calcification, and that the process is more closely analogous to the formation of bone than has usually been supposed. The varied theories held as to the structure and development of 320 On the Structure and Development of Dentine. [Mar. 5 dentine are partly due to the difficulties met with in the investigatioi of this tissue, soft and hard parts haying to be retained in theii natural relations to each other. Decalrification of the dentine b acids has been resorted to, a mode of preparing microscopical object) for study which is open to many objections. Sections cut by process recommended by Dr. L. A. Weil, of Munich, exhibit th natural relations of pulp and tooth without the necessity of resortin] to decalcification. Fresh specimens are fixed in sublimate, passe* through gradually increasing strengths -of spirit to absolute alcohol and slowly impregnated with a solution of desiccated balsam ii chloroform, dried with more balsam over a water-bath, and cut dowi on a stone with water. The present investigation was undertake] •with the aid of this process, controlled by the examination of othe specimens cut by the more ordinary methods. Processes or bundles of fibres are seen, incorporated on the on side with the dentine, and on the other with the connective tissu stroma of the pulp; some of the bundles give evidence of partia calcification, reminding one of similar appearances in the calcificatioi of membrane bone. Cells are seen included in the bundles and lyin parallel to their course ; these cells, it is concluded, form together wit the odontoblasts the formative cells of the dentine, the calcification c which tissue should be looked upon as in part, at least, a secretio rather than a conversion process, the cells secreting a material whic calcifies along the lines of and among the connective tissue fibrei the cells themselves not being converted into dentine matrix. Theg appearances are seen in the rapidly forming dentine of a growin tooth, as well as in more fully developed specimens. An examinatio of other Mammalian teeth reveals similar appearances. The dentin of the incisor of the Rat (Mug decumanus) shows with great distincl ness the incorporation of the connective tissue fibres with the dentine and there is a marked striation of the dentine near the pulp cavity, parallel with these fibres. The ivory of the Elephant's tusk shows the same relation of connective tissue to formed dentine. VMO- dentine exhibits a very well defined connective tissue layer sur- rounding the pulp. This layer has hitherto been looked upon as consisting of odontoblasts, but this tissue shows no nuclei, and has the characters of a layer of flattened connective tissue fibres — a layer of nucleated cells in close apposition to the dentine, probably being the real odontoblasts of vaso-dentine. 1891.] Presents. 321 Presents, March 5, 1891. Transactions. Baltimore : — Johns Hopkins University. Circulars. Vol. X. No. 85. 4to. Baltimore 1891. The University. Berlin : — Gesellschaft fur Erdkunde. Verhandlungen. 1891. No. 1. 8vo. Berlin; Zeitschrift. 1891. No. 1. 8vo. Berlin. The Society. Buda-Pest : — Konigl. Ungar. Geologische Anstalt. Mittheilungen. Bd. VIII. Heft 9. Bd. IX. Heft. 2. 8vo. Budapest 1890 ; Foldtani Kozlony. Kotet XX. Fttzet 5-12. Svo. Budapest 1890. The Institute. Kew : — Royal Gardens. Bulletin of Miscellaneous Information. No. 50, and Appendix 1, 1891. 8vo. London. The Director. jeipsic: — Konigl. Sachs. Gesellschaft der "Wissenschaften. Ab- handlungen. Bd. XII. No. 2. 8vo. Leipzig 1891. The Society. jondon : — British Museum. Catalogue of Printed Books. Leval- Licska, Lictardus-Lindemayr. Folio. London 1891. The Trustees. British Astronomical Association. Journal. Vol. I. No. 4. 8vo. London 1891. The Association, tanchester : — Literary and Philosophical Society. Memoirs and Proceedings. Vol. IV. Nos. 1-2. 8vo. Manchester 1891. The Society. Tew Haven : — Connecticut Academy of Arts and Sciences. Trans- actions. Vol. VIII. Part 1. 8vo. New Haven 1890. The Academy. 3t. Petersburg : — Societe Physico-Chimique Busse. Eclipse Totale du 7/19 Aout, 1887. Rapports des Expeditions de la Societe [Russian]. 8vo. St. Petersburg 1889., Prof. Egoroff. Stockholm : — Kongl. Vetenskaps-Akademie. Ofversigt. Arg. 47. No. 10. 8vo. Stockholm 1890. The Academy. Butschli (0.) Weitere Mittheilungen iiber die Structur des Proto- plasmas. 8vo. Heidelberg 1890. The Author. Chauveau (A.), For. Mem. R.S. Le Travail Musculaire et 1'Energie qu'il represente. The Author. Clark (L.), F.R.S. A Dictionary of Metric and other Useful Measures. 8vo. London 1891. The Author. Clifford (H. E.) Harcourt's Pentane Standard Lamp. 8vo. U [Boston] 1890. With one other Excerpt in 8vo. The Author. 322 Presents. Collins (E.) The Magnetic Circuit: a Theoretical Discussion, in eluding a Formula for Magnetism in Soft Iron. 8vo. [Boston 1889. TheAutho Cross (C. R.) and H. E. Hayes. On the Influence of the Stre of the Magnet in a Magneto Telephone Receiver. 8 [Boston'] 1890. The Autho: Downing (A. M. W.) The Star-Places of the Second Melbo % General Catalogue for 1880. 8vo. London 1890. The Auth Dupont (E.) Notice sur Laurent-Gnillaume de Koninck. 8 Brwwlles 1891. The Auth Eastman (J. R.) The Progress of Meteoric Astronomy in Ameri 8vo. Washington 1890. The Auth< Eliot (J.) On the Occasional Inversion of the Temperature Re t ions between the Hills and Plains of Northern India. 8 Calcutta 1890. The Au Fritsche (H.) On Chronology and the Construction of the Calen with Special Regard to the Chinese Computation of Time pared with the European. 8vo. St. Petersburg 1886. The Au Goppelsroeder (F.) Ueber Fenerbestattung : Vortrag. 8vo. M\ hausen i.E. 1850. The Ant Jacobi (C. G. J.) Gesammelte Werke. Bd. V. 4to. Berlin 1890. Konigl. Preuss. Akademie der Wissenscha: Johnson (G.), F.R.S. Medical Lectures and Essays. 8vo. 1887 ; An Essay on Asphyxia (Apnoea). 8vo. London 1889. ~ The Author. Kolliker (A.), For. Mem. R.S. Ueber die erste Entwicklnng der Nervi olfactorii. 8vo. Wiirzburg 1890. With one other Excerpt in 8vo. The Author. Lawes (Sir J. B.), F.R.S. Memoranda of the Origin, Plan, and Results of the Field and other Experiments at Rothamsted. June, 1890. 4to. London. Sir J. B. Lawes. Maiden (J. H.) Wattles and Wattle-Barks. 8vo. Sydney 1890. Technological Museum, Sydney, Mensbrngghe (G. Van der) Sur la Propriete Caracteristique de la Surface commune a deux Liquides sonmis a lenr Affinite mutueile. Partie 1-2. 8vo. Bruzelles 1890. The Author. Puffer (W. L.) Data and Plots of various Incandescent Lamps, together with an Improved Method of Testing. Parts 1-2. 8vo. [Boston] 1890. The Author. Roscoe (Sir H. E.), F.R.S., and C. Schorlemmer, F.R.S. A Treatise on Chemistry. Vol. III. 8vo, London 1891. The Authors. Rouvier (J.) Identite de la Dengue et de la Grippe-Influenza. 8vo. Paris 1890. The Author. On the Plasticity of an Ice Ciystal. 323 Rowland (H. A.) and C. T. Hutchinson. On the Electromagnetic Effect of Convection Currents. 8vo. [London] 1889. The Authors. Butley (F.) On Composite Sphernlites in Obsidian, from Hot Springs near Little Lake, California. 8vo. [London] 1890. The Author. Sang (E.) Exhibition of Curves produced by the Vibration of Straight Wires. 8vo. [London] 1889. The Author. Slater (J. S.) Description of an Improved Armillary Sphere. 8vo. [London'] 1890. The Author, .ckermann (A.) Index to the Literature of Thermodynamics. 8vo. Washington 1890. The Author. March 12, 1891, Sir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. The Right Hon. Lord Hannen, whose certificate had been sus- pended as required by the Statutes, was balloted far and elected a Fellow of the Society. The Presents received were laid on the table, and thanks ordered for them. Kie following Papers were read : — On the Plasticity of an Ice Crystal." By tlie late J. C. McOoNNEL, M.A. Communicated by R. T, GLAZEBROOK, :F.R.S. Received January 24, 1891. Two years ago, in the ' Proceedings of the Royal Society,' was pub- ished an account of some experiments on t"he plasticity of ice made >y Mr. Kidd and myself. We proved the oft-repeated statement, that lacier ice is not plastic under tension, to be erroneous, and showed bat any ordinary bar of ice composed of several crystals will yield ontinuously either to pressure or tension. But we found that a bar at out of a single crystal with its length at right angles to the optic sis showed no signs of continuous stretching even under half the peaking tension, and other experiments convinced us that an ice •ystal will not change its shape under either tension or pressure ^plied at right angles to its optic axis. These results seemed to ;nder it highly probable that an ice crystal was not in any way astic, and though after the winter was over we wished we had varied ir experiments more, yet we quite expected that further investiga- 324 Mr. J. C. McCoiinel. [Mar. 12, tion would only have corroborated the perfect " brittleness " of single crystal. Since our paper was written, my attention has been called to passage in Professor James Thomson's masterly article on " Tbi Lowering of the Melting Point of Ice by Distorting Stress (' Phil. Trans.,' 1849), in which he expresses the opinion that crystals whether of ice or other substances, are not plastic. If we reject the idea of internal distortion of the crystals, we an driven to the conclusion that the observed plasticity must be due t< some action at the interfaces, whereby the crystals alter their shapi sufficiently to allow them to alter their relative positions. As to th< nature of the action, various suggestions occurred to me. Jama Thomson explained the plasticity of ice at 0° C. by supposing the to melt at those interfaces where the stress was great, and the libe water, after flowing to points where the stress was small, to solidify. This might be extended to low temperatures by supposi a certain quantity of water to be kept in the liquid state by pressure of residual impurities. But the process would be en mously retarded by the constant necessity for the distribution of being equalised by diffusion. Again, it is not clear how a bar of i during this process would be able to resist a tension considera greater than the pressure of the atmosphere. With more probabili we may suppose one crystal to grow at the expense of another owinj to the stresses and strains on the contiguous parts being differe: Though the stresses were the same, the strains might be dift'eren owing to seolotropic elasticity. But the elasticities are not likely be very different in different directions, so for a very small exte: of the bar we should expect considerable movement of the interfi There is, however, nothing to prevent the stresses being different The tension in any direction parallel to the interface might be greater in one crystal than in the other. The migration of matter from one crystal to another under less stress would probably in almost all cases be accompanied by yielding to the external force producing the stresses. But in this case the effect would be very indirect, and again we might look for large movement of the interfaces. Some such speculations had occupied my mind last autumn, and it was with considerable curiosity that I began experiments in Decem- ber on the puzzling question of the real cause of the plasticity of ice. I took a bar of ice consisting of half a dozen crystals, made a draw- ing under the polariscope of the relative position of the interfaces, and then set up the bar with the ends supported and a weight hung from the middle. After two days, it had bent a good deal, yet, under the polariscope, I could detect no material change in the position of the interfaces. One crystal, however, had completely chang< appearance. It now strongly reminded me of a piece of unaunealed 1891.] On the PlasticAtij of an Ice Crystal 325 glass. There were two centres of colour encircled by irregular rings, and these remained much the same when the two faces through which the light passed were rubbed quite flat and the other crystals cut away. There could be no doubt that this crystal had suffered some- thing more than mere elastic distortion. The next experiment was very instructive. A thin slip of ice, being a single crystal, was subjected to bending stress as before, and left for several hours. It apparently bent very quickly, for after a few hours it was found crescent shaped, and luckily unbroken, lying at the bottom of the box. The optic axis was bent, and, though its change of direction was rapid where the bend was sharp, there appeared to be no break in continuity. On the other hand, the long narrow bubbles, which were originally no doubt parallel to each other and perpendicular to the slip, were still parallel to each other throughout. In fact, as I noted at the time, the crystal behaved as if it consisted of an infinite number of indefinitely thin sheets of paper, normal to the optic axis, attached to each other by some viscous substance which allowed one to slide over the next with great diffi- culty. This comparison proved to be the key to the whole question of the plasticity of a crystal of ice. Further experiment showed that if a bar of ice consisting of a single crystal with the axis perpendicular to two of the side faces was subjected to bending stress, it would bend freely in the plane of the axis either at or below the freezing point, but not at all in a plane perpendicular to it. In the bent crystal the optic axis in any part was normal to the bent faces in that part. But any series of lines drawn in the substance of the ice which were originally parallel to the iptic axis and to each other remained parallel to each other, though oot, of course, to the optic axis. This was evidenced by the position )f long narrow bubbles which frequently form at right angles to the )lanes of freezing, and also by the end faces of the bar remaining parallel to each other. When the optic axis was longitudinal, the bar >ent indeed, but not very readily, and the general behaviour was nore obscure. Still, this case, too, was in satisfactory agreement vith the analogy mentioned above. Let us state this analogy more fully. The sheets of paper offer no esistance to bending, but utterly refuse to stretch except, of course, lastically. Initially they are plane and perpendicular to the optic xis, and, after they have been deformed by bending, the optic axis jit ny point is still normal to the sheet at that point. They are of niform thickness, whence it easily follows that the directions of the tic axis in any crystal form a series of straight, though not parallel, 326 Mr. J. C. McConnel. [Mar. 12, Detailed Account of the Experiments. The first two experiments have been sufficiently described already. The place of experiment was a north room in the Buol Hotel, Davos. A box without a lid was placed on a wooden table, and across the top of this box were laid two pieces of wood, which served to support the ends of the bar of ice. From the middle of the bar was suspended a weight with a loop of thick string. In the bottom of the box, but at the other end, i.e., about a foot from the idr and 6 inches below it, was placed a registering thermometer of the Sii pattern. Over the whole was put a thick wooden cover. As there was nothing inside the cover of great capacity for heat, I believe that any variation of the temperature of the ice was nearly simul- taneously felt by the thermometer. This thermometer, which was used throughout, was divided into Fahrenheit degrees ; its correction at freezing-point was tested both before and after the experiments. The error did not exceed $° F. At 6° F. I compared it with a spirit thermometer which had been verified at Kew ; it read |° F. too high; j These errors are negligible in the present work. Exp. 3. — A bucket of water left in the ice room over night wai found in the morning covered with ice about 15 mm. thick, consisting of several crystals. From this I sawed out a bar and planed it smooth and straight. The breadth was 10 mm. ; the depth, 9 mm. The bar contained many long bubbles in a vertical position, the middle of it was one crystal with the axis nearly vertical. T two ends of the bar were composed of many crystals. A weight 1'29 kilograms was applied from 11.20 A.M. to 8.30 P.M. on Decem 14. During this time the maximum temperature was — 2*"8 C. the minimum, — 5°'6 C. ; and the mean, about — 3°'6 C. The bar taken the shape of the diagram, fig. 1, which is copied from a t: Fio. 1. made soon after the experiment. The bends at the points indicated by a and 6 were more decided in the bar than in the trace. The exact position of the supports was not noted at the time, but they certainly did not extend right up to the bends at a and 6. The fact that the two end pieces are still nearly in line suggests that the end surfaces 1891.] On the Plasticity of an Ice Crystal. 327 of the middle crystal are in the same position as before the bending. The question immediately suggested itself whether the bend was due to a limited number of layers sliding over each other by finite amounts, or to a true shearing strain. I examined the surfaces of the bubbles very carefully with a magnifying glass, and could find no trace of pro- jecting edges or " faults," so I concluded it was a true shear. My )lariscope was the same as was used two years ago. Light from the white paper A, fig. 2, was reflected by the three FIG. 2. lates of glass, B, upwards through the Nicol C, and then the ice was lid on the glass stage E, or held in the closed hand. D was lined nth black velvet. This simple apparatus served its purpose excel- itly, and it was seldom that I wished for a more elaborate apparatus rith convergent light. The bent bar under this polariscope was rand to have the optic axis as nearly as I could tsll normal to the VOL. XLIX. z 8ft) Mr. J. C. McConnel. [M.ir. 12. bent faces throughout. If the black centre was near tbe middle of one half, the sharp bend was crowded with narrow coloured bands which moved slowly along as the bar was tilted, till as each band reached the straight piece beyond the bend it moved rapidly and broadened out. The movement of the bands across the bend, though slow, was quite regular, so the direction of the optic axis changed quickly but not per salt tint. Exp. 4. — A similar arrangement. The bar was all one crystal except the parts actually on the supports. The optic axis was transverse, but horizontal. Depth, 9'5 mm. ; breadth, 10 mm. ; supports, 75 mm. apart. The weight of 1'29 kilos, was applied over 42 hours from 4.15 P.M. on December 15 to 10.35 A.M. on December 17. The minimum temperature was — 7°'8 C., the maximum — l°'l C., the mean about -3°'3 C. Decided evaporation had taken place ; the edges of the bar wore rounded :and the string which had stuck to the bar was raised on ridges. The greater part of the bar was 8^ mm. deep, 9 mm. broad. In comparing the traces taken before and after the experiment I could find no bending. It certainly did not amount to half a milli- metre. The traces were taken by laying the bar on a sheet of paper and following the upper and lower edges with a pencil. Exp. 5. — The same bar, turned so as to put the optic axis vertical, bent rapidly. Depth 8f mm., breadth 8j mm. Distance between supports 73mm. The weight of 0'62 kilo, was applied from 11.10 A.M. to 9.5 P.M. on December 17. The minimum temperature was — 4°'4 C., the maxi- mum — 1°'7 C., mean about — 3°'0. The depression of the middle J measured on the trace was about 4'4 mm., which had taken place \ in 10 hours. Assuming that in Experiment 4 the depression was less then 0'5 mm., the bending of the bar in the new position must ha\ •• been at least thirty-seven times as fast. It is true the depth and breadth were slightly less, but the weight was less than half as great. The results of 'Exp. 3 as to bubbles and optic axis were confirmed. Exp. 6. — A bar with the axis longitudinal. I obtained a large lump of thick ice from the Davos lake, and from this cut a CD CD 1> 00 O to oo t— J> 1 rl 1 1 1 1 1 1 1 1 1 1 1 1 s, 5 N ! rH rH "M CO H g CD t- co CO t> 00 Oi 0 t> t* CD M 1 1 1 1 I 1 1 1 1 1 1 o P. 9 to j £ CO O "? 00 ^ _ rH ••# O ,2 C74 rH o ** o O rH 6 M ID .« lO tO lO ja tt. 00 | •P 5 rH OS ^ s to 0 s> "* (N rH 0 0 0 § • O CD iN CO 1> co O . 1 r^ CD r1 9 00 8 oo to 8 o CO IM to (N rH O s h D O 0 o o 0 O 1 o o o. O 0 1 1 E E s rH rH rH S & 9 00. co os J8 0 rfl 0 0 rH rH rH rH rH ^ o. o o M oo os oo to to co- - oo CO rH rg 'S 3 § 0 (M Cvl 5Q rH rH 0 00 o (M 0 0 1 5 0 O 0 0 O O 1 + O 0 : o 0 0 1 1 a co to CD to 10 » vt eo CD =- S CO (M (M CO co co 1 4- eq IN f 1. rH 0 1 1 « o s s . . . a 1 t D | O rH eo o co co co co •* to to os to to co to co co to to CO IM %% 00 tO Tf rH CO CO SJ os © d «® rH rH O rH rH rH rH (M N O rH H g t» rH 1 1 7 53 m J 1 s = rH 3 8 to 04 II 71 - 8 1 .2 c 0 0 $ & 1 1 1 i eo eo w I-H 00 ec rH d ® S — .2 9 9 * s 0 0 M 1 1 pparent tension. W3 00 0 0 1 1 % z * 0 • • 1-1 S H o o . eo 10 oo 4- n 2 ^ rH 3 i •-s PC, 591.] On the Plasticity of an Ice Crystal. 3'55 Into this matter I enter more fully below. The indicated rise between 12.59 and 2.3 P.M. is, I feel sure, simply lue to a misreading. Whenever the weight was altered the appa- itus was unavoidably disturbed, so I had to take an entirely fresh reading of the pointer. Generally this only differed by fractions of a millimetre from the previous reading, but in the case in point it was nearly 6 mm. greater. The ice showed an inconvenient tendency to slip backwards on the iron plate, thus bringing the end of the pointer forwards till it almost touched the edge of the slit. The ice had to be pushed forwards three or four times during the experiment. Of course a fresh reading was taken after each such displacement, so that no error resulted. This trouble was caused doubtless by the plate not being accurately level. In subsequent experiments I was more successful in avoiding it. Exp. 11. — I desired to establish with, the more delicate system measurement that the plasticity is inappreciable when the bending 3ss is applied at right angles to the axis. I cut a bar, all one crystal, from the bath ice, and planed it so that the upper and lower surfaces were as accurately as possible parallel to the optic axis. In the polariscope, when the middle of the black cross was in the middle of the bar, the two faces were equally inclined to the lines of sight. I then set up the apparatus in the usual way. The results are seen in the annexed table (p. 334). f It will be seen that the pointer indicated a rise of the stirrup amounting in the 21^ hours to 0'29 mm. As was before mentioned, the stirrup was slightly roughed to prevent it from slipping, so at first it would make contact with the bar at only a few points. Evaporation would help to extend the contact to large surfaces, and admit of a slight movement of the stirrup relatively to the ice. Thus the experiment was not as satisfactory as could be wished. It is possible that a very slight depression of the bar might be masked by this effect of evaporation. But even supposing that the rate of real depression was twice as great as that of the apparent elevation, viz., O0043 mm. per hour, it would still be very small compared with the rates of the next experiment. I am at any rate entitled to say that within the limits of error of experiment there is only one kind of plasticity in an ice crystal, viz., that due to the sliding layers at right angles to the optic axis. It is probable that the same source of error was active in other experiments, but in them the effect would be almost negligible. Exp. 12. — The same bar was turned on its side so that the optic cis was vertical. 3f> Mr. J. (J. McCounel. [Mar. 12 e CO rH 9 "-P O 00 94 t- CO t» rH 1, O 94 * 1(5 -H t» US 09 94 04 rH eo •* to 01 eo eo 1- - 3 1 1 1 1 1 M 1 1 1 1 1 1 1 1 i £ p. a _s> = 1 *0 **. « 94 O rH 10 ••£> 00 ? 99 ,. S 't 00 o •* CO 94 04 rH 94 CO ia •o co ro CO H C8 1 1 1 1 MM 1 1 1 1 1 1 1 I •3 cs C5 p ' a JB O O o cc o o * B 0 1— 1 O rH o - f a • 04 rH j -? rH O i-l 00 O co >o 1- -* 94 O O5 CO «O 30 0 0 00 rH S — / i -- to 1 fe 0 O o o O rH rH rH o o PH o o o z. 3 1 1 1 1 a •3 £ CO *>. eo eo t^ at •-£> » ?4 »O iM 00 00 t^ OS O O 9H rH.i-H rH r?S 09 04 04 r-i 11 M 3 O 94 00 O O O O b o • O •# o o - a Real \li-ll-MII. 8£ O 94 C4 IH m »» o o 94 94 rH 94 •*-* 1— 1 rH O O rH i— 1 CO ^ 94 O O O O O O O O o o 1 t O O \ o o 1 e • 1§ C5 CO OS o eo ii Ot> *-•* i- i'- - .'-. • oo DO 94 00 94 04 0.^ 1 1 1 1 4 j H a sal .- «« O •< h ^ 3 H • •: i> i - rH IO rH ~4 00 94 94 rH O «OOO^? 04 CO ^ US rH IQ >p ^ rH ^ 5r? •* rH — r i- rH CO rH rH 0 O O i-l FH 94 94 C4 94 94 94 CO co eo eo CO •* •* 00 00 00 O OS C» ,_; rH rH 04 • .3 5 CM 1891.] On the Plasticity of an fee Crystal. 337 We first notice that the plasticity exists down to — 14°'4. At this emperature the bending was slow, but this was due in great part to the fact that it came at the beginning, and the bar was as usual. The rapid growth of plasticity, independently of the temperature, is shown by the rate of 0'59 mm. per hour at a mean temperature of — 5°'6, being raised in less than two hours to 1*18 mm. at — 6°'l. The tend- ency to recover when the weight is removed is shown three times over in the table. As might be expected, it soon becomes very slow, and in that case after twelve hours, when the recovery amounts to 0'72 mm., it has probably stopped altogether. In the fall of rate from 1-89 at -1°7 to 1-18 at -6°'l and O745 at -13°, in spite of the natural tendency for the rate to rise, we seem to have a real effect of temperature. After 8.38, the cigar box had to be left open as the pointer had almost reached the lid of the box, and so the subsequent tem- peratures are unreliable. I imagine that the change from Ofc85 to 0*745 was due to a fall of temperature. At the beginning of Exp. 11 the bar measured 14 mm. by 12'3 mm., •which was reduced at the end of Exp. 12 to 13 mm. by 10'8 mm. The evaporation had been rather more rapid just at the bend of the bar. This was owing, I believe, to the circulation of air through the ole by which the string passed out. I measured the total depression on the trace as 2'6 mm. As mea- red by the pointer it is 2'45. The agreement is as good as could be expected. Exp. 13. — In this experiment I used a thicker bar and tried a variety of weights. The bar was only just small enough to go into the stirrup. (See Table IV, next page.) The stiffness of the bar in the first three hours is surprising. Exp. 14. — In all the experiments hitherto on bars composed of single crystals it happened that the optic axis had been vertical when the ice was formed, so that the planes of freezing coincided with the sliding layers. I fully believed that this coincidence was merely acci- dental, and what happened in Exp. 8 had confirmed this idea, but I thought it desirable to have a more direct proof. So I cut a piece out of a good large crystal in the ice, found on the surface of the water in the bucket, in which the optic axis was not Vertical. When the bar was put in position the planes of free/ing were vertical and parallel to the length, and the optic axis was normal to the length and inclined at about 50° to the vertical. The bar was about 8 mm. square, and the distance between the supports was 51 mm. Under a weight of 0*62 kilo, in 4 hours 28 minutes at a mean tem- perature of — 40>4 (the maximum — 1°'4) it bent downwards about 4 mm. There was a large lateral bend, which made the vertical bend Sy difficult to measure. 1 the sliding layers had been necessarily the same as the planes of • • 338 Mr. J. C. HcCennel. r. 12, OO O OS o X 1-1 o d 1(9 lO o ^ X X o £. o M e m 1 1 1 1 1 1 rH 1 1 1 1 b s | OS OS rH 04 ceo t. 1 _ cs H S co co o ^ t~ X o o o 10 •a 1 1 1 1 1 1 1 1 1 1 i c 0 •s o rH OS $ OS S OS lO rH OS B B sr 0 " o o rH o 0 0 B J: tj J la § lO OS 10 S lO OS 'S "* -H i cs lO rH t» « Cl >) o M to • • 0 S to - Ll o o o O o o O o O o 9 c 1 £ (N rH OS •* iO $ §0 S S S ? 5 rS J2 CO rH rH O O rH o O) o 0 J •UOI88 gC S S II i rH I CM rH IO ?! PC B 0 O o o O O 0 o O o •o *. ! C c : S i '*3 00 OS IN OS rH OS X lO co 71 i CO IO 01 rH CO X CO t> ^ CD 1.0. •4 X x ej os OS OS rH H x .a 5 to 1891.] On the Plasticity of an Ice Crystal. 339 freezing, this bar should not have bent at all. If, however, the sliding layers are necessarily perpendicular to the optic axis, this bar should have been free to bend on the plane of the optic axis, but not in the perpendicular plane. In the experiment the plane of the total bend contained the optic axis. Thus the experiment was decisive. In attempting to discover the manner in which the rate of the molecules sliding over each other depends on the driving force, we are met by the difficulty that the rate of depression depends on at least three other circumstances, the temperature, the previous history of the bar, and the irregularity of the stresses and strains within the bar. The second is to some extent avoided by only considering the rates observed immediately before and immediately after the change of weight. The third is probably not very important. In the following table are collected all the instances which occurred, with the attendant changes of temperature. The changes of rate are not so great as the square, but greater than the first power of the changes of the applied force. In the table may be seen the amount of correspondence with the power f . The two most glaring discrepancies are in the second Table Y. Change mean temperature. Change of weight in kilos, per sq. cm. /Old forceXf. Change of rate in mm. per hour. Ratio of rates. \New force/ - 7'2to -6-7 1-47 to 0-85 0-442 0-172 to 0-0735 0-427 -10'Oto -15-0 054 to 0-174 0-182 0-058 to 0-0058 0-100 -15-0 to- 8-9 0 -174 to 1 '47 24-6 0-0058 to 0-410 70-7 - 5-Oto- 6-7 0'91 to 0-47 0-373 0-160 to 0-054 0-338 - 6-7to- 7'5 0-47 to 0-91 2-70 0-054 to 0-159 2-95 - 7-5to- 8-0 0-91 to 1-38 1-87 0-159 to 0-297 1-87 - 8-9to-10-0 1-38 to 0-91 0-537 0-323 to 0-197 0-610 -10-0 to- 7-8 0-91 to 0-225 0-122 0-197 to 0-0225 0-114 - 7'8 to- 6-1 0 -225 to 0 -91 8-15 0 -0225 to 0 -28 12-4 - 6 -1 to - 5-9 0-91 to 1-38 1-72 0-28 to 0-57 2-04 and third instances given in the table, when the power 2 is well satisfied. But these discrepancies may be largely, if not entirely, explained by the great change of temperature. Without elevating the statement to the rank of a law, we may say that fairly close agreement with the observed facts is obtained by supposing that when the molecules of ice slide on each other the cube of the friction varies the square of the velocity. In attempting to pass from the rate at which the centre of a loaded sinks to the coefficient of plasticity, we meet with considerable difficulties, and shall have to content ourselves with a rough approxi- B;ion. It might well be thought that the problem of a rectangular ^ " Mr. .!.('. M« -Gunnel. [Mar. li>, ( htstic bar, supported at either end and loaded in the middle, had been fully worked out. But this does not. appear to be Hhe case.y The ordinary elementary treatment makes the gigantic assumption ., that plane cross-sections of the unbent bar remain plane, and that thet lateral contraction or expansion of elementary strips parallel to the ength of the bar under longitudinal pulls or thrusts are the same ns in 2 free space. It does not consider any shearing stresses or strains. It is true that Rankine ('Applied Mechanics,' p. 338), assuming Hie results of this method, proceeds to find an expression for the shearing stress. He makes it proportional to a9 — a:2, where the origin is at the centre of the bar, the axis of x is drawn upwards, and 2a is the depth of the bar. But this expression is inconsistent with the general equations of an elastic solid. St. Tenant's solution of thej bending of a bar, given in Thomson and Tait's ' Natural Philosophy,*' postulates equal and opposite couples applied at the two ends, so that < the bending moment is uniform throughout. The importance of the absence of this uniformity is not trifling but fundamental, for in onrl case everything depends on the shears, and in St. Venant's solution! there are no shears. I fancy that I see my way to obtaining the complete solution in the form of infinite series. But, since it ceases to be applicable the} moment plastic strains take place, it would only enable us to deter- 1 mine the inUial stresses, and this would hardly justify the insertion i here of such a long investigation. The following simple but imperfect treatment must suffice. Let ns first define the coefficient of plasticity. Take a rectangular element* with two faces normal to the optic axis, and let these faces be sub- jected to a tangential force U per unit of area in opposite directions, parallel to another pair of faces. Fio. 8. U Then if the rate of growth of two of the angles, or rate of dimi- nution of the other two be denoted by dx/dt, the coefficient of plas- ticity p may be defind by the equation 1891.] On the Plasticity of an Ice Crystal. FIG. 9. 341 i The bar is represented in fig. 9, with a weight W hanging from the middle. The length between the supports is I, the breadth b, the depth d. U is the force per unit area which acts on a small vertical interface in a vertical direction, and when U is positive the matter to the left of the interface is urged upwards. The force per unit area on a horizontal interface in a direction parallel to the length of the bar is necessarily the same, and is also denoted by U. Consider the equilibrium of the part of the bar to the right of any cross section PP'. It is urged upwards at the support by a force equal to ^W ; therefore, if we neglect its weight, the total vertical force on the section PP' is also £W. KU be the average of U over the section bdU = iW (2). annot be constant over the section, for it necessarily vanishes at the upper and lower surfaces of the bar. The average shear over any cross section being the same, except that the sign suddenly changes at the middle of the bar, it is reasonable to suppose that the same amount of plastic shearing strain would take place between the layers perpendicular to the optic axis at every cross section. This condition makes the bar bend sharply when the weight is applied, and keeps the two halves straight. In tke earlier experiments, where the bending was considerable, this form was observed before its cause had been perceived. For this form to be assumed without elastic strain, the plastic strain must be the same, not merely in corre- sponding points of different cross sections, but also throughout each cross section itself, and, in fact, throughout the entire half of the bar. But as we have seen, the shearing stress must vanish at both the upper and lower surfaces. Doubtless the truth is that the state of shearing strain is nearly uniform throughout the bar, except close to the surface, where it rapidly diminishes to zero. Probably in these regions the elastic strains are very great, and quite different from what they are elsewhere. 342 On the Plasticity of an Ice Crystal. FIG. 10. [Mar. 12 Let « be the depression of the middle of the bar, \ the angle either half makes with the horizontal, small, and We have s = -v. 2* When x > IVfdt (3). This gives the coefficient of plasticity in terms of the unsupported, length of the bar, the weight per unit area of cross section, and the? observed rate of depression. We have employed equation (2)j which is strictly applicable only when the bar is straight and hoi zontal. But, in the cases to which we have to apply these results, \ ^ so small that the error is negligible. It was hardly worth whil calculating the numerical value of p, especially as it has been shoi to depend on the temperature, on the value of U nearly, and on the previous history of the bar. But the above investigation assist any one in estimating, as far as can be done from my expei ments, the rate of distortion of an ice crystal in any given case. In several cases in the experiments, after a heavy weight was removed, a slight gradual unbending of the bar took place. At first I thought this a mere consequence of the irregular elastic strains ou the bar, the parts most severely strained gradually bending back the rest. But the magnitude of the recovery seems, on closer examination, to put this explanation out of the question, and I have now little doubt that it is a true molecular effect. In Exp. 12, after a stress of 1*69 kilos, per sq. cm. had been removed, the middle of the bar rose O'Ol 04 cm. in four hours. Accord- ing to an experiment by Moseley (' Phil. Trans.,' 1871), Young'* modulus for ice is 92,700 kilos, per sq. cm. Hence, if we neglect the effect of the plastic strains in one bar of ice, the elastic depres- sion under 2'5 kilos, should have been 0'00138 cm., less than oue- seventh of the recovery observed. The permanent or plastic strains in Moseley 's bar are considerable, so that the deduced value of Young's modulus may be too great. Bevan, also by flexure of baw 1891.] Temperature and the Refractive Index of Liquids. 343 of ice, found the value 60,000. Rensch (« Nature,' vol. 21, p. 504), by experimenting on the sonorous vibrations of rectangular plates of ice, found Young's modulus to be 23,632 kilos, per sq. cm. (this last method seems rather dangerous). In attempting to devise an imagi- nary system of strains sufficiently great to render such a recovery as 0"! cm. possible, we are soon brought up by the breaking tension of ice. Direct experiments by Moseley give this as 7 or 8 kilos, per sq. cm., and Kidd and myself found it in one case to be 8'3 kilos, per sq. cm., but the fact that the bar of ice in Exp. (11) bore the •weight of 2'5 kilos, before any plastic strains had taken place brings it out greater than 15*5 kilos, per sq. cm., and the bar in Exp. (13) was able to endure an even greater stress. A similar discrepancy has been noticed in the case of cast iron (Rankine, ' App. Mechanics,' §297). • Using the latitude given by the uncertain values of the constants the utmost, I have not been able to devise any system of elastic strains which could possibly make the bar rise O'Ol cm., and there is no reason to suppose that the unknown system of strains actually occurring in the experiments would be exceptionally well adapted to such a purpose. I conclude, then, that we have to deal with a real tendency of the forcibly displaced sliding layers to slide back. The rate of recovery, rapid at first, soon falls off. Thus in Exp. (10) there was a recovery of 0'046 mm. in the first 18 minutes, and only 0-021 in the next 58. In Exp. (15) after 0'014 in the first 11 minutes, and the same in the next 31, the motion probably came to a standstill after a few hours, practically, if not absolutely. Thus in Exp. (12) the bar was left with no weight on for 12 hours, and the recovery only 0'072 mm. [Mr. McConnel died suddenly at Davos while engaged on the fore- going paper, which has been printed from his rough copy with some few alterations of no great importance. I thought it better to do this than to attempt to edit it; though I know from his last letters to me that the author would have himself, if he had lived, been able to leave it in a more finished state than that in which it now appears. -R. T. GK] " On the Effect of Temperature upon the Refractive Index of certain Liquids." By W. CASSIE, M.A. Comnrnnicated by Professor J. J. THOMSON, F.R.S. Received February 19, 1891. n my paper " On the Effect of Temperature on the Specific Inductive Capacity of a Dielectric" ('Phil. Trans.,' A, 1890), the OL. XLiX. 2 A 344 Temperature and the Refractive Index of Liquids. [Mar. 12, values obtained for the temperature-variation of specific inductive capacity of four of the liquid dielectrics investigated were compared with the corresponding values of the temperature-variation of refrac- tive index found by Messrs. Dale and Gladstone.* And the relations between these two quantities, though not in accordance with Clerk Maxwell's electromagnetic theory of light, were near enough to make it worth while to try whether the divergence from theory might not be due to differences in composition. Accordingly I measured the rate of change of refractive index with temperature for the same specimens of the liquids as were used in the electrical experiments. In the case of olive oil, however, the original supply could not be found. The results obtained are very close to Messrs. Dale and Gladstone's for those of the liquids they had examined, and for the others the optical effect shows a similar divergence from Maxwell's theoretical relation. And considering the enormous diffe- rence in the rapidity of the electrical and optical effects, this is not surprising. The change of refractive index was measured by observing with spectrometer the minimum deviation of the D lines for a bottle pri filled with the liquid. The observations were taken at two tempe: tnres, viz., that of the room, 16° or 17° C., and a higher temperatu about 40° C., obtained by heating the prism and its contents in warm water. The results are shown in the following table, the last column i giving the values of Messrs. Dale and Gladstone : — 1 Turpentine Kate of change per degree centigrade of r Specific inductive capacity. Refractive index. Refractive index (D and G). -•0012 - -004 -•006 - -0006 -•0014 + '0023 -•0003 -•0006 - -0002 - -00037 - -00043 - -00017 - -00033 - -00018 -•00037 -•00043 Carbon bisulphide Glycerine Benzoline Benzine Paraffin In the case of glass, the change of refractive index with temj ture was found by Stefanf to be 0'0000023 per degree centigrade quantity of quite a different order from 0'002, the rate of change > specific inductive capacity. And in view of the influence of the time of charging, even when extremely short, upon the specific indue » Result* collected in Watts's ' Diet, of Chem.,' vol. 3. t ' Wien., Akad. Sitzber.,' vol. 63, Abth. 2. 1891.] On Sensitisers for Rays of Low Ref ranglbility. 345 capacity of glass revealed by Professor J. J. Thomson's experiments,* this is only what might be expected. ,, " On the Bisulphite Compounds of Alizarin- blue and Coerulin as Sensitisers for Rays of Low Refrangibility." By GEORGE HIGGS. Communicated by LORD RAYLEIGH, Sec. R.S. Received February 19, 1891. The determination of the relative wave-lengths of the Fraunhofer lines, by photographing all the orders of spectra given by any particular grating, includes certain subjects which present more or less difficulty, and that of selecting or producing a dye-bath adapted to the requirements of the two or more orders comprising the subject is intimately connected with that of the choice of absorbing media. Having been engaged for some time in investigations of this nature, I had occasion, during the summer of 1889, to require an impression of the 2nd order, about X 3300, contiguous with that of the red end of the 1st order, and finding that the ordinate of an actinic curve for a plate immersed in a very dilute alcoholic ammoniacal solution of cyanin (1 : 30,000), reduced to about one-fourth of that for an unpre- pared plate, I abandoned its use for this purpose. The results appeared to be unaffected by the addition of quinine. Subsequently, induline, ccerulin, alizarin-blue, and the bisulphite compounds of the two latter were used. When obtained in a state of sufficient purity the alizarin-blue S leaves little or nothing to be desired, for, whilst possessing, in a high degree, sensitising properties for rays throughout the region comprised between X 6200 and 8000, it does not, like cyanin, lower the sensitiveness to the violet and ultra-violet. The following is one of the processes I employed in the prepara- tion of the dye-stuff in a pure state : — To a saturated solution of sodium bisulphite in a mortar is added alizarin-blue paste. This is disintegrated with a pestle, and poured into a glass vessel capable of holding an additional quantity of sodium bisulphite, in all 10 parts of the paste to 20 parts of bisulphite, and another 10 parts of water. The vessel is well stoppered, set aside in a cool place for five or six weeks, and shaken daily, but left undis- bed during the last eight or ten days, he solution is decanted, filtered, and treated with alcohol, to pre- itate the greater portion of the remaining sodium bisulphite. 50 pavts of water are now added with a sufficiency of sodium chloride >rm a concentrated solution. Again set aside in an open-inouthed * ' Roj. Soc. Proc.,' vol. 46. 2 A 2 346 On Sensitisers for Rays of Low Refrangibility. [Mar. 12, glass jar, covered with bibulous paper, for seven or eight days, a deposition of the dye in a crystalline state, together with sulphite of calcium, will take place, which latter, owing to its insolubility in water, may be removed by filtration. The alizarin-blue S is separated from any unaltered substamv in the original stoppered vessel by solution, and added to the brine, now purified from lime salts, and once more set aside to crystallise, the final purification being effected in a beaker containing alcohol and a small percentage of water to remove the last traces of sodium chloride, collecting the crystals on a filter-paper and drying at ordinary temperatures. The needle-shaped crystals are of a deep-red. Dilute solutions am of a pale sherry colour, changing, with the addition of a few drops of ammonia, to a green, which immediately gives way to magenta aifl every shade of purple, till oxidation is complete, when it assumes a blue colour, the absorption spectrum of which is continuous and strongest in the least refrangible end, presenting the appearance of extending into the infra-red. Plates immersed in a solution containing 1 : 10,000 and 1 per cenK of ammonia give the most perfect results the day after preparation, but rapidly deteriorate unless kept quite dry. With a slit T Badische Anilin- und Soda-Fabrik, Ludwigshafen, who hold the patent rights for the manufacture of alizarin-blue S. It is hoped this company may be induced to manufacture this substance free from the minute crystallisable impurities which render it unsuitable for use in investigations of such delicate nature. * P.S. — With a low sun at times screens were found unnecessary. Colonel Water-house, who has also employed alizarin-blue (' Photographic News,' 1889), states that Schiendl and Eder failed to recognise the sensitiveness of this substance to the red, and considers that red or yellow screens are required t produce the full effect. 1891.] Properties of Metals in relation to the Periodic Law. 347 IV. " On Certain Properties of Metals considered in Relation to the Periodic Law." By W. C. ROBERT s-AusTEN, C.B., F.R.S. Received March 12, 1891. In a previous paper published in the ' Philosophical Transactions ' (1888, A, pp. 339—349), the effect of about 0'2 per cent, of im- purities on the mechanical properties of gold was examined, the results of the experiments showing that metals which diminish its tenacity and extensibility have high atomic volumes, while those which increase these properties have either the same atomic volume as gold or a lower one. The behaviour of aluminium and of lithium appeared to be somewhat exceptional. Gold contaminated with 0'2 per cent, of aluminium should, if the theory set forth in the paper be correct, have a tensile strength of about 7 tons per square inch ; but it was found to be capable of sustaining a load of nearly 9 tons per square inch without breaking. It became necessary, therefore, to ascertain whether the cooling of a mass of gold containing alu- minium presents any peculiarities, more especially as Osmond's* recent work leads to the conclusion that a pure metal can exist in two distinct molecular forms, and that the passage of the ordinary modification of a metal to the allotropic one may either be hastened or retarded by the presence of impurity. In order to continue the investigation, a trustworthy pyrometer LS needed, and this has fortunately been provided by the thermo- lectric -junction of platinum, and platinum with 10 per cent, of lodium, the use of which was suggested by M. Le Chatelier.f It •pears to be superior to any other of the thermo- junctions which ive previously been used, and some experiments made in 1889 tisfied me that the appliance is an extremely delicate and useful ie for temperatures between 500° and 1100° C. In a recent ;port to the Institution of Mechanical Engineers, in which details the method of calibration are embodied, I have described a suitable tngement for obtaining, by the aid of photography, autographic irves which represent the cooling or heating of masses of metal. It consists in enclosing a galvanometer of the Deprez and L'Arsonval type in a large camera ; a fixed mirror, F, being placed ilow the movable mirror, M, of the galvanometer, so that the light >m the lime cylinder, L, reflected in the mirror H, passes to both drrors, F and M, and is reflected in the direction of a fine hori- * 'Comptes Eendus,' vol. 110, 1890, p. 346. ' Journ. Iron and Steel Inst.,' L890, Part 7, p. 38. t ' Bull. Soc. Chim., Paris,' vol. 47, 1887. p. 2. ' Journal de Phjsique,' vol. 6, '•17, p. 23. 348 Prof. W. 0. Roberts-Austen. [Mar. 12, zontal slit, AB, behind which a sensitised photographic plate, C, is drawn vertically, past the slit, by means of gearing, D, driven by clockwork. The ray from the fixed mirror is interrupted periodically by the vane, E, and a beaded datum line is given which enables any irregularity in the advance of the plate to be detected. The amount of divergence from its datum line of the spot of light reflected by the movable mirror at any given moment bears a rela- tion (which can readily be found by calibration) to the temperature to which the thermo-jnnction X is heated, and variations of tempera- ture are recorded by a curve which is the resultant of the upward movement of the plate and the horizontal movement of the spot of light. The complete arrangement is shown in the diagram fig. 1. FIG. 1. The portion of the arrangement in which the thermo-junction is placed is also shown in fig. 2, which is drawn on a larger scale than fig. 1, the same letters being used in both. The thermo- junction X is inserted in a tubulure, T, of a specially constructed crucible of plumbago, c, which contains about 5 oz. of pure molten gold, and is allowed to cool down slowly inside a vessel, a, of silver 105 mm. diameter, and polished internally. The cylinder, b, is of tin plate, polished internally and blackened outside. L89L] Properties of Metals in relation to the Periodic Law. 349 FIG. 2. hotographic record of the cooling of pure gold is represented by the thicker of the dotted lines in fig. 3. The mass of gold had in this case an initial temperature of about 1250° C., which fell to 1045° C. when the mass began to solidify. The curve is approxi- mately horizontal during solidification, and throughout its entire course appears to be a perfectly normal curve of a cooling mass of metal, no points of exceptional absorption or evolution of heat, such as would occur in iron, being observable. A curve obtained in a similar way, and representing the cooling of gold with 0'5 per cent, of lead, is shown by the thin dotted line in the same figure. It is similar to the one representing the cooling of pure gold, but it will be evident that the presence of lead lowers the freezing point of gold by an amount which is found by measure- Iment to be about 7°'5 C. A very different molecular condition is, however, established by the presence of aluminium. With 0*47 per cent, of this element the true freezing point can be detected, but is nearly obliterated (fig. 3), and the mass does not become truly solid until the point marked a is reached when the temperature has fallen to 9006 C. It is of interest to ascertain how far the lowering of the freezing point of gold is in accordance with the results of Baoult's investiga- tions on the lowering of the freezing point of solutions. His generali- sations have been tested in the case of solutions of metals in metals •with low melting points (tin, lead, and bismuth), in an admirable series of experiments by Heycock and Neville.* In order to calculate the lowering of the freezing point of gold produced by one atom of the added element to 100 atoms of the solvent, which has been the usual method of stating such results, it is necessary to know the latent * ' Journ. Chem. Soc.,' vol. 55, 1889, p. 666 ; vol. 57, 1890, pp. 376 and 656. ' 350 Prof. W. C. Roberts-Austen. FIG. 3. \\ [Mar. 12, PURE GOLD GOLD V,,TH 0-47^ ALUMINIUM. GOLD *MTH o-5 or LFAD heat of fusion of gold, and this had not been determined, probabl because the accurate measurement of the latent and specific heats metals with high melting points, such as gold, presents many mo difficulties than the determinations of similar constants for bodi having low melting points. Violle* found the specific heat of platinum at different tempera- tures by heating a piece of the metal in a specially constructed mufti the temperature being simultaneously determined by means of porcelain air- thermometer. The temperature of the metal being known, he plunged it into a calorimeter, and calculated from the data he obtained the mean specific heat of platinum between the extreme temperatures of the experiment. By making many experiments at different temperatures, he was able to deduce the specific heat of platinum at any point within the range, and he found that it regularly increased with the temperature. The data, thus afforded, enabled him to obtain the freezing point of platinum by transferring metal just after solidification into the calorimeter. Further, by pouring metal just before its solidification into water, it was easy to determine the total amount of heat evolved during cooling. Hence, knowing * ' Comptes Benclus,' vol. 85, 1877, pp. 543—540. 1891.] Properties of Metals in relation to the Periodic Law. 351 the amount of heat evolved by the mass after it had become solid, and deducting this amount from the total heat transferred to the water by the melted platinum, he obtained the latent heat of fusion of the metal. He also determined* the specific heat and melting point (1045° C.) in the case of gold, but he does not appear to have ascertained what is the latent heat of fusion of the precious metal. The following experiments were therefore made, in order to afford a basis for cal- culating the theoretical lowering of the freezing point of gold which a given addition of impurity should produce. A calorimeter of polished silver, 10*5 cm. diameter, and 15'5 cm, high, was supported upon three points of cork within a bright metallic vessel, blackened externally, and constituting an air-jacket. The amount of water employed varied from 800 to 1088 grams. The stirrer was a thin sheet of mica, mounted upon a silver wire, bent at its lower end into the form of a hoop ; the mica also served to catch the gold poured into the water. In experiments E to I, the stirring was effected by silver vanes, of a form suggested by Professor Riicker, actuated by a small electromotor. Quantities of very pure gold, varying from 68 to 123 grams, were melted in a 11 clay crucible and poured into the calorimeter, his portion of the manipulation was performed by my assistant, r. Groves, whose long experience in melting gold enabled him to select the latest moment before solidification at which the gold could be poured. In Experiments A and B and E to I, the temperature of the molten mass was measured, by the aid of the thermo-junction previously described, which was placed directly in the molten gold, up to the moment of pouring, and it is believed that the temperature the mass was known to within 10° C. t the end of each experiment, the gold poured into the calori- eter was carefully collected and weighed. The thermometer used was a very sensitive one with fixed zero, and made by Hicks, of Hatton Garden; it could easily be read to 0°'02 C. The depth of water employed was sufficient to prevent the evolution of steam, and none was observed to escape in any of the experiments recorded. The calculations are as follows : — t P = weight of water in calorimeter. p!d = water equivalent of calorimeter. j92c2 = ,, „ thermometer. p = weight of gold employed. c = average specific heat of gold (Violle). t = initial temperature of the molten gold. T = „ „ water. ti = final temperature of the water. * ' Comptes Rendus,' vol. 89, 1879, pp. 702-703; 92, 1881, pp. 886-8. 352 Prof. W. C. Roberts-Austen. [Mar. 12, The total quantity of heat carried to the calorimeter by p grams of gold consists of the amount of heat which was required to raise the temperature of the metal to its melting point, plus the amount actually required to melt it ; or -T) = pc (t-tj +p\ where X is the latent heat of fusion of gold required ; Taking, therefore, 16*3 as the latent heat of fusion of gold, and proceeding to find the lowering c0 of the freezing point, due to the presence of an impurity, Ota c& = ~ > V where 0 = freezing point of gold, from absolute zero, ta = osmotic pressure in dynes, p = density of the solvent, X = latent heat of fusion of the solvent in dynes. Inserting values 1040 + 273 (1 013 xlffx 22-3x1300) *a - 1 X 19-6x273 p P* 16-3 x 41-6 xlO6 1313x1013x22-3x1300 19-6 x 16-3 x 41-6 xlO»x 273 = 10°-6 C. Experiments are in progress with a view to ascertain whether the mean specific heat of very pure gold is the same as that found by Violle, for there is every reason to believe that the presence of im- purity has great influence upon this constant. A few measure- ments already made would seem to indicate that his result is low, and this is important, because a slight difference in the specific heat will have a material effect upon the latent heat of fusion, and con- sequently on the theoretical atomic fall in the freezing point produced by aluminium. In order to ascertain whether aluminium would give the normal lowering of the freezing point (10° '6 for each atom present in 100 atoms of gold) a crucible, fitted with a tubulure, as already described, was taken, and 130 grams of very pure gold wM melted in it. The crucible was then placed over the thermo-j unc- tion, and allowed to cool, the freezing point of the metal it contained L891.] Properties of Metals in relation to the Periodic Law. 353 a. H O o 1 Remarks. 1 Solidification had just begun. 16*33. Mean of the nine ex- periments. ^ CO 1^ rH O5 CC 00 O >0 IN CO CD 1>- CO CD CD IN cp CO 4O t^ •^l O 00 co CD \a O N 00 t— V T? ITS rH •* O 10 00 rH i-l 00 CD IN 05 fr- Tjl 10 J> 1> 10 oo os cJ ,* 00 -? OS • O5 CO CO J> g rH IN O rH 1ft CO CO IN O5 O rH rH IN CO •* s^ o # # O O O O O O 1O 10 O o o o V. v - IN < ) h r -^ i IN 00 rH 1O I>

I-H rH 9 CO '~- *& ' C rH 9 1^ O5 »O N t> O O rH i— 1 co co CD co co co CO CD CO IN '•'I "- * G4 I ^ co CO CO CO 10 o m in co co CD CD CO Pi Iffl O t> 1> rH J> CO 8O cc oo oo o co o oo 00 00 OS 00 O oo CD CD CO : : : : : : : : : ej O 05 354 Prof. W. C. Roberts-Austen. [Mar. 12, being recorded in the usual way by a curve. The gold was then re-melted, and a weighed quantity of aluminium added, the mass being stirred and the temperature of its freezing point measured and re- corded in a curve. The addition of 0'2 per cent, of aluminium produced an appreciable fall in the freezing point, but this initial fall is only indicated by a change in direction of the curve. The fall as measured upon the photographic plate is only 1 mm., which nevertheless corresponds to a difference of temperature of 7°'68 C. A further addition of 0'2 per cent, of aluminium (making 0'4 per cent.) increased the fall to 1'8 mm., corresponding to 14°'28 C. It may be urged that these measurements are small, but the observa- tions were repeated with a scale some distance from the galvano- meter, and chronographic records gave results having the same values. An experiment with gold in which 1 per cent, of aluminium was present also conGnns this ; the fall in temperature of the freezing point was in this case 33°'66 C., but there were indications that the gold, the solvent, was becoming saturated. Now 0-2 per cent, of aluminium corresponds to 2/10 x 196/27'5 = 1-42 atom per 100 atoms of gold.* Hence the fall per atom present per hundred atoms of gold = 7-68/1-42 = 5°-4C. Similarly, a percentage of 0'4 corresponds to 4/10 x 196/27'5 = 2'85 atoms per hundred of gold, and the fall per atom = 14'28/2'85 = 5°-OC. With 1 per cent, of aluminium the total fall will be due to 7*16 atoms per hundred of gold; hence the atomic fall will be 33-66/7-16 = 4°-7 C. It may be added that experiments (as yet incomplete) seem to show that lead, bismuth, silicon, and platinum cause a much greater " atomic fall " in the freezing point of gold than aluminium does. The relations of aluminium to gold would, therefore, appear to be peculiar in more ways than one. The curve (fig. 3) clearly indi that aluminium has a remarkable influence on the cooling of a of gold, and in view of this it would seem strange that calculatio: based on the atomic weight of aluminium should show that it delays the initial solidification of gold less than other elements. The com- plete solidification is, however, much retarded ; for merely stirring a mass of gold contaminated with very little aluminium reveals the fact that the added element has set up during the solidification of the mass a " pasty stage " which continues through an unusually long range of temperature. In the metallurgy of iron, aluminium is known to play an im- * 196 is the atomic weight of gold, 27*5 that of aluminium. 1891.] Properties of Metals in relation to the Periodic Law. 355 portant part, and the introduction of a small quantity of it renders it possible to cast very mild steel or even " wrought " iron into forms which are remarkable for delicacy and soundness. The mode of action of the aluminium on iron in the " mitis castings " has given rise to wide divergence of opinion, but the view that it acts by the removal of oxide, or of occluded oxygen, has gained much favour. In the case of gold, which has neither occluded oxygen nor oxide to lose, the castings of the metal with 0'2 per cent, of aluminium are also remark- ably sound, and, as experiments prove, very tenacious ; the action cf the aluminium is, therefore, probably a molecular one of much com- plexity. It may be pointed out that the presence in gold of quantities of silver which vary from O'l to 4'0 per cent, does not lower the freezing point of the mass. Messrs. Heycock and Neville, who witnessed certain of the experiments above described, inform me of the hitherto unpublished fact, observed by them, that the presence of thallium does not lower the freezing point of lead. The close concordance in both these cases between the atomic volumes of the mass of metal and the added impurity is of special interest in connexion with the generalisation given in my earlier paper and re-stated on the first page of this. Silver has the same atomic volume as gold, and if present in small quantity, produces no I effect on either its tenacity or its freezing point. Throughout these experiments gold has simply been employed for the sake of its freedom from liability to oxidation, but other metals must be studied, and it is worthy of record that Hadfield has recently shown that the parts played by aluminium and by silicon in steel are almost identical. Most of the physical properties of aluminium and silicon, in a free state, are totally different, but they possess the same atomic volume, and when they are alloyed with iron they affect it in precisely the same way. I have to express my thanks to my assistant, Mr. H. C. Jenkins, his aid in conducting these experiments. [April 20, 1891. — In the course of the investigation, it became ident that, as is the case when aluminium is alloyed with copper or >n, the addition of aluminium to gold is attended with evolution of it. The following experiment was therefore arranged, with a lew to obtain evidence on this point : — A mass of 30 grams of gold, contained in an unglazed porcelain icible, was placed in the centre of a block of firebrick and strongly teated up to well above the melting point of the metal. The thermo- junction was inserted directly in the gold, and the spot of light from te galvanometer allowed to fall in the usual way on to the sensitised late (fig. 1). A piece of cold aluminium; equal in weight to 1 per mt. of the mass of gold, was then added and rapidly stirred. The Properties of Metals and the Periodic Laic. [Mar. 12, FIG. 4. ••••••• ••••••••••••I ••••••••••••• awsasss •••••••••••••• IKSR •••• 1 «•••••••• autographic curve, from which fig. 4 was plotted, showed that the first effect of the added aluminium is, as might be expected, to lower the temperature of the gold to a point a which proved to be close to its solidifying point, 1045°; the temperature instantly rises, however, to a point &, which is 225° higher than the initial temperature of the gold. The experiment is not strictly quantitative, as the perfect admixture of the aluminium could not be ensured ; but it is probable that true combination of aluminium and gold has taken place, which would doubtless greatly affect the physical constants of the mass.] 1891.] Presents. 357 Presents, March 12, 1891. Transactions. Tokio : — Educational Society of Japan, A Short Account of the. 8vo. Tokyo 1890. The Society. Topeka : — Kansas Academy of Science. Transactions. Vol. XI. 8vo. Topeka 1889. The Academy. Toulouse : — Faculte des Sciences. Annales. Tome II. Fasc. 1-4. 4to. Paris 1888. The Faculty. Upsala : — Kongl. Vetenskaps Societet. Nova Acta. Vol. XIV. Fasc. 1. 4to. Upsalice 1890; Catalogue Methodique des Acta et Nova Acta, 1744-1889. 4to. Upsala 1889. The Society. Utrecht : — Laboratorium der Utrechtsche Hoogesohool. Onder- zoekingen, gedaan in het Physiologisch Laboratorium. Vierde Reeks. Deel I. Stuk 1. 8vo, Utrecht 1890. The Laboratory. Vienna: — Kaiserliche Akademie der Wissenschaften, Anzeiger. Jahrg. 1890. Nr. 25-27. 8vo. Wien. The Academy. K.K. Geologische Reichsanstalt. Abhandlungen. Bd. XIV. 4to. Wien 1890 ; Verhandlungen. Jahrg. 1890. Nos. 14-18. Jahrg. 1891. No. 1. 8vo. Wien. The Institute. Warwick: — Warwickshire Naturalists' and Archa3ologists' Field Club. Proceedings. Annual Report. 1889. 8vo. Warwick [1891]. The Club. Washington : — U.S. Department of Agriculture. Division of Ornithology and Mammalogy. North American Fauna. Nos. 3-4. 8vo. Washington 1890. The Department. York : — Yorkshire Philosophical Society. Annual Reports for 1853, 1855, 1857-1889. 8vo. York. The Society. Zurich: — Naturforschende Gresellschaft. Vierteljahrschrift. Jahrg. -XXXV. Nos. 1-2. 8vo. Zurich 1890. The Society. jservations and Reports. Kiel : — Commission zur Untersuchung der Deutschen Meere. Ergebnisse der Beobachtungsstationen. Jahrg. 1889. Heft 1-12. Obi. 4to. Berlin 1871 ; Atlas Deutscher Meeresalgen. Zweites Heft. Lief 1-2. Folio. Berlin 1891; Sechster Bericht fur die Jahre 1887 bis 1889. Folio. Berlin 1890. The Commission. London: — Meteorological Office. Weekly Weather Report. 1891. Nos. 6-8. 4to. London ; Appendices 1-4 to the Weekly Weather Report, 1890. 4to. London ; Summary of the Weekly Weather Report, 1890. Appendix 1. 4to. London; Quarterly 358 Presents. Observations and Reports (continued). Summary of the Weekly Weather Report, 1890. Appendix 1. 4to. London; Summary of the Observations made at the Stations included in the Daily and Weekly Weather Reports. December, 1890. 4to. London. The Office. Lyme Regis :— Rousdon Observatory. Circular of Observations. 4to. [Sheet.] 1891. Mr. C. E. Peek. Vizagapatam : — G. V. Juggarow Observatory. Results of Meteoro- logical Observations, 1889. 8vo. Calcutta 1890. The Observatory. Washington : — U.S. Naval Observatory. The American Eph- emeris and Nautical Almanac for 1893. 8vo. Washington 1890 ; Report. 1890. 8vo. Washington. The Observatory. Wellington : — Registrar- General's Office. Statistics of the Colony of New Zealand. 1889. Folio. Wellington 1890. The Office. Wisconsin: — Washburn Observatory of the University of Wis- consin. Publications. Vol. VII. Part 1. 4to. Madison 1890. The Observatory. / -Mason &Alcock. Proc Eoy.Soc. ft PTEROPLAT^IA MICRURA EXPLANATION OF PLATE 7. Fig. 1. Gravid uterus of Pteroplatcea micrura, opened by a1 longitudinal incision im its dorsal wall, with, the flaps turned back, so as to show the passage of the- large bundles of trophonemata through the spiracles into the pharyngeaL cavity of a single foetus. Fig. 2. Head and shoulders of the same foetus from the left side,, to- show the great size and the lateral position of the spiracles. EXPLANATION OF PLATE 8. Fig. 3. Distal moiety of a large trophonema from one of the spiracles, to show the superficial texture and the outstanding vein. • 14. Fig. 4. Apex of the same trophonema, to show the compound duct-openings, x 66. Fig. 5. Transverse section of a trophonema in its distal half, to show the glands in vertical section, x 120. a, artery ; V, main trunk ; and V, V, branches of vein with coagula in their lumina. is on &A- Proc.Eoy.Soc. Vol. 49.P1.8. 4 x 66 PTEROPLAT^EA MICRURA'. On the Uterine Villiform Papules of Pteroplataea micrura. 359 March 19, 1891. Mr. JOHN EVANS, D.C.L., LL.D., Treasurer and Vice-President, in the Chair. The Bight Hon. Lord Hannen was admitted into the Society. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read : — " On the Uterine Villiform Papillae of Pteroplatcea micrura, and their Relation to the Embryo, being Natural Histoiy Notes from H.M. Indian Marine Survey Steamer 'Inves- tigator,' Commander R. F. Hoskyn, R.N., Commanding. No. 22." By J. WOOD-MASON, Superintendent of the Indian Museum and Professor of Comparative Anatomy in the Medical College of Bengal, and A. ALCOCK, M.B., Surgeon. I.M.S., Surgeon-Naturalist to the Survey. Communicated by Professor M. FOSTER, Sec. R.S. Received February 24, 1891. Contents. L. Preliminary Historical Sketch. I 2. Recent Observations on the Uterine Villi of some Indian Rays. 3. The Uterus and Embryo of Pteroplatcea micrura, and the Relation of the Uterine Villiform Papillae (or Trophonemata) to the Embryo. § 1. Preliminary Historical Sketch. That in the females of several Selachioids and Batoids the mucous brane of the terminal portion of the oviduct, or uterus, is pro- ed with glandular structures which secrete an albuminous fluid tined in some way or other for the nourishment of the developing bryo is a bionomic phenomenon which has attracted the attention numerous physiologists and histologists, though, as far as we are are, it has never been fully followed out. Concerning the intra-uterine arrangements for the protection and trition of the egg or embryo among Selachians, Gegenbaur ('Grundziige der Vergleich. Auat.,' p. 875) writes : — " The terminal ivision of the oviduct of the Selachians, which has already been rationed as functioning as uteras, also differs from the rest of the VOL. XLIX. 2 B 300 Prof. Wood-Mftson and Mi. Alr.x-k. On ///• oviduct iu the nature of the mucous membrane. In many it is raised into villi. Glands are much developed. The relation of this di . of the oviduct to the egg or to the embryo that originates ther is a tolerably various one. Least intimate is it in the oviparous Selachii (Raja and Scyllium) : only furnishing the egg-case. In others (Spinax, Acanthias, Scymnus), a shell is also developed, but only for a short time, and the embryo afterwards lies free in the uterus. Here come those Selachians in which there is no longer any shell at all developed, and from this circumstance results the nutritive connexion of the foetus with the uterine wall by the intermediation of the yolk-sac." This passage, although it clearly de6nes the well-known function* of the Selachian uterine mncosa, on the one hand of secreting an egg-case, and on the other hand of forming a vascular nutritive con- nexion with the modified yolk-sac of the embryo, makes only a vague allusion to another modification of function : namely, the secretii by special uterine glands of a nutritive fluid which might be absorl or ingested by the developing embryo. Leydig also ('Handbuch der Histologie,' Ed. 1857, p. 51! describes the vascular uterine villi of Acanthias, Spinax, Scynu and Trygon, though without discussing their relation to the egg to the embryo. He says : — " In the Selachians the mucous metnbrai (of the uterus) either appears smooth and possessing only zig-: longitudinal folds (Scyllium, for example), or it bears mnch-develo] villi (Acanthias vulgaris, Spinax niger, Scymnus lichia, Trygonpastinaca] These villi are placed sometimes (Acanthias rulgaris, Scymntu lichia} in very regular longitudinal rows which cease towards the end of uterus, and pass into leaf-like longitudinal folds ; or, as in Ti pastinaca, they are so crowded together that nothing more of the of the mucous membrane of the uterus appears. The villi possess exceedingly rich vascular supply : there are to be distinguished them at most two stronger vessels which interlace and run into another at the end of the villus, and between the two a close-mesh< vascular network. These vessels are in the gravid uterus dis- tinguished by a proportionately very thick circular muscular layer." There are figures (p. 318, Ed. 1857) of " the uterus of Trygon, opened, in order to show the villi " ; and of " a bit of the uterine mncosa of Spinax, somewhat more than the natural size," showing the much- developed villi, which are represented as two- to three-branched. The great comparative anatomist Johannes Miiller, in his exhaus- tive paper : " Ueber den glatten Hai des Aristoteles " (' Abhand. Ak. Wiss. Berlin,' 1840, p. 188), reviews more completely the state of knowledge up to that date of the Selachian uterine structures which, quite apart from the secretion of egg-coverings or the formation of yolk-sac placentae, are concerned in the elaboration of secretions L891.] Uterine Villiform Papilla of Pteroplatsea micrura. 361 ehich are to be considered either as providing nourishment for the jwing embryo after the nutritive yolk of the egg has been absorbed, )r as maintaining and increasing the nutritive material of the yolk. Of Spinax niger he says (loc. cit., p. 236) : — " The foetus in the iterus is distinguished by possessing no trace of an egg-shell, and by inner membrane of the uterus being beset by very long (six to sight lines long) filiform villi." More particularly of the genus Torpedo he writes (loc. cit., p. 230) : — The eggs possess no trace of shell membrane ; they are only sur- Dunded by an albuminous uterine fluid, as already Bedi, Stenonis, jrenzini, and in more recent times J. Davy, observed. Cavoliiii tates that the yolk sticks to the walls of the uterus, and that lis is effected by an innumerable crowd of red uterine glands ring on the yolk. By this are clearly meant the papilliform villi on le uterus of Torpedo oculata ; but the yolk-sac in no way adheres to le uterus, as the observations of J. Davy show, observations with ?hich what I myself have seen in the gravid uterus sent by Dr. Peters icords. The yolk-sac of the Torpedos is perfectly smooth. I can the extraordinary difference observed by T. Davy in the icture of the mucous membrane of the uterus, which in Torpedo is furnished with villi, in Torpedo marmorata with parallel >ngitudinal folds." Johannes Miiller also quotes Davy's observations the increase in weight, from the undifferentiated egg-stage to the jmpleted festal stage, in Torpedo, notwithstanding the disappear- ice of the external yolk and the absence of any vascular maternal jnnexion. Of the Spinacoid Shark Scymnus lichia he observes (loc. cit., 237) : — " In the fresh uterus, the foetus and yolk-sac are sur- Dunded by a white-of-egg-like fluid. Also in this Shai-k no trace of egg-shell membrane is met with. The foetus with its enormous 3lk-sac is immediately surrounded by the uterus. The whole oval ilk-sac is, in the younger and middle stages of development, 4 inches and 2 inches thick. The inner membrane of the uterus is rnished with cylindrical villi six lines in length." John Davy (' Phil. Trans.,' 1834, pp. 531—540), in the research the embryology of Torpedo, referred to by Johannes Miiller, escribes the mucosa of the gravid uterus of this Batoid, and icially dwells upon the absence of any vascular connexion between embryo and the mother. He states that, in several series of observations, while the average • reight of undifferentiated eggs was 182 grains, and the average sight of eggs in which the embryo had appeared was 177 grains, the rerage weight of " ripe foetuses " was 479 grains ; and he asks how, the absence of any sort of structural connexion between the foetus id the mother, this remarkable increase of weight is to be explained. 2 B 2 362 Prof. Wood-Mason and Mr. Alcock. On the [Mar. He observed that there was to be found in the uterine cavity little fluid, generally milky, more rarely glairy, and sometimes bl which, on evaporation, yielded crystals of common salt, and a little animal matter composed chiefly of albumen ;" and he specula1 on the possibility of this uterine secretion being nutritive, negatived, however, the supposition that the embryo in utero co take in food by the mouth, and inclined, finally, to the opinion tha the embryo increases by absorption, partly through the general surface of the body and partly through the branchial filaments. Sir Everard Home (4 Phil. Trans.,' 1810, p. 208), in a paper on the " Mode of Breeding of the Oviviviparous Shark," which is quoted by Joh. Muller, described the naked-eye anatomy of the oviduct of Acanthias vulgaris, the jelly and which fills that part of its cavity and which functions as a uterus in this Selachian. He states that when the young one is completely formed the yolk remains attached to the belly by a long cord of blood-vessels, and that the young one in thai state " swims " in the uterine jelly. The jelly he regards as a secre- tion of the oviduct. Home further quotes the observation of Dr. Patrick Russell, that a Shark caught in lat. 70° N. had the oviducts distended with yonng ones, each with the yolk-sac attached ; the young ones swimming in a " white gelatinous liquid, thicker than the liquor amnios of Quad rupeds." Home supposed that the function of the jelly was to aerate the foetal blood. To sum up, we find that in Spinax niger, Scymnus lichia, Acanthiat vulgaris, Trygon pastinaca, Torpedo oculata (and also in Myliobatit noctula and Centrina salviani, according to Trois, in a paper in the ' Atti del Istituto Veneto,' vol. 2, which we have unfortunately been unable to obtain), special glandular villi have been observed on the uterine mucosa, which villi have in some cases been supposed to bear, either to the egg or to the developing embryo, some relation of support or nutrition other than that of furnishing an egg-case, or of assisting in the formation of a vascular connexion (yolk-sac placenta) between the embryo and the mother. In Scymnus lichia, on the one hand, it seems certain, from Miiller's researches, that the villi secrete a fluid which nourishes the embryo through the medium of the yolk-sac ; while in Torpedo, on the other hand, it is certain that, at least in the later stages, the seci reaches the embryo in some less indirect manner, and the question has actually been asked whether it is ingested by the embryo. In corroborating the opinion as to the function of the villi ot Selachian uterine mucosa, we are able to bring evidence of a case in which the nutritive secretion is actually conveyed into the pharynx of the embryo. Following on this, and because the term " villus," in its connexions 1891.] Uterine Villiform Papillae of Pteroplatsea micrura. 363 idth mammalian physiology, has come to connote a structure which ssentially absorbs nutriment, we propose to term the villiform struc- tures of the uterine mucous membrane in Selachians, which essen- tially secrete nutriment, trophonemata ; and by this name they will i referred to in the descriptive portion of this paper. § 2. Recent Observations on the Uterine Villi of some Indian Rays. In the ' Journal of the Asiatic Society of Bengal,' vol. 59, Part II, , 51, the second-named contributor of this paper described some jbservations on the uteri and the gestation of Try g on bleekeri and [yliobatis nieuhofii, which it is necessary here to briefly recapitulate. In a large female of Trygon bleekeri, taken on the 15th December, 1888, in the Mahanaddi estuary, the distal end of the right oviduct ras found to be enormously dilated, and to contain in its cavity a lly-developed male foetus with a disk llf inches long and 10| iches broad. The folded foetus lay free in the uterine cavity, quite lestitute of membranous covering, without any structural con- lexion with the mother, and without any vestige of external yolk- The uterine mucous membrane, which was a vivid vascular rlet, such as in Fishes is usually seen in the gill-laminae only, was overed with an abundant highly-albuminous fluid, secreted by a rowded layer of glandular filamentous villi which formed the inner mfc; and it was inferred that this secretion was a uterine milk elaborated for the nourishment of the embryo. In the absence of any ecial absorbent organs, and because the embryo was so folded that ly supposed " absorbent function " of the skin would have been as inch as possible limited, it was further inferred that the " milk " ras taken in by the embryo by the mouth!; though unfortunately the foetal stomach was not examined until post-mortem changes were Ivanced. It may be mentioned that the foetus did not possess inchial filaments. Again, in Myliobatis nieuhofii, the structure of the uterine glands has een made out, but we have had no opportunity of ascertaining their slation to the egg or to the embryo. In an adult female, taken off ae Grodavari Delta on the 31st March, 1889, the left ovary was found be full of enlarged ova, while the distal end of the oviduct formed globular swelling with thick, muscular walls, and a mucous mem- rane thickly beset with long foliaceous villi. The entire surface of le mucous membrane, both villous and inter-villous, was found to Dnsist of a close-set aggregation of tubular glands, most of which rere simple follicles resembling the Lieberkuhniau follicles of human atomy, though at the periphery of a villus they are commonly Jmose. We have now, in the case of Pteroplatcea micrura, discovered 364 Prof. Wood-Mason and Mr. Alcock. On the [Mar. H'r another instance of a Batoid which develops a naked embryo in an uterus with a mucous membrane of a complex structure; and while the histological characters of portions of the uterine mucosa are those of a secretory gland, the disposition of these glandular portions is such as to leave no doubt that the greater part of their secretion ia poured into the pharynx of the embryo as it lies in the uterus. § 3. The Uterus and Embryo of Pteroplatsea micrura ; and the Rdati of the Uterine Villiform Papillae (Trophonemata) to the Embryo. In December, 1889, the detached pregnant uterus, with part of one oviduct and kidney, of a Bay which had been captured in the estuary of the Hooghly was sent to the Indian Museum by Mr. A. J. Milner, of the Bengal Pilot Service. The embryo, after removal, was identified as Pteroplatcca micrura (Bl. Schn.). The measurements of its disk are, length 3'4 inches, breadth 6'5 inches; its caudal spine is not yet developed, and the nasal valves are still separate ; its liver is of very large relative size, and the intestine is greatly distended with grnmous bile-stained material. The gravid uterus forms a symmetrical ovoid swelling ; dorsally its wall is almost membranous, ventrally it is still thin ; laterally, and especially antero-laterally, it is thick and muscular. Internally, it is lined with mucous membrane, which, dorsally and postero-laterally, is quite smooth. On the ventral aspect, however, the mucous membrane begins to be extended in the form of short, compressed papillae, and these, anteriorly and laterally, grow by degrees longer and more numerous, until, at a point in the antero-lateral part of the uterus which coincides with the position of the spiracle of the embryo in situ, they form on each side a large bunch of long-compressed villiform tro- phonemata, the histological structure of which will be presently described. On opening1 the pregnant uterus by a dorsal longitudinal incision, the naked embryo is found lying prone, head forwards, and tightly rolled in a right-to-left spiral. Although the embryo is in uniform close contact with the uterine walls, there is no sort of structural connexion between it and the mother, and no trace of any such pre- vious connexion : nor can any vestige of external yolk-sac be ob- served. But by the rolling up of the embryo the spiracles, which are large patent cavities communicating freely with each other and with the pharynx, and smooth-walled, except for a very faint pectination anteriorly, come to have a lateral position, and deep into them passes, on each side, the lateral bunch of long trophonemata above men- tioned, in such a way that the secretion of these richly -glandular 1891.] Uterine Villiform Papillce of Pteroplatsea micrura. 365 :>phonemata can only pass down the pharynx of the embryo. The only other external communications of the pharynx, namely, the mouth and gill-clefts, are firmly closed, the opposite margins of the 2xternal gill-clefts being in the most complete apposition. There are, 3nsequently, no branchial filaments. The trophonemata are narrow, strap-shaped processes of the uterine lucosa which widen very slightly and gradually from their base to about the middle of their length, whence they taper still more gradu- ly to their rounded apex. Those which enter the pharyngeal cavity )f the foetus are the longest of all, measuring from 18 to 20 mm. in ensrth and about 1'4 mm. in extreme breadth. Save for the presence jf a blunt thickening that traverses them in a somewhat sinuous jurse from base nearly to apex, tapering and branching as it goes, id standing out in fairly bold relief from both their surfaces, they ippear quite flat. Stained in borax- carmine, mounted in spirit, and viewed under a low power by reflected light, they present a minute, honey- combed ippearance of their surfaces due to the presence of innumerable small depressions. From the ap pressed conjunction of ridges which rand these, a slightly elevated polygonal network results. Transverse sections of a trophonema shew that these depressions the funnel-shaped mouths, narrowing below into the lumina, of lall, short, bulb-shaped glands of the same simple tubular type as seen, for example, in the crypts of Lieberkuhn, or, better still, in the gastric glands of anthropotomy. The glands are arranged perpendicular to the surface, side by side, the substance of the mucosa — into which they are, in fact, so many involutions of the investing epithelium — so that the bases of those of opposite sides are separated from one another only by blood vessels id a very meagre, if any, connective tissue. Vertical sections of a trophonema in planes parallel to its surface, jr, in other words, transverse sections of groups of glands, shew that lese are so closely packed as to be polyhedral by appression. For a certain distance from the base of the trophonemata the de- pressions are small and simple, but they soon become larger and ampound, each being then the common mouth or short duct of a little group of glands, just as in the human stomach, wnere one leets with simple glands, each with its independent opening, and rith groups of glands opening into a common depression of the lucous surface. The larger (secondary) depressions, it is obvious from an attentive study of the surfaces of several trophonemata, as well as from, trans- rerse sections, have resulted from the further depression of the smaller (pi-imary) depressions in groups ; and the raised margins of the former result from the coalescence of those portions of the margins Prof. Wood-Mason ami Mr. Alcock. On the [Mar. I1.'. of the latter which are not involved in the general secondary de- pression. The epithelium is very thick in the bulbous basal portion of glands : here its constituent cells are very long, taper from baseme membrane to lumen, and are arranged round an axial cell in the fo of a cone, of which the outer cells do not extend far up the sides the gland. Above this the cells become gradually shorter and 1 oblique, until at or near the month they pass into an ordina columnar epithelium resting perpendicularly on the basal membrane. The nucleus of the cells is oval, and stains very strongly. It lies eccentrically near the base of the cell, which stains only less strongly than the nucleus itself, so as to form a sharply-defined, coloured stratum, in which the nuclei are included, throughout the gla This deeply-stained band is most conspicuous in the basal cells, whi are arranged in the form of a cone, and perhaps constitute the chi< if not the only, seat of active secretion. Not a single cell in any of the sections has been observed to ha undergone mucoid degeneration ; but many have been noticed contain minute globules, probably of secretion, not only in t coloured basal portion, but also in the clear and unstained outer pa of their protoplasm. The sections shew coagulated secretion in the mouths and lumi of many of the glands. The glands measure 0*06 to 0'08 in len by 0'04 to 0'07 in breadth. In a trophonema, 12 mm. long by 1'4 m in uniform width throughout, taking O'Oo mm. as the average diameter of the glands, we have calculated that no less than 21,280 glands are present — a result which is probably not far from the mark either way. The trophonemata are exceedingly vascular. Two vessels are present in all : an artery, which runs in the substance of one of their margin and a vein, which takes a sinuous course not quite along the rnidd but nearer to the opposite margin, giving off in its course two three short branches which may or may not anastomose with main stem. Both vessels taper towards the apex, near to which they are resolved into a capillary plexus, or rather into a system of na: sinuous cavities which establishes a communication between the t sets of vessels. The wall of these cavities is formed of a deli nucleated membrane answering to, and appearing in some part almost every section to be in actual continuity with, the endothelial lining and subjacent intima of the vein, into which some of the sinuses can actually be observed to open occasionally. The vein is much larger than the artery: its calibre in that part of its course across which the section has been taken being no less than five times as great. The artery is strongly contracted and empty: the vein, on the other hand, is fully dilated and filled with coagulated blood, even to its lateral branches and the larger of its 1891.] Uterine Villiform Papilla of Pteroplatsea micrui'a. 367 affluent sinuses. Hence in lightly- stained trophonemata, examined entire under a lower power, the artery is only just visible by trans- parence, while the vein presents itself as a very distinct, branched, and tapering dark streak. The connecting system of sinuses occupies the plane between the layer of glands of opposite sides, sending off processes around the base or specially secreting portion of every gland. The glandular epithelium possesses no connective tissue framework eyoud a filmy nucleated gauze, shreds of which can be traced wher- ever vacuities occur between the bases of adjoining glands, the rhole trophonema consisting, as has already been stated, almost 3ly of epithelium and blood vessels. Having already stated our conclusion as to the function of the jphonemata in Trygon and Pteroplatcea, and having described the path taken by the secretion in the latter, it only remains to consider riefly how far other views of the manner of absorption by the ibryo of the nutrient uterine milk might apply in the case of these two fishes. Whatever may be the case in the earlier stages, in the later stages, at any rate, branchial filaments do not absorb nutriment 3m the maternal wall, for branchial filaments do not then exist. Again, absorption through the general surface of the body of the ibryo can hardly be looked upon as the principal channel of supply, luse the embnyo, at least in its later stages, is so folded or rolled as to leave as little extent of surface as possible available for Drption. [P.S., April 8, 1891. — Since the above was written and despatched, have had the good fortune to obtain from amongst the contents of fishermen's nets at Cocanada several pregnant females of roplatcea micrura. The examination of these specimens in the esh state, while it confirms our description in its principal particu- lars, renders some modification of it necessary. (1.) The number of ig may be as many as three in each uterus, both uteri being reloped. (2.) The number of young may be two in each uterus, ir first qualification will therefore be, Uterus well developed on both les ; each uterus may contain from one to three young ones. Again, lere two and three young ones exist, the trophonemata (which pear to be fairly well developed over the entire mucosa of the srus) are specially long opposite to the spiracles of the young one, which they pass. Apparently — and this will be our second quali- itton — in the early stages of gestation the trophonemata are equally developed over the entire surface of the uterine mucosa, but by the ire exerted by the groiving embryo they become greatly atrophied, on those spots where they can pass into the spiracles of the embryo, here, perhaps by compensation, they become hypertrophiedJ] 368 Prof. J. A. Mac William. [Mar. 1«J, II. " A New Test for Albumin and other Proteids." By JOHN A. MAC WILLIAM, M.D., Professor of the Institutes of Medicine in the University of Aberdeen. Communicated by Sir WM. ROBERTS, F.R.S. Received March 5, 1801. Salicyl-sulphonic acid is a remarkably powerful precipitant of pro- teid substances ; it is an extremely delicate reagent for the detection of proteids' in solution ; it acts upon all the classes of proteid bodies. I shall state the results I have obtained with this reagent under two heads : — I. Its action on the various classes of proteids. II. Its use as a test for the presence of proteids in urine. I. The Action of Salicyl-sulphonic Acid on the various Classes of Proteids. In order to obtain the full effect of this reagent, it should be in saturated watery solution, and a drop or two of this solution sho bo added to a small amount (e.g., 1 or 2 c.c.) of the fluid to betes and the test-tube should be shaken so as to mix its contents well. When any considerable amount of proteid is present, a copious white precipitate at once results ; with only minute amounts of proteid a cloudiness or opalescence of the fluid is what occurs. This cloudi-i ness or opalescence is uniformly diffused over the fluid. Wlfli dealing with traces of proteids it is well to use a control tube con- taining some of the fluid to be tested, and if dilution has been per- formed, another control tube with some of the water (or other liquid) used for dilution along with one or two drops of the salicyl-sulphonic acid. The observer then holds the three tubes between him and the light, and looks through them at a dark ground. It is only, however, when dealing with very slight traces of proteids that these precautions are at all necessary. A. Native Albumins. (a.) Egg Albumin. — Upon this proteid salicyl-sulphonic acid acts with much precision. When a solution is obtained by diluting wliiu of egg with water in the proportion of 1 part white of egg in 20 part of the mixture, the addition of the reagent causes a dense white pre cipitate to be at once formed. On boiling, the precipitate become* markedly flocculent. (The solution of white of egg of course contain* globulin, but when this is removed by saturation with magnesiuc sulphate the albuminous filtrate gives the same reaction with salicyl sulphonic acid as the original fluid.) 591.] A Neiv Test for Albumin and other Proteids. When a similar solution is made with white of egg and the proteid loved by thorough saturation with ammonium sulphate (after slight cidulation) and nitration, the proteid-free filtrate gives no precipitate rith salicyl-sulphonic acid. But if some of the precipitate thrown lown by the ammonium sulphate, after being washed with a saturated solution of the salt, be redissolved in water, the solution proteid so made gives a copious precipitate when tested as before, considerable amounts of ammonium or magnesium sulphate present, a few crystals may form and sink to the bottom of the 3, apart from the presence of any albumin. This, however, does at all interfere with the working of the test, as such crystals, iting in the fluid at first and then sinking to the bottom, bear no semblance to the uniform turbidity or opalescence dependent on the jsence of albumin. These salts are easily removed by dialysis.) Similarly, when the white of egg solution is treated with a large 3ss of absolute alcohol (after slight acidulation with acetic acid), as to precipitate all the proteids, and is then filtered, the filtrate aws no precipitate when tested with salicyl-sulphonic acid ; re- )val of the alcohol from the filtrate does not influence the result. . the other hand, the alcoholic precipitate, when (after being washed rith absolute alcohol) it is redissolved in water and tested, gives striking reaction : a large amount of proteid is at once thrown 3wn. With very dilute solutions made with white of egg, I have com- the delicacy of the action of salicyl-snlphonic acid as a test for )teids with a number of other reagents more or less commonly iployed, and I have found the former to be by far the most delicate id precise of all. The white of egg solution was successively, diluted to various 3es — 1 part of the white of egg solution (1 in 20) in 100, 200, ), 400, 600, 620, 900, and 1000 parts of water or of f per cent, sodic loride solution. With the first degree of dilution (1 part of the 1 in 20 white of solution in 100 parts of water or salt solution) the following re- Its were obtained : — Boiling after faint acidulation with acetic acid = no reaction. Xantho-proteic test = slight reaction. The cold nitric acid test (Heller's) = slight reaction. Mercuro-potassic iodide = haziness of the fluid. Salicyl-sulphonic acid = marked cloudiness. With the second degree of dilution (1 part of the white of egg lution in 200 parts of water) : — Boiling after faint acidulation with acetic acid = no reaction. Xantho-proteic test = no reaction. 370 Prof. J. A. MacWilliam. [Mar. 19, Meronro-potassic iodide = doubtful haze. Salicyl-sulphonic acid = marked cloudiness. When the white of egg solution is diluted 400 times : — Acidulation with acetic acid and heat = no reaction. Xantho-proteic test = no reaction. Heller's test = no reaction. Mercuro-potassic iodide = no reaction. Salicyl-sulphonic acid = distinct cloudiness. When the degree of dilution is increased to 600 or 620 times, t is still a distinct reaction with salicyl-sulphonic acid when the tube is compared with control tubes containing — (a) the dil solution alone, and (fe) water with salicyl-sulphonic acid. And even with still higher grades of dilution (900 and 1000 ti there is still an appreciable effect recognisable a little time after addition of the reagent. The amount of proteid present in those dilute solutions is ex ingly small. Taking the percentage of proteid (albumin and globulin) in w! of egg as 12'2, the strength of the original white of egg sola (1 in 20) would be less than 1 in 160. When this solution is diluted 400 times, the proportion of pro is less than 1 in 64,000 ; when diluted 620 times, about 1 in 100,i and when diluted 1000 times, proteid is present only in the very minute amount of 1 in 160,000. (6.) Serum Albumin. — Solutions containing serum albumin were obtained by saturating serum with magnesium sulphate and then filtering so as to remove the globulin ; the filtrate contained the serum albumin. This fluid, when tested with salicyl-sulphonic acid, gave an abundant precipitate. Again, when the serum is deprived of all its proteids by complete saturation with ammonium sulphate and subsequent filtration, it then fails to give the slightest sign of precipitation on the addition of salicyl-sulphonic acid. On the other hand, the proteid precipitate thrown down by ammonium sulphate, when redissolved in water, gives a dense precipitate with salicyl-sulphonic acid. Similarly, when serum is deprived of its proteids by means of alcohol, the remaining constituents are entirely unable to give the characteristic reaction with salicyl-sulphonic acid. The delicacy of the action of salicyl-sulphonic acid as a test for minute amounts of the serum proteids is very striking, just as in the case of the egg proteids. The following reactions will serve as an illustration of this : — Some ox serum was diluted with £ per cent, of salt solution to the extent of 1 part of serum in 1000 parts. 1891.] A New Test for Albumin and other Proteids. With this dilute fluid various tests were tried : — 371 Salicyl-sulphonic acid = marked opalescence at once. Boiling after faint acidulation with acetic acid = no reaction. Heller's test = no reaction at once. Distinct film at junction of the two fluids in a few minutes. Xantho-proteic test = no appreciable results. Mercuro-potassic iodide = marked cloudiness. Saturated salt solution with hydrochloric acid (Roberts' test) = marked cloudiness. Serum diluted to 1 in 10,000 : — Salicyl-sulphonic acid = distinct cloudiness (especially after | — 1 minute), recognisable on comparison with the control tubes in a suitable light. Boiling after faint acidulation = no reaction. Xantho-proteic test = no reaction. Mercuro-potassic iodide = no reaction. Roberts' test = no reaction. Copper sulphate and caustic potash (Piotrowski's) = no reaction. Heller's test = no reaction at the time nor twenty minutes after- wards. The amount of proteid present in these dilute solutions is, approxi- itely, as follows : — Taking the percentage of total proteids in ox serum as 7'5,* the im diluted to the degree of 1 in 1000 would contain less than of proteid in 13,000 ; while with the dilution of 1 in 10,000 amount of proteid would be about 1 in 130,000. B. Derived Albumins. (a.) Acid Albumin. — A solution of acid albumin, obtained from a lution of white of egg by the addition of a few drops of a dilute acid subsequent warming, gives a copious precipitate on the addition salicyl-sulphonic acid. (&.) Alkali Albumin. — A solution of this proteid, obtained by iting the white of egg solution with a dilute alkali, also yields abundant precipitate on being tested with salicyl-sulphonic acid. C. Globulin. A solution of globulin obtained from blood serum (by precipitating ith magnesium sulphate, and subsequently redissolving in dilute It solution) gives results similar to albumin. * Hammarsten, " Ueber das Paraglobulin," ' Pfluger's Archly,' 1878. 372 Prof. J. A. MacWilliam. [Mar. 1 '.., And vegetable globulin obtained from flour (by extracting with 10 per cent, salt solution) behaves similarly. D. Fibrin. Solutions of fibrin, both when a dilute alkali and when 10 per cent, salt solution are used as the solvents, give white precipitates %vith salicyl-sulphonic acid. In the case of all the foregoing proteids (A, B, C, and D) the precipitate does not redissolve on heating ; on the other hand it becomes markedly flocculent. E. Proteoses. Primary albumoses (proto-albumose and hetero-albnraose) were prepared from Witte's peptone by precipitating them with sodic chlor- ide and (after washing with saturated solution of salt) redissolving the precipitate (containing some salt) by the addition of water. The solution so obtained gave a marked precipitate with salicyl-sulpho acid ; but in this case the precipitate redissolved on heating reappeared on cooling. Solutions of secondary albumose (deutero-albumose) gave simi results. F. Peptone. Solutions of peptone were obtained from albumin artificially digested with pepsin and hydrochloric acid, by saturation with am- monium sulphate and subsequent filtration. The filtrate contained peptone; it gave no precipitate with nitric acid, while it gave the xantho-proteic and the biuret reactions. On adding a drop of salicyl-sulphonic acid to a small amount of the solution containing peptone, a precipitate was at once formed. This, like the precipitate of albumoses, readily disappeared on heating and reappeared on cooling. Solutions containing peptone were also prepared by saturating the artificially digested albumin solution with sodio-magnesic sulphate, and similar results were obtained. Solutions of Witte's peptone were (after being faintly acidulated with acetic acid) saturated with ammonium sulphate in some cases, and with sodio-magnesic sulphate in others. The filtrate contained peptone, the other proteids having been precipitated by saturation with the salts named and removed by filtration. The peptone solu- tion yielded, on being tested with saturated solution of salicyl- sulphonic acid, a reaction similar to that described above, a precipi- tate which disappears on heating and reappears on cooling. 1891.] A New Test for Albumin and other Proteids. 373 When the peptone was removed by precipitation with excess of alcohol and filtration, the remaining fluid failed to give the slightest proteid reaction with salicyl-sulphonic acid. It will be noticed that there is an important difference in the be- haviour of proteoses and peptones as compared with the other proteid bodies under the influence of the salicyl-sulphonic acid ; the pre- cipitate yielded by the proteoses and peptones clears up on heating, and reappears on cooling, while the precipitate of the other proteids does not clear up on heating, but, on the other hand, becomes markedly flocculent. In this respect the reagent resembles picric acid and mercuro-potassic iodide, and to some extent also nitric acid. It differs from the latter, however, inasmuch as the latter gives no ipitate with peptones. s regards the nature of the precipitate of egg albumin, or urn albumin, thrown down by salicyl-snlphonic acid, its general appearance might suggest that not only precipitation, but also coagulation, had occurred, as with nitric acid, &c. But the fact that is soluble on the addition of a sufficiently large amount of a very ,k solution of potassic hydrate (O'l per cent.) or of sodium car- mate (1 per cent.) shows that no coagulation could have taken place. Solution of the precipitate does not take place as long as any acidity remains in the fluid. And when it has been redissolved the addition of a very small amount of a weak acid (nitric, acetic, sulphuric) can again bring about precipitation. The precipitate of albumin thrown down by salicyl-sulphonic acid ot redissolved by the addition of even considerable amounts of acid, nor is it dissolved by nitric acid, except when a large iunt of the strong acid is added. hen salicyl-sulphonic acid is made to act upon albumin for some me, especially at a high temperature, and the precipitate is then itered off, the filtrate shows a very marked coloration, varying from inkish tint to a bright amethyst. The filter paper commonly .ows a staining of the same colour. When the fluid is filtered hot, the filtrate usually shows evidence of containing albumoses; it mes turbid on cooling, and clears up on heating. The colora- n of the filtrate is most marked and pure when the fluid is clear ., when hot) ; when it is turbid the colour is, to some extent, :ed and modified (often to an orange-pink tint) by the presence the precipitate. II. On the use of Salicyl-sulplionic Acid as a Test for Proteids in Urine. Jalicyl-sulphonic acid gives no precipitate whatever with normal ic. 374 Prof. J. A. MacWilliam. [Mar. In the case of albuminous urine, on the other hand, it constitutes an extremely delicate and precise test for the presence of pr Hy its use, coupled with heat, one can, with great facility, recognise very minute amounts of proteid substance, and can discriminat between the so-called "albumin" (albumin and globulin), most com monly found, and the albumoses or peptones, if such are preseni This is easy, since the application of heat in the latter case causes th precipitate to disappear — to reappear on cooling ; while, in the case ordinary albuminous urine, the precipitate does not clear up on heatinjj The method of performing the test in the case of urine is the same as with other solutions. A very small amount of urine should be taken in the bottom of ordinary test-tube (e.g., half an inch, or so), or a very small, narrow test-tube may be used. The acid must be in a thoroughly saturate aqueous solution. A drop of this solution is then added to the urine and the tube is shaken. When any considerable amount of proteid is present, a copious precipitation immediately occurs ; when there only a minute proportion of proteid, the fluid becomes unifo: opalescent. The delicacy of the test if. shown by the following results, ob with one of the samples of albuminous urine examined : — The urine was diluted to 10, 20, 30, 40, 50 times. AVith weakest of these fluids (1 in 50), salicyl-sulphonic acid quie gave a marked opalescence. Heller's test gave no reaction for a considerable length of time then it gave a doubtful haziness at the junction of the nitric aci and the urine. Picric acid (saturated watery solution) = no reaction. Cupric sulphate and potassic hydrate = „ „ The urine was then diluted twice as much, to 100 times, and still gave, after standing a little, a distinct cloudiness with salicyl-snlph- onic acid, specially noticeable when the tube was compared (in a suitable light) with two control tubes, containing respectively (a) some of the dilute urine, and (b) water with a drop or two of salicyl- sulphonic acid. Even with much greater degrees of dilution, appreciable r< were got by means of this test. Without going to the extreme limits of its application, however, I find that in the case of the urine diluted 100 times, the amount of albumin contained must have been exceed- ingly small. A quantitative determination showed that the amount of urine present in the undiluted urinW was about O'l per cent. Hence the amount present in the urine diluted 100 times must have been about 1 in 100,000. The opalescence caused by the addition of salicyl-sulphonic acid to 1891.] A New Test for Albumin and other Proteids. 375 such very dilute albuminous solutions does not clear up on boiling. It remains persistent for days in the cold, the precipitate after a time assuming the form of a marked cloud at the lower part of the ?st-tube. The effect of adding salicyl-snlphonic acid to samples of albuminous irine from which the albumin had been removed was tested in many 38, and always with negative results. The albumin was precipi- ited by means of absolute alcohol (after acidulation, when necessary) by saturation with ammonium sulphate. The proteid-free filtrate ive not the slightest reaction in any instance when tested with ilicyl-sulphonic acid in the usual way. The characteristic reaction of even minute amounts of albumin in ic urine I found to be given, on the addition of salicyl-sulphonic Did, in very numerous and various conditions — in acid, neutral, and Ikaline urine ; in urines rich in mucin, phosphates, urates, &c. ; in les containing bile, sugar, and other abnormal constituents. My ssults, obtained from the examination of a large number of samples urine, have not indicated that the applicability of the test is com- plicated or interfered with by any of the abnormal constituents present. The urine of persons under the influence of various drugs (e.g., alcohol, quinine, sulphonal, croton-chloral, iodide of potassium, iloroform, salicylate of soda, strophanthus, &c.) has not shown the lightest reaction with salicyl-sulphonic acid when shown to be free albumin by other tests (after concentration) or when freed >m albumin, if such has been present, by means of alcohol or iinonium sulphate. I have also examined the effect of salicyl-sulphonic acid upon jlutions of various substances, many of which give precipitates with Brtain of the well-known reagents for the detection of albumin in pine — solutions of strychnine, digitalin, morphia, nicotin, chloral bydrate, atropine sulphate, aconitine, ergotin, caffein citrate, stroph- ithin, sulphonal, gallic acid, quinine, bromide of potassium, copaiba, 3. — and in no case have I seen any reaction at all resembling that rielded by proteids. The conclusion to which my results up to the present lead is that licyl-sulphonic acid is probably the most delicate and precise of all lown reagents for the detection of proteids in solution. Note on the Nature of Salicyl-sulpTionic Acid. Salicyl-sulphonic acid is a whitish crystalline substance, readily :>luble in water and in alcohol. On slow evaporation of its aqueous jlution, it crystallises in long, thin needles. Its formula and formation are stated in Beilstein's ' Handbuch d. rg. Chemie,' 2nd ed., vol. 2, p. 969. (For this reference I am in- VOL. XLIX. 2 c 376 Dr. W. Huut.-r. '/'/„ Influence of debted to Professor Japp, F.R.S.) The formula is there given as CeH3(OH)(SO3H)COOH ; and its formation by the action of sulphuric anhydride on salicylic acid (Mendios, 'Ann. Chem. Pharm," vol. 103, p. 4§), or by heating salicylic acid with concentrated sulphuric acid (Remsen, ibid., vol. 179, p. 107). It is said to be very stable, and to undergo no change on heating with nitric acid. The specimens of salicyl-sulphonic acid which I have used in my experiments were obtained from Messrs. Davidson and Kay, Union Street, Aberdeen. III. " The Influence of Oxygen on the Formation of PtomaincR." By WILLIAM HUNTER, M.D., F.R.S.E. Communicated by Professor M. FOSTER, Sec. U.S. Received March 11, 189 ' (Abstract.) A special interest attaches to the role of oxygen in the life-hisl of bacteria. Very wide differences exist, however, between diff< groups in respect of its importance. To the great majority a supply of oxygen is absolutely essential for their proper growth ai development ; to a small minority the converse applies, growth proceeding best in the absence of oxygen, if indeed it is not entirely prevented by its presence ; while, lastly, in the case of an inter- mediate group it seems almost immaterial whether oxygen be present or not, growth proceeding apparently equally well in both conditions, provided that the supply of food be otherwise suitable. Of these three groups of " obligate aerobic," " obligate anaerobic " and " facultative aerobic " bacteria, respectively, the last has perhaps the greatest interest for the pathologist, as it is to it that the great majority of pathogenic organisms belong. The question is thus an interesting one, to what extent the patho- genic properties of this class of bacteria are related to the power they, apparently under necessity, possess of obtaining their supply of oxygen from the food constituents themselves when the supply in the air is cut off. The present paper deals with the results of an investigation un< taken in this relation. It was necessary that the class of bacteria selected for study should be one whose pathogenic properties were not constant, but subject to variations presumably connected with the character of their sur- roundings. The bacteria of ordinary putrefaction possess in a special degree this qualification, their chemical products differing much in char and poisonous action under different, for the most part as yet un- known, conditions. L891.] Oxygen on the Formation of Ptomaines. 377 The method chosen by which to gauge the influence of oxygen on pathogenic properties of bacteria was to estimate the quantity of Ikaloidal bodies or " ptomaines " formed in the putrefactive process, scording as oxygen (1) was freely admitted; (2) was present in loderate quantity ; or (3) was withheld altogether. For our knowledge of the ptomaines of putrefaction we are chiefly idebted to the researches of Brieger. In their order of formation as pell as complexity, the most commonly met are choline, C5H15N02 ; idaverine, C5HUN2 ; putrescine, C4H12N2 ; trimefhylamine, (CH3)3N ; limethylamine, (CH3)2NH ; and methylamine, (CH3)NH2. The ptomaines most characteristic of the early stages of putre- 3tion are the diamines, which include, in addition to cadaverine jentamethylenediamine) and putrescine (tetramethylenediamine), ther two isomeric with the former, but of different, as yet unknown, institution — neuridine (C5H14TSr2) and saprine (C5H14N2). With the exception of choline, all these bodies are non-poisonous ; id choline only produces symptoms when given in very large doses. In this respect they differ from another group which possess arkedly toxic properties, e.g., muscarine (C5H15N03), an oxidised lerivative of choline, and neurine (C6H13NO), also obtainable from loline artificially by warmiiig with baryta water ; as also two other >dies to which Brieger gave the name of mydatoxine (CCH13N02) and '/dine, C8HUNO. While the poisonous bases are oxidised, the harmless bases are an-oxidised, a circumstance which led Brieger to conclude that sygen plays an important part in the formation of poisonous Ikaloids, and that a free access of oxygen favours the formation of Dmaines generally.* The observations now recorded supply data for judging how far icse conclusions are correct. Their chief result is to show that the formation of the ordinary putre- Mve. ptomaines is favoured by the entire absence of oxygen; the tantity formed under such circumstances being several times greater in ivhen oxygen is admitted. Method of ResearcJi. The method employed for the isolation of the ptomaines was that of Jrieger. Equal quantities of extract of meat, obtained by extracting meat with cold water, were allowed to putrefy, for periods iging from 5 to 8 days, under the three following conditions : — (1.) Free Supply of Oxygen. — The fluid was placed in a large glasa Blinder, open at both ends, kept in continuous rotation round a jrizontal axis. The direction of rotation was alternately from right " Weitere TJntersuclmngen iiber Ptomaine." Hirschwald. Berlin, 1885, p. 27. 2 c 2 „ 378 Dr. W. Hunter. The Influence of [Mar. to left and left to right ; the fluid was thus kept in continual agitation, and uniformly distributed over the inner surface of the cylinder. (2.) Moderate Supply of Oxygen. — The fluid was placed in a wide- mouthed jar, and stirred freely from time to time. (3.) Exclusion of Oxygen. — The fluid was placed in a narrow-necked bottle which it nearly filled ; excess of oxygen at the outset was driven out by a stream of hydrogen ; the bottle was then tightly closed by an india-rubber stopper through which passed a glass tube suitably bent and opening externally under mercury. In (2) and (3), the vessels were maintained at a uniform tempera- ture of 32° by being suspended in a water tank. In most of the ex- periments, a certain quantity of extract of pancreas was added, to hasten putrefaction, with 10 grams of CaC03 to prevent the in- jurious action of the acids formed in the early stages of the process. The conditions of the experiments varied somewhat in other respects, either as regards the quantities of material used, or its nature, or the manner of dealing with it. The experiments made, eight in number, thus divide themselves into three series, each made up of two or three different observations under the conditions above noted. The attempts made in the earlier experiments to isolate the indi- vidual ptomaines in the form of their platinum or gold salts failed, owing to the small quantities present. Attention was afterwards confined to the diamines, and accurate quantitative results were obtained by use of benzoyl chloride — ft reagent which, as Udranzky and Baumann have shown, forms bulky and stable derivatives with all bodies of this nature. Results. The results of the observations show : — (1.) That a free supply of oxygen prevents entirely the formation of ptomaines, the only base found under such circumstances — and that too from the very first — being ammonia. (2.) With one exception, all the experiments agree in showing that, as judged by the relative quantities of diamines formed, the greatest formation of ptomaines takes place when oxygen is entirely excluded. The differences between moderate supply of oxygen and entire absence in this respect ranged from 2:1 to as much as 27 : 1 in the observations made, the greatest formation always taking place where oxygen was excluded. The one exception to this can be explained by a difference in the procedure, the effect of which was probably to destroy a large number 591.] Oxygen on the Formation of Ptomaines. 379 the diamines in the observation in which oxygen was excluded. The relation in this instance was reversed, viz., 1 : 3*8, the largest quantity being obtained where oxygen was admitted in moderate quantity. (3.) Observations were also made on the effect of lengthening the -duration of the putrefactive process when oxygen was entirely tcluded. The result showed that on the 13th day the diamines jre reduced to one-fourth of the quantity present in a similar lount of fluid, exposed to the same conditions, on the 7th day. (4.) In all cases the bulk of the benzoyl compound obtained was Je up of cadaverine, its melting point varying according to purity 127°'5 C. to 129° C. Putrescine was only present in traces. (5.) The results of the observations on the quality of the bases sent were not so definite. The most definite symptoms of poison- ing were obtained in one instance from the injection of a fluid which putrefied in the absence of oxygen. They included prostration, 3reased peristalsis, and diarrhoea, and on another occasion rise of emperature. Conclusions. Certain conclusions are drawn from the above data, partly of a ns prove certain of the latter to be in modifying in a very material the fermentative action of bacteria generally. ;iso Mr. A. Mallock. Some Measure* of [Mar. HI. IV. " Some Measures of Young's Modulus for Crystals, &c." By A. MALLOCK. Communicated by LORD RAYLEIGH, Sec. R.S. Received March 9, 1891. The Table at the end of this communication contains the results of experiments made in October, 1889 — February, 1890, on the elasticity of various bodies. The measures relating to crystalline bodies are, I believe, new. The method used to obtain these results was applicable to very small specimens. This was a necessary condition in the case of most crystals, because of the difficulty of getting large specimens without flaws. In the experiments now to be described, I am dealing only with the values of Young's modulus, but by a modification of the apparatus, measures can be made of the simple rigidity, which will, I hope, the subject of a future communication. Of course, the simple rigidity must lie between one-half and o: third of the value of Young's modulus, according to the ratio be longitudinal extension and lateral contraction (Poisson's con for the substance. The apparatus used in my experiments is shown in figs. 1 and 2. Fig. 1 shows the general arrangement of the parts, and fig. 2 is full-sized diagram of the mirrors and knife-edges. The lettering is the same in both figures. A, is a vertical FIG. 1. L89L] Young s Modulus for Crystals, $c. FIG. 2. 381 - cross section of beam abe carrying the oblique arms B, B'. On B is mounted the tele- 3ope T, and on B' the collimator C, having in its principal focus the iss scale S. and K3 are two parallel horizontal knife edges, mounted on a iss support at the upper end of A. On these knife edges the sub- ince to be examined rests, and a third knife edge, K3, parallel to le other two, and half-way between them, Avhich. is properly guided rnd free to move only in the vertical plane passing through its edge, cesses on the substance with a force determined by the magnitude the weight W and its position on the graduated arm D. 382 Mr. A. Mallock. Some Measures of The fulcrum of D is the knife-edge Kj, and a wire passing through A connects the knife-edge K4 with K3. The substance to be examined is formed into a small rectangular beam, rather longer than the distance between the fixed knife-edges KI, K2, and to the projecting ends of the beam the mirrors M,, M2 are cemented. These mirrors are mounted in brass frames, and from the back of each frame a small brass tongue, EE' (fig. 2), projects, which is the actual part to which the cement is applied. The two other larger mirrors M3, M4 are inclined to one another at an angle of 45° nearly. They are fixed in a rigid brass mounting, which rests on the horizontal flat surface FF, from which two studs project, so placed that when the mounting of M3, M4 is in contact with both, the intersection of the planes of MI and M2 is parallel to the knife-edges Klt K2. The horizontal width of the mirrors MI, M2 is less than half that of Mj, MI, and the telescope and collimator are so placed that their axes of collimation graze the vertical edges of M, and M2. It is necessary that the planes of Mt and M2 should be nearly, but not quite, parallel, and this is effected by cementing the mirrors to the experimental beam whilst the former are held in the gauge shown in fig. 3. FIG. 3. A spring, not shown in the figure, keeps the mirrors pressed against the plane faces A, A' of the gauge. These are parallel in the vertical direction but inclined to one another about 2' or 3' horizontally, i.e., the planes A, A' intersect at this angle in a line parallel to OY. 591.] Young's Modulus for Crystals, tyc. 383 The cement is applied to E and E' before the mirrors are placed in gauge ; when they are in position, the beam is laid with one end on E and the other on E', and warmed. When cool, the experimental beam with the mirrors attached is removed from the gauge and laid in the proper position on K1} K2. On looking through the telescope T, two images of the scales S will be seen side by side. One of these images being formed by successive reflection from the four mirrors M2, MI, M3, M1} in the ler named, and the other by reflection from M3 and M4 only. The course followed by the two sets of rays is indicated by the >ws on the dotted lines in fig. 2. The appearance of the scales in the field of the telescope is shown in £. 4. If MI and M2 were absolutely parallel in a horizontal direc- FIG. 4. on, the scale images would at times exactly overlap one another, irhich would make readings difficult. As long as the condition of approximate parallelism of the inter- 3ctions of the pairs of mirrors is fulfilled, any shifting of one image the scale past the other is due to an alteration of the angle between pair or other of the mirrors, and to that alone, and since M3, M4 in a rigid mounting, any relative motion of the images is due to alteration in the angle between Mj and M2. The experiments were made by noting the relative motion of the lages when force was applied to the beam by the central knife-edge The course usually followed was to start with no load on K3, and aving noted the relative position of the scale images, to move W long D until the scales had moved relatively through one division. 384 Mr. A. Mullock. &.. •• M '*ure» of [Mai. 1'.-. The reading was then taken on D. W being then moved forwards until another scale division had been reached, the position of W . .u D was again read, and so on. The process was afterwards reversed and mill ings of the same kind taken when the load was being diminished step by step. All these results were then plotted, and the curve drawn through the observations gave a measure of the angle between the ends of the beam in terms of the force applied to its middle point. In nearly all cases the lines drawn through the plotted observations were straight lines, within the limits of errors of observation, but, in general, tin- lines for each substance differed appreciably, according to whether the strains were increasing or decreasing. Some of the plotted diagrams are appended to show the kind of accuracy attained. The actual linear motion of the central knife-edge was always verjfr small, not in any case exceeding 0'00016 inch. I pass now to the treatment applied to the experimental results, in order to deduce from them the values of Young's modulus. If I, b, t are the length, breadth, and thickness of a beam (originally straight), q = Young's modulus, F = Normal force applied at its mid-length, 0 = Angle made by the tangent at each end with the tangent at its mid-length, , FP 3FZ* = and = If, now, B be the distance between the divisions of the scale S, n, the number of divisions through which the images of the scales are relatively displaced, and / the focal length of the collimator, the angle observed, 0 = nljf. Now 0 = 40, because 20 is the actual alteration of angle between MI and M2, and this is multiplied by two by the reflection. Also, if B be the reading of the position of W on the arm D, and r the distance between K4 and Ks, the downward force acting on K3 is F = W ~ ; r 3WR/P hence q = In this expression^ for the value of q, the factor /r/cr is a con- depending only on the apparatus, since I is the distance between K! and K.. L891.] Young's Modulus for Crystals, 385 is a constant for each beam, and R/w is the inclination of the straight line passing through the plotted observations to the axis Hence putting , A for -J— , Sr B for -- , , ot3 and C f or W , n Log q = log A + log B + log C. The numerical values of quantities involved in A were as follows : — Focal length of collimator, / = 8'87 inches. Length between knife-edges, K1} K2, I = 0'3422 inch. Distance between division of scale 8 = O'Ol. Distance between knife-edges K4, K5 = I/O. The values employed for & and t varied between O'l and O'Ol inch, id for W from 0'02 to 0*25 pound. The chief and indeed the only jnsiderable source of error in these experiments is in the measure- lent of t. The measures were made with a screw micrometer ling to O'OOOl by estimation. The average value of t was between 0'03 and 0'04, so that the leasurement was probably accurate to something like 1 in 400. Eence, there may be an error in t3 approaching 1 per cent. In the case of crystalline substances, beams cut from the same leighbourhood of the same crystals exhibit a constancy, in the results obtained from them, of this order, but in passing to other specimens lore difference was observed. In many substances, and notably in the case of zinc, lead, and white irble, it was found that the full deflection due to a given load was lot reached until a considerable time had elapsed, and experiments nth such substances would of course lead to different values for foung's modulus, according as the observations were made in rapid iccession or slowly. The behaviour of zinc in this respect was so marked, that a sparate set of observations were made with that material, the results )f which are shown in diagrams (10) and (11), pp. 394-395. It will be seen on examining these diagrams that, starting with a 2shly annealed piece of rolled zinc (and similar results were ob- lined from a beam cut from a large crystal of cast zinc), that, on the irst application of the force, the bending immediately produced con- inues to increase for many minutes, and that, when the load is amoved, the beam does not recover itself all at once, and also that permanent set has taken place. On the second application of the force, however, if the force is not iter than that first applied, the behaviour of the zinc is quite ferent. It now very rapidly assumes its maximum deflection and 386 Mr. A. Mallock. Some Measures of [Mar. 19, drops back to its equilibrium position, on the removal of the force, still more rapidly, but little further permanent set being produced. On again increasing the force so as to exceed that first applied, a further gradual extension, lasting a considerable time, takes place ; and additional permanent set is found when the force is removed. Diagram (11) shows that — (1.) The immediate elastic bending and the permanent set are pro- portional in amount to the force causing them. (2.) That the increment of extension or deflection which happens in time is something like a constant quantity. The method, however, described in this paper is not well adapted to the investigation of these phenomena, as the state of strain in the beam on which they depend varies from + through 0 to — on L891.] Young's Modulus for Crystals, fyc. 387 jpposite sides of the neutral axis, and one cannot be sure that the rery slightly strained material of the central parts acts in the same ray as that near the tipper and lower boundaries. In nearly all the substances experimented on, it was found that rork was done in bending and unbending the beams, i.e., for a given leflection the load was always less when the latter was being liminished than when it was being increased. This effect was gene- illy more apparent in metals than in hard crystals. On reference to the Table (p. 398), it will be seen that only ten of the ion-metallic substances examined at all approach steel in stiffness. I regret that I have not hitherto been able to get a specimen of liamond of suitable form for measurement ; but I hope to be able to jive Young's modulus for ¥this and some other crystals in a supple- icntary table. B88 Mr. A. Mallock. Some Measures of [Mar. 19, Young's Modulus for Crystals, fyc. 389 390 My. A. Mallock. Some Measures of [Mar. 19, 1891.] Young's Modulus for Crystals, $-c. VOL. XUX. •2 D Mr. A. Mallock. Some Measures of [Mar. I'1. >1.J Yovmj* Moduli for Crystals, fyc. I II PI m mm a i 12 1-4 16 « Mr. A. Mullock. Some Measures of [Mar. 19, [891.] Young's Modulus for Crystals, $c. 305 396 Mr. A. Mallock. Soini' Mi"-'ireg of [Mar. lit, Explanation of tJie Diagram*. Diagrams (1) to (9) are examples of the diagrams used in determin- ing the ratio R/n. The ordinate is the scale-reading on the arm D (6g. 1). unervations does not in general point the origin is due to the fact that the mirrors were not quite para! in a vertical direction at the beginning of the experiment ; in fact, according to the position in which the spring holding the mirrors against the faces of the gauge was placed while they were being cemented to the beam, variations of rather more than a minute of ar were produced between their planes. The abscissa reading when ordinate = 0 has of course to be subtracted from n in getting true ratio B/n. The spots indicate individual observations, and are mart with arrows whose directions show whether the load was beii increased or diminished. Diagram (1). (a)W t I = 0-0302 = 0-1100 0-2581 Ib. inch >5 ] wrought iron. (/,) W = 0-3710 Ib. Diagram (2). t b W — 0-0322 0-0918 0-2511 inch- Ib." } cast iron. Diagram (3). b NY — 0-0208 0-1075 0-0671 inch >i Ib. ! platinum. Diagram (4). t b W = 0-0461 0-0955 0-1381 inch » Ib. 1 copper. Diagram (5). t b W Diagram (6). / b W Diagram (7). t b W = 0-0473 inch -j = U-1190 „ > bismuth. = 0-0671 Ib. J = 0-0304 inch 1 = 0-0757 „ > carbuncle = 0-0671 Ib. = 0-0369 inch = 0-0911 „ = 0-0671 Ib. quartz. L89L] Young's Modulus for Crystals, beryl. 397 Diagram (8). t = 0'0415 inch b = 0-0877 „ W = 0-1381 Ib. Diagram (9). t — 0-0292 inch I - 0-1065 „ W = 0-0217 Ib. fluor. In diagram (9) the abscissa is plotted to a different scale, since, swing to the extreme brittleness of fluor spar, a displacement of only aut 1'5 of the ordinary division of the scale could be safely use rhen the thickness of the specimen was about 0'03 inch, and many ims of this substance were broken in attempting to produce greater sxures. In this experiment the greatest departure of the centre of the 3am from its unstrained position is about O'OOOOl inch. Diagram (10) shows some of the properties of zinc. The curves lumbered 1 to 8 are really one continuous experiment. A light reight was allowed to act on a beam of sheet zinc, and the deflections lused by it were noted every thirty seconds for ten minutes. These leflections are shown by the first part of curve 1. The weight was len removed, and the recovery of the beam was observed for five linutes. This forms the second part of curve 1. The experiment was then repeated with the same weight, and the suits are shown in curve 2. Additional weight being applied, the line course of procedure gave curves 3 and 4, and in like manner by till further additions of load curves 5, 6 and 7, 8 were obtained. The dimensions of the beam were : — t = 0-0373 inch 6 = 0 1558 For curves, 1, 2 „ 8, 4 „ 5, 6 •7 8 » <•> o weight = 0-4026 Ibs. „ =0-8052 „ „ = 1-657 „ = 2-110 Diagram (11) gives (a) the permanent set, (&) the immediate stic deflection, (c) the deflection at the end of ten minutes. These taken from diagram (10). 39* Yountfs Modulus for Crystals, [Mar. I1.' Table of Values of Young's Modulus. Substance. Young's modulus, Ibs. per square inch. Young's modulus. C.G.S. Steel 33-5 x 108 2 -311 x 10" 27'0 1-863 Platinum 25-42 1-754 Cast iron (soft grey) 23-31 1-608 17-65 1-218 Brass 16-38 1-130 Cobalt 12-89 8-895 x 10" 8'73 6-025 Bismuth* 4-16 2-87 Lead . 2-71 1-87 Zincf 1 -4 to 0 -89 9'7 to 6-1 x 1010 34'83 x 10* 2-430 x 1011 CarbuncleJ (another speci- men , 34*38 £-372 Beryll 30-9 2*076 18'76 1-294 17-5 1-207 Fluorll .... 17-39 1-200 FluoriF 17 -18 1-185 16-38 1-130 13-79 9-515 x 10" Yellow topaz J (6) 12-75 8-80 11-79 8-135 Quartz** 10-82 7 -46 10-09 6*96 9-25 6-381 White "Arkansas " stoneft- SeleniteJ J 8-45 7-98 5-83 5*505 " Extra dense " flint glass. . 7-48 4-64 5-165 3-20 White marble 1 -6 1 -1 * Cast bismuth. The beam cut parallel to a natural crystalline cleavage of the metal. t The greatest value is that obtained from obserrations taken in rapid succes- sion. J Relation of tne faces of the beam to the crystallographic axes not known. The specimens marked (b) are cut at right angles to those marked (a) . § A very black opaque crystal from the Ural ; (a) cut parallel to the side of the prism, (6) normal to the sides. || Parallel to diagonal of the cubic crystal. T Parallel to face of cube. ** Parallel to sides of prism. ft A very close-grained oilstone. +t Parallel to the principal cleavage. L891.] On the Chief Line in the Spectrum of the Nebulce. «, " On the Chief Line in the Spectrum of the Nebulae." By JAMES E. KEELER, Astronomer of the Lick Observatory. Communicated by WILLIAM HuGGiNS, D.C.L., LL.D., F.R.S. Received March 13, 1891. As my paper on the Motions of the Planetary Nebulae in the Line of Sight* did not give a final determination of the exact position of the chief nebular line, and might therefore possibly be regarded as leaving in abeyance the question as to whether that line could be regarded as a remnant of the magnesium fluting, I beg to be allowed state briefly the results of some more recent observations, which ,ve enabled me to fix with great accuracy the true position of, the ief nebular line. At the time when my paper on the motions of the nebulae was printed, I had not been able to obtain any satisfactory comparisons of the third nebular line with terrestrial hydrogen, all the nebulae in my list having proved to be too faint for the purpose. I was, therefore, compelled to adopt the mean position of the principal line for the ten nebulae observed as the normal position from which to easure displacements, and it was for the reason that the ten nebulae id not have the uniform distribution in the sky which was desirable at the numerical results for their motions were stated as " not to regarded as final." In October, 1890, when the Orion nebula came within reach of the lescope, comparisons of the third line with the H/3 line of hydrogen ere made without difficulty, and on the same nights the position of e principal line was determined. One such double observation, if rfect, completely solves the problem, since the displacement of the ird line gives the necessary correction to the position of the first, .e only question is in regard to the accuracy of the observations. It is evident from what has already been written on this subject Dr. and Mrs. Huggins, Professor Lockyer, and myself, that the swer to the question whether the chief nebular line is coincident ith the edge of the magnesium fluting at A, 5006*4 depends pon very small differences of position, differences which would, fact, be considered small even in solar spectroscopy. But eir minuteness, although it increases the practical difficulty of Tvation, does not detract from their importance, since abso- te coincidence of spectral lines is necessary (although not always fficient) to establish a claim to identity of origin. It is there- ire necessary to determine from a careful consideration of the ick Observatory measures whether they are of a sufficiently high * 'Publications of the Astronomical Society of the Pacific,' No. 11, p. 265. 400 Mr. J. E. Kcrln. "i, tl,,> [Mar. in. order of accuracy to prove that the small observed interval betwc the nebular line and the magnesium fluting is real, and not due errors of observation. A detailed account of all the tests to which the apparatus was sub- jected cannot be given here. Nothing that suggested itself wi omitted. The best tests, however, both for constant and accidental errors, are afforded by observations of the motion in line of sight of bodies whose motion is already known. As example of such observations, I may refer to the measures of motion of Venus in the line of sight given in the table on p. 21 1 Publications of the Astronomical Society of the Pacific,' No. 11, ii which the greatest error is one English mile per second. Simil measures of the displacement of lines in the lunar spectrum we seldom in error by more than two miles, and measures of the moti< of a-Tauri and a-Orionis, usually made on the same nights that nebula was observed, were of the same order of accuracy, as det mined by their agreement with each other, and with the photograpl results of Professor Vogel. In work of this character the periodic shifting of lines in .spectra of the stars and nebula? due to the earth's annual motion is of a magnitude not to be neglected, and it should appear in the cor parison of observations made at different seasons. So faithfully ii the orbital motion of the earth reflected in my observations on nebula of Orion, that I would with some confidence undertake determine the month of the year, by measuring the distance of principal line from the lead line used in the comparison spectrum. With these remarks on the degree of accuracy which character the observations, 1 give below the results which have been obtaii up to the present time, for the nebula of Orion. From sixteen complete measures, made on eleven different night (two of which were in the winter of 1889-90), the wave-length the principal line, corrected for orbital motion of the earth, X 5006'22 + 0'014, the probable error corresponding to an unc tainty of U'5 mile per second in the line of sight. When t\ measures were made on the same night, they were always in differ spectra of the grating. Ten comparisons of the third nebular line with terrestrial hydrogen were made on seven nights in 1890-91, showing, when corrected for the orbital motion of the earth, a displacement of the nebular line toward the red of 0'28 + 0*026 tenth-metres. This corresponds to a motion of recession of the nebula from the sun of 10*7 + I'O miles per second. In recent comparisons of hydrogen with the third nebular line, I have not been able to attain the small probable error of 1^ miles per second for a single evening's comparison, given in my letter to the 1891.] Chief Line in the Spectrum of the Nebula'. 401 • Observatory,' as the first comparisons were made under exception- ally favourable conditions. Some small improvements in the apparatus make it probable, however, that it can be readied in the iuture. Examination of the individual results for each night's work shows that the errors are purely accidental ; hence, the mean of the results for the third line will be used to determine a correction to the mean )f the results for the first line. A displacement of the third line toward the red of 0'28 tenth- letre corresponds to a displacement of the principal line, in the same direction, of 0'29 tenth-metre, which is the amount by which the principal line is seen to be too near the red end of the spectrum, account of the recession of the nebula from the sun. Hence the wave-length of the principal line, if determined by an jbserver at rest relatively to the nebula, would be X 5005'93, and this, therefore, is the normal position of the chief nebular line, according to 11 the observations of the nebula of Orion which have been made, up to the present time, at the Lick Observatory. The probable error of this jsult is, by the theory of least squares, 0'03 tenth-metre. The posi- tion of the MgO fluting, on the same scale, is X 5006'36 or O43 tenth- ictre below the normal position of the nebular line. An interval )f this magnitude is not only measurable with my apparatus, but loticeable at a glance in the telescope. An incident which occurred during the course of the work lay be mentioned here, as showing how much greater the above- ited interval is than any error which could be made under good mditions of observation. The measures of January 26, 1891, on )eing reduced the next morning, made the interval between the icbular and lead lines 0'15 tenth-metre greater than it should have en according to previous measures. This difference led me at ice to infer that something was wrong with the apparatus, and on examining the instrument I found that the observing telescope was 3t to a reading 5° different from the usual one, in such a direction lat a higher dispersion than usual had been employed. On deter- ling the value of the micrometer for this position of the grating, id re-reducing the observations, the discrepancy was then but a few hundredths of a tenth-metre. In the ' Journal of the British Astronomical Association,' Mr. taunder says, in reference to the possibility of my having over- leasured the interval between the chief nebular line and the edge of the magnesium fluting, " Further, some allowance must be made for the difficulty of comparing a line with a fluting ; we ought certainly lot to measure from the centre of the nebular line to the extreme of the fluting. This will apply a small, but a further, correction the same direction." Mr. Maunder's criticism does not, however, 402 On the Chief Line in the Spectrum of ///>> Xcl-ulrc. [Mar. 19t apply to my own observations, which were made with this difficulty in view. If the distance between the line and the edge of the flutii could be measured with a slit-width vanishingly small, the interval would be obtained. With a practicable slit-width, tl position of the centre of the line is unchanged, but the edge of tl fluting is shifted toward the red by half the width of the line, my observations of nebulae, the slit-width used was such as to the bright, sharp load line (and hence, also, the nebular line) just width of the coarse micrometer wire (about 0'4 tenth-metre). Tl bright lines were observed by occulting them with the wire, observations thus referring to their centres, but the magnesiui fluting was observed by bringing its extreme edge and the lower of the micrometer wire into coincidence, the centre of the wire fallii therefore upon the edge of the fluting with infinitely narrow slit Measures of the interval between the lead line and the edge of tl magnesium fluting, made with the fine micrometer wire and narrow a slit as could be used, gave the same value as measi made in the manner just described.* The correction mentioned Mr. Maunder is therefore unnecessary. It appears to me, from what has been shown above, that the non- coincidence of the chief nebular line and the magnesium fluting nu be regarded as proved. In regard to the character of the line, recent observations at Mount Hamilton have shown nothing which does not confirm the opinion I have already expressed,! that under no circumstances of observation does the line tend to assume the aspect of the remnant of a fluting. The observations which have been made at Mount Hamilton demonstrate the incorrectness of the view that the chief nebular line is in any way connected with the magnesium fluting at X 5006'36, for reasons which may be briefly summarised as follows : — (1). The nebular line is 0'43 tenth-metre more refrangible than lower edge of the magnesium fluting. (2). The nebular line has no resemblance to a fluting. (3). Flutings and lines of magnesium, which could not fail to * I may call attention to the fact that my own value of this interval (1*86 tenth* metres) is 0'04 tenth-metre smaller than the most reliable measures which have yet been published. t " A single prism of 60° was Qrst employed, then a compound prism of about three and one-half times the dispersion of the latter, and finally a Rowland grating of 14,438 lines to the inch. With all these different degrees of dispersion, and alia with other spectroscopes employed, the nebular lines appeared to be perfect mono* chromatic images of the slit, widening when the slit was widened and narrowing to excessively fine, sharp lines when it was closed up. The brightest line showed no tendency to assume the aspect of a ' remnant of a fluting ' under any circumstance* of observation." — ' Publications of the Astronomical Society of the Pacific," No. 11, p. 266 and 280. L891.] Presents. 403 ippear at the same time with the fluting at X 5006,36, are entirely ibsent in nebular spectra. Additional reasons have been given by Professors Liveing and )ewar, and by others who have investigated the subject, but I wish consider here only such observations as have been made at the Lick Observatory. The" Society then adjourned over the Easter Recess to Thursday, April 9th. Presents, March 19, 1891. Fournals. American Journal of Philology. Vol. XI. No. 3. 8vo. Baltimore 1890. The Editor. Ateneo Veneto. Ser. 13. Vol. II. Fasc. 4-6. Ser. 14. Vol. I. Fasc. 1-6. 8vo. Venezia 1890. The Ateneo Veneto. Boletin de Minas. Aiio 6. Num. 9-11. 4to. Lima 1890. La Escuela de Ingenieros, Lima. Epigraphia Indica and Record of the Archaeological Survey of India. Part 6. 4to. Calcutta 1890. The Editor. Fortschritte der Physik im Jahre 1884. 8vo. Berlin 1890. Physikalische Gesellschaft, Berlin. •Galilee (Le) 1891. Nos. 1-4. 8vo. Paris. The Editor. Horological Journal. No. 390. 8vo. London 1891. The Horological Institute. Mittheilungen aus der Zoologischen Station zu Neapel. Bd. IX. Heft 4. 8vo. Berlin 1891. Dr. Dohrn. Naturalist (The) Nos. 186-187. 8vo. London 1891. The Editors. Nature Notes. Vol. II. Nos. 13-14. 8vo. London 1891. The Selborne Society- Revista do Observatorio. Anno 5 ; Num. 12. Anno 6 ; Num. 1. 8vo. Rio de Janeiro 1890-91. The Observatory, Rio de Janeiro. Revue Medico-Pharmaceutique. 1891. No. 1. 4to. Constanti- nople. The Editor Stazioni Sperimentali Agrarie Italiane (Le). Vol. XIX. Fasc. 6. 8vo. Asti 1890. R. Stazione Enologica di Asti. Victorian Year-Book for 1889-90. 8vo. Melbourne 1890. The Government of Victoria. -Zeitschrift fur Naturwissenschaften. Bd. LXIII. Heft 1. 8vo. Halle 1890. Naturwissenschaffclicher Ve^rein, Halle. 404 Present*. Buckton (G. B.), F.R.S. Monograph of the British Cicadas. Parts 3-5. 8vo. London 1890-91. The Author. Colenso (W.), F.R.S. A Description of two newly -discovered Indi- genous Cryptogamic Plants. 8vo. [Ifobart 1889.] The Author. I huibree (G. A.), For. Mem. R.S. Experiences snr les Actions niques exercees sur les Roches par des Gaz a Hautes Tempera- tures. 4to. Paris 1891. The Author. Dawson (G. M.) On the Glacial ion of the Cordillera. 8vo. [Mon- treal] 1890. The Author. Fletcher (L.), F.R.S. On the Mexican Meteorites. 8vo. London 1890. With sixteen additional Pamphlets in 8vo. The Author. Ives (J. E.) Echinoderms from the Northern Coast of Yucatan and the Harbour of Vera Cruz. 8vo. [Philadelphia 1890.] The Author. Leconte (F.) Etude Experimentale sur un Mouvement Curienx d€ Ovoides et des Ellipso'ides. 8vo. Geneve 1890. The Author. Lewis (T. H.) Stone Monuments in North-Western Iowa and South- Western Minnesota. 8vo. St. Paul 1890. The Author. Norman (J. H.) Local Dual Standards. 4to. London 1886. [Re- vised 1890.] The Author. Plantamour (P.) Des Monvements Periodiques du Sol. 8vo. Geneve 1890. The Author. Ramos-Coelho (J.) Historia do Infante D. Dnarte Irmao de El-rei D. Joao IV. Tomo II. 8vo. Lisboa 1890. The Lisbon Academy of Sciences. Reade (T. M.) Mammalian Bones in the Blue Clay, Alt Moutl 8vo. Liverpool 1890; Secular Straining of the Earth. 8vo. Hertford 1890. The Author. Rydberg (J. R.) Recherches sur la Constitution des Spect dominion des Elements Chimiques. 4to. Stockholm 1890. The Author. Shaffer (N. M.) What is Orthopaedic Surgery ? 8vo. New To 1890. The Author. Terry (J.) Sculptured Anthropoid Ape Heads. 4to. New Yorl 1891. The Author. Uslar (P. K.) Ethnography of the Caucasus. Vol. IV. [Russian.] 8vo. Tiflis 1890. Le Curateur de I'Arrondissement Scolaire du Cauc Ventosa (V.) Metodo para Detenninar la Direccion del Viento por las Ondnlaciones del Borde de los Astros. 8vo. Barcelona 1890; La Direction des Vents Superienrs determined par les Ondula- tions du Bord des Astres. 8vo. Bruxelles 1890. The Author. Presents. 405 Washington (Major F. P.) Lecture on the Methods and Processes of the Ordnance Survey. 8vo. 1890. The Author. roodward (A. S.) and C. D. Shei-born's Catalogue of British. Fossil Vertebrata. Supplement for 1890. [Extracted from Geol.Mag.] 8vo. Hertford 1891. The Authors rolf (B.) Astronomisohe Mittheilungen. No. 76. 8vo. [Ztmc/i] 1890. Dr. Wolf. On Electrostatic Screening by Gratings, Sec. 405 Washington (Major F. P.) Lecture on the Methods and Processes of the Ordnance Survey. 8vo. 1890. The Author. roodward (A. S.) and C. D. Sherborn's Catalogue of British Fossil Vertebrata. Supplement for 1890. [Extracted from Geol. Mag.] 8vo. Hertford 1891. The Authors, f (R.) Astronomische Mittheilungen. No. 76. 8vo. [Zurich] 1890. Dr. Wolf. April 9, 1891. Sir WILLIAM THOMSON, D.C.L., LL.D., President, followed by the Treasurer, in the Chair. The Presents received were laid on the table, and thanks ordered >r them. The following Papers were read : — " On Electrostatic Screening by Gratings, Nets, or Per- forated Sheets of Conducting Material." By Sir WILLIAM THOMSON, D.C.L., P.R.S. Received April 2, 1891. I. Grating. 1. Maxwell, in his "Theory of a Grating of Parallel Wires" ('Electricity and Magnetism,' Arts. 203—205,* and Plate XIII), pves a very valuable and interesting two-dimensional investigation of electrostatic screening, and a most instructive diagram of " Lines of Force near a Grating," which powerfully helps to understand and extend the theory, and to acquit it of an accusation wrongly made linst it in the last two sentences of Art. 205. It is only on the supposition of the grate-bars being circular cylinders that the ivestigation is less than rigorous : and that supposition nowhere iters into the investigation ; it merely appears in the word " radius," the first line of the last sentence but one of Art. 204, and it is con- licted in lines 3 and 4, and by the rest of the sentence, and by the icxt sentence. (See § 6 below.) 2. The conclusion, " a = — O'lla," in the last sentence of Art. 205, >ndemned as " evidently erroneous," is quite correct, and very iteresting. It shows that a corrugated metal plate agreeing with * In formula (7) of Art. 204, delete A. ; in Art. 204, delete 2 in last line of p. 250 Edition 1873) ; and delete 2 in lines 6 and 16 from foot of the page. VOL. XLIX. 2 K 406 Sir W. Thomson. On Electrostatic Screening [Apr. 0 the eqnipotential surface c = ^a, exceeds in electrostatic capacity a plane metal surface through the poles of the diagram (Plate XIII, reproduced in § 9 below), with the surroundings described in Art. 204, and supplies the datum requisite for finding the exact amount of the excess. The reason for the greatness of the excess clearly is that the surface c = £o, which just touches the plane through the poles of the diagram midway between the poles, is everywhere nearer than this plane to the other plate of the condenser. (See § 7 below.) 3. For c = a/6 we have, by (11) of Art. 205, a = o, and the corre- sponding equi potential, partially shown in Maxwell's diagram, is a set of curves concave towards z = — oo , and asymptotic to the lines a- = (t±^)a, t denoting any integer, (See §§ 10 to 13 below.) For every value of c less than a/6, the equipotential is a row of ovals ; and the grating formed by constructing these ovals in metal has less electrostatic capacity in the circumstances described in Art. 205 than a plane through the poles or the ovals (this being no doubt what is meant by " a plane ... in the same position " as the grating). 4. For every value of c exceeding a/6 the equipotential, instead of being the boundary of a grating, is a continuous corrugated surface, and its electrostatic capacity exceeds that of the plane through the poles. 5. Begin now afresh, and let it be required to find the electric force in the air on either side of an infinite row of parallel bars at equal consecutive distances, a, each uniformly charged with electricity. Let pa be the quantity per unit length on each bar, so that p would be the surface density, if the same quantity were uniformly dis- tributed over the plane of the bars. Taking 0 in one of the bars, OX perpendicular to the bars, and OZ perpendicular to their plane, we find (by Fourier's method) for the z-component of force at any point (x, z) for which z is positive, Z = a where m — 2w/a Summing this we find Z = _ 2irp a €*•* — 2 cos mx + e This has equal positive and negative values for equal positive and negative values of z, and it therefore gives the value of the s-force, not only for positive, but also for negative, values of z. Taking now — f Zdz, with constant assigned to make the integral zero for z = + D, we tirid V = pa (log - - ---- rmD ) (4) V fi€~ — 2COS TH3- + 6-~ / ........ V/ . 191.] I'll Gratings, fyc., of Conducting Material. 407 I 1 the potential due to the grating, and two parallel planes at equal distances, D, on its two sides, each uniformly electrified with half the quantity of electricity of opposite sign to that on the grating. 6. If now we construct in metal, C, any one complete equipotential surface, V0, of this system, and electrify it with the same quantity of electricity as that which we gave originally to the infinite row of infinitely thin bars ; and if we place metal planes, B, B', at the two places of zero-potential (z = +D), we have an insulated conductor at potential YO, between two planes, B, B', at zero potential, and at distance 2D asunder, on each of which the electric density is ^/>. For brevity, I shall denote the insulated conductor by I. 'ts electrostatic capacity per unit area of its medial plane (the ne of the original infinitely thin bars) is /»/V0- '. This conductor, I, is symmetrical on each side of its medial plane, and consists either of an infinite number of isolated parallel bars, each surrounding one of the original infinitely thin bars, or of a late symmetrically corrugated on its two sides, with maximum and inimum thicknesses respectively at the places of the infinitely thin i, and the lines midway between them. For the case of isolated ars, let 2c be the diameter of each, in the medial plane. Then, to nd V0, we must put x = +c and z = 0, in (4). Thus we find 4 sin2 — / (5). a [ence the electrostatic capacity of I in the circumstances is rhich is greater or less than l/(27rD), the electrostatic capacity that i would have if reduced to its medial plane, according as c> or < ±a. Mie conductor I, to be a grating, implies c<^a, or sin2 — <1, and a lerefore requires that V0>27r/>(D — — log 4^ = 27r/)(D--22a) (7), V 27T J When V0 exceeds this critical value, the conductor I is the con- inuous plate corrugated on each side, which was described in § 7. le critical value corresponds to an intermediate case of a plate so leeply furrowed on each side as to be just cut through by its two irfaces crossing at right angles ; and (7) shows that the electrostatic 2 E 2 408 Sir W. Thomson. On Electrostatic Screening [Apr. capacity of the conductor I so constituted is equal to that of a plant sheet of thickness 2alog[2*]/(2*r), or '44 a insulated midway between the two earth plates 8, B', at the distance asunder as they had with I between them. 8. By (4), (5), and (7), we have for the equation of the sui constituting the two sides of I in this critical case, = 4 Taking double the positive value of z which this gives when x = we find Salog [(1+ ^/2*f\l(2ir)t or '562a as the maximum thickness of I. This is log (l + v/'2)/log2, or 1'S times the amount shown in (8) for the thickness of the plane-side plate of equal electrostatic capacity ; which is just such a relation as ii expected before calculation ! 9. If 0(z, a;) denote what V becomes when in place of mD we sut stitute — mz in (4), we have the potential due to a uniform electric force pam, or 2-a-p, added to the z-component, of the force due to tl grating with its given charge of pa quantity per unit length of each bar; and it is the eqnipotentials and lines of force of this system that are represented in Maxwell's diagram of Plate XIII, reproduced her In it the resultant force for infinitely large positive values of z is parallel to OZ, and of constant value 47iy> ; and it is zero for infinitely large negative values of z. The approximation to these values is very close, at only so moderate a distance as a on either side of the grating. 10. Choosing, in the system of §6, any one of the multiple-oval 1891.] by Gratings, $c., of Conducting Material. 409 jquipotentials around the infinitely thin bars, that indicated by the shading, for example which I have added to Maxwell's diagram, let c be the distance from the infinitely thin primary bar within it, at which it is cut by the plane of the primary bars. By putting, in the expression for 0(z, x), z = 0, and x = c, we find 0(0, c) = pa log 4 sin'' — a (11) the potential at the surface of each of these chosen ovals. Con- struct now each of these ovals in metal, and let the supposed uniform force, 27T/3, be produced by uniform electrification of density — />, on a ictal plane, B, at any great distance, 6, on the positive side of the iting. We thus construct a grating of thick bars of oval-shaped 3ross section which, when electrified with the same quantity of elec- ricity as that which we gave initially to the infinitely thin bars, and subjected to the influence of the equal quantity of negative electricity :>n B, has 0(z, x) for potential through external space from B (z = fe), infinite distance on the other side of the grating (z = — oo), and for potential through all the portions of space within the surfaces the grate-bars the constant value expressed by (11). In this system the potential, for positive values of z great in comparison with i, is, by (4) with — mz instead of = —4irpz (12). le difference of potentials between B and the grating is, by (6) ind (5), „ • -2 T' 4sur - (13). [ence the electrostatic capacity of che mutually insulated system, B, and the grating of oval-shaped bars is equal to the capacity of a pair of parallel planes, B and a plane at a distance beyond the plane of the primitive infinitely thin bars equal to 47T log . . , 7TC 4 sin2 — (14). 11. If in (4) we put — nz in place of -\-rnD, we have the potential of system in which besides the electricity of the primary bars there is listant electricity such as all in all to give at great enough distances )n the two sides of the primitive bars uniform fields of z-force re- spectively equal to 410 Sir W. Thomson. On Electrostatic Screening [Apr. />(m+n), for z = + 00; and p(m—n), for z = — oo. -..(!{ If, in (4) with — nz instead of + mD, we put we find, as the equation of the equipotential surfaces, —2 cos ma + <•*•+ c-~ = Ce-" ( By taking n = 0, or n = m, we fall back on the cases of §§ 5-8, §§9, 10, respectively. 12. To find an approximate equation for the equipotentials at dii tances around primitive bars small in comparison with a, the distanc from bar to bar, let x and z be so small that we may neglect powers of mx, mz, and nz, above the square, which implies that C small of the same order as (mx)2 and (mz)2, (11) becomes where r2 denotes m~~2C. This shows that, to the degree of approximation in which we negl cubes and higher powers of mx, mz, nz, the equipotential is a row elliptic cylinders of eccentricity nrj v/2, with their greater diamet planes perpendicular to the plane of the primitive bars. When n = 0, the equipotential is a row of circular cylinders having the primitive bars for their axes ; and this is true to the higher approximation in which we need only neglect powers above the cubes of mx and mz, as we see by going back to equation (17), with n = 0. 13. The conclusions of § 12 are useful for detailed investigation of the screening effect of plane gratings of circular or elliptic, straight parallel bars electrified with given quantities of electricity and placed with their planes perpendicular to the lines of force in a uniform field of force, and to corresponding problems in which potentials are given, as in Maxwell's §§ 203 — 205. 14. Instead of a single row of parallel equidistant infinitely thin bars in one plane, let us take for primitives two or more such rows, parallel or not parallel, all in one plane or not in one plane. We may thus form an endless variety of force-systems available for illustrating or helping to solve problems which may occur. Towards the several problems of electric screening we find important contributions by considering in two parallel planes rows of primitive lines parallel to one another for one case and perpendicular to one another for another case. The consideration of three rows of primitive lines in one plane, dividing it into equal and similar triangles alternately oriented in L89L] by Gratings^ fyc., of Conducting Material. 411 )pposite directions, leads to a complete theory of electrostatic screen- ig by a triangular lattice of metallic wire or ribbon. The funda- lental potential formula for this system obtained by summation of tpressions, each given by an application of (4) to one of the three )ws, is = log. — 2 COS mg-f- — 2 COS nr-\- e'"')^ V ---- (19); rhere o, 6, c denote the intervals between the successive lines of the iree systems ; -aro, pb, determinate, we might sup either the total quantity of electricity on S, or the potential at whi its metal is kept, to be given. We shall take the latter supposition, and call the given potential C. 20. Let 0 denote the potential which would be produced by th electricity of S if it were spread continuously over the medial with electric density equal to /> at (x, y, z) ; and let wiin (23) denote the potential in the metal of S, due to the actual distribution of electricity on its surface. 21. To understand the meaning of this notation (;»), consider a large area around (a;, y, z), so large that its border is very distant from (x, y, z) in comparison with the thickness of the sheet, and with the diameters of its apertures, but not so large as to deviate sensibly from the tangent plane at (x, y, z). Let the electricity of all the surface of S beyoud A be changed from the imagined continuous distribution to the actual distribution on the surface of the perforated metal. This change will make no sensible difference in the potential at (x, y, z). Next, let the imagined continuous distribution of uniform electric density />, over the continuous area A, be changed to the actual dis- tribution of the same quantity over the surface of the perforated metal of the porous sheet A. The augmentation of potential at (x, y, z) produced by this charge is what we denote by ftp, where /* is a coeffi- cient depending on the shapes and magnitudes of the perforations, that is to say, on the complex surface of the perforated metal. It would be zero if there were no perforations, and we shall see that the by Gratings, $-c., of Conducting Material. 413 greater it is the less is the screening efficiency. We shall therefore call ft, the electric permeability, and fir1 the electric screening efficiency of the perforated sheet. The sheet is homogeneous as to permeability or screening efficiency if ft has the same value for all parts of it, but we .eed not assume this to be the case ; on the contrary, we shall suppose to be any known function of (a;, y, z). In §§ 5 — 16 we have the xplanations necessary for determining p in the various cases of gratings and nets there described. For similarly perforated surfaces, the values of fi are as the linear dimensions of a perforation or of the rs or bosses of the structures. 22. The equation of electric equilibrium is 0+/*/> = K (a constant) rhen S, being insulated and electrified, is not under the influence any other electrified matter. It is K-V .................. (25), when S is under the influence of any given electrified bodies pro- iucing a given potential, Y, at (x, y, z). 23. As a first example, going back to (24), let fi be such that 0 lall be constant. This makes, if we denote by A; a constant, (26), being a constant), which means that the screening efficiency is, in different places of S, inversely proportional to -the electric density at ilarly situated places of a continuous electrified conductor of the .me shape as S. Let, for instance, S be an ellipsoid ; then, if the sizes of the perforations be inversely proportional to the perpendicular from the centre to the tangent plane, (26) is satisfied. Generally, to fulfil this condition, the net must be finer in the more convex and more projecting parts, and coarser in the flatter and less projecting parts. 24. If any perforated conductor or cage, S, fulfilling the condition of § 23, be electrified and insulated away from the disturbing influence of other conductors, or electrified bodies, the charge distributes itself so as to have in every part the same quantity per unit area of the medial, as a smooth continuous metallic surface agreeing with the medial and electrified with the same total quantity. When the medial is a closed surface, the electricity on the perforated surface does not nfine itself to the parts of it outside the medial : on the contrary, en the apertures are very wide in compaiison with diameters of cage-bars, bosses, &c., the electricity distributes itself almost equally on the parts of the complex surface inside and outside the medial. 25. Seeing that the electric density (as defined in § 17) is the II 414 Sir W. Thomson. On Electrostatic Screening [Apr. 9, same for a perforated surface fulfilling the condition of § 23 as for the medial constructed in continuous metal, we naturally ask the question, what then is the difference between the two cases, if any, besides the fact of the electricity being equally but very unequably distributed over the outer and inner portions of tin- complex surface in one case, and equably over the outside of the smooth medial in the other ': There is a very important and interest- ing difference. The electrostatic capacity of the perforated con- ductor, S, is less, in the ratio of 1 to 1 + k, than that of the medial constructed in continuous metal ; as we see by (23) and (26). • 26. As a sub-example, suppose S to be a spherical surface. homogeneously perforated, it will fulfil the condition of § 23 : and its screening efficiency is the same as that of a grating of parall bars (circular cross section of diameter 2r; distance from centre centre a), we have, by (o) of § 7, when vc/a is very small, Now, S being spherical, if R denotes its radius, we have (§ 20) 0 = 47rR,> .................... (28) Hence, by (26) and (27), a . a 1 . a k = — ~ log - = v? lo£ - 2rR 5 re N 62»C where N denotes the number of bars in the equatorial belt of the cage of § 27 below. 27. To illustrate a realisation of § 26, let a spherical cage be made up of a narrow equatorial belt of approximately straight parallel bars of diameter 2 c, and distance from middle of one bar to middle of next, a ; completed by polar caps (nearly hemispheres) of thin metal perforated so as to have everywhere the same effective electric screening efficiency l{2a log (a/2 ire)}. Suppose, for instance, the bars to be of " No. 18 gauge ' (2c = 0'122 cm.) and a = 5 cm. We have log (a/2a-c) = log 13 = 2-57. Hence, for this case, and any other in which the ratio o/c is the same, we have, by (27) and (29), ft. = 5-14 a ..................... (30), 18 891.] by Gratings, fyc., of Conducting Material. 415 IThus, if a = 5 cm., and R = 50 cm., Tc = 0'0409 = -^ ; and (§ 25) e electrostatic capacity of the spherical cage ff of that of a simply continuous spherical surface of the same magnitude. 128. Let now an electrified metal globe, or globe of insulating aterial uniformly electrified, G, be insulated concentrically within S. It may be of any magnitude, large or small, provided only that the interval between the two surfaces be at least two or three times the diameter of the largest of the perforations of S. Let S be con- nected with the earth, and let Q denote the quantity of (positive) electricity with which G is electrified, and Q' the quantity of the opposite electricity which it induces on S. The potential in the ictal of S due to Q' is, by (23), iis, added to Q/R, the potential due to G, must be zero, and there- fore (33)' •,by(26), Q = Q'(l+4) (34). Hence, in the particular case of § 27 (31 ), Q = Q'(l l+ 0-409 .............. (35); and when R = 10a, we find Q — Q' = ^V Q> an<^ conclude that the effect of S, earthed, with G electrified and insulated within it, is just per cent, of the effect of G unscreened. 29. If S is connected with the earth, and supported at a height ve the earth equal to at least six or eight times its diameter, the antity of electricity (positive in fine weather) induced on it will l/(l + k) of that which would be induced on a simply con- nous metal globe of the same size. Hence the potential at any int of the air within S at not less distance inwards than 2 a will be :/(l + k) of the undisturbed atmospheric potential at the same height above the ground, or 5 per cent, in our particular case. This quite in accordance with the imperfectness of the screening effect ainst atmospheric electricity found by Roiti* within earthed wire iges, supported at a considerable height above the ground, by a cket attached to the top of a wall of a building in Florence, ted by a water-dropper with its nozzle inside the cage con- * " Osservazioni Continue della Elettricita Atmosferica " (' Pubblicazioni del Istituto di Studi Superior! in Firenze '), Florence, 1884. 416 Sir W. Thomson. On Electrostatic Screening [Aj nected by an insulated wire with a quadrant electrometer in the buildings. 30. The problem of finding the distribution of electricity on a spherical cage, of equal electric permeability, /t, in all parts of its surface, formulated in (25) of § 22, is easily solved by aid of spherical harmonics. Confining ourselves for brevity to the case of external influencing bodies, let their potential at any point, P, within S be (36)» where Si denotes a given spherical surface-harmonic of order t, and r the distance of P from the centre of S. And /»,-, denoting an unknoi surf ace- harmonic of order t, let be the harmonic expression for />, the required electric den Going back to § 20 for the definition of 0, we find, by the elements spherical harmonics, Hence, by (25), K + So _(2t pi= 1 + and 0 = K + 2- (2t + l),i R< IT" Jn (39) we have virtually the same result as in (33). The approxi- mation on which we are founding in §§ 17 — 29 is valid in (40) and (41) only for values of t small in comparison 2-a-R/a: but, as in virtue of greatness of the logarithm for the case formulated in (27), /t may be great in comparison with a ; and therefore the denominator of (40) need not be only infinitesimally greater than unity, and may be any numeric however great. 31. Taking S,r = x, S2 = 0, Ss = 0 . . . . , we see by (41) that if an insulated unelectrified spherical cage be brought into a uniform field of electric force, X (that of atmospheric electricity, for example, at any height above the ground exceeding five or six diameters of the cage), the force within the cage is 1891.] by Gratings, fyc.. of Conducting Material. 417 * -— (42), or, according to (27), and (29), X , or X (43). 3a a 3 , a This result is also applicable to a hemispherical screen of radius R, simply placed on the ground. For the particular proportions of § 27, it makes the force under the hemispherical cage £ of the un- disturbed force outside. A cage of ordinary gardener's (anti-rabbit) hexagonal wire-net (of 5^ cm. from parallel to parallel) cannot be very different from this. If, instead of the radius being 50 cm. it be 200, bat the cage still of the same net, the force inside would be only Iper cent, of the undisturbed force outside. 32. In every case the force at any distance from the perforated surface, on either side of it, more than the diameter of a perforation, is, as is easily proved by Fourier's methods, very nearly the same as if the electricity were spread equably over the medial surface, with the same quantity per unit area of the medial as the grating has in each part of it. Hence, in the case of § 31, the force is uniform throughout the interior of the cage, except within distances from the net of two or three times the aperture. Hence a second screen, similar but slightly smaller, placed inside the first will reduce the force farther in the same ratio ; so that, if eX denote the force inside the single screen, the force inside the inner screen when there are two will be e2X, provided the distance between the two is nowhere less than the diameter of the perforation. Thus, with screens such as those in the last particular case of § 31, the force inside the inner screen would be only 9/10,000 of the undisturbed force far enough outside the outer. The two screens, if placed close together, so as to narrow the apertures as much as possible, would have little more than double the screening efficiency of either singly, as we may judge from (27) of § 26, and from (21) of § 14. The principle that, to duplicate a screen with best advantage, the two screens should be placed, not in one surface but in two, with not less distance between them than the diameter of their apertures, is not only theoretically interesting, but is of great practical importance in the screening of Jctrometers against disturbing electric force. 33. Questions analogous to those of §§ 26 — 32, but for circular cylindric (mouse-mill) cages of equidistant parallel bars, instead of the spherical or hemispherical cage which we have been considering, readily answered by the simpler work corresponding to that of 41* Sir W. Thomson. [Apr. , § 30 (with sin iO and cos t'0 instead of spherical harmonics). But it deserves more complete synthetic investigation, not limited by the approximntionftl conditions of §§ 21, 22, if for no other reason, because of Hertz's mouse-mill. This must, however, be reserved for a future communication. Meantime, it is worth saying that sudden variations of electric current, or alternating electric currents, distri- bute themselves between different straight parallel conductors in the same proportion as static electriBcation is distributed in corre- sponding electrostatic arrangements, whenever the suddenness, or the frequency, is sufficient to cause the impedance by mutual induc- tion of the separate parallel conductors (and therefore, a fortiori, tl impedance by self-induction of each) to be very large in compai with ohmic resistance. Hence Hertz's mouse-mill screening follow (though by utterly different physical action), simply the electrostatic law, except in any case in which his wave-length is less than a siderable multiple of the diameter of his mouse-mill. II. "On Variational Electric and Magnetic Screening." Sir W. THOMSON, P.R.S. Received April 1, 1891. 1. A screen of imperfectly conducting material is as thorough ii its action, when time enough is allowed it, as is a similar screen of metal. But if it be tried against rapidly varying electrostatic force, its action lags. On account of this lagging, it is easily seen that the screening effect against periodic variations of electrostatic force will be less and less, the greater the frequency of the variation. This is readily illustrated by means of various forms of idiostatic electro- meters. Thus, for example, a piece of paper supported on metal in metallic communication with the movable disc of an attracted disc electrometer annuls the attraction (or renders it quite insensible) a few seconds of time after a difference of potential is established and kept constant between the attracted disc and the opposed metal plate, if the paper and the air surrounding it are in the ordinary hygro- metric condition of our climates. But if the instrument is applied to measure a rapidly alternating difference of potential, with equal differences on the two sides of zero, it gives very little less than the same average force as that found when the paper is removed and all other circumstances kept the same. Probably, with ordinary clean white paper in ordinary hygrometric conditions, a frequency of alter- nation of from 50 to 100 per second will more than suffice to render the screening influence of the paper insensible. And a much less frequency will suffice if the atmosphere surrounding the paper is arti6cially dried. Up to a frequency of millions per second, we may safely say that, the greater the frequency, the more perfect is the annulment of 1891.] On Variational Electric and Magnetic Screening. 41 screening by the paper; and this statement holds also if the paper be thoroughly blackened on both sides -with ink, although possibly in this condition a greater frequency than 50 to 100 per second might he required for practical annulment of the screening. 2. Now, suppose, instead of attractive force between two bodies separated by the screen, as our test of electrification, that we have as test a faint spark, after the manner of Hertz. Let two well insulated metal balls, A, B, be placed very nearly in contact, and two much larger balls, E, F, placed beside them, with the shortest distance between E, F sufficient to prevent sparking, and with the lines joining the centres of the two pairs parallel. Let a rapidly alternating difference of potential be produced between E and F, varying, not abruptly, but according, we may suppose, to the simple harmonic law. Two sparks in every period will be observed be- tween A and B. The interposition of a large paper screen between E, F, on one side, and A, B, on the other, in ordinary hygrometric conditions, will absolutely stop these sparks, if the frequency be less than, perhaps, 4 or 5 per second. With a frequency of 50 or more, a clean white paper screen will make no perceptible difference. If the paper be thoroughly blackened with ink on both sides, a frequency of something more than 50 per second may be necessary; but some moderate frequency of a few hundreds per second will, no doubt, suffice to practically annul the effect of the interposi- tion of the screen. "With frequencies up to 1000 million per second, as in some of Hertz's experiments, screens such as our blackened paper are still perfectly transparent, but if we raise the frequency to 500 million million, the influence to be transmitted is light, and the kened paper becomes an almost perfect screen. Screening against a varying magnetic force follows an opposite aw to screening against varying electrostatic force. For the present, I pass over the cage of iron and other bodies possessing magnetic susceptibility, and consider only materials devoid of magnetic sus- ceptibility, but possessing more or less of electric conductivity. However perfect the electric conductivity of the screen may be, it has no screening efficiency against a steady magnetic force. But if the magnetic force varies, currents are induced in the material of the screen which tend to diminish the magnetic force in the air on the remote side from the varying magnet. For simplicity, we shall suppose the variations to follow the simple harmonic law. The greater the electric conductivity of the material, the greater is the screening effect for the same frequency of alternation ; and, the greater the frequency, the greater is the screening effect for the same material. If the screen be of copper, of specific resistance 1640 . cm. per second (or electric diffusivity 130 sq. cm. per second), and •h frequency 80 per second, what I have called the " mhoic effective 420 Sir W. Thomson. [Apr. 9, thickness "* is 0'71 of a cm. ; and the range of current intensity at depth n x 071 cm. from the surface of the screen next the exciting magnet is c~" of its value at the surface. Thus (as e3 = 20'09) the range of current-intensity at depth 2'13 cm. is -fa of its surface value. Hence we may expect that a sufficiently large plate of copper of 2£ cm. thick will be a little less than perfect in its screening action against an alternating magnetic force of frequency 80 per second. 4. Lord Bayleigh, in his "Acoustical Observations" (' Phil. Mag.,' 1882, first half-year), after referring to Maxwell's statement, that a perfectly conducting sheet acts as a barrier to magnetic force (' Elec- tricity and Magnetism,' § 665), describes an experiment in which the interposition of a large and stout plate of copper between two coils renders inaudible a sound which, without the copper screen, is heard by a telephone in circuit with one of the coils excited by electro- magnetic induction from the other coil, in which an intermittent current, with sudden, sharp variations of strength, is produced by a " microphone clock " and a voltaic battery. Larmor, in his pa on " Electromagnetic Induction in Conducting Sheets and Bodies" ('Phil. Mag.,' 1884, first half-year), makes the followi very interesting statement : — " If we have a sheet of conducting matter in the neighbourhood of a magnetic system, the effect of disturbance of that system will be to induce currents in the sheet such kind as will tend to prevent any change in the conformation the tubes [lines] of force cutting through the sheet. This follows from Lenz's law, which itself has been shown by Helmholtz and Thomson to be a direct consequence of the conservation of energy. But if the arrangement of the tubes [lines of force] in the conductor is unaltered, the field on the other side of the conductor into which they pass (supposed isolated from the outside spaces by the conductor) will be unaltered. Hence, if the disturbance is of an alternd^l character, with a period small enough to make it go through a cyok of changes before the currents decay sensibly, we shall have the con- ductor acting as a screen. " Further, we shall also find, on the same principle, that a rapi rotating conducting sheet screens the space inside it from all magnetic action which is not symmetrical round the axis of rotation." H Mr. Willoughby Smith's experiments on ° Volta-electric induc- tion," which he described in his inaugural address to the Society of Telegraph Engineers of November, 1883, afforded good illustrations of this kind of action with copper, zinc, tin, and lead, screens, and with different degrees of frequency of alternation. His result.- iron are also very interesting: they showed, as might be expected, paratively little augmentation of screening effect with augmen * « Collected Papers,' vol. 3, Art cii, § 35. „ 91. "I On Variational Electric and Magnetic Screening. 421 of frequency. This is just what is to be expected from the fact that broad enough and long enough iron plate exercises a large magneto- ,tic screening influence ; which, with a thick enough plate, will be nearly complete that comparatively little is left for augmentation of the screening influence by alternations of greater and greater frequency. 5. A copper shell closed around an alternating magnet produces a screening effect which on the principle of § 3 we may reckon to be little short of perfection if the thickness be 2^ cm. or more, and the frequency of alternation 80 per second. 16. Suppose now the alternation of the magnetic force to be pro- duced by the rotation of a magnet M about any axis. First, to find the effect of the rotation, imagine the magnet to be represented by ideal magnetic matter. Let (after the manner of Gauss in his treat- ment of the secular perturbations of the solar system) the ideal magnetic matter be uniformly distributed over the circles described by its different points. For brevity call I the ideal magnet sym- metrical round the axis, which is thus constituted. The magnetic force throughout the space around the rotating magnet will be the as that due to I, compounded with an alternating force of ich the component at any point in the direction of any fixed line ies from zero in the two opposite directions in each period of the rotation. If the copper shell is thick enough, and the angular velocity of the rotation great enough, the alternating component is almost annulled for external space, and only the steady force due to I is allowed to act in the space outside the copper shell. 7. Consider now, in the space outside the copper shell, a point P rotating with the magnet M. It will experience a force simply equal to that due to M when there is no rotation, and, when M and P rotate together, P will experience a force gradually altering as the speed of rotation increases, until, when the speed becomes sufficiently great, it becomes sensibly the same as the force due to the sym- metrical magnet I. Now superimpose upon the whole system of the | magnet, and the point P, and the copper shell, a rotation equal and opposite to that of M and P. The statement just made with refer- ence to the magnetic force at P remains unaltered, and we have now a fixed magnet M and a point P at rest, with reference to it, while the copper shell rotates round the axis around which we first sup- posed M to rotate. 8. A little piece of apparatus, constructed to illustrate the result experimentally, is submitted to the Royal Society and shown in action. In the copper shell is a cylindric drum, 1*25 cin. thick, closed nt its two ends with circular discs 1 cm. thick. The magnet is sup- ported on the inner end of a stiff wire passing through the centre of Herforated fixed shaft which passes through a hole in one end of DL. XL1X. 2 F - . 422 Sir W. Thomson. [Apr. the drum, and serves as one of the bearings ; the other bearing is rotating pivot fixed to the outside of the other end of the drum. The accompanying sections, drawn to a scale of three-fourths full size, explain the arrangement sufficiently. A magnetic needle out- side, deflected by the fixed magnet when the drum is at rest, shows a great diminution of the deflection when the drum is set to rotate. \ „ ? 91.] On Variational Electric and Magnetic Screening. 423 If the (triple compound) magnet inside is reversed, by means of the central wire and cross bar outside, shown in the diagram, the magneto- meter outside is greatly affected while the copper shell is at rest ; but scarcely affected perceptibly while the copper shell is rotating rapidly. < 9. When the copper shell is a figure of revolution, the magnetic force at any point of the space outside or inside is steady, whatever be the speed of rotation ; but if the shell be not a figure of revolu- tion, the steady force in the external space observable when the shell is at rest becomes the resultant of the force due to a fixed magnet intermediate between M and I compounded with an alternating force with amplitude of alternation increasing to a maximum, and ulti- mately diminishing to zero, as the angular velocity is increased with- rut limit. 10. If M be symmetrical, with reference to its northern and southern polarity, on the two sides of a plane through the axis of rotation, I becomes a null magnet, the ideal magnetic matter in every circle of which it is constituted being annulled by equal quantities of positive and negative magnetic matter being laid on it. Thus, when the rota- is sufficiently rapid, the magnetic force is annulled throughout e space external to the shell. The transition from the steady force of M to the final annulment of force, when the copper shell is symme- trical round its axis of rotation, is, through a steadily diminishing force, without alternations. When the shell is not symmetrical round axis of rotation, the transition to zero is accompanied with alter- ations as described in § 8. 11. When M is not symmetrical on the two sides of a plane through .e axis of rotation, I is not null ; and the condition approximated to ugh external space with increasing speed of rotation is the force e to I, which is an ideal magnet symmetrical round the axis of itation. 12. A very interesting simple experimental illustration of screening inst magnetic force may be shown by a rotating disc with a fixed et held close to it on one side. A bar magnet held with its netic axis bisected perpendicularly by a plane through the axis rotation would, by sufficiently rapid rotation, have its magnetic >rce almost perfectly annulled at points in the air as near as may to it, on the other side of the disc, if the diameter of the disc :ceeds considerably the length of the magnet. The magnetic force the air close to the disc, on the side next to the magnet, will be erywhere parallel to the surface of the disc. 2 F 2 424 Prof. W. E. Ayrton and Dr. W. E. Sumpner. [Apr. III. " The Measurement of the Power given by any Hl< Cnrrent to any Circuit," By W. E. AYRTON, F.R.! Professor of Applied Phywcs in the City and Guilds London Institute, and W. E. SUMPNER. D.Sc. Receive March 16, 1891. I. During the meeting of the Electrical Congress at Paris in 1881, one ns* devised a method of nsingan electrometer for measuring the po given to any circuit by any current. The accuracy of the method wholly independent of the nature of the circuit, which may self-induction, mutual induction capacity, and an E.M.F., as well as the nature of the current, which may be constant, intermittent, or al nating, according to any function of the time. This method is the onl electrical one published up to the present date the accuracy of whi is not based on assumptions, either as regards the nature of current or as regards the entire absence of self- and mutual indncti from a circuit some portion of which is necessarily of a solenoi form, or as regards the nature of the circuit the power given which we desire to measure. In view then of the present wide use of alternating currents industrial purposes, it might have been expected that this electro- meter method of measuring the power given by any intermittent or alternating current to an inductive circuit would have been extensively employed. Unfortunately, however, as pointed out by one of ns in conjunction with Professor Perry,f the use of this method is re- stricted by the fact that Sir W. Thomson's quadrant electrometers da not generally obey the mathematical law given for these instru- ments in text-book8,J as it was supposed they did when electrometer method of measuring power was first suggested. hence the main result that has, up to the present time, followed the publication of this method has been the stimulation of inventive minds to devise forms of electrometers in which the text-book law is strictly fulfilled. In 1888, Mr. Blakesley published a very ingenious method for using three dynamometers to measure the power given by an alternating * This method was simultaneously arrived at independently by Professor Fit*- gerald. t ' Journal of Soc. of Tel. Engs. and Elect*.,' vol. 17, 1S88. J We may mention that an investigation on Quadrant Electrometers has been going on from time to time at the Central Institution for the last five years, and we had hoped to have communicated the complete report long before this to the Boyal Society. L891.] Power given by any Electric Current to any Circuit. 425 tiu : urrent to the primary coil of a transformer. His original proof, a geometrical one, was based on various hypotheses, amongst others, that the primary and secondary currents and the magnetic flux were ine functions of the time. Recently, one of us, in conjunction with Mr. Taylor, has published* analytical proof showing that Mr. Blakesley's three dynamometer method of measuring power gives equally true results, whatever functions the currents and magnetic flux be of the time. There still owever, remains a serious objection to this method, viz., that it umes the absence of magnetic leakage in the transformer, or in ther words, that the number of lines of force embraced by one con- olution of the primary coil at any moment is the same as the number f lines of force embraced by one convolution of the secondary, iher, the three dynamometer method cannot be used to measure e power given to a single circuit, as the coils of one of the dynamo- eters have necessarily to be put in different circuits. The employment of an electromagnetic wattmeter for the measure- nt of electric power is well known, and investigators have con- idered the error that is introduced into wattmeter measurements de with alternating currents on account of the fine-wire circuit f the wattmeter possessing self-induction. This fine-wire circuit lually consists of a suspended coil in series with a so-called non- ductive stationary high resistance, and various devices have been opted by different experimenters to make the effective self-induction I this fine-wire circuit nought. One of the simplest of these devices e venture to think is that proposed by one of us in conjunction with T. Mather, and which consists in winding the stationary so-called on-inductive resistance in such a way that the capacity of this iubly-wound coil practically neutralises the effect of the self-induc- ion of the suspended coil. II. Several months ago, however, while working at alternate current iterference, we noticed that it was possible to employ an extremely iple method, based on the difference of phase of the P.D. and the irrent, for measuring the power by any current to any circuit. This lethod, which has since been in regular use in the laboratories of the Central Institution, is quite independent of any assumptions as to the iture of the current, or of the circuit, the power given to which it is lesired to measure, and it has the further great advantage that the )nly measuring instrument required is the ordinary alternate-current voltmeter of commerce. In series with the circuit ab (fig. 1), the power given to which we lesire to measure, connect a non-inductive resistance be of r ohms. * Meeting of Physical Society, February 27, 1891. 426 Prof. W. E. Ayrton and Dr. W. E. Sumpner. [Apr. FIG. 1. Let V}y F2, and V be the readings of the voltmeter when ap between a and 6, 6 and c, and a and c respectively ; then, if W be tl mean watts supplied to the circuit ab, we have in all cases, whatevt the nature of the current, or of the circuit^ ab — For, let Vi, vt, and v be the instantaneous values of the P.D. betwt a and b, b and c, and a and c at some moment /, then v = t'i + vt (2). r . If a. be the current in amperes flowing through the circuit at time f, then avj equals the watts w given to 06 at that time. But a = , r since the resistance be is non-inductive ; Then, squaring (2) we have — Consequently «* = ^T (f *«*- - !» or the equation given above. If the resistance of be be not known, or if there be any fear that it may be changed by the passage of the current, then an ammeter (an I 891.] Power given by any Electric Current to any Circuit. 427 alternate current ammeter, of course, if alternate currents be em- ployed) can be inserted in the circuit;. Let A be the reading of this ammeter, and which represents the square root of the mean square of e current, then, for r in (1) we may substitute VJA, or A w* (3). When employing this last formula, the non-inductive resistance may be that offered by incandescent lamps, since there is no objec- tion to the resistance varying with different mean strengths of the jurrent employed. This voltmeter method of measuring power was arrived at quite idependently of the electrometer method referred to above, but an lination of the electrometer method shows that it is practically mivalent to simultaneous measurements of three P.Ds. III. The method which we have described for measuring the power fiven by any current to any circuit may be conveniently employed for leasuring the power given to an alternating-current arc, or to an alter- iting-current arc-lamp. It is known that an alternating-current arc juires a greater current than a direct-current arc to produce the same jht with similar carbons; for example, a 10-ampere direct- current imp requires 12^ amperes, or 25 per cent, larger current, when used rith an alternating current. In a masterly paper on " The Theory Alternating Currents," read before the Society of Telegraph igineers, on November 13th, 1884, Dr. Hopkinson refers to a law fiven by Joubert, that the difference of potential between the carbons an alternating arc is of approximately constant numerical value iroughout the period, and that it reverses sign discontinuously at reversal of the current. Using this law as his basis, he works Dut mathematically some very curious relationships between the iriations of current and P.D. with time. Three of our senior students, Messrs. Kolkhorst, Thornton, and reekes, have been making a number of experiments on the power ipplied to alternating-current arcs by using the method of measur- ig power described above. From these experiments it would appear mt the quality of the carbon employed affects materially the differ- ice in phase between the currents passing through the arc and the J.D. between the carbons. If the arc be quite steady and only give )ut the rhythmic hum that accompanies a good arc, such as can be )btained with cored carbons of proper quality, the arc appears to it practically as a simple resistance, and M. Joubert's law does not lold. But if the arc be maintained between uncored carbons of poor 428 Prof. W. E. Ayrton and Dr. W. E. Sumpner. [Apr. quality, and be hissing, there is considerable difference in phs between the current and the P.D. between the terminals; further, the experiments show that current is very far from being a sii function of the time, although produced by a dynamo whose E.M.F. normally follows a harmonic law. We do not purpose, in this communication, to enter at length into these experiments on alternate-current arcs, but a few examples of the experimental results that hare been obtained will be interesting as illustrating the ready applicability of this new method of measur- ing power to such investigations. In addition to the difference of phase of P.D. and current that may be produced in the arc itself, there is the electromagnet to be con- sidered by which the distance between the carbons is usually regu- lated in arc lamps. This electromagnet will introduce lag betwt the P.D. at the terminals of the lamp and the current passii through the electromagnet and the arc in series ; and hence, evei although the arc be perfectly steady, we find, even in the case of Brush lamp especially intended for alternate currents, that the true power supplied to the electromagnet and arc is 20 per cent, less than the product of the readings of the ammeter and the voltmeter attached to the lamp terminals, and which gives the square root of the mean product of the squares of the current and P.D. If, however, the arc be between common carbons and be hissing, the difference, we find, is much greater. With cored carbons this Brush lamp requires a P.D. of about 35 volts to be maintained between its terminals, but if these cored carbons be replaced by common carbons and the arc be hissing, the P.D. between the terminals of the lamp at once rises to 45 or even 50 volts, although the current passing through the lamp and the amount of light given out remain practically as before. And then we find that the true power supplied to the lamp may be only one-half of the square root of the mean product of the squares of the current and P.D., so that the readings of the ammeter and voltmeter alone make the apparent power twice as great as the true power. For the purpose of easily estimating the ratio of the true to the apparent power supplied, formula (3) may be thus written, from which we see that the expression in the brackets represents the ratio of the true to the apparent power supplied to the lamp or othc circuit ab (fig. 1). Hence the percentage error made in assuming that the power supplied to any circuit was the product of the am- meter and voltmeter readings would be in all cases, whatever the nature of the current or of the circuit, L89.1.J Power given by any Electric Current to any Circuit. 429 100 v " ' "* 'J.\'_l *~V*+V) (5). The following are samples of Jthe results obtained with a hand- ilated lamp, there being no electromagnet at all in series with Fio. 2. ic arc (fig. 2). The carbons were not cored and the arc was hissing. The frequency was maintained at 200 periods per second. I Table I. Square root of mean square Percentage error in estimating power formula (5). Of P.D. in volts between Of current in amperes. a and b. rv b and c. r» a and c. V. A. 55-0 45-4 60-0 75-4 108-0 107-3 12-3 11-8 24-0 45-8 For the purpose of obtaining an idea of 0, the angle of phase lifference produced by the hissing arc, between the current and the 430 Prof. W. E. Ayrton and Dr. W. E. Surnpner. [Apr. 9, P.D., we may assume that the P.D. and current are sine functions of the time ; then, as may be easily proved, COS0 = and the values of 0 for the two tests given above come out as 40° 20' and 57° 10'. It will, of course, be observed that this assump- tion of a harmonic law for the P.D. and current for the purpose of obtaining some idea of the value of 0 in no way affects the generality of the method for the measurement of the power, since this is based on no such assumption. The following are samples of the results obtained with a Brush alternate- current lamp regulated by an electromagnet (fig. 3), the Fio. 3. ft egiJ la tiny Electro Magnet. Non Inductive Resistance. carbons not being cored, and the arc hissing. The frequency was maintained at 200 periods per second. 591.] Power given by any Electric Current to any Circuit. 431 Table II. Square root of the mean square' Percentage error in estimating power formula (5). Lag between current and P.D. Of P.D. in volts between Of current in amperes. a and b. z b and c. F3. a and c. F. <;>. 64-8 59-8 55-0 58-0 64-2 67-3 108-4 107-4 107-4 13-0 12-0 10-6 44-0 50-5 47-0 56° 0' 60 20 58 30 The experiments already described tell us that a hissing arc may cause a considerable phase difference between the P.D. and the current, but they do not enable us to decide whether such an arc causes the current to lag behind the P.D., or to lead in front of it. To decide this point, that is, to decide whether a hissing arc acts like an inductive coil, or a condenser, a variety of experiments were made by tting induction or capacity in series with the arc. The following ves the result of one such experiment : — In series with a hand- regulated lamp (and, therefore, containing ho electromagnet), was placed a condenser of 89 microfarads (fig. 4). Uncored carbons were used, and they were adjusted so that the arc was very short at first ; the carbons were then not touched, and, as they burnt away, the arc grew longer and longer until it finally went out. The fre- uency was maintained at 200 periods per second. FIG. 4. 432 . \V. K. Ayr-ton and Dr. W. E. Surapner. [Apr. 9, Table III. Square root of mean square Lag between Of P.D. in volU between Of current Sum of current and E.M.F. of in amperes. F.+ F,. P.D. dynamo a and b. b and r. a and c. in volts. 'V r,. r. A. *• f 35-4 89-0 72-3 12-0 124-4 129° CQ J 38-0 92-0 73-3 12-5 130-0 133 59 < 51-2 104-5 74-3 14-0 155-7 135 I 69-2 86-5 G7-5 13-4 155-7 131 Comparing V with the E.M.P. of the dynamo, we see that the arc and the condenser together acted as a condenser on the whole ; bat, comparing V with V\ + Ft, we see that the arc acted as an induction and not as a capacity. It having been conclusively proved that a hissing arc with uncored carbons acts as an induction, it was interesting to compare the im- pedance it produces with the impedance produced by the ordinary regulating electromagnet of the lamp. The arc itself seen in fig. 3 was, therefore, short-circuited, and the following measurements made, F! now being the square root of the mean square of the P.D. between the terminals of the regulating electromagnet, F» as before that between the terminals of the non-inductive resistance, and F that between a and c, the arc, as already explained, being short-circuited. The frequency was maintained at 200 periods per second. Table IV. 'V F8. F. A. 35-4 69-2 82-0 11-3 :(.-)• ; 65-6 80-0 11 4 We have, then, P.D. measurements giving the phase difference of current and P.D. with the arc alone (Table I and fig. 2) ; with the arc and regulating electromagnet (Table II and fig. 3) ; and with the electromagnet alone (Table IV). Defining impedance in the usual way as the ratio of the square root of mean square of P.D. to the square root of mean square of current, we find from the two sets of results given on Table I, that 1891.] Power given by any Electric Current to any Circuit. 433 {4'47 O.WQ ; )m the three sets of results given in Table II, that the impedance of the arc and electromagnet equals id from the two sets of results given in Table IV, that the impedance of the electromagnet alone equals. . < o.ie- In order to test whether the current follows a harmonic law, let assume that it does, then find what result this assumption leads , and, lastly, see whether the experiments confirm this result or not. Let, therefore, the instantaneous current at any moment be of the here r is the effective resistance in each case, viz., the ratio of the true watts given to the circuit divided by the mean square of the current in amperes, and where^> equals 2?rra, n being the number of periods per second. In each of the seven experiments referred to in 'ables I, II, and IV, n was 200. The seven values of r in ohms corresponding with the seven values the impedance given above are for the Arc alone J \ 3-42 2-07' 2-65 Arc and electromagnet 1 2' 66. 271 Electromagnet alone Lnd, since the impedance equals ^( le, the corresponding values of Lp are, for Arc alone fO-44 1 0-54' , if the harmonic law be J2-88 i 3-16' (-4-08 Arc and electromagnet 4. 4'41. [4-37 {3'12 s-iT* 434 Prof. W. E. Ayrton and Dr. \V. E. ISumpner. [Apr. 9, But if the harmonic law hold for the current, the sum of Lp for the arc alone, plus the Lp for the electromagnet alone, mast equal the Lp for the arc and electrpmagnet, since p has the same valiu- in case. Now it is obvious that the condition is far from being fulBlled with the numbers just given. Hence the current does not follow a harmonic law. It is interesting to notice that the Lp for the hissing arc alone is actually greater than the Lp for the regulating electromagnet. The values given above for r, being obtained by dividing the true watts by the mean square of the current in amperes, are the effective resistances in ohms — whether the current follows a harmonic law not. Hence, by comparing the value of r for the regulating ele magnet alone with its resistance in ohms, measured with a steady current, we have a true measure of the waste of energy in the iron core of the electromagnet due to hysteresis and Foucault cnrren Now the resistance of this electromagnet for a steady current is o 0'065 ohm ; hence 90 per cent, of the energy given to the regnlati electromagnet of this Brush' lamp is wasted in heating its iron core when the frequency is 200. Here again we have a further illustrati of the importance of being able to measure, by means of the simple method we have described, the power given by any current to any circuit. Added March 31, 1891. IV. The Best Value to give to the Non-inductive Resistance. In cases where great accuracy is required in the measurement of the power given to a circuit, it is important to consider what value should be given. to the non-inductive resistance (fig. 1), in order to reduce to a minimum any error that may arise from possible in- accuracies made in the three readings of the voltmeter, or on tb graduation of its scale. Since W = ^-(F2- F,1- F,«), dW = -(FdF-F^F,- r where dV, dV\, dVy are the errors made in the estimation of the three P.Ds. Let dV= ±eV dV, = ±eVl dVt = ±eVt Power given by any Electric Current to any Circuit. 435 where e is a small fraction, i.«., let the errors be each the same small raction of the correct value, then the probable value of 4 (FVF2+ V?#V?+ F22e2F22), d_ , ._4e2 s Ull * (72-F12-F2)2 Let the non-inductive resistance have such a value that F, = »Fi (8), 2 being already defined, the square root of the mean square of the .D. between its terminals, and VL the square root of the mean square the P.D. between the terminals of the circuit the power given to which we desire to measure. Then we wish to find the value of x that will make eZTF/TFa minimum. Let 0 be the angle of lag between the current in the circuit ac and .e P.D. at the terminals of ab (fig. ].), then 0 is the angle of lag between the P.D. at the terminals of ab and the P.D. at the terminals be. Hence, since i, and vz being the instantaneous values of the P.Ds., F2 = F12+F22+2F1F2cos0 (9). Eliminating F, FI, and F2 by means of equations (7), (8), and )), we have /dW\z _ 2 (l+a2+2a;cos0)2+l + a;4 \W) ~ 4352COS20 Now cos 0 depends on the circuit, the power given to which we sire to measure, and is independent of x. Hence differentiating nth respect to y and equating to nought in the usual manner, we id that x equal to unity makes a minimum. W Hence, inaccuracies in the three readings of the voltmeter, or in graduation of its, scale, produce the least effect in this method of sasuring power when the P.D. between the terminals of the non- iductive resistance is equal to the P.D. at the terminals of the circuit under test. The next point to consider is, what is the percentage error made in leasuring the power by this method compared with the percentage made in reading one of the P.Ds. Let x equal unity, then 436 Prof. W. E. Ayrton and Dr. W. E. Sumpner. ("Apr. 9, dW y/2 + 4(l+C080)3 W ~2e ~ 2C080 dW We ~~ co80 Now dW/We is the ratio of the percentage eiror made in measuring the power to the percentage error made in measuring one of the P.Ds. and the right-hand side of the last equation we find equals from 4 to 5 for the values of the lag angle 0 that occur ajj ordinary practice. If then there were a positive or a negative error of 1 per cent, in each of the measurements of F, Fi, and F2, tl would be a probable error of from 4 to 5 per cent, in the measure- ment of the power. The probable percentage error in the measure- ment of the power being from 4 to 5 times the error in the measurement of each of the P.Ds. arises partly from the fact tl the expression for IF, being depends directly on the difference in the mean squares of the P.Ds., and not on the difference of the square roots of the mean squares. And as all instruments that are graduated for measuring the square root of the mean square of an alternating P.D. such as a hot-wire voltmeter, an electrostatic voltmeter, ii force if the latter exceeds a certain minimum value. 9. The author has investigated these phenomena by means of cores constructed of iron wire (annealed) covered with insulatii material overwound with insulated copper-wire coils, the latter being wound in every case in a helix returning axially upon itself, so that the current in this copper wire should have null effect in directly generating any induced electromotive forces along the iron-wire core. 10. The effects obtained are considered by the author to be akin tn those obtained by Villari,* in 1865, by the mechanical agitation iron bars through which electric currents had been previously ps and, like the effects of Villari, to be due to the production and sul sequent disappearance of a circular magnetisation. They are akin to those observed by Hughesf with the induction balance. 11. The author has been able to imitate and reproduce these effe by th } use of copper wires immersed in iron filings, and surrounc by a magnetising coil wound so as to return axially upon itself. Presents, April 9, 1891. Transactions. Calcutta : — Asiatic Society of Bengal. Journal. Vol. LV! Parti. No. 3. 8vo. Calcutta 1890; Journal. Vol. L VI Part 2. No. 5. Vol. LIX. Nos. 2-3. 8vo. Calcutta 1890;' Proceedings. 1890. Nos. 4-10. 8vo. Calcutta 1890-1891. The So< Indian Museum. Catalogue of the Mantodea. No. 2. 8vo. Calcutta 1891. The Museum.' Cambridge, Mass. : — Harvard College. Annual Reports. 1889-90. 8vo. Cambridge 1891. The College. Museum of Comparative Zoology. Bulletin. Vol. XX. No. 8. 8vo. Cambridge 1891. The Museum. Edinburgh : — Geological Society. Transactions. Vol. VI. Part 2.' 8vo. Edinburgh 1890. The Society. Royal Society. Transactions. Vol. XXXIV (The Meteoro- logy of Ben Nevis). 4to. Edinburgh 1890. The Director, Ben Nevis Observatory. Essex Field Club. The Essex Naturalist. Vol. IV. Nos. 10-12. 8vo. Buckhurst Hill 1891. The Club. Heidelberg : — Naturhistnrisch-Medicinischer Verein. Verhand- lungen. Bd. IV. Heft 4. 8vo. Heidelberg 1891. The Society. • ' Poggendorff, Annalen,' vol. 126, 1865, p. 87. t ' Boy. Soc. Proc.,' Yol. 31, 1881, p. 631. L891.] Presents. 441 transactions (continued). Kew : — Royal Gardens. Bulletin of Miscellaneous Information. No. 51. 8vo. London 1891. The Director. Lausanne: — Societe Vaudoise des Sciences Naturelles. Bulletin. Vol. XXVI. No. 102. 8vo. Lausanne 1891. The Society. Leipsic : — Konigl. Sach. Gesellschaft der Wissenschaften. Abband- lungen (Math.-Phys. Classe). Bd. XVI. No. 3. Bd. XVII. No. 1. 8vo. Leipzig 1891. The Society. Liege: — Universite. Institut de Physiologie. Travaux du Labu- ratoire de Leon Fredericq. Tonielll. 8vo. Pam 1890. M. Leon Fredericq. London : — Aristotelian Society. Proceedings. Vol. I. No. 4. Part 1. 8vo. London 1891. The Society. Entomological Society. Transactions. 1890. Part 5. 8vo. London. The Society. Odontologicat Society of Great Britain. Transactions. Vol. XXIII. No 4. 8vo. London 1891. The Society. Photographic Society of Great Britain. Journal and Trans- actions. Vol. XV. No. 5. 8vo. London 1891. The Society. Royal United Service Institution. No. 157. 8vo. London 1891. Society of Antiquaries. Proceedings. London [1891]. Society of Biblical Archaeology. Part 4. 8vo. London 1891. Manchester : — Geological Society. Transactions. Vol. XXI. Parts 2-5. 8vo. Manchester 1890. The Society. Journal. Vol. XXXV. The Institution. Vol. XIII. No. 2. 8vo. The Society. Proceedings. Vol. XIII. The Society. New York : — Academy of Sciences. 8vo. New York 1890. Vol. 5. 1890; Transactions. Vol. IX. 1889-90. Annals. Vol. IV (Index). Nos. 4-8. 8vo. New York Nos. 3-8. 8vo. New York The Academy. Paris: — Ecole Normale Superieure. Annales. Annee 1890. No. 12. 4to. Paris. The School. Societe Philomathique. Bulletin. Tome II. No. 4. 8vo. Paris 1890. The Society. Philadelphia : — Academy of Natural Sciences. Proceedings. 1890. Part 3. 8vo. Philadelphia 1891. The Academy. Bell (R.) On Glacial Phenomena in Canada. 8vo. Washington, 1890; The Nickel and Copper Deposits of Sudbnry District, Canada. 8vo. Rochester 1891. The Author. 442 Pretent*. Benndorf (0.) Das Heroon von Gjolbaschi-Trysa [in continuatioi 4to. [1891.] The Author, through the Austro-Hnngarian Eml Burd«tt (H. C.) Burdett's Official Intelligence for 1891. London. Mr. Bnrdi Bnrggraeve (Dr.) La Societo de Medecine de Gand et la Medecii Dosiiiu'trique. I.-:i I ;'t 1 -*9. 8vo. Paris 1891. The Author, through Dr. T. L. Phi] Dawson (Sir J. W.), F.R S. On Fossil Plants from the Similkam< Valley and other places in the Southern Interior of British Columbia. 4to. [Montreal] 1890. The Author. Harris (J.) The Laws of Force and Motion. 4to. London II The Autl Hull (E.), F.R.S. Our Coal Resources. 8vo. [Edinburgh] II With two other Excerpts in 8vo. The Autl Hnyghens (C.) (Eurres Completes de Christiaan Huygens. T( III. 4to. La Haye 1800. Societe Hollandaise des Sciences, Harli Sprengel (H.), F.R.S. The Origin of Melinite and Lyddite (Pic Acid). 12mo. London 1890 (two copies); The Origin of Mel nite and Lyddite- (Reprinted from The Times). 12mo. [London 1890. The Anl On the Causes ivhic/i produce the Phenomena of Neic Stars. 443 April 16, 1891. Sir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read : — "On the Causes which produce the Phenomena of New Stars." By J. NORMAN LOCKYER, F.R.S. Received November 28, 1890. (Abstract.) In communications to the Society during the last four years, I lave produced evidence to show that many so-called stars are com- )osed of swarms of meteorites, and are increasing their temperature. Taking a normal case of an undisturbed swarm, 1 have shown, by leans of a " temperature curve," the spectra given by the same mass )f meteorites in its evolution from a nebula to a condensed and nearly )ld body. In considering this question, the appearance of the so- called " New Stars " was referred to, and it was suggested that such ippearances might be due to the collision of meteor-swarms or streams in space, an idea which I first put forward with regard to Tova Cygni in 1877. It became obvious that a complete discussion of these phenomena rould afford a valuable test of the general hypothesis, for the reason that such bodies, instead of going forward along the temperature curve, should go back aa they cooled and became invisible. All the observations have, therefore, been brought together and liscussed from this point of view, the investigation having special eference to the sequence of spectroscopic changes from the first ippearance of a new star to its final disappearance. The various theories which have been put forward since the appear- ice of the new star of 1572 are referred to in the paper, and these ire followed by a general statement of the meteoritic theory of the origin of new stars. The remaining part of the paper consists of a letailed discussion of all the observations of new stare which have 2en made, and the final result is a complete justification of the con- clusion arrived at from the first survey that " new stars, whether seen in connexion with nebulae or not, are produced by the clash of leteor-swarms." Some of the chief points may be referred to here. lit Mr. .1. Norman Lockyer. On the Causes [Apr. M, The investigation has shown that there is a close relation between the spectra of comets and the spectra of new stars, but whereas in comets only one swarm has to be considered, in new stars there air two s warms which may or may not be equally dense or of c«|iutl dimensions. The spectrum of a new star is therefore a compound one. We have, in fact, a mixed radiation and absorption spectra similar to that presented by a variable like Mira Ceti when at it.-, maximum brilliancy. In another paper I have shown that variables of the Mira type are really double swarms, and hence the conclusion that the difference between this class of variables and new stars is only a difference in the orbits of the subsidiary swarms. Omitting Nova (U) Orionis, which proved to be only a long period variable, ouly three new stars have been spectroscopically observed ; namely, Nova Corona) (1866), Nova Cygni (1876-77), and No Andromeda (1885). In Nova Coronae, when first observed, a spectrum of bright lines was superposed upon one of dark Hues. The absorption phenomena were similar to those characteristic of stars like * Orionis, and the chief radiation was that of hydrogen. A discussion of the observa- tions suggests that two of the ill-defined lines in the blue may have been due to carbon. In the discussion of cometary phenomena which I have previously communicated to the Society, I pointed out that in many cases the blue band appeared to have two maxima, one at A, 468 and one at X 473, and it is more than probable that the two lines of the Nova were identical with those of comets.* In comets, the blue band, whether single or double, is generally admitted to be due to carbon, from its association with the undoubted carbon band in the green, and the same origin is therefore probable in the case of the Nova. Whatever the origin of the two lines in Nova Coronoe, the fact of their being common to comets and a new star is the point I am anxious to bring out. The F line was recorded throughout the whole period of observation, and another bright line, apparently coincident with the chief nebula line, w recorded by Messrs. Stone and Carpenter. The suggestion that a new star is produced by the collision of two meteor-swarms or streams is fully borne out by the discussion of the observations of Nova Coronae. The mixed phenomena of absorption and radiation which were obsei-ved are simply and sufficiently ex- plained on this supposition. An attempt is made in the paper i» * Note, April 4. — The band in question is also probably identical with the one seen in some of the stars of the \Volf-Ra\et type. Dr. and Mrs. Uuggins ha>r recently made observations of some of these stars which have led them to conch that the oand is not due to carbon (' Roy. Soc. Proc.,' vol. 49, p. 3d). I am not convinced on this point, but I shall take another opportunity of replying to their remarks. L89L] which produce the Phenomena of New Stars. 445 iow that the spectrum of the Nova can be reproduced by integrating the spectrum of a comet at a certain temperature, and a nebula of a ertain degree of condensation. The resulting spectrum differs only irery slightly from that of the Nova, and the differences can be 3counted for by difficulties of observation. Nova Cygni is by far the most important new star which has ippeared in spectroscopic times. Numerous observations were made, ind they are, on the whole, in reasonable agreement. The most >mplete observations were made by Vogel. When first observed, the spectrum consisted of several bright lines and flutings, the lines of hydrogen being very conspicuous. As the star gradually faded away, there was a general diminution in the number and brightness of the lines, but the most striking feature was the brightening of the line in ic green, near X 500, which is generally accepted to be the nebula le, as the other lines faded. Finally, the spectrum consisted solely jf the line 500. The discussion indicates that, in addition to hydrogen, icre was the radiation of carbon vapour, the flutings seen being those are most frequently observed in comets. They are, however, lodified by the superposition of the spectra of other substances, tactically all the lines and flutings seen in the spectrum of Nova }ygni can be explained by reference to laboratory work at low tem- sratures. As in the case of Nova Coronse, the spectrum of Nova /ygni can be reproduced by integrating the spectra of bodies which re have reason to believe are swarms of meteorites. Several examples of this are given in the paper. In the earlier stages, it is necessary integrate the spectra of at least three swarms of different degrees condensation, but as the spectrum became simpler, two are suffi- cient. The compound origin and character of the spectrum of a Tova is thus clearly indicated. It is not to be supposed from these itegrations that in the first instance there are really three or more swarms engaged. A Nova is probably produced by the collision of ily two swarms, but the resulting mixed swarm is so complicated lat we can only represent it by assuming at least three temperature jnditions. There will be the temperatures corresponding to each of the central condensations, and that corresponding to the outliers. As le swarm cools, the temperature becomes more equal throughout, and lally the swarm resembles a planetary nebula. The spectrum of Nova Andrornedee was at no time a very striking le, and was always difficult to observe. It was also further compli- ited by being superposed upon the then imperfectly recognised actrum of the Great Nebula, in which it was involved. The jectrum was almost continuous, with brighter portions here and lere, which could only be measured with difficulty. Consequently, results obtained by different observers are somewhat discordant, ["he discussion shows that what was really observed after the star had 446 On the Phenomena of Arfir -S' [Apr. 16, faded was nothing more than the spectrum of the nebula itself, as might be expected. Owing to the difficulty of making the observa- tions, the apparent variations of the spectrum from day to day may not be real, and it is hopeless to attempt to explain them by a reference to the effects produced by a gradual fall of temperature. As the star only fell two magnitudes during the whole period of spectro- scopic observation, the change of temperature would not be so great as in Nova Cygni, and the variations would not be so well marked. No lines or bands, however, were on any occasion recorded in the spectrum with which we are not familiar in other bodies which, there is evidence to show, are meteoritic swarms. A diagram shows that the spectrum of the Nova, as seen by Copeland, on October 1, can be reproduced by adding the spectrum of hydrogen to that of the nebula. It is next pointed out that the theoretical sequence of phenomena in the spectrum of a Nova produced by the collision of two swarms of different densities is in strict accordance with the partial sequences actually observed. A discussion of the colour phenomena shows also that in Nov» we have to deal with mixed swarms, the colours at certain stages being compound ones. In my former paper, I have shown that carbon radiation is one of the chief characteristics of uncondensed .meteor-swarms, and the dis- cussion of the new stars has revealed the fact that carbon is also one of the chief characteristics of their spectra, though modified by other substances. The observed changes in magnitudes of Novae are also in accord- ance with the collision theory. The rapid fading away demonstrates most conclusively that small bodies, and not large ones, are in ques- tion. The observations with which I have had to deal have often been imperfect, owing to the difficulty of observing 'this class of bodies, and different observers have frequently disagreed with regard to some of the spectroscopic details, but still, as I have endeavoured to show, most of the discrepancies can be reconciled when difficulties of obser- vation are allowed for. L891."| On the Adialatic Relations of Ethyl Ox'ule. 441 [I. u An Attempt to determine tlie Adiabatic Relations of Ethyl Oxide. Part I. Gaseous Ether." By W. RAMSAY, F.R.S.. Professor of Chemistry in University College, London, and E. P. PERMAN, B.Sc. Received March 16, 1891. (Abstract.) The object of the research described in the memoir is the determi- lation of the behaviour of ether in the state of gas approaching >wards the state of liquid, when heat is communicated to it, so as to Iter its condition adiabatically. Previous researches by one of the authors in conjunction with )r. Sydney Young have yielded data regarding the relations of pressure, temperature, and volume of gaseous and of liquid ether rom which tt e values of the isobaric and of the isochoric differentials ire obtainable. Such results lead directly to a knowledge of the lifferences between the specific heats at constant pressure and those it constant volume ; and these differences are not constant, but vary rith varying volume, pressure, and temperature. The memoir contains an account of experiments made to determine the ratio between the specific heats at constant pressure and those at jnstant volume. The velocity of sound in gaseous ether was letermined at various temperatures, pressures, and volumes; and by leans of the isothermal differentials, and the experimental results for the velocity of sound, the ratios between the two specific heats rere calculated. From the differences and the ratios of the specific icats, the values of the specific heats were deduced. The general conclusion is that, for any constant volume, the specific leat, whether at constant volume or at constant pressure, decreases a limiting value with rise of temperature, and subsequently icreases ; and that the change with temperature is more rapid, the laller the volume. At large volumes, the specific heats tend towards independence of jrnperature and volume, while at small volumes, the influence of ihange of temperature and volume is very great. The authors are at present investigating similar relations for liquid sr. 448 Prof. \V. X. Hartley. Pluuical Character* of the [Apr. 1 III. "On the Physical Characters of the Lines in the Spt Spectra of the Elements." By W. N. HARTLEY, F.U.," Professor of Chemistry, Royal College of Science, Dubl Receivea .M.-m-h 18, 1891. The properties of the atoms are a periodic function of the masses, and the physical characteristics of the spectra of the eleiuei appear to be an expression of the properties of the atoms ; for th is undoubtedly an intimate connexion between the rays emitted the self-luminous vapours of the elements and their chemical physical properties. If we photograph the spark spectra of thirty or forty of elements and arrange the spectra in groups following the perk law, the arrangement will be seen to be a perfectly natural one. Tl observation applies not only to the groupings of the lines, but also the physical characteristics of the individual lines. In spark sj the three most striking characteristics are (1) an extension of cei lines above and below that part of the spectrum bounded by points of the two electrodes ; (2) the nimbus which surrounds extremities of the lines, even to some extent those portions whic form an extension ; and (3) the continuous spectrum which forms background to the lines. (1.) On the Extension of the Lines. — The spark discharge, as shown by Perrot, is composed of two parts, of which the fiery track, or central portion, is a statical discharge, and the aureole, or flame, is dynamical, and capable of electrolytic action. From careful observation of the sparks, and photographs of spectra, I have come to regard all those spectra with lines extended as spectra of different discharges taken simultaneously. The principal lines lying between point and point of the electrodes are spectra the fiery path of the spark ; the extension of the principal lines aboi and below the points of the electrode appear to be spectra of aureole. The principal observation which leads to this conclusion is that the electrodes are seen to glow silently and continuously abo> and below the points of the upper and lower electrodes, and frequentlj slight roughnesses present the appearance of brightly but steadilj shining dots ; particularly is this the case with those metals whic exhibit the most extended lines, as for instance, cadmium, thalliut and indium. The lines in many spectra are free from this extension and no glow is observed on the electrodes. A study of about tl different spectra of the metals and semi-metallic substances has to the following observation. Elements which are difficult to volatilise, and those which are lad ductort of elect. ~icityt do not exhibit tpectra with extended lines; and, con- Lines in tJte Sj>arl Spectra of the Element*. 449 rersely, metals which are the best conductors and the most volatile exhibit spectra with their principal lines largely extended. The following metals are good conductors, that is to say, suffi- ciently good not to impede the spark when broad electrodes are used, and they are more or less volatile. They show a large extension of eir principal lines : — Boiling point. Atomic mass. Volatility. Atomic mass. Magnesium. . Zinc ....... 1100° C. 924° to 24-4 65-3 Aluminium. . Not volatilised by ordinary means. Volatilised at a 27-08 113-7 Cadmium . . . 954° C. 763° to 772° C. 112-1 Thallium.... red heat. Easily volatilised at a red heat. 204-2 Atomic mass. Copper Not volatilised by ordinary means. . 63'33 Silver Boils about 1570° C 107'93 Mercury „ 357° C 200'1 In these examples the extension of the lines is least in the case of the least volatile metals, which are also those of least atomic mass, ind it is greatest with those which are most volatile and of greatest 3m ic mass. The continuous spectrum in these examples is very weak, and the iir lines are almost absent from the thallium and mercury spectra, air spectra being suppressed by the excess of dense vapour in the rack of the spark. The lines most extended are the following : — In , • ^ cadmium spectrum, those with wave-lengths 3611 '8, 3609'6 (a pair), 3466'8, 3465-4 (a pair). These pairs appear as single lines the dispersion is insufficient and the definition imperfect. The most refrangible line of each pair is the more extended. The rther lines in this spectrum are 3402'9, 2747' 7, 2572'2, 2313'6, and 265*9, all with fine extensions. In the spectrum of thallium, wave- sngths 3775-6, 3528'8, 3518'b', and 29177. In the spectrum of mercury, the Hues with wave-lengths 4358, 1)6-5, and 3984 are well extended, but the most important exten- sions in this spectrum are the lines with wave-lengths 3662'9, 3654'4, J2'9 ; the last of these, which form a well-marked triplet, is by far most extended. The pair of lines 3130'4 and 3124'5 are greatly extended, and the same remark applies to 2966'4 and 2946'6. The dimensions of the principal lines in the cadmium, thallium, 450 Prof. W. N. Hartley. Physical Character* of the [Apr. Ifi, and mercnry spectra were measured on my enlargements. The prin- cipal portion of the lines lying between point and point of the elec- trode was 42 mm. in all spectra. The extension of the lines below wait 22 mm. to 25 mm., extension above, 9 mm. to 10 mm. As the exten- sion is always sharp and well deBned, it is an important feature in these spectra. Even concentrated solutions of the metal?, when photo- graphed with graphite electrodes, exhibit this extension in their principal lines. For instance a solution of beryllium chloride shows a very remarkable extension above and below the points of the upper and lower electrodes ; the dimensions of the principal line, wave- length 3130'2, are as follows : between the points, 42 mm. ; below, 10'5 mm. ; above, 17'5 mm. It is at the upper or positive electrode that the longest extension is observed, but at the lower or negative electrode that it is strongest. In the case of the cadmium lines, the extension is smaller, but strong at the side of the negative electrode, and very fine and long at that of the positive.* The appearance lines due to impurities or traces of metals in the spectrum of the negative electrode only, I have attributed to the oscillation of the spark discharge, and the fact that the negative electrode is the hotter, f (2.) The Nimbtis. — The nimbus is not apparently dependent on the volatility or the oxidisability of the vapour of the elements, though these properties are connected therewith. By far the largest nimbus is that of magnesium ; those of cadmium and mercury stand next in order ; the smallest are those of platinum, gold, copper, and silver. It is thus evident that neither conductivity nor vapour density controls it, for there is very little nimbus on the lines of the thallium and iridium spectra; but volatility certainly increases it. There is a considerable nimbus on some of the lines in the spectra of arsenic, antimony, and bismuth ; also on a few lines of tin and of lead. In the case of magnesium, the cause of the dense and large nimbus is probably the intensity of the chemical action of which the rays of the incandescent vapour are capable, together with the large quantity of metal in the track of the spark, owing to its volatility. The chemical activity of the zinc rays is less than that of the rays of magnesium, but the effect of this is overbalanced by the density of the vapour and the volatility of the metal being both greater ; accordingly the lines of zinc have a large nimbus. The nimbus is somewhat larger on the lines of cadmium than on those of zinc, the volatility and the density of the vapour are both greater. * In a paper published in the ' Scientific Proceedings of the Royal Dublin Society,' on the constitution of electric sparks, this does not appear in the litho- graphed illustration, but I have carefully verified the fact by referring to the original photographs. f Loc. cit., p. 373. 1891.] Lines in the Spark Spectra of the Elements. 451 tThe nimbus is evidently an expression of the quantity of matter the spark, and the intensity of the chemical action which the rays emitted by its ignited vapour are capable of exerting. (3.) On the Continuous Spectrum which forms the Background to the Lines of certain Spectra. — This must be caused by the ignition either of some solid substance or of a vapour which is not that of an element but an oxide. An examination of the spectra in which the continuous background of rays is a conspicuous feature discloses the fact that the metals which are not oxidisable do not possess it, for instance, gold, silver, and platinum. Metals of the iron group show it near the points of the electrodes when the non-volatile oxides are formed. The very volatile metals with volatile oxides, such as mercury, iridium, thallium, zinc, and cadmium, do not show it. I Spectra of the metalloids, such as tellurium, arsenic, antimony, and bismuth, which are not only volatile but which form volatile oxides, show it very strongly. Ordinarily, magnesium does not show it, because the exposure necessary for photographing the spectrum of that element is less by one-half the period of the others, and by one- quarter that of tellurium. When a plate is long exposed to the rays of magnesium, the continuous spectrum appears at the points of the electrodes where the non-volatile oxide would be formed. It may be considered that in the passage of the spark, the vapour of the element fills the track, and this vapour, on cooling, forms, for a minute period of time, an incandescent oxide, and, the spectrum of this being a, continuous spectrum, its photograph appears as a back- und to the rays emitted by the element. But it is nevertheless the fact that the continuous background a very characteristic feature of the metalloids, though why the pours of these oxides should produce this action more conspicu- ously than those of the oxides of the volatile metals, there seems to no sufficient or well-understood reason to be advanced at present, may be that the vapours of the metalloids in cooling emit a con- ons spectrum for a short period prior to oxidation. On the Breadth of Lines. — It is well known that, under identical nditions, the principal lines in the spectrum of an element become >nger and broader as the rays forming the spectrum proceed from larger quantity of material, that is to say, form a denser radiating ,yer. It is evident, then, that in any series of three or more ments of similar character, the intensity and the breadth of the es in their spectra will depend upon (1) intensity of chemical ergy, (2) volatility and vapour density, and (3) electric conduc- vity of the metal. In accordance with these conditions, the lines of cadmium are >ader than those of zinc, aud the lines of zin ; broader than those •magnesium. Present*. [Apr. Presents, April 16, 1891. 'ransactiona. Batavia : — B itaviaasch Genootschap van Kunsten en Wetonsc pen. Notulen. Deel XXV11. Aflev. 4. Deel XXVIII. Aflev. 1-2. 8vo. Batavia 1890; Tijdschrift voor Indische TaaU, Land- en Volkenknnde. Deel XXXIII. Aflev. 1, 5-6. Deel XXXIV. Aflev. 1-2. 8vo. Batovia 1889-90 ; Plakaat. boek, 1602-1811. Deel VII. 8vo. Batavia, 1890. The Society. Berlin :— Gesellschaft fUr Erdkunde. Verhandlungen. Bd. XVI No. 2. 8vo. Berlin 1891. The Socie Physikalische Gesellschaft. Verbaudlungen. 1890. 8vo. BerU\ 1891. The Society. Beziers : — Societe d' Etude des Sciences Naturelles. Compte-Rem des Seances. Annee 1888-89. 8vo. Beziera 1890. The Society, Briinn — Naturforschender Verein. Verhandlungen. Bd. XX VIII 8vo. Briinn 1890 ; Bericbt der Meteorologischen Commi sion des Naturforschenden Vereines. 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Henri de Saussure April 23, 1891. 5ir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. The Presents received were laid on the table, and thanks ordered them. The following Papers were read : — "Contributions to the Chemical Bacteriology of Sewage." By Sir HENRY E. ROSCOE, F.R.S., D.C.L., LL.D., and JOSEPH LUNT, B.Sc., F.C.S. Received April 23, 1891. (Abstract.) The present research contains the results of experiments on the emical and bacteriological examination of sewage micro-organisms, ade with the object, in the first place, of ascertaining what species are there present, and, in the second, of determining some of their emical characteristics. The authors have isolated from crude sewage, by methods which are fully described, a number of organisms which may serve as typical examples of those usually present in this material. Some of these have already been described, whilst others are believed to be Iw organisms. The microscopic and macroscopic appearances of the organisms and their pure cultures have been carefully recorded by means of photo- graphs, which give in a permanent form their morphological characters and the plate- and tube-cultivations in their most characteristic stages of growth. This method of illustration the authors consider to be of much importance, as bacteriological descriptions of organisms are frequently of little value for the want of accurate representations of microscopic preparations and pure cultures. The experiments described were undertaken with the object of studying the reactions of sewage organisms from a chemical point of iew, and of gaining information as to the rationale, both chemical 2 H 2 * - 456 Sir H. E. Roscoe and Mr. J. Lunt. [Apr. 23r and bacteriological, of the two marked changes which sewage is liable to undergo, i.e., on the one hand purification, or the gradual destruc- tion of putrescible matter without the formation of offensively smell- ing products, and on the other putrefaction. It was desired to ascertain which organisms are concerned in the first of these processes and which in the second, as likewise to gain an insight into methods by which such changes are effected. For all the organisms described, the authors have determined tl absorptive power for free oxygen when cultivated in a perfectly pure state, and also for which of the organisms free oxygen is a necessity of their activity and growth. Each organism has been examined as to its power of growth in liquid medium from which every trace of free oxygen, both and dissolved, has been rigorously excluded. It is shown that anaerobic organisms associated with putrefactioi although able to grow in complete absence of oxygen, yet when that gas is present are able to absorb it rapidly, and thus prepare the con- ditions for their anaerobic growth. The following methods for the isolation of micro-organisms ha been used : — (1.) The method of gelatine plate-culture. (2.) A method, fully described, for the isolation and cultivation anaerobic organisms. (3.) A method for the isolation of spore-forming organisms. (4.) The dilution method. The method used for the isolation of anaerobic organisms coi in their cultivation in a specially devised form of flask contaii sterile nutrient broth, through which liquid could be passed a stream or pure hydrogen, freed fi-om all traces of oxygen by passing ove glass beads, in two Emmerling's tubes, moistened with alkaline j gallate. As the authors have shown in a previous paper (' Chera. Journ.,' 1889, Trans., p. 554), this treatment frees the liquid coi pletely from dissolved oxygen. Crude sewage was carried through three cultivations in pi hydrogen, when it was found that not only had all aerobic organis been eliminated, but only one form of anaerobic organism appeal viz., Proteus vulgaris, and this method may be used for its isolation. Several other organisms, although isolated by different methods the above, were found to grow in the pure state in nutrient broth from which all traces of free oxygen had been excluded. These ai fully described in the paper. In the method for the isolation of spore-forming organisms, all others were eliminated by heating the sterile broth, in which sowing had been made from crude sewage, to 80° C. for ten minutes. • 91.] Contributions to the Chemical Bacteriology of Sewage. 457 The still living spores were then further isolated by plate cultivation, ither with or without previous incubation of the broth tube. For the purpose of studying the absorptive power for free oxygen, pure cultures were sown in sealed flasks with two necks, containing 25 c.c. of nutrient broth and 250 c.c. of air. These were incubated at 20 — 23° C. for seven days, after which time the flasks were opened and the gases remaining abstracted for analysis. It was seen that the various organisms exhibited great differences in their absorptive power for free oxygen, some showing the feeblest absorption, whilst others, abstracted nearly every trace of oxygen from an atmosphere ten times as large as the culture liquid during seven days' incnba- -, w Ihe rate of absorption of dissolved oxygen was also determined for a number of the organisms by sowing tap- water aerated under known inditions, and containing a definite amount of dissolved oxygen, ith 1 per cent, of a pure broth culture of the organism which had been cubated for two days after sowing. It is shown, in the case of ose organisms which absorb oxygen rapidly from the air, that the ater is completely de-aerated in fourteen hours. It is shown that certain organisms which are capable of growing in atmosphere devoid of oxygen, i.e., anaerobic, are yet incapable of iquefying gelatine without the presence of that element, although when grown in air such liquefaction is extremely rapid. Cultivations were made in the form of flask referred to for .naerobic organisms, in which the organisms were sown in molten gelatine, through which pure hydrogen was passed for half an hour. The flask was then sealed. After five days' incubation, no liquefaction hatever took place, although, when exposed to air, the normal rapid quefaction of the gelatine afterwards occurred. It is also shown, both in the case of aerobic and anaerobic organ - ns, that a very appreciable diminution of the liquefying power of Tganisms takes place after repeated sub-cultivation in nutrient latine. The method employed for photographing the micro-organisms is also escribed. In all cases the bacteria were stained with methyl violet, >ut, as this stain transmits chemically active rays, it was necessary, order to obtain actinic contrast, to use a coloured screen and iso- matic plates. The screen adopted (a weak solution of potassium ichromate) was spectroscopically adjusted to the stain employed, so at the objects appeared black on a bright yellow background. The iparatus employed was of the simplest kind, and the source of illu- ,tion was a common duplex paraffin lamp. The organisms isolated from the sewage under examination are escribed and illustrated photographically, as regards microscopic reparations and plate- and tube-cultures. 458 Mr. A. Mallock. Instability of India-rubber [Api II. " Note 011 the Instability of India-rubber Tubes and Balloons when distended by Fluid Pressure." By A. MALLC Communicated by LORD RAYLEIGH, Sec. R.S. Receive March 16, 1891. When an india-rubber tube is expanded by internal fluid present it preserves its cylindrical fom> until the increase in its diamett bears a certain proportion to its diameter when unstrained ; but, whe more fluid is introduced, the condition of the tube becomes unstabl and the internal fluid pressure diminishes. When more fluid, therefore, is introduced into a length of tnl than will suffice to expand it to its stable limit, it no longer rei cylindrical throughout its length, but assumes the form of a cylindt with one or more bulbous expansions ; and the diameter of the which remains cylindrical, though greater, of course, than the ui strained diameter, is less than that attained at the stable limit ii fig. 1. FIG. 1. In the case of an elastic hollow sphere, although the spheric form is retained, whatever be the amount of fluid introduced, there ifi a similar limit to the pressure which the elastic reaction of its can cause within it. If the thickness of the walls of the tube or sphere is small ooi pared with the radius, and if, further, the material of which they composed be considered as incompressible, while the other elastic constants are invariable for such extensions as are involved (assnmj: tions which are approximately true for india-rubber), the value of the radius when instability begins, may readily be found. Taking &c, cy, £z as the sides of any small cube of the material of the walls, (x and ?y being parallel to the tangent plane of the surface and 2f normal to it, let a stretching force act in the direction of x causing &» to become pSx. Since the material is incompressible, £y and £:, under the influence of this force, will become respectively (l/v'jOfy and L891.] Tubes and Balloons distended by Fluid Pressure. 459 Now, maintaining this force, let another stretching force act in the lirection of y, which would, if acting alone, stretch By to icSy. Then p £e will become -¥— dx ; The force required to stretch &e to p $x is = q dy &u K id that required to stretch — f- to — j-Sy is vp vp = q v/p dx dz, rhere q is Young's modulus for the material. In the case of the cylinder, if x be taken parallel to the axis of the cylinder and y round its circumference — J<$a; = unstrained length of cylinder = Z0 ; j&y = „ circumference „ = 27rr0; \Bz = ,, thickness ,, = t0 ; lence the whole elastic circumferential stress is K— 1 y« = Q V p ZQ £<)) • id the fluid pressure, P, due to this stress is l / i Vp 10 P = 27r */p */ 1 27rg*0 K— 1 To Ktf K ?his is a maximum when K = 3. 460 Mr. A. Mallock. Instability of India-rubber [Apr. L'.'>. Since P is also equal to F* -r- strained area of base of cylinder, ^H- /„ T,, ,, •* J I/O *• 4ir p and by equating this to the former expression, we have for j> in terms of *, _ v/*0-i) + 2 * ' 2 So that, when K = 3, p = ^/3 + l. From this it will be found that the critical value of the radius is 1-815 TO, and that then the length of the tube is T58 10 nearly. In the case of the sphere the maximum pressure will also be attained when ic = 3, but, since by symmetry p now = *, we shall have for the critical value of the radius r0v/3, or 1'73 v0 nearly. Some experiments were made with india-rubber pipes and balloons to see how nearly their behaviour conformed to the theory just given. Fig. 2 (p. 461) shows the apparatus employed. The india-rubber to be experimented on was placed in a Is closed vessel, B, full of water. Two pipes C and D passed through the stopper of B ; of these C communicated with the interior of the expeiimental tube or sphere A, and D immediately with the contents of B. A pressure gauge was connected with C. When -tubes were being experimented on, the ends were closed with hardwood discs, covered with paraffin, through the upper one of which C entered. Fixed into the centre of the lower disc was a long straight wire, E, which passed freely through C, and the position of whose upper end, E', could be read on the scale S. Water could be introduced into A by means of the pipe H con- nected with C. When every part of the apparatus was filled with water, and the pressure gauge showed that the internal and external pressures on the india-rubber were equal, more water was admitted through C. The volume of water thus introduced was measured by the amount expelled through D. The pressure gauge showed the internal pressure in A, and the descent of E' gave the elongation of the tube. The analysis of the results thus obtained is given by the curves in Diagram I. The experiments on spheres were made in the same way, except that the wire E was not used. L891.] Tubes and Balloons distended by Fluid Pressure. 461 The results are given in Diagram II. Diagram III gives the values of the function (K—I)/K^K in terms *:. In Diagram I the abscissa is rfr0. (a) shows the observed pressure iu the tube. (6) „ „ extension of „ ' > represent the values of < . (d) j IP (e) is the theoretical pressure. (/) „ extension. After the unstable state is reached the formula for the extension does apply. For this tube t0/r0 — 0'039. 462 /notability of distended India-rubber Tubes, $c. [Apr. 1891.] Presents. 463 In Diagram II — (a) shows the observed pressure, (&) „ theoretical pressure, an india-rubber balloon for which t0jr0 = 0'0125. (c) is the value of K. The rather uncertain nature of the measurements of both t0 and i/,> these experiments makes the close apparent agreement between observed and theoretical results somewhat illusory ; but it shows at any rate that, if among the values obtained for t0 and v0 those are taken which make theory and observation coincide for one value of •*, the remaining observations will also lie on the theoretical curve. Presents, April 23, 1891. insactions. Baltimore : — Johns Hopkins University. Circulars. Vol. X. No. 86. 4to. Baltimore 1891 ; Studies from the Biological Laboratory. Vol. V. No. 1. 8vo. Baltimore 1891 ; Studies in Historical and Political Science. Ninth Series. Nos. 3-4. 8vo. Baltimore 1891. The University. Belgrade : — Royal Servian Academy. Memoirs. Nos. 2, 5-7. 4to. Beograd 1890 ; Bulletin. Nos. 18, 21-23, 27. 8vo. Beograd 1890 ; Annual. 1888. 8vo. Beograd 1889. [In the Servian language.] The Academy. Birmingham : — Free Libraries Committee. Twenty-ninth Annual Report. 1890. 8vo. Birmingham 1891. The Committee. Cambridge : — Cambridge Philosophical Society. Transactions. V»l. XV. Part 1. 4to. Cambridge 1891; Proceedings. Vol. VII. Part 3. 8vo. Cambridge 1891. The Society. Catania : — Accademia Gioenia di Scienze Naturali. Atti. Serie 4a. Vol.11. 4to. CatanialSQO- Bullettino Mensile. Fasc. 16-17. 8vo. Catania 1891. The Academy. 464 Presents. [Apr. 23, Transactions (continued) . Cracow : — Academic des Sciences. Bulletin International. Fevrier, 1891. 8vo. Cracovie 1891. The Academy. Edinburgh : — Royal Physical Society. Proceedings. Session 1889-90. 8vo. Edinburgh 1891. The Society. Royal Scottish Society of Arts. Transactions. Vol. XII. Part 4. 8vo. Edinburgh' 1891. The Society. Royal Society. Proceedings. Vol. XVII. Pp. 401-432. 8vo. Edinburgh 1891 ; List of Members at November, 1890. 4to. The Society. Frankfort-on-Main : — Senckenbergische Naturforschende Gesell- schaft. Katalog der Vogelsammlung im Museum. Von Hartert. 8vo. Frankfurt a. M. 1891. The Society, Geneva : — Institut National Genevois. Bulletin. Tome XXX. 8 Geneve 1890. The Institn Glasgow : — Glasgow and West of Scotland Technical Co Calendar. 1890-91. 8vo. Glasgow 1890. The Govern Haarlem : — Mnsee Teyler. Archives. Serie 2. Vol. III. Partie 8vo. Haarlem 1890. The Muse Leipsic : — Konigl. Sachsische Gesellschaft der Wissenschal Abhandlungen (Math.-phys. Classe). Band XVII. No. 8vo. Leipzig 1891 ; Berichte iiber die Verhandlungen (Mai phys. Classe). Band XLII. Nos. 3-4. 8vo. Leipzig 1891 Berichte iiber die Verhandlungen (Phil.-hist. Classe). Bai XLII. Nos. 2-3. 8vo. Leipzig 1891. The Society. London: — Entomological Society. Transactions. 1891. Part 1. 8vo. London. The Society. Institute of Brewing. Transactions. Vol. IV. Nos. 3-5. 8vo. London 1891. The Institu Institution of Civil Engineers. Minutes of Proceedings. V CIII. 8vo. London 1891. The Institutio Mineralogical Society. The Mineralogical Magazine. Vol. No. 43. 8vo. London 1891. The Society Royal Institution. Proceedings. Vol. XIII. Part I. No. 8vo. London 1891 ; Additions to the Second Volume of t Catalogue of the Library. 8vo. London ; List of the Members, Officers, and Professors. 8vo. London 1890. The Institution. Royal United Service Institution. Journal. Vol. XXXV. No. 158. 8vo. London 1891. The Institution. Society of Biblical Archaeology. Proceedings. Vol. XIII. Part 5. 8vo. London 1891. The Society. Lund :— Universitet. Ars-skrift. Tom. XXVI. 4to. Lund 1889-90. The University I L891.] Presents. 465 ^ransactions (continued) . Manchester: — Manchester Geological Society. Transactions. Vol. XXI. Part 6. 8vo. Manchester 1891. The Society. Manchester Literary and Philosophical Society. Memoirs and Proceedings. 4th Series. Vol. IV. No. 3. 8vo. Manchester. The Society. Moscow : — Societe Imperiale des Naturalistes. Bulletin. Annee 1890. No. 3. 8vo. Moscou 1891. The Society. New York: — American Geographical Society. Bulletin. Vol. XXII. Supplement. Vol. XXIII. No. 1. 8vo. New York 1890-91. The Society. Paris : — Academic des Sciences. Bulletin du Comite International Permanent pour 1'Execution Photographique de la Carte du Ciel. Fasc. 6. 4to. Paris 1891. The Academy. Ecole des Hautes Etudes. Bibliotheque. Fasc. 83. 8vo. Paris 1890. The School. Societe Mathematique de France. Bulletin. Tome XVEII. Nos. 5-6. 8vo. Paris 1890. The Society. Siena : — R. Accademia dei Fisiocritici. Atti. Serie IV. Vol. II. Fasc. 9-10. Vol. III. Fasc. 1-2. 8vo. Siena 1890-91. The Academy. Sydney: — Linnean Society of New South Wales. Proceedings. Second Series. Vol. V. Part 2-3. 8vo. Sydney 1890. The Society. Xbservations and Reports. Adelaide: — Observatory. Meteorological Observations. 1883, 1888. Folio. Adelaide 1889-90. The Government Astronomer. Public Library, Museum, and Art Gallery. Report of the Board of Governors for 1889-90. Folio. Adelaide 1890. The Governors. Batavia: — Magnetical and Meteorological Observatory. Observa- tions. Vol. XII. Folio. Batavia 1890 ; Rainfall in the East Indian Archipelago. Eleventh Year. 1889. 8vo. Batavia 1890. The Observatory. Bombay: — Government Observatory. Magnetical and Meteoro- logical Observations made in the years 1888 and 1889. 4to. Bombay 1890. The Observatory. Brussels: — Observatoire Royal. Annuaire. 1891. 12mo. Bruxelles 1891. The Observatory. Calcutta : — Meteorological Department of the Government of India. Report on the Administration of the Department. 1889-90. Folio ; Cyclone Memoirs. Part 3. 8vo. Calcutta 1890. The Department. I1' ''• Presents. Observations and Reports (continued). London : — Local Government Board. Report of the Medic Officer for 1889. 8vo. London 1890. The Medical Officer. Marseilles : — Commission de Meteorologie du Departement dt Bouches-du-Rh6ne. Bulletin Annual. Annee 1889. 4to. Marseille 1890. The Commissioi Paris : — Bureau des Longitudes. Annales. Tome 1-3. 4to. Par 1877-83. The Bnreai Observatoire. Annales. M£moires. Tome XIX. 4to. PC 1889. The Observatory. St. Petersburg : — Physikalisches Central-Observatorium. Am 1889. Theil 2. 4to. St. Petersburg 1890. The Observator Tiflis : — Physikalisches Observatorium. Magnetische Beobachtui gen. 1888-89. 8vo. Tiflis 1890; Meteorologische Beobacl tungen. 1889. 8vo. Tiflis 1890. The Observatoi Vienna : — K.K. Central-Anstalt fiir Meteorologie und Erdt netismus. Jahrbiicher. Jahrg. 1888. 4to. Wien 1889. The Central-Anstalt K.K. Gradrnessungs-Bureau. Astronomische Arbeiten. Bs II. 4to. Wien 1890. The Br Virginia : — Leander McCormick Observatory. Publications. Vc I. Parts 1, 4. 8vo. 1883, 1889. The Observatory. Washington: — U.S. Coast and Geodetic Survey. Report of tl Superintendent. 1888. 4to. Washington 1889; Bullet Kos. 18-21. 4to. Washington 1890-91. The Survey. U.S. Geological Survey. Ninth Annual Report. 4to. Washing- ton 1889; Monographs. Vol. I. 4to. Washington 1890; Mineral Resources of the United States. 1888. 8vo. Washington 1890; Bulletin. Nos. 58-61, 63-64, 66. 8vo. Washington 1890. The Survey. U.S. Naval Observatory. Magnetic Observations. 1888-89. 4to. Washington 1890. The Observatory. U.S. Signal Office. Bibliography of Meteorology. Part 3 — Winds. 4to. Washington City 1891 ; Report of Rainfall in Washington Territory, Oregon, California, Idaho, Nevada, Utah, Arizona, Colorado, Wyoming, New Mexico, Indian Territory, and Texas, for from Two to Forty Years. 4to. Washington 1889. Two copies. The Signal Office. Cloud Photography. 4(57 April 30, 1891. Sir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read : — "Cloud Photography conducted under the Meteorological Council at the Kew Observatory." By Lieut.-General R. STRACHEY, R.E., F.R.S., and G-. M. WHIPPLE, Superintendent of the Observatory. Received April 23, 1891. In 1878 the Meteorological Council decided upon undertaking a iries of experiments with the view of attempting by means of photo- graphy to obtain a record of the height and velocity of the clouds, as indicating the movements of the upper parts of the atmosphere. For this purpose a plain cubical camera was constructed, with its optical axis directed to the zenith, and a number of pictures of clouds were thus obtained. The results were so far satisfactory as to establish the possibility of identifying points in the clouds which would admit of the calculation of their height with considerable precision. But, owing to the small field of view of the lens made use of, it was found that the opportunities of photographing clouds in this manner were of somewhat rare occurrence, and it was therefore decided, on the pro- posal of Captain Abney, to whom the Meteorological Council is indebted for his valuable advice throughout the course of these experiments, to construct two cameras so arranged as to enable them to be directed to any part of the sky, and thus to photograph clouds all positions. For this purpose the cameras were fitted with theodolite mountings, provided with altitude and azimuth circles. The dark slides for carrying the sensitised plates were fitted with glass plates, upon hich cross lines indicating the position of the optical axis were ;hed. These lines were photographed simultaneously with the louds, and the readings of the divided circles, recorded at the time of posure, thus supplied the altitude and azimuth of the point of the oud covered by the intersection of the cross lines at that moment. From a photographic picture of a series of staves erected at known ingular intervals, a scale of angular distances was obtained, by means I Lieut-General Strachey and Mr Whipple. [Apr. of \\ hii-li the azimuth and altitude of any point in the cloud pictni could be deduced from those of the intersection of the cross lines. Arrangements were made for erecting these cameras at the ex- tremities of a base of known length (800 yards), between which electrical communication was established. Spring shutters were placed over the lenses, which could be Ml rated and again closed, at the will of the observer, by the passage an electric current, so as to expose the plates for any desired inter of time. Captain Abney also, after numerous trials, devised a suitable for mula for an emulsion for coating the plates, as special precautiot were found to be necessary in order to obtain good cloud photograpl Captain Abney thus describes the photographic process he pi posed : — " My attention has been once more directed to the photographic process to employ for the delineation of the clouds, certain inconvenience having attached to the use of collodion-emulsic which at first I had not foreseen. I had then recourse to gelat plates, but the manner in which they are ordinarily prepared indue a sensitiveness which becomes unmanageable, even when a diaphrag with a small aperture is used in the lenses. The great desideratt in the plates appears to be that a small variation in the intensity the light proceeding from the sky or cloud shall produce a contrast in the intensity of the developed image. A very rapid plat does not answer for this purpose ; hence I tried several modific tions. The process which at present has given the best results is follows : — " 150 grains of bromide of ammonium and 10 grains of iodide of potassium are dissolved in 3 oz. of water, to which 80 grains of Nelson's No. 1 photographic gelatine and 80 grains of Coignet's gelatine have been added. This is dissolved by the aid of heat, and 200 grains of silver nitrate dissolved in 1^ oz. of water are added. The whole is warmed to 100° F. for five minutes, and allowed to set after being poured out in a flat dish. The emulsion thus produced is washed (in the usual manner) from the soluble salts, and is the re-melted and plates coated and dried, as is customary in the gelat process. " This formula gives very constant results, and great contrasts image arc obtained by careful development." The years 1881 to 1884 were passed in working out the det of the arrangements above described, and in 1885, after numeror ])reliminary trials, it was resolved to erect the two cameras at the Kew Observatory. One was placed on the roof of the Observator building, and the other on a stand in the Old Deer Park, 800 ya from the other, on the road leading to the Observatory from Rich- mond ; and a telegraph cable carrying two insulated copper wires of 1891. Cloud Photography. 469 low resistance, buried a few inches below the surface of the ground, was laid between the two stands. Switches, attached to telephones as well as to an electric battery, were fixed to these stands, and wires were arranged on the cameras, so that the observers could either communicate with one another, or work the exposing shutters of the two cameras at will. Operations for the determination of cloud height and motion were then carried out on suitable occasions, as follows : — The two observers, termed for convenience A and B, proceeded to their respective stations, each provided with a box containing half-a-dozen dark slides charged with sensitised plates, and also an adjusted watch. The cameras were set up on the pedestals, levelled, and the connecting wires joined up. Locking plates of peculiar construction were pro- vided, which ensured that the zero points in azimuth of both cameras were exactly directed to the same point of the horizon. The observer at A, when he saw B had reached his station and placed his camera on the pedestal ready for use, attracted B's atten- tion by means of a flag waved overhead, and directed him through the telephone to set the instantaneous shutter of his camera, setting that of his own camera at A at the same time. A then, making use of the push, sent a current of electricity through the two cameras, I ('Which should liberate both shutters at the same instant of time. An I • enquiry was immediately made through the telephone of B, and, if the reply assured A that the shutters were working satisfactorily, the I observers proceeded to the second stage of the observation, which was as follows : — A carefully examined the sky and, selecting a suitable cloud, directed the sights on his camera towards it, making a convenient setting of the horizontal and vertical circles, which he then read off. O l He then told B to set his camera to the same azimuth and altitude, and insert a loaded plate-holder in its groove, repeating the circle readings to ensure accuracy, and also at the same time to set his shutter. A, whilst directing B through the telephone, conducted the same series of operations at his own instrument, so that, as soon as B telephoned that he was ready for action, A switched the battery on to the line, and, watching the cloud for a favourable instant, touched the push, whereby the two plates were exposed simultaneously, the instant of the exposure being recorded by both observers in their respec- tive note-books. They then quickly exchanged their plate-holders for Dthers containing fresh plates, and again set the shutters, so that by the Dime sixty or seventy seconds had elapsed since the first exposure was made they were ready for a second, which was carried out as before inder the directions of A, both observers again noting the time. Aiter this. A, having switched on the telephones, enquired of B if he K obtained the two pictures. If the reply was in the affirmative, )L. XLIX. 2 I 470 Lient.-O( 11- r.il Strachcy and Mr. Wliij.ple. [Apr. he was directed to read both his circles, and to enter the readings, with the times of the two exposures and the numbers of the plate- holders in his book, A doing the same for his own instrument. Having deposited the plate-holders in the light-tight carrying boi another charged pair were taken, and a fresh cloud in another part the sky selected, and the operations already detailed were repeat until the stock of charged holders was exhausted. The observers ' then, by means of the telephones, again comi their watches, and noting their differences, if any, sighted tl cameras on each other, and read their mutual bearings and altituc This was done in order to be sure no displacement had taken place either the orientation or level of the instruments. They tl unlocked the stands, dismounted the cameras, and put them away the lockers of the pedestals, ready for use on another occasion, veying the plates to the photographic laboratory for development subsequent treatment. From time to time, the empty plate-holders were taken out, lenses directed to each other, and settings made and circles with the view of determining the true bearings of the fiducial before described, from which the angular position of the cloud-j dealt with were obtained. On removal of the exposed plates from the holders, the dates the observation having been written on each of the films in pencil, well as a register number, development proceeded. This was ducted in a wooden tray with a glass bottom specially adapted hold four plates. The two A's and two B's forming one set pictures were usually selected for simultaneous development, in or that the negatives obtained might possess the same degree of tensity. Before hydrokinone became an article of commerce, solution of pyrogallic acid or sulphate of iron was employed as developing agent, but, since 1889, Edwards's hydrokinone develc has been employed by preference, as being less liable to prodi fogged plates. Owing to the efforts of the Kew observers being chiefly directed photographing high cirrus clouds, very careful and slow developmc was required, to produce satisfactory negatives, and it has generally necessary to continue the operation for about forty minnt to bring out a successful result. In some cases of very thin fil cirrus, the so-called mare's tail clouds, the development occuj l£ hours, before the picture appeared. For discussion of the photographs, in most cases prints were of the negatives by the ordinary albuminised paper process. Various methods of obtaining the heights and velocity of motion the clouds from the photographs thus made have been attempt The computation by the ordinary trigonometrical formulae from „ 91.J Cloud Photography. 471 azimuths and altitudes derived by measurement of a series of points in the clouds, properly identified in the sets of pictures, is very tedious, and a graphical method was suggested by Sir Gr. Stokes, which, though very ingenious, was found to be troublesome in prac- tice, and was not persevered in. From the nature of the process employed, the indefinite outlines of the clouds, and their incessant change of form, complicated by the effects of perspective distortion on an irregular and ill-defined surface, it is necessarily impossible to identify cloud-points in the different pictures with much precision or make exact measurements ; and approximate results, therefore, are all that can be sought for. The object of the enquiry is chiefly to determine the velocity of movement of clouds at varying heights above the earth's surface and to obtain the heights of those observed at the greatest elevations, which appear as cirrus. If A and JB are the azimuths of any point in a cloud, and 7ta and Z4 the zenith distances, observed respectively at A and B, the ends of the base /3, then the distances, measured in a horizontal plane pass- ing through the base, Dtt, D6 from A and B respectively of the point vertically under the cloud-point will be ^_ ft'- 'sin(A-B)' ^sin(A-B)' and H, the height of the cloud-point above the horizontal plane passing through l.he base, will be H _ * sin (B) sin (A) Psin (A— B) tan Za Psin (A— B) tanZj' hese values are readily found by means of a slide-rule constructed as shown below. The graduations of the upper scale of the fixed rule are log sines ; those of the lower scale of the fixed rule logs of Qumbers, the log of 2400 feet, the length of the base, coinciding with log sin 90°. The upper sliding rule No. I is graduated with log sines of small ingles on the same scale as the first rule, the point marked with index No. I indicating log sine 5° 44' 27", which is 9' 00000, or 23", which is S'OOOOO. e lower sliding rule No. II is graduated with log tangents Z, the joint marked with index No. II, corresponding to log tan 45°, and on '•he same scale as the sines. To apply the rule, bring index No. I of the slide-rule No. I opposite ihe angle A on the upper fixed scale. Then bring the index No. II of ;he slide-rule No. II opposite to the angle A — B on the slide-rule ^o. I. 2 i 2 472 Lieut. General Strachey and Mr. Whipple. [Apr. Fio. 1. Opposite the index No. II, or tan 45°, will be found on the lower fixed scale the distance Dj, in feet ; and opposite to the angle Z* will be found on the same scale the height of the cloud in feet. By a 1891.] Cloud Photography. 473 similar process •will be found tbe distance Da and a height of the cloud determined from Za. The position of the point vertically under the selected cloud-point will be determined with sufficient accuracy graphically, by the inter- section of the two distances measured from the ends of a line drawn to represent the base. The repetition of this process for the second set of photographs will in like manner give the position of the cloud-point after the interval elapsed between the taking of the two sets of pictures, and the dis- tance travelled being measured on the diagram, the velocity can be found, and the direction of motion will be shown in relation to the direction of the base. Irrespective of the laborious nature of this process, it was found that the angles on which it was based were often so small that the results obtained were inconsistent and unreliable. In 1890, therefore, it was decided to try another method of observing, which would admit of much simpler treatment. This was to fix the cameras so that the optical axes were directed to the zenith, ind to photograph clouds which passed across the field of view which is comprised within a circle described at an angular distance of about 15° round the zeniths of the two stations. The defect of this method 18 that it very materially limited the scope of operations, and reduced }he opportunities of taking pictures to a comparatively small number, :or it was found that a large proportion of the clouds which seemed ipparently favourable for photographing when viewed by reflected i jolar light incident upon them at oblique angles became almost nvisible when observed directly overhead. This was notably the ;ase with cirrus, some forms of which, especially those possessing the lature of cirro-stratus, appear as practically structureless masses vhen seen in this position. But notwithstanding these drawbacks, tome of which, it is hoped, may be obviated, the advantages of this nethod of observing seem to be sufficient to lead to its adoption in reference to any other yet suggested. To adapt the cameras for work in this manner, both altitude and .zimuth circles were permanently clamped, rendering them immovable n both vertical and horizontal pla.nes, and the locking plates were hifted on the pedestals, so that, while the fiducial lines on the tictures intersect at the zenith, the direction of one of them is that f the line joining the two stations, or the base, the other being at ight angles to it. With the object of ensuring the proper adjustment of the optical xes of the cameras, a tripod stand 12 feet in height was made, which ras temporarily erected immediately over them. A plummet was uspended directly above the lens-centre, from the point of intersec- ion of two horizontal wires fixed at right angles to one another, one 474 Lieut.-General Strachey and Mr. Whipple. [Apr. of them being carefully made to coincide in direction with the joining the two cameras. The charged dark slides, which are separately numbered, so that correction for each of them may be ascertained and recorded, are tl successively placed in the camera and photographs taken of the wires overhead, the pictures of which should coincide with the fiducial lines of the camera, the position of which is as nearly as possible adjusted to secure this coincidence. The photographs thus made preserved, to supply data for correcting the negatives for any error < the fiducial lines, should the slides not be properly adjusted so as secure the coincidence before spoken of. Assuming, as may be done without objection for this purpose, the cloud surface photographed and the earth's surface at the pi of observation are in parallel planes, distances measured on the pi graphs from the intersection of the fiducial lines will tangents of angles measured from the zenith to radius equal to height of the cloud. Again, if a pair of photographs made simultaneously at extremities of the base are superimposed one on the other, so that forms of the clouds coincide, which they will do accurately if pictures are properly placed, then the line joining the intersections ' the cross lines will represent, both in magnitude and direction, line joining the zeniths of the two ends of the base, from which observations are made, or the base itself. If the adjustments before described have been satisfactorily the base, as thus indicated, should obviously fall on one pair of fiducial lines, which, when the photographs are superimposed, she also coincide ; otherwise, if the fiducial lines in the two pictures made to coincide, then the separation of points properly identified the pictures will be the measure of the parallax or angle subt by the base at such points. . A scale of angular distance having been prepared as before plained, the parallax thus measured may at once be converted angular measure, and the height of the cloud is given by equation H = /3/tan r, where v is the angular parallax. In like manner, if two photographs taken from the same point u ith an interval of time between them be superimposed, so that the cloud pictures coincide, the line joining the intersections of the cross lines will represent in magnitude and direction the movement or drift of the cloud, and the velocity in miles per hour will be found from the equation — SB 3600 V = -x-*— X— :r-, p 5280 t" 1891.] Cloud Photography. 475 where 6 and p are the drift and parallax as measured on the photo- graphs, and t the interval in seconds between the pictures being taken. The method of reduction of the photographs first adopted and em- ployed during the early part of the past summer was as follows : — Prints were made on albuminised paper of the set of four pictures, two taken at each end of the base with an interval of time between them, and they were mounted on stout cards in order to avoid the usual curling up of the paper. When necessary, new fiducial lines were then drawn in the proper direction through the points that had been ascertained to represent the corrected position of the lines of reference as before described, and these lines were extended to the margins of the cards. If possible, five or six cloud-points were then selected in each print, capable of satisfactory identification. A sheet of paper was next procured, larger than the pictures, and lines intersecting at right angles were drawn across it. Punctures were then made, by means of a needle, through all the selected cloud-points in the four pictures, which were successively placed over the reference sheet (termed here- after the receiver), so that the fiducial lines upon the pictures coin- cided with the lines drawn upon the receiver, thereby ensuring the points of intersection being directly superimposed, and, by means of a needle passed through the pricked holes, the marked cloud-points were transferred to the receiver. This having been done in turn for all the four pictures of the set, the points thus pricked off were joined by inked lines, those obtained from the pair of pictures taken simultaneously being drawn in black ink, and those from the other pair in red, by which a series of parallelograms was formed, equal in number to the number of points selected for treatment. The black lines or sides of these parallelograms then represented the parallax of the several cloud-points, being proportional in length to the tangent of the angle subtended by the base line at the altitude of the cloud, whilst the red lines forming the other two sides of the quadrilaterals represented on the same scale the drift of the cloud daring the interval which elapsed between the taking of the two sets pictures. The measurement of these black and red lines provided the means already explained of determining the height of the clouds and the rate of their motion, the direction being given by the inclination of the o lines, of which the black one represented the base. In dealing with the direction of the drift when thus obtained from positive prints, it has to be remembered that by the printing the right and left of the pictures are transposed, so that the east is on the ! left and the west on the right in a picture the top of which is directed to the north. of t I7i! Lieut.-GentT.ii Str.-iehey and Mr. \Vliij)j)l.-. [A\> The necessary measurements were made on a scale of millimeters, and the computations carried out by the help of logarithms. The operations thus described have lately been much abbreviated in various ways. First, it has been found possible to carry out the superposition of the pictures by means of the negatives only, and to work without either employing 'positives or depending on the identi- fication of a few selected points whose positions were transfern «l a receiver. A frame has been constructed which carries the glass negative plates upon sliders in grooves running in parallel planes, one imme diately over the other, but arranged so as to travel at right angles one another, the lower moving towards and away from the observe whilst the upper traverses from right to left. A mirror, either silvered or an opal plate, is employed to reflect the light of the si upwards to the eye through the negative photograph when tl apparatus is placed upon a table in front of a well-lighted window. Stray or diffused light is excluded by placing a box, darkened on it inner surface, over the negatives, and the observer views the com- bination through a tube fixed perpendicularly upon the top of the box. The two photographs to be compared are placed one in each of tl sliding frames, which are first so adjusted that the fiducial lines whic follow the direction of the base pass exactly over one another. Nei the bottom or backwards-and-forwards slider is moved until the clouc pictures, say a pair marked A and B, are seen to coincide, and tl distance between the intersections of the cross lines on the two plat representing the zenith points, which is the parallax, is then measui by means of a pair of compasses ; but a scale could readily be fix* on the slides from which the parallax could be read off withov measurement. In order to avoid calculations, a standard curve has been drawi (see fig. 2), from which the height of the cloud may at once graphically determined from the distance between the intersections the cross lines or parallax of the base as thus measured. On the axis of abscissa? of this curve are marked off the heights a scale which makes 2400 feet, the length of the base, equal to tt focal distance of the camera, and at regular intervals along t-hi< lii ordinates are drawn of the length, as measured on the photograph!: of the parallax corresponding to the several heights. Through t\ extremities of these ordinates a curved line is drawn, which gives tl locus of the equation h = p cot IT, the lengths It and p being both expressed on the scale just tioned. The same operations are next performed with pictures Aj and 1891.] Cloud Photography. 477 id a second value of the cloud height is obtained, which serves to mfirm or modify the first determination. Then pictures A! and A2 are placed in the frame, and the images Derimposed and made to coincide as before, but now the distance sparating the zenith of the two pictures, which will be termed the ift, will indicate the space the cloud has moved during the interval - jetween the taking of the two pictures ; and the angle which the line joining the zeniths makes with the line of base gives the direction in lich the drift has taken place. From the length of the drift measured upon the plates as above, the jlocity of motion may easily be obtained by a graphical method. 478 Lieut-General Strarhey and Mr. Whipple. A.B before stated, the velocity in miles per hour is v _ £ ft 3600 ~ p ' 6280 ' ~7'~ To obtain the value of V graphically, proceed as follows : — Draw a horizontal line on which will be represented equal time- intervals from 0 to 120 seconds, see fig. 3. Erect vertical lines at all the points between 60 and 120 seconds, which will include all the time intervals between the pictures likely to occur in practice. On the first of these verticals mark off any convenient length to represent 1891.] Cloud Photography. 47D 1 mile, and divide it into 60 equal parts, and from the zero point on the horizontal line draw radiating lines through the points of division, extending to the vertical at 120 seconds. This constitutes a scale of proportional velocities from 0 to 60 miles per hour, and may be ex- tended to any higher velocity. N"ext (see fig. 4) draw two parallel vertical lines at a distance apart equal to the length of the base, 2400 feet, on the scale before assumed to represent 1 mile, and draw a horizontal line intersecting the other two at right angles at points M and N. Then mark off the length of drift t upwards on each of the two 480 Cloud [Apr. 30, vertical lines from M and N at points P and Q ; and the length of the parallax p, on the horizontal line from M towards N, at a point R. Join P, B, intersecting the vertical through N at S. Then QS represents the drift on the scale assumed to represent 1 mile. Let this be marked off upwards on the vertical line drawn on the scale of proportional velocities, fig. 3, from the seconds division correspond- ing to the time interval between the pictures, and the velocity of drift will be indicated by the radiating line nearest to the mark thus made. The scales above described for the graphical determination of the cloud heights and velocities are engraved and printed on sheets of paper, which, after the computations are completed by their aid, will serve as convenient records of the observations. After a little practice, the whole of the processes requisite for these determinations from the glass plate -negatives of a complete set of four pictures will not exceed 20 minutes. Quite sufficient accuracy is ensured, and the labour and risk of error arising from the use of tables is entirely avoided. Although the cameras now in use only embrace a circle of angular diameter of about 30°, trials have been made with a lens which gives satisfactory pictures of double that extent, which is probably as much as could be desired. The following is a list of the determinations made during the past year by the methods now described : — Date. Height. Velocity. Direction. Surface. Velocity. Direction. 1890. July 10 miles. 1-29 5-20 f 5-47 < 8-39 [6-34 2-87 1-64 1-97 1-93 6-87 6-29 7-22 2-60 f 2-66 { 2-87 [ 2-27 4-60 4-60 1-72 1-71 miles. 7-27 45-80 41-39 64-61 49-16 15 -19 20-19 13-70 13-28 42-40 45-18 42-00 25-90 19-90 19-70 22-00 54-40 53-10 5-30 6-40 N.W. S.W. S.W. S.W. S.W. S.S.E. S.S.E. W.S.W. W.S.W. w. w. N. S.S.W. S.S.W. S.S.W. S.S.W. s.w. s.w. s.w. s.w. miles. 10 5 5 5 5 15 15 7 7 3 3 8 10 10 10 10 16 16 5 5 N.W. S.W. S.W. S.W. S.W. s.w. s.w. N. N. W.S.W. w.s.w. W.N.W. S.E. S.E. S.E. S.E. S. S. S. S. 16.. 16 August 26 26.. , 29 29 September 9 9 10. . , 17 . 17 18 . , „ 18 „ 23 , 23 1891.] The Passive State of Iron and Steel. 481 II. " The Passive State of Iron and Steel. Part III." By THOS. ANDREWS, F.R.SS.L. and E., M.Inst.C.E. Received April 23, 1891. SERIES V, SET 1. Relative Passivity of Wrought-iron and various Steel Bars, and the Influence of Chemical Composition and Physical Structure on their Passive State in Cold Nitric Acid. . The author is not aware that any previous experiments have hitherto been made showing the relative passivity of the various kinds of steel compared with wroughb iron, or the influence of the chemical composition and physical structure of such metals on their passive condition in nitric acid. The passive state of iron or steel may have hitherto been regarded by many as a sort of fixed property pertaining to iron and steel alike, when immersed in cold, strong nitric acid. The following experi- ments were made to investigate if the passivity was of an universally static character, or whether it varied with the chemical composition and general physical structure of the metal and, if so, to what extent. For convenience, this part of the investigation was divided into two parts, one portion of the observations, Set 1, being made on drawn rods of metals of known chemical composition and structure, and the other, Set 2, of experiments constituting a study of the relative FIG. 5. WROUGHT IRON BAR A Mr. T. Andr [Apr. 30, passivity of various steel and iron plates of known bnt varied com- position, AC. The experiments of Set 1 were made on bars of the various steels selected from the author's standard samples. The Table VI. Current between polished " passive " wrought-iron and steel ban in cold nitric acid 1*42 sp. gr. Electro-chemical position of the wrought iron positive, except where otherwise marked N (nega- tive). E.M.F. in volt. Time from com- Column 1. Column 2. Column 3. Column 4. mence- ment of experi- ment. Soft cast steel with Hard cast steel with Soft Bessemer steel Tungsten steel with wrought iron. wrought with wrought iron. wrought iron. iron. Set No. 1. Set No. 2. Set No. 3. Set No. 4. Set No. 5. Set No. 6. seconds 0 o-ooo 30 0-013 0 -022 N 0-004N 0-017 0-016 0-070N minutes 1 0-005 0-022N 0 -016 N 0-022 0-017 0-074 N 3 0-005 N* 0 -022 N 0-020N 0-030 0-024 0-073N 5 0-007 X 0-028N 0-0-23 X 0-034 0-032 0-071N 10 0-011 N 0-026 X 0-022N 0-034 0-034 0-070N 20 0-012 X 0-025N 0-020 N 0-031 0-034 0-065N 30 0-013 X 0 -023 N 0-023 N 0-028 0-032 0 -061 N 40 0-013 JT 0-01't X 0-020N 0-024 0-029 0-060 N 50 0 -013 N 0 -017 N 0 -019 N 0-023 0-026 0-059N hours 1 0 -013 N 0-014N 0-019 N 0-020 0-024 0-056N li 0 -012 N 0-011 N 0-020 N 0-017 0-019 0 -055 N 2 0 -Oil N 0-008 N 0-020N 0-014 0-016 0 -054 N 2i 0-007N 0 -005 N 0-019N 0-012 0-013 0 -052 N 3 1 0 -004 N i 0 -001 N 0-018N 0-012 0-013 0 -052 N 3i 0-002N o-ooo 0 -018 N 0-011 0-013 0-051 N 3k 0-000 o-ooi 0-017 N 0-011 0*013 0-050N 4 0'002 0-004 0-016N 0-011 0-012 0-049N 5 0-006 0-007 0-013N 0-011 0-011 0-049N 7 0-016 0-012 0-006N 0-011 0-011 0-048 N 12 0-037 0-018 0-006 0-012 0-011 0-048 N 18 0-052 0-026 0-017 0-013 0-012 0-047N 20 0-058 0-030 0-023 0-013 0-013 0-047N 22 0-064 0-033 0-028 0-014 0-015 0-048N 24 I 0-070 0-036 0-033 0 016 0-065N 26 0-078 0-035 29 0-085 0-042 30 "-088 0-047 38 0-098 0-058 40 0-107 0-060 43 0-065 45 0-071 47 0-090 1891.] The Passive State of Iron and Steel. bars were cold drawn through a wortle, and were therefore different in physical structure to the rolled plates used in the second series of the experiments. An idea of their general properties will be obtained on reference to Part II, Tables IV and V. A polished bar, 8£ inches long, 0'310 inch diameter, of the steel to be tested was placed in the wooden stand W (fig. 5), along with a polished wrought-iron bar of equal size, and the pair were then immersed in 1| fluid ounce of nitric acid 1'42 sp. gr., contained in the JJ-tube, the bars being in circuit with the galvanometer. The immersion was continued for the periods stated, and with the electro-chemical results given on Table VI. The wrought-iron bars used in each experiment were cut from one longer polished rod, so as to afford a fair comparison of the relative passivity of the various steels, compared with the wrought iron and also with each other. The results are the average of numerous experiments in each case. SERIES V, SET 2. Relative Passivity of Wrought-iron and various Steel Plates in Cold Nitric Acid sp. gr. 1*42. In the following series of observations, the metals experimented upon consisted of plates of rolled wrought iron, rolled steels made by the Bessemer, Siemens-Martin, or crucible cast-steel processes, and they were of the chemical composition given on Table VII. Each plate was 3 inches square, by g inch thick, = total area of exposure, 19' 5 square inches including edges, brightly polished all over, and had a long thin strip left on the top side (see fig. 6), for convenience Fia. 6. of attaching to the galvanometer connexions. The whole of the wrought-iron plates, used as elements with the various steel plates, 484 Mr. T. Andrews. [Apr .2 a H be a •§ i -a O •** o _ - a 5 | § § § § 1 H £8 j 8 8 8 8 8 gf ^o 90 CO C- a *" r*4 — i ~ • n - £ '_ — 0 O) ^H O) 1^ S.8 § O) § 8 00 OJ o T) 1 i 7 o 2 n 1-5 ^ O) & -H — eo >o |H (O s4 1 1° 0 O 0 i-H o 1—4 i a,° 0 fc js is M 0 S % o r-l A O O 0 o O 0 0 pt £ it ^ U3 1— 1 eo •///*. [Apr. 30, Transactions (continued). Boston : — American Academy of Arts and Sciences. Proceedings. Vol. XVII. 8vo. Boston 1890. The Academy. Cambridge, Mass. : — Harvard University. Bulletin. No. 48. 8vc [Cambridge] 1891. The Universit Kew : — Royal Gardens. Bulletin of Miscellaneous Information. No. 52. 8vo. London 1891. The Director. London : — Photographic Society of Great Britain. Journal and Transactions. Vol. XV. No. 6. 8vo. London 1891 ; List of Members. 1891. 8vo. London. The Society. Royal Agricultural Society of England. Journal. Ser. 3. Vol. II. Part I. 8vo. London 1891. The Society. Royal Statistical Society. Journal. Vol. LIV. Part 1. 8vo. London 1891. The Society. Montpellier : — VI" Centenaire de 1'Universite. Compte-Rendu, Discours, Adresses. 4to. Montpellier. 1891. The University. Munich : — K.B. Akademie der Wissenschaften. Sitzungsberichte. (Philos -Philol. Histor. Classe) 1890. Bd. II. Heft 3. 8vo. Miinchen 1891. The Academy. Naples : — Accademia delle Scienze Fisiche e Matematiche. Rendi- conto. Ser. 2. Vol. IV. Fasc. 1-12. 4to. Napoli 1890. The Academy. Paris: — Ecole Normale Superieure. Annales. Annee 1891. No. I. 4to. Paris. The School. Rio de Janeiro : — Museo Nacional. Archives. Vol. VII. 4to. Bio de Janeiro 1887. The Museum. Bourne (W.) Handy Assurance Manual. Second edition. 1891. 8vo. London; Handy Assurance Directory. 1890. 8vo. London. The Author. Brodie (Rev. P. B.) On Fossil and Recent Extinct Birds. 8vo. Warwick [1891] ; Address to Warwickshire Naturalists' and Archaeologists' Field Club. 1890. Warwick. The Author. Buchan (A.) The Meteorological Results of the " Challenger " Ex- pedition in relation to Physical Geography. 8vo. London 1891. The Author. Cassal (C. E.) Annual Report of the Public Analyst appointed for the Parish of Kensington, for the year ended 31st March, 1890. 8vo. [London.] The Author. Jones (T. Wharton) F.R.S. Report on the State of the Blood and the Blood- Vessels in Inflammation. [Five copies.] 8vo. London. 1891. The Author. Kops (J.) Flora Batava. Aflev. 291-292. 4to. Leiden [1891]. The Netherlands Legation. 1891.] Presents. 491 Examination for Colour of Cases of Tobacco Scotoma. 491 Netto (L.) Le Museum National de Rio de Janeiro et son Influence sur les Sciences Naturelles en Bresil. 8vo, Paris 1889. The Author. Phillimore (W. P. W.) The Dictionary of Medical Specialists. 8vo. London 1880. The Editor. Pickard-Cambridge (Rev. O.), F.R.S. The Spiders of Dorset. 8vo. Sherborne 1879-1881. With four Supplementary Papers. 8vo. Sherborne 1882-1889 ; Monograph of the British Phalangidea or Harvest-Men. 8vo. Dorchester 1890. The Author. Roberts-Austen (W. C.), F.R.S. An Introduction to the Study of Metallurgy. 8vo. London 1891. The Author. May 14, 1891. Sir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. The Presents received were laid on the table, and thanks ordered for them. In pursuance of the Statutes the names of the Candidates recom- mended for election into the Society were read from the Chair as follows : — Anderson, William. Bower, Prof. Frederick Orpen, D.Sc. Conroy, Sir John, Bart., M.A. Cunningham, Prof. Daniel John, M.D. Dawson, George Mercer, D.Sc. Elliott, Edwin Bailey, M.A. Frankland, Prof. Percy Faraday, B.Sc. Gilchrist, Percy C. Halliburton, William Dobinson, M.D. Heaviside, Oliver. Marr, John Edward, M.A. Mond, Ludwig. Shaw, William Napier, M.A. Thompson, Professor Silvanus Phillips, D.Sc. Tizard, Capt. Thomas Henry, R.N. The following Papers were read : — " On the Examination for Colour of Cases of Tobacco Scotoma, and of Abnormal Colour Blindness." By Captain W. de W. ABNEY, C.B., R.E., D.C.L., F.R.S. Received April 29, 1891. The following cases were submitted to the Colour Vision Com- littee, and it was thought desirable that the results of the examina- tion should be communicated to the Royal Society. VOL. XLIX. 2 L 492 Capt. W. de W. Abney. Examination for [May 14. The examination of these three cases was conducted at different times, the first partially in the presence of the Colour Vision Com- mittee by Mr. Nettleship, and the two last, and part of the examination of the first, at different times, in my laboratory, with the assistance of Mr. Nettleship. In all three cases the examination made was an ability to distin- guish colour, luminosity of the different parts of the spectrum, and total sensation of light ; and, in addition, in the first case, to range of colonr sensation on the retina. Case I. — This patient, Alfred C., aged 36, a traveller, was suffer- ing from rather severe tobacco amblyopia, and was brought to the Committee by Mr. Nettleship. The scotoma was a very marked one, and the loss of colonr sensation most complete. Mr. Nettleship has kindly added the following remarks on the case : — His acuteness of vision was /„ with R. and -/5 with L. He smoked half-an-onnce of "shag" daily and drank about four pints of beer. His sight had been failing for about two months. As is common in early stages of this disease, the ophthalmoscope revealed no decided changes at the optic discs. He was tested at the Royal Institution by Mr. Nettleship, in the presence of the Committee, with the following results : — He passed the test of the Holmgren wools satisfactorily, proving that the usual vision was normal for colour. I had prepared small pellets of moulder's clay, each weighing 4 grains, and about \ inch in diameter, and had had sets coloured with the same colours as those of the Holmgren wools. C. was told to pick out the blues, reds, and greens. The blue pellets he picked out without fail, and he never made the least mistake in his choice, but he failed entirely to distin- guish the greens or reds, mistaking them for drabs and greys, which were amongst the pellets. When told to look away some 20° from the slab on which the pellets were placed, he at once saw all the colours, but directly he turned his eyes to pick them out, all colour perception, except for blue, disappeared. This test indicated that he had lost all perception of green and red in the central part of the eye. He was next tested with small discs of different colours by Mr. Nettleship, keeping his eye fixed on a given point, and the loss of colour sensation for all except blue, and perhaps a little yellow, in the central part of the eye, was at once made apparent ; the blue he would distinguish with the greatest facility, and the sensation was appa- rently as strong as in normal eyesight. A further test was made by Mr. Nettleship with coloured lights to imitate signal lights, and he named a brilliant red light, and an equally brilliant green light, when side by side, both as white (see also p. 85). This man attended at my laboratory, at the meeting of the Com- mittee on Colour Vision, with Mr. Nettleship, and he was tested with 1891.J Colour of Cases of Tobacco Scotoma, 493 the colour-patch apparatus described in " Colour Photometry," in the Philosophical Transactions,' 1886, by General Festing and myself. The objects first in view were to test his perception of the spectrum colours, and then his retinal field colour perception for the same. A template was cut out after the manner described by General Festing and myself in the second part of " Colour Photometry " (' Phil. Trans.,' 1889), of such a shape that all the spectrum lying between X 4600 and X 6600 was reduced to equal luminosity when it was ro- tated in front of the spectrum. Diaphragms containing holes of different sizes were placed in front of the last prism, and thus a round spot of monochromatic light of the same luminosity was produced upon the screen when a slit was passed through the spectrum. From the red end to X 5270 he called the whole of the colours white, and from that point he began to see blue, called the colours bluish and blue. When the full illumination for all the colours was used, the same results were obtained. From this examination it would appear that he was totally deprived of the sensation of any colour except of blue. A subsequent examination of his perception of the luminosity of different rays, however, has to be taken into account, for in the first examination he had no light of pure white with which to compare the colours. In the next experiments, a strip of white light was I. II. III. IV. V. Remarks . Scale No. Wave- length. Luminosity to the normal eye. Luminosity toX. IV. III. 60 6730 7-3 0 0 Sees only the white stripe. 57 55 6423 6242 32 65 10 38 0-31 0-65 Calls red yellowish, and white bluish. » » » 53 6074 96 86 0-89 Both one colour. 51 5920 99 90 0-91 „ ,. 47 43 5660 5430 92 69 83 625 0-90 0-90 Calls green a little blue ; white he sees as white. » >i > 40 5270 50 46 0-92 » >» » 32 31 4910 4960 8-5 7 9 8 1-06 1-14 Sees blue as blue, and white yellowish. » » » 26 4680 3 3 1-00 » » » 2 L 2 -I'M Capi. W. de W. Abney. Examination for [May 14, placed in juxtaposition to the colour, and the results were slightly different. The table (p. 493) gives his luminosity measures. Col. I is the empyric scale nnmber, II is the wave-length.nl the luminosity of the colour to the normal eye, IV the luminosity to C, and V the ratios of III to IV . In the diagram, his luminosity curve X is shown, its area being 1400 against 1650 for the normal eye. As will be shown, his per- ception of light is only two-thirds of that of the normal eye ; hence 1891.] Colour of Cases of Tobacco Scotoma, 495 his area of luminosity should be 1100. As it is 1400, the ordinates of the above carve should be multiplied by 0'8, to compare with that of the normal eye. It should be mentioned that his matches of luminosity were ma.de without any hesitation, and were concordant for each observation, which is not to be wondered at, as the matches, except at the blue end, were practically matching shades of black to white. From the foregoing, it will be seen that the white which C. sees as white is the same as the D sodium light, and that the red he says is yellowish. The mixture of this yellowish-white with the blue apparent makes white at X 5430. He sees a little blue in the spectrum colour at A, 5720, so it must be taken that at that point of the spectrum he begins to see colour, a point which is considerably lower than that given by his preliminary examination of the spectrum colour, and due, no doubt, to the fact that the white light used by the comparison light was that of the positive pole of the electric light. It seems probable that what C. called yellowish was really a sensation of white mixed with a very small quantity of red sensation (as he saw no yellow in the orange, in which that colour would be most easily distinguished on account of its luminosity), and red light, when strongly diluted with white light, to the normal eye appears slightly orange. Subsequently C. was tested for the illuminating value of white light compared with my own and that of Mr. Nettleship. The appa- ratus used in this case (fig. 2) was, I believe, somewhat on the prin- ciple of Dr. Forster's photometer, with which I was unacquainted before I made the instrument. It is made as follows : — FIG. 2. 496 Capt. W. de W. Abney. Examination for [May 14. E is a small tube for the eye to look down into a box 4 feet lonj G is an aperture in the side of the box covered with ground glass ; L is a gas-light ; A rotating sectors which can be opened and closed at will ; M a mirror to reflect the light on to a card (which can be changed at will, and on which are one or more black spots) slipping into a slot S from the top of the box. E is so arranged that the whole of the card can be viewed. The observer places his eye at E, and the sectors, whicb at first are closed, are gradually opened until the observer can see that there are black spots on a white ground. The angle of the aperture of the sector is noted. Each eye is tested. In this case my own right eye, agreeing with that of Mr. Nettle- ship, was used as the standard, since it was with that that the normal luminosity curve was originally made. Right eye. Left eye. Remarks. Abney 17 17 5 smallish spots used as test object. AlfredC... 31 25 >» » » » Abney ..... 10 9 1 large spot „ „ AlfredC... 26 17 n » i> »» From this it may be concluded that C.'s appreciation of light to the standard is about half for the right eye, and two-thirds for the left that of the standard. The horizontal colour field was tested by a modification of the colour patch apparatus. FIG. 3. A brass-work frame was made as shown, fig. 3. A and B are fixed to a board, the other arms are capable of moving with parallel motion, the arm BD slides through D ; at B, and attached to BD, is a mirror which can be fixed in any position. The light, when once turned in 1891.] Colour of Gates of lobacco Scotoma, fyc. 497 the direction BL, always falls on E, at the end of which a paper disc can be placed. A mirror without this arrangement can be employed, the light falling on a paper strip, but is not quite so convenient. The monochromatic light was thrown on the micro r, and the angular deviation from the zero point read, the eye being fixed on a point along the zero reading. The experiments were made first with the ordinary luminosity of colours, and subsequently with the reduced. Scale No. Wave length. Temp. side. Nasal side. 56 52 47 56 52 47 23 6330 5996 5658 5330 5996 14° 14 15 14 14 side. 5658 white all over the field 4600 sees blue throughout. 10° 1 in L Square patch, 2-inch 11 10 10 [ Small round, spot, ^-inch diam. In the above, the angles show where colour was first visible. Case II. — The next two subjects are brothers (Alfred and William P., indicated below as P and Q), whose colour perception is mono- chromatic. Mr. Nettleship had previously tested them with wools, and the matches they made, such as matching yellow with blue, made it evident that their colour vision was very abnormal. The defect is not due to active disease, but they were born with it. They suffer from amblyopia. These cases were published as cases of " Day-blindness with Colour-blindness," by Mr. Nettleship, in the 'St. Thomas's Hospital Reports,' 1880 (vol. 10). Testing them with the spectrum, they made most extraordinary mistakes, calling blue, red ; red, green or blue. On cross-examina- tion, it seems that they only distinguish colour by its luminosity ; they always explain that one colour is lighter or darker than another ; evidently their colour names are founded on the observation of what is told them as to the different colours, and not from any real know- ledge of them. The next examination was to get their luminosity curve of the electric light spectrum, and this they did with the very greatest ease. Their readings for the same colour were occasionally a little erratic, differing as much as 5 per cent, from one another, but, by taking the means, their curves come out very concordantly Practically, the curves of the two brothers are identical, the means not differing 2 per cent, from one another at any part of the spectrum ; hence it is unnecessary to give more than one of them. It should be mentioned that both brothers could just catch a glimpse of the red line of lithium when the spectrum of the vapour was on the focussing screen of the apparatus. The luminosity curves are shown in the diagram, and the following is the table of observations : — 4 its Capt. W. de W. Abney. Examination for [May 14, 1. II. III. IV. V. Remarks. Scale No. Wtin- length. Luminosity to the normal eye. I.iitnino-itv to P and Q. IV. III. 55 6242 66 1-2 0-02 " Both blue." 54 6156 M 2-4 0-03 52 5996 97 9-6 o-io 50-6 5990 99 14-4 0-145 (D line). 48 5720 95 33-6 0-35 " Both white." 46 5596 86 62 5 0-73 44 5480 75 86-4 1-15 42 5370 62-5 92-6 1-49 40 5270 50 96 1-92 "Both white." (39'8, E line.) 38 5180 36 93-6 2-63 (38, "b" line.) 36 5080 24-5 86-4 3-38 34 4990 15-0 77-4 5-16 32 4910 8-5 60-0 7-06 30 4820 5-5 41-0 7-45 " Both blue." 25 4650 2-5 21-6 8-64 20 4510 1-4 9-6 6-85 10 4270 0-6 2-4 4-00 Their appreciation of light was — Abney P .... Q.... Right eye. . 23 . 23 15 Left eye. 25 16 15 We may take it that P's right eye has the same appreciation light as the standard, and his left 1*5 times that of the standard, is 1*6 times that of the standard with both eyes. The luminosit curves were taken with both eyes open. The cnrve is very remarkable, showing an intense excitement by the blue rays of the spectrum, the whole of which appears of one olour to both brothers. The maximum luminosity is about E, but 1891.] Colour of Cases of Tobacco Scotoma, 499 the place of the greatest difference in degree of luminosity, com- pared with the normal, is near F, where it is more than eight times more luminous than the normal eye. The area of their luminosity curve is 1800 ; that of the normal eye being 1650. If we take their appreciation of light as being 1'5 that of the standard, their lumino- sity curve should be 1650 by 1'5 or 2475. Theirs is 1800 as measured, the ordinates of their curve should therefore be multiplically 1'37 for a strict comparison with that of the normal eye. We may therefore take it that near F their sensation of light is 11*88 times that of the normal eye. In the three patients we have cases of abnormal vision, one in which practically the only sensations in the central part of the eye are white and blue, and in the other two there is only one sensation. In these last two cases we have apparently a curve of the funda- mental sensation, since it must be the same as the luminosity curve, and it appears to agree with that found by Koenig. In regard to Alfred C., it should be remarked that he begins to feel the blue sensation in the spectrum near the point where Koenig places its origin. Addendum. Received June 18, 1891. On Four Cases of Colour Blindness Examined for the Colour Vision Committee. Case III. — The next case, "W. S., is one of progressive atrophy of both eyes. When tested with spectrum colours — a patch of white light being placed in juxtaposition with the colour — it was found that he was absolutely blind to colour from 26'75 (A, 4733) on the scale of the spectrum to the termination of the red of his spectrum, which was close to 63 on the scale (A 7082). Above scale No. 26' 75 W. S. saw blue, and his spectrum was continued normally in the violet. Mr. Nettleship has promised to furnish a chart of his retina. His lumi- nosity curve (fig. 4) was made without any difficulty, and, compared with my own, is slightly deficient, from the red to the yellow, but his perception of luminosity increases as the blue is approached. The following is the table applying to his curve of luminosity : — 500 Capt. W. de W. Abney. Examination for [May 14, Scale No. Ware-length. Beading. Remarks by W. 8. 60 ana 34 Grey. H 6520 15-0 ,i 56 6330 41-0 .. 55 6242 43 N 54 6152 69 52 5996 94 50 5850 100 ,, 48 5720 96 45 5538 88 42 5373 74 40 5270 61-5 H 38 5172 45 35 5042 30 30 4848 12 ., 25 4675 6 Bluish. 20 4518 4 15 4376 3 Blue. 10 4248 2-5 He was subsequently tested with colour discs — Ultramarine (U), Red-royal (R), Emerald-green (G), Chrome-yellow (Y), White (W), and Black (B). It was found that — 165 (U) + 48 (R) + 147 (G) = 75 (W) + 285 (B). The black reflected 3 "4 of white ; hence the true equation is — (i). 165 (U) + 48 (R) + 147 (G) = 84-7 (W) + 275 (B). (ii). 120 (U) -|- 240 (Y) = 196 (W) + 164 (B) (corrected)— With 260 (U) + 100 (Y) he sees blue. 250 (U) + 110 (Y) „ light-blue. 242 (U) + 118 ( Y) „ no blue. This last in connexion with (ii) shows that his blue perception is 1891.] Colour of Cases of Tobacco Scotoma, §c. ,501 neutralised by the yellow, although the yellow to him was matched with white. The thin line curve is the normal curve. Case IV. — The next case is that of G., suffering from very well marked tobacco scotoma, occupying a considerable area. His curve of luminosity of the spectrum is shown in fig. 4. The following ' able refers to it : — 502 Capt. \V. de W. Abney. Examination for [May 14, Scale No. Wu length. Beading. Remarks by O. 57 0 55 6242 3 No colour. 5? 6074 11 Colour " yellow," white " blue." 51 .v.'l:> 34 » » » n 50 5850 80 >• » ii it 49 im 64 Colour " gold," white " sky-blue." 45 5538 59 40 5270 40 Both white. 35 5042 18 ,, 30 4848 10 11 29 4807 6 Colour " very pale blue," white as white. 26 4707 4 Colour "blue," white "white." 20 4518 3 ii ii ii >i 10 4248 2 i). it ii n G. was tested for light sense in the apparatus described in the previous memorandum. Light disappeared with Abney Bight eye. 5'° Left eye. 5° 5° 5° G. . 55-58-58 58-58 It thus appears that the final sensitiveness to light of the central part of the eye was nearly 12 times less than a person possessing normal sense. Case V. — This was a remarkable case, which Mr. Nettleship had mentioned to the Committee. He had stated that this lady, N. W., mistook blue for red, and it was with some curiosity that this case was examined. Her first examination was as to colour sense with the spectrum colours, a patch of mono-chromatic light being placed in juxtaposition with an equal patch of white light. At 62'5 (X 6890) of the scale the red of the spectrum disappeared. As the slit moved along the spectrum, and the white was approximately reduced to equal 1891.] Colour of Cases of Tobacco Scotoma, fyc. 503 luminosity, she described all the red as grey, and of the same colour as the white until 58'5 (X 6110), and after this point she said the colour was brownish compared with the white. The colour continued of this hue to her till 48 on the scale (A, 5720), when she said the colour was neither brown nor green, but both. From 48 on the scale she described the colour as green till quite sharply at 31*5 (A. 4905). In the blue she again began to see grey ; the grey at this end of the spectrum, and also of the white patch, she called brownish-grey. Scale No. "Wave- length. Beading. Remarks by N.W. 62-5 7019 0 Both grey. 60 6728 3 » 58 6520 10 i> 56 6330 30 'j 54 6152 52 Colour "brownish," white "grey." 52 5996 70 » >i » » 50 5850 81 ,, 48 46 5720 5596 87 90 Colour " brownish-green," white " grey." Colour "green," white "grey." 44 5481 88 V » 42 5373 82 ;» » 40 5270 62-5 ., 38 5172 46 v » 35 5042 23 » , " 32 4924 12-5 » » 31 30-5 4886 4862 10 8-5 Colour " brownish - grey," white " brownish-green." » » » )> 25 4675 ' 5 » >j » » 20 4518 3 u i) » » 15 4376 2-5 )> » » » 10 4248 1-5 >i >) i) » 0 4010 0-2 „ 504 Capt. W. de W. Abney. Examination for [May 14, This name must evidently have been a mental distinction, as si described the red end and the white as grey only, and not brown- grey ; and, indeed, she was tried again over that part of the spectrum, and adhered to the previous naming. It would appear to be due to the low luminosity which made the grey appear brownish to her, and not to any actual difference in hue. Her curve of luminosity in the spectrum was next taken, and her readings are given in the table. The curve is shown in fig. 5. The shaded band beneath it applies to her curve. My own readings were 1/1 '375 of the normal curve as shown in the diagram. The extinction of a gas-light, in my own case and that of Mr. Nettleship, was 13°'5. That of N. W. was 16°, showing that her final perception of light was 13'5/16 of what we may call the normal. An endeavour was made to form a series of colour equations with her eyesight by placing three slits in different parts of the spectrum, but without success, although a match with white was made in two posi- tions. One slit was placed in the orange-red at about 52 of the scale, another at E, and the third at Gr, and white light was formed, though her match was so erratic that it was useless to measure the apertures. When the slit in the violet was covered up, a white patch being along- side as a comparison, she called the mixture of red and green u brownish-green ; " when the slit in the red was covered she called the mixed light of green and violet "green;" and when the green Blit was covered up she called the purple colour a " different kind of brown." When the first slit was moved into the red near the lithium line she called the colours "green," whenever the green slot was uncovered. A piece of signal-red glass (London, Brighton, and South Coast Railway) was placed in the white reflected beam, forming a red patch, and a patch of the blue scale at No. 30*5 (X 4862) was placed alongside, and she matched them in luminosity and in colour. (The dominant colour of the signal glass in question was X 6220.) She finally was tested with colour discs : — One being in red with dominant wave-length . . X 6150 Another, emerald-green „ „ . . X 5373 And the third, French ultramarine „ . . X 4700. To make white she required 130 G + 113 R+117 U = 72 W + 288 B (corrected). She was then tried with the blue and green discs alone and made a match — 258 U + 102 G = 65 W + 295 B (corrected). An attempt was made to match with the green and red discs alone, but this failed. L891.] Colour of Cases of Tobacco Scotoma, 505 She matched the red disc alone with black and white, aud also the }lue disc alone — 360 E = 56 W+304 B (corrected), 360 U = 60 W + 300 B (corrected). any proportion of B and U mixed together she matched a grey approximately the same intensity as above, as it might be supposed she would from the last two equations. The thin line curve is the curve of luminosity for the normal eye. Capt. W. de W. Abney. Examination for [May 14, Taking the intensity carve of the light reflected from the red it was found to contain a great deal of the part of the spectrum which she called brownish, viz., from 53'5 to 48 on the scale, whereas the blue reflected a trifle of this portion of the spectrum, as did also the green, and this may account for her making a match to grey of U and G, and not of R and G, but it is hard to see why she matched U alone and also R with the grey. Reviewing the case, it seems that any perception of colour is very small, and that the sensations are green and red, together with white. Experiments which I have described in my book on " Colour Measure- ments and Mixture," 1891, show that a large proportion of colour may be mixed with white without being perceived, but this colour so hidden has still the capability of neutralising a certain quantity of the com- plementary colour thrown on the white, which, by itself, would not be masked by the white. It would seem then that in N. W.'s case the two colours perceived were very much diluted, and at parts of the spectrum so diluted as not to be perceived, but that the latent colour, if it may be so called, has the power of forming a grey with the green which she sees more strongly. Case VI. — This case is that of Miss W., who was brought before the Committee by Dr. Lindsay Johnson, on -April 29. The right eye was apparently normal for colour, but with the other she saw nothing but shades of white. Miss W., it appears, has had a slight stroke of paralysis, which affected her left side, and subsequently she discovered that colour sensation in the left eye had disappeared. Mr. Brndenell Carter, the day after the meeting of the Committee, examined her and pro- nounced hers to be a case of atrophy of the optic nerve. I examined her with the spectrum colours on the 5th May, and found her left eye totally blind to every colour, though her per- ception of light was very fair. She had very little difficulty in comparing the luminosity of the most brilliant spectrum colours with the white patch of light placed alongside them. In making the measurements she experienced a certain amount of fatigue, but, by resting the eye for short intervals, her readings were very constant. The following is the table of her readings : — 1891.] Colour of Cases of Tobacco Scotoma, fyc. 507 Scale No. Wave- length. Readings. Remarks by Miss W. 63 62 7082 6957 0 1 Both colour and white patch appeared as white throughout the spectrum. 60 6728 7 58 6520 18 57 6423 28 56 6330 43 54 6152 76 52 5996 90 50 5850 95 48 5720 93 46 5596 83 44 5481 71 42 5321 58 40 5270 46 38 5172 32 36 5085 21 34 5002 12-5 32 4924 7 30 4848 4-5 28 4776 3-0 25 4675 1-5 20 4518 0-4 19 4488 o-o At 19 the light perception was so diminished that she could not latch the grey. Her light perception extended further into the /iolet (as white) beyond this point, as the subsequent measures show conclusively. It seemed that it would be interesting to examine her eye for the extinction of light by the same method as that described in my recent japer. VOL. XLIX. 2 M 508 iidnation of Cases of Tobacco Scotonia, $c. [May The orange sodium light of the spectrum was thrown on the apparatus therein described, of a luminosity of an amyl lamp 1 foot off, and the slit giving this brightness remained unchanged through- out the examination, and was moved through the spectrum till a position was reached where all light was just extinguished. Her per- ception of the point of extinction was very acute. Rotating sectors were placed in front of the apparatus, as described in the paj referred to, set at different angles, so that the amount of reduction the luminosity of the spectrum was known at once. Scale readings of light extinction. Light coming through the slit reduced to — Slit moved towards the violet. Slit moved towards the red. No reduction. 15 53-7 i intensity. 207 52-4 i „ 217 50-9 i .. 23-2 48-7 T3 »> 267 46-7 •sV »» 34-7 44-2 A » — 40-0 The extinction of light with the full aperture to myself was at 2'1 and 57'9. At 57'9 the luminosity of the spectrum is 0*22 that at the D line, and as the light on the screen at the end of aperture is 1/620 that falling on the instrument originally, it follows that the extinction to myself was when the light of 57'9 (\ 6510) was 0'22/620 = 0'000355 of an amyl lamp placed at 1 foot from the screen. These details are given to show that the newer instrument used in these tests gives the same results as the older one, for with the latter it was 0-000350. The place in the spectrum where Miss W. last perceives light is the same as my own. The luminosity which is invisible to her is when 1'45/100,000 of an amyl lamp illuminates a screen 1 foot off. At D if 71/100,000 of an amyl lamp illuminated a screen I foot off it is invisible to her. With my own vision if the screen be illumi- nated with 7/100,000 of the same light it just becomes invisible. There is therefore a marked difference between the two sights as regarding initial perception of light. $91.] Limit of Visibility of the Rays of the Spectrum. 509 " On the Limit of Visibility of the different Rays of the Spectrum. Preliminary Note." By Captain W. DE W. ABXEY, C.B., R.E., D.C.L., F.R.S. Received April 29, 1891. In certain photometric experiments it became necessary to find the limit of visibility of the different parts of the spectrum, and also to ascertain what ratio this limit would bear to some fixed luminosity. It should be borne in mind that this question is totally different from acuteness of vision, which some have confounded with it. The two are independent one of the other, and can scarcely be compared. The instrument used in these experiments was similar to that described in the note on the examination of a case of Tobacco Scotoma, &c., but the dimensions were modified : — A square tube, 3 feet long, had an aperture of 2 inches cut in- its side at 2 feet •6 inches from one end, and covered over with ground glass. Within the tube, and close to the ground glass, was a mirror, which reflected the light coming through the ground glass on to the end of the tube, and if the ground glass was illuminated by any light the reflection illuminated a card placed at the end of the tube. The illumination of the card could be viewed through a circular hole at the other €nd of the tube, in which was fixed a smaller tube, fitting closely [into the eye. If a colour patch from the spectrum was thrown [on to the ground glass, evidently the card at the end of the tube would be illuminated by the colour used, and its disappearance could be effected by means of rotating sectors closing and opening at will, placed in front of the patch. This simple piece of apparatus iswered its purpose most effectively. The first point to ascertain was the ratio of illumination of the card that of the patch thrown on the ground glass. The following ingement was made to effect this. The end of the tube, linst which the card was placed, was removed, and a card with square hole, of f-inch side, was inserted instead. This was jvered on the side away from the tube with a piece of Saxe iper, and when viewed from the outside, and when illuminated the light from the ground glass, showed as a square patch of ;ht. Outside of this, and of double the width, but of the same jight, a mask of black paper, with an oblong aperture, was placed that the illuminated square occupied one-half of the oblong, and le other half showed no white paper. An amyl acetate lamp (O8 )f standard candle), placed at a fixed distance from this oblong, and a line with the axis of the tube, illuminated both squares ; but a placed in proper position cast a shadow on the translucent square, lowing only the opaque white half to be illuminated. When the 3tors above alluded to were placed in front of the lamp, the two 2 M 2 510 Capt. \V. de W. Abney. On the Limit of [May 14 brightnesses could be equalised, and the intensities of the light transmitted passing through the paper estimated. Now there is a ray very near D in the spectrum, whose colour i» very closely, if not quite, identical with the colour of the light emitted by the burning amyl acetate, and for making the measures this ray waa used. When the measure had been made, the screen, with the square aperture, was placed in the position of the ground glass, and the- amyl acetate lamp placed on the side of the screen, away from the- colour patch, and the rod placed in position to cast the shadow necessary. The rotating sectors were then placed between t' spectrum and the screen, and the light reduced so that the illnmi tion of the translucent and opaque white square, viewed from the side of the lamp, was equalised. Knowing the distance of the lamp the two cases, and the aperture of the sectors, the relative illumina- tion of the two surfaces was asceiiained. For convenience, the- aperture of the ground glass was limited by means of a diaphragm,, or by placing a diaphragm in front of the first prism. Two sets of measures showed that if the illumination of the ground glass be represented by 1, the illumination of the card at the end of the tube was -^ ; that is, any light falling on the ground glass wa* diminished to that extent. The actual measures were -^fa and yj-y , but we may take 7-^ as- sufficiently close to the truth. The colour-patch apparatus to which reference is made is described in the Bakerian Lecture, 1886 (Abney and Testing, " Colour Photo- metry"). The only addition to it that was made was to use an adjustable slit to move through the spectrum. There was thus a treble means of altering the intensity of the light, viz., by altering- the aperture of the slit of the collimator, by altering that of the slit of the slide, which was shifted at will into different parts of the spectrum,, and by the rotating sectors placed in front of the spectrum. The- mode of proceeding to measure the luminosity at which light disappeared was as follows : — The dullest part of that portion of the spectrum which it was desired to extinguish was allowed to pass through the slit in the spectrum, and a patch was form on the ground glass, which, it may be remarked, had a tn fitted over it, to prevent any chance of extraneous light reaching it. The card at the end of the square box was viewed, and the slits closed till all trace of light disappeared. (It may be as well to call to mind what is well known, that faint light of all colours appears as white.) In some sets of experiments the sectors were set at fixed angles, and rotated in front of the patch, and the slit in the spectrum moved from a position in which faint light appeared to one in which it just dis- appeared, the position in the spectrum being noted by the scale at the back of the moving slide carrying the slit.* In other cases the s L891.] Visibility of the different Rays of the Spectrum. 511 placed at different positions in the spectrum, and the rotating 3tors closed till all light had vanished, when the aperture was loted. The first plan is the more convenient of the two, and gives rery accurate results ; though in some positions of the spectrum the second method must be adopted, since the graphic curve formed from the readings becomes almost a horizontal straight line at one portion of the spectrum. As will be seen from the table, it is quite evident that no one aperture of the slit of the collimator and of that in the slide would suffice to give the entire range of disappearance of the spectrum, and that at least three settings are necessary. At each change the D light falling on the ground glass was measured, and the necessary factors to make the readings on one scale were derived from these measurements. Four sets of measures throughout the spectrum were made on different days. No one differed to any appreciable extent from the other. A mean of the four has been taken as representing the truth, and the measures given in the first table are those of that which most nearly approaches this mean. It may be stated that very rarely did one curve differ more than 4 per cent, from another at any portion •of the spectrum. The readings were taken when the eye had rested in darkness some time, and were often repeated a con- siderable number of times, the first parts measured being re- measured last. That the eye was equally sensitive throughout the time may be judged from the fact that the two sets of readings scarcely ever differed. The process of making these measures of ex- tinction is very fatiguing, and probably rather detrimental to the •eyesight ; owing to the strain on the eyes, one set of readings is usually as much as can be properly carried out on any one day, if Accurate results are to be looked for. It is now three years ago since I began this research, and, after trying various plans, I have come to the conclusion that the method now described is the most easy, as it is the most simple. There is one point in the method which might be open to criticism, .and that is that the cutting off the light by rotating sectors might iuse some error in the results. This criticism, I may say, I raised in my own mind at its very commencement, and found that it was innecessary. Polarising the light entering the slit of the colli- lator, and then dimming ib by means of a Nicol's prism placed in Dnt of the colour patch, proved an unsatisfactory method for an- swering the criticism, as in no case could a total disappearance of a aright light be brought about ; but by diminishing the area of the Dlour patch by placing different apertures of diaphragms in front of the last prism of the colour-patch apparatus (and thus throwing on the ground glass discs of light of various areas), the truth of the results •was readily verified. The two sets of measures, one made in this way 512 Capt. W. de W. Abney. On the Limit of [May 14r and the other as just described, gave identical results within th limits of the errors necessarily due to observation. The method adopted gave the extinction of light on the whole retina, for not only was the central part used, but the extinction wi carried so far that it was complete for every part of the eye. AM there is a considerable absorption in the yellow spot this is necessary, but the absorption exercised in this part of the eye, which occupies from 4° to 6° angular aperture, can be fairly measured if only the light on a small area be extinguished and this part of the retina be alone used. A very simple way of seeing the absorption of the yellow spot is to form a feeble spectrum some 3 inches long on ground-glass screen. If the eye looks at the green, a dark band ex- Table I. No. 1. No. 2. Scale No. Sector aperture. Sector aperture reduced. Scale No. Sector aperture. Sector aperture reduced. 55-2 5-3 54-0 9-3 53-2 10-6 62-3 13-3 51-3 15-9 60-5 16-3 50-0 17-3 48-4 19-3 45-4 26-3 180 » 90 » CO » 45 • 32 » 25 » 22-5 » 15 » 11 » 180 n 90 M 60 ii 45 » 32 » 25 M 22-5 » 15 M 11 » 57-3 2-1 55-9 4-3 54-1 8-3 53-1 12-3 180 » 90 » 38 20 » 456 >» 228 97 » 51 » Luminosity of patch on No. 2 = 2 '56 that of No. 1. No. 3. 60-8 :,••'• } 58-3 66-9 53 4 180 90 45 22-5 5 2700 1350 675 337 75 D light had to be reduced to 0-17789 its luminosity to equal the light from an amyl lamp at 48 cm. from the ground glass. Luminosity of patch No. 3 = 15 that of No. 1. 1891.] Visibility of the different Rays of the Spectrum. Table I — continued. 513 No. 4. No. 5. Scale No. Sector aperture. Sector aperture reduced. Scale No. Sector aperture. Sector aperture reduced. 52-3 14-3 49-8 17'3 44-3 26-3 43-3 35-3 25-3 30-3 34-3 38-3 180 » 90 » 45 M 40 >» 45 43 40 37 45 » 22-5 »> 11-25 » 10 » 11-25 10-75 10 9-2 61-9 60-9 60-2 59-0 57-6 56-5 180 90 60 30 15 9 6000 3000 2000 1000 500 300 Luminosity of patch in No. 5 = 22 "2 times that of No. 1. A measure showed that 63 required double the aperture of 62 to be ex- tinguished. Luminosity of patch in No. 4=0 '25 that of No. 1. tending to the blue will be seen, but if the eye be turned towards the red end or violet, the green is seen outside the central spot and the colour reappears. I propose to return to this in a fuller discussion of the subject. The first table shows the actual observations in the spectrum. 514 Capt. W. de W. Abney. On the Limit of [May H, 18 ill.] Visibility of the different Rays of the Spectrum. 515 The second table attached shows the extinction of light of a luminosity of one amyl lamp placed at a foot from the screen. It Table II. Extinction of Rays of Equal Luminosity, the Luminosity being 1 Amyl Lamp at 1 foot from a Screen. Scale No. X. Reading. Luminosity of rays. Extinction of equal luminosities. TtniWo °f an amyl lamp Lft. off screen. 63 7082 13,000 1 13,000 36-11 62 6957 6,400 2 12,800 35'5 61 6239 3,100 4 12,400 34-4 60 6728 1,800 7 12,600 35-0 59 6621 1,000 12-5 12,500 34-7 58 6520 600 21 12,600 35-0 57 6423 380 33 12,540 34-8 56 6330 240 50 12,000 33-3 55 6242 160 65 10,400 29-0 54 6152 100 80 8,000 22-2 53 6074 55 90 4,950 13-75 52 5996 38 96 3,640 10-11 51 5919 28 99 2,772 7-70 50 5850 21 100 2,100 5-83 49 5783 17 99 1,682 4-65 48 5720 16 97 1,552 4-31 47 5658 14 92-5 1,294 3-59 46 5596 12-4 87 1,078 2-99 45 5535 11-6 81 906 2-517 44 5481 10-0 75 750 2-083 43 5427 9-8 69 686 1-905 42 5373 9-6 62-5 600 1-666 41 5321 9-6 67 546 1-516 40 5270 9-6 50 480 1-333 38 5172 9-6 36 346 0-911 36 5085 9-8 24 236 0-655 34 5002 10-0 15 150 0 -4166 32 4924 10-2 8 82 0 -2277 30 4845 11-0 5-5 50 0 -1388 28 4776 11-2 4 43-6 0-1166 26 4707 11-6 3 35 0-0972 24 4643 12-0 2-2 26-4 0-0733 22 4578 12-4 1-6 20 0 -0555 20 4519 14-0 1-4 18 0-0500 18 4459 18 1-2 21-6 0 0600 16 4404 26 0-9 23-4 0-0650 14 4349 36 0-7 25-2 0-0700 12 4298 50 0-6 30 0 -0833 10 4247 70 0-55 36-4 0-1011 8 4197 104 0-5 52 0-1444 6 4151 160 0-4 64 0-1777 4 4105 240 0-35 84 0-2333 2 4058 350 0-3 105 0 '2916 0 4010 516 Capt. W. de W. Abney. On the Limit of [May 14, IBBBBBBBBrJBBBBBBIIBBBBBB«BHBBJ IB'JI IB IB BffJBI BBI IBflB IIBI •VBBBBBBBlJBBBflBBBBIBBI •Ml BIIBBBBI IBriBBBBBBBriBfl BBflBBBBBBBBBBBBlBBBBBBBBBBBBBB wtW-trnw [BBBBBBBIIBII juu""/ ,enqffix ~w\\\ be seen that the extinction of the red rays is effected when they are reduced to about 36/100,000 of this standard, whilst the rays near F require a reduction of 5/10,000,000, that is, the sensitiveness of the eye is 700 times greater for the latter colour than the former, and this has a bearing on the extinction of white light of different qualities. It is worthy of remark that the reduction of the rays from about C to the visible limit of the red necessary to cause extinction from the standard luminosity is practically the same, and points to the fact that this part of the spectrum is probably monochromatic ; if admix- ture of any other colour sensation were present, the curve would rise or fall instead of remaining horizontal. The same apparently applies to the violet end of the spectrum, though, owing to the small luminosity, exact measures of it are less certain. The experiments show that the rays having the wave-length of about X 4770 are the last perceived. The shift in the position of maximum resistance to 1891.] Visibility of the different JRays of the Spectrum. 517 about X 4510, as shown in Table II, is due to the fact that equal luminosities of each colour have been considered as being reduced. Some interesting experiments were carried out by placing slits in different parts of the spectrum, and forming a mixture of light on the ground glass of the apparatus. An intense D light mixed with a faint light near F formed a colour patch, and this mixed light was extinguished and found to require 9° of aperture of the sector. The D light was then shielded and the single ray of blue-green light was extinguished, when it was found that the same aperture was required to extinguish this beam alone. Red and green and various other mixtures were tried, all showing that in the extinction of light the green-blue light was the last visible, and was equivalent to extin- guishing that light alone, although it might be mixed with very much brighter light in the red or yellow. In the blue the conditions somewhat change, as will be seen in the diagram, but if slits of equal aperture were used the same results were obtained. The diagram shows that in the spectroscopy of feeble light the rays in the blue and green are the first to be perceived, and that rays of far greater intensity in the yellow and red may exist without ex- citing the sense of light. This may account for some of the varied results recorded in eye spectroscopic observations of sources of feeble luminosity, in which the yellow and red lines are absent. In extinguishing white light, the fact of the total extinction of the blue-green light is of importance. It is not the light at that particular wave-length which disappears last, but some one sensation which is principally existent at that point, but which extends over a great portion of the spectrum which has to be extinguished. For instance, in extinguishing the light from the reflected beam of the electric light already alluded to, it was found that the light illuminating the ground glass was 720 times brighter than that reaching the screen. To extinguish 0'014 of the light from an amyl lamp on the ground glass the sector had to be closed to 21, that is the light of one amyl lamp luminosity, falling on the screen at 1 foot distance, had to be reduced to 14 1 21 1 x ^571 x T57^ or 77T-t ^ o£ the original light. Had the luminosity 1UOO 720 180 441,000 of the unit of luminosity been due entirely to the colour at X 4776, it would have had to be reduced to about oooVoo of its luminosity before it became invisible. Thus the electric light gives about half the sensation of this light that the monochromatic light of that colour and luminosity would give, and hence we may conclude that about half the luminosity of the white light is due to this sensation, of course distributed unequally through its spectrum. This is a very- close approach to the area of the green sensation curve of the spectrum when the luminosity is taken into account. 518 Prof. H. G. Seeley. On the Strw [May 14, It would thus appear that by studying the extinction curves it may be possible to approximate to the three positions in the spectrum which the colours giving the nearest approach to the three fuuda- mental sensations on the Young-Hetmholtz theory occupy. III. " Researches on the Structure, Organisation, and Classifica- tion of the Fossil Reptilia. VII. Further Observations on Pareiasaurus" By H. G. SEELEY, F.R.S., Professor of Geography in King's College, London. Received May 5, 1891. (Abstract.) The author distinguishes five zones of life in the Karoo rocks, which are termed, counting from the bottom, Mesosaurian, Pareia- saurian, Dicynodont, Theriodont, and Zanclodont. The Pareia- saurian zone extends between the Prince Albert Road station and the Nieuwveldt range of mountains. He obtained a nearly complete skeleton from Bad, east of Tamboer, a less complete skeleton from Tamboer Fontein, and a portion of jaw from near Klipfontein, on the summit of the Nienwveldt range. These materials show almost every part of the skeleton except some details of the carpus and tarsus, and the number of digits. The skull shows in both specimens the structure of the palate, which was closed in the median line, and almost covered with teeth, which extend in four principal longitudinal rows on the vomera and pterygoids. The teeth are slender, cylindrical, and recurved. There are two oblique rows, half as long as the others, on the palatines. They converge backward. Other teeth occur in rows behind these, and in front of them. The posterior nares open behind the pterygoids on the basi-sphenoid. The pterygoid bones diverge backwards to meet the quadrate bones, which are wedged in between them and the bones of the cheek. On the outer border of the side of the quadrate is a perforation like that figured ' Phil Trans.,' B, 1889, PI. 10, fig. 4, only smaller. The brain case has the same sort of relation to the roof bones of the skull, as in marine Chelonia. The brain case is depressed behind. The occipital condyle appeal's to be formed by the basi-occipital in its lower half, and by the ex-occipitals in its upper half. It is concave, and was margined below by a semi- circular intercentral bone. A similar intercentral ossification occurs behind it, below the atlas. The surface of the skull has no opening except the nares, orbits, and the large parietal foramen. Its posterior border is concavely notched. The surface shows the same pitted and channeled ornament as in the specimen already described. The vertebral column is complete with the exception of a few small terminal vertebrae of the tail. No neural arch has been found to the 1891.] Organisation, and Classification of Fossil Reptilia. 519 first vertebra. The processes for articulation with the dorsal ribs have elongated facets, which are rarely divided into diapophyses and parapophyses. The sacrum, includes four vertebrae, of which the first is sacro-lumbar and the last two sacro-caudal. Chevron bones are well developed along the tail. The shoulder girdle is placed far forward ; the precoracoid, cora- coid, and scapula are anchylosed together. The scapula is expanded and elongated, extending backward towards the ilium. The clavi- cular arch includes five bones. The interclavicle has a descending median bar, which expands transversely between the coracoids ; its transverse bar unites with the clavicles, which rest upon the scapulae. They only extend half-way along the length of the superior margins of the scapulce. Beyond that point is another pair of bones which represent the supraclavicles, as in Fishes and Labyrinthodonts. The pelvis is entirely Mammalian in form. The pubes are almost entirely behind the iliac bones, and unite with the ischia to form a continuous sheet of bone, the two sides being inclined to each other and meeting in a ventral symphysis. There is only a small perfora- tion through the pubis, and no perforation between the pubis and ischium, as in Mammals. The transverse processes from the four sacral vertebrae meet the expanded blade of the ilium along its length on each side. The limbs are massive and short ; the femur shows characters which have previously been regarded as belonging to the humerus. The distal end of the bone is perforated. The lesser trochanter is strongly developed. The tibia is large and massive, and the fibula slender. These bones are much shorter than the femur. The os calcis is of large size, and articulates with both the fibula and tibia ; the astragalus is small. The tarsal bones of the distal row are small and separate ; their relations to each other not definitely determined. The metatarsal bones are strong and short; the phalanges are short, and terminate in massive, long, flattened claws. In the fore-limb the humerus is greatly expanded at both ends with a large deltoid crest. The condyles of its distal end are well rounded ; the radius is short and massive ; the ulna expands at its proximal end, and is produced according to the Mammalian plan so as to receive the distal end of the humerus. The carpus is imperfectly known. The digits were stronger than those of the hind limb, and terminated in similar claws. The specimens show that in characters of the teeth and mandible there is nothing to distinguish Anthodon from Pareiasaurus ; and that the genus Propappus apparently has no existence, being founded on a femur. One species is named Pareiasaurus Sainii, another is Pareiasaurus Hussauwi. All the affinities hitherto attributed to Pareiasaurus with Labyrinth- odonts, Anomodonts, Procolophon, and Mammals are shown more 520 On the Structure, fyc., of the Fossil Reptilia. [May 14, strongly in the several parts of the skeleton, by the new evidence. The shoulder girdle is more Labyrinthodont than was previously supposed, the skull is more Reptilian, and the pelvis and limbs are more Mammalian, though with some resembance to Dinosaurs. From further evidence of the structure of the skeleton in Procolo- phon, the author regards that type as a member of the Pareiasauria, rather than as forming a distinct sub-order. It also has four sacral vertebrae. The divisions of the Anomodontia are grouped as — Theriodontia. Placodontia. \ Dirvnodontia. Endotbiodontia. / \ Pareiasauria. Mesoaauria. The relations of the Auomodontia to other Vertebrata are expressed in the following grouping : — 1891.] On the Theory of Electrodynamics. 521 IV. " On the Theory of Electrodynamics." By J. LARMOR, Fellow of St. John's College, Cambridge. Communicated by Professor J. J. THOMSON, F.R.S. Received May 11, 1891. The electrical ideas of Clerk Maxwell, which, were cultivated partly in relation to mechanical models of electrodyuamic action, led him to the general principle that electrical currents always flow round com- plete circuits. To verify this principle for the case of the current which charges a condenser, it was necessary to postulate an electrodynamic action of the same type as that of a current for the electric displacement across the dielectric, in which the excitation of the dielectric may be supposed, after Faraday, to consist. The existence of such an action has subsequently been deduced qualitatively from the general prin- ciple of action and reaction,* and has also been detected by various experimenters. The principle also requires that the electric displacement shall not lead to any accumulation of charge in the interior of the dielectric, therefore that it shall be solenoidal or circuital, f its characteristic equation being of the type dx \ dx ) dy\ dy J dz \ dz ) where V is the electric potential, and K a dielectric constant. The surface density of the electricity conducted to a face of a condenser must neutralise the electric displacement, and not leave any residual effective electrification on the surface. On taking the displacement and the surface density each equal to KF/4n-, where F denotes the electric force, the value of K becomes unity for a vacuum dielectric ; and K represents the specific inductive capacity as measured by electrostatic experiments. When this principle of circuital currents is postulated, the theory of electrodynamics is reduced to the Ampere-Neumann theory of complete circuits, of which the truth has been fully established. It leads, as shown by Maxwell, to the propagation of electrical action in dielectric media by waves of transverse electric displacement, which have the intimate relations to waves of light that are now well known. * Cf. J. J. Thomson, 'Brit. Assoc. Report,' 1885. t A term recently introduced by Sir W. Thomson. 522 Mr. J. Larmor. [May 14, Generalised Polarisation Theory. The problem of determining how far these remarkable conclusions will still hold good when a more general view of the nature of di- electric polarisation is assumed was considered by von Helmholtz* in a series of memoirs. The most general conception of the polarisation of a medium which has been formed is the Poisson theory of magnetisation. The magnetised element, whether actually produced by the orientation of polar molecules or otherwise, may be mathematically considered to be formed by the displacement of a quantity of ideal magnetic matter from its negative to its positive pole, thereby producing defect at the one end, and excess at the other end. The element is defined mag- netically by its moment, which is the product of the displaced quantity and the distance through which it is displaced. The dis- placement per unit volume, measured by this product, is equal to the magnetic moment per unit volume, whether the magnetised mole- cules fill up the whole of that volume or are a system of discrete particles with unoccupied space between them. In the electric analogue we replace ideal magnetic matter by ideal electric matter ; the displacement thus measured constitutes the elec- tric displacement, and its rate of change per unit time represents the displacement current in the dielectric. We have to consider whether a displacement current of this type suffices to make all electric currents circuital ; and it will be sufficient and convenient to examine the case of a condenser which is charged through a wire connecting its two plates. In the first place this notion of electric displacement leads to the same distribution of potential between the plates as the ordinary one, adopted by Maxwell ; for in the theory of induced magnetism there occurs a vector quantity of circuital character, the magnetic induction of Maxwell, of which the components are — /t((fV/rfx), —ft(dVjdy), —p(dVjdz), and which, therefore, leads to the characteristic equation of the potential A/ *T\+d-( d^\+jL( ^Y\ — o dx \ dx / dy\ dy / dz\ dz / corresponding to the one given above. If the displacement in the dielectric is — *(dV/ therefore, by Coulomb's principle, •F = 47Tr) Jj ' \~i* ds cb'~r ~ds ds'~rdt ~di ds da ~ fi * I* /j ' I dr f i » ,*•' j , 1 dr = - \\&r\ t'dsi- — - \\tr\ dsi- — J I "% rMy V r da wv This variation is accounted for- by the following forces of repulsion, tending to increase r. (i) Between the elements ids and ids', equal. to , , , / 1 Jr dr 2 (Fr f{cos e— | cos ^ cos 0'), Ampere's law. 3 (ii) Between, the element ufe. and the positive end of the con- ductor de't , ,1 dr , tdn - — , r o» or , de 1 , , , — ids cos (r . ds), dt r where dc' fdt is the rate at which the charge at that end is increasing, (iii) Between the element: ids' and the end of the conductor ds, , , , I dr t (IS I ;, r dg" or t'ds'- I cos (r. d»"), r being here measured away from ds'. (iv) Between an end of one conductor and an end of another con- ductor, or dede ' dt dt (1-0'r). 1891.] On the Theory of Electrodynamics. 527 It is to be observed that the form of 0(r) affects only the forces (iv) in this scheme of attraction, as one would expect from the fact that 0(r) disappears if either current flows round a complete circuit. Not to refer to (ii) and (iii), we notice from (iv) that two changing electrifications attraet each other with a force involving a term which is constant at all distances, unless a special form of 0 (r) be assigned differing from any of the values which occur in. the sequel. It is difficult to imagine- the mechanical basis of such an action ; the remarks of von Helmholtz in justification (against Bertrand) may, however, be referred to.* This investigation of the mechanical forces is equivalent to von Helmholtz's with the exception .that he takes at the beginning 0(r) to be proportional to r, on the general grounl that the potential energy of two elements in all natural actions involves only the inverse first power of the. distances • The validity of this consideration seems to be weakened by the fact noticed above that 0(r) occurs only in the force (iv). For what follows it will not be necessary to restrict the form of 0(r). To discuss the propagation of electrical action in continuous media, we have to trans-late T from the -form suitable to linear -distributions to the form suitable to volume distributions. Following the method first developed by Kirchhoff, and -for this case the analysis of von Helmholtz, the energy function for any field of currents- is to be obtained by summation of the energy functions of all the pairs of elementary filaments of currents that compose it, care being taken that no pair is counted twice over. The proper form will be a volume integral ; instead of ds, ds',the elements of the filament, it will involve dr, d-r\ the elements of volume, and instead of «,».«', the resultant currents, it will involve their components per unit sectional area uvw and u'v'w' ' . mi m f ids ids' cos e • if d , d ,, >. , , / I hus T — ---- j_ | « t' — . 0(r) ds ds JJ r jj ds as r r * =-i| I - (uu +vv'''-\-ww) d-rd-r JJ r the factors \ being inserted because the volume integrals, being extended all over the system, take each pair of elements twice over. Hence * ' Wissen. Abbandl.,' I, p. 708. 528 Mr. J. Larmor. [May 14, where F = (± dr. G = (L dr't H = tl rfr". K, d0 , , d , ,d0\ , , tt —?—.+ V —Z--I.V} — !- \(ir ; dx'^ dy dz ) in these formulae the accents may now be dropped, as the integrals are extended over the whole system. It is through this function x that the indeterminateness enters into the equations of electrodynamics. In a certain class of cases the function may be expressed in another form, which is useful in the subsequent analysis. By integration by parts throughout space, we obtain (d A = J ' *' provided we can neglect* tte surface integral over the infinite sphere ; and this we can do, if the system is confined to a finite region and

= — (P, Q, R). The vector potential FGH is connected by definition above with nvw by the equations of potential V2(F,G,H) = -4,r(W,V,«;); while the characteristic equation of V is /df dg dh \dx dy The equations of electric propagation are involved in these results. Mr. J. Larmor. [^a}r 14-. The value of KI in electromagnetic units is very small, the square of the reciprocal of the velocity of light in the medium ; so that there are, broadly, two classes of media, (i) , conductors in which KI is neglected, (ii) insulators in which UiV\w\ are zero. The equations of propagation for each case are involved in, the above equations. Propagation in Dielectric Media. The simplest and most important case of this generalised theory, as displacement currents in conductors are negligible, is that of dielectrics. In the first place, .we may consider the propagation of V. We have \dx dy dz Now ™L+™+™ = fl^+*!+*F 4» ^ dy * dz J /• U« dy ^dz r dt dV ~dt ™ t 2TT (PV d Therefore _V -^ ^, n wnich 0 is a function of'r. This equation determines the mode of propagation of V. It repre- sents wave-motion of a complicated character which may be analysed most easily by applying the equation to the case of a plane wave with the displacement at right angles to its front. There are two com- paratively simple cases. (i.) If vV = 0» »'•«•! 0 = A + Br~', the equation becomes K, dt- which represents wave propagation with velocity depending on the wave-length, and therefore involving dispersion. 1891.] On the Theory of Electrodynamics. 531 For the plane wave V oc exp i (mx—nt), it leads to the condition K, and the velocity of propagation is where X is the wave-length! The special case of 0(r) equal to zero is worth notice, as that would represent a theory in..whicb the element of Neumann's in- tegral, viz., ids i'dy a constant Ki/4w. For the indeterminateness that may exist in the vector potential (or electric momentum) PGH is of the same type as that which may exist in the electric force PQR, and, therefore, as the equations show, may be merged in the latter. It would, perhaps, be difficult to conceive any more general hypothesis than this. The increased generality which can be imparted to the theory merely leads to .-various modes of .propagation of a condensational wave. cCorpp orison with Experimental Knowledge. In the general theory, of polarisation sketched at the beginning of this paper, therefore KI The specific inductive capacity of v the medium is K2 = /t = l-f-45r«r. Thus Ka the units being here electrostatic. Now, the results of various experimental investigations seem to place it beyond doubt that for dielectrics of simple chemical consti- tution the velocity of propagation varies as K2~*. Thus, in the recent experiments of Arons and Rubens,* the velocity of waves, 6 metres * Wiedemann's ' Annalen,' vol. 42, 1891, p. 581. 534 Mr. J. Larmor. long, guided by a pair of parallel wires, was measured by interference experiments when a part of Ihe circuit was surrounded by various liquid dielectrics. The great length of the wave compared with the section of the conductor ensures that it travels with its front sensibly in the direction of propagation, and, therefore, that its velocity is normal ; while the presence of the return wire limits its divergence into space. Their results are expressed in the following table which gives Kj*, the index of refraction m for light waves of length 6.10~7 metres, and the index of refraction m' for the observed waves of about 6 metres long : — K.4. M. m'. Castor oil 2'16 1'48 2'05 Olive oil 1-75 1'47 1-71 Xylene 1-53 Iv49 1'50 Petroleum ] -44 1"45 1'40 Thus the greatest, deviation from correspondence for the longer waves is about 5 per cent. The- correspondence of these numbers requires that the values of Kt and, K2 should be sensibly equal for the substances tested, which can only be the .case in the limiting form of the polarisation theory which constitutes Maxwell's dis- placement theory. . In that case, as has been .seen, the currents are all circuital; the Ampere-Neumann theory of electrodynamics suffices for all purposes, and there is -no condensational wave. The stand- point from which the theory of dielectric polarisation has been generalised in the theory here expounded is that of polar elements attracting according to the law of inverse squares in the manner of small magnets. In the results, however, this conception disappears and the phenomena are all expressed iu the continuous manner by means of partial differential equations! It is also possible, in Maxwell's manner, to ignore the attractions of the elements from the beginning, and simply to define the displace- ment as proportional to the. electric force. The statical theory of condensers shows that in the dielectric the displacement must be circuital, for the characteristic equation- of the potential must hold good. The displacement constant assumed by Maxwell is equal to the specific inductive capacity, in ordeT to ensure that the charging current shall be continuous across the faces of a condenser. It might be proposed to take a less restricted form for this constant, with the result, of course, tliat the currents would be non-circuital. The in- vestigation of this paper, however, proves that in all cases the velocity of the waves of transverse displacement is specified iu terms of this displacement constant ; and the experimental fact that in the simpler media it is determined in the same manner by the specific inductive capacity confines us to that value of the constant which is assumed 1891.] On the Theory of Electrodynamics. 535 by Maxwell.* It is necessary to emphasise that it is of the very essence of a theory of this kind that the current in the dielectric is not circuital, and, therefore, that the electric volume density pro- duced by the electric displacement varies with the time. This is so because the electrodynamic part of the electric force is not derived from a potential. Any investigation which restricts the current to be circuital is necessarily inconsistent with itself, except for the limiting case which forms Maxwell's theory. A discrepancy of n per cent, (n a small number) between the observed velocity and K2~* would involve, by the formulae at the beginning of this section, a difference of about 2n per cent, between K2 and K2 — 1, so that K2 would be of numerical magnitude about 100/2%; which determines the ratio in which the ordinary values of the inductive capacities of all media, including vacuum, would have to be multiplied, to make the polarisation theory not discordant with the observations. The amount of discontinuity in* the current at the surface of a conductor is the fraction K2-1 of the total current across the surface. At the interface between two dielectric media, denoted by the values K2 and K'2, the normal components - of the displacement -on the two sides are (K2— l)N/47r and (K'a— where N, N' are the normal components of the electric force, so that •'K2N = K'2N'. Thus the discontinuity in the displacement is ' (N'— N)/4?r or (K2/K'2^-l)N/47r compared with a total displacement (K2— l)N/4jr; the ratio of these is (K2— K'2)/K'2(K2 — 1), which is less than the fraction K'2-1, which corresponds to the surface of a conductor. Thus, under the assumed circumstances/ the ratio of the amplitudes of the condensational waves to those of the transverse waves would have a superior limit of the order1 2«/100; in the observations quoted this limit is at 5 per cent. It is worth while to emphasise that if the polarisation theory were to take K2 equal to unity for a vacuum, K! would be zero, and in a vacuum there would be nothing but action at a distance. It is thus an essential part of a theory like this that a vacuum has an absolute inductive capacity greater than unity, so that the ordinary value unity is merely a relative unit. Thus the transition to Maxwell's scheme, where the absolute coefficients are all assumed infinite, does not involve any undue stretch of the original hypothesis. In the above, the relative velocities in different media of the * Cf. J. J. Thomson, ' Brit. Assoc. Keport,' 1885, p. 140. 536 Presents. [May 14, transverse waves have been considered. The absolute velocity in a vacuum must take account of the fact that the ratio of the electro* static and electromagnetic units of quantity has been altered by the factor K'2* in the transition to Maxwell's theory, where K', now represents the assumed absolute inductive capacity of the vacuum : thus the velocity for vacuum is (l — K'rl)~* multiplied by the ratio of the electric units in vacuum, agreeing with von Helmholtz's result,* on writing this inductive capacity K'2 for his constant 1+4 *•*<>, and exceeding the velocity of light unless K'» is very great. The theory of electrodynamics would thus appear to be, on all sides, limited to Maxwell's scheme, which has also so much to recommend it on the score of intrinsic simplicity. The Society adjourned over the Whitsuntide Recess to Thursday, Mav 28. Presents, May 14, 1891. Transactions. Cracow : — Academic des Sciences. Bulletin International. Comptes Bendns des Seances. 1891. No. 3. 8vo. Cracovie. The Academy. Paris : — Bibliotheque du Depot de la Guerre. Catalogue. Tome VII. 8vo. Part? 1890. Ministere de la Guerre, Paris. Rome : — Reale Accademia dei Lincei. Atti. Serie 4. (Classe di Scienze Morali, Storiche e Filologiche). Memorie. Vols. II-V. 4to. Roma 1886-88. The Academy. Salford : — Museum, Libraries, and Parks Committee. Annual Report, 1889-00. 8vo. Salford. The Committee. Stockholm : — Kongl. Vetenskaps-Akademie. Ofversigt. Arg. 48. No. 1. 8vo. Stockholm 1891. The Academy. Tokio : — Universitat. Mitteilungen aus der Medicinischen Facultat. Bd. I. No. 4 4to. Tokyo 1890. The University. Toulouse : — Facnlte des Sciences. Annales. Tome IV. Fasc. 2. 4to. Paris 1890. The Faculty. Turin: — R. Accademia delle Scienze. Atti. Vol. XXVI. Disp. 1-3. 8vo. Torino 1890-91 ; Osservazioni Meteorologiche. 1890. 8vo. Torino 1891. The Academy. Utrecht: — Provinciaal Utrechtsch Genootschap van Kunsten en Wetenschappen. Aanteekeningen van het verhandelde in de Sectie Vergaderingen. 1890. 8vo. Utrecht. The Society. Vienna : — Anthropologische Gesellschaft. Mittheilnngen. Bd. XXI. Heft 1. 4to. Wien 1891. The Society. * Loc. tit., p. 627. 1891.] Presents. 537 Transactions (continued}. K. Akademie der Wissenschaften. Anzeiger. 1891. Nos. 5-7. 8vo. Wien. The Academy. K.K. Geologische Reichsanstalt. Verhandlungen. 1891. Nos. 2-4. 8vo. Wien. The Institute. Journals. American Journal of Philology. Vol. XI. No. 4. 8vo. Baltimore 1890. The Editor. Archives Neerlandaises des Sciences Exactes et Naturelles. Tome XXIV. Livr. 4-5. 8vo. Harlem 1891. Societe Hollandaise des Sciences, Harlem. Galilee (Le) 1891 . Nos. 5-7. 8vo. Paris. The Editors. Horological Journal (The) Nos. 391-392. 8vo. London 1891. The Horological Institute. Naturalist (The) Nos. 188-189. 8vo. London 1891. The Editors. Nature Notes. Vol. II. Nos. 15-16. 8vo. London. The Editor. Re vista Argentina de Historia Natural. Tomo I. Entrega 1. 8vo. Buenos Aires 1891. M. Florentine Ameghino. Revista do Observatorio. 1891. No. 2. 8vo. Rio de Janeiro. The Observatory, Rio de Janeiro. Revue Medico-Pharmaceutique. 1891. Nos. 2-3. 4to. Con- stantinople. The Editor. State Library Bulletin. Comparative Summary and Index of State Legislation in 1890. 8vo. Albany 1891. University of the State of New York. Stazioni Sperimentali Agrarie Italiane (Le) Vol. XX. Fasc. 1-2. 8vo. Asti 1891. R. Stazione Enologica di Asti. Technology Quarterly. Vol. III. No. 4. 8vo. Boston 1890. Massachusetts Institute of Technology. Carruthers (G. T.) The Variation of the Magnetic Needle at Paris. 8vo. [West Brighton] 1891. The Author. Jones (T. R.), F.R.S. On some more Fossil Estherise. 8vo. Hert- ford 1891 ; On some Estheriae and Estheria-like Shells from •the Carboniferous Shales of Western Scotland. 8vo. [Glasgow 1890] ; Seventh and Eighth Reports (1889-90) of the Com- mittee on the Fossil Phyllopoda of the Palaeozoic Rocks. 8vo. [London'} ; On some Fossils from Central Africa. 8vo. Hert- ford 1890 ; On some Bivalve Shells from the Karoo Formation. South Africa. 8vo. Hertford 1890 ; Obituary Notice of Mr. H. B. Brady. 8vo. Hertford 1891. Professor Jones. On the Bases (Organic) in the Juice of Flexh. [Nfay 28, Schram (R.) Ueberdaa Stundenzonen-System der Amerikanischen Eiseiibahnen. 8vo. Wien 1890; La Zona Oraria dell' Adriatico. 12mo. Trieste 1890; Anslandisdic Stimmeii uber die Adria^eit. 8vo. Wien 1890; The Ac-taal State of the Standard Time Question. 8vo. [Lumlon] 1890. The Author. Sergueyeff (S.) Le Sommeil et le Systeme Nerveux. Physiologic de la Veille et'du Sommeil. ' Tomes' I-II. 8vo. Par It 189' ». The Author. Wolf (R.) Astronomischfi Mittbeilungen. "December. 1880. 8vo. [Zurich.] vThe Author. Portrait Medals in bronze of P. J. van Beneden and F. Tiedemann. Sir James Paget, Bart., F.R.S. A series of Photographic Studies of the Normal Solar Spectrum. Mr. George Higgs. "May 28, 1891. Sir WILLIAM THOMSON, D.C!L., Lli.D./President, in the Chair. The Presents received were laid on the table, and thanks ordered for them. The Rev. A. M. Norman (elected Jane 5, 1890), was admitted into the Society. The following Papers were read : — I. "On the Bases (Organic) in the Juice of Flesh. Part I." By GEORGE STILLINGFLEET JOHNSON, M.R.C.S., F.C.S., F.I.C. Communicated by Professor G. JOHNSON, F.R.S. Received April 28, 1891. (Abstract.) The author has endeavoured to ascertain by careful experiments how far the substances hitherto prepared from flesh are true " eductt," and really present in the flesh itself, or merely products, due to (1) the action of chemical or physical agencies applied in the course of extraction, or (2) to bacterial action modifying the composition of the flesh before it comes into the hands of the operator. 1891.] Dr. F. Evans' Paper on the Fungus of Malaria. 539 Preliminary experiments are first described bearing chiefly upon the first-named source of error. Liebig's process for extracting kreatine from the juice of flesh was modified by omitting the use of baryta-water, with the result that abundance of kreatine was obtained, mixed with acid potassium phosphate (KH2P04). In Liebig's process potassium chloride is obtained after the kreatine has been separated. A preliminary experiment is then described in which the author precipitated the albuminoid matters from the watery extract of fresh butcher's beef by means of solution of mercuric chloride, the filtrate depositing on standing a spherical precipitate, consisting of the mercury salt of the sarcous kreatinin. from which a tabular kreatinin was obtained isomorphous with the tabular kreatinin obtained by the author from human urine in 1887. The special advantages of the method adopted by the author in isolating the kreatinin of urine are next detailed, after which a series of experiments are described in which muscle substance in different stages of freshness was extracted with water, the extracts treated by the mercuric chloride method, and. the products compared. Among these products is sarcous kreatinin, whose properties are fully described and carefully compared with those of urinary kreatinins previously investigated (vide 'Roy. Soc. Proc.,' vol. 43, pp. 493-534). The final conclusion drawn is that sarcous kreatine is not present in fresh muscle, but results from bacterial action, whereas sarcous kreatinin is probably a true " educt." II. " Note on Dr. Fenton Evans' Paper on the Pathogenic Fungus of Malaria." By W. T. TniSELTON DYER, M.A., C.M.G., F.R.S. Received May 12, 1891. The abstract of this paper published in this volume of the ' Proceed- ings ' contains (p. 200) the following statement : " Alteration in the chemical composition of the nutrient medium . . . elicited the interesting fact that, under these circumstances, the organism can pass to a more highly developed state, displaying the structure and fructification of a highly organised fungus, but differing in certain important features from any fungus hitherto described." This statement will remain on record, and can hardly fail to cause some perplexity to future students of the aetiology of malaria. 1 was present at the reading of the paper. The fungus exhibited was undoubtedly " highly organised." It was in point of fact a typical Mucor, and my friend Professor Marshall Ward, who was also present, was disposed to regard it as identical with the form known VOL. XLIX. 2 0 540 Mr. F. Galton. [May 28, as Mucor racemosus. The identification was so unmistakable that I utterly fail to understand in what " important features " the fungus differed " from any fungus hitherto described." In the face of the undoubted fact that the fungus was a charac- teristic Mucor, it seems to me very improbable that it has a genetic relationship with any of the organisms found in the blood, and much more likely that its appearance in the nutrient medium was due to some experimental error. III. " Method of indexing Finger- Marks." By FRANCIS GALTON, F.R.S. Received April 30, 1891. Sufficient proof was adduced by me in a memoir read November 27, 1890, before the Royal Society ('Phil. Trans.,' B, 1891), of the extraordinary persistence of the papillary ridges on the inner surface of the hands throughout life. It was shown that the impression in ink upon paper of each finger tip, contained on the average from twenty-five to thirty distinct points of reference, every one of which, with the rarest exception, appeared to be absolutely persistent. Consequently that it was possible to affirm with practical certainty whether or no any two submitted impressions were made by the fingers of the same person. In the present memoir I shall explain the way in which finger prints may be indexed and referred to after the fashion of a dictionary, and on the same general principle as that devised by A. Bertillon •with respect to anthropometric measures, whose ingenious method is now in regular use on a very large scale in the criminal administration of France and elsewhere. I desire to show how vastly the practical efficiency of any such method as that of A. Bertillon admits of being increased by taking finger prints into account in the way about to be described. It must not, however, be supposed that the use of indexing finger marks is limited to the above purpose, the power of doing so being equally needed for racial and hereditary inquiries. I do not dwell upon these applications now, simply because I am engaged in making them, and the results are not yet ready to be published. I ought, however, to mention that a great increase of experience has fully con- firmed my earlier views, that finger marks are singularly appropriate subjects of anthropometric study owing to many distinct reasons. The impressions are easily to be made by anyone who has the proper appliances at hand. They are as durable as any other printed matter, and they occupy very little space. The patterns are usually sharp and clear, and their minutice are independent of age and growth. They are necessarily trustworthy, and no reluctance is shown in per- 1891.] Method of indexing Finger-Marks. 541 mitting them to be taken, which can be founded either upon personal vanity or upon an unwillingness to communicate undesirable family peculiarities. Without caring to dwell on many of my earlier failures to index the finger prints in a satisfactory way, my description shall be con- fined to that which has proved to be a success. It is based on a small variety of conspicuous differences of pattern in each of many digits, and not upon the numerous minute peculiarities of a single digit. My conclusions are principally based on a study of the im- pressions of all ten digits of 289 different persons, but the tables about to be given refer only to the first 100 on my list. These are sufficiently numerous to serve as a fair sample of what we might always expect to find, while they are not too cumbrous to print and to discuss in full detail. I described in my previous memoir the way in which the impres- sions had been made that were then shown. A plate of copper was blackened with printer's ink, the ink being of a rather fluid cha- racter, and spread very thinly and evenly over its surface by a printer's roller. The thumb, which was then the subject of discussion, was pressed and slightly rolled on the inked plate, and afterwards on the paper. In the present collection of all ten digits, four operations were used in each case. First the four fingers of one hand were simultaneously printed from, and then its thumb in the way above described ; afterwards, the other hand was treated in the same way. Though I have spoken and shall speak only of impressions, it is not really necessary for the purpose of compiling an index to make any impression at all. The entries that are wanted for the index can be derived directly from the fingers themselves. I rely, for the purpose of indexing, on the three elementary divi- sions of primaries, whorls, and loops. They are severally expressed by the numerals 1 and 2, 3 and 4, 5 and 6. The reason of this double numeration is that most of the patterns have a definite axis. Those that are formed by ridges which proceed from only one side of the finger, will necessarily lie in a sloping direction across its axis pointing to the one side or the other according to that from which the supply of ridges proceeds. The only patterns that are symmetrically disposed about a vertical axis are 6 and to a lesser degree a, c, h, and i in fig. 1. Usually, and, as we may say, normally, the slope of the axis of the pattern is (roughly) parallel to a line drawn from a tip of the forefinger to the base of the little finger. All normal slopes, as well as all the patterns that have no definite axis, are expressed by the odd numerals 1, 3, or 5. All abnormal slopes are expressed by the even numerals 2, 4, or 6. It cannot be too strongly insisted that the words right and left are ambiguous and should not be used here. 2 o 2 Mr. F. Gallon. Fio. l. [May 28, Index [symmetric. tipped. Priory. , \\-horts. Loop*. /// ///&>/! w// sloped. /^ % ^ \" /* , V/ S o p q r s' t u, r ir The foi-efingers are the most variable of all the digits in respect to their patterns, their slopes being almost as frequently abnormal as not (see Table II) ; the third fingers rank next ; the little finger ranks last, as its pattern is a loop in nine cases out of ten. I, therefore, found it convenient not to index the fingers in their natural order, but in the way that is shown at the head of the column of figures on the left side of fig. 2. There, the sequence of the numerals that express the Fio. 2. R L , R 123, 123 I T4.T4 353,333; 35,35 353,333 35,35 353,353- 15,55 353,653 35,35 415,555 35,55 Left. 355,353 55,35 /? /> 0 @ /7 355,455 55,35 /?/?/?©/? 365,355 55,55 / // ^ . @ & Right. 1891.] Method of indexing Finger-Marks. 543 patterns on the digits, is divided into two groups of three numerals and two groups of two numerals, as 355, 455, 55, 35. The first group 355 refers to the first, second, and third fingers of the left hand ; the second group 455 to the first, second, and third fingers of the right hand ; the third group 55 to the thumb and fourth finger of the left hand ; the fourth group 35 to the thumb and fourth finger of the right hand. The index is arranged in the numerical sequence of these sets of numbers as shown in fig. 2 and in Table I. Before translating the patterns into numerals, I find it an excellent plan to draw symbolic pictures of the several patterns in the order in which they appear in the impression, or in the fingers themselves, as the case may be, confining myself to the limited number of symbols shown in fig. 1, which have fairly well sufficed for my 289 sets or 2890 finger marks, as well as for many others. A little violence has of course to be used now and then, in fitting some unusual pattern to one of these symbols. But we a're familiar with such processes in ordinary spelling, where the same letter does duty for different sounds, as a in the words as, ask, ale, and all. The merits of this process are many. It facilitates a leisurely revision of first determinations ; it affords a pictorial record of the character of each pattern ; it prevents mistakes between normal and abnormal slopes ; it prevents confusion when changing the sequence of the entries from the order of the impressions to that used in the index ; and, lastly, it affords considerable help to a yet further subdivision of the patterns. This may be inferred from the first two lines of fig. 2, which have the same index numbers, but whose pictured forms differ in respect to the two thumbs, and to the middle finger of the left hand. I will now describe the symbols in detail, and show how such small difficulty as arises from rare transitional or border cases is minimised. The primaries in their earliest and purest form are sufficiently, expressed by the symbol a, fig. 1. From this elementary type all other sorts of patterns seem to be lineally descended. A fairly pure form of this type is seen in b ; this is not infrequent in fingers, but I have not once met with it among some thousands of thumbs. A nascent whorl, still so immature as to count as a primary, is sym- bolised by c ; similarly nascent loops, that should undoubtedly bo counted as primaries, by d and e. When, however, the loop form is more pronounced and the pattern has been accepted as a primary only after reasonable hesitation as to whether it was not a loop, a dot is put inside the symbol, as in / and g, to serve as a warning. In this case, supposing another person to reckon the doubtful finger-mark as a loop and to refer and fail to find it under that head, he would make a second reference by treating it as a primary. A dot always means a possibly transitional case ; thus r and s signify that they had been accepted as loops after some hesitation. 544 Mr. F. Galton. [May 28, The whorls include circles, ellipses, and spirals, both simple and compound, whatever may be the direction or closeness of their twist. These are so apt to be confounded together unless the impression is from a rolled finger and is afterwards scrutinised and outlined (as explained in my previous memoir) that it seems best for the present purpose to group them all, with few exceptions, under the one symbol h. The exceptions are these. When two streams of ridges proceed from opposite sides of the finger and interlock, the symbol t is used, regardless of all other details. Again, when the whorl is crozier shaped, as in j and k, it is necessarily enclosed in a loop, but the loop is here ignored. If the crozier approaches very nearly and mistakably to either of the plain eyes t, «, it is dotted for a warning, as in I and m. The loops in their simplest and common forms are shown by n and o. Frequently they have an internal offset which may be variously feathered or bent, short of being a whorl ; all such cases are expressed by p, q. They have sometimes a conspicuous eye due to an internal curvature of the ridges upon themselves, or even to an eye in the central ridge ; these are all expressed by t or it, in which the sur- rounding loop is left out in order to avoid multiplicity of lines. When the eye approaches nearly to a crozier as in Z, m, the dotted symbols r, w are used. In making a large and complete index, the symbols would, of course, be cast as movable types, and be printed with the letterpress. It will be seen from fig. 2 that there is space for 20 entries in one 8vo page. I do not expect from my own reiterated experiences that there would be much trouble due to transitional cases, after a standard collection of doubtful forms had been establised so as to ensure that different persons should abide by a common rule. I find much uniformity in my own judgment. I give an index of 100 cases ; they are the first that occurred in my catalogue of impressions, which are pasted in two rows on each page, and are consequently numbered 1, 1' ; 2, 2', in order; but there are a few blanks, so the numbers in the index happen to run from 1 to 56', with some omissions, and not from 1 to 50'. These cases afford data for roughly measuring the increase in power of discrimination obtained by basing indexes on the patterns of 1, 2, 3, 6, and 10 digits respectively. It appears from Table III that when all 10 digits are used, the number of different patterns observed in the 100 cases was 83 ; therefore the average number of references required to pick out a single well-defined case from among these 100 would be equal to 100 divided by 83, that is, to about 1^. It will also be seen from Table III that, owing to the large effect of correlation, an index based on all the ten digits is not much superior 1891.] Metliod of indexing Finger- Marks. 545 in efficiency to one that is based on only six, namely, upon the first three fingers of both hands. In the 100 different sets there are 83 varieties of pattern in the one case and 65 in the other, which roughly accords with the relative efficiency of 5 to 4. When all the 289 cases are similarly treated, the relative efficiency comes out as 213 to 139, or roughly as 3 to 2. This is a little better but not much. It is, there- fore, a fair question whether it is worth while to impress all the 10 digits. The chief advantage of doing so is to add to the volume of evidence, and to supply data which mutilation, or bad scars, or obliteration due to some exceptional cause might render of value. We also see from Table III that the three fingers of both hands are more than twice as efficient for the purposes of an index as those of one hand only ; again, that three fingers are nearly twice as useful as two. I may mention that for my present inquiries into racial and hereditary patterns I am, for various reasons, dealing only with the three first fingers of the right hand, and slightly rolling the fore- finger, so as to obtain a full impression of its pattern on the side of the thumb. The greatest difficulty in constructing a uniformly efficient cata- logue lies in the troublesome frequency of plain loops, so that even the method of picture writing fails to analyse satisfactorily the numerous 555, 555 ; 55, 55 cases. When searching through a large number of similarly indexed prints for a particular specimen, it is a very expeditious method to fix on any one well-marked characteristic of a minute kind, such as an island, or enclosure, or a couple of adjacent bifurcations, that may present itself in any one of the fingers, and in making the search to use a lens or lenses of low power, fixed at the end of an arm, and to confine the attention solely to looking for that one characteristic. The cards on which the finger marks have been made may then be passed successively under the lens with great rapidity. I fear that the method of counting ridges (as the number of ridges in the AH of my previous memoir) would be difficult to use by persons who were not experts. Anyhow, I have not yet been able to devise a plan for doing so that I can recommend. 54 ti Mr. F. Galton. y 28, Table I. — Numerical Tli roe first fingers. Thumb and fourth finger. Book I. Three firi »> »• 111 i> »• 151 15 61 55 51 15 i) 11 35 51 page 52 20 32 37 46 215 >i 115 255 55 55 55 55 page 48 20' 253 155 55 55 r 255 655 35 35 51 115 i> H II » 113 115 >i 155 55 15 55 15 55 55 15 55 55 55 39 53 4 34' 1 25' 333 " 11 it i • 155 333 353 n ii ii H 433 555 633 55 35 55 55 55 33 35 53 55 33 35 35 M 35 33 33 35 55 33 35 33 33 33 55 35 14 2 31' 2' 36 45 IS ~i 13 4' 14 55' 29 13' 151 151 54 51 33' 154 115 55 55 47 155 ii » » » ii » >» » H >» >i it 113 115 116 155 ii 553 555 ii ii ii 633 655 55 55 35 55 55 55 35 55 55 35 55 55 55 53 35 55 55 35 35 ii 35 35 35 12 20a 6 35' 45' 35 23 507 10 54 56' 44' 335 333 653 53 55 55 55 1* 307 353 ii 333 353 653 35 15 35 35 H 55 35 Stf 197 6' 17 156 553 35 35 7 355 n 353 135 55 :,:, 35 35 16 49 1891.] Method of indexing Finger-Marks. 547 Index of 100 cases. Three first fingers. Thumb and fourth finger. Book I. Three first fingers. Thumb and fourth finger. Book I. Left, 1, 2, 3. Eight, 1, 2, 3. Left, th.,4. Right, th., 4. Left, 1,2, 3. Eight, 1, 2, 3. Left, th., 4. Eight, th., 4. 3C5 355 55 55 page 3' 555 » :> 555 » 55 » 55 » page 19 3 40' 415 555 35 55 21a 4:53 433 35 i 35 10' 32' 565 155 55 35 35 22 •453 355 55 55 633 655 35 5 •455 515 355 455 153 156 55 » 35 55 55 55 35 55 35 11 56 41' 23' 49' 635 653 653 153 653 55 55 35 55 55 33 29' 1' 28' 655 155 335 455 553 555 » 653 655 M 55 55 V 55 35 35 35 55 35 35 55 55 » 35 55 55 55 35 65 55 33 55 35 55 » » S6' 15' 12' 21 «' 53' 20a' 47' 44 52' 26' 21' 25 51' 21 30 553 !> ;> 153 333 353 553 » >j 15 55 55 55 55 15 35 55 35 55 37' 13 22' 27' 16' 24 40 27 23 26 28 39' 15 41 17' 555 » » i> » » » 115 151 153 253 513 553 555 55 55 55 35 55 55 55 » » 55 35 53 35 55 55 55 »j 665 655 55 55 46' .r>ls Mtt hod of indexing Finger- Marks. [May 28, Table II.— Analysis of the 100 Cases in Table I. Forefinger of left hand. Pattern. pattern. I 2 3 4 5 6 H 4 23 6 21 n 100 „ nascent loop, slope normal . . . J „ „ „ slope abnormal . . . with tail, slope normal J tt M slope abnormal Loop, slope normal ,, slope abnormal Table III.— Further Analysis of the 100 Cases in Table I. Set of digits observed. Number of times in First 2 fingers of left hand. First 3 fingers of left hand. First 3 fingers of both hands. All the digits of both hands. which each pattern occurs. Number of Number of Number of A Number of Pat- terns. > Cases. Pat- terns. - Cases. ( Pat- terns. OMW. Pat- terns. •\ Cases. 1 5 5 13 13 49 49 71 71 2 4 8 5 10 6 12 10 20 3 — — 1 3 4 12 1 3 4 1 4 1 4 4 16 — — 5 — — 2 10 1 5 — — 6 1 6 1 6 1 6 1 6 10 1 10 — — — 11 — — — — — — — — 12 — — 1 12 — — — — 13 — — 1 13 — — — — 14 — — 1 14 — — — — 15 — . — 1 15 — — — — 16 2 32 — — — — — — 17 1 17 — — — — — — 18 1 18 — — — — — — Total cases 100 100 .. 100 t f 100 Number of "1 different v 16 . . 27 65 . . 83 patterns J 1891.] Anatomy, $-c., of Protopterus annectens. 549 IV. " On the Anatomy and Physiology of Protopterus annectens" By W. N. PARKER, Ph.D., F.Z.S., Professor of Biology in University College, Cardiff. Communicated by W. H. FLOWER, F.R.S. Received May 4, 1891. (Abstract.) The work which has resulted in the present paper was begun in Freiburg in the summer of 1888, when the author was fortunate enough, owing to the generosity of Professor Wiedersheim, to obtain a number of fresh specimens for examination. As so many interest- ing points presented themselves at an early stage in the research, a short preliminary notice, without illustrations, was published in the following autumn (' Berichte d. Naturforsch. Gesellschaft zu Freiburg i.Br.,' vol. 4, 1888).* This notice merely forms the basis of the present paper, in which the whole subject has been worked out in greater detail. A number of new facts are recorded, some of the author's earlier conclusions modified, and the paper illustrated with 11 plates containing 71 figures. With the exception of certain special details, the structure of the skeleton and of the nervous and muscular systems is not described, the paper consisting mainly of an account of other organs which have not received so much attention from previous observers, and of a comparison of Protopterus with the other genera of Dipnoi, so far as their structure is known, as well as with other Ichthyopsida. The author returns his sincere thanks to the Council of the Royal Society for the grant out of which various expenses connected with the investigation were defrayed, as well as to Professor Wiedersheim, not only for the gift of abundant fresh and preserved material, but also for his continued help and advice during the progress of the work. To Professor Howes the author is indebted for many valuable suggestions. A number of details with regard to the habits of Protopterus in captivity are given, and reference is made to Stuhlmann's observa- tions with regard to its mode of life under natural conditions. The paired extremities, the movements of which are more like those of limbs than of fins, show no connexion with the cheiroptery- gium, and, in spite of their considerable nerve supply, are evidently greatly degenerated structures as regards their free portions. Sensory organs are not present on them, and they therefore cannot have a tactile function. Their distal ends, like the apex of the tail^ are very variable, and can undoubtedly be reproduced when lost by * See also ' Nature,' TO!. 39, p. 19. 550 Prof. W. N. Parker. Chi the Anatomy and [May 28, accident. The tail is almost certainly not primarily diphycercal, and shows signs of a possible origin from a heterocercal form. The epidermis on the whole most nearly resembles that of Perenni- branchiate Amphibians, and gives rise to simple multicellular glands (which are most numerous on the snout), as well as to very numerous closely-packed goblet-cells, which produce the gluey secretion as well as the main substance of the capsule which surrounds the animal during the torpid state. The epidermis forms a regular and continuous layer over the derma, in which the cycloid imbricating scales are imbedded. Pigment cells are present in both layers of the integu- ment, and the derma encloses nests of leucocytes here and there, small cells, apparently migratory leucocytes, being seen in places amongst the ordinary epidermic cells. Integumentary sense organs, similar to those of Fishes and larval Amphibians, are present not only on the head and lateral line, but in various other regions of the trunk also ; they are most numerous on the head. In young animals they are all superficial, and do not project below the general level of the epidermis, and this condition is retained in those situated on the trunk. On the head, the epidermis becomes involuted along certain lines to form grooves, which then become converted into sub-epidermic tubes, in which the sensory organs are situated, and which communicate with the exterior by an aperture at one end. The relations of the sensory organs of the trunk are therefore similar to those seen in young stages of Fishes and in Amphibian larvae, while in the case of the head, they resemble those which are typical for adult Fishes. End-buds, similar in structure to the taste-bads of Fishes and Amphibians, are present on the tongue and oral epithelium, but are absent on the lips, and, as in Amphibians, do not occur on the surface of the body. As regards its general structure, the olfactory organ most nearly resembles that of Elasmobranchs, but the presence of posterior nostrils raises it to a higher level. The position of the anterior nostrils beneath the upper lip is probably to be accounted for as an adapta- tion in connexion with the torpid state (vide infra). The space between the eyeball and its muscles and the orbit is filled with a delicate connective tissue; there are no orbital glands or eyelids. Four straight and two oblique muscles are present. The cornea is continuous with the derma on the one hand, and the sclerotic on the other ; the latter is fibrous in young animals, and islands of cartilage first appear at the points of insertion of eye-muscles, and then gradually extend so as to chondrify the whole sclerotic. The eye resembles that of Amphibians ; a processus falciformis and campa- nula Halleri are absent, and no ciliary muscles were observed, though possibly present ; almost all the pigment of the eye is ectodermic. No specialised glands are present in connexion with the greatly 1891.] Physiology of Protoptems annectens. 551 folded epithelium of the oral cavity. The lips contain no muscles. The tongue, as well as the palate, is covered with blunt conical papillae, on which the taste-buds are situated. Beneath the epi- thelium the tongue is composed anteriorly to the hyoid of a simple connective tissue, while posteriorly to the hyoid it is made up of extrinsic muscles, the main mass of which is continuous with the ventral musculature of the trunk. A horny cap is developed over each tooth from the overlying epithelium, which apparently becomes cut through by the sharp edges and points of the teeth, and which probably corresponds to the cuticula deniis. The thyroid is a small bilobed organ imbedded in the tongue just above the hyoid symphysis, and has the characteristic structure. The thymus consists of lymphoid tissue, and is situated dorsally and posterior to the branchial arches, surrounding the blood-vessels of the external gills. The alimentary canal extends almost in a straight line from the mouth to the vent. A ventral, as well as a fenestrated dorsal, mesentery is present supporting the intestine. The so-called urinary bladder (" cloacal caecum ") opens into the cloaca dorsally to the intestine ; the author compares it with the " processus digitiformis " of Elasmobranchs. A spleen and pancreas are present, imbedded in the thin walls of the stomach, and extending on to the proximal part of the intestine ; they are covered externally by sparse muscular fibres as well as by the peritoneum. The relations of the pancreas therefore most nearly resemble those met with in Ganoids and certain Teleosteans. The pancreas is deeply pigmented, and its ducts open into the bile-duct. The pigmented walls of the intestine and the spiral valve are very thick, owing to the abundance of lymphoid tissue contained within them. With the exception of the bursa entiana, the internal walls of which are raised up into a number of deeply pigmented oblique folds, the whole of the mucous membrane of the stomach and intestine is perfectly smooth, and there is no indication of any differentiated gastric or intestinal glands. Cilia are present on the epithelium throughout the stomach and intestine. The epithelium is columnar and stratified, and branched pigment cells extend into it in the greater part of the intestine. Small leucocytes can be recognised among the epithelial cells here and there. A layer of small-celled lymphoid tissue directly under- lies the epithelium. In the spleen and lymphoid organs of the intestine two kinds of tissue are present: (1) a large-celled tissue, which forms the greater part of these organs, and which somewhat resembles embryonic connective tissue ; and (2) a smaller-celled tissue, similar to that lying directly beneath the epithelium, and resembling that of ordinary lymphoid follicles. Large migratory cells are present in both kinds of tissue, many of which enclose 552 Prof. W. X. Parker. On tJie Anatomy and [May 28, yellowish granules. Gradations between these and rounded cells of a deeper yellow or brown colour can apparently be made out; the latter arc arranged in larger or smaller groups, and cells appearing to be intermediate forms between these and the ordinary black branched pigment cells can also be seen. The lymphoid tissue is penetrated by networks of blood-vessels, and it seems probable that the yellow grannies mentioned above are due to the disintegration of red corpuscles, which are ingested by leucocytes, and then undergo some change, whereby the latter gradually pass into the condition of black pigment cells, which migrate through the epithelium, and are so got rid of. The muscular layers are very thin. A muscularis mucosee is present, and the circular and longitudinal layers are represented, but the direction of the fibres is in many regions difficult to trace. Strands, only a few cells in thickness, extend throughout the lymphoid tissue of the intestine, and some of these unite to form a longitudinal band passing down the axis of the spiral valve. An analysis of the contents of the gut, for which the author is indebted to Professor Baumann, while yielding negative results as regards the stomach, proves the presence of peptones, in small quantities, in the intestine. The question as to the mode of digestion and absorption of the food in Protopterus is discussed. The branchial apparatus shows signs of considerable reduction. Internal gills are present on the posterior face of the hyoid, on both faces of the third and fourth branchial arches, and on the anterior face of the fifth. Three pairs of external gills were present in all specimens, even the largest, examined. The pulmonary apparatus, on the whole, more nearly resembles the air-bladder and its duct of certain Ganoids than the lungs and laryngo-tracheal chamber of Amphibians. The pulmonary branches of the vagus cross one another at the base of the lungs. The blood is remarkable for the large size of its elements, which is only exceeded in the case of Proteus and Siren, as well as for the large proportion of white corpuscles in comparison with the red ones. Two forms of the former are described, in one of which fine radiating pseudopodia can be protruded, and different stages in the degenera- tion of the nucleus and cell-body could be observed. The chief points of interest with regard to the blood-vessels are as follows : — (1) the presence of a paired pulmonary artery, the left supplying the ventral, and the right the dorsal, aspect of the lungs ; (2) the presence of a single true post-caval, along with a persistent left posterior cardinal vein ; and (3) the single caudal vein, giving rise to a right and a left renal portal. No external sexual differences could be observed, and amongst the specimens examined, females were the more abundant. The urino- genital organs are surrounded by masses of tissue resembling the 1891.] Physiology of Protopterus annectens. 553 large-celled lymphoid tissue of the gut, but differing from the latter in becoming largely converted into adipose tissue. The kidneys probably represent the mesonephros, and their duct the Wolffian duct ; nephrostomes are absent. In unripe males, delicate Miillerian ducts are present. The sperm is conducted to the exterior by a duct, which is probably formed in connexion with the testis, quite independently of the excretory ap- paratus. The seminal tubules are directly connected with it, and it opens into the base of the Miillerian duct, the rest of which ap- parently aborts completely. Unlike most of the tissue elements, which are very large, and closely resemble those of the Amphibia, the spermatozoa are very minute, and are remarkable in possessing two vibratile flagella attached to the carrot-shaped " head." The genera- tive organs of the female bear a striking resemblance to those of Amphibians. The oviduct corresponds to the Miillerian duct ; the epithelium covering its internal folds shows signs of degeneration similar to those which have recently been described amongst TJrodeles. No traces of a sympathetic were found. An account of the mode of life of Protopterus during the torpid period is given. The coccoon is provided with a " lid," perforated by a hollow funnel-shaped tube, which passes between the lips of the animal, and thus forms a passage for the respiratory current. The source of nutrimeat during the summer sleep lies in the adipose tissue in connexion with the gonads and kidneys and alongside the notochord in the tail, as well as in the lateral muscles, some of which, especially in the caudal region, undergo a granular degeneration. Very probably the latter is the precursor of the fatty degeneration, and, in all probability, leucocytes are the active transporting agents of the degenerated material. This assumption would help to -explain the large development of lymphoid tissue in the body of the animal. An analysis of^the muscles, by Professor Baumann, shows that they do not retain quantities of the products of nitrogenous waste, as is the case in Elasmobranchs. The systematic position of the Dipnoi is briefly discussed in the light of the new facts brought forward in the present paper. Although the Dipnoi present many points of resemblance to Fishes on the one hand, and to the lower Amphibians on the other, their connexion with any living forms of either class is probably a very distant one, and it is inadvisable) to classify them amongst the Fishes. Owing to the absence of ontological evidence, and to the incompleteness of our knowledge of the palaeontological history of the Dipnoi, it is impossible to construct a genealogical tree which will show, with any approach to accuracy, 'the probable connexion between them and other ">."> 1 Presents. [May 28r Ichthyopsidan types. The most that can be said at present, with any- thing like certainty, is that the Dipnoi are the isolated survivors of an exceedingly ancient group, which was probably related to the ancestors of existing Fishes and Amphibians. Amongst the former, the connexion seems to be closest to the Elasmobranchs, more par- ticularly to the Chimseroids on the one hand, and to such an ancient Selachian type as Chlamydoselache on the other; but at the same time, the Ganoids probably arose from the common ancestral stock not very far off. Though retaining many primitive characters, the Dipnoi, and more especially Protopterus and Lepidosiren, are in some respects highly specialised, the specialisation being largely due to a change of habit. V. " On the Constitution of the Terpenes, Camphors, and Camphor Acids." By J. NORMAN COLLIE, M.D. Communi- cated by Professor RAMSAY, F.R.S. Received April 29, 1891. [Publication deferred.] Presents, May 28, 1891. Transactions. Acireale : — Societa Italiana dei Microscopisti. Bollettino. Vol. I. Fasc. 4. 8vo. Acireale 1891. The Society. Baltimore : — Johns Hopkins University. Studies in Historical and Political Science. Nos. 5-6. 8vo. Baltimore 1891 ; Annual Report, 1890. 8vo. Baltimore. With Twelve Dis- sertations and Excerpts. 8vo. The University. Berlin :— Gesellschaft fur Erdkunde. Zeitschrift. Bd. XXVI. No. 2. 8vo. Berlin 1891. The Society. Bnda - Pest : — K. Ungarische Geologische Anstalt. Foldtani Kozlony. Kotet XXI. Fiizet 1-3. 8vo. Budapest 1891 ; Jahresbericht fur 1889. 8vo. Budapest 1891 ; Mittheilungen. Bd. IX. Heft 3-5. 8vo. Budapest 1891. The Institute. Calcutta : — Asiatic Society of Bengal. Proceedings. No. 1. 8vo. Calcutta 1891 ; Annual Address to the Asiatic Society of Bengal. 8vo. Calcutta 1891. The Society. Cambridge, Mass. : — Museum of Comparative Zoology, Harvard College. Bulletin. Vol. XXI. No. 1. 8vo. Cambridge 1891. The Museum, Chapel Hill, N.C. : — Elisha Mitchell Scientific Society. Journal. Vol. VII. Part 2. 8vo. Raleigh 1891. The Society. 1891.] Presents. 555 Transactions (continued). Cracow : — Academic des Sciences. Bulletin International. Comptes Rendus des Seances. Avril 1891. The Academy. Edinburgh : — Royal Society. Transactions. Vol. XXXIV, XXXVI. Part 1. 4to. Edinburgh 1890-91. The Society. Florence : — R. Istituto di Studi Superiori Pratici e di Perfeziona- mento. Pubblicazioni (Medicina e Chirurgia). Vols. 3-4. 8vo. Firenze 1885-86; Pnbblicazioni (Filosofia e Filologia). Vol.11. No. 21. 8vo. Firenze 1888 ; Pubblicazioni (Scienze Fisiche e Naturali). Nos. 12-14. 8vo. Firenze 1884-88. The Institute. Frankfort-on-Main : — Senckenbergische Naturforschende Gesell- schaft. Abhandlnngen. Bd. XVI. 4to. Frankfurt 1890. The Society. Frankfort-on-Oder : — Naturwissenschaftlicher Verein. Monatliche Mittheilungen aus dem Gesammtgebiete der Naturwissen- schaften. Jahrg. VIII. Nr. 4-11. 8vo. Frankfurt 1890-91. The Society. Gottingen : — Konigl. Gesellschaft der Wissenschaften. Abhand- lungen. Bd. ^XXXVI. 4to. Gottingen 1890 ; Nachrichten. 1890. 8vo. Gottingen. The Society. Leipsic : — Astronomische Gesellschaft. Vierteljahrsschrift. Jahrg. 25. Heft 4. 8vo. Leipzig 1890. The Society. London : — City and Guilds of London Institute. Report to the Governors. 1891. 8vo. [LondonJ] The Institute. East India Association. Journal. Vol. XXIII. No. 1. 8vo. London 1891. The Association. Institute of Brewing. Transactions. Vol. IV. No. 6. 8vo. London 1891. The Institute. Institute of Chemistry of Great Britain and Ireland. Register, 1891 . 8vo. London. The Institute. Royal Horticultural Society. Journal. Vol. XIII. Part 1. 8vo. London 1891. The Society. Victoria Institute. Journal of the Transactions. Vol. XXIV. No. 95. 8vo. London [1891]. The Institute. Zoological Society. Report. 1890. 8vo. London 1891. The Society. Manchester: — Manchester Museum, Owens College. Report. 1889-90. 8vo. Manchester [1891]. The Museum. Meriden : — Scientific Association Proceedings and Transactions. Vol. IV. 8vo. Meriden 1891. The Association. Munich : — K. B. Akademie der Wissenschaften. Abhandlungen (Math.-Phys. Classe). Bd. XVII. Abth. 2. 4to. Munchen 1891; Abhandlungen (Philos.-Philol. Classe). Bd. XIX. Abth. 1. 4to. Hiinchen 1891. The Academy. VOL. XLIX. 2 P 55ti Presents. [May 28, Transactions (continued). Nt w York : — American Museum of Natural History. Bulletin. Vol. III. Pp. 195-210. 8vo. [New York] 1891. The Museum. Orthopaedic Dispensary and Hospital. Report. 1890. 8vo. [New York] 1891. The Trustees. Paris : — Societe Mathematique de France. Bulletin. Tome XIX. No. 1. 8vo. Paris 1891. The Society. Penzance : — Royal Geological Society of Cornwall. Transactions. Vol. XI. Part 5. 8vo. Penzance 1891. The Society. Philadelphia : — American Philosophical Society. Proceedings. Vol. XXVIII. No. 134. 8vo. Philadelphia 1890. The Society. Rome : — Reale Accademia dei Lincei. Atti. Ser. 4. (Scienze Morali, Storiche e Filologiche). Vol. IV. Parte 1. Vol. VI. Parte 2. 4to. Roma 1888-89. The Academy. Stockholm: — Kongl. Vetenskaps-Akademie. Ofversigt. Arg. 48. No. 2. 8vo. Stockholm 1891. The Academy. Sydney : — Australasian Association for the Advancement of Sci- ence. Report. Melbourne Meeting. 1890. 8vo. Sydney [1891]. The Association. Turin : — Reale Accademia delle Scieuze. Atti. Vol. XXVI. Disp. 4-5. 8vo. Torino 1890-91. The Academy. Vienna: — K.K. Geologische Reichsanstalt. Verhandlungen. 1891. Nos. 5-7. 8vo. Wien. The Institute. Washington : — Smithsonian Institution. Miscellaneous Collec- tions. Vol. XXXIV. Articles 1-3. 8vo. Washington 1890. The Institution. U.S. National Museum! Proceedings. Nos. 834-35, 837, 839. 8vo. Washington 1891. The Museum. Wiirzburg : — Physikalisch-Medicinische Gesellschaft. Verhand- lungen. Bd. XXIV. No. 7. Bd. XXV. Nr. 1-2. 8vo. Wiirzburg 1891 ; Sitznngsberichte. 1891. No. 1. 8vo. Wiirzburg. The Society. Observations and Reports. Buda-Pest : — Konigl. Ungar. Central- Anatalt fur Meteorologie und Erdmagnetismus. Jahrbucher. Bd. XVIII. 4to. Budapest 1890. The Institute. Cambridge, Mass. : — Harvard College Observatory. Annals. Vol. XXIII. Parti. Vol. XXVII. 4to. Cambridge 1890; Variable Stars of Long Period. 4to. Cambridge 1891. The Observatory. Christiania : — Norwegisches Meteorologisches Institut Jahrbuch fur 1888, Folio. Christiania 1890. The Institute. 1891.] Presents. 557 Observations, &c. (continued), Edinburgh: — Royal Observatory. Circular, No. 15. 4to. [Sheet] 1891. The Observatory. Hongkong : — Observatory. Observations. 1889. Folio. Hong- kong 1891. The Observatory. Kiel :— Sternwarte. Publication. No. 6. 4to. Kiel 1891. The Observatory. Mexico : — Informes y Documentos relativos a Comercio Interior y Exterior Agricultura e Industrias. Num. 68. 8vo. Mexico ]891. Observatoire Meteorologique Central, Mexico. Missouri : — Geological Survey. Bulletin. Nos. 2-3. 8vo. Jeffer- son City 1890. The Survey. Munich : — K. Sternwarte. Neue Annalen. Bd. I. 4to. Miinchen 1890. The Observatory. Portugal : — Commission des Travaux Geologiques. Description de la Faune Jurassique. Embranchement des Echinodermes. Fasc. 2. 4to. Lislonne 1890. The Survey. Sydney : — Observatory. Meteorological Observations. November, 1890. The Observatory. Toronto : — Meteorological Service of the Dominion of Canada. Report. 1887. 8vo. Ottawa 1890. The Service. Journals. Archiv for Mathematik og Naturvidenskab. Bd. XIII. Hefte 2-4. Bd. XIV. Hefte 1-2. 8vo. Christiana 1890. The University, Christiania. Archives Neerlandaises des Sciences Exactes et Naturelles. Tome XXV. Livr. 1. 8vo. Harlem 1891. Societe Hollandaise des Sciences, Harlem. Boletin de Minas Industria y Construcciones. Ano VI. Num. 12. Ano VII. Num. 1-2. 4to. Lima 1891. La Escuela Especial de Ingenieros, Lima. Canadian Record of Science. Vol. IV. No. 5. 8vo. Montreal 1891. Natural History Society, Montreal. Galilee (Le) Nos. 8-9. 8vo. Paris 1891. The Editor. Medico-Legal Journal (The) Vol. VIII. No. 3. 8vo. New York 1890. Medico-Legal Society, New York. Monitore Zoologico Italiano. Anno 2. Nos. 1-3. 8vo. Firenze 1891. The Editors. Naturalist (The) No. 190. 8vo. London 1891. The Editors. Nyt Magaziu for Naturvidenskaberne. Bd. XXXI. Hefte 4. 8vo. Christiania 1890. The Editors. Revista Argentina de Historia Natural. Tomo I. Eutrega 2. 8vo. Buenos Aires 1891. The Editor 558 Presents. Journals (continued). Revista do Observatorio. 1891. No. 3. 8vo. Rio de Janeiro. Observatory, Rio de Janeiro. Revue de 1'Evoluiion Sociale, Scientifique et Litteraire. Nos. 6-7. 4to. The Editor. Revue Medico-Pharmaceutique. 1891. No. 4. 4to. Constanti- nople: The Editor. Societatum Litterae. 1890. Nos. 7-9. 1891. No. 1. 8vo. Frankfurt a.O. Natnrwissenschaftlicher Verein, Frankfort. Stazioni Sperimentali Agrarie Italiane (Le) Vol. XX. Fasc. 3. 8vo. Asti 1891. R. Stazione Enologica, Asti. Cauchy (A.) (Euvres Completes. Ser. 2. Tome IX. 4to. Pam. 1891. Academic des Sciences, Paris. Harcourt (L. F. Vernon) Achievements in Engineering. 8vo. London 1891. The Author. Jones (T. R.), F.R.S. On the Utility of an Elementary Knowledge of Geology to the Officers of the Army and Navy. 8vo. London 1891. The Author. Jones (T. R.), F.R.S., and J. W. Kirkby. On the Ostracoda found in the Shales of the Tipper Coal-Measures at Slade Lane, near Manchester. 8vo. [Manchester 1891.] The Authors. Lansdell (Rev. H.) Through Siberia. Second Edition. 8vo. London 1882 ; Russian Central Asia. 8vo. London 1885 ; Through Central Asia. 8vo. London 1887. The Author. Le Chatelier (H.) and G. Mouret. Les Equilibres Chimiqnes. 8vo. Paris 1891. The Authors. Miller (W. D.) The Micro-Organisms of the Human Mouth. 8vo. Philadelphia 1890. The Author. Mueller (F. von), F.R.S. Iconography of Australian Salsolaceous Plants. Decades 1-6. 4to. Melbourne 1889-90. The Government of Victoria. Schubeler (F. C.) Norges Vaextrige. Bd. III. 4to. Chrittiania 1889. The University, Christiania. Sharp (W.), F.R.S. Essays. No. 59. 8vo. London 1891. The Author. Smith (J. B.) A Treatise upon Wire, its Manufacture and Uses. 4to. London 1891. The Author. Sprengel (H.), F.R.S. A Contribution to the History of the Electric Incandescent Vacuum- Lamp. 8vo. London 1891. The Author. Wood-Mason (J.) and A. Alcock. Natural History Notes. No. 21. 8vo. London 1891. The Authors. OBITUARY NOTICES OF FELLOWS DECEASED. In ALEXANDER JOHN ELLIS the Society have lost an earnest and useful worker in several important branches of knowledge. He was a learned mathematician, an accomplished scholar, an original thinker, an indefatigable investigator, and an industrious writer; and his contributions to some of the more obscure and unfamiliar subjects of scientific study have been numerous, varied, and remark- able. He was born at Hoxton in 1814, and his original name was Sharpe, having been changed to Ellis in 1825. It is believed that this was done in consequence of a bequest, made by a relative, to enable him to devote his life to study and research, unhampered by pecuniary cares ; and if this was so, he certainly carried out most faithfully his part of the bargain. He was placed first at Shrewsbury School, and then at Eton, after which he went to Cambridge, being elected a Scholar of Trinity College in 1835. Here he worked with zeal, bearing his specified career in mind, and in 1837 he came out Sixth Wrangler and First of the Second Class in Classics. He entered the Middle Temple as a student, and remained a member ; but he appears to have had no serious intention of following the legal profession, and he was never called to the Bar. The work of Mr. Ellis's life, as exhibited in his multifarious and voluminous writings, has been so extensive that it is impossible here to do it full justice. It must suffice to indicate some of the principal subjects to which his attention was given. He first made himself known as a writer on Mathematics, having published, in 1843, a translation of Professor Martin Ohm's " Geist der Mathematischen Analysis." He afterwards continued to write, from time to time, papers on mathematical subjects, mostly published in the ' Proceedings of the Royal Society.' Many of these were of a somewhat abstruse character, as " On the Laws of Operation and the Systemization of Mathematics," 1859 ; " On Scalar and Clinant Algebraical Coordinate Geometry," 1860, 1861, and 1863; "On Stigmatics," 1865 and 1866: while others were more practical, such as " Problems in Hypsometry," 1865, and " On the calculation of Logarithms," 1881. He also published, in 1874, a separate work con- sisting of five consecutive essays, and entitled " Algebra identified with Geometry." VOL. XLIX. 6 The chief subject, however, of Mr. Ellis's labours was a branch of philology which he called " Phonetics," or the science of pronuncia- tion. A few years after leaving Cambridge, he associated himself with Mr. Isaac Pitman in arranging a system of printing called phonotypy, which, by the aid of several new letters added to the Roman alphabet, gave the means of accurately representing the various sounds used in spoken language. In 1844, he published a description of this in a little work called " Phonetics ; a familiar System of the Principles of that Science " ; and this was followed by several other works, pointing out the disadvantages of the ordinary orthography, and advocating a general adoption of phonetic spelling. For many years ho laboured industriously, and at considerable cost, to further this " Spelling Reform," and, as a means of exhibiting his views more completely, he undertook the transformation, into the new ortho- graphy, of many well known and standard works, such as the New Testament, the ' Pilgrim's Progress,' some of Shakespeare's plays. ' Paradise Lost,' ' Rasselas,' and so on. He also brought out on the same plan a monthly magazine called the ' Phonetic Journal,' and after- wards a weekly newspaper entitled the ' Phonetic News.' The latter 6rst appeared on the 6th January, 1849, and it ran for three months, attracting much public attention from the strangeness of its typo- graphy, and the boldness of the aim embodied in its design. The object aimed at was, however, far too gigantic to have a chance of success, and Mr. Ellis afterwards contented himself with using his system as a means of enabling him to describe and discuss pro- nunciation with greater accuracy of detail than previously, par- ticularly as exemplified in the varieties of existing dialects. With this view, he modified it considerably in order to simplify the print- ing arrangements. In 1886, he produced what he called " Paloeotype, or the Representation of Spoken Sounds by Ancient Types " ; and in 1870, he laid before the Society of Arts an elaborate paper with a more popular educational aim, " On a Practical Method of Meeting the Spelling Difficulty in School and in Life." In this he proposed, not. as before, to abolish the ordinary spelling, but to use concurrently with it a phonetic orthography formed only of ordinary types, which he called " Glossic " ; the objects were, as he put it : — Too fasilitait lerning too reed. Too maik lerning too spel unneseseri. Too ashnilait reeding and reiting too hearing and specking. Too make dhi riseevd proanuneiaishen or Ingglish aksesibl too aul reeden, proavinahel and foren. Mr. Ellis was not long in finding a worthy nse for the phonetic instrument which he had thus elaborated. In the course of his work upon it, he had occasion to look into the history of Englis Ill pronunciation, and he was so fascinated by the novelty and extent of the subject that he determined to devote himself to its study ; and it occupied him, more or less, all the remainder of his life. It resulted in a great work, of which the First Part appeared in 1869. It was entitled : ' On Early English Pronunciation, with special reference to Shakespeare and Chaucer, containing an Investigation of the Corre- spondence of Writing with Speech in England, from the Anglo-Saxon Period to the existing Received and Dialectal Forms,' &c., &c. This part was, in a few years, followed by three others, but Part V required so much labour, that it was only finished in 1889. The whole work contains about 2500 pages, and was published jointly by the Philological, the Chaucer, and the Early English Text Societies. The Public Orator at Cambridge, speaking of it in 1890, said, very appropriately : — " It may be confidently predicted that the day will come when all the varieties of our dialects, like the ancient languages of the Arcadians and the Cyprians, will have entirely faded out of human cognizance ; and then most certainly there will daily accrue increas- ing honour to the works which this author has elaborated with such infinite labour." Mr. Ellis was President of the Philological Society from 1872 to 1874, and from 1880 to 1882, and he wrote many other works and papers on this and other kindred matters. Another subject in which Mr. Ellis took great interest was the scientific theory of music. During his phonetic investigations, he had wished to obtain an accurate physical explanation of the produc- tion of vowel sounds, and, on the suggestion of Professor Max Miiller, he referred for this to the work published in 1863 by Professor Helmholtz, " Die Lehre von den Tonempfindungen.'' In this, he found much more than he had sought for. He had studied music under Professor Donaldson, of Edinburgh (a physicist as well as a musician), and had acquired a desire to investigate for himself the physical basis of the musical art. He had found but poor satisfac- tion in the existing theoretical works, but the novel expositions of Helmholtz solved all his difficulties. The first results of his study were three papers presented to the Royal Society in 1864, " On the Conditions, Extent, and Realization of a Perfect Musical Scale on Instruments with Fixed Tones," "On the Physical Constitution and Relations of Musical Chords," and " On the Temperament of Musical Instruments with Fixed Tones." But he had so high an opinion of the importance of Helmholtz's work that he undertook the laborious task of translating it into English, and the translation was published in 1875, under the title of " The Sensations of Tone as a Physiological Basis for the Theory of Music." IV Of Mr. Ellis, however, it may be said that nihil tetiijit quod nan ornavit, and, not content with translating excellently the 640 closely printed pages of the original, he ornamented it with a mass of elaborate theoretical matter of his own, amounting, in notes and appendices, to about 60 per cent. more. A second edition was published in 1885, to which large farther additions were made. He wrote other essays on musical subjects, among which were two important ones on the much-debated subject of musical pitch, read before the Society of Arts in 1877 and 1880, and rewarded by silver medals. The last paper he presented to the Royal Society, the end of 1884, was a joint one by himself and Mr. A. J. Hipkins, " On the Musical Scales of Various Nations," and this was followed, in March, 1 885, by a larger one on the same topic at the Society of Arts. He farther endeavoured to make his phonetic knowledge practically useful to the musical art by an excellent little work on Pronunciation for Singers. Mr. Ellis was elected into the Royal Society on the 2nd June, 1864. He had previously made several communications to the Society, and he was afterwards a frequent contributor to its Proceed- ings. He served on the Council from 1880 to 1882. He was elected a Fellow of the Society of Antiquaries in 1870, and in June, 1890. he was presented by the University of Cambridge with the honorary degree of Doctor of Letters. It must be added that Mr. Ellis was highly esteemed by all who knew him or had transactions with him, for his amiability of character and his zealous, sincere, and unselfish devotion to the spread of knowledge. But few men have possessed his depth of acquirements, or his power of application, and still fewer have used them so well. About six years ago, he issued a circular to his friends, intimating that the few years of his life he could reckon on would be fully occupied by the completion of his great work, and requesting them to disturb him as little as possible till it was done. The concluding volume appeared, as has been said, in 1889 ; and he immediately afterwards wrote an abridgement of it, which was published sepa- rately in 1890. He had had, however, a severe shock in the death of his wife; his health began to give way, and he died on the 28th of October, 1890. W. P. Professor JOHN MARSHALL, F.R.C.S., died on the morning of the 1st of January, 1891, at his residence, "Bellevue," Cheyne Walk, Chelsea, to which he had removed in the preceding summer from the house in Savile Row where he had spent the greater part of his professional life. He had for some years been in failing health, suffering from winter cough and occasional attacks of gout. These conditions doubtless predisposed him to the acute attack of bronchitis which proved fatal after an illness of a few days' duration. Professor Marshall was in his 73rd year at the time of his death, having been born on the tlth September, 1818, at Ely, where his father practised as a solicitor. After having received his education at a private school, John Marshall was apprenticed to a surgeon at Wisbeach, and in 1839 began his medical studies at University Col- lege and Hospital, then the largest and most popular school in England. Here he speedily attracted the favourable notice of his teachers — more particularly of Mr. Quain and of Dr. Sharpey. His acquaintance with Dr. Sharpey speedily ripened into a close intimacy and a warm friendship which continued unbroken till his death. Mr. Marshall became a member of the Royal College of Surgeons in 1844. He' now established, himself as a practitioner in Camden Town, was appointed. Assistant Demonstrator of Anatomy in University College, and subsequently made Curator of the Ana- tomical Museum. In 1848 he was appointed Assistant-Surgeon to the hospital, and in 1849 became a Fellow of the Royal College of Surgeons. For many years he taught practical and operative surgery at University College ; but it was not until 1866 that he was ap- pointed full Surgeon with charge of in-patients to the hospital. This important step was gained on Mr. Quain's retirement from the hospital, and in the same year, on Mr. Erichsen being transferred from the post of Professor of Surgery in the college to that of Holme Professor of Clinical Surgery in the hospital, Mr. Marshall succeeded him in the college professorship. Mr. Marshall held this appointment till 1885, when failing health and the pressure of other work compelled him to resign his office, both in the college and hos- pital. In recognition of his lengthened and distinguished services in these institutions, he was appointed Emeritus Professor of Surgery in the college, and Consulting Surgeon to the hospital. Onerous and important as were his duties in University College and Hospital, these institutions were by no means the only scenes of Mr. Marshall's professional activity. For four years he was the Fullerian Professor of Physiology at the Royal Institution. He was early in life appointed Lecturer on Anatomy as applied to Art, first at Marlborough House, and then at the Government School of Art at South Kensington ; and on the death of Mr. Partridge he was ap- pointed to the honourable post of Professor of Anatomy at the Royal Academy. In 1873 he was elected a member of the Council of the Royal College of Surgeons, and in 1883 he became the President of that college. He was elected President of the Royal Medical and Chirurgical Society in 1883, and in 1887 became President of the General Medical Council — an office that he held at the time of his VI death. Daring the latter years of bis life Mr. Marshall took an active interest in the establishment of a teaching university for London, and was chairman of the association established for the promotion of that object. Mr. Marshall was strongly in favour of the establishment of a new teaching university for the metropolis, and of leaving the present University of London to discharge its duties as an Imperial examining body untrammelled by teaching functions. Mr. Marshall was elected a Fellow of this Society in 1857. He twice served on its Council, viz., from 1868 to 1870, and again in 1880-81. He has contributed two papers to the ' Philosophical Transactions.' The first of these (1849), published in 1850 (' Phil. Trans.,' pp. 135 — 170), was " On the Development of the Great An- terior Veins in Man and Mammalia, including an account of certain Remnants of Foetal Structure found in the Adult ; a Comparative View of these Great Veins in different Mammalia, and an Analysis of their occasional Peculiarities in the Human Subject." This paper, which was the result of a laborious original research, formed a very important addition to embryology and to our knowledge of the morphology of the vascular system. The second paper, published in 1861 (' Phil. Trans.,' pp. 505—538), was " On the Brain of a Bush- woman, and on the Brains of two Idiots of European Descent." This paper was a most valuable contribution to our knowledge of the anatomy of the idiot brain. In it Marshall mapped out the con- volutions, and in some measure may be said to have been a pioneer in that field of research which has yielded such important results to Ferrier, Horsley, and others of recent years. The bent of Professor Marshall's mind was essentially and strongly scientific. Throughout his life he devoted much time, and paid close attention, to the study and the teaching of anatomy and physiology. As has already been stated, he was for a lengthened series of years Lecturer on Art Anatomy at the Government Schools of Art at Marlborough House and South Kensington ; up to the time of his death he held the Professorship of Anatomy at the Royal Academy of Arts ; and for four years he had been Fullerian Professor of Physio- logy at the Royal Institution. As a lecturer he was clear and precise ; his hearers felt that he possessed a thorough mastery over the subject on which he discoursed, and the enthusiasm with which he treated his favourite studies could never fail to elicit a warm and sympathetic response in his class. Marshall's published works were chiefly on anatomy and physio- logy- " The Human Body : its Structure and Functions " appeared in 1860, "Outlines of Physiology" in 1867, and "Anatomy for Artists " in 1878. On surgery he wrote but little. His most im- portant contributions to it were a paper in the ' Medico-Chirurgical Vll Transactions' for 1851, on "The Employment of Electricity in Surgery," and the Bradshaw Lecture delivered at the Royal College of Surgeons in 1883, on " Nerve-stretching," and the Morton Lec- ture, on " Cancer." Mr. Marshall took much interest in hospital construction, and strongly favoured the " circular- ward " system. Whatever may be the merits or demerits of that system — and on this point there is much discrepancy of opinion, Marshall had the satisfaction of seeing it introduced, mainly through his advocacy, into several hospitals in this country. Few members of the medical profession can show so full a record of public and official work as conld Professor Marshall, and by none has such work been done more thoroughly and more faith- fully than by him. Yet he has been allowed to pass away with services such as these unrecognised and himself unrewarded by any public mark of dignity or of distinction. J. E. E. Vll Transactions ' for 1851, on " The Employment of Electricity in Surgery," and the Bradshaw Lecture delivered at the Royal College of Surgeons in 1883, on " Nerve-stretching," and the Morton Lec- ture, on " Cancer." Mr. Marshall took much interest in hospital construction, and strongly favoured the " circular- ward " system. Whatever may be the merits or demerits of that system — and on this point there is much discrepancy of opinion, Marshall had the satisfaction of seeing it introduced, mainly through his advocacy, into several hospitals in this country. Few members of the medical profession can show so full a record of public and official work as could Professor Marshall, and by none has such work been done more thoroughly and more faith- fully than by him. Yet he has been allowed to pass away with services such as these unrecognised and himself unrewarded by any public mark of dignity or of distinction. J. E. E. Holland has produced more, perhaps, than its share of men whose names are likely to be held in lasting honour by mankind, and among them hardly one greater or nobler as a hero of science than FRANS CORNELIS BONDERS.* In him rare gifts of nature were so happily blended, and turned to such good account for the advantage of his fellow men, as to make him an illustrious example of how much may be accomplished for our race in those quiet paths of life in which he was well content to pass his days. He was, indeed, doubly fortunate, for, while he bore a conspicuous part in the extension of knowledge and its beneficent applications, in fields which he found already ripening for the discoveries with which his fame will be ever associated, he lived long enough to see the rich results of his labours universally and gratefully acknowledged by his contemporaries. He was born the 27th May, 1818, at Tilburg, a manufacturing town of North Brabant, in the Kingdom of the Netherlands, in a com- munity almost exclusively Roman Catholic. His father was a simple burgher, kindly and studious, who, though he seems to have left the cares of business very much to his more practical wife, while he occupied himself apart with chemistry, music, and literature, was still full of active sympathy with the less studious life around him. Eight daughters had been born to them, but, as yet, no son, when the unexpected fulfilment of a long deferred hope induced, it was thought, a congestion of the brain, under which the poor father rather suddenly succumbed. The child was tenderly reared by the mother and elder sisters, in narrow circumstances, and was probably spoiled, for he became unruly, * For a portrait see frontispiece to the present volume. C Vlll and had to be sent at seven to the village school of Duizel, in the vicinity. Here he rapidly acquired all that the humble master, Mr. Pnnkcn, could impart, and showed such precocity, especially in arithmetic, that the rustics would mount him on the table of the village inn, and give him sums to solve for half-pence. It was thus, perhaps, discovered that he might be safely entrusted with the pay- ment of the weekly wages by an employer, who rewarded him by a little pocket money. " Imagine the little boy with the dark eyes peep- ing out of the black locks" — the fond mother would say — " sitting behind the desk to give the coins to the big workmen !" He was also made responsible for the steady going of the village clock. They used to call him " Master's Frans." In after years, when Bonders, the great Professor, was secretly requiting, by substantial benefits to afflicted relatives, the love bestowed upon him in childhood, such trifling in- cidents as these were recalled and treasured up by loving hearts, and they are, therefore, deemed not unworthy of a passing record here. As he grew to be eleven years old he became so useful in the school that his mother was asked to allow him to remain there as a tutor for two years more at a salary. Thus early did the clever lad begin to exercise that innate aptitude for teaching which he afterwards culti- vated to such perfection. He was subsequently moved on to other seminaries at Tilbnrg and Boxmeer, learned easily to converse in Latin and French, and less fluently in Greek. English he acquired from schoolfellows, since become London merchants, and friends of after life. In music, too, he was an adept, taking the 2nd violin in quartetts. His religious instruction he first received from a sister of charity (beguine), who prepared the children for the priest's teaching. His sister Ther^se seems to have been a remarkable woman. He would relate of her that she was chosen abbess over a pauper establishment by the bishop, although the youngest of the community, and there- fore in her own eyes unworthy. A photograph of her shows her to have been very like Bonders in features. It is not surprising, per- haps, that his early reveries were of the priesthood ; and some in- teresting traits have been preserved, witnessing to his boyish fervour in this direction ; but, with opening manhood, the current of his aspirations, from whatever cause, entirely changed, and he never afterwards for a moment regretted his resolve to embrace a medical career. Having this in view, he would have proceeded to Liege, where his eldest sister was settled, having married M. Grandmont, subse- quently head of the eminent firm of publishers in that city. But the revolution was about to break out, which was to end in the severance of Belgium from Holland, so he turned aside to the University of Utrecht, entering it as a medical student at the age of seventeen, and becoming at the same time a pupil in the Military Hospital. IX " Indescribable " he says, on the occasion of his jubilee, after a lapse of fifty years, " was the impression made upon me here by the chemical lectures and experiments of Nicholas de Fremery. When, for the first time, I mastered the notion that all that exists, in its in- finite variety, is composed of a relatively small number of elements, which in certain proportions unite and reunite, it seemed to me as if, with the creation of the elements, the whole of nature had been given, and my imagination worked this out in its own way. Later on I became especially interested in Physiology, as taught by Schroeder van der Kolk." The term prescribed for admission to his examination for his degree at Utrecht not having yet arrived, he anticipated it by at once proceeding to Leyden, where his unusual proficiency in Latin and his many accomplishments secured for him a brilliant reception from the academical body.* Thus accredited, he went immediately to Flushing as a military surgeon and health officer, and shortly after- wards was promoted to headquarters at the Hague. Here he worked intensely in the hospital wards, made autopsies, contributed papers to the medical journals, and was favourably noticed by the Director- General ; who, being about to reorganise the Military Medical School at Utrecht, flatteringly invited him, then only in his twenty-fourth year, to give the courses on Anatomy, Histology, and Physiology. This was no light enterprise, for it included 18 lectures in the week for the 46 weeks which made up the scholastic year ; but he under- took it joyfully, " feeling teaching to be his true vocation." Thus he came back already distinguished to his own University city, his home from that time onward. There he was soon to become famous. G. J. Mulder, then recently appointed Professor of Chemistry in the University, was already powerfully contributing to give form to the new science of Physiological Chemistry, and his genius at once at- tracted and was attracted by that of Bonders. The two soon became close friends and fellow workers, Bonders occupying himself in every spare moment with microscopical researches in connexion with the chemistry of the elementary tissues, and publishing many original papers.f With Jac. Moleschott also, then very young, he established a lasting friendship, as well as with Opzoomer and others who, in their several ways, became eminent. In those days of opening man- hood, Bonders plunged eagerly and discursively into every avenue of spiritual and intellectual activity. Men of science, lawyers, divines, were alike his intimates, while, in general society, his * His inaugural dissertation, based on original researches, was entitled " Dis- sertatio inauguralis sistens obseryationes anatomico-pathologieas de centre nervoso," 1840. t Vide, e.g., " Proofs of a General Physiological Chemistry," 1843-50, pp. 539 et seq, c 2 musical and artistic temperament, responsive to every refined emotion, hih quick perception and ready memory, his geniality and conversa- tional powers, made his handsome presence everywhere acceptable.* " Bonders was then," writes Moleschott with fervid admiration, " a swelling rose-bud, whose calix leaves signified nothing but pure science, the flower leaves hidden glory. In one word, he was a man complete — perfect for his time of life." His bright intelligence, indeed, was able to assimilate without apparent effort all that it saw and read of in the active world around — a world then agitated by novel questions, of absorbing interest, regarding the Constitution of the Universe and the true import of Man's place and being in it. In those days very recent advances in the methods and aims of exact research, as applied to various branches of science, had made it possible to penetrate more deeply than ever before into many of the profounder mysteries of nature, and some grand enlightenment seemed near at hand. During the years following 1840, one concep- tion in particular, that of the Conservation of Energy in Nature, long foreshadowed, was rapidly assuming definite shape under the ordeal of exact experiment pursued on many converging lines. It could hardly, however, have been said to have become yet established, even in the minds of the most advanced physicists, ere Bonders had clearly recognised its far-reaching importance in its special application to the Science of Life, the foundations of which his keen gaze was then freshly exploring. In the winter of 1844, when but twenty-six, in "only a lecture, not pretending," he modestly says, "to any high scientific worth," he casts a glance on the change of matter as the source of animal heat.f Here we already find him embracing in his view all nature, and looking confidently to her most general and all- pervading laws for the explanation of the enigma of life. " Animal heat is chemical heat ;" but the final and irreversible proof of this, he shows in detail, " can only be given when science shall have proved that the quantity of heat in the animal body answers absolutely to the chemical change which takes place there" "All working- in nature, all life on earth, rests on the change of the elements from which it is formed, but side by side with this change of matter stands a change of forces. Both are inseparably bound up together. As the change of matter is the condition without which no life exists, so the change of forces is the condition without which no life gives evidence of itself. An idea arises gradually in science, which finds confirmation everywhere, absolute contradiction nowhere, an idea * His stature was 6 feet 1 inch ; circumference of bead, 24 inches, English. t " A Glance on the Change of Matter of Epitellurian Life as the Source of Proper Heat of Plants and Animals," by Dr. Bonders, Military Doctor, 2nd Class, at the Military School of Medicine, delivered in the Society of Sciences, Utrecht ; Van der Post, Feb. 1845. [In Dutch, never translated.] XI great and all-encompassing, fertile for tlie future development of science, it is the Permanence of Forces. No one molecule of matter can be destroyed, but neither can a minimum of Energy. Thus runs the important hypothesis which may come to be the soul of natural science. The forces change and join, they appear under different forms, but no force is annihilated. Determinate quantities of move- ment, heat, light, electricity, magnetism, and nervous force respond to each other, and can pass from one into the other." " There is therefore a sum of energy, just as much as there is a sum of matter ; both are proportionate to each other, both remain always the same." And Donders was hardly less prescient as he stood on the threshold of that other great achievement of our era, the doctrine of the Evolution of Organisms on our planet. The knowledge of the elements and of the elemental forces, then rapidly extending, was being more and more applied to the elucidation of certain vital problems, on which the greatest minds had long speculated in vain. Standing as we now do in the fuller light of those crowning dis- closures of the progression of living nature through past ages which we owe chiefly to the genius of Darwin and of Wallace, dealing with an opulence of new materials for thought, it is very interesting to notice how Donders, in that nascent period, regarded this momentous subject. Already, in 1846,* he had briefly contested the then all but universally accepted teleological notion of the origination of organic forms by separate creative interpositions, accounting it to be arbitrary and unscientific ; and soon after, on being called to the Professoriate of the University, he deemed the topic " weighty enough for a wider treatment, and because of its general bearing, well suited to an inaugural discourse. "f Herein, after passing in review the grander features of the material universe and of the earth, as then known, he strives to show that the harmony everywhere pervading living nature, then usually explained by the principle of design {conformity to an end), is simply a necessary result of the condi- tions under which all organisms have come to be what they have been, or are. Though by no means denying the existence of a purpose in the phenomena of nature, he insists that a doctrine of the purpose can never become science, and can indeed only tend to obstruct the progress of science by lulling to sleep the spirit of enquiry into the laws governing the phenomena. These remain open to investigation in the field of life, just as in that of inanimate matter. It is remarkable how firmly Donders here grasps the certainty that all life has been ever in process of being moulded into its specific forms by the continuous operation, through long ages, of laws * ride Qids, 1846, pp. 893 et seq. t " The Harmony of Animal Life, a Manifestation of Laws." By F. C. Donders, 28th Jan., 1848. [Also in Dutch, never translated.] implanted in matter and the forces of matter ; and that these laws have gradually but necessarily at every stage been operative on the plastic organisation, adapting it continuously to the new conditions which it was ever encountering ; in default of which adaptation and renovation of the disturbed harmony, the organisation itself could not have survived. The laws must be studied in the^ phenomena ; and he particularly discusses and illustrates the operation of three laws, which for shortness' sake he calls those of habit, of exercise, of inheritance. But it is not enough, he adds, to deduce the necessity of the harmony from these laws ; we must endeavour to fathom these laws themselves more deeply. The two former, those of habit and of exercise, mutually interacting, continually tend towards a restora- tion of the harmony between the organism as a whole and its sur- roundings, and between the several component parts of the same organism, as the harmony becomes by little and little disturbed in lapse of time by the intercurrence of altered conditions. The last law, that of inheritance, carries over into the future the accumulated modifications of the past, so far as they have survived in the latest offspring, thus preserving the continuity of life through successive generations, but only by essential changes in its forms. " Already some light dawns in science on the causes of the phenomena we referred to, the laws of habit and of exercise ; and thus, ascending from cause to cause, without ever losing ourselves in dreams about the purpose, we approach, slowly it is true, but with firm step, the ideal point of view, according to which all the phenomena of nature will be seen proceeding from the attributes of the elements and elementary forces. And if once by an All-wise Omnipotence these elements and forces have been created for a predetermined purpose, and if the conditions of the whole future have been enshrined in their attributes, then also not a single drop of blood flows without purpose through our veins, but it is a purpose which lies outside the science of nature." As Donders had originally approached physiology from the side of medicine, so now he had evidently come to meditate deeply on this great theme of the procession of organic forms down the tracts of time on independent grounds of his own, and rather as a physiologist than as a naturalist. As other matters were engrossing his attention, he did not pursue this one to further conclusions ; but he welcomed with delight the publication, in 1859, of Charles Darwin's book, ' The Origin of Species ;' became, subsequently, the friend and correspond- ent of its illustrious author ; and visited him at Down. He also, some years later, undertook, at his request, more than one elaborate inves- tigation,* designed to elucidate obscure questions relating chiefly to * E.g., " On the Action of the Eyelids in Determination of Blood from Expi- ratory Effort," by F. C. Dondere, translated in Scale's ' Archives,' 1870. See also xm his work, ' On Expression of the Emotions in Man and Animals,' then under preparation. Almost casually, in one of his letters to Darwin (14th March, 1871), thanking him for a copy of ' The Descent of Man,' Donders thus summarises in our language his own views of 1847 : " I always took a great interest in the question of the origin of organised beings. Even in 1847 I wrote and published an essay (oratio inauguralis) on the subject ' Harmony of Animal Life, a Manifestation of Laws,' con- taining, from the physiological point de vue, a farther development of the doctrine which had been indicated by Lamarck, although the communications on this subject of Lamarck were as unknown to me as almost to every one, in that period. Fully excluding final causes from scientifical research and theory, I tried to show how the infinite harmonical relations, on the one hand, between animals and sur- rounding nature, on the other hand, between the different parts and organs of every organism, are to be deduced from the laws of adapta- tion by habitude and by exercise, and from the laws of transmission. I applied the same on the psychical actions. I admitted the gradual evolution of the highest orders of plants and animals from more simple forms of spontaneous origin, and the origin of different specie? from the same source. I indicated the changes which are obtained by artificial selection, found the cause of continual progress in the circumstance that every not well adapted form necessarily is con- demned to perish, but still was not aware of the influence of natural selection, your great and immortal discovery, the mighty factor, which alone allowed to give a full and special demonstration of the theory of descent. As I began to write, I had not the intention to mention to you my little book, but, telling about my special interest in the subject, I rather involuntarily inclined to explain it. And now, although it is Written in Dutch, I could not resist my wish to send you a copy, in the hope that you will benevolently accept it. . . ." Darwin replies (18th March, 1871), "... I have been interested in what you tell me about your views, published in 1848, and I wish I could read your essay. It is clear to me that you were as near as possible in preceding me on the subject of Natural Selec- tion." And afterwards (June 19th, 1871), "... When reading over your several letters, the thought has often crossed my mind how incomparably better an essay on expression you could have written than that which I shall be able to produce. . . ." ; (April 8th, 1872) " . . . I feel, every day. that to write on Expression, a man ought to have ten times as much physiological knowledge as I possess. . . ." ; and (December 21st, 1872) "... My book on Expres- sion, in writing which I was so deeply indebted to your kindness "- ' Life and Letters of Charles Darwin,' by Francis Darwin, vol. 3, and C. DarwitL ' On Expression, &c.,' 1872, p. 160. XIV sentences, honourable alike to each of these eminent men, exhibiting true modesty, transparent candour, and in all simplicity a most generous appreciation of merit in the other.* But to resume the tenonr of Bonders' life. In 1847, that his ser- vices might the better be secured to his University, he was named Professor Extraordinary, there being no vacancy among the ordinary chairs ; and such was the confidence inspired by his character that he was asked to select his own subjects for lecture. He chose four, viz., Forensic Medicine, Anthropology (especially for students in theology and law), General Biology, Ophthalmology. To this last he had been drawn, not only by its own intrinsic charm, but from his having, in the preceding year, in order to eke out his slender resources (for he had now wifef and child), undertaken a Dutch translation of the great German treatise of Ruete on that subject, and from having thereupon thrown himself, as was his wont, heart and soul into what- ever lines of original research this work, as it proceeded, had sug- gested to him. It is impossible here to particularise, but several of these were among the more subtle problems lying on the borderland of physiological optics, problems remaining to perplex even the most observant practitioner, until by their solution the path is made clear to all alike. Suffice it that Bonders in this way became more and more attracted towards Ophthalmic Practice ; for with readiness he gave all the help in his power to the physicians and patients who were eagerly approaching him, as they heard of his discoveries in the physiology of vision. And when it was proposed to him by some of our passing countrymen that he should acquaint himself with English methods of treatment, then much esteemed abroad, he came to London in 1851, on the occasion of our first " Great Exhibition," return- ing by way of Paris. Some of the incidents of this journey he himself soon after placed on record,}; and he always spoke of it as having had a great influence in moulding his life. It was his first travel, and it brought him, at least, one thing for which he had great reason to be thankful — the personal friendship of Albrecht von Graefe, an asso- ciation soon to be fraught with splendid results for the expanding science of Ophthalmology ; for these two men, both of the first capacity, laboured ever afterwards to advance it as brothers in council, and alike fruitfully; freely communicating their ideas to each other, always in perfect harmony of aim. While von Graefe, a stranger in London, was able to tell Bonders of the European hos- pitals he had been visiting, and of the new clinical ideas he was * Vide Chas. Darwin ' On Expression, ic.,' Nov. 1872, p. 160, &c. The writer is indebted to Mr. Francis Darwin for the opportunity of perusing these letters. t His first wife was Ernestine J. A. Zimmerman, daughter of a Lutheran pastor. (She died Sept., 1887.) J Notes on London and Paris, ' Nederlandsch Lancet,' 1852. XV maturing*, as well as of the construction in that year, by Helmholiz, at Konigsberg, of a dioptric apparatus for rendering visible the fundns of the eye, Bonders, a stranger there too, could, on his side, explain many discoveries of his own in the physiological field, and, among other things, declare the true nature of the act of accommoda- tion, quite recently disclosed with certainty by his countryman Cramer, under, it may be added, his own inspiration and in his own laboratory. It was somewhat later, though independently, that Helmholtz arrived at the same conclusion. It is not wonderful that Bonders, on his return to Utrecht, should have already decided on adding to the abounding work of his four- fold lectureship, including the theoretical side of Ophthalmology, the onerous responsibility of its daily practice. He had, in fact, been gradually led to recognise more and more that this department of the healing art, from the very nature of its subject-matter, affords an ampler scope and a firmer ground than any other for the applica- tion and exemplification of those scientific principles which must eventually bear sway in all its departments, if vagueness and uncer- tainty are to disappear under the slow but certain advances of exact knowledge.* But in addition he was then swayed by a special impulse hard to be resisted. It had long been known that in animals having a tapetum luctdum the rays of light entering the eye through the pupil are in part reflected outwards by that shining surface along the lines of entrance ; and in 1846 our countryman Gumming, too early lost to us, had shown that in man also such a reflex was in a certain way demonstrable. But, in 1851, Helmholtz discerned that it must surely be possible, by an optical contrivance, to render visible the reflecting fundus itself by bringing these emergent rays to a focus upon the retina of an observer; and, as just mentioned, such means he had devised. The Ophthalmoscope was thus given to mankind, a dis- covery rather than an invention, as Helmholtz has himself remarked — a revelation transforming ophthalmology, and of itself entitling that great man to our ever grateful remembrance. In the words of Bonders, " the whole world spoke of it ; every one wanted to see the ophthalmoscope, which revived long-lost hope." But Bonders felt that a sphere for its employment in Holland was still needed ; and his fellow citizens, appealed to for this, and fired with some of his own enthusiasm, provided him with a temporary hospital ; a few years later subscribing funds for a permanent one.f " That result," he remarks, " was obtained through the influence of the discovery of the ophthalmoscope and the appearance of von Graefe at Berlin." " In * Vide Francisci Cornell! Ponders, oratio de justa necessifcudine scientiam inter et, artem medicam, et de utriusque juribus et mutuis officiia, quam habuit die xxvi m. Martii a. MDCCCLIII, quum magistratum academicum deponeret. f Opened February, 1859, with forty beds. XVI those days " (he proceeds) " — I may here tell what I have kept secret till now — I was invited by the medical faculty of Bonn to be the successor of Helmholtz [as professor of physiology]. It was the unanimous wish of all the members of the faculty, including Helm- holtz himself, then about to leave Bonn. The offer might have been tempting. With a gift of 40,000 florins in my hand, for a purpose marked out by myself, it could not be thought of. The Ophthalmic Hospital thus founded was to be an institution for patients, but also for investigation and research in Ophthalmology in its widest range, in connexion with the University, by which both science and practice might be advanced ; and not only did our students share its ad- vantages, but foreign fellow practitioners made their appearamv to witness our proceedings and to participate in our enquiries." These last had reference to a variety of problems presented in the course of the practical work which Donders now entered upon, but chiefly to the " Refraction and Accommodation Anomalies," which were found to be greatly more common than had been supposed, and to admit in large measure of exact definition and correction. In 1858, there appeared the first of a long series of essays, in which, during six years, he was able to propound a complete doctrine, com- plete as it left his hands, both as to theory and practice, of the employment and prescription of corrective glasses, a subject never really mastered till then, and yet of the widest importance in every- day life, for the young, the middle-aged, and the ofd of all classes, and for all future time. His results, elaborated down to their minutest details, were then arranged and collected into a volume, which it was his wish to offer to the world first, in its entirety, in an English form, as a reminiscence perchance of the welcome he had experienced here in 1851. This volume, as translated from the Dutch MS. by Dr. Moore, of Dublin, and revised by himself, was accordingly published by the " New Sydenham Society " in 1864, and dedicated to an English friend.* It was soon out of print, passed into several languages, and must remain the permanent classic, both as to theory and practice, on the topics embraced by it. To attempt an analysis of it would be beyond the scope of the present notice. It constitutes the title on which its author takes rank above all his contemporaries as the main founder <5f a very large province of modern Ophthalmology. But it must not be supposed that these results, memorable as they were, stood alone among the achievements of Donders in those fertile * ' On the Anomalies of Accommodation and Kefraction of the Eye, with a pre- liminary Essay on Physiological Dioptrics.' By F. C. Donders, M.D., Professor of Physiology and Ophthalmology in the University of Utrecht. Translated from the author's MS. by Wm. Daniel Moore, M.D., Dublin. The New Sydenham Society, London, 1864. XV11 years. He was also enriching Physiology in other directions, even though well-nigh exhausting his strength in doing so : for he had been also serving the University as Rector, an office which he re- linquished in 1853.* In conjunction with Dr. Bauduin he undertook a Manual of Physiology, which, however, he could only carry as far as the first volume, ' Special Physiology ' (1853) — for its time a work of authority, and still the best record of contemporary teaching. In 1857, he discovered that in each vowel sound the mouth is tuned to a definite pitch, alike in men, women, and children using a common speech, and differing only with difference of dialect ; this was confirmed by Helmholtz. Again, in 1865, Bonders took the first step in a new field of research, by determining the rapidity of perceptions of Thought and of the Will. Others had arrived at the physiological time, or that required for reacting by a movement on a nervous irri- tation. But in the next succeeding years he carried these exquisite investigations much further, analysing the time taken in simple, and also in many and various complex, psychical processes, by a most ingenious and refined method, which he explained in 1876, at one of the Conferences at South Kensington in connexion with the Loan Collection of Scientific Apparatus. t Others of his physiological papers deserving special mention, among a great number, were : " On the timbre of the Vowels," "Muscular Work and Development of Heat in relation to the necessary Elements of Food," " On the Tongue-instruments in the Organs of the Voice and Speech," " Influence of the Vagus Nerve on the Cardiac Movements," " On Associations, congenital and acquired " (the latter are the result of habit in the individual, the former represent habit in the species), " The Chemical Phenomena of Respiration are a Process of Dissocia- tion;"— indeed, to the close of his life he remained indefatigable in the domain of Physiology, almost continuously winning new laurels in one or other of its departments. In 1862 an event had occurred having an important influence in this direction. By the death of Schroeder van der Kolk the chair of Physiology fell vacant, and it was immediately pressed upon his acceptance, with the understanding that a new Physiological Laboratory should be erected for his use. This was an appeal he could not withstand, though aware that it would involve a partial, and, gradually, an almost complete, relinquishment of his ophthalmic practice. But Physiology in its widest range, with the ample field it presented for Research, had been his first love, and to this his inclination now gradually led him back. His esteemed pupil, Snellen, became his colleague at the Hospital, and eventually succeeded him there ; while Thomas W. Engelmann, who was to be in course of * Vide note *, ante, p. IT. t Vide ' Science Conferences,' 1876, Section Biology, pp. 224—228. XV111 time his much loved son-in-law, became his assistant in the Labora- tory, and finally, his eminent successor. Bonders continued in these new circumstances to display the same marvellous productiveness as heretofore, and to animate, by his influence and example, the younger men attracted to him, often from distant countries. He delighted, as he had ever done, to make them taste the joy of becoming themselves the authors of some original work of value, and to engage their interest and help in his own laborious and systematic inquiries into whatever promised to benefit mankind in t.he sphere of the sciences he was cultivating. No better example of this generous ardour of pursuit could be adduced than his method of dealing with the subjects of the Colour Sense and of Colour Blindness, then more and more attracting atten- tion in relation to the public safety. It exhibits very aptly his many- sided excellence. While acquainting himself with the ideas of his predecessors, he first statistically ascertained, with accuracy for him- self, the broader facts, engaging for this the aid of his younger colleagues and pupils. The delicate instruments which he was from time to time contriving in the course of his researches bearing on the theory of the Colour Sense and its defects, as on other subjects,* were constructed in a special department of his laboratory by the mechanician Kagenaar, whom he had reared from a youth and made his friend. His theoretical conclusions, as they were reached, were published in papers of permanent value.f Meanwhile he was also calling the attention of the higher officials of the railway and sea services, of his own and other countries, by all the means within his power, to the responsibilities they lay under for the lives of the com- munity, in the matter of Colour Blindness ; was framing rules for their acceptance, which they might suitably enforce ; and pressing his conclusions to their final consequences in practical life, with such directness, moderation, and good sense, as compelled the attention and assent of administrators and statesmen. And that he might not fail in his immediate object of effecting a present benefit, he further, for many years personally undertook, without remuneration, the very considerable labour of superintending the carrying out of this matter on the railways of Holland, examining scrupulously into the more doubtful instances of supposed defect, so as to prevent injustice to individuals, and in every way facilitating the adoption of the new rules which he had suggested. No wonder that his countrymen, * Many of these instruments were exhibited at South Kensington in the Loan Collection of Scientific Apparatus, 1876. t His views of that day " On Colours and Colour Blindness " were well summarised by himself in the theatre of the Lucasian Professor at Cambridge, August, 1880, Sir George Or. Stokes being present. See ' Brit. Med. Journ.,' 13th November, 1880. XIX even the humblest, followed him with grateful recognition when he appeared at the stations or moved among them. Indeed, his life was one of incessant labour and benevolent endeavour to turn to useful ends each new insight into nature which he and others were acquiring. Sympathising with all, seeming to understand the sentiments and interests of all, he was generous as well as just in his judgment of others, yet ever courageous and firm in the assertion of whatever he deemed to be right and true. Indefatigable in the pursuit of truth, he was as able in imparting it. Eloquence, the graces of style, and the mastery of several languages combined to make him a great teacher. Even in his youth he had become conscious that to teach was to learn, and that to learn was the purest of intellectual enjoyments. " I was already in correspondence with Bonders," says von Helm- holtz, in a letter to the present writer, " before 1856, when I lived in Konigsberg. He had sent me his physiological treatise on Animal Heat and his handbook on Physiology, and as I had then made the first experiments on the change of form of the crystalline lens in accommodation, he told me about the somewhat earlier experiments made by Cramer in his laboratory. As far as I know, I first made his personal acquaintance during my stay at Bonn, between 1856 and 1859. He used to go in summer, with his then already ailing wife, to Cleve, to breathe purer air in that hilly country, as was then the fashion in Holland. From thence he came over to Bonn. I have also paid him a visit of a few days, in Utrecht, at that time, and lived in his house. . . . The loveablcness, openness, and honesty of his character you know — I need not portray them to you. We have then and afterwards discoursed very much on scientific questions, as we many times and independently had taken the same problems in hand. He had, in Ophthalmology, the greater experience of patients, and I have learnt much from him in that respect ; but even where it seemed to me that I must maintain my own opinion, I never observed in him the least sign of sensitiveness, or of too great warmth in defending his position. In his way of talking he had then already, as a young man, something of stateliness ; he loved choice expressions, remind- ing one somewhat of the antique eloquence of the French Academy. But he was never prolix, indeed, rather concentrated, in his conversa- tion, and I have always loved to listen to him, though in Germany we are very little accustomed to attend much to the artistic oratorical element in speaking. He was clearly a warm-hearted man with great ideal views, and he thought it his duty to give utterance to these ideal views before the world, and to show them in their height and significance. Moreover, he was aware of- his capacity of im- pressing this with great force upon his auditory. Very beautiful in this respect was his last speech in handing over the Graefe Medal at XX Heidelberg."* ..." Our friendship has remained unclouded to the last." Bonders took, from time to time, a very conspicuous part in the assemblies and congresses of Science. Here he shone as a star of the first lustre. By universal consent he was a most admirable President, particularly where men of many nationalities were met together ; for his wide and accurate knowledge and accomplishments, his tact, the grandeur of his simple earnestness, and his magnificent personal bearing acted as a spell on all. If the occasion seemed to demand it he would give an address, sentence by sentence, in two or more languages, with perfect mastery. He presided over the fourth Inter- national Congress of Ophthalmologists in London, 1872, and again, for the last time, over the seventh meeting of the same at Heidelberg, in 1888 ; over the sixth International Medical Congress, at Amster- dam, 1879 ; and he was Vice- President, as well as Royal Medallist, of the seventh International Medical Congress in London, 1-881. In his own country, from 1865 onwards, he annually presided over the Physical Section of the Royal Academy of Sciences, and (alternately with the President of the Literary Section), was President in plena. Bat in 1883 he expressed the wish to withdraw from some of the more arduous of his many engagements. He was soon, alas ! to cease from the service of the University for which he had done so much- By the law of the Netherlands a Professor must retire at seventy. He was approaching that age, apparently in full vigour, though indications of gouty congestions had more than once occasioned some disquietude to his friends. His Jubilee was celebrated at Utrecht, on the 27th and 28th May, 1888, amid the universal applause of his countrymen and of men of science everywhere. He was decorated by the King, and in his honour a commemorative medal was struck. Forty of his former pupils communicated each an original scientific paper to a memorial Festival volume, published by a committee. f The Royal Society of London, which had elected him a Foreign Member in 1866, asked three of its Fellows, Sir Joseph Lister, Mr. Jonathan Hutchinson, and Dr. Hughlings Jackson, to convey to him its con- gratulations ; our Physiological and Ophthalmological Societies also sent deputations. Indeed, hardly one civilised country but was in some way represented. A large sum had been subscribed, and was placed at his disposal. He assigned it to the establishment of Travelling Fellowships in Physiology and Ophthalmology, to be attached to the Universities of the Netherlands, with Utrecht as a centre; not without a glance, perchance, at an early incident in his own fortunate career. That career he now passed in review * Viz., to von Helmholtz himself, 9th August, 1886. Vide ' Festsitzung der Ophthalm. Gesellschaft, &c.,' Rostock, 1886. t ' Feestbundel Donders-Jubiteum, &c.,' pp. 546, Plates xvii. XXI before his assembled friends and pupils in a speech of touching simplicity and eloquence — a lasting and truthful survey of the lifework he had been enabled to accomplish. " I may be thank- ful," he concluded, "for the life granted me. I stand here comparatively strong, and also ready to do what may be given me to do. I stand here, having reviewed my life, and having seen how manifold were the advantages that have been allotted to me. All this makes me grateful, fervently grateful, especially to the Eternal Source of all that exists, of which it is not given to man — a speck in the infinite space, a breath in the infinite time — to form an idea ; he can do no more than bow reverently in absolute submission. This submission has been asked of me more than once. I hope also to find the strength to submit to what may be required of me in the future." Some sorrowful bereavements had indeed befallen him : in the loss, in 1870, of his only child Marie, after giving birth to twins ; and more recently, in 1886, of the beloved and admirable partner of many years, after a long and distressing illness, through which he had nursed her with the tenderest assiduity. But he remained steadfast and full of trust, and he had many compensations. The retrospect of his life was happy ; his contemporaries loved and honoured him as few men have been loved and honoured, recognising in him in a rare degree the possession and harmonious, fruitful, and lifelong exercise of some of the greatest and best attributes that can adorn human nature. The last illness of Donders was sudden, as his father's had been, and in him, too, it was the circulation of the brain that failed. That powerful organ of sweetest feeling, high aspiration, and self-restrained will, which had enabled him to accomplish so much, even measuring for us the velocity of thought, was now itself to give way. He had come on a visit to England in October, 1888, and seemed to be supremely happy in the renewal of his domestic life. Most interest- ing was it to listen to the themes he opened as to the work he might soon undertake in the studio of his refined home, tracing the springs of Art to their most secret source in the very constitution of man's bodily organisation, subject in all respects to the conditions and limitations imposed by physiological laws. The operations of these laws he had long delighted to track out to their remotest conse- quences, and to communicate his conclusions to masters in art of the quality of his friends Sir Fred. W. Burton and G. F. Watts. His studies had always inclined him in this direction, and he now hoped to execute a design he had long cherished, of illustrating his concep- tions and views by reference to the life of Leonardo da Vinci, the great artist with a scientific turn of mind, to whose figure he had ever felt himself especially attracted. In such a field, had his days XX11 been prolonged, it is probable that ho would still have left behind him rich legacies of thought (for who so capable ?), in which rigidly exact definitions of scientific trnth would have been seen to be in truest harmony with the most exquisite sensibility to every form of beauty, natural or artistic. Bat the joy of anticipation was a perilous joy, and could not be long supported. Pathetic were the circumstances of the last fatal seizure, for in the intervals of illness he knew and weighed as in a balance of the laboratory all its phases, with unimpassioned serenity and resignation, though not without sadness, while witnessing the grief of those who loved him, and recalling the scenes in which he had acted so conspicuous a part. He rallied sufficiently to be able to return home under the escort of his brother-in-law, who had been summoned to his bedside in England. But relapses recurred, with varying alternations and pauses. During these weeks of suspense, so agonizing to his friends, he often spoke of the insoluble riddle of exist- ence, and of the hope of a future reunion. One afternoon he had walked with assistance in front of his house (it was his last walk), and he seemed refreshed. " We have had a nice walk, and you are better," said one. " Yes," he replied, " a beautiful walk — is it not a beautiful walk ?— to Eternity ! " He died on the 24th March, 1889, within a year of his jubilee. The day of his burial was indeed one of gloom in Utrecht. The second wife of Donders was Bramine, daughter of Mr. P. F. Hnbrecht, Secretary of the Home Office at the Hague, sister of Pro- fessor Hubrecht, of Utrecht, a lady of noble disposition and of wide culture. We owe to her remarkable talent several fine portraits of him, for one of which, a three-quarter length, painted for his jubilee, she received the award of a gold medal at Munich in 1888. It is destined for the National Museum at Amsterdam. Others are, a half- length, with his decorations, in the Hall of the Professors at the University ; one at the Ophthalmic Hospital, representing him as in 1864, soon after the foundation of the hospital ; and a fourth, as seated in his study, with the bust of von Helmholtz at his side, in the last year of his life, painted for his twin grandchildren, Frans and Paula Engelmann. There ar§ also two life-size heads by Mr. Watts, R.A., painted in 1873-75, during some of his brief visits to England. One of these, never completed, but remaining a grand sketch, forms one of Mr. Fred. Hollyer's series of Mr. Watts's por- traits, and has been reproduced as the frontispiece to the present volume of the ' Proceedings of the Royal Society ' by Mr. Dew- Smith, of the Cambridge Engraving Company. Both this and the jubilee portrait were exhibited at the Royal Society Conversazione, XX111 18th June, 1890. There is, lastly, a life-size oil picture of Bonders as he was in 1881, for which the writer is indebted to the kindness ol his old friend E. U. Eddis, Esq. Some Published Notices of FEANS CORNELIS DONDKRS. Some Earlier Ones. — (1.) A. Kolliker, Skizze einer wissenschaft- liclien Reise nach Holland und England in Briefen an C. Th. v. Siebold. Zeitschrift f. Wissensch, Zoologie v. C. Th. v. Siebold und Kolliker, vol. 3, 1850, p. 86. (2.) F, C. Bonders, Notes on London and Paris. Nederlandseh Lancet, 1852 (translated into English at the time). (3.) Photographs of Eminent Men of all Countries, with Brief Analytical Notices of their Works. By T. Herbert Barker, M.B., and Ernest Edwards, M.A., 4to, London, 1867-8, vol. 3, pp. 93-104. Later. — (4.) F. C. Bonders, Biscours d'Ouverture, Con- •gres International des Sciences Medicales, Amsterdam, 1879. Edition corrigee. (5.) Festsitzung der Ophthalmologischen Gesell- «chaft in der Aula der Heidelberger Universitat am 9 Aug., 1886. — Ueberreichung der Graefe-Medaille an Hermann von Helmholtz, Rostock, 1886. (6.) Het Jubileum van Professor F. C. Bonders gevierd te Utrecht op 27 en 28 Mei, 1888. — Gedenkboek uitgegeven door de Commissie, Utrecht, P. W. Van de Weijer, 8vo,pp. 210, 1889. (7.) Franciscus Cornelis Bonders. Festgruss zum 27 Mai, 1888. Bargeboten von Jac. Moleschott, 8vo, pp. 51, Giessen, 1888. Some Obituary and other Notices. — (8.) Mort de Bonders. Annales d'Ocu- listique, publiees par le Br. Warlomont, 8vo, pp. 141-144, Mars- Avril, 1889. (9.) Franz Cornelius Bonders, M.B. Brit. Med. Journ., 30th March, 1889 (by W. A. Braiiey). (10.) F. C. Bonders, par le Br. E. Landolt, Extrait des Archives d'Ophtalmologie, Mai-Juin, 1889 (a just and eloquent tribute, translated in ' The Illustrated Medical News,' 14th September, 1889, with a portrait). (11.) Bie Ophthalmologische Gesellschaft wahrend der ersten fiinfundzwanzig Jahre ihres Bestehens, von 1863 bis 1888. Im Auftrage des Aus- schusses zusammengestellt und herausgegeben von Wilhelm von Zehender, 8vo, pp. Ill, Rostock, 1888. (12.) Commemorazione dell' Accademico onorario Francesco Cornelio Bonders, &c. Letta dal Prof. G. Colasanti nella seduta del la R. Accademia Medica di Roma il 28 Aprile, 1889, 8vo, pp. 16. (13.) F. C. Bonders, Klinische Monatsblatter fur Augenheilkunde, herausgegeben von Br. von Zehender, Mai, 1889, 8vo, pp. 163-168. (14.) Prof. Snellen (notice of Bonders) ' Het Nederlandseh Gasthuis voor Behoeftige en Min- vermogonde Ooglijders gevestigd te Utrecht,' 2) Ju!i, 1889. (15.) F. C. Bonders et son CEuvre, par Prof. J. P. Nuel (Liege), 'Ann. d'Ocnlistique,' 8vo, pp. 1-107, 1889 (with an analysis of 208 of Bonders' papers and treatises, and a portrait — a full and admirable XXH' account). (16.) F. C. Bonders, Gedenkiv.lr ^i-halten in der licben Jahressitzung der Budapester Kon. Gesellschaft der Aertze am 14 Oct., 1889, von Dr. W. Goldzieher, 8vo, pp. 28. (17.) Bericht iiber die Zwanzigste Ver8ammlung,der Ophlhalmologischeu Gesellschaft, Heidelberg, 1889 ; redigirt durbh W. Hess nnd W. Ze- bender, Rostock, 14 Dec., 1889. (18.) Mannen van Beteekenis in onze Dagen, Redactie : Dr. E. D. Pijzel.— Breijer, 1890 (a true and deeply interesting tribute to Dondefs' work and character, by:i. Brunton (T. L.) and J. T. Cash, contri- butions to the study of the connexion between chemical constitution and physiological action. Part II, 311. INDEX. XXVll Callendar (H. L.) and E. H. Griffiths, on a determination of the boiling point of sulphur, and on a method of standardising platinum resistance thermometers by reference to it, 56. Camphors, and camphor acids, on the constitution of the terpenes (Collie), 554. Candidates for election, list of, 304. list of recommended, 491. Carus-Wilson (C. A.) the rupture of steel by longitudinal stress, 243. Casey (John) obituary notice of, xxiv. Cash (J. T.) and T. L. Brunton, contri- butions to the study of the connexion between chemical constitution and physiological action. Part II, 311. and W. E. Dunstan, the physiolo- gical action of the paraffinic nitrites considered in connexion with their chemical constitution. Part I. The action of the paraffinic nitrites on blood pressure, 314. Cassie (W.) on the effect of tempera- ture upon the refractive index of certain liquids, 343. Chemical constitution, the physiological action of the paraffinic nitrites con- sidered in connexion with their. Part I. The action of the paraffinic nitrites on blood pressure (Cash and Dunstan), 314. Chemical constitution and physiological action, contributions to the study of the connexion between. Part II (Brunton and Cash), 311. Chromatin, on the demonstration of the presence of iron in, by micro-chemical methods (Macallum) , 488. Ciliary action, on the structure of amoe- boid protoplasm, with a comparison between the nature of the contractile process in amoeboid cells and in mus- cular tissue, and a suggestion regard- ing the mechanism of (Schafer), 193. Cloud photography conducted under the Meteorological Council at the Kew Observatory (Strachey and Whipple), 467. Coal-measures, on the organisation of the fossil plants of the. Part XVIII (Williamson), 154. Coerulin and alizarin-blue as sensitisers for rays of low refrangibility, on the bisulphite compounds of (Higgs), 345. Collie (J. N.) on the constitution of the terpenes, camphors, and camphor acids, 554. Colour, the numerical registration of (Abney), 227. Colour blindness, on the examination for colour of cases of tobacco sco- toma, and of abnormal (Abney), 491. Couroy (Sir John) elected, 491. Corpus vitreum, on a membrane lining the fossa patellaris of the (Stuart), 137. Croonian lecture (Q-otch and Horsley), 235. Crystalline lens and the lens capsule, on the connexion between the suspen- sory ligament of the (Stuart), 141. Crystals, some measures of Young's modulus for (Mallock), 380. Cunningham (Daniel John) elected, 491. Cygnus, on Wolf and Eayet's bright- line stars in (Huggins and Huggins). 33. Darwin (Or. H.) on tidal prediction. — Bakerian lecture, 130. Dawson (George Mercer) elected, 491. Delepine (S.) contribution to the study of the vertebrate liver, 64. Dentine, some points in the structure and development of (Mummery), 319. Dewar (J.) and G. D. Liveing, on the influence of pressure on the spectra of flames, 217. Bonders (Frans Cornells) obituary notice of, vii. Dunstan (W- &•) and J. T. Cash, the physiological action of the paraffinic nitrites considered in connexion with their chemical constitution. Part I. The action of the paraffinic nitrites on blood pressure, 314. Dyer (W. T. T.) note on Dr. Fenton Evans* paper on the pathogenic fungus of malaria, 539. Electric and magnetic screening, on variational (Thomson), 418. current, the measurement of the power given by any, to any circuit (Ayrton and Sumpner), 424. currents, on the sensitiveness of the bridge method in its application to periodic (Rayleigh), 203. Electricity, on the rate of propagation of the luminous discharge of, through a rarefied gas, 84. Electrodynamics, on the theory of (Larmor), 521. Electrostatic screening by gratings, nets, or perforated sheets of conducting material, on (Thomson), 405. Elliott (Edwin Bailey) elected, 491. Ellipsoidal harmonics, on (Niven), 1. Ellis (Alexander John) obituary notice of, i. -, — ... d 2 XXV11I IVKKX. Ktlivl oxide, an attempt to determine the atiiabatic relations of. Part 1. Gaseous ether (Ramsay and Perinan), 447. Evans (J. F.) on the demonstration by staining of the pathogenic fungus of malaria, its artificial cultivation, and the results of inoculation of the same, 199. note on the above (Dyer), 539. Finger-marks, method of indexing (Gallon), 540. Flames, on the influence of pressure on the spectra of (Liveing and Dewar), 217. Flesh, on the bases (organic) in the juice of. Part I (Johnson), 538. Fluid pressure, note on the instability of india-rubber tubes and balloons when distended by (Mallock), 458. Focometry of lenses and lens-combina- tions, on the, and on a new focomeler (Thompson), 225. Fossa patellaris of the corpus yitreum, on a membrane lining the (Stuart), 137. Fossil plants of the coal-measures, on the organisation of the. Part XVIII (Williamson), 154. reptilia, researches on the struc- ture, organisation, and classification of the. VII. Further observations on Pareiaaaurtts (Seeley), 518. Frankland (Percy Faraday) elected, 491. Fungus of malaria, on the demonstra- tion by staining of the pathogenic (Evans), 199. note on Dr. Fen ton Evans* paper on the pathogenic (Dyer) , 530. Galton (F.) method of indexing finger- marks, 540. Galvano-hysteresis, on. Preliminary notice (Thompson), 439. Gas, on the rate of propagation of the luminous discharge of electricity through a rarefied (Thomson), 84. Gilchrist (Percy C.) elected, 491. Gotch (F.) and V. Horsley, on the mammalian nervous system ; its fun- tions and their localisation determined by an electrical method. — Croonian lecture, 235. Griffiths (E. H.) and H. L. Callendar, on a determination of the boiling point of sulphur, and on a method of standardising platinum resistance thermometers by reference to it, 56. Halliburton (William Dobinson) elected, 491. Hannen (Lord) elected, 323. admitted, 359. Hartley (W. N.) on the physical cha- racters of the lines in the spark spcct r i of the elements, 448. Haycraft (J. B.) on the minute struc- ture of striped muscle, with special reference to a new method of investi- gation, by means of "impressions" stamped in collodion, 76, 287. Heat capacity and heat of fusion of some substances to test the validity of Person's absolute zero, determina- tions of the (Pickering), 11. Heaviside (Oliver) elected, 491. Higgs (G.) on the bisulphite compounds of alizarin-blue and coerulin as sen- sitifiers for rays of low refrangibility, 345. Horsley (V.) and F. Gotch, on the mam- malian nervous system ; its functions and their localisation determined by an electrical method. — Croonian lec- ture, 235. Huggins (W.) on the chief line in the spectrum of the nebulas. A reply, 136. and Mrs. Huggins, on Wolf and Rayet's bright-line stars in Cygnus, 33. Hunter (W.) the influence of oxygen on the formation of ptomaines, 376. Ice-crystal, on the plasticity of an (McConnel), 323. India-rubber tubes and balloons, note on the instability of, when distended by fluid pressure (Mallock), 458. Insects, on the minute structure of the muscle-columns or sarcostyles which form the wing muscles of. Prelimi- nary note (Sehafer), 76, 280. Iron and steel, the passive state of. Part II (Andrews), 120. Part III (Andrews), 481. in chromatin, on the demonstra- tion of the presence of, by micro- chemical methods (Macallum), 488. Jackson (William Lawies) elected, 136. admitted, 154. Johnson (G.) on the physiology of asphyxia, and on the anesthetic action of pure nitrogen, 144, Johnson (G. S.) on the bases (organic) in the juice of flesh. Part I, 538. Keeler (J. E.) on the chief line in the spectrum of the nebula;, 399. Kew Observatory, cloud photography conducted under the Meteorological INDEX. XXIX Council at the (Strachey and Whipple) , 467. Larmor (J.) on the theory of electro- dynamics, 521. Lenses and lens-combinations, on the focometry of, and on a new focometer (Thompson), 225. Leon (J. T.), C. R. A. Wright, and C. Thompson, on certain ternary alloys. Part IV. On a method of graphical representation (suggested by Sir GK GL Stokes) of the way in which certain fused mixtures of three metals divide themselves into two different ternary alloys, with further experiments sug- gested thereby, 174. Light, on the reflection and refraction of, at the surface of a magnetised medium (Basset), 76. Limit of visibility of the different rays of the spectrum, on the. Preliminary note (Abney), 509. Liquids, on the effect of temperature upon the refractive index of certain (Cassie), 343. Liveing (Or. D.) and J. Dewar, on the influence of pressure on the spectra of flames, 217. Liver, contribution to the study of the vertebrate (Dele pine), 64. Lockyer (J. N.) on the causes which produce the phenomena of new stars, 443. on the chief line in the spectrum of the nebulae, 136. Love (A. E. H.) note on the present state of the theory of thin elastic shells, 100. Luminous discharge of electricity through a rarefied gas, un the rate of propagation of the (Thomson), 84. Lunt (J.) and Sir H. E. Roscoe, con- tributions to the chemical bacteriology of sewage, 455. Lydekker (R.) on the generic identity of Sceparnodon and Phascolonus, 60. Macallum (A. B.) on the demonstration of the presence of iron in chromatin by micro-chemical methods, 488. McConnel (J. C.) on the plasticity of an ice-crystal, 323. MacWilliarn (J. A.) a new test for albumin and other proteids, 368. Magnetic screening, on variational elec- tric and (Thomson), 418. Magnetism, on the unsymmetrical dis- tribution of terrestrial (Wilde), 120. Malaria, on the demonstration by stain- ing of the pathogenic fungus of, its artificial cultivation, and the results of inoculation of the same (Evans), 199, note on above (Dyer), 539. Mallock (A.) note on the instability of india-rubber tubes and balloons when distended by fluid pressure, 458. some measures of Young's modulus for crystals, &c., 380. Mammalian nervous system, on the ; its functions and their localisation deter- mined by an electrical method. — Croonian lecture (Gotch and Horsley), 235. Marcet (W.) on the chemical phenomena of human respiration while air is being re-breathed in a closed vessel, 103. Marr (John Edward) elected, 491. Marshall (John) obituary notice of, iv. Matthey (E.) further contributions to the metallurgy of bismuth, 78. Metallurgy of bismuth, further contri- butions to the (Matthey), 78. Metals, on certain properties of, con- sidered in relation to the periodic law (Roberts- Austen), 347. Mond (Ludwig) elected, 491. Mummery (J. H.) some points in the structure and development of dentine, 319. Muscle, striped, on the minute struc- ture of, with special reference to a new method of investigation by means of " impress-ions " stamped in col- lodion (Haycraft), 76, 287. Muscle-columns or sarcostyles which form the wing muscles of insects, on the minute structure of the. Pre- liminary note (Schafer), 76, 280. Nebulae, on the chief line in the spec- trum of the (Keeler), 399. (Lockyer), 136. A reply (Huggins), 136. Nervous system, on the mammalian ; its functions and their localisation deter- mined by an electrical method. — Croonian lecture (Q-otch and Horsley), 235. Nitrogen, anaesthetic action of pure (Johnson), 144. Niven (W. D.) on ellipsoidal harmonics, 1. Norman (Rev. A. M.) admitted, 538. Numerical registration of colour, the. Preliminary note (Abney), 227. Obituary notices : — Casey, John, xxiv. Bonders, Frans Cornelis, vii. Ellis, Alexander John, i. Marshall, John, iv. XXX INDEX. Oligochaetous annelid, preliminary notice of a new form of excretory organs in an (Beddard), 308. Paraflinir nitrites, the physiological action of the, considered in connexion with their chemical constitution. Part I. The action of the paraffinic nitrites on blood pressure (Cash and Dunstan),314. Pareiataurut, further observations on (Seeley),518. Parker (W. N.) on the anatomy and physiology of P-rolvptermx annectenx, 549. Passive state of iron and steel, on the (Andrews), 120, 481. Pathogenic fungus of malaria, it.-* artifi- cial cultivation, and the results of inoculation of the same, on the demonstration by staining of the (Evans), 199. note on Dr. Fenton Evans' paper on the (Dyer), 539. Periodic electric currents, on the sensi- tiveness of the bridge method in ite application to (Rayleigh), 203. law, on certain properties of metals , considered in relation to the (Boberts- Austen),347. Perman (E. P.) and W. Bainsay, an attempt to determine the adia but it- relations of ethyl oxide. Part I. Gaseous ether, 447. Person's absolute zero, determinations of the heat capacity and beat of fusion of some substances to test the validity of (Pickering), 11. Phtucolanut and Sceparnodon, on the generic identity of (Lydekker), 60. Photometric observations of the sun and sky (Brennand), 4, 255. Physiological a-iion, contributions to the study of the connexion between chemical constitution and. Part II. (Brunton and Cash), 311. of the paraifiuic nitrites con- sidered in connexiou with their chemical constitution. Part I. The action of the parafiinic nitrites on blood pressure (Cash and Dunstan), 314. Pickering (S. P. IT.) determinations of the heat capacity and heat of fusion of some substances to t . M t he validity of Person's absolute zero, 11. Plasticity of an ice-crystal, on the l.MeConnel), 323. Presents, list of, 53, 73, 80, 117, 127, 133, 150, 200. 233, 24O, 321. 307, U>3, 44-1, 152, 403, 489, 536, 554. Protopttrn* anntcte**, on the anatomy and physiology of (Parker), 549. Pteroplataea micrura, on the uterine villifomi papilla? of, and their relation to the embryo. No. XXII (Wood- Mason and Alcock), 359. Ptomaine?, the influence of oxygen on the formation of (Hunter), 376. Ramsay (W.) some suggestions regard- ing solutions, 305. and E. P. Perman, an attempt to determine the adiubatic relations of ethyl oxide. Part I. Gaseous ether, 447. RAH some (A,) on certain conditions that modify the virulence of the bacillus of tubercle, 66. Rayleigh (Lord) on the sensitiveness of the bridge method in its application to periodic electric currents, 203. Reflection and refraction of light at the surface of a magnetised medium, on the (Basset), 76. Refractive- index of certain liquids, on the effect of temperature- upon the (Cassie), 343. Reptilia, research e»-on» the structure, organisation, and classification of the fossil. VII. Further observations on Pareiasaums (Seeley), 518. Respiration, human, on the chemical phenomena of, while air is being re- breathed in a closed vessel (Marcet), 103. Roberts-Austen (W. C.) on certain properties of metals considered in relation to-the periodic law, 347. Roscoe (Sir H. E ) and J. Lunt, con- tributions to the chemical bacteriology of sewage; 455. Rupture of steel by longitudinal stress, on the (Cams-Wilson), 243. Sampson (R:- A.) -OB Stokes's current function, 46. Saroostyles or muscle-columns which form the wing muscles of insects, on the minute structure of the. Pre- liminary note (Schafer), 76, 280. Sceparnodon- and Phcucolonut, on the generic identity of (Lydekker), 60. Schafer (E. A-.) on the minute struc- ture of the muscle-columns or sarco- styles which form the wing muscles of insects. Preliminary note, 76, 280. on the structure of amoeboid proto- plasm, with a comparison between the nature of the contractile process in amoeboid cells and in muscular INDEX, xxxi tissue, and a suggestion regarding the mechanism of ciliary action, 193. Scotoma (tobacco), on the examination for colour of cases of, and of ab- normal colour blindness (Abnej), 491. Screening, on variational electric and magnetic (Thomson), 418. electrostatic, by gratings, nets, or perforated sheets of conducting material (Thomson), 40*. Seeley (H. G.) researches on the struc- ture, organisation, and classification of the fossil reptilia. VII. Further obseryations on Pareiasaurus (Seeley) , 518. Sensitisers for rays of low ref rangibility, on the bisulphite compounds of alizarin -blue and ccerulin as (Higgs), 345. Sewage, contributions to the chemical bacteriology of (Roscoe and Lunt), 455. Shaw (William Napier) elected, '491. Shells, note on the present state of the theory of thin elastic (Love), 100. Silver, bismuth, and zinc, alloys of, and of bismuth, zinc, and tin (Wright and Thompson), 156. Sky and sun, photometric observations of the (Brennand), 255. Solutions, some suggestions regarding (Ramsay), 305. Spark spectra of the elements, on the physical characters of the lines in the (Hartley), 448. Spectra of flames, on the influence of pressure on the (Liveing and Dewar), 217. of the elements, on the 'physical characters of the lines in the spark (Hartley), 448. Spectrum, on the limit of visibility of the different rays of the. Pre- liminary note (Abney). 509. of the nebulse, on the chief line in the (Keeler), 399. on the chief line in the (Lockyer), 136. on the chief line in the. A reply (Huggins), 136. Stars, on the causes which produce the phenomena of new (Lockyer), 443. in Cygnus, on Wolf and Rayet's bright-line (Huggins and Huggins), 33. Steel, the passive state of iron and. Part II. (Andrews), 120. Part III (Andrews), 481. the rupture of, by longitudinal stress (Carus- Wilson), 243. Stokes (Sir Or. G.) note on a graphical representation of the results of Dr. Alder Wright's experiments on ter- nary alloys, 174. Stokes's current function, on (Sampson), 46. Strachey (R.) and 'Or. M. Whipple, cloud pliot ography conducted under the Mete >rological Council at the Kew Obiervatory, 467. Stress, --the rupture of steel by longi- tudinal (Carus- Wilson), 243. Striped muscle, on the minute structure of, with special reference to a new method of investigation, by means of " impressions " stamped in collodion (Hay craft), 76, 287. Stuart (T. P. A.) a simple mode of demonstrating how the form of the thorax is partly determined by gravi- tation, 143. on a membrane lining the fossa patellaris of the corpus vitreum, 1"7. on the connexion 'between the sus- pensory ligament of the crystalline •dens and the lens capsule, 141. Sulphur, on a determination of the boiling point of, and on a method of standardising phitinum resistance thermometers by reference to it (Callendar and Griffiths), 56. Sumpner (W. E.) and W. E. Ayrton, the measurement of ttie power given bv any electric current to any circuit, 424. •Sun and sky, photometric observations of the (Brennand), 4, 255. Temperature, on the effect of, upon the refractive index of certain liquids (Cassie), 343. Ternary alloys, note on a graphical re- presentation of the results of Dr. Alder Wright's experiments on ternary alloys (Stokes), 174. • on certain. Part III. Alloys of bismuth, zinc, and tin, and of bis- muth, zinc, and silver (Wright and Thompson), 156. ; Part IV. On a method of graphical representation (suggested by Sir G. G. Stokes) of the way in which certain fused mixtures of three metals divide themselves into two different ternary alloys ; with fur- ther experiments suggested thereby (Wright, Thompson, and Leon), 174. Terpenes, camphors, and camphor acids, on the constitution of the (Collie), 554. Terrestrial magnetism, on the un- XXX11 INUKX. symmetrical distributioti of (Wilde). 120. Thermometers, on a determination of tin- boiling point of sulphur, and on a method of standardising platinum resistance (Culleidar and Griffiths), 56. Thompson (C.), J. T. Leon, and C. R. A. Wright, on certain ternary alloys. Part IV. On a method of graphical representation (suggested by Sir O. Q-. Stokes) of the way in which certain fused mixtures of three metals divide themselves into two different ternary alloys ; with further experiments suggested thereby, 174. t and C. R. A. Wright, on certain ternary alloys. Part III. Alloys of bismuth, zinc, and tin. and of bismuth, zinc, and silver, 156. Thompson (Silvanus Phillips) elected, 491. on galvano hysteresis. Prelimi- nary notice, 439. on the focometry of lenses and lens- combinations, and on a new foco- nieter, 225. Thomson (J. J.) on the rate of pro- pagation of the luminous discharge of electricity through a rarefied gas, 81. Thomson (Sir W.) on electrostatic screening by gratings, nets, or per- forated sheets of conducting material, 405. on variational electric and magnetic screening, 418. Thorax, a simple mode of demonstrating how the form of the, is partly deter- mined by gravitation (Stuart), 143. Tidal prediction, on. — Bakerian lecture (Darwin), 130. Tin, zinc, and bismuth, alloys of, and of bismuth, zinc, and silver (Wright and Thompson), 156. Tizard (Thomas Henry) elected, 491. Tobacco scotoma, on the examination for colour of cases of, and of ab- normal colour blindness (Abney), 491. Tubercle, on certain conditions that modify the virulence of the bacillus of (Ransorae), 66. Uterine villiform papillae of Pteraplataa mlcrnra and their relation to the embryo, on th* fWood-Mason and Alcock). No. XXII, 869. Vertebrate liver, contribution to the study of the (I)elepine), 04. Vice-1're.sidenta, appointment of, 1. Whipple (G. M.) and R. Strachey, cloud photography conducted under the Meteorological Council at the Kew Observatory, 467. Wilde (H.) on the unsymmetrical di»- tribution of terrestrial magnetism, 120. Williamson (W. C.) on the organisation of the fossil plants of the coal- measures. Part XVIII, 154. Wing muscle* of insects, on the minute structure of the muscle-columns or sareostyles which form the. Pre- liminary note (Schafer), 76, 280. Wolf and Ravel's bright-line stars in Cygnua, on (Iluggins and Hug gins), 33. Wood-Mason (J.) and A. Alcock, on the uterine villiform p.-ipilhe of Ptero- platcea mierura, and their relation to the embryo, being natural history notes from II M. Indian Marine Survey steamer " Investigator," No. XXI I, 359. Wright (C. R. A.) and C. Thompson, on certain ternary alloys. Part III. Alloys of bismuth, zinc and tin, and ' of bismuth, zinc, and silver, 156. C. Thompson, and J. T. Leon, on certain ternary alloys. Part IV. On a method of graphical representa- tion (suggested by Sir GK O. Stokes) of the way in which certain fused mixtures of three metals divide them- selves into two different ternary alloys ; with further experiment* suggested thereby, 174. Wright's (Dr. Alder) experiments on ternary alloys, note on a graphical representation of the result* of (Stokes), 174. Young's modulus for crystal*, some measures of (Mallock), 380. Zinc, bismuth, and tin, alloys of, and of bismuth, zinc, and silver (Wright and Tnompson), 156. END OF FORTT-N1NTH VOLUME. UARU180N AWI> SOX8, PKINTKKS IK OBDIKAUY TO 11KB MAJESTY. ST.MAETlM's LA>F. Royal Society of London Proceedings I&90-3I "•47 Physical A Applied Sci. Serials PLEASE DO NOT REMOVE CARDS OR SLIPS FROM THIS POCKET UNIVERSITY OF TORONTO LIBRARY