MS f Py - - Vos =) Bp a 2. Copyright No. shelf KS hie x oe Wi eh iy i Pe tiene Mio Te | ee ee Re ha, A = > A TEXT BOOK OF THE Piay oles. OF AGRICULTURE BY FH. RING Professor of Agrieultural Physics in the University of Wisconsin ” Author of ‘The Soil;”’ “Irrigation and Drainage;’’ ‘‘ Principles and Movements of Ground Water” MADISON, WIs. PUBLISHED BY THE AUTHOR 1900 All rights reserved 91150 Libracy of Cong lwo Coees RECEWED DEC 201900 Lewes f 7494 COPYRIGHT, 1899 Biv ey GEL NIG PREFACE. The great need of agricultural practices at the present time is a keener appreciation and a more thorough com- prehension of the principles which underlie them. The facts of agriculture are spread through so many and widely different fields, and are so numerous, that no one can hope to grasp them all or needs to do so. But the laws and principles which control his practice each farmer must know before he can secure his results with the greatest cer- tainty and at the least cost. In these pages the aim has been to present to the student who expects to be a farmer, some of the fundamental prin- ciples he must understand to become successful. They are presented from the standpoint of physics rather than of chemistry or of biology, and in dealing with the physical side of the problems the burden of effort has been to lead the student to see wuy he should practice more than WHAT, and it is hoped the student will pursue the various subjects treated in this spirit, not only in his study, but above all on the farm and in the field. The book in its present form is not complete in either of its sections, but has been put together to meet the imme- diate needs of classes. KK. oH. Kine University of Wisconsin, Madison, Wis., Dec. 5, 1900. CONTENTS: INTRODUCTION. PAGE. MEAT TUR: AND! JHORGH..: ive cjtiatacecce assiwie, ovokcte seis) o nile ersi ele cieie shoversuen svanoharer etek 6 MOLD CULARY CONS RUM G ETON OM BOD TES 2,5 ra cece, sree, ck ave dn euher ds sae ie Gaete 6 Distance between molecules, p. 7; Motions, p. 8; Size, p. 9; Rela- tion to fertilizers, p. 11; to poisons, p. 12; to odors, p. 13. iow ODORS AND FLAVORS FiInpD THEIR WAY INTO MILK.............. Enter during secretion of milk, p. 14; Influenced by feed, p. 15; From the air, p. 15; Introduced with solids, p. 16; Developed after drawn, p. 16. DEODORIZING MILK VV UGS FE Sa roe on Suc Pe ey arene ve Iai) Sacha Noes USSU) Steal iciran ove eneuastte Calle ieia achat orchens is speualereua ae! Conservation, p. 19; Source of the earth’s energy, p. 20; Solar energy, p. 20; Hlow it reaches the earth, p. 21; Amount, p. 22; Rate of transmission, p. 28; Kinds of waves, p. 23; Evapora- tion of water, p. 24; Chemical changes produced, p. 24. NATURE OK HEAT AND COLD TEMPERATURE Measurement, p. 25; Accuracy of thermometers, p. 26. NITES SOA OR Ke CARN EINER GW) 5.5 8 5)o05.5 coli ane oie alates 0) sl pie See tiels, o Siute Shs ceterere Foot-pound and foot-ton, p. 27; Horse-power, p. 27; Unit of leat, p. 28. SSEEE) GM CMAUNID) SICGAUT ENTS EM HTAUID Syovtaus ave foviazeraier ict telayetats aveteve(aieterse lonatel © ’eraravar crete Melting of ice, p. 31; Evaporation of water, p. 31. ee ee ey PHYSICS OF THE SOIL. CHAPTER I. NATURE, ORIGIN AND WASTE OF SOIL. NOUMSEFAN DI SUB SOLE Srasde-tonenevelat sta ois a a sacveie sieve ckerotaretelavel a eueteva swale) eleie. wis SH SROME SOL craeretciens ce bre c enerev here ticke. chcine a eks ee Meuepeateteielecsvenstonel'ss) sac auras HO RAEAT ON (ORME S OMT sca cesta te pena ceare or acne le averercheteis eke intete ereneisiaveys evel soveuous, « Influence of rock texture, p. 51; Rock fissures, p. 53; Running water, p. 54; Glaciers, p. 51; Humus soil, p. 61; Wind-formed, p. 63; Animals, p. 64. 14 16 18 19 25 25 CHAPTER II. CHEMICAL AND MINERAL NATURE OF SOILS. PAGE. ESSHNITAL) CONSDITUNNIS OF A MiRrran Solu... sss see neneeeeoene 69 HUNCLIONS OF SSENDIAT IPVANT HOODS: eos oaoleee eee 70 CHOHMICAT ACOMPOSTTION Oke SOLES sa Seine eine eee ieiene Be Oso dia iG AP (al Difference between clayey and sandy, p. 71; Differences due to texture, p. 72; Between soils and subsoils, p. 72; Between clay and humus, p. 73; Between clay and loess, p. 73; Between arid and humid, p. 73; between soil and rock, p. 77 Humuwus See a reece Rica EAH Ghee CaE MC tenctsr Srs ERS Go. re rr ai fants os Poulsen go pedanrtoe ae rene aaa: Of arid and humid climates, p. 76. AND MOOD a. tceierr ie eeieolectiavc ces ASIC Es ieee ha ES Renae Eero een 79 Amount removed from soil by crops, p. 79; Amount in soil, p. 79; Number of crops produced, p. SO; Rothamstead experiments, Dp: Sie SENGETA IG GEREN TiN LEM EY 9S Oa rsics a yrag ae eer ore eBoy ca PLT OT TR eI ete eee 82 Amount in Manitoba soils, p. 82; Forms of occurrence, p. 83; Dis- tribution in soil, p. 88; Amount as nitric acid, p. 84. SOURCHS circle cecj pcre share ole ole Dapeiay tate eae LO Soil texture and tilth, p. 231; Importance of good tilth, p. 233. How TEXTURE AND TILTH ARH DEVPLOPED............. Aolifaes mole cestarsies AS PAR The uses of harrows, p. 234; The planker, p..236; The roller, p. 237: The plow. p. 238: How may puddle soils, p. 289; May correct texture and improve tilth, p. 239. onside (ata MeWOh isi peas Gea EU OB ICminob CbRGu S.cmee OIG Cireeno Oru OIOKC, Orn - 209 Must be adapted to the soil, p. 240; Sod plow, p. 241; Pulverizing plow, p. 242; Mellow soil plow, p. 242. TDeAuy ninco ial MOS oo BORD eMb OOD BAURO UO COTS UDO COLO COIS DU ia nCrCiaicac 243 English and American trials, p. 248; Draft of sod plow with and without coulter, p. 243; Sod compared with stubble plow, p. 244- Influence of moisture on draft, p. 244; Draft of sulky plow, p. 245; Line of draft, p. 246: Scouring of plows, p. 247. UAEEN IY OTT MTEC reve arches eke cae cic ete eras abe exesichsleuwteuslsFaleln! «| eigveieieisis egeueuera 247 When not in use, p. 247; Keeping in form, p. 247. ESO) BAL O)\\ ot ep GID IO D.C 0 Cro CHOI ED CeO RO ELHO Ce OIGIIIC OND ECAC SRC rCs ICCA . 250 Ospsects. METHODS AND TIMES OF PLOWING.......-++ ee esse ee eee wee 200 Depth of plowing, p. 250; Best condition of soil for, p. 251; Treat- ment after plowing, p. 252; Plowing for corn in the fall, p. 252: Plowing sod, p. 252: Plowing under manure, p. 253 ; Plow- ing under green manure, p. 253; Early fall plowing, p. 254. GROUND WATER, WELLS AND FARM DRAINAGE. CEVAR EIR = SXqene MOVEMENTS OF GROUND WATER. AMOUNT STORED IN GRroUND. LL AE er aia. Gis crc ole a.Geolb Ground water surface, p. 258; Seepage, p, 258; Growth of streams, p. 259; Rise of ground water through precipitation, p. 260; Law of flow through sands, p. 262; Calculation of flow, Dp. 262: Observed and computed flow, p. 264; Relation of rate of flow to diameter, p. 266; Relation of pressure to flow, p. 266; Observed rates of flow in sand and rock, p. 268; General movements across wide areas, p. 270. FLUCTUATIONS IN THE RATE OF FLOW OF GROUND WATER Due to barometric changes, p. 270; In springs, p. 270; In rate of discharge from tile drains, p. 271; Change of level in wells, p. 272; Due to changes in soil temperature, p. 271. CHAR TAR Xone FARM WELLS. BSSHNITATL. KH PAPURES OWUN "GOOD MWEN Lin -iy cise oles credo e eee toietons eeoiaens Capacity, p. 275; Best geological conditions, p. 276; Depth, p. 283. CONDITIONS INFLUENCING CAPACITY Size of grains and pore space, p. 276; Depth in water-bearing beds, p. 278; Pressure, p. 279; Diameter of well, p. 279. USB (OR! SSA GS THRANIES SS cl cer cucue: eee caucttceeaue tee cor cuettene faite det ohel cay uetnewegietelst cn eMeN Capacity, p. 281; Compared with open well, p. 282. TLE MRE RAR UR OR OV RIO HV VOAISIOR terece) sco issaqercithere @eyerehntarekeraGePeUe fe tnyale hen saat Lion or cyan OV ASU orca Gs Jey id Novara ainigmtnciomot ic anita bs EIS. bist aaistordtounte id ao alc CHAPTER XIV. PRINCIPLES OF FARM DRAINAGE. NMCESSTDY OR “TOR AU NAGI. mo oisiciececestolcus Shel - pial 0) siteuslreuaisbeiisbener) ot sueionel eile toner trolls CONDITIONS REQUIRING DRAINAGE AN oygiisin eros IDNYY UNOS Gay GoooGnaEenogabouedn cosconoeacoon aoc dbeat Increases root room, p. 287; Increases available moisture, p. 288 ; Makes soil warmer, p. 288; Better ventilation, p. 290. 4 UC) ORE) B90 IPs Cen BERNICE ne ib oid emo OOD oO Sido MO Oo ac onde woo Sooo Essential features of drain tile, p. 291; How water enters tile, p. 292; Collars, p. 292; Depth laid, p. 292; Distance between tile drains, p. 296. CONFORMATION OF GROUND WATER ABOUT DRAINS..........--++20000- Rise away from drains, p. 298; Observed eal w ater surface, p. 296: Rate of change of surface, p. 297. PAGE. 255 270 286 287 . led 287 290 294 PAGE. MOVEMONG OF WRATNAGE “WATDR: .. 66 cj.6.00 6 ocree vat cie MBs a od when eo 298 Heavy clay underlaid with sand, p. 298; Gradient, p. 298: Silt basin, p. 299; size of tile, p. 299; Practical illustration of sizes and lengths, p. 3801; Outlets, ov. 502; Joining laterals with mains, p. 808; Obstructions, p. 308. OKT ERe MIC Ee GROIN iticyeve cp O nS CRUE CHEAPER EMEC ion den aL ea ee a a 304 LEME A CSET UP TUAT NAGE deca, ote cy oye units vac Pener's, acu oy cock’ iis tone at cae emoun ele een ea icone 306 Construction, p. 806; Intercepting underflow, p. 307; Basins with- out outlets, p. 307. Lands requiring surface drainage, p. 309. CHAPTER XY. PRACTICE OF UNDERDRAINAGHE. MEP ENED IE LINTON Gee a Bila Sate ne avect icherancr SeeNGeas iacal oetmieeenal Gola a oie oa alesis) ePrice 312 Instruments, p. 312: Method of leveling, p. 313; Contour map, p. 315; Locating mains and laterals, p. 315; Determining grade, p. 317: Changing from one grade to another, p. 319. WIGGENG Et SOUL GE. aye, oa recetete tna seues anal ec sieyara hela e ees acctretahatay etre s.. 321 Ditching tools, p. 321; Width of ditch, p. 322: Bringing bottom to grade, p. 322: Placing tile, p. 324; Filling the ditch, p. 328. RURAL ARGHITECTURE. CHAPTER XVI. STRENGTH OF MATERIALS. WOANBENTCUINET OEY PLCC) SS eos alls storey Mec ry was cited nay aie Papetele’ Saad Gy Sue ed oachans, Peeuerene oie 6 Oo Stress, p. 329: White pine pillars, p. 350. ED EARS SE) SUR IN GEILET clea) evey oles essa eiveceus ops Gowers ais, sl dienare & Stduaichana aiteipetieeetarele ote 331 Tensile streneth, nv. 331: Principles. bv. 381: Proportional to squares of depth, p. 882; Relation to length, p. 334; Break- ing constants, p. 335: Computing loads, p. 336; Rafters, p. 337: Safe loads for horizontal beams, p. 337; Selection of lum- ber, p. 338. BARN FRAMES BRS Hci ei CIRO AO ECO HOC ALCL HERO eI. nS Tee HOA OIear 338 Braces, p. 838: Constructing timbers from 2-inch lumber, p. 3359; Forms of frames, p. 339; Plank frame, p. 340; Balloon frame, p. 840; Cylindrical frame, p. 341. CHEAP TERS xovin: WarMtH, Licrr AND VENTILATION. WONTROU. Ol) TRRWALPYIIEAM UR, oiece vara lo ntavase hate falals/ |e) sie) ers) jelais «=| \= info ole «j'a'skaye 343 Normal animal temperatures, p. 343; Best stable temperature, p. 244: Solid masonry walls, p. 346; Hollow masonry walls, p. 247: Brick veneered walls, p. 347; All wood walls, p. 348. PAGE, PAGECIN G PSR Me FR TID TIN G Siovcterere cus ote ec cusret ove cadiciss tem cncler stot a ae ee ee 348 ficiency of windows, p. 348; Position of windows, p. 349. VENTA TTON On ARM ETD TMG Skis ss encive thesis + crater Dabere stay ashe 350 Necessity for ventilation, p. 350; Carbon dioxide, p. 350: Mois- ture from lungs and skin, p. 350: Ammonia and organic mat- ter, D, 501: Micro-organisms and dust, p. 352; Bad ventila- tion predisposes to disease, np. 352 ANOUNTORSATR UB OUMRED ici eks sce five cei lone emi cena e ee ee 353 Amount respired, p. 353: Degree of impurity permissible, p. 354; Rate of supply, p. 354. CONSTRUOMION, OF AVENDIUANORS Actes tustece austere ers tener dire ee oe 355 Capacity of flues, p. 355; Iorces producing ventilation, p. 358; es- sential features, p. 358; Location, p. 359: Place of openings, p. 360; Introduction of fresh air, p. 362; Construction, p. 363; Ventilation of basement stables, p. 364. CHAPTER XVIII. PRINCIPLES OF CONSTRUCTION. REGADION OR COVURING LO SPACHD TINCLOSHD ssa. sn: lsiereeis cle eoeieieinie eine 366 Relation of walls to floor space, p. 366; Relation of hight to ca- pacity, pb. 367; Combined and separate construction, p, 370; Saving of labor, p. 372. SABIE MOTO ORS ciatysrcnoeinahe overs icieters citer ee aers tery cass emcee sec Haytet ce tcil a) sees ne le a ieee 374 Essential features, p. 374; Cold and warm floors, p. 875; Use of bedding, p. 376; Wood floors, p. 377; Making wood floors water- tight, p. 377; Stone floors, p. 878; Macadam floors, p. 378; Macadam for barn yard, p. 379. CONSTRUCTION OF CEMENT FLOORS AND WALKS...............+.0+-- woke Kinds of cement, p. 379; Cement concrete, p. 379; Materials, p. 380: Wetting crushed rock, p. 380; Ratio of ingredients for concrete, p. 381;.For finishing, p. 381; Thickness, p. 382; Making and laying, p. 382. GUAT ET TGs ee ee eee ee eae ee eros ites e Tomncpetie Rens he aas ee eteete owen ces restonen Wao rakenotiers 384 Stanchions, p. 384; Adjustable stalls, p. 385; Movable halter ties, 1 otaltic IN DNS C1) pene te Bea ep a RISO Sec sp Ole Ot Goo Smo OO Ue moln.o med otme to ot aoc 388 WON ph IDOI aoe goon obcomotooooUdL OUndone douoNbO UOC er teheacedciekorsisis 388 TON ESHLOP SIO ANON MOOSE SoA tas dood coon moo ooodaouaouOS Patetorecs O chtun 388 Watering in bain, p. 388; Storing water in tanks, p. 3889; Water- ing trough, p. 390. FAG RU SUN CEI AT ED NUS 0 ETO Te mel ONGC) AUD TON Go Red VAG Yareeeiee es tate taths Peliel te natehic fee tainenal ctletistcieasiicicte 391 CHAPTER XIX. CONSTRUCTION OF SILOS. CONDITIONS ESSENTIAL FOR PRESERVING SILAGE.....................- 394 Depth, p. 394; Rigid walls, p. 394: Protection against frost, p. 396. Xili PAGE CONS TRUCE LOM SOR wy TONEY PLO Sireiore ts cienc cheverelein soit, © MEE ereravene sieve es eheca@tarn vole 397 Laying walls, p. 397; Plastering, p. 398; Doors, p. 399. CONSRRUCLIONS OR VERGE STUO Sis cptcctovw cet eierete, ia) hcl ovevosetonevele. coe o) ocer ela of exeve 400 Foundation, p. 400; Walls, p. 402; Tie-rods, p. 402; Making walls air-tight, p. 402; Doors, p. 403. CONSERUCTION OL BRICK TNE Ds MMO Si 1c areveeie al ela aus. sities dsl aheve st altace « «ie 403 Foundation and sill, p. 405; Setting studding, p. 405; Sheeting, p. 405; Siding, p. 406; Lining, p. 406. IFAT EAD PANT) qc AS TERED) «SLI OS cre eben) omecuetshe olci et sie tekcyer Sie cteccha av oar do ays overavens 407 CONSTRUGLION ORVATTR WOOD ISLUOS setsversive sitteusherscetcser ees: eh oi eheteuete ciate crime che 409 Foundation, p. 409; Cementing bottom, p. 410; Sills and studding, p. 410; Sheeting and siding, p. 412; Plate, p. 413; Lining, p. 413; Roof, p. 417; Ventilation, p. 417: Painting lining, p. 418. SS UAB ORY MPAUNT ISG Ini SSIES Ola ticivcs aipey's dee eoeNeaoke ue merevere neha eeere nel auaerel ee] arta eieiepoin cierecoic 418 Construction, p. 420; Staves, p. 422; Foundation, p. 422; Hoops, p. 422; Doors, p. 4238. DPUESTWGS SHLD G) SSB eat eee fer Si ies o fakccieea rach a ok ome al ue aul ailUrone Stave Ne eee Ors Seyi fone. oh Wikia auagetoravellche 423 DY NMAEN SONG ORME SITIO Syapatrancieaneren cra etot ot kenepen eres e forehronteiear tu cys evoke 500,000, 000 = 5, 120, 000,000,000 molecules. It is plain, therefore, from this straightforward line of observation and simple calculation that molecules of ana- line at least must be very small and that a pound of the material would contain an enormous number. From another line of observation Maxwell has computed that the molecules of hydrogen, oxygen and carbon dioxide are so small that the numbers in the table below are re- quired to weigh one gram. Number of molecules in one gram of Hydrogen Oxygen Carbon dioxide 2, 174(10)?3 1, 359(10)?? 9, 881(10)*1 That is to say, the number of molecules is so large in one gram of these three substances that 2,174, 1,359 and 9,881 11 must be multiplied by 10 used as a factor 25, 22 and 21 times respectively in order to express them. 7. Molecules and Commercial Fertilizers.—It is a very strange fact that 100 to 500 pounds of commercial fertil- izers applied to a poor soil will produce such marked et- feets upon the growth of plants when these small amounts are spread over an acre of ground and then dissolved in and distributed through the soil water of perhaps the en- tire surface four feet. To know, however, that the mole- cules of these fertilizers are so extremely small and that there are such immense numbers of them in a single pound enables the mind to better comprehend how such marked effects are possible. The surface four feet of good field soil when well supplied with moisture may contain the equivalent of 10 inches of water on the level. This amount of water expressed in eubie feet per acre is 36,800. The experiment with an- aline indicates that a single gram has been divided into not less than 5,120,000,000,000 parts. Let us compute how many parts this number would give to each cubic inch of the 36,300 cubic feet of soil-water in the upper four feet of an acre. 5, 120, 000, 000, 000 36,300 « 1,728 = 81,624 We see, then, that a single gram of analine may be di- vided enough to place 81,624 parts in every cubic inch of moisture of an entire acre of good soil to a depth of four feet. But one gram of sodium nitrate would contain, accord- ing to Maxwell’s results, NaNO, :2 O:: No. of O molecules : No. of NaNO, molecules or 85i2.32) 22 1, 359(10)?? : x whence x = 51(10)23 =—5, 100, 000, 000, 000, 000, 000, 000, 000 12 Treating this result as we did that of the analine we shall have 5, 100, 000, 000, 000, 000, 000, 000, 000 36, 300 >< 1,728 = 81,310,000,000,000,000 as the number of molecules of sodium nitrate in each cubie inch of water from which the plants may draw their sup- ply of nitrogen. It will be seen that this number is so large that even a cube of water .01 inch on a side will contain 81,310,000,000, a number far too large for com- prehension: and yet if 200 pounds of sodium nitrate were applied to the acre this number would have to be multiplied by the number of grams in 200 pounds to express the num- ber of molecules there would be for each cube of soil-water one-hundredth of an inch en a side. 8. Molecular Structure in Relation to Poisons—It is the extremely large number of molecules which may exist in a small space, coupled with the energy which these molecules may carry with them in their movements, which makes possible the violent disturbances in the life processes of animals and plants associated with the introduction into the system of such small quantities of substances known as poisons. It will be easily understood from what has been said regarding the vast number of fertilizer molecules per eubie inch of soil moisture, when only a single gram has been disseminated throughout the surface four feet of full acre, that extremely small quantities of any poison, like strychnine, will contain molecules enough to charge the body of the largest animal with great numbers of the poisonous units. The important practical lesson to be remembered in this connection is that, since such extremely small quan- tities of matter, when introduced into the plant or animal body, are sometimes capable of producing such profound disturbances as to cause death, extremely small quantities of other substances may have very important beneficial effects; and it is quite possible that it may be along such 15 lines as these we must search for an explanation of some of the little understood points associated with the nourish- ment of both plants and animals. 9. Ability to Recognize Small Quantities of Matter.— \Ve often marvel at the delicacy of the chemical balance and many other instruments of measurement, but the delicacy of the sense organs of men and animals, and particularly the sense of smell, is so extreme that it is difficult to form a just conception of the minuteness of the quantity of matter or of energy to which they will respond with the degree of intensity which permits accurate Judgments to be formed. The sensations of odors result from the disturbances produced on the organs of smell by molecules of different substances moving through the air when brought to the nose. But when the blind lady took the glove of a stranger and, walking up and down the aisles of a large audience room filled with people, handed the glove to the owner, made known to her only by the likeness of the odor ont the glove to that escaping from the! stranger, who will say what fraction of a gram of that volatile principle it was which produced so marked a sensation? The weight of volatile substance rising into the air from a man’s track, made by a shoe rather than his bare foot, must be very small indeed, and yet the sense of smell in the dog is so keen that he will follow his master at a rapid run even when the tracks are two hours old and where many other people may have passed along the same course more re- cently than did his master. The readiness with which flowers, fruits and vegetables may be identified by their odors alone, often at consider- able distances, and with which animals scent their enemies or their food, are all of them concrete demonstrations at once of the extreme minuteness and vast numbers of mole- cules, while at the same time they prove how sensitive is the animal organization to such minute quantities of ma- terial. 14 10. Foul Odors and Flavors in Dairy Products.—Since the commercial value of dairy products is determined in a high degree by their flavors and odors “and since these qualities are judged through the sense of smell, which we have seen is so extremely delicate and keen, and since such minute quantities of the odor or flavor producing sub- stances are certain to awaken the undesirable impressions, it is clear that the greatest of care must be exercised in producing, handling and caring for them through all the steps preceding the delivery to the consumer. Since we have seen that so little fertilizer may be disseminated through so much soil moisture and since so little may be de- tected by the organs of smell, it is plain that too great care cannot be taken in keeping the milk clean and ‘that only those who do this can hope to secure the custom of people wilhng to pay a high price for the milk, cream, butter or cheese which just suits them. 11. How Odors and Flavors Find Their Way Into Milk.— The substances producing these qualities in nilk make their entrance there in three dient ways: (1) from the blood at the time the milk is secreted; (2) from the outside after the milk is drawn; and (3) they are produced within the milk after it has been secreted before or after it is drawn. 12. Odors Entering Milk During Secretion.— Any volatile principle which may chance to be present in the blood of the animal at the time the milk is being drawn will find its way into the milk and will impart a quality to it, the intensity of the flavor or odor depending upon the amount of the volatile principle present and the readiness with which it evaporates. Nearly all food stuffs contain substances which produce odors and if these substances are not destroyed during the processes of digestion they will again escape from the body of the animal through the channels of excretion; that is, through the skin, kidneys, lungs, rectum or ud der, and if 15 any of these principles still remain im the blood at the time the milk is being drawn they will appear in it. — It follows, therefore, that the longer the interval of time be- tween the taking of food into the body and the drawing of the milk the less danger there will be of the milk be- ing tainted by it. The reason for this is found in the fact that the milk is excreted during the time of milking while the blood is coursing through the udder, carrying whatever odor producing substances may then be present. 13. Time to Feed Odor Producing Foods.—It is clear from what has been said that if it is desired not to have the milk charged with the undigestible odor-principles of food while it is being drawn these foods should be fed as soon as possible after milking and never just before in order that time enough may have elapsed to permit the odor principles to have been eliminated from the blood by the other organs. On the other hand, if the food contains a principle whose odor is desired in the milk, then the re- verse rule as regards time of feeding should be practiced, namely, to feed these just before milking. 14. Introduction of Odors Into Milk From the Air.—]t is the fact that the molecules of substances are not in contact and that they are in motion which makes it possible for milk when in an atmosphere containing odors to become charged with them. If the odors of manure, of urine, of ammonia, or any of those associated with the decay of organic matter are in the air above the milk the rapid motion of these molecules will cause some of them to plunge into the milk and accumulate there until they be- come so numerous that just as many tend to escape per minute as tend to enter. The milk is then saturated with the odor in question. The warmer the air surrounding the milk and the warmer the milk the more quickly will the condition of 16 a! saturation be reached, simply because the rapidity of mo- lecular motion increases with the temperature, for when the molecules of foul odor are once inside the warm milk they travel or diffuse downward more rapidly because it is warm. 15. Odors and Flavors Resulting From the Introduction of Solids Into Milk.—It must be clear from what was demon- strated in (€) that when great care is not taken both in keeping the stable and cows clean and free from dust the fine particles of dirt falling into the milk, even though the amount is small, may readily dissolve and impart a strong flavor to it, and one careless milker may easily ereatly injure the quality of that from the whole herd where all of the milk is pooled. The fundamental point to be kept ever in mind is that a very little dirt is capable of being divided to an extreme degree and that through the senses of taste and smell extremely small amounts may readily be detected. 16. Odors and Flavors Develeped in Milk After It is Drawn.— Milk is a very nutritive fluid and for this rea- son great care must be exercised not only to keep dirt out but also to prevent those germs from entering it which have the power of developing rapidly there, producing un- desirable odors and flavors and thus injuring the quality of the milk. These objectionable germs are lable to be introduced into the milk through the dust from the sta- ble and the cow as well as from the lack of proper cleanh- ness of the vessels in which the milk is handled. 17. Deodorizing Milk.— The removal of odors from milk may be accomplished by greatly increasing its surface in a space containing none of the odors which the milk con- tains. The method known as the “Aeration of Milk” has for its purpose this rather than the exposure of the milk to the air, as the presence of the air hinders the escape of Ke the odors rather than favors it and if the milk could be ex- posed in a vacuum their escape would be more complete and more rapid. The escape of the odors from the milk depends upon the rapid motion of the odor molecules in it which forces them to escape whenever they approach the surface with suffi- cient velocity to overcome the surface attraction, and the division of the milk into a large number of small streams increases the chances for the odors to escape in proportion to the increase of the surface. The finer the milk streams, the farther they are apart and the longer the stream is in falling the more complete will the removal of the odors be. Where there can be a movement of air over the milk surface or among the streams of milk this will favor the removal by carrying the odor molecules away and thus preventing them from re-entering the streams. Since the molecular movement is greater the higher the temperature it follows that the deodorizing process should be apphed as soon after the drawing of the milk as possi- ble before it has had time to cool and the molecular motion to slow down. 18. Place For Using the Deodorizer.—If the aerator or deodorizer is used in the barn or where there are many ob- jectionable odors it must be remembered that exactly the same conditions which favor the escape of the odors which the milk contains when drawn are the best conditions to permit it to become charged with odors from outside, and hence the deodorizer or aerator should be placed where it is surrounded by a current of pure air. 19. Cooling Milk.—The cooling of milk immediately after it is drawn has a powerful influence in preventing odors from developing in it as a result of the growth of any germs which may have found their way into the milk because the low temperature makes their growth much slower. Cooling, then, is not a deodorizing process but one which prevents the formation of new odors. If, then, 18 it is desired to remove the animal odors this if possible should be done first and then the milk cooled to prevent the formation of other odors. 20. Work.—Whenever any body is moved under the ac- tion of a force work is done and the amount of this work is measured by the intensity of the force and the distance through which it has acted. When a body weighing one pound is lifted one foot against the attraction of the earth the amount of work done is one foot-pound. The same weight lifted 10 feet represents 10 foot-pounds and 10 pounds raised one foot has the same value. A team hauling a load over a road under a mean pull of 200 pounds is doing 200 foot-pounds of effective work for every foot trav eled and in traveling 10 miles the total work done is 10 < 5,280 > 200 = 10,560, 000 foot-pounds. When a larger unit than the foot-pound is dene that of the foot-ton may be employed and its value is 2,000 pounds lifted one foot high or 2,000 foot- “pounds. Tf a wagon with its load weistine 4,000 pounds is moved along ‘the road the work done will not be measured by the produet of the load into the distance traveled but by the intensity of the pull necessary to pull the load into the distance trav- eled. On a good level macadam road 60 pounds will move a ton and 120 pounds two tons. To draw four tons over 10 miles of such level road means the doing of 4 60 10 X 5,280 2, 000 = 6, 336 foot-tens. So, too, if the pressure of steam on the head of the piston in a steam engine is 80 pounds per square inch and the area of the piston is 100 square inches the amount of work it can do per foot of stroke is 80 < 100 = 8,000 foot-pounds. 19 If this engine makes 200 strokes per minute, then the work it does per minute will be 200 > 8,000 = 1,600,000 foot-pounds. 21. Energy.—Knergy is the ability of a moving body to do work and the amount of energy the moving body has is measured by the amount of work it can be made to do in coming to rest. If a weight suspended from a string be drawn to one side and then released it will begin fall- ing and acquiring velocity, and on reaching the lowest level it will possess the ability of doing a certain amount of work. That amount will be enough to raise its own weight through the height from which it fell in the same time. If a bow is bent and the string is released against the arrow it will recover its form of rest but in doing so will impart to the arrow an amount of motion equal to that which the bow acquired in straightening out. When work is done in winding the clock the distorted spring has the power to develop an amount of energy equal to that expended in winding it up. In chopping wood the action of the woodsman’s muscles increases the amount of motion in the ax until it falls upon the wood, when the energy which has been imparted to it does the work of cut- ting. We cannot exert pressure enough with the hand alone to force the nail into the board, but by giving the muscles an opportunity to act gradually upon the hammer it is a simple matter to store in it enough energy to easily drive the nail into the wood. When coal or wood is burned in the fire-box of the engine and the heat developed converts water into steam under high pressure in the boiler we have still another case where energy is developed and accumu- lated in the rapidly moving molecules of steam which drive the piston whenever the valves are opened leading to it. 22. Conservation of Energy.—No discovery of modern science is more fundamental than the fact that neither mat- ter nor energy can be destroyed or created. One form 20 of energy may be transformed into another, and one kind of substance may be decomposed and others made from the components, but in these transformations there is neither annihilation nor creation. The small amount of ashes left from the winter’s supply of coal or wood seems to point to a destruction of matter, but their weight added to that of the products which pass up the chimney is even greater than that of the original fuel by the amount of oxy- gen which was required to burn the fuel. So, too, the energy of 10 horses expended in threshing grain seems to be annihilated but it is only transformed. Heat of fric- tion and concussion, sound and material raised into new positions, from which it may fall, when added together will make a sum equal to that develoned by the horses. Again we appear to realize in the increase of cur domestic ani- mals or in milk produced much less weight than has been used by them in feed and drink but this is because such large quantities of the materials eaten, breathed and drank escape 1m an invisible form through the skin and lungs. 23. The Source of the Earth’s Energy.—The real source of the earth’s energy is the sun. All the rivers of the world flowing to the sea and the rush of the winds swaying the tree-tops and lashing the ocean into billows represent so much water and air lifted from a lower to a higher level by the sun’s heat and now being pulled by gravity back to their original level to be raised again and to again re- turn, just as a pendulum rises and falls while swinging through its are. The wood burned in the stove, the coal burned in the en- gine and the food consumed by the horse are all the prod- uct of sunshine which lifted the constituents of soil, moisture and air into such combinations as readily per- mits of their return to other forms, setting free the energy which was consumed in producing them. 24. Solar Energy.—When the sum rises the temperature increases, usually becoming higher and higher until past 21 noon, then when the sun sets the temperature falls again, continuing to do so until once more the sun is above the horizon. So, too, as our days grow longer and longer with the approach of summer in the middle and higher lati- tudes, making more hours of sunshine in every twenty- four, the mean daily temperature increases but falls away again when the nights became longer than the days. Such and many other facts prove the sun to be a source of energy which in some manner is being transferred to our earth. |More than this, since the earth travels entirely around the sun once each year and yet. each day receives heat and light from it, it follows that solar energy is con- tinually leaving the sun in all directions, so that the amount arrested by the earth forms a very small portion of the whole. 25. How Solar Energy Reaches the Earth.—To under- stand how the energy of the sun reaches us, coming across 93,000,000 of miles we must learn that the energy travels in the form of waves through some medium filling space, which has been named ether, but whose real nature is not yet understood. Something similar to the process in question would be represented by a man at the center of a pond throwing its water into waves. These waves would spread in all directions and when reaching the beach a portion of the energy of the waves would be absorbed or transferred to whatever body they chanced to strike. The energy, therefore, generated in the muscles, is changed first into wave energy in the water and conveyed away from the man in all directions, but afterward when arrested at the beach, the waves may move the pebbles, making them grind upon one another, wearing themselves into sand, or their sliding may change a portion of the wave energy inco heat and thus the person in a small degree may warm the pebbles lying on the distant margin of the lake, not di- rectly by the heat of his body, but by the waves set up in 2 22 the water, and much as the earth is warmed by waves sent out through the ether of space from the surface of the sun. The rapid and intense molecular motion at the surface of the sun is transformed into wave motions in the sur- rounding ether of space, as the motions of the imaginary man were changed into waves in the water, and these ether waves travel away from the sun’s surface in all directions at the rate of 186,680 miles per second. So many of these waves as the size of the earth permits it to stop are arrested and transformed into the various forms of motion which are manifested at its surface. 26. Amount of Energy Developed at the Sun’s Surface.— Careful measurements and calculations have shown that the energy developed second by second at the sun’s surface, amounts, according to Lord Kelvin, to not less than 153,000 horse power on each square meter or 1.09 square yards of its surface. 27. Rate at Which Solar Energy Reaches the Earth’s Surface.— As the intense energy developed at the surface of the sun spreads away from it, it becomes weaker and weaker in the ratio that the square of the distance of the waves from the sun increases, as represented in Fig. 2, and Fia. 2. so at the earth’s surface the amount of energy has become so much reduced that Lord Kelvin places it at only a little more than 1.3 horse power per each square yard of surface. 23 But small as this amount of energy is when compared with that leaving a like area at the sun’s surface it is neverthe- less very large. It may seem strange that so much energy falling upon the earth does not keep its surface at a higher temperature than is observed, but when it is stated that the temperature of the space which surrounds the earth outside its atmos- phere is —273° C. and that only the thin atmosphere shields the surface from this intense cold, it is plain that a large amount of heat must be required to hold the mean temperature even as high as 45° IF. which is 273° + 7° = 280° C above absolute zero. If we add to the necessity of holding the earth’s surface at a temperature 280° C. to 300° C. above the space in which it moves, the demand for energy needed to maintain the movements of water and of winds, together with that em- bodied in activities of animal and plant hfe, then 1.5 horse power per square yard of surface does not appear so much too large. 28. Kinds of Ether Waves.—The energy reaching the earth from the sun.in the form of wave motion is not all alike in that the waves have different lengths, or, what is the same thing, greater numbers of one kind reach the earth in a unit of time. Waves which are so frequent that from 392 to 757 billions reach us per second produce the sensation of light when falling upon the eye; the slower ones producing red light and the more rapid ones the ex- treme violet colors of the rainbow. Associated with these color waves there are many other dark waves to which the human eye is not sensitive. Some of these are much shorter than the color waves and are especially powerful in breaking down the molecular structure of different sub- stances; that is, in producing chemical changes such as oc- cur on the photographer’s plate when the negative is made andsuch as take place in the green parts of plants when ear- 24: bon dioxide is broken down and the chemical changes are produced which result in building the sugars, starches and cellulose of plants. Others of these waves are much longer than the light waves and these have a wonderful power in producing heating effects when they fall upon certain sub- stances, one of which is water. When bright sunshine is allowed to pass through a large lens the glass is but little warmed by the passage, -but if paper is held at the light focus it is quickly set on fire by the dark or invisible rays. That it is the dark rays may be proved by allowing the light to pass first through a solution of iodine in bisulphide of carbon which permits the dark waves to easily pass while it cuts down or stops the light waves. When these dark waves are brought to a focus in water it is made to boil quickly under their in- fluence. On the other hand if sunlight is first passed through a solution of alum in water, which stops the dark waves but allows the light waves to pass, then when they are focused upon water but little heating effect is noted. 29. How Water is Evaporated. It is the fact that water does not allow the long dark waves from the sun to pass readily through it which causes it to evaporate so rapidly from ocean, lakes and streams, and from the soil and the leaves of vegetation. When these waves fall upon water they set its molecules in such rapid vibration that the sur- face tension, or force of cohesion, is overcome and many of the water molecules are thrown out into the air in the form of invisible vapor. Were the water not so opaque to the dark waves, neither snow nor ice would be as rapidly melted in the spring nor would there be so much evapora- tion from the ocean as we now have, hence rains would be less frequent and the land less productive. 30. How Chemical Changes Are Produced by Ether Waves.—When the light waves and especially the shorter dark waves fall upon many substances they appear to set. 25 up vibrations within the molecules themselves, which in time may become so intense as to overcome the force by which the components are bound together and the molecule is thrown into parts, setting them free so that when their motion slows down they may join in new combinations. It is much as if some giant power were to seize upon a steel chain, throwing it into such intense vibrations that its sev- eral links are broken. 31. Nature of Heat and Cold.—When a body becomes warm the rate of vibration of the molecules which compose if is increased and the path through which they move becomes longer. If the body becomes cold the rate of movement of the molecules becomes less rapid and the dis- tance through which they move less. The higher the rate of molecular motion within a given body the warmer that body is and vice versa. If the molecular motion of a body could be completely brought to rest its temperature would be absolute zero. Under this condition it is supposed that any body would have its smallest volume; and all liquids and gases would become solid. 32. Temperature.—When the temperature of a body is given it is intended to state the degree of molecular vibra- tion within it. The temperature at which a Fahrenheit thermometer marks zero is not that of no molecular motion but simply 32 degrees of that scale slower than the rate at which pure water becomes a solid; while zero indicated by a Centigrade thermometer is the rate of molecular motion which permits water to become solid and is a temperature 273 degrees above what is assumed to be absolute zero or the condition of absolute rest. 33. How Temperature is Measured.—It is a general law that those substances which may exist as solids, as liquids or as gases, as is the case with water, which we know as ice, water and steam, or invisible vapor, change from the solid to the liquid form and from the liquid to the gaseous form when the rate of molecular motion has reached a certain 26 degree, and this being true the freezing and boiling points of various substances may be taken as standards of tem- perature. Water being a common substance which changes its state at convenient and common rates of molecular motion has been selected to fix two degrees of temperature called the freezing and boiling points of water. When a thermom- eter scale is to be graduated its bulb is placed under the in- fluence of melting or freezing water, and the place at which the moving point comes to rest marked; then it is placed under the conditions of boiling water and the new point also marked. The space between these two points on the seale is then divided into 80, 100 or 180 divisions, accord- ing to the system which it is designed to follow. Since this range in molecular vibration is divided into 180 degrees on the Fahrenheit scale its degrees are the shortest, while those of the Reaumer seale are the longest because the same range is divided into but 80 divisions. The Centigrade and the Fahrenheit scales are the two commonly used in this country, the degree of the former being equal to @ of the latter. 34. Accuracy of Thermometers.—The bulbs of most ther- mometers shrink after they are blown and if they have not been permitted to stand for a number of years to season before fixing the zero and boiling points of the scale, these points will change and the thermometer will give incorrect readings in time and the cheaper grades of thermometers are liable to be subject to this error. The accuracy of the freezing point may be approxi- mately tested by surrounding the bulb with snow or erushed ice out of which the melted water may drain, al- lowing the thermometer to remain until the temperature becomes stationary. The accuracy of the boiling point may also be approxi- mately determined by holding the bulb in rapidly boiling soft water. 27 A thermometer may be correct at the freezing and boil- ing points and inaccurate at most intervening degrees, growing out of the sores diameter of the tube in differ- ent portions and the fact that all degree marks may be made of the same length. Errors of this sort can be de- tected only by comparing the thermometer with a standard. 35. Units of Work and Energy.—It has been found neces- sary in dealing with the numerical relations of work and energy to adopt standards of measurement just as has been done for lengths, volumes, surfaces and mass, and various units are in use. 36. Foot-pound and Foot-ton.—A common unit of work is the foot-pound, which is a mass or weight of one pound lifted vertically against or in opposition to the force of gravity. Tf a body is moved one foot in any other direction than against the force of eravity and the intensity of the pull or push necessary to do this is equal to that required to lift one pound, then in this case the work done is one foot- pound. If 2,000 pounds is lifted one foot high then 2,000 foot-pounds of work have been done, and this is sometimes designated a foot-ton. The same intensity of pull in any other direction may be expressed in the same terms. Time is not a factor taken into account in simply ex- pressing the amount of work done for the reason that a very small foree when permitted to act for a very long time may raise the same weight through one foot, which would require a very intense force if permitted to act but a very short time. 37. Horse-power.— When the rate at which work is done and the intensity of the force required to do the work at the stated rate are to be expressed quantitively, then a unit involving time must be chosen and the horse-power is one of these. The horse-power used by English and American engineers is the amount of energy which ean do 550 foot-pounds of work per second or 33,000 foot- 28 pounds per minute, equal to 16.5 foot-tons in the same time. To raise grain in an elevator to a hight of 20 feet at the rate of 16.5 tons per minute would require 20 horse power. If a horse is walking 2.5 miles per hour and exerting a steady pull on his traces of 100 pounds then the effective energy he is developing is 100 X 5, 280 2.5 60 >< 60 9< 550 = ANE AP: and this for a well fed horse weighing 1,000 pounds, work- ing 10 hours per day at the rate of 2.5 miles per hour, is called a fair day’s work. If a 1,500-pound horse could do work in proportion to his weight then his ability to de- velop energy would be equal to the standard English horse- power of 550 foot-pounds per second. Gen. Morin, how- ever, has placed the ability of the average horse to do work at the rate of 435.5 foot-pounds per second. 38. Heat Unit.—In the steam engine the energy of heat is converted into work, and since heat is a form of moleecu- lar motion its quantity must have a fixed relation to the temperature of a given amount of material. The English and American heat unit is the amount of heat energy which is required to raise the temperature of one pound of pure water from 32° F. to 33° F., and since one form of energy may be converted into another the value of a heat unit may be expressed in foot-pounds. The English scientist, Joul, was the first to measure the number of foot-pounds of work which one heat unit could do and found it to be 772, which when corrected for the mercurial thermometer became at 15° C. 775 foot-pounds. Rowland obtained the value 778.3 foot-pounds. This means that the source of heat which is able to raise the temperature of one pound of water one degree every second would also be able to raise 778.3 pounds one foot high in the same time. 39. Determination of the Mechanical Equivalent of Heat. —JIn order to ascertain the value of the heat unit in foot- 29 pounds, Joul arranged a vessel containing water in such a way that by means of nicely adjusted weights he could cause them to drive a set of paddles in the water and by the mechanical agitation warm it. By knowing the number of pounds in his weights, the distance they were allowed to fall and the rise in temperature which was observed in a given weight of water, he found the relation to be that stated in (38). 40. Specific Heat.—We have learned (82) that tempera- ture is a measure of the rate of molecular motion within a given body; it is not, however, a measure of the amount of work which must be done upon that body to change its temperature through a given number of degrees ; neither is it a measure of the amount of work which may be secured from that body when its temperature falls a given amount. When the same number of heat units is imparted to like weights of different substances their temperatures are not raised through an equal number of degrees. |The same amount of heat, for example, which will raise the tempera- ture of one pound of water from 32° F. to 33° F. will raise a pound of sand from 32° F. to 37.23° F. For some reason more work must be done on water than on the sand to secure the same change of temperature, but, true to the law of the conservation of energy, when the water again cools down if gives out as much more heat in doing so as was required to produce the rise in temperature. It is this fact which causes large bodies of water to make the winters of adjacent lands warmer and the summers cooler. Soils change in temperature more rapidly than would be the case were their specific heats higher, and for this rea- son in part a wet soil is cooler than the same soil when dryer. 41. Latent Heat.—When ice at 32° F. has heat applied to it its temperature does not rise so long as there is still ice to melt, the whole of the energy given to it being con- sumed in changing the solid ice into liquid water, that is, 30 in doing the work of melting. The amount of heat re- quired to melt one pound of ice is 142 units when ex- pressed in round numbers ; or if the work done is expressed in foot-pounds it will be 142 & 778.3 = 110,518.6 foot-pounds and the time required for one horse power to do the work would be 110,518 .6 ~ 33,000 _ = 3.35 minutes. When crushed ice and salt are mixed in the ice-cream freezer the changing of the two solids to a liquid requires so much energy, and it is used so rapidly, that the cream is. quickly frozen, its molecular motion being used in doing the work. When water has been brought to the boiling tempera- ture it ceases to become warmer so long as boiling contin- ues, all of the heat energy entering from the fire being re- quired to do the work of changing liquid water into steam. The amount of heat required to change one pound of water at 212° IF. into steam at the same temperature is 966.6 heat units. When expressed in foot-pounds it becomes 778.3 >< 966.6 = 752,305 and the time required for one horse-power to do this work is 60 52 5B = 22.8 minutes. When a pound of water at 32° F. becomes ice at 32° F. there reappears as heat the 142 heat units which were re- quired to melt it, and so toc when one pound of steam con- denses into water there reappears 966.6 heat units. Be fore the nature of these changes were as well understood as ol they now are, it was supposed that the heat became hidden or datent but that it was heat still. 42. Measuring the Energy Required to Melt Ice.—This may be determined approximately by taking equal weights of water at 212° F. and of ice at 32° F., putting the two together and noting the temperature at the moment the ice is all melted. When this has been done it will be found that the combined water has a temperature of about 51° F. If, however, equal weights of water at 52° and 212° are mixed there will be found a temperature of 212 32 a Sie one volume of water having lost as much as the other gained. In the first case, however, the water lost 212 — 51 = 161 while the ice gained only oat, There was therefore in this case an apparent loss of 161 — 19 = 142° If a pound of water and of ice had been taken for these ex- periments it is plain from (88) that the 142 would also represent 142 heat units. 43. Measuring the Energy Required to Evaporate Water. —If a pound of steam at 212° F. be condensed within 5.37 pounds of water at 32° F. there will result 6.37 pounds of water having a temperature very close to 212° F. The one pound of steam has therefore raised the temperature of 5.37 pounds of water through o2 212° — 32° = 180° without having its temperature materially lowered. The molecular energy, therefore, which the one pound of steam contained was 180 >< 5.37 = 966.6 units. This large amount of energy in steam explains how it is able to do so much work when acting upon the engine pis- ton and why a burn from steam may be so much more se- vere than that from boiling water. 49 PHYSICS OF THE SOIL. CHAPTER Tf. NATURE, ORIGIN AND WASTE OF SOIL. 64. Nature of the Soil.—The great bulk of most soils is made up of small fragments of rock of various kinds, but nearly always there is associated with these varying amounts of organic matter derived from the breaking down of plant and animal tissue. On the surface of the soil grains, too, there is always ad- hering more or less of substances which have been dis- solved in the soil-water but which have been deposited again when the water was evaporated. In most soils, but chiefly in the clayey types, there oce- curs some aluminium silicate having water combined with it, which is regarded as giving to them their sticky, plastic quality when wet. The amount of this material in a good soil is always small, seldom reaching more than 1.5 per cent., but the particles are so extremely minute that very little by weight has a marked effect upon its character. 65. Soils and Sub-soils.—In climates where the rainfall is sufficient for large crops it is common to speak of the sur- face few inches of rock fragments as the soi! while that below is known as the sub-soil. |The fundamental reason for making this distinction is found in the fact that the latter is less productive than the surface soil. So general is this difference in fertility that the term ‘‘dead-furrow” has been universally applied to the finishing of a land in plowing where the two furrows are thrown in opposite 50 directions, leaving the sub-soil exposed, and where crops are always smaller. On the other hand, where two fur- rows are thrown together to form the “back-furrow” and the depth of soil increased crops are notably more vigorous. We do not yet know just why a sub-soil when exposed to the surface is less productive than the true soil, but the difference seems in some way to be associated with the larger per cent. of the extremely minute particles which sub-soils contain. In arid regions where the rainfall is not sufficient for crop production it seldom oceurs that the deeper soil is markedly different in productiveness from that at the sur- face. Soil taken from the bottom of cellars and even from depths as great as 30 feet is found quite as productive when placed upon the surface as the top soil. So gener- ally true is this that when it is desirable to level fields for purposes of irrigation in arid climates the soil from the higher places may be scraped to the lower levels without fear of lessening the productiveness of the fields. 66. Uses of Soil.—In the agricultural sense the most im- portant use of soil is to act as a storehouse of moisture for the use of plants; and the productiveness of any soil is in a very large degree determined by the amount it can hold, by the manner in which it is held and by the readiness and completeness with which the plant growing in it is able to withdraw that water for its use as needed. In the second place, the soil is a storehouse from which plants derive the ash ingredients of their food, the lime, the potash, phosphoric acid and other materials of this class, all of which are derived from the slow decay and solution of the soil grains. Besides these the soil is a laboratory in which a great variety of microscopic forms of life are at work during the warm portions of the year, breaking down the dead organic matter of the soil, converting it into nitric acid and other forms available to higher plants; and the student must never forget that the magnitude of the crop taken pv 51 from the field is always in proportion to the size of the crop developed by the micro-organisms in the soil. Then again, the soil is a medium in which plants may place their roots in such a manner as to enable them to stand erect in the open sunshine and moving air currents above. Finally, the soil is a means whereby the sunshine is changed into fornis of energy available to the needs of soil organisms and the roots of plants and without which this life could not exist; for all of its movements must originate primarily from the sunshine altered in the soil or in the tis- sues of the plant above the soil. 67. Formation of Soil.— There are many agencies at work in the formation of soils and the processes of soil growth are in continuous operation day and night, winter and sum- mer. Since all soil material originates from the breaking down of the various rock structures which make up the earth’s surface all of the agencies which are operative in rock destruction may also contribute to soil formation. 68. Influence of Rock Texture on Soil Formation.— Nearly all kinds of rock are made up of fragments or crystals of various sizes and shapes and these are held together by in- terlocking, by some cementing material, or else by direct cohesion when extreme pressure has brought the grains close enough together to make this possible. It is seldom true, however, that the structure 1s so close or the cement- ing so complete as to make the rock impervious to water and the closest granite or the finest marble may absorb as much as .1 to .4 of a-pound of water to 100 pounds of rock. If this water is changing it will dissolve away the cementing materials and the faces of the erystals them- selves, making the rock still more open and the grains may even fall apart as is frequently observed in those cases known as “rotten stones.” The water may freeze in the stone and by its expansion cause it to crumble. Or again, when the sun shines on 52 rocks made up of minerals of different kinds the erystals do not all expand at the same rate and this unequal expan- sion and contraction tends to loosen crystals and fragments, breaking the rock down, and thus form soil. P Bes =I > eee tS See eas ees = aS Sea ee ee —=a: a = = 25 SSeS ae Fig. 8.— Section of limestone hill showing rock changing to soil. (After Chamberlin.) 69. Formation of Soil From Limestone.—If one will visit any limestone quarry where the soil and rock are exposed in section as represented in Figs. 8 and 9 it will be clearly seen how the rock is slowly converted into soil. In such cases as these, the water containing carbonic or other acids dissolves away the lime and magnesia, leaving the more insoluble portions of the lime rock to form the soil mantle which is left. These more insoluble portions are usually clay and very fine sand so that soils formed in this way are oftenest clayey soils, sometimes containing even less lime than other soils not derived from limestone. Fic. 9.—Section of flat limestone surface showing rock changing to soil. (After Chamberlin. ) The mantle of soil seen above gravel beds in railroad cuts and where hills have been graded down on wagon roads has usually most of it originated from the decomposition of the gravel in place in the same manner as a soil from the limestone itself. So, too, in countries where granite and other crystalline rocks he beneath the soil, these have been broken down and ——— ae ee eras the over-lying soil de- rived from them. 70. Influence of Rock Fissures.— An exainina- tion of almost any quar- ry where considerable surfaces are exposed re- veals the presence of systems of fissures which divide the stone layers into blocks of various sizes and at the same time provide easy ave- nues for the entrance of surtace waters. These features are shown ;32s% clearly in igs. 10, 11, Fie 3.— Fort Danger, Wis., showing rock fis- 19 and 13, Sad) eae puro which lead to rock desc:uction. (After them the roots of trees sometimes make their way where by expansion, dueto growth, such strong pressures are devoloped as sometimes to throw down large blocks — of stone. Then again, in eold climates these fis- sures may become filled with water which, when freezing, overturns and throws down many frag- ments, thus hastening their passage into soil. 71. Soil Removal.—It follows from what has been said that the same ; processes which result in Fic. 4.— Bee Bluff, Wis., showing rock fissures : 4 : which lead to rock destruction. (After S¢ il formation. must also Chamberlin.) : : contribute to its destruc- D4 tion in one place or re- moval to another. All are familiar with the creeping of soils from the brows of steep hill- sides toward their bases and out upon the more level plains.; which stretch away from them. These downward move- ments are caused by sev- eral agencies: (1) The beating of falling rain- drops and the carrying power of the streamlets which form as_ these gather together; (2) the expansion and contrac- tion of the soil due to the alternate wetting i ie and drying, there being Fie. 12.—Giant’s Castle, near Camp Dove es Wis. Bei ceric clitfs of rock crumbling into less resistance to expan- — soil.’ (After Chamberlin.) sion downward than upward against gravity. These movements are analogous to those of the steel rails of the railroad which tend to creep down grade under the influence of changing temperature, which causes them to first lengthen and push down hill and then shorten and again draw downward because of less resistance in that direction. (3) Then, again, every disturbance of the soil produced by animals burrowing or walking up or down the hillside. tends usually to work the soil from higher to lower levels. Even the action of the wind is on the whole downward. 72. Soils Produced by Running Water.—Rivers and streams are continually at work at this double process of soil building and soit removal. When one watches the bed of a stream as the water ripples over the uneven surface 55 it is easy to note how rapidly soil and sand grains are be- ing rolled and tumbled along the bottom. If it is desired to measure this rate of movement a shallow pan or box may be sunk in the bed of the stream, leaving its rim flush with the surface over which the water rolls. After a sufficient in- terval remove the box and dry and weigh the material collected. At each bend in a stream soil is being taken from the con- eave side and carried onward toward the sea, while on the op- posite side new soil is being formed from that dragged along the bottom. In this MaMmoer Sstreanvs change their courses sil oe ‘ee ee al Fie.13 — Pillar Rock, Wis.. showing rocky cliff and Wander Trom side in the last stages of decay. (After Chamber- to side across the val 1) ley, each time making a new soil on the side from which they are retreating and carrying away an older soil from the encroaching side. It is in this way that broad and flat river valleys are formed, with their terraces, such as are shown in Fig. 14. It is in this way, too, that the ‘‘ox- bows” of the Mississippi below Vicksburg were formed, some of which are represented in Fig. 15. These abandoned river channels are at first long and narrow lakes but ultimately, with the repeated overflows of the stream, they became filled. Sometimes they remain for long intervals depressions in which swamp or humus soils develop. pe Fic. 14.—Showing the windings of a stream, the formation of broad valleys and river terraces. Madison River Valley, Montana. NY Ny Se v NWI hiy, iW! ans SSS Fia. 15.— Showirg the shifting of river channels, the formation of ‘ ox-bo ws’ and alluvial soils. 73. Glacial Soils.—In those portions of the world where the temperature is so low that most of the moisture falls as snow and where these snows do not all melt during the warm season there come to be such vast accumulations that the great weight compresses the snow into ice. So ex- tensive and massive are these snow and ice fields in Green- Showing a terminal moraine near?Eagle, Wis. Eire? 16:— Section of a terminal moraine near Fig. 17.—Showing how glacial action has broken, ground up and accumulated rock fragments. 5 Whitewater, Wis. 60 land and in parts of Alaska today that they move over the face of the country much as a ‘broad river would move, except at a much slower rate. The same type of phenom- ena occur, too, in the elevated mountain districts of Europe and in the Sierras of this country, the ice streams con- verging and flowing into the lower valleys im the form of vlaciers. As these ice streams move over the uneven sur- face of their valleys and crowd against their sides, the rocks, gravel and sand taken up by the moving ice act with ereat effectiveness to abraid into soil the rigid rock surfaces over which they move. gia. 18.—Showing rock surface over which glaciers have passed, scratching and polishing it. In a recent geological epoch the whole of the North American ecntinent north of the Ohio and Missouri rivers and much of northern Europe and Siberia were under enor- mous moving ice sheets which resulted in the formation of the extensive glacial soils of these countries; consisting largely of a roe k flour ground to varying degrees of fine- ness, and naturally very fertile where the materials have not been sorted by the waters from the melting ice in such a way as to form siliceous sandy plains. Figs. 16, 17, 18 and 19 are views illustrating different phases of soil forma- tion by glacial action. Fic. 19.— Relief Map of Wisconsin, showing the difference in topography of a glaciated and non-glaciated surface, 74. Formation of Humus Soils.—There is a class of soils having their origin in various types of swamps or marshes which contain an unusual amount of organic matter im va- rious stages of decomposition and which have by some writers been given the name of humus or swamp soils, the former name referring to the large amount of humus these soils contain and the latter to the physical conditions under which they have been formed. In many places in the higher latitudes and at consider- able elevations nearer the equator where the surface is too flat for ready drainage, and where the winter snows re- main so long upon the ground that the summer is too short 62 to permit the soil to become dry enough to allow the air to penetrate deeply and freely, the organic matter accu- mulates and soils are formed containing a large proportion of humus; even beds of peat may develop. Fie. 20.— Showing a method of formation of peat marshes and swamp soils about lakes. Under other conditions, where rivers ap- proach their outlet across a very flat country and are no longer able to scour their chan- nels and keep them clean, the moving sedi- ment finally raises the banks and the bed un- til the water is flowing above the surround- ing country. Under these conditions with a continual seepage and frequent overflows swamps are developed in which marsh vege- tation grows luxuriantly and, falling under conditions where free oxidation cannot oc- cur, the remains only partially decay, giving rise to beds of peat and rich humus soils. In other cases, where a river often shifts its course and especially where the cut-offs or ox-bows illustrated in Fig. 15 are formed, these places, with the poor drainage which they must have and with the occasional over- flows to keep the cut-offs filled with water, are maintained wet long and continuously enough to allow humus soils to form. With the final withdrawal of the great ice sheet from the glaciated parts of America and Kurope there were left large numbers of shallow lakes whose flat margins were wet enough to support marsh vegetation and very often this vegetation came to form a floating fringe steadily encroaching upon the lake in the manner represented in Fig. 20. As the vegetation continued to grow and die the fringe became heavier and sank more deeply in the water until finally the whole lake was overgrown and until the organic matter, together with the sediments brought down by the rains and the winds and washed in from the surrounding higher land, became so heavy and so thick as to rest upon the bottom of the lake, converting it into a marsh of peat or humus soil. On the margins of larger lakes and — especially along the seashore, sand bars or reefs are thrown up behind which 2) bodies of water are shut off and in these organic matter may accumulate in the same manner as that just de- seribed, giving rise to the same type of soils. In still other cases, on the margins of the sea bottom, there flourishes a pe- culiar type of vegetation known as eel grass, which lives always beneath the water at low tide in a position repre- sented in Fig. 21. These grasses offer a natural obstruction to the coming and. outgoing tidal waters, causing them to throw down their sediments and thus build up the sea floor with silt containing large amounts of or- ganic matter under conditions unfay- orable to rapid decay. As the sea floor rises in this way above low tide level the eel grass dies and another type of swamp vegetation takes its place, as between a and b in the figure, and here again the formation of humus soil is continued under somewhat different conditions. 75. Wind-Formed Soils.—The wind moving continuously over the face of the land is now and long has been a potent factor in soil removal and soil building. Indeed, it is probable that nowhere can soils be found which do not contain many wind-borne particles. Every raindrop which falls and every snowflake, however white, brings to the field upon "BOS OY} JO SIOP.10q ot} UO S[IOS SnUINY JO TOTFBUILOF JO OpoUl B SUIMOYS —TZ “OLA 64 which it falls one or more particles of soil which has been drifting in the higher air from unknown distances. The dr ifting Lf dust from roads during dry times and from fields in the spring are strong reminders of the po- tency of wind action at times, but it is the less evident but continuous action that counts most in the long run and, were it not for the steady wearing away and rear rrangement of the soil surface, w ind-formed soils would be much more evident and gener ral than they are. On the leeward margins of arid regions and on sandy coasts the building and eroding power of the wind becomes most evident, and the most extensive deposits which have been assigned to this cause are the loess beds of China which have great horizontal extent and in some _ places depths reaching even 1,200 and 2,000 feet. These depos- its have been described by Richthofen as having been formed from dust accumulations drifted by the prevailing winds from the high desert plateaus of Central Asia. In Europe, and in this country in the Mississippi val- ley, there are deposits of a similar character. They are distributed along the border of a former ice sheet of the glacial period and from thence they spread down the main streams, along the Mississippi from Minnesota to near the Gulf, along the Missouri from Dakota to its mouth, and along both the Illinois and the Wabash. These deposits are thickest, most typical and coarsest along the bluffs nearest to the streams and they thin out and become finer as the distance back increases. It is thought that the fine silts borne along by the waters of the elaci al streams im times of high water were spread out over broad flats and as the waters withdrew they were left to dry in the sun and then picked up by the winds and drifted away. The loess soils are almost always extremely fertile and very en- during. 76. The Work of Animals as Soil Producers.— There are many animals which have contributed largely to the forma- tion of soil through a grinding of pebbles and the coarser sand and soil grains into finer materials. 65 Darwin, through a long and careful study, reached the conclusion that in many parts of England earthworms pass more than 10 tons of dry earth per acre through thei» bodies annually and that the grains of sand and bits of flint in these earths are partly worn to fine silt by the muscu- lar action of the gizzards of these animals. Their method of action in moving through the soil is this: They eat a narrow hole, swallowing the earth, when the point of the head is held fast in the excavation while an enlarged por- tion of the esophagus or swallow is drawn forward, fore: ing the cheeks outward in all directions, thus crowding the soil aside and making the opening wider, when more dirt is eaten and the operation repeated, allowing the animal to advance through the soil. Domestic fowls and all seed-eating birds, in picking up pebbles for service in grinding their food, do the same sort of work as the earth- worms in producing fine soil, as every housewife can testify from the worn condi- tion of bits of glass and pottery taken from the gizzard of the chicken. | 77. Soil Convection.— There is another very important line of work done by earthworms, ants and all burrowing animals, in bringing the sub-soil to the sur- face and carrying the surface soil into the eround, thus maintain- ing a sort of soil-con- La. — reetic thie 1 ,f{_Fic. 23.— A tower-like casting ejected by a spe- vection W hic h, In ¢ t cies of earthworm, from the Botanic Garden, feet. amounts to the Calcutta, India. Natural size from photo. ? - (After Darwin.) le night after gasing fain. the work of the common earth worm durin a heavy ing Fic. 23.—Show 67 same thing as plowing except that its influence extends much deeper. Both earthworms and ants often burrow in the ground to a depth of four feet, and in some cases more than nine, bringing the material to the surface and forming passage- ways down which the rains may wash the finer surface soil. Fig. 22 shows a single pile of earth cast wp by an earthworm in the Botanic Gardens of Caleutta, and Fig. 23 shows the work of our common earthworm during a single night in bringing up soil after a rain. TUNA N Wn eadrabay S cine Ki IN NA) i ne ah ae iy Fic. 24.— Section of vegetable mould in a field drained and reclaimed 15 years before; showing turf, vegetable moulds without stones, mould with frag- ments of burnt marl, coal cinders and quartz pebbles buried under the influence of earthworms. One-third natural size. (After Darwin.) This frequent bringing of earth to the surface tends to bury objects and gradually to lower them into the ground, and Fig. 24 represents the results of one of Darwin’s studies, showing the amount of soil which has accumu- 68 lated above bits of burnt marl, cinders and pebbles dur- ing 15 years, largely through this action of earthworms and ants in bringing to the surface portions of the sub- soil. It will be seen that the amount accumulated is more than three inches, or at the rate of an inch in 5 years. CHAPTER. Ef. CHEMICAL AND MINERAL NATURE OF SOILS. 78. Unsatisfactory State of Present Knowledge.—It is now pretty generally conceded that the capacity of a soil to feed crops of a given kind cannot be foretold with much certainty from the results of chemical analyses as it has been the custom to make and present them. It has been found, for example, in the arid west, that soils nota- bly deficient in humic nitrogen and which for this reason should be comparatively unproductive, have, nevertheless, been found capable of giving large yields when irrigated. Then again, in moist climates there are types of soil ex- ceptionally rich in both humic and nitric nitrogen which are comparatively unproductive until they are given dressings of coarse farmyard manure. The analyst would place them among the richest of soils and yet they are among the poorest until given farmyard manure; and, what appears stranger still, straw and coarse litter may be much more beneficial to them than liquids from the sta- ble cistern. 79. Essential Constituents of a Fertile Soil While it is true that our chemical knowledge of soils is very unsatis- factory, it has nevertheless been thoroughly established that a fertile soil must contain certain substances in order to permit any crop to come to maturity upon it and these are potassium, calcium, magnesium, phosphorus, sulphur, iron, nitrogen and probably chlorine. Let any one of these ele- ments be absent from a soil, or its moisture, and crops fail to develop upon it. It has not, however, been established yet in what form of combination these elements must or may exist nor in what proportions to give the best results. It is known that they do not exist in the soil in the elementary form and that they are combined in a great variety of ways. 70 Furthermore, from these combinations, under favorable conditions, plants are able to supply their needs. 80. Functions of the Essential Plant Foods.— from the standpoint of plant physiology it is again unfortunate that little has yet been positively demonstrated regarding the part played by each of the essential elements of plant food taken through the soil and soil moisture. It is known that nitrogen is an essential constituent of the protein com- pounds of living tissues, and that to most of the cultivated crops it becomes available in the form of nitrie acid or of a nitrate of lime, magnesia, potash or some other base. Po- tassium does not appear as an essential ingredient of plant tissues or of its storage products like starch or gluten, but Nobbe, Schroeder and Erdmann have shown that when Japanese buckwheat, placed in nutritive solutions en- tirely free from potash salts, after a few weeks’ growth came to a standstill and that all organs of the plant came to be nearly or quite free from starch; but when a potas- sium salt was added to the solution starch began to develop and growth became normal. In regard to phosphorus the clearest mdications go to suggest that it is usually taken into the plant in the torm of phosphates and, because its compounds are often asso- ciated with the soluble albuminoids, that it assists In some way in the transfer of these from place to place in the plant. Some compound of iron must exist in soil solutions and must enter the plant before the normal development of the green coloring matter, chlorophyll, can take place; so ex tremely small quantities, however, are needed that no soil is ever lacking in sufficient available forms. Sulphur is apparently largely if not wholly taken into. the plant in the form of sulphates, and these are thought to. be decomposed by the oxahe acid, setting the sulphuric acid free, which is then broken down and the sulphur appro- priated to enter as an essential constituent of the albumin- oid compounds. But little is known of the part played in plant life by 71 the salts of magnesia except that they must be present in the seed. The action of lime is held to be medicinal, its function being to neutralize the poisonous oxalic acid liberated as an intermediate product in the oxidation of carbohydrates. Large amounts of silica and alumina and_ smaller amounts of many other substances are found in the ash of plants but their presence there is regarded as accidental, growing out of the simple fact that they chanced to be dis- solved in the soil-water and passed into the tissues with it during growth. 81. Chemical Composition of Soils—From what has been said regarding the origin of soils and the manner in which their particles have been moved from place to place, it is evident that there must necessarily be a strong similarity among them, of both chemical and mineral composition, wherever found. It has been customary in analyzing soils to digest a certain weight of dry soil for a stated time ina certain strength of hot hy drochlorie acid and to examine the solution for the compounds it might contain, calling the part not dissolved the isoluble residue. The tables on pages 74-75 show the results of some of these analyses, taken from the papers of Hilgard in the Tenth Census of the United States. 82. Chemical Difference Between Clayey and Sandy Soils. —Studying the table of clayey and sandy soils it will be noted that out of every 100 pounds of the clayey soil there were, as an average, 31.791 pounds which dissolved in hot hydrochloric acid, while only 6.79 pounds were soluble in like weight of the sandy soil. In other words, a quarter of the weight of the clayey soils more than of the sandy soils is soluble in a unit of time in hot hydrochloric acid. There is about 2.5 times as much potash and organic matter, nearly twice as much phosphoric acid, 7 times as much lime, 9 times as much magnesia and 1.4 times as much sulphurie acid in the clayey as in the sandy soil, which may be dissolved out in equal times by the solvent used. These ratios, however, are sometimes a long ways from 72 true when single cases are compared, and this is shown in a striking manner in the single case of clay soil given below the line of averages in the table of sandy and clayey soils. This is described by Hilgard as a fair upland soil yielding 700 to 800 pounds of cotton per acre, gray in color, not heavy, 6 to 8 inches deep, and underlaid by a subsoil quite heavy in tillage and dark orange in color; and yet its im- soluble residue is about 91 per cent. and there are two of the sandy soils where the per cents. are 90 and 92 respec- tively, showing ihat the two are more nearly alike chemi- eally than they are physically. 83, Observed Chemical Differences, Partly Due to Differ- ences in Amount of Soil Surface.—It is a common experience that the more finely a substance is subdivided the more rapidly will it dissolve. Fine salt and powdered sugar, for example, dissolve much more rapidly in water than the coarser grained varieties do. In the clay soils the particles have a much smaller diameter than they do in the sandy soils and hence the number of grains in a given weight of soil will be much larger, but the number of grains cannot be increased without also increasing the surface upon which the solvent may act, and hence with the same strength and amount of acid, for equal weights of the coarse and fine grained soil, having exactly the same chemical composition, there should be dissolved in equal times a larger per cent. of the soil having the largest amount of sur- face. The sandy soils therefore are not likely to be as dif- ferent from the clayey ones as the table of analyses indi- cate. 84. The Chemical Differences Between Soils and Their Subsoils.—In humid climates there is usually a marked dif- ference in the producing capacity of the soils and their sub- soils as was pointed out in (65), and a study of the table of subsoils, pp. 74, 75, will show that there is a chemical difference also. It will be seen that the surface soils con- tain more lime, phosphoric acid and organic matter, less soluble silica, alumina and iron and about the same amounts of potash, magnesia and sulphuric acid, lor) (oO 85. Comparison Between Clay Soils and Swamp Soils.—If a comparison is made between the clayey soils, which are generally productive naturally, and the humus soils it will be seen that the latter contain about twice as much potash, magnesia, sulphuric acid and organic matter, six times as much lime and a little more phosphoric acid, and yet for some reason the humus soils, when well drained, may not naturally be as productive as the clay soils are and here is where the present methods of soil analysis fail to tell the whole truth. 86. Comparison Between Clayey Soils and Loess Soils.— The loess soils do not show a much larger percentage amount of the essential ingredients of plant food than do the clayey ones. Indeed there is less of organic matter and only a little more of potash, phosphorie and sulphuric acids. The chief and great difference lies in the large amount of lime and magnesia which they contain, the first bemg more than 9, and the latter more than 8 times as large. If it is true that these soils are largely wind-formed it is to be ex- pected that these two substances would appear at the sur- face to be taken up by the winds more than any other of the essential ingredients, first, because they are comparatively soluble and hence likely to be brought up by the capillary waters and left after evaporation where the wind has free aecess to them; and second, because they are not so soluble as to be completely dissolved by the heavy rains and car- ried back into the ground again. 87. Difference Between Arid and Humid Soils.—The soils which have aceumulated in the arid climates of the world are quite markedly different from those of the more humid portions, both in physical and chemical properties. The per cents. given in the table of arid and humid soils are those of Hilgard and are averages of 466 analyses from hu- mid climates and 313 from arid. Tt will be seen that the arid soils contain more than 3 times as much potash, nearly 13 times as much lime and 6 74 Chemical composition of soils. Essential ingredients in per cent. of dry soil. PHOSPHOR-| SULPHURIC WATER POTASH. LiME. MAGNESIA.| yo Acrp. ACID. AND ORGANIC MATTER. Sand.|Clay.|Sand.|Clay.|/Sand.|Clay.|Sand.|Clay.| Sand. | Clay. | Sand. | Clay. .100 | .416 | .120 | .080 | .040 | .691 | .051 | .103 | .028 -061 2.055 | 1.906 .156 | .176 | .081 | -690 | .069 |} .112 | .101 | .071 | .057 055 2.642 | 8.891 .045 | .186 | .064 | .071 | .005 | .065 | .066 | .204 | .O91 285 2.422 | 8.953 -117 | .134 | .058 | .219 | .042 | .289 | .092 | .069 | .058 035 1.807 | 8.309 -110 | .242 | .090 | .387 | .025 | .508 | .191 | .O71 105 -055 3.47 6.8435 .067 | .092 | .119 | .036 | .090 | .070 | .111 | .082 | .054 054 2.881 | 6.167 .275 | .431 | .055 | .540 | .048 | .836 | .105 | .187 | .034 009 3.682 | 6.922 .095 |1.104 | .076 |1.349 | .083 |1.665 | .039 | .304 | .045 024 2.354 | 7.369 -209 | .150 | .241 |3.054 | .031 | .029 | .103 | .242 | .046 -089 3.113 | 4.962 .034 | .255 | .045 | .340 | .043 | .296 | .014 | .079 | .035 079 1.636 | 4.962 -639 | .435 | 3.786) 5.820) .886 | 3.692] .150 | .200 148 .090 | 13.943 | 1.205 SOILS COMPARED WITH THEIR SUB-SOILS. SOILS. Sand.|Clay.|Sand |Clay.|Sand.|Clay.|Sand./Clay | Sand. | Clay. | Sand. | Clay. 157 | .214 | .115 | 1.761) .076 | .182 | .128 | .207 052 -090 2.853 | 6.014 SUB-SOILS. 143] .344| .096/ 1.481) .073) .240) .124) .159) .060 O71 1.943 | 4.7 | | | + .014|—.130)-+-.019|-+- .280/+- .003]/—.058|+-.004£/+-.018)—.008 |+.019 | +.910 |+1.234 ARID AND HUMID SOILS COMPARED. Hu- -, | Hu- «4 | Hu- P Hu- . Hu- . Hu- . maids Arid. wat Arid. aL Arid. ah Arid. . Arid. val. Arid. -216 | .729 | .108 |1.362 225 |1.411 113 | 117 | .052 O41 3.644 | 4.945 odie io Chemical composition of soils. Inert ingredients in per cent. of dry soil. | ) Brown INSOLUBLE SOLUBLE S OXIDE OF | PEROXIDE ODA. : ALUMINA. RESIDUE. SILICA. MAN- oF Tron. GANESE. Sand. | Clay. |Sand| Clay. ;Sand |Clay |Sand |Clay.|Sand |Clay.| Sand. |Clay. 93.630 | 72.746 | 1.682) 8.926 | .060 | .112 | .102 | .106 | .761 |12.406|] 1.532 | 2.473 94.770 | 73.690 | .486) 3.370 | .069 | .004 | .156 | .146 | .706 | 5.989) .733 | 7 305 93.362 | 60.370 | 1.721; 2.000 | .018 } .119 | .220 | .196 | .941 | 9.709) 1.339 |18 066 95.630 | 73.422 | .879) 2.709 | .064 |trace| .049 | .164 | .224 | 4.054) .473 |10.598 92.090 | 63.444 | 1.220} 11.325 | .035 | .079 | .126 | .052 | .S63 | 3.894) 1.959 [13.454 90.230 | 77.860 | 1.940) 1 790! .009 | .O41 !_.313 | .056 (1.927 | 5.646) 2.141 | 7.538 90.681 | 54.565 | 1.885) 13 219 | .130 | .277 | .172 | .079 |1.837 | 7.089) 1.436 |16.071 92.460 | 51.063 | 1.550) 20.704 | .036 | .325 | .0410 ' .119 | .843 | 5.818] 2.649 !10.539 94.428 | 79.580 | .529) 3.628 | .069 | .065 | .101 | .195 | .661 | 3.420) 1.195 | 4.988 94.822 | 75.350 | 1.037) 7.310 | .022 | .258 | .020 | .038 | .930 | 5.784) 1.576 | 5.567 “93.210 | 68.209 | 1.293) 7.498 | .051 | .128 | .130 | .115 | .979 | 6.381| 1.503 | 9.660 91.498 1.722 054 066 1.372 1.522 SWAMP AND LOESS SOILS. Hu > Hu- Hu- Hu- fail lhe t aes Loess. nee Loess. ane ee Fa, Loess Hu- loess mige Loess 35.886 | 65.853 |20.825) 4.918 | .109 | 165 .164 |7.040 | 3.569] 14.476 | 2.812 SOILS COMPARED WITH THEIR SUB-SOILS. SOILS. Sand. | Clay. | Sand} Clay. | Sand Ictay. | Sand Clay. Sand|Clay. Sand.|Clay. | | 124 | 93.222 | 73.978 |1.019 | 5.034 | .672 | .085 -133 1.162 | 5.205) 1.145 | 6.998 SUB-SOILS. —— 714 | 66.290 | 2.212 7.446 | .064 | .085 | .080 | .125 |1.739 | 6.947) 2.276 |12.086 +2. 12.508 aa: 688. -1.193] —2.412 H- Bai -000 +.014 .044)-+- .008|—.577|-1.742|—1.131 |-5.088 ARID AND HUMID SOILS COMPARED. Arid. 84.031 | 70.565 4.212 7.266 | .091 | .264 | .183 | .059 | 3.131 5.782 4.296 | 7.888 76 times as much magnesia as do the humid soils with which they have been compared. They also contain some more of each of the other essential plant foods except sulphur, the sulphuric acid being less. If, however, a comparison is made between the arid soils and the mean of the 10 clay soils given in the first table, it will be seen that, excepting potash, lime and magnesia, these contain more of the essential ingredients of plant food than do the arid soils, and so, too, there is more solu- ble siliea. 88. Humus.—It is this product in the soil which gives to it usually its dark color, but so far as its chemical composi- tion is concerned its nature is not yet well understood. It is a very important ingredient of fertile soils and is the product of dec: aying organic matter. In torrid climates where the soil is warm the whole year and in arid regions where the soil is more open on account of deficient moisture as well as on sandy soils wherever found, the rate of complete decay is so rapid that the amount of humus is generally relatively small; but in tem- perate climates, where the soil is damp, its texture close and rains frequent, the organic matter decays more slowly and the amount of humus in the soil is relatively greater. The great importance of humus in agricultur al soils is found in the fact that it is relatively insoluble under good field conditions and does not leach away and im this form becomes the food of niter-forming germs which convert it by degrees into nitric acid, as one of their waste products, but the essential form of nitrogen for the food of most higher plants. A soil entirely devoid of humus must neces- sarily be manured or given nitrogen in some other form in order to make it fertile. 89. Difference Between the Humus of Arid and Humid Cli- mates.—Hilgard and Jaffa have made the important dis- covery that the humus of arid soils is relatively richer in nitrogen than is that of humid soils and hence that smaller Loge amounts of it will meet the needs of niter-forming germs and thus allow large crops to be produced where, with a poor form of humus, this would be impossible. The results of their studies in this line are stated in the table below: No. of | Humus in| Nitrogen BP ess samples. soil. in humus. Boule Per cent. | Percent. | Per cent. PATTOUSOMS2 a ctaens: dettesa ee nine! sia/e eis sceistess 18 oy fs) 15.87 101 DOTA ALIGISOWS.acrciccisicwics ote. nisoleiecis 8 .99 10.03 -102 PEM TG SOUS hora ote sevsscteleinkvicie shee ets letete 8 3.04 5.24 132 In speaking of these results they say, “It thus appears that, on the average, the humus of the arid soils contains three times as much nitrogen as that of the humid, that in the extreme cases the nitrogen percentages in the arid hu- mus actually exceeds that of the albuminoid eroup, the flesh- -forming substances.” “Tt thus becomes intelligible that in the arid region a humus percentage, which, under humid conditions, would justly be considered entirely inadequate for the success of normal crops, may, nevertheless, suftice even for the more exacting crops. This is more clearly seen on inspection of the figures in the third column, which represent the product resulting from the multiplication of the humus percentages of the soil into the nitrogen of the humus.” 90. Chemical Composition of Soils Compared With the Rock from Which They Are Derived. a soil accumu- lates in place from slow decomposition of the underlying rock there is sometimes a close resemblance in chemical composition between the rock and the derived soil, but in other cases there is little resemblance between them. If the rock is made up of a large percentage of relatively solu- ble materials, as is the ease with most limestones, then the solvent power of water, combined with the effects of leach- ing, tend to cause a concentration of the relatively insoluble 78 ingredients, thus giving rise to a soil very different in chem- ical composition from the parent rock. If, on the other hand, the rock is made up of minerals of nearly equal solubilities, or if in any way the soil results from a mechanical breaking up of the rock, then the soil may have much the same relative amounts of ingredients as the parent rock shows. In the table which follows are given the composition of some rocks and of soils derived directly from them: Composition of rocks and residual soils.> TRENTON || BERMUDA || Gyurss, GRANITE, || DIORITE. LIMESTONE)| LIMESTONE Rock} Soil.|| Rock} Soil.|) Rock| Soil.|| Rock} Soil.|| Rozk| Soil. Pr ct.|Prct.||Prct.|Pr ct.||Pr ct./Pr ct.||Prct.|Prct.||Prct.|Pr ct. Silica (SiOz) ....) .44 | 43.07)| .052/45.16 || 60.69) 45.31)] 69.33/65.69 || 46.75] 42.44 Alumina (Al2Og)| .042| 25.07]| 0.54 |15.473}| 16.89] 26.55|| 14.33/15.28 || 17.61) 25.51 HerricvoxiGer se .|(encses DO AG I Re rcranets 13.898] 9.16) 12.18] 3.60] 4.39 || 16.79] 19.20 Lime (CaO) ost 34.77 0.63)/54.496) 3.948]| 4.44) tr. 3.21) 2.63 9.46) 0.37 Magnesia (MgO) | tr. 0.03} 1.751) 0.539!) 1.06) 0.40) 2.44) 2.64 5.12) 0.21 Potash (K2O)...jnotd.| 2.50)| 0.066) 0.133]| 4.25! 1.10]} 2.67] 2.00 0.55) 0.49 Soda (Na2Q)..../notd.| 1.20} 0.252] 0.007|| 2.42) 0.22]| 2.70) 2.12 2.56| 0.56 Carbon dioxide..|42.72 | tr. |/44.251| 2.533/]...... (OXO.0 Ge Sical lgaerice 0.00) 0.00 Led evo saris WSOPE ete. lea bo.callllacoaenrilasoaosiilscnsos 0.47)| 0.10) 0.06 0.25) 0.29 Water and vola- tile products ..| 1.03 | 12.98|} .328/18.265 .62} 13.75}| 11.22] 4.70 0.92) 10.92 The two limestones, it will be seen, have given rise to a soil containing almost as much silica, alumina and iron oxide combined as is contained in the three soils from the other three kinds of rock, the per cents. standing, in round numbers, 83, 75, 84, 85 and 87. In other words there is a strong tendency to bring all soils approximately to one composition. Indeed it may be said that in any soil the essential ingredients of plant food make up but from 3 to 8 per cent. of the total dry weight. It will be observed that in the case of the soil derived from the Bermuda lime- stone, not less than 98 pounds of every 100 pounds of rock 1Rocks, Rock Weathering and Soils. Merrill. 19 are dissolved and carried away by the water for each 2 pounds of soil formed, the chief materials carried away being the lime, magnesia and earbon dioxide. co) ? S 91. Amount of Essential Plant Food Removed from the Soil by Crops.—It is very important, in the management of soils, to know something of the draught upon them which crops of different kinds make, and in the table which fol- lows is given the amount of materials removed from the soil in 1,000 pounds of fresh or air-dried product. Table of amount of plant food in 1000 lbs. of air-dried product. . (WOLFF. ) Mazze.|| Oars, || WINT’R]| SPRING|} WINT’R||Bapripy|| RED " * || WHEAT]! WHEAT]|| Rye. CLOVER Pla E SE S| EEE ae] ai 2] 4 Ss os = CI Sy 3 He a & ne} Hs es] HS a pPotaleashen as. sa. 45 .3)12.4)/61.6/26.7//46.0/16.8]|38.1/18.3 Sele 45 .9)/22 .3]/E7.6/38.3 Potash (K20O) ...}16.4) 3.7]/16.3) 4.8}) 6.3] 5.2//11.6] 5.6)| 8.6] 5.8//10.7| 4.7//18.6]13.5 Soda (Naz2O) ...| .5} 0.1}/ 2.0] 1.0}| 0.6} 0.3}/ 1.0] 0.3}] 0.7] 0.3}| 1.6) 0.5}] 1.1] 0.4 Magnesia (MgO) | 2.6] 1.9]} 2.3) 1.9]} 1.1] 2.0]| 0.9} 2.2]| 1.2] 2.0] £.2] 2.0]] 6.3] 4.9 Lime (CaO)..... 4,9) 0.3}| 4.3) 1.0}| 2.7] 0.5]} 2.6) 0.5)]| 3.1] O 5)! 3 3} 0.6}/20.1) 2.5 Phos. acid (P2O35)| 3.8] 5.7|| 2 8] 6.8]] 2.2] 7.9]| 2.0) 9.0] 2.5) 8.5]| 1.9] 7.8]| 5.6)14.5 Sul. acid (SO3)..| 2.4] 0.1]] 2.0) 0.5]| 1.1] 0.1]} 1.2] 0.2]] 1.6] 0.2]| 1.8] 0.4]| 1.9] 0.9 SiwiSol ate psees sees BP lll karl Te al] Ite Tt les salleamo lll) sg) alee abeey) bez uh Po ais Nitrogen... .:.... 4.8]16.0}| 5.6/17.6)| 4.8/20.8]| 5.6/20.5]| 4.0/17.6]| 6.4/16.0/|19.7/30.5 From this table it appears that each ton of clover hay withdraws from the soil 39.4 lbs. of nitrogen; 37.2 Ibs. of potash ; 12.6 lbs. of magnesia; 40.2 lbs. of lime; 11.2 Ibs. of phosphoric acid; and 14.2 Ibs of sulphurie acid, making an ageregate of ash ingredients alone of 154.8 lbs. 92. Amount of Plant Food in an Acre-foot of Soil.—If we take 4,000,000 pounds as the dry weight of an acre-foot of all soils, except the humus and that at 2,000,000 (149), and the percentages of essential plant food given in the tables on pages 74 and 75, the amount of plant food per acre-foot may then be computed, giving the results in the table below: 80 Table giving the tons of essential plant food per acre-foot of different types of soil. Sandy soil.| Clay soil. | Loess soil. Pings Tons. Tons. Tons. Tons. BotashsGs O)neecriccses sacs cece 2.42 6.38 8.70 6.39 hime (CaO) Rereeeceacm arere sae 1.70 12.34 116.40 37.86 Magnesia (MeO) iiehecccccien shea .96 9.12 73.84 8.68 Phosphoric acid (P2O5)........... 1.74 2.82 4.00 1.50 Sulphuric acid (SQg).............. 1.10 1.50 1.80 1.48 From this table it appears that the amount of plant food per acre-foot of field soils, not including nitrogen, ranges from about 2 to 8 tons of potash, 2 to 116 tons of lime, 1 to 75 tons of magnesia, 2 to 4 tons of phosphoric acid, and 1 to 2 tons of sulphurie acid. 93. Number of Crops Required to Remove the Plant Food of an Acre-foot of Soil—The ratio of dry weight of the ker- nels to that of the straw and chaff in a crop of wheat has been found to be as 1 to 1.1 in a dry season, but to be as high as 1 to 1.5 when there has not been an undesirable stimulation to the growth of straw. Taking this ratio of 1 to 1.5, a yield of 40° bushels of wheat per acre would mean a crop of 2,400 Ibs. of grain and 3,600 Ibs. of straw. From these two figures, the data in the table of (91) and that of (92), it is possible to compute the number of crops of wheat vielding 40 bushels per acre which would remove the amount of plant food in an acre-foot of one of the sev- eral types of soil represented in the table of (92). Soly- ing the problem for the potash in the clay soil the case would be 6.38 < 2,000 @4X52)+ 66x63) 0° 81 where 6.38 is the tons of potash per acre-foot, 2,000 is the number of Ibs. in one ton, 2.4 is the number of 1,000 lbs. of grain in 40 bush. of wheat, 5.2 is the number of lbs. of potash per 1,000 lbs. of grain, 3.6 is the number of 1,000 lbs. of straw with 40 bush. of wheat, 6.3 is the number of pounds of potash per 1,000 lbs. of straw, 362.9 is the number of crops of wheat. When the problem is solved for each of the essential plant foods used by the wheat crop, the results will stand for the clay soil as given below: Potash enough for 363 crops of wheat of 40 bush. per acre. Magnesia enough for 2,082 crops of wheat of 40 bush. per acre. Lime enough for 2,260 crops of wheat of 40 bush. per acre. Phosphoric acid enough for 210 crops of wheat of 40 bush. per acre. Sulphuric acid enough for 108 crops of wheat of 40 bush per acre. Nitrogen enough for 78.5 crops of wheat of 40 bush. per acre. In computing the nitrogen in the soil for this table .152 per cent., from the table in (89), was taken and the same weight of soil, 4,000,000 pounds per acre-foot as used for the other plant focds. It has been assumed that 40 bushels of grain and 3,600 pounds of straw per acre are taken from the ground each crop and that nothing is returned to the soil, and yet chem- ical analyses would indicate that there is enough of every- thing but nitrogen for more than a century of cropping, and this is saying nothing regarding the plant food which is known to exist in the second, third and fourth feet of soil in which the roots of plants regularly feed. Plainly we have very important knowledge yet to discover regarding the feeding of plants from the soil. 94. Experiments at Rothamstead.—The classic experi- ments which have been made by Sir J. B. Laws and his as- sociates regarding the conditions which determine the fer- tility of the soil, have thrown much needed light upon this 82 problem. By growing the same crop year after year on the same ground to w hich no nitrogen- bearing manures were applied. they learned that when’ fertilizers containing the essential ash ingredients of the plant were added to the soil larger yields and more nitrogen could be taken from the ground. They found that when wheat grown continuously for 32 years on the same soil without manure of any sort could obtain but 20.7 Ibs. of nitrogen per acre, the same crop on adjacent and similar land given fertilizers without nitrogen could gather 22.1 lbs. or 6.76 per cent. more. Barley, which, with no fertilizers, during 24 years could gather but 18.5 lbs. per acre per annum, did, when aided with other ash ingredients, remove from the al 22.4 Ibs. of nitrogen per acre. Beans, which gathered from untreated land 31.3 Ibs. of nitrogen per acre during 24 years, took off from the land under the other treatment 45.5 lbs. per acre. So, too, in a rotation of crops, 7 courses in 28 years, no fertil: izers gave 36.8 lbs. of nitrogen, while with supe rphosphate of lime the yield was 45.2 lbs. per acre. Again in the mixed herbage of grass land 20 years without fertilizers gave 33 lbs. of nitrogen per acre, but where mixed mineral fertilizers containing potash were given the yield was 55.6 Ibs. of nitrogen per acre. 95. Store of Nitrogen in the Soil.— The mean amount of nitrogen in eleven arable and grass soils at Rothamstead is placed by Laws and Gilbert at .149 per cent. and for eight other Great Britain soils at .166 per cent. Voeleker found in four Illinois prairie soils .808 per cent., and C. Schmidt gives for seven rich Russian soils .341 per cent. The mean of these 30 analyses is .219 per cent. and yet a soil containing but .1 per cent. will carry 4,000 lbs. or enough for nearly 60 40-bushel crops. 96. Amount of Nitrogen in Four Manitoba Soils.— As an example of soils exceptionally rich in nitrogen the table (e2) sh) below gives the distribution and amount per acre in each of the upper four feet of four Manitoba soils: Niverville.| Brandon. | Selkirk. | Winnipeg. Lbs. Lbs. Lbs. Lbs. IRSUA OO bres ssicc como eles eel aercieraetae 7,308 5, 236 17, 304 11, 984 SOCONG LOO ba cuhcccem deteeilecivenioe 5, 408 3,488 8,448 10, 464 RHI AGO tesenaradactisoce ceteeneone ne 2,484 2,592 2, 736 5, 688 HOULtO LOO ti acerencin Seer cccecacneine 1,520 870 1, 457 4,045 ROballpan tae sonnets 16, 720 12,186 29,975 32,181 JOT Sy Gain Go neanGorenamece cried &.36 6.093 14.987 16.09 Thus it is seen that in the upper four feet of these rich soils there was found from 6 to 16 tons per acre of nitrogen. 97. Forms in Which Nitrogen Occurs in the Soil.— Nitro- gen occurs in the soil in several distinct forms: 1. In humus, deseribed in (88), which is by far the most important form and the substance which carries the largest proportion of that which the soil contains. 2. In organic matter in the form of roots, stubble and farmyard manure, which by slow degrees is converted into humus to make good that which has been used. 3. As free nitrogen in soil-air which is seized upon by some forms of microscopic life described in (101) and con- verted into organic form for their use. 4. As nitrates of lime, magnesia, potash and soda, and this is the form from which most of the higher plants get their supply. 5. As ammonia, nitrous acid and nitric acid, which are transition stages to one of the nitrates named above and which are formed either from the humus or organic matter or are brought down with the rain. > 98. Distribution of Nitrogen in the Soil—In humid cli- mates the largest amount of nitrogen is found in the surface 6 to 12 inches, but as already shown in (96) large quan- tities are found as deep as four feet below the surface. 84 Warrington determined the distribution of nitrogen in some of the Rothamstead soils to a depth of 9 feet in 9-inch sections. The results he found are given in the table be- low: Nitrogen in soils at various depths. Arable soils.| Old pasture. Lbs. per acre|Lbs. per acre Binst)9 inchesrcontatmed w.micsclesce acselseieciesis cia cteleeie 3,015 5,351 Second inches contaimed encneneceicecinieietceaieleie ciate 1,629 anole Mira inches contained sacrimessicke miescicisceiieeiieaee 1,461 1,580 Fourth 9 inches contained. 1, 228 1, 412 Fifth 9 inches contained.. Paice ts 1,090 1,301 Sixth 9 inches contained saacecsa- cceenccteseciemes ence cisee 1,131 1,186 SurflacesitectCcontained!s..a--cse nee ean vances ene eee 7, 333 10, 656 Second ankeet contained a ..snco cea terese a nceeee cen A SOD. = 2 l\lescisisvsisnstelsetete Third 3feeticon tained: vss asco eee le poeio eee e one ADO, - Sill eeaalaeierseniee 10) > A en ea Rt aia cML Se eno irene riot Geri SGN oan G25 Ne ase eeme-reine Tn these two cases the nitrogen decreases downward until about four fect and below this depth to nine feet the amount remains nearly constant. It will be seen that the amount is very large in the aggregate. Enough for more than 240 crops of wheat, 40 bushels per acre, could it all be used. 99. Amount of Nitric Acid in Soils.—The amount of the available nitrogen in soils, or nitric acid, is seldom a large quantity and while crops are growing the quantity is still smaller. Warrington states that the nitric nitrogen in the soil seldom reaches 5 per cent. of the total amount present, and in the surface three feet of the arable soil referred to im (98) this would represent 366.6 lbs. of nitric nitrogen and 1,650 lbs. of nitric acid per acre; enough, if it could all be used, to give a yield of 57.5 bushels of wheat per acre. 100. Nitric Acid in Fallow Ground.—The amount of ni- tric acid in fallow ground was determined to a depth of 4 (9 9) 5 feet in one-foot sections on May 24 and again on Aug. 22, and the results are given in the table below: Nitric acid in fallow ground in pounds per aere. | ist foot. | 2nd foot. 3rd foot. 4th foot. De yee ecco erly cs Maes isla wise 2 hie aie 78.03 21.43 8.13 4.76 PARENTS UH Aid slo sain ssc is ecissd wetele a Sra siel sie s¥s 293.72 116.17 23.50 16.72 Grima PEs eet te ser nt 215.69 94.74 15.37 | 11.96 These figures are a mean of the amounts found in nine different sub-plots, the soil being a clay loam changing into sand in the third foot. It will be seen that the total amount of nitric acid at the close of May was 112.35 Ibs., contain- ing 24.97 lbs. of nitrogen, enough for only about 14.3 bushels of wheat. On the 22nd of August, however, there had been an increase to 450.11 Ibs. per acre, containing 100.02 Ibs. of nitrogen, enough for nearly 60 bushels of wheat per acre. 101. Source of Soil Nitrogen.—Until recently it was maintained that the nitrogen for the growth of all plants was derived from the humus of the soil and from the small amount of ammonia and nitrous and nitric acids brought down by the rains. It is now known that the free nitrogen of the atmosphere is the ultimate source of soil-nitrogen, and that the soil-nitrogen is being continually returned to the air again just as was long ago recognized to be the case with the carbon of living forms. 1. The immediate source of humie nitrogen is the slow decay of organic matter, whether this be the roots, stems or leaves of plants or the tissues and waste products of ani- mals, and a large part of the life processes of the world take place between the conversion of humus into living tis- sues and dead tissues back into humus again. 2. The formation of nitrous and nitric acids through an oxidation of the nitrogen of the air by electrical discharges 5 86 such as occur during thunder storms is generally conceded. It is also thought that a part of these combinations may be brought about through the action of ozone upon ammonia. Warrington is also of the opinion that the peroxide of hy- drogen in the air causes the conversion of some atmospherie ammonia into nitric acid, and hence that not all the nitrie acid brought down by the rains was formed as new ma- terials in the atmosphere from direct union of oxygen and nitrogen gases. The amount of nitrogen brought to the soil with the rains seldom equals 5 Ibs. per acre per annum in the open coun- try, as shown by the following table: Nitrogen as ammonia and nitric acid, in pounds per acre per annum, in rain. incoln, Rothamsted. Sega Barbadoes. 8 years. 3 years. 3 years. Lbs. Lbs. Lbs. Nitrogen as ammonia.............. 2.53 0.74 0.93 Nitrogen as nitric acid.......... .. 0.84 1.00 2.84 3.37 1.74 SILT! tL s “hou ; + ‘ a 3 0 a a =. 5 S| Fic. 25.— Showing the influence of free-nitrogen-fixing germs on the growth of peas. The large plants all grew in sand containing the nitrogen-fixing bac- teria, while the small plants grew in soils identically the same except that all bacteria were excluded from them. After Hellriegell. 87 These amounts, it will be seen, are far too small to be of great importance to plant life. 3. The process of symbiosis is a third method by which the nitrogen supply of the soil is maintained and next to the decay of organic matter is the most important of any yet well understood. It was in 1888 that Hellriegel pub- lished the results of his studies, which thoroughly estab- lished the fact that great numbers of microscopic forms of life inhabit the roots of leguminous plants, forming upon Fic. 26.— Showing the growth of rye, oats, peas, wheat, flax and buckwheat in soils fertile in all elements of plant food except nitrogen, and illustrating the power of the pea, through its root tubercles, to procure nitrogen from the air. After P. Wagner. them tubercles in which these organisms live and withdraw free nitrogen from the soil-air for their needs. It had long been known to farmers that in some way clover in rotation with other crops left the soil richer in nitrogen, and it is now known that the bacterium which lives on the clover roots, deriving a part of its food from the clover plant, at the same time increases the nitrogen supply available to the clover crop and so we have two forms of life living together 88 in what has been named symbiotic relations. There are other forms of bacteria which live upon the bean, pea, lu- pine and other members of this family, also having the power of fixing free nitrogen from the soil-air in forms available to higher plants. It is known that other forms of bacteria live in symbiotic relation with soil algae and in this way increase the sup- ply of soil nitrogen as shown by Frank, Schlésing, Jy., and Laurent in 1891, followed by Kosswitsch in 1894; and the great demands ae the fixing of free nitrogen to make good the rapid return of it to the air and loss in drainage waters appears to call for other agencies than those named. Pie. 27.—Showing oats growing under conditions identical with those of ig. 18, except that the several pots received Chile saltpetre, 1, 2 and 3 grams respectively, thus enforcing the immense importance to such plants of nitric nitrogen. After P. Wagner. 4. Winogradsky has shown that there is a form of bacil- lus in the soil which, when supplied with sugar and iso- lated from the influence of oxygen, is capable of thriving and fixing free nitrogen from the air, and this discovery may lead to a knowledge of still a fourth mode of increas- ing the world’s supply of nitrogen. 89 Some of Berthelot’s experiments are thought by him to show that soils destitute of all visible vegetation may gain large quantities of nitrogen when simply exposed to the air, and he thinks he has realized gains as large as 70 to 130 Ibs. of nitrogen per acre in 11 weeks. Such conclusions, how- ever, require careful verification as they are at least ap- parently contradicted by field practice. 102. Nitrification.—The formation of nitrates in the soil involves at least four distinct phases or stages: (1) the am- monia stage, (2) the nitrous acid stage, (3) the nitric acid stage and (4) the nitrate forming stage. When humus or dead organic matter is placed under the right conditions of temperature, moisture and air in the pres- ence of ammonia-forming germs, these organisms feed upon portions of it and throw off ammonia as a waste prod- uct. Ammonia is extremely soluble in water and is re- tained by it in large volumes. Even dry soil has the power of condensing and retaining it. In a fertile soil where ammonia has been formed there are also present nitrous acid germs which are able to use ammonia in their lite processes but throwing off nitrous acid as a waste prod- uct. The niter germs or ‘mother of petre’ utilize the nitrous acid in their work and throw off as a by-product nitric acid. This nitric acid readily attacks any of the bases in the soil which are held by carbonic and other weak acids, displacing them and forming nitrate of lime, mag- nesia, potash or soda, as the case may be. In the old days of “niter farming,” when nitrate of potash for gunpowder was obtained from the soil, great pains were taken to form a soil rich in organic matter and to keep it warm, well supplied with moisture and thor- oughly aerated. These, too, are the points to be secured in the best management of soil for farm and garden crops. 103. Denitrification.— Pitted against the processes of fix- ing free nitrogen from the air, which have been deseribed, 90 there are other processes which reverse these operations and set free again the nitr ogen of organic compounds and of ni- trates so that it is again re ‘turned to the atmosphere as free nitrogen gas. (1) Dr. Angus Smith showed in 1867 that nitrates in sewage waters are decomposed and the nitrogen set free as agas. (2) Schlésing showed that when moist humus- bearing soils are placed in an atmosphere free from oxygen they fickle lose all traces of nitrates. (3) Warrington demonstrated that sodium nitrate in a water- logged soil is decomposed and the nitrogen liberated as a gas. (4) So great is the demand for oxygen in rich water-logged soils that according to the experiments of Miintz even such compounds as chlorates, iodates and bromates are deprived of their oxygen, leaving iodides, chlorides and bromides in their place. (5) W hen black marsh soils are stirred up with water and allowed to stand Prof. J. A. Jeffery and the writer have shown that the nitrates rapidly disappear and nitrogen gas is set free. In all of these cases there are microscopic organisms in the soil and water whose needs for oxygen are so great that when that which is free in the soil-air or water-air is not sufficient they have the power of decomposing nitrates and even some organic compounds for the oxygen they contain and in this way liberate free nitrogen. (6) There is still another condition under which denitri- fication takes place in which the loss is large, rapid and nearly complete. It is when human excrements are covered with pulverized dry soil, as is done in the dry-earth closets. The late Colonel Waring kept two tons of dry earth for a number of years, having it used over and over again in or- der to see how long it might be used without losing its effi- ciency. The closets were filled with the dry earth and exere- ment about 6 times each year, and when they were emptied the material was thrown in a heap on a floor of a well venti- lated cellar to dry. After the same soil had been used over not less than 10 times it was analyzed for the amount of nitrogen it contained, and in 4,000 Ibs. of the soil was found 91 no more than 11 Ibs. of nitrogen and yet not less than 230 lbs. had been added to it and the soil at the start contained at least 3 lbs. There had been set free therefore 230 — 8 = 222 lbs. of nitrogen. Nor was this all, for so completely had all the carbonaceous materials been oxidized that even the paper used had en- tirely disappeared. How far these processes take place under field condi- tions when farmyard manure is applied we have yet to learn. CHAPTER ITI. SOLUBLE SALTS IN FIELD SOILS. All the food of plants is taken by them in the form of liquids or of gases, and hence the fertility of a soil must be determined by the rate at which plant food may be dis- solved in the soil water and carried to them at the time the crops are growing. If the ash ingredients and the nitro- gen used by plants while growing are supplied in the soil water as rapidly as the crop can use them, then maximum yields will be certain if the temperature and sunshine are also right. 104. Amount of Soluble Salts in Field Soils.—There is a very wide difference in the amount of salts dissolved in soil water under different conditions. In arid regions, where there is little soil leaching, the salts become in places so abundant that plants are unable to grow and alkali lands are the result. In humid climates, especially where the soils are sandy, the salts may be so small in amount that plants starve. In the table below these differences are shown for the surface foot. Water soluble salts in soils||Water soluble salts in soils of arid climates. of humid climates. Where bar- | Where bar- Sah ears pee oer ley will not | ley grows Bornierely Foor sandy grow. 4 ft. high, ae Stare Lbs. per million of dry soil 8,585 4,877 272 21 Lbs. per acre of 4,000,000 DSi etete on neces c tatoos 34, 340 15,508 1,088 84 These figures show a range of total salts soluble in water from 17 tons per acre foot to less than .05 tons. 93 105. Maximum Amount of Water Soluble Salts Which Limit Plant Growth.—Hilgard concludes from his studies that the maximum amount of soluble alkali salts which are consistent with a full crop of barley hay is 25,000 to 32,000 lbs. per acre in the surface four feet of soil, pro- vided this is not more than one-half its weight sodium car- bonate. Whitney places the limit of possible plant production in the soils of the Yellowstone Park at 15,000 lbs. per acre in the surface foot, where the black Alea or sodium carbonate is absent. Grapes grow in Algeria in alkali soils containing 600 lbs. per million of dry soil but die when it reaches 1,700 Ibs. per million in the surface soil and 3,700 in the sub- soil; but grain crops grow normally Fe le soil contains 2,000 Ibs. per million, 106. Why too Much Soluble Salt in Soil Kills Plants.—De Vries found, as represented in Fig. 28, that when the liv- Fic. 28.—Showing the effect of too strong solution of salts on the proto- plasm of plant cells. ing cells of a plant were immersed in a 4 per cent. solution of potassium nitrate, there was first a shrinkage in volume through a loss of water, as shown between 1 and 2. When the solution was given a strength of 6 per cent. the proto- 94 plasmic lining, p, began to shrink away from the cell a h, as shown at 3, and when the strength of the solution wa made 10 per cent., the conditions shown in 4 are pr sane When the cells of plants are affected in this way they wilt and growth ceases. A soil containing 20 per cent. of water and also 2,000 Ibs. of water soluble salts per million of dry soil would contain 2,000 lbs. in 200,000 lbs. of water or 1 part in 200, which is .5 per cent. If the soluble salts constitute 2 per cent. of the dry weight of the soil then with 20 per cent. of moisture present the stre neth of the soil solution would be equal to that which De Vries found fatal to plants, or 10 per cent. The salts in the surface three inches of soil Pe which Hilgard found barley to grow four feet high were 1.2 per cent., While it was 2.44 per cent. in the same a where the barley died. With 20 per cent. of moisture in the soil, and all the salts dissolved, the soil solution in the first case would represent a strength of 6 per cent. and in the second case 12.2 per cent., which is larger than the amount De Vries found fatal. 107. Concentration of Salts in Zones.—W here long contin- ued drought has occurred in soils rich in soluble salts the tendency is for the salts to collect in the surface two or three inches and in this wav become injurious to plants when they would not be so with an abundance of water in the soil. When heavy rains follow such a concentration of salts at the surface, or if the land is irrigated so as to produce percolation, the result is to wash the salts down in a body to the depth reached by percolation, and hence it may hap- pen that a layer of soil very rich in salts may occur at the surface at one time and later at a distance of 12, 18, 24 or 30 or more inches below, determined by the depth of per- colation. 108. Origin of Soluble Salts.—The excessive amounts of salts found in alkali lands are usually the result of long 95 continued rock decay under conditions where little or no leaching has taken place. Rains enough fall to produce decay, but not enough to carry the salts formed into the drainage channels and out of the country. This is why alkali lands are largely peculiar to desert. or semi-arid climates. 109. Leaching Necessary to Fertile Soils.—It is clear from 106 and 108 that if there was not some leaching to take up and carry away the extremely soluble salts not available as plant food all soils would in time become “al- kali lands ;” so that while excessive leaching is undesirable, a sutticient amount is indispensable. The prevention of the accumulation of undesirable solu- ble salts in the soil of irrigated lands in dry climates is one of the most serious of practical problems. 110. Soluble Salts in Marsh Soils.—The black marsh soils of humid climates often contain unusually large amounts of soluble salts, sometimes reaching 2,366 parts per mil- lion of the dry soil in the surface 6 inches after maturing a crop. This would make the water contain 1.18 per cent. of salts if the water content of the soil was 20 lbs. per 100 of dry soil. Many of these soils behave much like alkali lands, beimg unproductive, the crops often dying when there is no evident reason for it. 111. Correction for Alkali Lands.—I+t has been found that when a soil is unproductive from too high a per cent. of sodium carbonate or black alkali and there is not enough of other soluble salts to be injurious, this may be corrected in part by the use of gypsum or land plaster, which has the effect of converting the carbonate into the sulphate or “white alkali,” like amounts of which are less harmful. It often happens that waters which must be used in irri- gation contain black alkali, and where this is the case it is well to correct the water by using land plaster in the reser- voirs or distributing canals, for the water to run over or through, before reaching the field. 96 7S) 50) 29) |= ‘TL T Sa = a PARTS PER MILLION OF DRY SOIL. StChIESsauRs JOTI SH RHR ee all Tea tom zai LTT 125 rm RAIN-FALL, Jf APRIL MAY. CORN PLOT-3 inde egae soil under growing corn, ag z i ea 3 +. 29.-Showing the seasonal changes in the amounts of nitrates in the 97 240}, PARTS| PER ay CORN PLOT-1- S ~ * 7 3 71) ‘ * 1 ofa ‘ ahs ' em a ie pale it | He Parag i en ee, it | | eal «| a ' aii et T | i :. 30.—Showing the seasonal changes in the amounts of soluble salts in the soil under growing corn. 98 112. Drainage the Ultimate Remedy.—Drainage must be the ultimate remedy for any alkali land, as it can be only a matter of time when any fertile soil will develop enough undesirable soluble salts to render it sterile or less produe- tive, unless the soluble salts not needed are removed, and only drainage can do this. 113. Deep and Frequent Tillage Helpful.—It is clear that whatever means will prevent the excessive evaporation of water from the surface will in so far lessen the concentra- tion of salts there, and hence frequent and deep cultiva- tion, to form effective mulches, will lessen the rise of water, and therefore of salts, to the surface and in this way permit crops to be grown on soils which are critically near the limit of sterility on account of the high salt content. 114. Change in Soluble Salts with Season.—In Figs. 29 and 30 are represented the changes in the nitrates and total soluble salts in the surface four feet under three fields of corn, beginning with April and ending with Sept. Re- ferring to the nitrate curves it will be seen that the nitrates start in April nearly equal in the four feet, but increase rapidly in the first foot until the middle of June, when the corn begins to draw on the supply. From this time they decrease rapidly until the middle of July, when they are less than in April and less than in the second foot. By the middle of August, when the crop has ceased to draw much but water from the soil, there is a slow increase again and then one more rapid after the corn is cut, Sept. 1. The change in the total salts is much less marked, but evident, there being a general decrease. The mean amount of salts at the beginning and at the end of the season are: April 18. Sept. 1. Total salltse. sca ccc ceeien BOs) 363 NUTEREEOS aie ete Peace mioeerletels 86 32 Difference ves. seusteeunee 454 331 From these figures it appears that the salts, other than nitrates, have decreased during the season 123 Ibs. per mil- lion of the dry soil for the four feet, or 1,968 Ibs. 99 115. Variation of Soluble Salts with Different Crops.— There is a marked difference in the amount of soluble salts, and especially in the amount of nitrates, in soils under crops like corn and potatoes, where inter-tillage is prac- ticed, and under such crops as clover and oats, where the ground is not cultivated at any time of the season. This is very clearly shown in Fig. 32; the nitrates are plotted in the lower two sets of curves and the total soluble salts in the upper two sets. The nitrates in the first foot under the corn and potatoes increased rapidly until July 1st, when they were five times as concentrated as in the fourth foot; but in 30 days more the nitrates had been reduced from over 400 Ibs. to 40 Ibs. per acre. PARTS PER MILLION OF DRY SOIL. | "| SOLUBLE eatin Mina ADR Hic, 31.—Shows the mean ameunt of nitrates and total soluble salts in the surface four feet of soil under cultivated and not cultivated crops. In the case of the uncultivated crops the fields started with about 40 Ibs. per acre and increased to only 70, June Ist, when they were highest; from this date they fell to little more than 10 Ibs. per acre in the surface foot, but rose again to 60 Ibs. at the end of August. With the total soluble salts there was at first a more L. of C. 100 180_PARTS PER MILLION OF DRY SOIL- Hi | i id ia Fr GROUND NOT CULTIVATED] CLOVER AND OATS 4 ” Te “SOLUBLE GROUND CORN A | NOT CULTIVATED. eat CLOVER AND OATS. Ly E {1 STATA Peet Trt coy I hrm eather a CULTIVATED. CORN AND POTATOES NITRATES eee ; : ll i cameaaneeeit i fic. 52.—Showing the difference between the amounts of nitrates and of total soluble salts in the soil under cultivated and not cultivated crops. 101 rapid rise, from nearly 300 lbs. per acre in the surface foot on the cultivated ground April 18, to about 500 Ibs. per acre, but falling again on August Ist to 250 lbs. On the clover plots the start was at 250 Ibs. per acre in the surface foot, rising to 290 lbs. in 12 days. From this date there was a slow decrease, falling to 220 Ibs. on the date when the cultivated grounds were highest, at 600 Ibs. per acre. 116. Relation Between Nitrates and Total Soluble Salts.— As a general rule when the nitric nitrogen in clay loams is very igh the total soluble salts, as indicated by the electrical method, are yery low. It will even happen that the electrical resistance will show but little more salts than are required to account for the nitrates, and this is perhaps what should be expected for, if nitric acid is being formed in the presence of carbonates, these would be decomposed to form nitrates, and if the rate of nitrification were suf- ficiently rapid, it might be that all the carbonates would be decomposed and little else but nitrates left. The ratio of total soluble salts to nitrates in the surface foot of the five cultivated fields represented by the eurves was a mean for the season of 2.14 to 1, while in the surface foot of the clover fields it was 4.8 to 1. For the second, third and fourth feet the ratio is 7.29 to 1 for the corn and potatoes, and 9.97 to 1 for the clover, alfalfa and oats; and these ratios are what would be ex- pected if the formation of nitric acid destroys the earbon- ates and bi-carbonates in the soil water. 117. Closeness of Plant Feeding.—I[t was pointed out in (7) what small amounts of a fertilizer can be widely dis- tributed through an acre of soil, and we may now consider how extremely close plants do feed the nitrates of a soil. In the table which follows are given the amounts of ni- trates which were found in each foot of nine field plots, represented by the curves, between July 18 and Sept. 1. 6 102 Table showing mean amounts of nitrates under different crops between July 18 and Sept. 1, in lbs. per acre of dry soil. Plot 1.| Plot 2.) Plot 3.| Plot 4.| Plot 5.| Plot 6.| Plot 7.| Plot 8.| Plot 9. Oats Pota- | Pota- Corn. |Clover.| Corn. cea tees: thee Clover.!Alfalfa | Corn. Lbs. | Lbs. Lbs. | Lbs. Lbs. | Libs. | Libs. | Lbs. Lbs. 1st foot.. 50.94 58.32 24.11 15.07) 180.21) 105.32 44.91 18.&4 10.85 2nd foot.| 127.35 23.74 48.81 11.42} 155 95} 172.62 15 63 10.65 8.88 3rd foot.. 83.52 10.28 59.44 18.81 49.65 50.66 le) 9.53 10.79 4th foot.. 40.83 14.80 64.82 27.05 24.08 59.82 4,59 9.73 12.51 When these amounts are expressed as parts per million of the dry soil in the form of nitrogen, they stand 3.38, 1.61, 0.72 for corn; 3.87, 2.98, 1.00 for clover; 1.25 for alfalfa and 6.99 for potatoes, and yet with these small amounts of nitrogen in the soil during the time when the chief growth was being made, large yields were produced. 118. Limits of Nitric Nitrogen at Which Corn and Oats Turn Yellow.—Taking samples of soil from the surface foot upon which oats were turning yellow and under adja- cent areas where the plants were normal green it was found that two sets of duplicate determinations gave Oats vellow Oats green. Pes ve ‘ { June 10 .025 213 Parts of nitric nitrogen per million of dry soil.... - (June 11.027 297 These amounts, when expressed in pounds per acre and as nitrates, are only .392 Ibs. and 3.843 Ibs., respectively, for the yellow and green oats. Table showing the amounts of nitric nitrogen under corn rows where leaves are turning yellow and where they are yet normal green. Plot 9. | Marsh soul. ||| . Randall’iplae Depth. — — —- Yellow. | Green. | Yellow. | Green. Yellow. | Green. USteOOtiarcncsceactl 0.61 0.92 0.95 3.62 0.10 0.95 7X6 lies (ot a RAN GOMe OOD MiGs 0.14 1.70 0.40 1.41 0.06 0.60 Sadi LOOG ew cssinrcuts 0.41 2.95 0.07 0.52 0.25 0.37 ‘Ath fOOtrencacten soos 0.42 1.82 0.00 0.00 0.30 0.30 105 Small as these amounts of nitric nitrogen are the yield of corn on plot 9 was a mean of 8,000 Ibs. of water-free matter per acre. On another plot where the yield was 11,440 lbs. of water-free matter per acre the nitric nitro- gen was reduced as low as 1.446 parts per million in the first foot and .726 parts in the second foot. It must be understood that in these cases the demands for nitrogen were so urgent that the plants were taking it up almost as rapidly as it could be produced, leaving the amounts so low, as the figures show. 119. Nitrates of Fallow and Cropped Ground.—JIn the table which follows are given the amounts of nitrates found under different crops and, at the same time, under mmmediately adjacent fallow ground which had been ecul- tivated and kept free from weeds. Oats. Fallow. Barley. 1: S|) Dota : Sl ebotall eae | Ova Nitrates.| salts, ||Nitrates.| cats, ||Nitrates| colts, isi Rea ee 5.94 | 70.94 || 246.40 | 199.3 || 2.62 | 61.72 OE MOOS xis occe sare 8.12 46 3] 26.75 123.5 5.10 87.08 Cee LOO Ut. c. ke ects nae 4.73 124.7 6.50 108.0 4.04 112.6 Ate LOO tecccene: ccc 4.60 39.44 2.84 42.10 3.03 51.76 Oats. Fallow. Peas. Sty LOOGe raceoce cscs Oe) 80.35 143.05 20631, 8.38 77.00 MNES LOO tanto su cok ees 3.22 162.1 29.50 254.3 18.57 197.2 CML OO Ltciersccatcte stevie 2.95 102.7 8.87 115.0 6.59 135.8 Ate TOOb.\. cco oie we 2.70 58.24 4.10 95.32 2.66 44.62 Oats. Fallow. Spring rye. BSG OO Gs orca sinese ate ce 2.47 78.56 129.15 211.3 1.24 17.34 BUS LOOte scoot conan 2.46 102.9 35.60 254 7 2.62 102.1 BOM LOOU. c-cd dae ee 3.83 72.98 9.11 117.8 2.07 94.82 AL DELOO tare case ciinecs 3.16 33.99 4.08 61.92 2.78 48.85 If the mean amount of nitrates in the surface foot of the fallow ground and under the crops are expressed in pounds per acre they stand 473.65 to 10.88. This difference is enough for 85 bushels of oats per acre, where the ratio of grain to straw stands as 3 to 5. 104 120. Loss of Nitrates from Fallow Ground During Winter and Spring.—A field which has been kept fallow during a whole season and cultivated either once per week or once in two weeks had the nitrates determined in it on August 25 and again the next spring, April 30. The field was di- vided into nine plots and the nitric nitrogen was deter- mined in each one to a depth of four feet on both dates. The results are given in the next table. Table showing the amount of nitric nitrogen found in fallow ground after the leaching of winter and early spring. Pounds per million of dry soil. Nov ol-plob. (late. Shee aks mien 27. ul Saeeimen ist foot { | APT: 30, 1900 {| 75.90) 58.31) 58.03) 55.22] 51.66) 51.25] 98.02] 44.34) 48.26 St foot) | Aug. 22, 18997 | 16.81] 13.58] 26.67/ 26.80} 19.09] 16.82) 5.50] 24 07] 19.60 2d foot )| APE 30 19005 | 15.81] 18.75] 7.97] 6.51] 13.06] 15.66) 17.33] 18.56] 14.85 - || Aug. 22,1899? | 4.34] 7.75] 1.81] 9.07} 5.74] 2.76] 1.43] 6.06] 6.61 3d foots | APT: 30, 18005 | 2.46} 4.75] 4.93] 4.89] 3.94) 7.35] 6.04) 8.24) 6.71 'Y| Aug. 22,18992| .70] 154] 2.48] 80] 0.54) 1.37] 0.95] 0.54] 38 OL dthfoot) | AP®- 30; 19005} 2.95] 237] 3.05} 2.35] 2.01) 2.36] 3.65] 5.60] 5.08 ‘){ Aug. 22, 18907] .80|......] 1.04)...... 1.85) 0.52[ 0.26) 0.53) 3.51 It is clear from this table that however large the leach- ing may have been it was not enough to prevent the nitrates Wie. 38.—Showing the difference in the amount of nitrates in the surface four feet of fallow ground, the succeeding spring, and that upon which crops had been grown, 105 being higher the following May than they were August 22 before. 121. Nitrates on Fallow Ground in Spring Compared with That not Fallow.—Comparing the mean amount of nitric nitrogen in nine field plots bearing crops in 1899 with that of the nine fallow plots of the same year, as found in the spring of 1900, the amounts are as stated in the table below Oo and represented graphically in Fig. 33. Table showing the differences in the amounts of nitric nitro- gen after the winter and early spring rains in ground kept Jallow and free from weeds the previous season and that bearing crops. Ist foot. 2d foot. 8rd foot. 4th foot. Depth. Fallow plots, pounds per acre of LDV ESOLU er taatta te roeniceine aientae CG 212.00 56.22 21.91 13.11 Plots not fallow, pounds per acre MUPVERG Mle meveat ied ctnecinca teoak anal eich a ce 25.24 15 O8 10.00 7.24 WUTLOLEN CO) ae ede ls's ce diem eve tive 186.76 41.14 11 91 5.87 From this it is clear that the crops on the fallow ground start out in the spring under conditions very superior to those on the fields which had not been fallow, there being 245.68 lbs. of nitrates more per acre in the surface four feet. 122. Development of Nitrates Influenced by Depth and Frequency of Cultivation.— When a series of cylinders like those represented in Fig. 58, p. 187, are mulched by stir- ring at different depths and the stirring is repeated at dif- ferent intervals the rate of formation of nitrates 1s ma- terially modified, as shown in the table below: Difference in the amount of nitric nitrogen, after 258 days, due to differences in depth and frequency of cultivation. Depth of cultivati’n.| Cultivated once per week. |Cultivated once in two weeks. Lbs. per acre. Lbs. per acre. linech deep... ....... 217.69 213.29 2 inches deep........ 323.44 199.00 3inches deep........ 441.24 401.68 4 inches deep........ 387.96 245.26 106 It can be seen that the nitric nitrogen has increased in both series to a depth of 3-inch cultivation and it has in- creased with the frequency of the cultivation. 123. Soluble Salts Affect the Movement of Soil Moisture.— The varying strength of salt solutions in soil moisture mods ify both the movement of moisture in the soil and its rate of loss from the Dees: These movements are influenced (1) by changes in the intensity of surface tension; (2) by changes i in as inte rnal friction of the soil iii state or its viscosity; and (3) by modifications of the surface of the soil due to de ae of salts upon and within it, where evaporation is taking place. 124. Modification of Surface Tension by Soluble Salts.— As a general rule the surface tension of a strong soil solu- tion is greater than that of a weaker one, or of pure water, and in so far as this influence is operative it tends to in- crease the rate of capillary movement toward the surface or toward the roots of plants. 125. Salts in Solution Lessen Rate of Evaporation.—— When water has been brought to the surface of the soil by eapil- larity it has yet to evaporate and unless this takes place the surface soil would become capillarily saturated with water and remain so. Since salts im solution increase the sur- face tension it will require a greater energy—a higher temperature—to throw the water molecules off into the air than would be required to do so from the surface of pure water and hence the evaporation from soil solutions rich in salts is slower than it is from weaker ones under other- wise like conditions. As the salts become concentrated at the surface by evaporation the moisture becomes a stronger and stronger solution and hence the rate of evaporation be- comes less and less so far as it can be influenced by this factor, in this way. 126. Viscosity of Soil Water Modified by Soluble Salts.— The internal friction of soil moisture is made greater by 107 the presence of salts in solution and the more concentrated the soil solution is the greater is the internal friction, and hence the slower must be the rate of flow, and it may be that the much slower rate of capillary movement in a compara- tively dry soil is to a considerable extent due to this in- creased viscosity or internal friction. But as one effect of the salt in solution is to increase the surface tension, while the other decreases the flow by increasing the friction, the two influences work against each other, making the com- bined result less than it would be could either act alone. 127. Deposits of Salts after Evaporation May Lessen Loss of Soil Moisture.—\WVhere water rich in salts is being evap- orated from a soil these salts may accumulate upon the sur- face and form a sort of mulch more or less effective accord- ing to its texture; or they may be deposited as a crust upon, over and between the soil grains, which may nearly close the capillary pores and in this way lessen the loss of water by evaporation. Such a closing of the pores is likely to be more harmful in shutting out the air and in lessening the freedom of entrance of water after rains than it can render assistance in conserving soil moisture. CHAP Ii ay, PHYSICAL NATURE OF SOILS. 128. Texture of Soils.—The size of soil grains and the way they are grouped in composite clusters forming ker- nels or crumbs has a very great influence in determining the physical properties of soils and their agricultural value, and as soils vary quite as widely in the size and arrange- ment of their grains as they do in their chemical composi- tion it is clear that this phase of soil problems must take at least equal rank with those considered in the last chapter. In all agricultural soils except the very coarse and sandy ones there is a composite granular structure which renders them muchmore open and porous than they could otherwise be, and when a soil is puddled this structure or texture is destroyed in a large measure and the separate grains are then brought into the closest possible arrangement, and they become nearly or quite impervious to both water and air, approaching the condition of brick and potter’s clays. 129. Size of Soil Grains.—\Vhen the fragments of rock are so coarse that very few are smaller than .01 of an inch in diameter we have a sand rather than a soil. Most plas- tering sands are made up of grains ranging from .01 up to .O8 of an inch in diameter. In the table which follows is given the mechanical anal- yses of three types of soil: Tt will be seen from this table that only .8 per cent. of either soil is made up of grains having diameters so great that only 28 are required to span a linear inch, while the heavy elay soil has nearly one-half of its weight made up 109 of grains so small that 25,000 of them must be placed side by side to span a linear inch. SANDY SOIL. Loess Sor. Number of Number of Diam.| grains Per || Diam grains m. m. | per linear | cent. || m. m., | per linear inch. inch. 1to3 23.1 A 1lto3 ea 5tol Biley 3.0 Apycoye t 31.7 A 63.5 6.9 4 63.5 3 84.7 8.1 A} 84.7 .16 163.9 3.0 16 163.9 12 211.9 1.6 12 211.9 .072 353.4 1.2 072 353.4 -047 540.1 3.6 OKT 540.1 .036 704.3 6.8 .036 704.3 -025 1,020. 14.6 025 1,020. -015 1,695. 14.8 O15 1,695. .008 8, 226. 30.7 .008 3, 226. .0001 25, 000. 4.6 .O001 25,000. | | | | Per cent. pee we LR Re ork ad AAS OS SONOaS FL HBAvy Cray SOIu. Number of Diam.| grains Per m. m, | per linear | cent. inch. 1to3 Pesyil 8 5 tol 31.7 1,2 4 63.5 2.0 a} 84.7 1.6 .16 163.9 9 12 211.9 8 072 353.4 52 047 240.1 2.0 036 704.3 Sal 025 1,020. 5.6 015 1,695. 10.6 008 3, 226. 24.7 .OUOL | 25,000. 48.0 130. Number of Grains of Soil in a Cubic Inch.—If soil grains were perfect spheres like shot and in a given soil they were all of a single size it would be a simple matter to be 2.22; C262 2.e.e "ila a * A" Gs" Sia! Ml" Ga” i.’ Gide’ SB" GA i’ Ga’ is’ 4 hetdteta’ste’s WEMEMEN G (-\t-MA \ ~ "loa G =, §AD\SBZ ) K = OOOC = R AN Xx Zy NY (la Ite. 34.—Showing the effect of size and arrangement of soil grains on the pore space and upen the movement of air and water through a soil. 110 determine the number ina cubic inch. If a soil were made up entirely of the largest size given in the last table, then 23 would build one edge of a cube an inch on a side and the number in a cubic inch arranged in the manner repre- sented in the lower part of Fig. 34 would be 23° — 23) x 2d 23) Ie OT. On the other hand, if they were all the size of the smallest grain in the table then the number would be 25,000? = 15,625,000, 000, 000, or enough to form three and a third continuous lines of grains in contact from Boston to San Francisco. 131. The Size of Soil Kernels.—It must be kept in mind that while it is true that the heavy clay soils are made up largely of soil grains of the extremely small size considered in (130) these minute grains are generally bound together in groups or kernels of various sizes and it is only by long boiling in water or thorough pestling that these can be broken down. The writer has found that when air-dry samples of the heaviest clay soils are thoroughly pestled in the dry condition it is difficult to reduce their texture to a finer degree than kernels averaging .01 to .005 m. m. in diameter or such that from 2,500 to 5,000 are required to span a linear inch; but even this degree of closeness of texture is too fine to allow of proper drainage and soil ven- tilation and to permit roots to make their way through the soil with the freedom required for good erops. 132. Specific Gravity of Soil Grains.—The specific gravity ot soil grains, or the number of times they are heavier than an equal volume of water, varies somewhat, as does that of the minerals which compose them. As there are not many common minerals more than three times as heavy as water and not many lighter than 2.5 times as heavy, the specific gravity of soil grains will lie between these two figures and it is usually found to be near 2.65. ia 133. The Pore Space of Soils.——When the weight of a eu- bic foot of dry soil is known the amount of pore space or space not occupied by the soil grains may be computed from the specific gravity. Taking the weight of a cubic foot of water at 62.42 Ibs., a cubie foot of dry soil, if there were no open spaces in it, should be 2.65 >< 62.42 = 165.4 Ibs. With this value and the data given in (149) the pore space of those soils may be calculated. Thus, for the surface toot we have 165.4 — 79 = 92. : : 165.4 92.23 per cent Pore space = That is, in this soil the surface foot is more than half open space. . The pore space for the six feet will be as given be- low: Weight of Rail Pore space, ) Lbs. Per cent. ERESELOOGe coe ae. sie cde kien ow oo dation naa Ooeelee eo ace nae 79.0 52.23 SHCOD CULO Us ar. ioaheicrors satis oatcreloren oe aie eo aac tee aio satin 92.62 44.00 Abvenie | Fito te a ohae ne naar amine ace wees BS CUS C amines RB OnoSer 104.59 36.76 Mourehifoo tise se cwce ieee osc ne okK one nee aisen en eeeee ds 106 21 35.78 UTE GETELOO Gate crest orcas ners mete oe So wie ole eee ae Ices otto 111.06 32.85 (Sib-4 rl SUnf0101 rata Sach Ree San CAC Be WR ee oe See eee EM aG 111.06 32.85 Thus it is seen that the unoccupied space in a soil varies from more than half to less than one-third of its volume, the finest grained soils having the largest pore space and the sandy soils and sands the smallest. 134. Pore Space Between Spherical Grains.—It can be shown mathematically that when a space is filled with spheres all of one size and these are given the closest pos- sible packing, having the arrangement shown in the upper part of Fig. 34 and Fig. 35, the pore space must be 25.95 per cent. ; but when the spheres are given the closest possi- ble packing and the arrangement represented in the lower 112 part of Fig. 54 and in Fig. 36, then the pore space must be as large as 47.64 per cent. In the first case the water capacity of such a soil with the pores entirely filled would PIG. 35.—Showing the closest packing of spherical soil grains, the ele- went of yolume aud the direction of lines of flow. Face angles 60° and 120°. (After Slichter.) be 3.114 acre-inches per acre-foot and with the second ar- rangement the maximum water capacity would be 5.7168 acre-inches per acre-foot. Neither of these arrangements would be likely to oceur throughout a mass, and hence the general tendeney will be 113 to form a pore space between these two extremes, and Fig. 37 shows what the observed pore space is in soils, sand, crushed rock and erushed glass. It will be observed that Fic. 36.—Showing the closest packing of spherical grains, the element of yolume, and the direction of lines of flow when the face angles are 90°, 60° and 120°. (After Slichter.) the finest clay soils, and indeed the finest grained materials, have the largest pore space. It will also be noted that the largest observed pore space exceeds the largest theoretical 114 pore space and that the smallest observed pore space also falls below the smallest theoretical limit for spherical grains of a single size. PER CENT. TINE {Sas = INE PER CENT 20 Fic. 37.—Showing the obseryed pore space of different kinds of soils and sands and their relation to the theoretical pore space of spheres of a simple diameter. 135. Amount of Pore Space Determines Maximum Water Capacity of Soil The amount of water a soil may contain when below the level of the ground water surface is meas- ured by the pore space. So too in the case of heavy and protracted rains the pore space determines the number of inches of water which may enter the ground before it be- comes so filled that surface drainage must carry away that which is falling, and it will be readily understood that in the clay soils, where the pore space is so high, very large 115 amounts of water may be stored in them to drain away gradually in the underflow. 136. Subdivision of Pore Space Determines the Rate of Per- colation and Drainage.—If reference is again made to Fig. 54 it will be clear at a glance that water must flow through spaces filled with these different sizes of spheres at very different rates. Where the spheres are largest there are 16 passage-ways for the movement of air or of water; but in the middle section where the spheres have one-half the diameter, the number of passages is 4 times as great, while in. the last section with spheres of one-quarter the size the number of passages is 16 times as great. The aggregate area of the cross-sections of the pores is exactly the same in the three cases, and from this it follows that the areas of the cross-sections of single pores are to each other as 16:4: 1. The coarse spheres divide the column of water into 16 streams, the medium ones divide it into 64 streams, while the smallest spheres divide the column into 256 streams, each having only one-sixteenth the sectional area of the first. But to subdivide the column into 256 streams in- stead of 16 means that the friction must be much greater in the ageregate on the smaller streams, and hence that the flow must be slower. 137. Method of Determining the Pore Space of Soil.— The simplest method of determining the pore space of soil is to pack the dry material into a cylindrical vessel containing 100 ¢. ¢. until it is even full, and then weigh and compute the per cent. of pore space from the volume, weight and specific gravity, using the formula Vd — W Vd et where V is the volume of the vessel in ¢. ¢., d is the specific gravity and W is the weight of the soil in grams. To determine the pore space in undisturbed field soil 116 the simplest method is to use a soil tube, represented in Fig. 38, taking a number of cores of the desired depth, Fo ———— aaa Ra Fic. 38.—Showing soil tube for taking samples of soil. drying them, and then compute the pore space with the formula above. 138. Largest Possible Pore Space.—The largest possible pore space in soils will be found in the cases where the com- pound or kernel-structure is most marked. Referring again to Fig. 34, imagine each sphere there represented to be made up of other very much smaller spheres having the same general arrangement. Were this the case it is clear that in consequence of the compound spheres the soil must have a pore space not less than 25.95 per cent. with one arrangement and 47.64 per cent. with the other. But in addition to this pore space there must be a like pore space within each compound sphere so that in the first case the total pore space would be 25.95 + [25.95 per cent. of (100 — 25.95)] = 45.17 and in the second ease 47.64 + [47.64 per cent. of (100 — 47.64)] = 72.58 per cent. The first pore space, 45.17, it will be seen, les close to that possessed by the finer soils but the latter is larger than anything ever found except it be in the loose mulches. The smallest pore spaces result when grains of different sizes are so related that the small ones fall into the pores formed by the large ones without at the same time crowd- ing them farther apart. Referring again to Fig. 34, it will be seen that if small spheres are packed into the pores there shown, with the same arrangement that the large ones have, the original 25.95 per cent. and 47.64 per cent. 1i7 of pore space would be occupied to the extent of 74.05 per cent. in the first case and of 52.36 per cent. in the second case. Such a condition ead leave only about 6.73 per cent. of pore space for the closest packing. Such arrangements as this are not lkely of course to occur in nature but in the construction of macadam roads and in all concrete work a definite effort is made to reduce the pore space to the smallest possible limit by using erushed rock, gravel, sand and finally cement to fill all pores as completely as possible. 139. Number of Soil Grains per Unit Weight.—If soil erains were all spheres and in a given case they were all of the same size the number in a gram could be found by the equation Weight of soil No. of grains = zd* & sp. gr. 6 where the weight of the soil is in grams and the diameter of the soil grains, d, is in c. m. In the table below are given in round numbers the num- ber of grains in one gram and in one pound of soil, sup- posing the grains all spheres and to have a specific gravity of 2.65 Diameter. Hover eae 11 |No. of grains in one lb, UPEYYG PINs, 5) ic faite tore weisveisiars sicsin sere iets awe 720 326, 903 PRISTER GHEY ese? erasone 3s sais alae cetera Oa lene a ae aie sieloeete 720, 000 326, 903, 000 MORN GTTI Sg INS ice). 25 cise cea cts tale te Oe oe ance ae weer 720, 0C0, 000 326, 903, 000, 000 MpMibre et fle ee id |e 72050000005 000 326, 903, 000, 000, 000 .0001 m. m..................+.2++----+-+|720, 000, 000, 000, 000 | 326,903,000, 000, 000, 000 That is to say, 720 multiplhed by 10 used as a factor 3, 6, 9 and 12 times gives the number of grains in a gram of soil in round numbers and the number in a pound may be found by using 10 as a factor in the same way and the number 362,903. ; If the soil were made up of some grains of all the sizes ‘ 118 in the table, then to find the total number in a gram or pound it would be necessary to multiply those numbers by the per cent. of each size found in a gram of the soil and add the several products. If the soil were made up of 20 per cent. of each size in the table the number would be as follows: Diameter. Per cent.) No. of grains per gram. 144 144, 000 144, 000, 000 144, 000, 000, 000 144, 000, C00, 000, 000 144, 144, 144, 144, 144 140. Amount ef Soil Surface Possessed by a Gram of Soil. —Much of the water retained by soils is held there in the form of thin films surrounding the grains and the larger this surface is the more water may be retained. So, too, the solution of plant food from the erains takes place at their surfaces and the larger the amount of surface the more rapidly the solution may take place. The extent of soil-surface in a gram of soil can be found by multiplying the number of grains by the surface of one grain or by introducing 7d? into the equation of (189), thus: Weight < zd? 6 < weight TO? SOs amp CU SS Elon Gare 6 expressed in square @. m. . Using this formula to compute the surface in one gram of soil grains having the sizes given in the table of (139) the results below are obtained: = soil surface Dinetaeiaeee ee cea Hess gram papee ber pound UU OUND SUM Riss cttesciatcreucvelniarrsiufe-snen nel otatalelseste ele pprletetaietets 22.64 11.05 SMI MN fares co esa eco scleyss cs oeaitee ciate See ae atl ere tense 226.41 110.54 SOD ee AES RE oateorntes ac oe careers eee oe ete iets 2,264.15 1,105.38 OOD SMe Rae cca vc Gore ches isiae cee ee reettetias 22,641.51 11, 053.81 S000 Tims Sereceee eos ee een eee ees 226, 415.14 110, 538.16 119 It will be seen from this table that the internal surface of an ideal soil increases in the same ratio that the diam- eter of the grains decreases, that is, reducing the diameter one-half doubles the surface to which water may adhere and upon which it may act. 141. Difficulties in Determining the Surface of a Soil Accu- rately.— While it is possible to determine accurately the surface in a given weight of spheres of known dimensions the case is quite different with true soils. Indeed, it is not practicable to determine with much accuracy the sur- face in a soil. This will be clear from a consideration of a simple problem. Take a soil composed of grains, (a) .009 and (b) .00015 m. m. in diameter and let these be mixed in the propor- tions of 90 per cent. of (a) with 10 per cent. of (b). 10 per cent. of (a) with 90 per cent. of (b). . 950 per cent. of (a) with 50 per cent. of (b). OmP Under these conditions the surface of one gram of such mixtures of soil having a specific gravity of 2.65 is For A. Surface. 90 per cent. of grains (a) .009 m. m. diameter ........... 2,264 sq. cm. 10 per cent. of grains (b) .00015 m. m. diameter ......... 15,094 sq. em. Motalisuniace acess cos: Mateta mielaanaeie sana leicteisivecintes 17,358 sq. em. For B. 10 per cent. of grains (a) .009 m. m. diameter............ 251.6 sq. em. 90 per cent. of grains (b) .00015 m. m. diameter...... ... 135, 848.9 sq."em. opalasurtaceaecwssnce hie one weer ations 136, 100.5 sq. em. For C. 50 per cent. of grains (a) .009 m. m. diameter............ 1,258.0 sq. em. 50 per cent. of grains (b) .00015 m. m, diameter.......... 75, 481.7 sq. em. MOGAISULLA CE aAstreaicsteaciir aa omnes docee acaes Gn ag. SQecmn. 120 The number of grains in one gram of each of these m1ix- tures would be as given below: A. B. C. (ED) masaaa ceodoudoosoodade 889, 753, O61 9&, 861, 363 494, 306, 828 (10) "us Goan seu soon puooosbe 21, 354, 187, 192, 118} 192, 188, 053, 097,345) 106, 770, 833, 333, 333 Mofalleern ance ccer 21,355, 076, 945, 149 1921 188, 151, 958, 708| 106, 771, 327, 640, 151 It is the custom to find the diameter of soil grains either by direct measurement or else by counting and weighing a given number of grains and then computing the diameter of the mean grain from the weight and specific gravity. If the diameter of the mean grain in the above three problems is computed by each of these methods the results will be as below: If the surface of a gram of soil is computed from each of these diameters the results given below will be found: A. B. C, sq-cem. | sq. cm. | sq. cm, Actual surface per gram of soil.. peas) clvinettss 136, 101 76, 740 Surface computed from the grain of mean diameter 150,570 150, 939 150, 902 Surface computed from the grain of mean weight..) 10,053 145, 734 119, 804 These results are very different and differ so much from the actual as to make them of little value in determining the actual surface a given soil may possess. it has been the practice to take as the mean diameter of the soil grain the average between the diameter of the largest grain in the group and the smallest, which in the above problem would give .004575 as the mean value. But to use this to compute the surface in a gram of soil would give the results below: Computed from the mean of the two extreme diameters. Ne Computed from the true diameters in true proportions. B. C. 4,949 sq. cm. 17, 358 sq. em. | 136,101 sq. em. 76,740 sq. cm. 121 Here it is seen that the computed surface, 4,949, 1s very far indeed from either of the true values given under A, B and C. 142. Effective Diameter of Soil Grains.—While it is not possible to determine either the mean diameter of the erains in an ordinary soil or the amount of surface a given weight of soil may possess with even approximate accu- racy, it is possible for the simple sands, at least, to deter- mine the diameter of @ grain which, if substituted for the actual ones, would permit, under like conditions, the same amount of air or of water to flow through. The method is based upon the laws of flow of fluids through capillary tubes and aims to compute from the ob- served rate of flow of air through a given column of soil the effective diameter of the capillary pores and from this the size of spherical grains which would be required to form such capillary tubes as those computed. The theory of the method is fully set forth in Prof. C. S. Slichter’s paper." 143. Description of the Method.—The apparatus used to determine the effective size of soil grains is represented in Fig. 39, and consists of a cylinder in which a sample of soil is carefully packed and weighed to determine the per cent. of pore space. When this has been done the tube is connected with the aspirator and the rate at which air will flow through it under a measured tempera- ture and pressure found. When these data have been ob- tained, then the formula below, used with the table given, enables the effective diameter to be computed when the flow has been measured at the temperature of 20° C. 1 Nineteenth Annual Report of the U. S. Geol. Survey, Part II. h sot _-(8.9434 — 10) where d = diameter of grain in c. m. h = length of sand column in ec. m. s = area of cross-section of sand column in sq. c. m. p = pressure in c. m. of water at 20° C. t — time in sec. for 5,000 c. c. of air to flow through at a tem- perature of 20° C. [8.9434 — 10] is a logarithm of a constant k is a constant taken from the following table. Fic. 39.—Showing aspirator for determining the mean effective diameter of soil grains. A, aspirator bell; B, pressure gauge; C, air meter; D, aspirator tube for samples. Per cent. of pore Per cent. of pore space. Log. k. d. space. Log. k. d. 1.9258 563 SUikcdtivecn cme xe 1.4193 377 1.8695 500 BOmeisemiaie es eren 1.3816 371 1.8195 450 OO a stele KASEI Rew e's 1.3445 367 1.7701 502 40 iiascueaits 1.3078 353 1.719° 467 AN ettat re ceva corer 1.2725 351 1.6732 455 ADs rele cocretonsis 1.2374 345 1.6277 430 AS raatoarevenveela’s 1.2024 339 1.5847 438 MAK Se Oe eraits,atorers 1.1690 320 1.5409 410 PSA aie Cement 1.137¢ 312 1.4999 407 AG Peers as6 ates 1.1058 329 1.4592 400 Boe cadiats eeeaces iy Ave * 2 bamedesees == —————es 144. Observed Flow of Water Through Sand Compared With That Computed From the Effective Diameter.— The ac- curacy of the method deseribed in (148) is best shown by computing from the effective diameter of the soil grains what the flow of water ought to be and then measuring the flow of water to see how it corresponds. This has been done and the results are given in the table below: Effective Grade of sand. diameter of Computed Observed grain. flow of water.|flow of water. m. m. Gms. Gms. Ee ata ate clot ane a ete roniciol che e. o's pierlwiale(ela sjecs 2.54 2,277 2, 296 RRA Sas ape te tee neeemeina) Baws 1.808 1,132 1,080 ered resin cn oicis ee aici bale teie saci: wis 1.451 757 756 AEG SER ERE RODD BOC TAICECE BOSC AoC me 1.217 522 542 Pye eee IRL Res DN Nea More chacseaeinte 1.095 453 2 504.6 MME ee Na ane ae cole seis eawTaCers .9149 297.5 329.2 Don CBE E OOD SEOs oD RO COde DRC OCC ILIAC . 7988 193 210.0 DEN SMe SEN cats ate ae Dalelste theievaia: aisle 7146 122 138.6 1 chico PBL ROSE ORT Cle TC CO SEs 6006 80.6 94.8 CMa Ne Sele afcci smile utamaniae evareye ares 5169 66.8 72.3 When it is observed that the effective diameter of the grains in these sands was found by measuring the flow of air through one sample in one piece of apparatus and the flow of water was measured through another sample and in another piece of apparatus, and that the flow varies as the squares of the diameters of the soil grains, it is clear that the effective diameter has a very exact value so far as the flow of fluids is concerned. 124 145. The Effective Diameters of Soil Grains and the Amount of Surface Computed From Them.—We have no means of knowing yet how accurately the computed sur- face of soil grains in a given weight of sample compares with that which is p »ssessed by it. We do know, however, that the comparison is accurate enough to furnish a valua- ble basis for comparing different types of soils, and in the table which follows is given the effective diameters of sev- eral kinds of soils, together with the pore space and the computed amount of soil surface per cubie foot of dry soil. Table of computed surface of soil grains in different types of soil. 2 Effective Per cent. |Surface of soil Kind of soil. diameter of of grains in soil grains. pore space. jone cubic foot. m.m. Sq. Ft. Hinesticlayusoua a. sa.ce es otceeee eens .004956 52.94 173, 700 Famerclay esOllasasensoancen ato aoe. .0U7657 45.69 129, 100 Mineiclalysoilann semen eee ee ea eee 008612 48.00 110, 500 Heavy red clay soil. Boe totals OL 44.15 91, 960 Moamiy elayssoile ee ae ee eee 02542 49.19 70, 500 Clavey loam ccer sae cee -OL810 47.10 53, 490 loys Neha ea EM OBA Senen aaa Rees .02197 44.15 46,510 d DOF (eaten ee ieen nee rad Hcknom ee ae ola con .02619 34.49 45, 760 Sandy OEM ae Re ee .03035 38.83 36, 880 Sand yasoilieve soto eee ee .07555 34.45 15, 870 Sandy soil . ; ioe te idwsiee teres ats 1119 32.49 11, 030 Coarse sandy soil. . eS oh ee ah care . 1432 34.91 8,518 It will be seen from this table that the amount of surface in the true soils is indeed very great, ranging from a little less than a quarter to more than a third of an acre in the sandy soils, through more than an aere in the loams to as much as four acres per cubic foot in the finest clay soils. The amount of soil surface in the upper four feet of every cultivated field ranges from not less than one acre to more than 16 acres per each square foot of surface cultivated. 146. Relation of the Surface of Soil Grains to the Water arge portion of the water held by a soil is spread out as a thin film surrounding the soil grains and it 125 is generally true that the larger the surface of the soil grains the more water the soil will retain. If a marble is hfted out of water it retains a film sur- rounding it and its surface is wet; so if rains fall upon a sand or soil surface until percolation takes place, there is held back upon the grains a certain amount of water which is characteristic of or peculiar to each type. It is clear that a soil whose internal surface is 4 acres per cubic foot may contain a large amount. of water even though the film is extremely thin. In an acre there are 43,560 sq. ft. and in four acres 174,240 sq. ft. The thickness of a water film on this surface sufficient to equal 4 inches on the level per square foot of soil would be 4 1 174,240 ~~ 43,560 of an inch or one-half the thickness of the film of a soap bubble when it becomes yellow just before appearing black and breaking, from thinning out. This thickness is also about { the di- ameter of the soil grain itself. In the case of a fine sand having grains .O8188 m. m., which retains, after complete drainage 8 feet above stand- ing water, 3.44 per cent. of water, the film would have to have a thickness of only about «+s of the diameter of the grain, and when containing 20 per cent. of its dry weight then the film need have a thickness of only about +r of the diameter of the sand grains, that is, .0072 m. m. It is clear, therefore, from these considerations that the surface of soil grains has much to do in determining the water-holding power of a soil and that the films may be very thin and yet on account of their great extent represent a high per cent. of the soil itself. 147. Movement of Air Through Soil.—There is perhaps nothing which shows how physically different the fine and the coarse grained soils are as clearly as the rates at which air will pass through them when dry, and in the next table some of these are given. 126 It will be seen from this table that when the grains are so large that 10 of them will span a linear inch only 37 seconds are required for a pressure of .1 foot of water to force 5,000 ¢. ¢., 5.3 quarts, of air through a column a foot long and .01 of a square foot in cross section; but in the finest clay soil, which makes the best grass land, where 5,125 grains must be set in line to measure a linear inch, then the time required is 2,933,000 seconds for the same amount of air under the same conditions to be forced through, a ratio of 37 seconds to 45 days. Table showing the differences. in the rate of movement of air through gravel, sand and soils of different types when the columns are 1 foot long, .O1 ft. in cross section and under a pressure of .1 ft. of water. —_ : No. of seconds No. of grains| Per cent, for 5,000 c. ¢ Description of material. per of of ain to flow linear inch. | pore space. through. Fine gravel, grade No. 8................ 10. 37.60 37 Fine 2ravel, Erade NOs Uae. cas ceeds sc 14.0 38.44 7 Fine gravel, grade No. 6................ 17.5 38.85 99 Fine gravel, grade No. 5.5.............. 20.6 39.26 138 Coarse sand, grade No. 5. ot ancnene 24.3 39.88 184 Coarse sand, grade No. 4. Bre re ee 27.8 38.53 260 Coarse sand, grade No. aoe Do cieiels Buctahntee 31.8 36.26 416 Coarse sand, grade No. 2............ - 30.0 34.66 €12 Medium sand, grade No.1.............. 42.3 34.43 869 Medium sand, grade No. 0.............. 49.1 34.42 1,178 Fine sand, grade No 60................ 143 34.20 10,370 Fine sand, grade No. 100............... 310 35.32 44,310 @oarseisandy SOU, wonnce caeeececenees 177 34.91 14, 580 Sandy Sols doccuseeetes cawaueseeuaee 227 32.49 30, 460 Sandy solar dersit cevcarcmn asters 336 34.45 54,910 Bandy oan. eanceiie ete nateiccs area ateioteieere 837 38.83 227, 400 Coarse loan «iki ic.ccccicioe cle across /eisisiestrrese 970 34.49 45, 750 GORI Sacre cele ncehsisaits Gn coe cua lo ere ita orate 1,156 44.15 252, 200 Clayey loam \-tacchn roteneoatcese saoeuer 1,403 47.10 476, 600 Loamy clay.. Bye Wikis sicker Ciencis oteaaeete 1,647 40.19 804, 600 Heavy red clay Protege: Reais Sar Mh © OP 2, 286.0 44.15 1,129, 000 Clay sol So. Jacce ne sano a ose neato 2,949.0 48.00 1, 412, 000 Minerclay soll Mic ce acocestosusiesmece 2,310.0 45.96 2,057, 000 Minesticlay (soils ccwanccteeesaeenmon. 5, 125.0 52.94 2, 933, 000 It should be understood that this slow rate of movement of air through the finest clay soils was observed when the air-dry soil had been pulverized in a mortar and made as fine as practicable before packing into the aspirator. Un- 127 der field conditions, as has been pointed out, a good clay soil has its clusters of various sizes and there are passage- ways of various sizes and forms which allow both air and water to move much more freely than has been recorded in the table and if it were not so plants could not thrive in them. 148. Permeability to Air of Undisturbed Field Soils.—The rate at which air may flow through soils in their natural condition, in place in the field, may be readily studied with an apparatus such as is shown in Fig. 40. When the soil tube A is driven into the ground to near the depth at which the flow of air is to be measured it is recovered, the core of soil re- moved and the tube returned to—— its place, when the aspirator is connected as shown in the cut, and the time required for alii": given volume of air to be drawn pyg. 40— Showing appasatus for through determined. In_ these agar cone dnth poem ee Dea te field studies it will be found Sil is removed to the desired that the dryer the soils are the more freely air passes through them but that when they are saturated with water, as just after heavy rains, little or no air will pass through them even under a pressure of 12 inches of water. COTTA ULELLUPLLROPUNLEE gg 149. Weight of a Cubic Foot of Dry Soil.—A eubic foot of undisturbed air-dry soil varies in weight between quite wide limits, the humus soils being the hghtest, and the coarse sandy soils the heaviest. The writer has found a dry soil to have the weight per cubic foot given in the table be- low: pee bo D Ist foot. | 2d foot. | 3d foot. | 4th foot.| 5th foot.| 6th foot. Pounds per cubic foot 79 92.62 104.59 106.21 111.06 111.06 Pounds per acre...... 2, 740, 000) 4,034,000] 4,557,000) 4,637,000} 4,840,000} 4,840, 000 Shubler gives the weight of a cubic foot of dry soil as follows: Dry calareous or siliceous sand .............. 110 lbs. Hallitsandsand shalt: claiyinns acter eteereniciraeceraere 96 Ibs. Conimonfarablescoiliepc. cee ere 80 to 90 lbs. Heavy clay wihigs siswaes 22 cake oes a ines sar ay lO Se Garden mould rich in vegetable matter ...... 70 lbs. Pe atyseill ea eee ere oe crests thc ese Miva ce aie rote 30 to 50 lbs. As a number easy to remember it may be taken as a safe figure that the mean weight of the surface four feet of field soils is, in round numbers, 4,000,000 Ibs. per acre- foot. 150. Heavy and Light Soils.—These terms are used more with reference to the ease with which soils may be worked than to their weight per cubic foot. A soil that is nat- urally mellow and easily stirred is called a light soil, while one that becomes hard when dry and which tends to form clods is often called heavy. Sandy soils, as shown in (149) are among the heaviest we have while the clayey va- rieties are the lightest by weight except the humus types. The prairie loams which contain much humus and the black swamp soils when drained are among the most mellow of all soils, the large amount of humus preventing the soil erains from adhering and baking. CHAPTER. V. SOIL MOISTURE. 151. Occurrence of Moisture in the Soil.— For purposes of discussing the cultural relations of soil moisture water may be said to occur in the soil under three conditions : (1) That which fills the pore spaces between the soil grains and is free to move under gravitational or hydro- static pressure and may be called gravitational or hydro- static water. (2) That which adheres to the surfaces of soil grains -and to the roots of plants in films thick enough to allow surface tension to move it slowly from place to place, and which may be ealled capillary water (3) That still retamed on the surfaces of soil grains when they become air-dry; whose chief movements are those of evaporation and condensation and which has been designated hygroscopic moisture. rater in a goil in- creases in quantity suffice iene to move dooce vate r the pull of gravity it may be harmful in three wa (1) by pete out the soluble plant foods, thus jest the soil poor; (2) by excluding the air and thus causing suffocation of i roots of plants and micro-organisms living in the soil; (3) by preventing surface tension and by dissolving cementing materials, thus destroying or reducing the gran- ulation of soils, injuring their texture. It may be helpful in two ways: (1) by replenishing the eapillary moisture when this has become too small to enable cro ps to supply themselves, and (2) by washing out and carrying away sol- uble substances whic ‘h, if allowed to accumulate, become in- 150 jurious, such as black alkalies and possibly toxic principles developed by the roots of plants or soil organisms or during their decay. 158. Capillary Water.—It is in this condition or quantity in the soil from which crops and soil organisms chiefly de- rive their supply of water, and the right amount at all times is therefore very important. It is in the capillary water, too, that most of the plant foods derived from the soil are held in solution and with it moved to the plants as needed. When the texture of the soil is right the capillary water simply surrounds the soil grains and soil granules as a thin sheet which is continuous where the grains are nearly or quite in contact, but there are always open spaces through which the air may circulate and supply the needs of roots and soil bacteria. Tf the soil is puddled and the granules broken down then the surface films on the smaller soil grains come so nearly in complete contact that there is insufficient room for air to diffuse and plants cannot thrive in it. 154. Hygroscopic Water.— Moisture in this form possibly plays an important part in the actual solution of plant food from the soil and fertilizer grains because it is this portion which hes in immediate contact where the action must take place; but if this is true it can only do its work rapidly when capillary water is also present to carry away from the dissolving surfaces the products which are being formed. Polished surfaces do not as readily rust as those which have become tarnished or otherwise roughened. When a steel knife blade has become a little rusty the rusting then goes on much more rapidly, possibly because each particle of rust becomes invested with its film of hygroscopic mois- ture, and when these lie against the fresh metal the water can have a greater thickness and permit a more rapid move: ment of the compounds formed, away from the corroding surface. It is not probable, however, that the hygroscopic mois- ture of a soil can in any direct way aid plant growth. 155. Ways of Expressing the Water Content of Soils.— The amount of water a soil will or may contain has been ex- pressed in different ways: (1) As a per cent. of the wet weight of the soil, (2) as a per cent. of the dry weight of the soil, (3) as a per cent. of the volume of the soil, (4) in pounds per cubie foot, (5) in inches per cubie foot. The amount of moisture a soil does contain may be most readily and precisely stated as per cents. of the wet or dry weight, but for agricultural purposes it is best to state the amount in per cent. of the volume or in inches per cubic foot. 156. The Maximum Water Capacity of Soils.—The largest amount of water a soil may contain is expressed by its per cent. of pore space and if reference is made to the table in (145) it will be seen that this ranges from about 32 to more than 52 per cent., that is from 4 to 6 acre-inches per acre- foot of soil, and from 20 to 32 lbs. per eubie foot. These amounts of water, however, are never found in soils under field conditions. 157. Water Capacity of Soils Under Field Conditions.— The amount of water which may be retained by soils under field conditions is extremely variable and depends upon a number of factors. In the table below are given the amounts of water which were found in three types of soil with the undisturbed field texture, when they contained as much as they would retain after a few days of drainage fol- lowing heavy rains. Capacity of field soils for moisture. Depth. Sandy loam.| Clay loam. | Humus soil. Per cent. Per cent. Per cent. St LOG Gisentt cece sce tas.c fe Se ccealsees Nae 17.65 22.67 44.72 NOCOUMSLOG tae ctgen at entre trae sels aticetclene es 14.59 19.78 31.24 SBRITAIEGD bees cases cy Stecree oe Retin ne oe cer 10.67 18.16 21.29 132 In this table the third foot in each case is more or less sandy and for this reason shows percentagely less water than the soil above. It will be seen that the surface foot of sandy loam contains the smallest per cent. of water and the humus soil the largest, but on account of the differences in dry weight of these soils their water contents are more nearly equal than they appear, the sandy loam containing about 16 Ibs., the clay loam 18 Ibs. and the humus soil 26 Ibs. per cubic foot. Expressed in inches the amounts stand 3, 3.5 and 5 inches nearly. 158. Maximum Capacity of Undisturbed Field Soil.—In the table below are given the amounts of water which com- pletely filled the first five feet of undisturbed field soil, as determined by driving 6-inch metal cylinders one foot long into the soil and, recovering them, covering the bottoms with perforated covers and then placing the cylinders un- der water until the pores became completely filled. Table showing maximum capacity of undisturbed field soil for water. Kind of soil. Depth. eREeenS inchese Claveycloatin caus. secs es nek eee ASG LOOts.< moe cops scisie 43.3 5.88 Reddishicl ates sek sec eeweeceeeene AA MOGUL sa naeeeecrneeers 28.1 5.03 Re didishiel aye cases ccteemceictenr aes SOQTOGUG aco. he vee cence 28.4 5.07 Glayswithisand et ecsacuss sees Ath fOOtan seen cone ee 24.8 4.67 WeLny finesand aston eae stae ae Sane FEN OOteS wae eaieean ss 17.4 3.76 MepBalhen teenies fos ss Pe ees Al Sach Dee Pee eet eee 2b In this case it is seen that two feet out of five feet of the soil was open space which could be oceupied with water. 159. Maximum Capillary Capacity of Soils for Water.— The amount of water which may be retained in soils by eapillarity is greatly influenced by the distance of the soil above standing water in the ground and by the frequeney and amount of rainfall. The evlinders of soil referred to 155 in (158) when thoroughly dried and then placed in one inch of water in a chamber where no evaporation could take place, took up and retained by capillarity the follow- ing amounts of water: Table showing the maximum capillary capacity for water of jield soils with the surface 11 inches above standing water. bs. of Per cent. abs: eae Inches of of water. cu. ft. water. Surface foot of clay loam contained........... 32.2 23.9 4.59 Second foot of reddish clay contained......... 23.8 ape) 4.26 Third foot of reddish clay contained.......... 24.5 PRN 4,37 Fourth foot of clay and sand contained....... 22.6 22.0 4.25 Fifth foot of fine sand contained .............. 17.5 19.6 3.77 ROCA eet eee iacee else rode uerarecibloaiaciossallt | miki saes 110.5 21.24 ) O A | ! | SIMI BIR Ie) gay WAM Ss = —_ Sto Fic. 41.—Apparatus for measuring the capillary capacity of long eolumns of sand. It is clear from this table and the last that much of the pore space in the clayey soils cannot be maintained full of water by capillarity even when the surface is only 11 inches above standing water. 8 134 160. Influence of Distance Above Standing Water on the Water Capacity of Soils—When the distance to the ground- water is considerable the force of surface tension is not ereat enough to maintain as much water in the soil as when the distance is less, and the table which follows shows how the amount of water retained varies with the distance. The sands and soils were placed in an apparatus represented in Fig. 41, arranged so as to permit free percolation but allow- ing very little evaporation from the surface. The sand columns were 8 feet long and percolation was allowed to continue nearly 2.5 years. The soil columns were 7 feet long and percolation from them was continued during 60 days, at the end of which time the tubes were cut into short sections and the amount of water still retaimed determined by drying. Percentage distribution of water leftin columns of sand, sandy loam and clay loam after percolation had continued two and one-half years with the sand and 60 days with the soils. Height of section above} Sand | Sand | Sand | Sand | Sand | Sandy | Clay ground water. No. 20.| No. 40.| No. 60.| No. 80.|No. 100.| loam. | loam, Inches. Prcu » ct.||Pr-et.| Pricts| Pre ctaPry ct. beset. 0.17 0.22 1.26 by © el eames isassiocc 17 .23 1.16 5 pr: a IRA 5a Se .cisoao .16 .29 1.34 SiB25,| dois selene eee 15 4g74 i 61 OOM | closers te stel] ereeeeee 18 61 1.98 3.93 16.16 21.16 9) 1.07 2.02 A MO's\| se ceararererel| terreno .26 1.33 2.61 4.35 16.08 30.70 .58 1.57 2.90 492) lls, ee /0.01| noe 1.16 1.80 3.12 4,94 16.55 31.05 1.45 1.85 3.36 Bi MOn|\Seccnee aalleteeeee 1.67 2.03 3.56 5.91 16.97 31.11 1.80 2.18 3.92 6.43! on. cosa beeen 1.86 2.26 4,22 6.77 17.59 31.21 1 87 2.21 4.53 id | Bose sertel eee 1.98 2.30 4.88 8.59 17.99 31.94 1392 3.33 5.42 42.523 Seneall aces 2.12 2.46 6.03 10.50 18.70 31.99 2.07 2.71 6.99 ah US Be Ree Maaco S.- 2.18 3.08 TAT 12.58 19.44 32.18 2.29 3.46 8.71 T3200" is. ./ar< avec | eee 2.48 4.10 10.54 14.95 20.90 32.45 2.65 5.09 11.77 15200 || \c00s tees eee 135 This table shows very clearly that the amount of water a soil can retain by capillarity is very materially influenced by the distance it is above the zone of complete saturation or of standing water in the ground. The decrease of water upward is most rapid’ in the coarsest sand and it is least ‘apid in the finest soil. It is remarkable that in sands so coarse as those used water should continue to drain away during more than two years from so short a vertical column and that so small an amount of water was retained in the upper sections of the columns. It is not probable that drainage had become complete from the two soils although it may possibly have been, as there was no percolation during the last five days of the trial. : 161. Proportion of Soil-Water Available to Crops.— Not all the water which soils will retain is available to plants. root-hairs. e, main root; 1, air space; 2, soil grain; 3, film of water; h h, root-hairs. (After Sachs.) as to leave them and the soil granules surrounded by the water film. Each root hair is or should be in a sense under water, that is invested in a film of greater or less thickness. When a portion of this water enters the root hair and passes on into the root and up to the leaves, the water layer surrounding the root hair is left thinner; but no sooner does this thinning out oecur than the equilibrium is de- stroyed and surface tension at once squeezes more water onto the surface from the surrounding soil. In this way capillarity keeps the water moving to the root hairs as they pass it on to the plant. 182. Advance of Roots through the Soil.—Until the method by which roots advance through the soil is under- stood it is difficult to realize how it is possible for such deli- cate structures to set the heavy soil aside sufficiently to reach the great depths they do. Nature’s method of over- coming the difficulty is simple enough and it is as effective asitissimple. The large amount of open space there is in the surface four to six feet of soil makes it easier to set the 149 soil aside, and the setting of fence posts proves how large this space is. A 6-inch post set in the hole dug for it seldom occupies so much of the space but that all of the soil re- moved may be returned by thorough ramming. It is the existence of such large amounts of open space in the soil which makes the movements of water, air and roots through it possible and the absence of it which makes a puddled soil so uncongenial to plant growth. Bic. 47.—Method by which root-hnirs advance through the — soil. (Adapted from Sachs.) In Fig. 47 is represented a section of the tip of a root growing and advancing through the soil. It has been found that at 1, a short way back from the tip, there is a center of growth. Here new cells are forming by division and subsequent enlargement. On the forward side of this cell the new ones build the root cap, which acts as a shield and wedge, while those in the rear are finally transformed to make the various structures found in the root. At the center of growth new cells are forming and ex- panding under the intense power of osmotic pressure and, as the root is anchored behind, the root cap is pushed for- 9 150 ward and wedged sidewise, setting the soil aside and thus making room for itself. The root cap does not slide for- ward past soil grains but is anchored rigidly to them; the tip entering existing cavities 1s enlarged by growing on ward under and through the cap, the rear cells of which die ane the reot has grown past them, the root cap being a sort of point continually renewed as the root advances. 183. The Extent of Root Development of Corn.—It is only by careful study that the extent of root development in a soil can be learned. In Figs. 48 and 4 are shown the amount and distribution of corn roots at two stages of growth. When the corn was 30 inches high the whole of the soil to a depth of two feet was as full of roots as the engraving shows between the two hills; when the corn was coming into tassel the roots had penetrated to a depth of three feet and had come closer to the surface; and at ma- turity the roots had reached four feet in depth, making their way. through a fairly heavy clay loam and clay sub- soil, the fourth foot only being sandy. Tt should be understood that the roots here shown grew in undisturbed tield soil and were obtained by going into the field at the stage of growth shown and digging a trench around a block of soil a foot through and the length of the width of the row. The cage was then set down over the block; wires run through the block of soil to hold the roots in place and then the soil washed away by pumping water in a fine spray upon the block. Three days’ work for two men were required to secure the sample in Fig. 49. 184, Extent of Root Development of Grain.—In Fig. 50 is represented the depth to which the roots of winter wheat, barley and oats penetrated a heavy clay soil and subsoil. The roots are what were found in a eylinder of soil just one foot in diameter and were obtained by driving a cylin- der of metal four feet long its full depth into the soil and then washing the dirt out of it. It will be seen that in each ‘ase the roots have reached a depth of fully four feet. 11 weg: Ron i woe Fok % re, 30 y f ory Vein Mig LEAS GENT, SOX, px iA ‘fp Lh ie Te Mahe | Oat Med Fy KS a) pe OE beh At ses ee ee EP Jo Se seg Fic. 48.—Showing amount and distribution of corn roots under natural field) conditions. eas apn es a Se EE Be: ors a © and distribution of corn roots under natural amount 49.—Showing Ira. field conditions. 10 5)c5) Barley. Oats. Wheat. .—Showin eylinder of soil in one foot in diameter, extending to a depth of four feet. field the found roots of amount fia 5 50) 154 Fic. 51.—Showing the total root of one hill of corn. ‘ : ta Be & : Fg = ef 8 ee ae es = ae : ‘ ie com : - ri ‘3 a 2 . fe apt SieED sls Sicdalsiaishae 52.—Showing total roots of oats. ! } | ' | | iy clove dium roots of me g total howin Ss 157 The coarse branches shown with the winter wheat roots are the roots of a red oak tree which was growing in a pasture 33 feet away, and they serve to show how far forest trees send their roots foraging through the soil for water and food, and through w hat long lines the water must be pumped after it has been gathered. 185. The Total Root of Plants.—In the preceding sections the samples simply show the amount of root found in a given volume of field soil. In Fig. 51 is shown the total root of four stalks of corn, while Figs. 52 and 53 show the same thing for oats and medium clover. ‘These were se- cured by growing the plants in cylinders 42 inches deep and 18 inches in diameter, filled with soil. When the crops were mature the cylinders were cut down and the soil washed away. In each case the roots extended to the bottoms of the cylinders, forming a dense mat there, as the engravings show. The roots shown with the clover, and which gathered the moisture for the top, forced from the soil water enough to cover the space to a depth of 29 inches. It will be seen that the stand of clover is very close, fully three times as heavy as a good clover crop in the field. This was made possible by having a rich soil and supplying all the water the plant could use at just the right time. The length of all these roots is less than it would have been had the eylinders been deeper, as proven by the mat- ting at the bottom. 158 CHAPTER VIL. MOVEMENTS OF SOIL MOISTURE. 186. Types of Soil Moisture Movement.— he moisture which is found in the soil above the surface of the ground water is continually subjected to three types of movement : (1) Gravitational, (2) Capillary and (3) Thermal; the first due to the action of gravity, the second to surface ten- sion and the third to heat. When rain falls upon the soil one portion of it begins to flow vertically downward through the pore spaces, urged to do so by the pull of gravity; a second portion increases the thickness of the water film surrounding the soil graing and root hairs and is made to do so by surface tension ; while a third portion is returned to the atmosphere through evaporation, caused by heat. GRAVITATIONAL MOVEMENTS. 187. Percolation of Soil Moisture.—The direct gravita- tional flow of soil moisture, which oceurs during and after rains, is nearly always vertically downward until. the ground-water surface is reached. The movement takes place chiefly through the shrinkage cracks and _passage- ways left by the decay of roots and the burrowing of ani- mals, but also through the capillary pores formed by the grains of the coarser soils and by the granules of the finer types. The rate of movement is most rapid following heavy rains when the soil is already well saturated. After pro- longed periods of drought, when the soil has become very dry, there is so much air in the pore spaces that it greatly 159 impedes percolation except in those cases where wide shrinkage checks and cracks have resulted. Where percolation is influenced chiefly by soil texture it is most rapid through the sandy soils and the more granu- lated clay types. It is least rapid through the puddled clays. 188. Rate of Percolation Through Sands.—\WVhen the sim- ple sands are once completely filled with water the pereo- lation from them is quite rapid but decreases with the size of the sand grains. In the table below is given the amount of water which percolated from the columns of sand referred to in (160), Table giving the rate of percolation from sands under the gravitational head of the inclosed water. ; AMOUNT OF WATER PERCO- : 4 Effective|Per cent Weight LATED IN— GRADE OF SAND. |diameter| of pore | Of sand |— ae ==! 2 f grain.| space, |per & cu- ‘ 4 3 Pore ere bic feet, | First 30 min. |Second 30 min. m, m. Pounds.| Lbs. |Inches.| Lbs. |Inches. Niguel oaaceteuacos|) .OraT4do 38.86 809,28 53.33 | 10.25 24.26 4.683 INGOM AO Ss citocaetscttee acs .1848 40.07 793.28 39.27 7.549 27.35 5.258 ASO MOUs cteis)ole cicteis\'steters 1551 40 76 784.00 29.99 5 674 23.52 | 4,522 INO eae sovaonieio eerie .1183 40.57 786.64 7.86 1.512 6.73 1.294 von Wh aoeasaaboesee .08265 39.73 797.76 6.31 1 213 4.40 | B45 It will be seen from the above table that the rate at which the water moved downward through the coarsest or No. 20 sand was such as to average during the first thirty minutes 492 inches per twenty-four hours, while for the finest or No. 100 sand the mean rate was 58.16 inches, the flow from the first being nearly 8.5 times as fast, with grains not quite 6 times as large. After the end of the first nine days of percolation these coarse sands lost about 1.7 per cent. of their dry weight in each case, or only about .33 of an inch. 189. Rate of Percolation from Soils.—The percolation of water from the sandy loam and from the clay soil, given 160 in the table of (160), when the eight-foot columns were completely full of water at the start, took place at a much slower rate than from the sands, as indicated in (188), the rates being Sandy Clay loam. loam inches, inches. BUNS GAL SOULS) Vacteieree bc kin ptekcu lin cree Be ele Maat shinee tees BORON "lone tresses PITSb SS TOUCH cis wre sierock bie ates Ce line ence ait ae alsa rietene Pare Ruled ears 1.958 Binsploidavae following the BOOver. secure: nuicstc sieeie nae 5.072 2.111 Second 10 days following the above................ sesceee 905 493 TotalAnaboubielrda vs cancmscteiss cose ronan seis sist cosiercle 8.617 4.562 The rates in these cases were such that more water per- colated from the three coarsest sands during the first 30 minutes than from the clay loam in as many days; and yet the loam contained at the start the largest amount of water. It is clear from these differences in the rate of percolation why the sand could not be productive under ordinary con- ditions of rainfall, no matter how much plant food it might contain. It is clear also that fineness or closeness of tex- ture is one of the most important qualities of a good soil, for without this the water drains away so rapidly that, with the ordinary intervals between rains, not enough could be retained for the needs of crops. 190. Percolation Through Dry Soil.— When soils have be- come relatively dry, as happens especially during the mid- dle and later summer, water does not percolate into them as readily as it does in the spring when the pores are more nearly filled. When the volume of air in the soil is large, and when the films of water surrounding the soil grains are very thin, the flow downward past the air is very slow. Tt is on this account, in part, that the lighter rains are less effective in midsummer than they are in the spring, the water being retained close to the surface where it is quickly lost by evaporation. iILGal CAPILLARY MOVEMENTS OF SOIL MOISTURE. The capillary movements of soil moisture are relatively slow, when compared with those of percolation, and are slower in dry than in wet soil. The general tendency of capillarity is to bring water to the surface from varying depths, but its movements may oceur in any other direction, the flow being always from a soil where the water films are relatively thick toward those where they are thinner, or from the wetter toward the dryer soils. If the roots of plants have made the soil dryer in their immediate neighborhood capillarity may carry water to them from below, above or from either side. When heavy rains follow a dry spell then capillarity will assist gravity in carrying the water more deeply into the ground; and when water is applied by the furrow method in irrigation capillarity carries it laterally away from the furrows. 191. The Rise of Water in Capillary Tubes.—When a clean glass tube whose bore is small and wet is held verti- cally in water the liquid rises to a certain height above the level outside, the amount varying with the diameter of the tube, as given in the table below: In a tube 1. inch in diameter the water raises —_.054 inches. Inatube .1 inch in diameter the water raises .545 inches. Inatube .01 inch in diameter the water raises 5.456 inches. Inatube .001 inch in diameter the water raises 54.56 inches. That is to say, reducing the diameter of the tube one-half doubles the height the ee may be raised by ecapillarity, and reducing the diameter to one- hundredth enables the water to rise 100 times as high. The results in the table above will be true only when the walls of the tube are very clean, the water pure and the temperature 32° F. 192. Cause of the Variation in Height to Which Water Is Raised in Capillary Tubes.—The reason for the differences 162 in height to which water may be raised in capillary tubes by surface tension is found in the relation existing between the volume of the tube and its internal circumference at the level of the water surface. Quinke has shown that the foree of cohesion is exerted over a distance of rodeo inch; so that when a glass tube is thrust into water the molecules in the surface of the wall just above the water draw upward upon the rows of molecules in the surface lying nearest, raising them above the natural water level. But as the edge of the surface film is raised the whole water column is carried upward also until the weight lifted above the hydrostatie level is equal to the cohesive attraction be- tween the glass and the water. As each molecule of glass ‘has a fixed power to pull, the tube of large diameter will be able to lift as much more water than the small one, as the number of moleeules im its circumference is greater. But the cireumferences of tubes Increase in the same ratio as their diameters, and henee a tube whose diameter is .1 inch will lift above the water level 10 times as much water as the one .OL inch in diameter. But, as the weight of water lifted inereases as the squares of the diameters of the tubes, the first tube will only lift its column one-tenth as high as the second tube, for then its load becomes 10 times as great, and this is the limit of its power, as expressed in the table below: Relative area’) aight to Relative Diameter of tube, 5 plese which water amount of section of ep 5 bert tul is lifted, water lifted, ube, DOM AMIGO Rica's see te eee once ats 1,000,000 “ .05456 inches 54,560.00 TP BINOIIN ae, \uclck hinted mee carob 10,000 5456 inches 5, 466,00 TOU SAMO MG cas ccs catia tamer site Wacraraans 100 “ 56.456 inches 546.00 SO Ted Obiks sr cancatrcaeaiinne tee sein ateke 1 54.560 inches 54.56 The actual amount of water lifted by the surface film stretched across the tube and carried upward by the pull of the glass molecules just above its edge is as fol- lows: 163 ayes Oh en Chistile@rs scien a cards «serene .04285 cubie inch, Enitiewe l= sime@hiettloe). a. cccs «cere cc e's .004285 cubic inch. Tete. Ole iachintbe citar wereete 6 ore . .0004285 cubic inch. Imepie eOOlmmchiwtube. acct ere cee here 00004285 eubic inch. 193. Capillary Rise of Water in Soils.— The spaces left be- tween the soil grains form more or less triangular capillary tubes whose cross-section, formed by four spherical grains, placed as closely together as possible, is represented at the left in Fig. 54; and these tubes extend in all directions through a soil. The effective diameters of these capillary tubes are somewhat nearly proportional to the diameters of the soil grains so that for soils with spherical grains having the closest packing, doubling the diameters of the grains would also double the effective diameters of the capillary tubes through which the water must be moved. Pic. 54.—Showing the shape of cross-sections of the pore space between soil graiis. The area of cross section of the two capillary pores shown in Fig. 54 is equal to the area of the rhombus con- necting the centers of the four grains minus the area of a eircle having the diameter of the soil grains, so that divid- ing this area by two gives the area of the section of the pore. Where the pore has the smallest section its area is given by the equation Area = (v3 a 5) ; 6 6 Per cent, of water : md sp. gr. 6 where cd == diameter of soil grain in c. m. { thickness of water film. sp. er. = the specific gravity of the soil. Taking a very fine soil having grains with a diameter of 00508 m. m. and a coarse one with a diameter of .1 m. m., a film of moisture on each, having the thickness of the range of sensible cohesive attraction, as given by Quinecke, would make the per cent. for the finest soil 2.31 but for the coarse soil only 1153. No crop ean survive in soils as dry as these; and air-dry soils whose grains range between those given will generally contain more than these amounts of moisture. It follows from these considera- tions, therefore, that what has been regarded as the hygro- seopie moisture is more than that held within the range L177 of sensible cohesive attraction. It appears clear also that no hard and fast line can be drawn between capillary and hygroscopic moisture, nor indeed between either of these and the gravitational water; each must shade by insenst- bla degrees into the other. 206. The Amount of Moisture a Soil May Absorb from the Air.—The amount of so-called hygroscopic moisture a given soil may absorb from the air depends primarily upon the relative temperature of the soil and of the air and its de: gree of saturation. If the temperature of a soil could be maintained continually below that of a saturated atmos: phere above, it would in time become so fully charged with water ag to result not only in capillary saturation but im percolation as well; and it frequently oceurs on clear nights in summer, when dews are heavy, that a thick, loose, dry dust blanket will cool down so much that moisture condenses upon it in sufficient quantity to make it appear damp. Indeed dew, wherever it forms, is a demonstra- tion of the truth of the statement made; when it evapo- rates with the rising of the sun the loss of moisture from the blades of grass may carry the amount all the way from the drops, too heavy to be retained upon the blades, through the thick adhering films, to those which become invisible and are called hygroscopie. 207. Observed Absorption of Moisture from the Air.—'l‘he rate and amount of moisture which may be absorbed from the air is influenced by many factors. Tlilgard has studied the rate and amount of absorption of moisture by soils when spread out in layers about 1m. m. thick in a fully saturated and a half saturated atmosphere, maintained at a uniform temperature. He finds that fully 7 hours are required for an equilibrium to be reached in so thin a layer. In the table which follows are given some of his observations. Table showing the absorptive power of soils spread out in thin layers. SATURATED ATMOSPHERE HALF SATURATED ; : é - ATMOSPHERE, KIND OF SoIL. : : Per cent Per t Temp. | Time, : *1|"Temp: | Lime, ieee Ha oullhns of water Far.° irae of water : * | absorbed. : “+ labsorbed ae a8 a 57 43 6 547 ak: 1 LEAH ae eae Ssacekcinae| (Nerine Barc ‘ = > i 162 1s 11.408 R Wise) Na sl] ea careahe/ eter Urniak orate eter atte NP cee are \ 92 i 12.013 70 7 6.424 wb mes 77 u 12.2383 77 T.5 5-308 88 18,141 88 7 6.356 | L 100 6 18,481 100 6 6.209 f 55 | 19 7.144 || 61 18 4.008 . ate ~ 3 Black adobe soil, Univer- H x | Wee - AN aise sity grounds, Alameda) 4 30 : 7 ore Se 15 3926 HOWLOT aoe aka secs Pee ee 8.681 83 “s 8.929 y |} &2.6 1.5 8.948 89.5 7.5 8.910 { 100 7 9.569 100 7 3.885 (eer 1s 2.183 59 18 0.987 Calcareous silt soil, Fresno} | 79 6 2,983 19 6 0.959 COUNERNsaricaee ats enone. i oe 7 3.396 S4 vi 0.858 95 6 4.211 95 6 0.821 It will be seen that in the saturated atmosphere the largest amount of moisture was absorbed at the highest temperature, while the reverse was true in the half sat- urated atmosphere. Under the high temperature the rate of molecular movement is so rapid that the rate at which the water from the air falls upon and enters the soil is so much inereased that more water must have accumulated in the soil before the number of molecules which ean leave its surface in a unit of time equals that which falls upon it. In the dryer atmosphere, on the other hand, where there are less molecules to fall upon the soil and increase its amount, the higher temperature favors the rapid escape as much as when the saturation was high and, since less water is condensing, a lower per cent. is finally present when an equilibrium of interchange has been reached. 208. Internal Evaporation of Soil Moisture.—It is likely that under certain conditions the thermal movements of soil moisture may be considerable and perhaps of sufficient importance to materially influence vegetation, directly or indirectly. When the per cent. of unoccupied pore space in a soil has been materially increased by the loss of wa- ter and when the moisture films have become so thin that ‘apillarity is much enfeebled it is possible that internal evaporation of soil moisture may result in a considerable change of its position. If, for example, when the soil has become quite dry, to considerable depths, the surface six inches should become cooler than that below, the tendency to continual diffusion of water vapor under the impulse of heat would produce more internal evaporation of moist- ure where the soil is warmest and most moist, and a larger condensation of moisture where the soil is dryer and cool- er. Even where there is little difference in temperature be- tween adjacent layers of soil there must be, if they are not equally saturated, a tendency for diffusion to take place more rapidly from the wettest layer of soil toward that which is least moist. It is possible that during dry times and in dry climates during the dry season some moisture, too far below the root zone to be made available through eapillarity, may be carried upward by these thermal or evaporation movements so as to become helpful to crops in a measure. We are yet lacking in experimental data to form any just conception as to the magnitude of such a movement. 209. Temperature Influence of Hygroscopic Moisture.— It is Hilgard’s view that, in dry climates and during droughty periods in humid climates, the moisture still retained by soils when capillarity has become very feeble may exert an important influence in preventing the soil from becom- ing overheated during dry soil conditions, by the cooling effect of internal evaporation. It must be observed, how- ever, that in order that this influence may become effective the moisture evaporated must have left the soil and not 180 have been replaced by an equal amount through condensa- tion from some other place. It appears to the writer possible that the ability of such soils to withstand drought may perhaps be partly due to a more rapid evaporation from the soil grains and con- densation of moisture on the root hairs, the thermal move- ment, in this way, tending to supplement the enfeebled eapillarity. 181 CHAPTER. V EI. CONSERVATION OF SOIL MOISTURE. There are very few fields upon which crops of any kind, in any climate, can be brought to maturity with the max- imum yields the soils are capable of producing without adopting means of saving the soil moisture. There are fields, it is true, where, at times, the moisture in the soil is too great, and drainage becomes necessary ; but even un- der these conditions it will usually be found advisable to adopt measures for conserving the water not so removed. 210. Modes of Controlling Soil Moisture.—In aiming to control soil moisture three distinct lines of operation are followed, based upon as many different aims. These are: (1) To conserve the moisture already in the soil (a) by different modes, times and frequencies of tillage, (b) by the application of mulches, and (ec) by establishing wind breaks. (2) To reduce the quantity of water in a soil (a) by frequent stirring, (b) by ridging or firming the surface, (c) by decreasing the water capacity, and (d) by surface or under drainage. (3) To increase the amount of water in a soi! (a) by increasing its water capacity, (b) by strengthening the capillary movement upward and (¢) by irrigation. 211. Late Fall Plowing to Conserve Moisture.— There is no method of developing so effective a soil mulch as that furnished by a tool which, like the plow, completely cuts off a layer of surface soil and returns it loosely, bottom up, to place again. 11 182 When ground is plowed late in the fall, just before freezing, it then acts during the winter and early spring as a mulch, diminishing the loss of water by surface evapo- ‘ation, and at the same time the roughened surface tends to hold the snows and to permit winter and early spring rains to penetrate more deeply into the soil, leaving the ground more moist at seeding time than would be the ease if it were left unplowed. Determinations of the moisture in the spring, as late as May 14, have proved that late fall plowed ground may contain fully 6 pounds per square foot more water in the upper four feet than similar adja- cent ground not plowed. This difference represents a rainfall of 1.15 inches and is a very important saving in climates of deficient water supply for crops. 212. Late Tillage for Orchards and Small Fruits.—Late fall plowing and deep cultivation in orchards of fruit trees and in vineyards of small fruits, after the wood is fully matured and growth arrested by the cold weather, will do very much toward giving the soil better moisture relations the next spring, tending to secure such results as are cited in (211). In cases where injury from deep freezing is liable to occur the late plowing will lessen this danger because the loose soil blanket will help to retain the heat in the ground as well as the soil moisture. In the late plowing and deep tillage, advised in this and the last section, there is little danger of increasing the loss of plant food by leaching because the season is too late and the temperature of the soil too low to stimulate the formation of nitrates. 213. Early Fall Plowing to Save Soil Moisture.—Jn those eases where winter grain is to be sowed, the early plowing of the ground, or plowing as soon as the field has been freed from the preceding crop, is in the direction of econ- omy of soil moisture. So too in sub-humid climates, even where winter grain is not to be sowed, it will often be desirable to plow as early as possible in order to retain 183 soil moisture and to facilitate the entrance of the fall rains more deeply into the ground. ‘The early plowing or disk- ing in these cases may also be helpful in hastening nitrifi- cation in the soil. It is the strong tendency of early fall plowing, in cli- mates where there is plenty of soil moisture to develop nitrates and where there is much rain in the late fall and early spring, which has led to the sowing of “cover crops” having for their primary object the locking up of the solu- ble plant foods to prevent them from being lost by soil leaching; and the tendency of early fall plowing to dimin- ish surface evaporation and thus, in wet climates, to in- crease percolation and the loss of plant food may some- times make this practice undesirable in such cases. 214. Early Spring Plowing to Save Soil Moisture.—In all climates where there is a tendency of the soil to become too dry the earliest stirring in the spring, which is prac: tieable without injuring the soil texture, is in the direc- tion of economy in most cases because, at this season of the year, the effectiveness of tillage in conserving soil moisture is greater than at almost any other time. ‘This statement follows from (198), where it is shown that a wet soil car- ries water to the surface much more rapidly and from a greater depth than a dry soil can. In the spring the soil at the surface is usually not only wet but also well com- pacted, two of the most important conditions for the rapid movement of water to the surface, and it is because of these that early and deep spring tillage is so lmportant as a means of saving soil moisture. In one instance, where two immediately cee pieces of ground, in every way alike, were plowed in the spring, 7 days apart, it was found that the earliest plowed ground contained, at the time the second piece was plowed, a lit- tle more moisture in the upper four feet than it had 7 days before, while the ground which had not been plowed had lost, in the same interval of time, an amount of moisture from the surface four feet equal to 1.75 inches, a full paMojd a19M sboaR padojod 4yYsIT = ‘\saAIP 918 PUB ISBT any, ‘aanjsrour jos uo SZarMord supads oye ee | pue [Ive Jo eouenyu, ay) BuayMoyg—ye ‘oT 185 eighth of the rainfall of the growing season of that lo- ceality. Nor wasthe saving of moisture the only advantage gained by the early plowing, for the soil plowed last had dried so extensively as to become very hard and lumpy, thus great- ly increasing the labor necessary to fit it for planting. In another experiment to study the effectiveness of early as compared with late spring plowing in conserving soil moisture Fig. 57 shows how evident the effects were to the eye. 215. Disking or Harrowing Where There is Not Time to Plow.—It often happens in the spring that hot dry winds come on when there is not opportunity to get the ground plowed in time to save the needed moisture and prevent the development of clods. In such cases the use of tho disk harrow, or even the ordinary spike tooth harrow, will do very much to save the moisture and preserve the tilth of the soil, if only the fields are gone over with these. The disk harrow is one of the best of tools for early use in the spring to work the soil and develop mulches. 216. Corn and Potato Ground, Orchards and Gardens Plowed Early in the Spring.—Ground to be planted to corn or potatoes, as well as the orchard and garden, should gen- erally be plowed quite early in the spring and a consid- erable time before it is intended to plant them. By doing this, not only will moisture be saved but the development of nitrates in the soil will be hastened and thus larger crops secured on this account. It is only in the event of long, frequent and heavy rains, following such early tillage, that loss can result from such a practice. 217. Effectiveness of Soil Mulches.—The effectiveness of soil mulches as means for diminishing evaporation varies (1) with the size of the soil grains, (2) with the coarse- ness of the crumb structure, (3) with the thickness of the mulch and (4) with the frequency with which the soil is 186 stirred. Soils which maintain a strong capillary rise of water through them will, when converted into mulches, still permit the water to waste through their mulches faster than it will be lost through the mulches of soils whick permit only slow capillary movements. That is, the sandy soils for more effective mulches than do the clayey ones and this greater effectiveness of the sandy soils, as mulches, goes a long way toward making the smaller amount of water they are able to retain effective in crop production. In Fig. 58 is shown an apparatus for measuring the relative effectiveness of mulches and in the table which follows are given the results of a series of trials with three types of soil. The cylinders in this series, however, stood out in the open air of the field rather than in the case shown in the cut. Table showing the effectiveness of soil mulches of different kinds and different thicknesses. Mulch Mulch Mulch Mulch No zanlen, 1 in. deep, | 2 in. deep, | 3 in. deep, | 4 in. deep, er 109 |Wwater lost}/water lost/water lost}water lost Tae = per 100 per 100 per 100 per 100 vi: days. days. days. days. Black marsh soil: Tons per acre ....... 588.0 355.0 270.0 256.4 252.5 Inches of water 5.193 3.12 2.384 2.265 2.230 Per cent. saved by miulehesin.ceseeeeee 39.54 54,08 56.39 57.06 Sandy loam: . Mons perlacre) ... 4 741.5 3ia.7 339.3 287.9 315.4 Inches of water ..... 6.548 3.300 2.996 2.539 2.785: Per cent. saved by muUlchesiitescsseot| soe oemne 49.69 54 24 61.22 57.47 Virgin clay loam: Tons per acre .......| 2,414. | 1,260. 979.7 889.2 883.9 Inches of water ..... 21.31 Tis 8.652 7.852 7.805 Per cent. saved by mulehesias eee ee. Geeeessoares 47.76 59.38 63.18 63.34 From this table it will be seen that the soil mulches have exerted a very great influence in saving soil moisture. 187 It should be understood, however, that if the water reservoirs had been much farther below the surface of the soil, and below the mulch, the mulches would have been more effective as well as less water would have been lost from the unmulched cylinders. 218. Frequency of Cultivation May Make Mulches More Effective—When a fresh mulch is formed upon the surface of a well moistened soil the first effect of the stirring is se! eeaereie|[ EL Fie. 58.—Apparatus fer measuring the relative effectiveness of mulches, to increase the rate of evaporation from the field, on ac- count of the much larger surface of wet soil which is ex- posed to the air. This greater loss of water, however, is largely from the stirred soil. If dry winds and sunny weather follow the formation of the soil mulch it soon becomes so dry that but a relatively small amount of wa- ter can pass up through it. On the other hand if a series of cloudy days follow, when the rate of evaporation must be small even from firm wet soil, and if at the same time the soil below the mulch is quite moist, so much water may pass up into the mulch as to nearly saturate the lower portion of it and to cause the kernels to be drawn 188 together and again compacted and reunited with the un- stirred soil below. If this change does take place the muleh is rendered less effeetive and a second stirring is needed. Wie, 59.—Showing large eylinders for studying soil problems. The relative effectiveness of mulches stirred twice per week, once per week, and onee in two weeks, for a virgin clay loam, in eylinders 52 inches deep and 18 inches in diameter, standing in our plant house, as shown in Fig. 59, is given in the table which follows. 189 ‘able showing the relative effectiveness of soil mulches of dif- bere nt de SG and different sr equencies of cultivation. a ————— — Not culti-| Once in | Once per | Twice per vated, 2 weeks. week, week, Per acre, | Per acre. | Per acre. | Per acre, Cultivated one inch deep :* The loss in tons per 100 days was| 1724.1 551.2 545.0 527.8 The loss in inches per 100 days VAG eikivgadtatirssiet coin sciceteane 6,394 4,867 4,812 4, 662 The percentage of water saved AB aetna Was candaeek weasel Gal kx valet p © 23,88 24.73 27.10 Cultivated two inches deep: The loss in tons per 100 days was| 1724.1 609.2 552.1 515.4 The loss in inches per 1U0U days was, 6.394 5,380 4 875 4,552 The percentage of water saved was. Pa aahC aia siy\ohe Koc x 'a'sle mia rei |b cate wlorice! oe fa 15.88 23.76 28.81 r Cultivated three inches deep: The loss in tons per 100 days was) 724.1 612.0 531 5 495.0 The loss in inches per 100 days was, 6,394 5.280 4.694 4,371 The percentage of water saved was. BA ACR re rt Arne Fee RAEI 15,49 26.60 31,64 It will be seen that with each of the three depths of cul- tivation the percentage of moisture saved, over that which was lost from the ground not cultivated, increased with the frequency of cultivation. 219. Too Frequent Cultivation Undesirable. When a soil mulch is well loosened and thoroughly separated from the firm ground beneath, and especially after the mulch has become quite dry, little can be gained by stirring the soil. Indeed it must ever be kept in mind that it costs to cul- tivate a field and when this is done without need the work is a dead loss. Further than this, late in the season, when the surface of the ground has become relatively dry, posi- tive harm may be done by unnecessary cultivation because at this season many plants have put up, very close to the surface, great numbers of fine roots in order to avail themselves of the moisture from light showers and from the dew which may be condensed in the surface layer 190 of soil on the coolest nights. To destroy these roots will, in most cases, cause a greater loss by root pruning than can be gained by saving moisture. It is possible also, by too frequent tillage, to make the texture of the mulch so fine that its effectiveness is decreased. 220. Cultivations Should Be Most Frequent in the Spring. In the early part of the season when the aeration of the soil, the warming of it and the killing of weeds are other important objects to be attained it is more important to cultivate frequently. This is the season of the year when the effectiveness of mulches decreases most rapidly, it is the season when there is least danger of destroying the roots of the crop, and it is the time when cultivation is needed to help develop plant food. 221. Cultivation After Heavy Rains.—Whenever a rain has occurred which has thoroughly united the soil crumbs to one another, and with the soil below, it is time to eul- tivate again if this ean possibly be done without too pe root pruning, and the cultivation should be done just a quickly as the soil will permit. In the early part of the season there is little danger of root pruning if the culti- vator teeth do not go too close to the plants and not more than 3 inches deep. ; A rain which does not wet down more than 3 inches cannot be saved by cultivation; all that can be done in this case is to permit the surface roots to get as much of it as possible and to stir, if it appears expedient, when the wetting is likely to strengthen the upward movement too much. It must be remembered in this connection, however, that if, late in the season, the roots of the crop have spread horizontally through the whole soil, anything which strengthens the rise of the deeper water, causing it to come nearer the surface, at the same time brings it to the roots where it is needed, and hence it will seldom happen that a crop like corn or potatoes can be helped by 191 cultivation after the corn is in tassel or the vines begin to well cover the ground. 222. Depth of Cultivation to Save Moisture.—In regard to this point it must be kept in mind that the soils out of which mulchesaremade are the richest on the farm and that when they are converted into perfect mulches they are prac- tically useless so far as direct plant feeding is concerned. The general rule must then be to make the mulch just as thin as it can be and not permit too heavy a waste of the deeper soil water. On the lighter and coarser grained soils the mulches may be shallower than on those of the clayey type. In Wisconsin we have found that with the ordinary narrow pointed tooth cultivators a depth of about three inches saves more moisture and permits larger yields of corn in about 15 cases out of 20 than less depth of culti- vation. Where the tool is of such a character that it shaves off the whole surface of the ground and leaves the stirred soil spread in a blanket of uniform thickness the stirring may be shallower than if the surface of the ground is left in either narrow or wide ridges. 223. Depth and Frequency of Cultivation Should Vary With the Season and Crop.—F rom what has been said in the preceding paragraphs it follows that the soil may to ad- vantage be eultivated more deeply and more frequently during the early part of the season when the soil tem- peratures tend to be low, when the moisture may be over- abundant, and when weed seeds are germinating. Later in the season, however, when there is not as great need to encourage the development of nitrates by tillage, when the roots have come closer to the surface, and the main- tenance of a soil mulch is the chief or only object, the cultivation may evidently be less deep and not so fre- quent. The general practice then should be to gradually make the cultivation both less deep and less frequent. It should also be kept in mind that cultivation may gener- 192 ally be a little deeper in the middle of the space between rows, than close to the hills, because of less danger of root pruning. 224. Best Time to Cultivate Corn and Potatoes.—The best time to till land for corn, potatoes and similar crops, where intertillage is practiced, is before the ground is planted and just as the crop is coming up. When the ground is plowed two or three weeks before the crop is to be planted there is opportunity to develop the nitrates, to kill one or two crops of weeds, and to store in the upper five feet of soil the largest reserve of soil moisture from the spring rains. Besides these advantages there is no period in the growth of the crop when the ground can be stirred so rapidly and so cheaply. Before planting the disk or spring-tooth harrow may be used and afterward the dif- ferent weights of spike-tooth harrows, which enable a larger area of ground to be covered in a day by a man and team. The harrowing of corn and potatoes should be continued until the plants are well out of the ground and if care is taken to do the work during the hot por- tion of the day, when from slight wilting the plants do not break off readily, there need be but little serious in- jury to them. The different types of mulch produeing tools are dis- cussed in the chapter on Implements of Tillage. 225. Harrowing and Rolling Small Grain After It Is Up.— It sometimes happens in huniid climates, when drying weather follows a wet period, that a crust forms on the surface of fields sowed to the small grains, which may be injurious to the plants by preventing sufficient aera- tion and increasing the loss of moisture. In such eases the difficulties may be partly corrected by using either the roller or the light harrow with teeth sloping backward. If the grain is large, and especially if the surface of the field has been left narrowly ridged and somewhat lumpy, the use of the roller when the surface soil is dry will break up the crust by crumbling down the ridges and lumps and at the same time develop a true and effective mulch. The light harrow, when driven across the ridges, may be effective in breaking up the crust and in develop- ing a mulch. In sub-humid climates, such as that of western Kansas, fields seeded permanently to alfalfa have been, in the very early spring, gone over with the disk harrow and then crossed with the spike-tooth harrow, thus developing a very effective mulch which materially increases the yield. 226. Mulches Not Made From Soil.— While it is true that most conservation of moisture must be through earth mulches it should be understood that all vegetation growing upon the ground, whether it completely covers the surface or not, exerts a protective influence and diminishes the loss of moisture directly from the soil itself. This pro- tection comes partly from shading, partly from diminish- ing the wind velocity and partly from the saturation of the air with moisture by the transpiration from the grow- ing plants. Even in pastures where the grass is short, but close, the mulehing effect is strong and hence it is not in the direc- tion of economy to allow the feeding to be too close, not only because the growth of the grass is slower from too severe destruction of the foliage, but because there is a ereater loss of soil moisture besides that passing through the grass. The surface dressing of meadows with farmyard manure, thoroughly harrowed to spread it evenly over the ground, is extremely beneficial through its mulching effect as well as in the plant food it brings to the soil. When such dressings are applied in the winter and early spring and spread over the surface while the soil is yet wet beneath, the saving in soil moisture is greatest and in the case of meadows where the clover has disappeared, for any rea- son, such a dressing may make it possible to get a new seeding, by sowing the clover broadcast before the frost 194 is out in the spring, so that the thawing and freezing will tend to cover the seed and the thin mulch protect the ground from too rapid drying until the young plants are well rooted. The use of straw and other coarse litter and coarse sand for mulching will generally only be practicable in gardens and orchards and for the protection of shade trees and the lke. 227. Ridged and Flat Cultivation.—It used to be a com- mon practice to “lay by” the corn and potato crop with a strong hilling of the rows. This practice, however, ex- cept for potatoes, is now generally abandoned unless in localities where surface drainage is needed. The general abandonment of the practice rests in part upon the be- hef that the evaporation from the soil is appreciably in- creased by this process on account of the greater amount of surface exposed to the air. In making a practical test during the season of 1899 the results recorded in the following table were secured. These plots, each seven rows wide, alternated across a field of nearly uniform soil and samples were taken under and between every row. It will be seen that the soil re- ceiving the flat cultivation contained at the end of the growing season a little less water than the ridged plots, which is contrary to the accepted belief. Since the ridges are all shaded by the potato vines and since the wind ecur- rents may be supposed to be less strong between _the fur- rows, perhaps this is as should be expected. It is true, however, that the plots cultivated flat produced a little larger yield per acre and on this account the soil should have lost more moisture. It may be that the flat cul- tivation did really make a larger saving of water and that this saving was the cause of the larger yield. 195 Table showing the water content of soil, Sept. 19, under and _ between rows of potatoes hilled and left flat when laid by. HILLED, FLAT. Nos. of DEPTH OF SAMPLE. eee plots Between . Between In row can In row. ane Per cent. | Per cent Per cent. |Per cent. { Vesa oaks 12.83 14.11 11.85 14.23 Mirstfootysqecersoccee 7) z Seataratanaecete 12.01 13.61 12.18 13.54 Mean 12.42 13.86 12.02 13.89 (lleescuas. 16.71 18.56 15.38 17.69 Second foot .......... ? 2 Sea eletetoasts 15.84 17.85 16.03 17.84 Mean 16.28 18.21 ilByArAl ie tid Wee coh acer "7 18.00% «| 18-61 16.41 18.03 Third foots-s..22es 2 Diiteweicw eee 17.09 17.55 16.13 17.97 SE ee MN IH aes reer crarll rere tetbeleraretccrstare"|lsiszeveh ete tater eratssel llev=v=leqsroterer'els Moean....|| | 17.55 18.08 16.27 18.00 Gi deste teatas 15.78 16.95 9.79 | 11.75 Hourthefoote ses. eacses Demeter Pier ts 14.41 13.98 13.08 14.01 CW BatkeosoneaallllGoca ccasoo0el|p005 onoc.nadal|||aasnoooaoopel|obadorooc! Mean....|| 15.08 15.46 11.44 12.88 Mean of foursfeets..ccc||.cocdss see 15.33 16.40 13.86 15.64 228. Subsoiling to Save Soil Moisture.— ‘The deep plowing or stirring of the soil, to which this name has been applied, has the effect of making a larger per cent. of the rainfall available in producing crops, but it will never have the wide applicability that is possible for surface tillage. In sub-humid climates where the subsoils are less liable to be puddled and where there is the greatest need of economy this method of conserving soil moisture will find its widest usefulness. A piece of ground when subsoiled, as represented in Fig. 60 and given, with an adjacent area, a like amount of water, and protected from surface evaporation, was found to have retained not only the water given it but te have gained an additional supply through capillarity from below; while the ground not subsoiled lost a large per cent. of that given to it through percolation and capillary creeping. From the subsoiled area 8 inches of the surface were removed, the subsoil spaded to a depth of 13 inches more, and the soil returned to its place. After taking peau END» % ise ra ic. 60.—Method of demonstrating the influence of subsoiling on soil moisture, samples from the five places indicated by the dots, 1.36 inches of water were gradually sprinkled over the two areas on June 11th and they were allowed to remain cov- ered until the 15th, when samples were again taken. The changes in the water content of the soil in the two areas are shown in the table which follows: Table showing the ability of subsoiled ground to hold water against gravity. ae Not : ; Subsoiled. subsoiled. | Difference. Lbs. Lbs. Lbs. Dhevtinst foot eamed).acse enone ene 124.6 102.1 +22.5 The second foot gained |. .....eeee eee. W207 10.34 -+-62.23 Phe thirdifoot/ghined s1e-s. eee eee 38.22 12.05 -+-26.17 The fourth foot gained. ............-.... 33.26 3.82 +29 .43 The fifth foot lostis.ts.. cecckee cee 2.29 19.5 —17.21 hotalowatencained ane acacseceeetenernines 268.65 128.31 Potalswateraadedinct jsscknccce cee nee 254.41 254.41 DidferancGi.cPadhencsteens ee eens 14.24 =964) 1° 197 The subsoiled ground had therefore not only retained all the water added but it had gained by capillarity 14.24 Ibs. more. It is noteworthy too that the fifth foot in both places had lost water upward by capillarity, 2.29 lbs. in the former and 19.5 lbs. in the latter case. The effect of subsoiling on the capillary rise of water from below was demonstrated by using the same piece of apparatus in the same way except that the two areas were covered to prevent evaporation, without adding any water, the experiment extending from June 26 until July 2, giv- ing the results shown in the next table. Table showing the effect of subsoiling on the capillary rise of water from the deeper soil when no evaporation can take place from the surface. ON SUBSOILED GROUND. Ist foot. | 2nd foot.| 3rd foot.| 4th foot. | 5th foot, June 26 § Moisture (| Per ct. | Per ct. | Per ct. | Per ct. | Per ct. Piece ate. ets eabo. 23.29 21.89 17.85 14.14 19.55 July 2 j§ Moisture ; : oO ea Cad | at close. 22.66 22.50 17.49 14.45 20.27 Mbintie) she ares BBGay leroe aie ae eaen Lea qien | petsaeae On GROUND NOT SUBSOILED. Tita) ASS Eben seneniacopose cdaAnasel| | Ore 20.67 17.74 15.06 19.34 eM 2 —CLOSO) =. 2 soy = ca naees's 23.97 22.09 18.92 14 62 18.38 CHANge 2... 262. --- see ee ee | 19 45 +4.32 +1.18 Sin =" 496 It will be seen that in the subsoiled area there had been but little change in the water condition while the ground not subsoiled had gained a very material amount of water in the surface three feet at the expense of that deeper in the ground, the gain in the upper three feet amounting, on the 36 square feet, to 129.69 Ibs., 53.52 Ibs. having come from the fourth and fifth feet and the balance prob- ably partly from the sides and partly from the sixth foot. When the ground was subsoiled in the same manner as 12 198 before and allowed to stand exposed under natural condi- tions, and the surface kept free from weeds by shaving them off close to the surface with a sharp hoe, it was found, after an interval of 75 days from June until September, that the water content of the soil stood as in the next table. Subsoiled |Not subsoiled . ground. ground. Difference. Per cent. Per cent. Per cent. HUrst LOOtisencoesaurutecllareol emis aeitietelerectere 17.07 18.91 —1.84 Seconaootiventec cmos cesarean coetes 23.29 19.42 +8 .87 AU ciide liixors} nono bapa podoadesoosGocaD Gooaoc 22.76 17.78 +4.98 MOurth footie sesecc cts misc iets tlesisisite 16.35 14.19 +2.16 Mifth foOtssses cen cece eee eee 18.14 19.20 —1.06 In this case the surface foot of subsoiled ground is dryer than that not so treated, but the second, third and fourth have gained in moisture, over and above that lost from the other two feet, enough to represent a rainfall of 1.64 inches. 229. Moisture Effects of Subsoiling.—The results which have been given in the last section illustrate several very distinet effects produced by subsoiling: (1) Subsoiling increases the percentage capacity of the soils stirred for moisture. (2) Subsoiling decreases the capillary conducting power of the soil stirred. (3) Subsoiling increases percolation through the soil stirred or its gravitational conducting capacity. 230. How Subsoiling Increases the Water Capacity of the Soil Stirred— When a soil is broken into lumps lying loosely together, and these become filled with water, each one behaves in a measure much as if it were standing by it- self and much as a lump of sugar would, plunged into water and then withdrawn, coming forth with its pores practically filled with water. In short columns of soil, like the lumps, the surface films of water which span their capillary pores are strong enough to maintain their whole 199 interior nearly full of water, drainage being largely con- fined to those passageways and cavities which have larger than capillary dimensions. If a dozen strands of candle-wicking, two feet long, are twisted loosely together, saturated in a basin of water, and then held horizontally from the two ends to drain, more water will be retained than if it is allowed to sag into a loop and drainage from it will be still more complete when hanging from one end. So it is with long continuous col- umns of soil; from them the drainage is more complete than from shorter ones. 231. How Subsoiling Decreases the Capillary Conducting Power.—When large open spaces have been formed in a soil, by any means, as is the case in subsoiling, every such cavity cuts off the capillary connection with the unstirred soil below and above and in this way reduces the number of capillary passageways by which water may rise to the surface. This being true, when rains fall upon subsoiled ground, water travels downward quite slowly until after it has become ecapillarily saturated and, if the rain is not enough to over-saturate the layer, the whole will be retained. On the other hand, when the subsoiled layer has once become dry, the poor connection with the firmer ground below and its open texture makes it impossible for the moisture to rise through it to the surface as rapidly as it could through a more compact layer. It is clear, from these relations, that when the root system of a crop once develops through the subsoiled layer it may then act as a mulch of great thickness and increase the yield; but should a crop fail to get its roots below the subsoiled layer before the moisture becomes too scanty then a diminished yield might be the result even with an abundance of water below. 232. How Subsoiling Favors Percolation.—When rain enough has fallen upon an earth mulch or upon subsoiled ground to completely saturate the soil the balance of the 200 water is then free to move rapidly downward through the large non-capillary pores, urged by the strong force of = : gravity. Not only this, but, since the pores are many of them too large to be filled by the percolating streams, there is left an easy egress for the soil-air, which must escape upward before the water can enter, and this does not re- tard percolation as it does in a compact soil. 233. A Larger Percentage of the Moisture of Subsoiled Ground Available to Crops——When a soil has been made more open by subsoiling, and its capacity for holding water thereby increased, this extra amount of water retained be- comes wholly available to crops. It was shown in (161) and (162) that there is a certain per cent. of water in a soil which the roots of plants are unable to remove with sufficient rapidity to meet their needs and as this amount depends upon the size of the soil grains, which subsoiling does not alter, the increased percentage held becomes a clear gain to the crop. 234. Dangers From Subsoiling.—QOne of the most serious difficulties associated with subsoiling, aside from the ex- pense, is the danger of puddling, and this is particularly great in humid climates where the subsoil, especially in the spring, is liable to be too wet. The danger is intensi- fied on account of the fact that the surface soil may be in good condition for plowing when that below is much too wet. If this work is attempted when the ground is not in condition very great harm may be done and so it is gen- erally much safer to subsoil late in the fall in humid eli- mates, when the deeper ground is generally dryest. 235. Early Seeding.—When the crop is started to grow- ing upon the ground as early as the temperature of the soil and of the air will permit the farmer is conserving soil moisture, by taking advantage of that which otherwise would be lost by surface evaporation, and enabling his crop to use this in growth. Such timely planting may not only 201 save moisture from going to waste, both by evaporation and by percolation, but it may save plant food from loss in the drainage waters. Yet, while due diligence should be exercised in timely planting and sowing, there j is danger of too great, haste and it will generally be better to mi ake the mistake of getting the crop in a little late rather than too early. The soil should by all means be warm enough and dry enough to make germination prompt and vigorous, for otherwise weak and sickly plants will result, if the seed does not rot in the ground. 236. Danger From Green Manuring.—In the practice of erowing cover- Crops, and in green manuring, attention must alw ays be given to the effect these have upon the soil moisture, as related to the crop which is to follow. When either rye or clover is used in green manuring, and the plants are allowed to make a heavy growth before plowing under, the soil will be found very much dryer than if the field had been plowed and tilled early but left naked, or even if not plowed at all. The next table demonst ‘ates the truth of this statement, showing, as it does, the strong drying effect of clover as early as May 13. Table showing the drying effect upon the soilof a green ma- nure crop. 1 to 6 inches. |12 to 18 inches.|18 to 24 inches. Per cent. Per cent. Per cent. Ground not planted............ -. 23.33 19.13 16.85 AFronndln ClOver ss. sa csalenseesces 9.59 14.75 13.75 IOTEEGTONCE poet ac ect cciise ones ns 13.74 4.38 3.10 In such a ease as this, with the soil as dry when plowed as that under the clover, not only would there be danger of the seed not germinating properly but the large growth of herbage, when plowed under, would so much cut off the capillary connection with the deeper soil moisture that it could not readily become available until after the roots had penetrated below this level. Nor is this all; any such crop would have locked up in insoluble form, for the time being, a large portion of the soluble plant food, and unless abundant and timely rains were to follow the plowing speedily to develop a new sup- ply, the next crop would suffer for lack of nitrates and other plant foods. On soils naturally too wet and in wet seasons the dan- gers referred to will of course not be so great and the green manure crop might even be an advantage from the soil moisture side by making the over-wet soil more open, thus favoring stronger root action and more rapid nitri- fication. 237, Wind-breaks and Hedges.—‘‘In* sub-humid climates, especially like those of our western prairies, where there is a high mean wind velocity, and in the level districts of humid climates, where the soils are light and sandy, with a small water capacity, and which are lacking in adhesive quality, the fields may suffer greatly at times, not only from excessive loss of moisture, but the soil itself may be greatly damaged by drifting caused by the winds. Under such conditions, it is a matter of great importance that the wind velocities close to the surface should be reduced as much as possible.” On the lighter sandy lands, wherever broad fields lie unsheltered by any wind-break, strong dry winds frequent- ly sweep entirely away crops of grain after they are four inches high, and at the same time drift away even as much as three or four inches of the surface soil, the best in the field. In such cases wind-breaks and hedge-rows exert a very strong protective influence and greatly lessen such dis- astrous results. Not only do trees along line fences and roadsides, un- der these conditions, prevent such direct injuries to soil and *Trrigation and Drainage, p. 168. 203 crops but they materially lessen the evaporation of moisture from the soil and thus help to secure a higher yield of crops. *‘*The writer has observed that, when the rate of evaporation at 20, 40, and 60 feet to the leeward of a grove of black oak 15 to 20 feet high was 11.5 ¢. ¢., 11.6 e. c., and 11.9 c¢. c, respectively, from a wet surface of 27 square inches, it was 14.5, 14.2 and 14.7 ¢. ¢., at 280, 300 and 320 feet distant, or 24 per cent. greater at the three outer stations than at the nearer ones. So, too, a scanty hedge-row produced observed differences in the rate of ev aporation as follows, during an interval of one hour: At 20 feet from the hedge-row the evaporation was.............. 10.3¢.c¢. At 150 feet from the hedge-row the evaporation was.............. 12.5¢.¢. At 300 feet from the hedge-row the evaporation was... ........... 13.4 c.c. Here the drying effect of the wind at 300 feet was 30 per, cent. greater than at 20 feet, and 7 per cent. greater than at 150 feet from the hedge. Then, too, when the air came across a clover field 780 feet wide the observed rates of evaporation were: tee OT OO UTLOMCLOVOL A sesessig aitin oerekee anole eases oka semectee 9.3¢. c. PNETEOOLOR tH LOMECLOV Olimrcnisave na craceetes ae eae einen cetee cee oe 12.1¢.c. MER LEG LHLOMI CLOVER Lionas nctincncjvasser ora nae ene an acces eee Lae CFG: Or 40 per cent. greater at 300 feet away than at 20 feet, and 7.4 per cent. greater than at 150 feet.” *Trrigation and Drainage, p. 169. 204: GHAPTER IX. RELATION OF AIR TO SOIL. NEEDS OF SOIL VENTILATION. Air in the soil in which crops are to be grown is as es- sential to the life of the plants as the air in a stable is to the life of the animals housed. Careful observations and lines of experimentation have proved, in many ways, that when oxygen is completely ex- cluded from seeds that are otherwise under good conditions for germination they fail to start. It has been found, too, that even after a seed has begun to grow, if the oxygen supply is cut off, it makes no farther progress. Growth does take place in seeds in a very dilute atmosphere of oxy- gen, but after the amount has been reduced below vz of the average in the air the plants advance very slowly and are sickly. A soil in the best condition for crops must permit of ready entrance of fresh air and an abundant escape of the air once used; in other words, like the stable, it must be well ventilated. This ventilation is needed: (1) To supply free oxygen to be consumed in the soil. (2) To supply free nitrogen for the use of the free- nitrogen-fixing germs. (3) To remove the excess of earbon-dioxide which is set free in the soil. 238. Needs For Free Oxygen in the Soil.—T ree oxygen in the soil is required not only by the seeds, when they are germinating, but throughout the active life of the plant in order to permit the roots to live, for they, too, must breathe. Then in the conversion of the nitrogen of humus, manure, 205 and decaying organic matter in the soil into nitri¢ acid, large amounts of oxygen are needed, for each of the three known forms of microscopic life which do this work are unable to live in its absence. 239. A Water-logged Soil.—One of the chief reasons for the unproductiveness of a water-logged soil is the deficiency of free atmospheric oxygen in it. When the soil pores are filled with water and this water is stationary, that is, not changing, the free oxygen which it may contain in the air dissolved in it is soon used up and then the rate at which oxygen from the air above the soil is able to make its way downward through the soil-water and around and between the soil grains is much too slow to meet the ordinary needs of the roots of any erop. Not only this, but, as pointed out in (103), even the microseopie organisms in the soil find so scanty a supply that they are obliged to decompose the nitrie acid for the oxygen it contains in order to supply their needs. ‘The chief need of draining wet lands, then, is to secure to the soil a more rapid change of air. 240. Floating Gardens.—The instances where the Chinese and Mexicans grow crops upon floating rafts of logs an- chored in a stream or lake and thinly covered with soil may seem to contradict the statements in the last paragraph regarding a water-logged soil because, in these cases, the soil is very wet in its lower portion and the roots of the plants are continually immersed in a saturated soil or in the water itself beneath. \ La a , — ! \—a™ Oi cet sa say AN a rig. 66.—Cultivator with rigid teeth: best where soil is heavy and not stony. 279. The Teeth of the Cultivator Adjustable.— Another important feature sulky cultivators should possess is the possibility of tilting the gangs so as to allow them to work more deeply in the soil toward the center of the row in the later stages of cultivation because then the roots near the rows have deve loped close to the surface, and dee per eulti- vation in the center, where the soil is more exposed to the sun, is needed for etfeetiveness as a muleh. 280. Covering Weeds in the Row.—It sometimes happens with the most careful management that weeds will get such a start in the row that either hand hoeing must be resorted to or else a tool must be used which will throw enough OO —d | Fic. 67.—Cultivater which can be used to cover weeds in row. Itc, 68.-—Tool for shallow surface cultivation. 14 230 earth to cover the weeds in the row. A good cultivator for this kind of work is represented in Fig. 67. The levelers represented in the rear of the dises are intended to throw Hic. 69.—Two good garden cultivators. the earth back to prevent ridging when the tool is used for ordinary cultivation and ridging is not desired. 281. Garden Cultivators.—T wo good forms of garden cul- tivators are represented in Fig. 69, where the upper one is to be used early, when the plants and weeds are small, and the lower one when the harrow-stage has passed. In the garden as in the field the best time to kill weeds is just. as the seeds are germinating and emerging from the soil and the harrow-toothed cultivator is very effective in doing this. It stirs the surface thoroughly enough to throw the young weeds out and cause the soil close to the surface to dry sufficiently to kill them. Mueh worry and hard work will be saved by the timely use of this or a similar tool. TILLAGE TO MODIFY SOIL TEXTURE. 282. Soil Texture and Tilth.—Texture of soil, like the texture of cloth has reference to the size of the elements which give it its evident structure; and just as the threads of a piece of cotton, a piece of woolen or a piece of silk are WT AJ Fic. 70.—Showing the granular character of a soil in good tilth after cultivation. made by twisting together varying numbers of small fibers, making the threads coarse or fine, so is it with soils; they are comprised of granules of varying sizes formed out of ultimate soil grains which are cemented together more or loss firmly. Fig. 70 represents the textural elements of a clay loam in pretty good tilth. There are shown seven sizes of granules large enough to be readily distinguished with the naked eye, and each size is composed of tine soil grains comented together. All are represented natural size and were carefully drawn from an actual sample taken from a three inch muleh as left after the cultivator. The granules were sorted by means of a series of sieves and the relative amount of cach size of granules is repre- sented by the shading in the vials where it is seen that the largest size constitutes the smallest part of this soil, and No. 5 the largest portion. The finest grade, No. 8, is also largely composed of compound grains, many large enough to be clearly distinguished by the unaided eye, but many more of the ultimate grains whieh were rubbed off from the larger grains by cultivating and during the process of screening. Just as woolen cloths differ when the threads are of the same size beeause some are twisted from finer and others from coarser wool, so soils differ in having their granules made of coarser or finer soil particles cemented together. . Then, too, just as one cloth may differ from another im having its threads loosely twisted, while another is hard twisted, so one soil may differ from another in the degree of firmness with whieh the soil particles are cemented to- gother, Still again, just as one fabrie may be loosely woven while another is fine, so one soil may have its granules more strongly cemented together than another, making it hard to work and heavy while the other is hght and mellow. A sand differs from a soil in being: composed of simple separate grains, usually of rather large size, while a clay is composed very largely of extremely fine granules made from the finest of particles. A soil is in good tilth when its granules are neither too fine nor too coarse, and when they are not too firmly cemented together. 283. Why Good Tilth and Good Tillage Are Important. It is clear from the rounded form of the granules of soil shown in Fig. 70, that when they are massed together with- out being crushed a very large amount of unoceupied space must exist; this unoceupied space ina soil is needed for the movement of air and of water; for the spreading out of the root fibers and root hairs, and for the home of micro organisms Which develop the available nitrogen used by all the higher plants. If the granules are too large and too loosely packed the soil lets the rains fall through it too freely and does not bring it back rapidly enough by eapillarity to meet the needs of crops. Tf the granules are too small and too close then the water moves too slowly, too much is retained by capillarity and there is too little air. If the granules are hound together too strongly, the soil is too hard and the roots are unable to set if aside in making their advance and this lack of freedom reduces the yield. 284. How Texture and Tilth Are Developed._'lhe soil particles are drawn together into the rounded granules by the tension of the soil water in the same way that water forms itself into spheres when sprinkled on a dust covered floor. As long as there are large open spaces in the soil not filled with water the water is all the time drawing: itself to- gether, tending to form spheres, and in this system of pulls the soil particles become involved and are drawn together also. As the water is lost by evaporation and the salts dis- solved become too strong to remain in solution they are de- posited upon and between the grains and granules tending to cement them together. 285. Difference Between Soil and Potter’s Clay... When the granules ofa fine soil are all broken down and separated into their ultimate grains we have the puddled condition so fatal to crops, but the one the potter strives to secure to make his wares close in texture and strong. In the pud- dled soil and potter’s clay enough of the granules have been 234 broken down to fill the spaces between the larger simple grains and finer granules not yet broken down to make a close textured, impervious material in which no plant can thrive, and through which neither water nor air can move. 286. Early Spring Tillage.— The carly stirring of the soil in the spring preparatory to seeding has for its main object the changing of the soil texture so that it will become Ist, warmer, 2d, dryer, 3d, better aerated, 4th, better suited to lessen the rate of evaporation of the deeper soil water, and 5th, to hasten the development of weed seeds so they may be destroyed before the crop is in the way of killing them. 287. The Disc Harrow.—QOne of the best tillage tools yet devised is the dise harrow represented in Fig. 71. There is no harrow which so thoroughly pulverizes a soil in the spring after fall plowing as this tool. When set to work deep the draft is heavy but the amount of work it is doing 250 is relatively large. To put a piece of fall plowing in the best shape the harrow should be lapped half and in doing this the furrow between the two sets of dises will be en- tirely filled and the surface left level. I'rG. 72.--Spring-tooth harrow. Where small grains are to follow corn or potatoes the use of this tool will often make the plow unnecessary. On the upland prairie soils and others naturally mellow, ground for corn may be plowed in the fall and fitted in the spring with tthe dise harrow with good results. 288. The Spring Tooth Harrow.—On new land in wooded countries and where the fields are rough and stony the har- Fic. 73.—Spike-tooth or smoothing harrow, 236 4 row represented in Fig. 72 does good work. Its weight forces it into the soil and the elasticity of the teetin prevent them from being broken, but such tools can never do the degree of pulverizing that the dise harrow accomplishes. 289. Smoothing Harrows.— When the soil has been pul- verized with the dise or other tool and it is desired to leave the surface more nearly even, or where the soil is naturally very mellow, making less force necessary to change the surface texture, then the heavier weights of tilting har- rows, Fig. 73, may be used to great advantage on account of the greater area which may be covered with them in a day and their lighter draft. The planker. 290. The Planker.—It is sometimes desirable to leave the surface particularly smooth without firming it and at the same time to crush Iumps. This may be done by means of a planker made of three to five 8- or 10-inch plank bolted together with their edges overlapping as represented in Fig. 74. The tool is best made of oak plank two inches thick and eight to twelve feet long. Such a tool cannot take the place of a roller where it is desired to firm the ground. 291. The Use of the Roller.—The roller is used chiefly when it is desired to firm the surface and to help cover seed, especially when sown broadeast. In other cases it may be used to crush clods or to compress the furrow slices after the sod plow. Again when a green crop like rye or elover has been turned under for manure, or where coarse litter has been plowed under, a roller is needed to compress the soil and establish good capillary connection with the deeper soil water. It is sometimes used to develop a muleh where grain is rolled after it is up. QO2rF 404 In all of these cases weight is one of the essential feat- ures of the tool. A roller for tillage should have a weight of about 100 Ibs. to the running foot and a diameter of about 2 feet. MIMI Iii Wig. 75.—Two types of rollers. Two types of rollers are represented in Fig. 75, the one made of bars being designed to crush clods more completely and ito leave the surface ridged so as to be less likely to be influenced by the wind drifting the surface soil. 292. The Harrow Should Follow the Roller—Jn most cases when it has been desirable to use the roller to smooth or firm the surface a light harrow should follow 1t quickly in order to prevent unnecessary loss of soil moisture, be- cause the firming draws the deeper water to the surface, the surface temperature becomes higher in the sunshine and the wind velocity wear the smooth surface is greater; ach of which favors the rapid loss of water. 293. Danger in the Use of the Roller—QOn heavy soils, when they are a little wet, injurious results may follow the use of the roller just after planting or seeding on account of the close packing, excluding the air from the seed, which interferes with quick germination. This danger is ereatest Where grain has been sown with a drill, de ’ . . ; . ‘Lhe use of the roller when the soil isa little too wet may also interfere with the formation of nitrie acid in the soil by making it too close and too wet. In sueh a ease the im- mediate use of a light harrow would only retain the moist- ure and make the rate of nitrification slower, 294. The Plow.— The plow as a tillage tool is used for two distinet purposes, Ist, to alter the texture, forming ia, 76.—Showing the principle of the pulverizing action of the plow, from a comparatively hard soil a deep and mellow layer of earth; 2d, ‘to bury beneath the surface weeds and other vegetation or manure where it may decay rapidly and be converted into available plant food. [f you will open a book, placing the fingers upon the fly leaf in front and the thumbs under the fly leaf in the back and abruptly bend up the corner it will be seen that every leaf is slipped over its neighbor. What takes place is rep- resented in Fig. 76. Had pins been put through the book before attempting to bend the leaves the bending would have tended to cut the pins into as many pieces as there were leaves, just as scen in rig. 76. Now the plow has exactly this kind of effect upon the furrow slice; it tends to make it divide into thin layers which slide over one another just as the leaves of the book did, and it is because of this sort of action that a plow pul- verizes a soil as no other tool can. 295. How Plowing May Puddle Soils. When a soil is too wet its granules are so easily broken that the plow is lable to shear all the coarser ones into two, three, or more slices just as the pin has been sliced in Fig. 76, thus destroying its tilth by puddling it. 296. How Plowing May Correct Texture and Improve Tilth.— If a soil has gotten out of tilth, has become cloddy or has been partly puddled there is a shape of mold board, a stage of soil moisture, and a depth of furrow slice which will help to restore the tilth best and quickest. When such a soil is the least amount too dry to puddle the plow will shear it into the thinnest slices; if still drier the layers will he thicker and will form coarser granules. When much too dry no shearing can take place at all, and the furrow slice is simply broken into coarse lumps. [f you bend but a few leaves of the book at a time there is but little sipping, but the thicker the pile of leaves the greater is the sliding and the greater is the tendeney to shear. _ So it. is in plowing, the deep furrow pulverizes bet- ter and puddles worse than the thin slice or shallow furrow. Again if you bend the leaves gently there is little shear- ing, but if abruptly the sliding is great. So if you plow with the low mold board of Fig. 77 you disturb the ¢ilth least, puddled the soil least, and leave the texture coarsest ; but if the steep mold board of Fig. 78 is used there is the greatest danger of puddling if the soil is too wet and the greatest opportunity to pulverize the soil and improve the tilth if the moisture is right. 297. Forms of Plows.— Plows are made with two funda- 240) mentally different shapes depending upon the character of the work which they are expected to do. If the chief object of the plow is to cut a clean furrow slice and turn it over so as to completely cover whatever may be upon the surface a shape represented in Fig. 77 is used, iemang DAS uN Mia. 7.—Pype of sod piow, which pulverizes but little. [fon the other hand the primary object of the plow is to thoroughly pulverize the soil, making it deep and mellow, a form represented in Fig. 78 must be used. Then accord- ing as one or the other of these two chief objects vary in importance shapes of plows will be ehosen whieh are in- termediate between these two extremes. 298. Kind and Condition of Soil and Shape of Plow.—{t must be clear from the mechanical action of the plow that its form should be adapted to the soil. If the soil has + tendency to be too open and porous, and is naturally coarse grained, like the sandy soils, it should be plowed with a steep mold board, a little over wet and as deep as other con- ditions will permit, so as to break down the granulation and secure the closer texture. If the soil is generally too close in texture, is heavy and sogey, it needs the less steep mold board used when the soil is a little dry so as to shear into thicker layers and form granules of larger size. If plowing must be done when the soil is a little too wet 241 use the less steep mold board and plow as shallow as other conditions will allow. If a soilhas become a little too drviand is not pulverizing fine enough, use the steeper mold board and plow deep for this will spht it into thinner layers, make the soil finer, and the tilth better. 299. The Kind of Soil, the Shape of the Mold Board, and the Draft of the Plow.—Since the steepest mold board bends the furrow slice most and pulverizes most, it is clear that the work done is greatest, and hence that the draft will be most. Since deep plowing pulverizes more than shallow plow- ing the work done is more than in proportion to the depth. Since clay soils have more and larger granules which must be sheared in two in plowing than sandy soils do, the labor of plowing must be greater. Since the granules of the soil are not as strong when the soil is moist as when dry it plows much easier, when in good condition. But if the soil has become too dry and yet must be plowed, it should be plowed deeper rather than shallower. This is necessary to pulverize better, to get more moist soil on the surface for the immediate seed bed, and to quicker moisten and bring into condition the layer which has become too dry. 300. The Sod Plow.—The sod or breaking plow is con- structed so ss to reduce the draft as much as possible by doing only the work needed to eut and turn over tne fur- row shee. This ts accomplished by making the mold board very long and slanting so that the furrow slice is bent and twisted as little as possible, as shown in Fig. 77; the chief work being to cut it and roll it bottom up. The extremely oblique edge of the share in the breaking plow reduces the draft in cutting off the roots by allowing the cutting to be done gradually and with a drawing eut, just as it is easier to cut off a limb by letting the blade of the knife slant backward, drawing it across. 249 rly . . » . . ‘The extremety oblique construction of this plow too, makes it easier to hold it steady when passing and eutting off strong roots or other obstruction. Sta 7 at i NX AS LOTT COO Irie. 78.—Type of pulverizing plow with steep moldboard. 301. The Pulverizing or Stubble Plow.—It will be seen from Fig. 78 that this plow has a much steeper mold board and much less oblique plowshare, the object being to bend the furrow slice as abruptly as possible before it is turned over, for this is what pulverizes the soil, giving it the loose, fine, open texture sought. 302. Mellow Soil Plows.—Soils which are sandy and naturally very mellow may be plowed with a plow having the mold board less steep and more like that of Fig. 79 im shape. With such a form as this the team may eut a wider furrow, and thus cover the ground more rapidly, because the draft is less. When soils are very heavy and stiff it may also be de- sirable to use this type of plow, simply because the draft would be too heavy for the team with the type which pul- verized the soil more. Again very loose soils which have an extremely fine tex- ture and tend to clog will often clear better from the less steep mold board because the pressure comes more obliquely against the surtace. 245 303. Draft of Stubble Plows.—The amount of labor in- volved in plowing a field is so large under the best possible conditions, and it is so easy to make it unnecessarily large, that it is important to understand the principles upon which the draft depends. Mr. Pusey in England, in 1840, made a series of trials on the draft of plows in soils of different kinds, using’ 10 different plows. We have combined his results and give them in the table below: Table showing the draft of plows in tests made in England and in America. P P No of Size of Total | Draft per sq. Kind of Soil. plows. furrow. draft. jin. of furrow. Lbs. Lbs. WOAMViSANG! i. sa o8 aieate an wanelnwrncoess 19 |5in. x Qin. 227 5.04 SHMOVELOATAL ec svrsleriad aeenht cise os eho 10) Sri. x Olin 250 DED MO or Soil rch ty ccc Bane Wosisresiee haeniate se 10M) (Sains Olin 250 6.22 Strom plows ee: ws tenn ocoe seisisiser carrier TOS bie Ohne 440 9.72 STIL ay care cnels, ciscest aa Ctereinassis Chace fsa 10 | fin. x Qin. 661 14.69 Sandy loam (J.C. Morton)............ 5 |6in, x “9/1n. 566 10.48 Stitt clay loami@N.(Y. 1850))/ise. soecs... 14 | 7in. x 10 in. 407 5.81 Prof. J. W. Sanborn made an extended series of trials in 1890 in Missouri and later in Utah and the average of all his trials gives a draft of 5.98 lbs. per sq. inch of the cross section of the furrow slice. Separating these trials historic- ally, omitting those in the blue clay in England, the re- sults stand: English trials 1840, mean draft 7.41 lbs per sq. inch. American trials 1850, ‘‘ Pe Re BL 188 een 186 ss “ee La) 1890, oe ae 5.98 ee “ce “oe “ 304. Draft of Sod Plow With and Without Coulter.—A set of trials with a sod plow near the type of Fig. 48, in clover sod 2 years old,when the moisture present was about as high as it is prudent to work the soil, gave results as fol- lows: Size of furrow. |Total draft. had , : , Lbs. | Lhs. Sod plow with wheel coulter......... 5.575 in.x 15.08 in, 296.25 3.524 Sod plow without coulter............ 5.325 in. x 14.5 in, 843.75 4.453 Ditference..... 47.50 .929 Besides doing the work better the coulter diminished the draft 26.36 per cent. 305. Draft of Sod Compared With Stubble Plow.— Another set of trials were made at the time of 804 to compare the stubble type of plow, Fig. 78, with that of Fig. 77, and the results are given below: 13, ee te pa i Draft per Size of furrow. |Total draft. sq. inch, Lbs. Lbs. Stubble plow without coulter........ 5.872 x 14.31 in. 452.4 5.88 Sod plow without coulter............] 5.825 x 14.5 in 348.75 4.453 Difference..... 108.65 981 In this case the shape of the plow altered the dralt 20.9 per cent., and the difference is probably a measure of the difference in the amount of pulverizing done by the two plows. 306. Influence of Difference of Soil Moisture on the Draft of Plows.— A third series of observations wias made on a clover sod with the same sod plow provided with a wheel coulter, but at a time when the soil was dryer than when the other measurements were made. The results found were: Size of furrow. |Total draft.| Draft per Sq. in. : Lbs. Lbs. Clover sod without coulter. .... ..| 6.47 x 11.61 in. 714.35 10.80 Clover sod with coulter..............| 6.418 x 12.47 in. 664.82 8.616 Ditference..... 49.53 2.184 In this set of trials the coulter has reduced the draft 25.34 per cent. Soil rather dry.. AAG Soil in best condition. ~ Difference ......... Sod plow with coulter. Draft per sq. in. Sod plow without coulter. Draft per sq. in. 8.616 10.80 3.524 4.453 po!” 6.347 the plow is very much modified by the condition of the soil. ry. ‘ td , he results show the draft more than doubled when the soil was dryer. From this comparison it is clear that the draft of Wig. 79. moldbourd suited to mellow verizing. Type of soils requiring little pul- 307. The Draft of Sulky Plows.—It js generally claimed that the draft of sulky plows is less than that of the free- swimming types hecause the friction of the sole and land- side is transferred to the well oiled bear ings of the carriage. The few records accessible do not show a material gain, when the influence of the we ight of the carriage and ditvan are not deducted, but where the draft is no greater on the team with the man riding than when w: king, and the plow 15 24-6 ‘an be handled with equal facility, there is an evident ad- vantage in riding plows such as ig. 80. Wig, S8O.—Sulky or riding plow. 308. The Line of Draft.—It is very important in the handling of a plow that the /ine of draft be just right and such that a line connecting the center of draft A, Fig. 81, in the mold board with the place of attachment to the plow bridle shall also lie in the plane of the traces, as shown in 247 the eut by the line A, B, D. If for any reason the line of draft becomes a broken one as A, C, D or 1, 3, 5 or 1, 4, 5 instead of 1, 2, 5 the draft of the plow is made heavier. The greatest care should be exercised to have the length of the traces, or the hitch at the plow bridle such that the plow “swims free,” requiring little or no pressure at the handles to guide it. If a steady pressure in any direction is required at the handles something is wrong and the team is doing more work than is necessary as well as the man holding the plow. 309. The Scouring of Plows.—There are certain soils, whose texture is such that the most perfect plow surface fails to shed them ecmpletely and in such cases the shapes approaching the sod-plow are more suecesstful. But it is a matter of greatest moment that the mold board possess not only an extremely hard finish, so as not to be seratched by stone or grit in the soil, but it must also possess an ex- tremely close texture so as to be susceptible of a very high polish. If the metal itself is coarse grained there will be inequalities even in the bright surface in which the fine soil particles may lodge and thus clog the plow. 310. Care of the Plow.—-l’oo great pains cannot be taken to maintain a bright clean surface on all polished parts of the plow and the necessary care to do this will always pay; this caution is doubly important where the soils are in- clined to clog. Whenever a plow is laid by, even for a few weeks, its bright surfaces should be thoroughly cleaned, wiped dry and coated with a layer of the thick mineral lubricant used for journal bearings, to prevent rusting. - where V is the velocity, P is the difference in pressure at the ends of the column. h is the length of the column. k isaconstant depending upon thesize of the soil grains, the amount of pore space and the viscosity of the fluid. 329. To Compute Flow of Water Through a Column of Sand, Soil or Rock.—Under the conditions where Darey’s law may be fulfilled the amount of discharge may be com- puted by means of the formula derived by Slichter? and given below: 1Nineteenth Annual Report, U. S. Geol. Survey, Part II., p. 202. 2Nineteenth Annual Repert, U. S. Geol. Survey, Part II., pp. 301-822. Be 1 q = 10.22 ahi c. c. per second (1) where p is the pressure in ec. m. of water at 4° C. dis the diameter of the soil grains in millimeters. s is the area of the cross-section in sq. c. m. jt is the coefficient of viscosity. h is the length of the column. k is a constant whose log. is taken from the table, p. 123. and 10.22 is a constant whose log. is [1.0094.] Tf the pressure is measured in feet of water at 4° C., the length in feet, the area of cross section in square feet, the time in minutes and the diameter of the soil grains in a: limeters the formula is .2012 ee _—< cubie feet per minute. (2) If the flow of water. occurs under a temperature of 10° C. or 50° F. the formula may be written ieee ink cubic feet per minute. (3) Problem.— ia, 120, Drainage system of 80 neres, Double lines, malns; single lHnes, Interals, Numbers give length and dlameter of tlle. (After CC, G, Willott, 376. Outlet of Drains... Much eare should be exercised in selecting the location for, and in placing, the outlet. [It should if possible have a free out all as 1 ab: Ay) es 121, rather than to end beneath water as at B. Wra, 11 A, proper outlet for drains By limproper outlet; Cy proper june. (lon of Jateral with qnaing 0, liproper Junction, To avoid injury from freezing in cold climates the last 10 to 16 feet of the main should end in elazed sewer tile or the glazed drain tile; and the outlet should be guarded With masonry and covered with a grating to keep out ani- mals, 377. Connecting Sub-main with Main.—\Wherea sub-main joins a main the connection should be made at an acute angle as represented at O, Fig. 121, rather than at right angles as at D. Tf this is not done silt will colleet on ae- count of the reduced velocity caused by the meeting of the two streams. It is best in such cases to use the manufac- tured junetion tile. 378. Joining Laterals with Main.— The junction of ‘a lateral should if possible be made above the axis of the main, cutting a hole through the main with a tile pick; this is to avoid the clogging of the lateral. Where the fall is great enough to admit of doing so one of the best unions with a main is represented in Fig. 122, the end of the lateral being thoroughly plugged with a stone bedded in clay, or better with 3 or 4 inches of cement. ia, 122,—Method of connecting lateral with main drain, (After Jul. Kuhn.) Where, on account of small fall, the lateral must ap- proach the main low down it should be connected in. the oblique manner represented in Fig. 121 at C. 379. Obstructions to Drains.—The demand for water by trees is so great that they must not be permitted to grow within 3 or 4 rods of a line of tile which has water running in it during any considerable portion of the growing season. Fig. 128 represents two bunches of Muropean larch roots taken from 6 inch tile which they had completely closed. A small rootlet entered at the joint, where it grew, branched 304 and expanded until its fibrils collected so mueh silt as to completely close the drain. The willow, poplar, elm, larch and soft maple are among the trees most likely to make trouble in this way. Wis. 123.—Roots of Buropean larch removed from a 6-inch tile drain, which they had effectually clogged. 380. Laying out Drains.—Careful study should be given to the best manner of laying out a system of drains; the aim. being to secure the greatest fall, the least amount of dig- ging, the least outlay for tile and the most pertect drainage. To secure these results drains must be laid so that no two lines are taking the water from the same territory, the out- lets must be as few as possible and only as large tile used as are needed to do the work. Pic, 124.--Pwo systems for laying out drains. In Fig. 124 drains are laid out by two systems for the same area of 14 acres with the lines 100 feet apart. By the system A 625 feet of 4 inch main and 3,020 feet of 3 inch laterals are required ; while by the system B only 550 feet of 4 inch and 2,830 feet of 3 ineh tile are required to cover the ground so as to secure equal drainage. — It will be seen that in the sys- tem A the ends of all the laterals traverse 50 feet of territory drained by the main. When long lines of tile must be laid, requiring more than one size, three systems have been used: Ist, that represented at A, Wie. 194: Od, that at JA, 125 and 3rd, that at B, 125. In the second case, cover- ing an area 2,000 feet by 900 feet, above the line aa, 9,000 feet of 4 inch and Aaa sy 3"3" 3" VES 3"3" 3° 3'|3|3 313 |3 iiaya a']eye 3 fr |3" 344 [3 a'ja'}a 344 ]3" a A B Fia. 125.— Two systems for laying out drains. 306 9,000 feet of 8 inch tile are laid 100 feet apart; but follow- ing the third system only 3,000 feet of 4 inch and 15,300 feet of 8 inch render the same service with a saving of about $33.00 for tile. Usually no single system can be followed but the slope and shape of the land will require a combination of two or more. 381. Intercepting Surface Drainage.— | very many eases where drainage is required the necessity is caused by the collection of surface vaters from the surround- ing higher lands. It may often be possible in such cases to avoid a large part of the expense of under- drainage by intercepting and controlling the sur- face waters, collecting them into surface drains and leading them away as represented in Fig. 126. In this ease the water is FIG. 126 —Method of intercepting surfac, collected into a surface drainage, AH, surface ditch, “CFromdi¢ch before it reaches the low area and is carried around on the higher ground. It is specially important to use this method in eases where low areas are surrounded on all sides by a rim of land high enough to prevent the con- struction of underdrains. 382. Construction of Surface Drains.—Where surface waters are to be handled as in (881) it can usually best be done by constructing broad and comparatively shallow runways, which ean be kept in permanent grass, the width and slope of the ditch being such that a wagon and mower can readily be driven along and across it. Such waterways should usually be 1 to 2 feet deep and 10 to 15 feet wide 307 with sides sloping gently to a flat bottom which ean carry a considerablevolume of water slowly without being eroded. 383. Intercepting the Underflow from Higher Lands.—In a very large number of eases lands require drainage he- cause of the underflow of water from the adjacent higher land in the manner indicated in Fig. 127. In such cases, ea kee rs Fe < . 0 -$ e <9 - tat uy et Loree 50 who Dene oe, a a eee ae = —=— ———— x ic. 127.—Showing how lines vf tile may be placed at A and B to inter- cept the underflow from the higher land. = when drains are laid along the foot of the hill below the eround water surface, as represented at A and B, much oi the seepage water will rise into the drain and be conveyed away rather than flow on under the flat land beyond. When such corrections as these are made it may even be unneces- sary to underdrain the flat land or when the drains at the foot of the hill do not fully correct the evil the cost 1s made relatively less. 384. Draining Basins Without Outlets.—There frequently oceur sinks or ponds entirely surrounded by rims too high to permit drainage outlets to be constructed across them. Such cases must be met in special ways. 1. Occasionally such basins are underlaid with gravel or sand which is well drained and the water is retained on the surface only by a comparatively thin stratum of clay subsoil. When this is true, one or more wells may be sunk through the clay into the sand or gravel, as represented in Fig. 128, and filled with cobblestone and gravel. Into this underdrains may be led from various directions to collect the water and bring it to the subterranean outlet thus provided. 2. Where several acres must be drained the above method would hardly be practicable even if the under- drainage conditions were favorable. It is possible, how- 308 ever, to arrange in such a manner that a good windmill will drain a considerable body of land, where only the underflow must be dealt with and the lift is less than 20 feet. One method of draining by wind power is illustrated in Fig. 129 where A is one of a number of closed drains i Ire. 128.—Method of draining sinks. leading to a collecting basin, D, which is connected with the well from which the water is discharged through the pump into the drain C. If the area is small or the capacity of the pump large the water may discharge directly into the well, which may be provided with a float to throw the 1G, 129.—Method of draining sinks by wind power, From Irrigation and Drainage.) mill out of gear when the water is getting too low for the pump. ‘The object of the well is to permit the mill to work during the winter. 3. In still other eases it may be practicable to lay the sink off into lands separated by broad, open and rather deep ditches, into which the water from the lands could drain and where evaporation would be much more rapid than from the soil. To inerease the rate of evaporation of water from the ditches lines of water loving trees, like the willow, could be planted, but these would interfere with 309 cropping. The better plan would be to utilize the ground with a crop which would endure the shallow drainage. 385. Lands Requiring Surface Drainage.—There are many wide stretches of very flat land which can only be drained through surface channels. Such are the districts which in recent geologic times were lake bottoms, over which a heavy sheet of close textured clay was deposited. Soils like these have subsoils so close that were there plenty of fall and good opportunity to find outlets for drains the rains could not reach the drains freely enough to meet the needs of crops. — | ae ! Fie. 130.—Plan for drainage of lands of the Illinois Agricultural Company, Rontoul, Illinois. (After J. O. Baker.) The smallest squares are 40 acres; double lines show open ditches; single lines are tile drains. Such fields must be plowed in narrow lands with the dead furrows in the direction of greatest fall in order to provide a quick removal of the surplus rains. Other districts are so flat that the rains have not yet been able to cut sufticiently deep river channels to drain the Helds enough for agricultural purposes. The soil miay be porous enough, even a coarse sand, and yet for lack of natural drainage channels remain ‘too wet to till. 19 310 In such eases deep open ditches must be provided to con- vey the water out of the country, serving as outlets for underdrains laid in the adjoining tields. A district of this type of land drainage is represented in Fig. 150, covering nearly six square miles. ‘The double lines represent deep open ditehes and the single lines underdrains. Another drainage system of this sort im Mason and Tazwell counties, IL., has 17.5 miles of main diteh 30 to 60 feet wide at the top and 8 to 11 feet deep. Leading into these mains there are five laterals 30 feet wide and 7 to 9 feet deep, the whole system embracing 70 miles of open ditch for the purpose of providing outlets for under- drains, O11 CHAPTER: XV, PRACTICE OF UNDERDRAINAGE. The best work in underdraining can only be done by the man who has a thorough grasp of the principles of the art and who has had enough practical experience to make him perfectly familiar with the essential details as they vary with soil, topography, climate and crop conditions. There are many cases of local drainage where the are: and expense involved are small, where the farmer having a fair knowledge of the principles of drainage can super- vise or do his own work, but when large areas are to be underdrained, where the fall is small and the surface con- ditions complex, it will be safest to entrust the leveling and staking out of the mains and laterals ready for the ditcher to a competent and thoroughly reliable drainage engineer, Indeed it will generally be best and miore economical to let the whole job if it is large and difficult to a man of ex- perience who has established a reputation for reliable work. Even in the matter of digging the ditch, and particularly in giving it its finish, as well as in placing the tile, drainage engineers find it difficult to find men who have the pa- tience, the feeling of responsibility and the practical skill to do it well. .\ man who has the right frame of mind and the skill to do this finishing and most important work well is much more to be trusted than the farmer himself who has so many duties to distract his attention and tempt him to rush the job. But while the general farmer should not be encouraged to attempt the draining of large and difficult areas on his 312 own place it is quite important for him to have a clear con- ception of the general principles of drainage and of what constitutes thoroughly good detail practice. Wig, 181.—Showing forms of drainage tools. 386. Means for Determinimg Levels.— As a general rule the laying out of a system of drains should only be at- tempted with good instruments, two of which are repre- sented in Fig. 131. Where a good drainage level cannot be had the best substitute is the water level, one form of which is represented in Fig. 131 and another in Fig. 182; which consists of a piece of gas pipe about 8 feet long mounted on a standard and provided with two elbows ito whieh are cemented two pieces of water gauge glass. When the instrument is filled with water the surfaces in the two tubes stand on a level and can be used to sight across. To move the instrument close the ends of the tubes with corks. As a substitute for the gas pipe a piece of rubber tubing may be used or a piece of garden hose. A less reliable level can be improvised by arranging an arm upon a standard upon which a carpenter's level may be set. Or a still more crude level may be made from a ‘arpenter’s square mounted on a horizontal arm on which a plumb bob is suspended, with which to set the square with its long arm | level. 387. Leveling a Field.— In determining the differ- ences of level, in different parts of a field it is desired to drain, the simplest method for the inexper- ienced person is to lay out the field into squares of 100 or more feet, driving short stakes at the corners. Set the instrument at a, Fig. 183, midway between the stations I-1 and I-2 and record the veading of i Fic. 122.—~Showing one form of water level. the target placed upon the stake at I-1 in the table in the column headed ‘back-sight”’ whiah is assumed for illustration to be 4 feet. Next turn the instrument upon stake 1-2, when its distance below the level is found to be 3.8 feet and is entered in the column headed ‘‘fore-sight.” This shows that the ground at I-2 is 4 ft. --3.8 ft. = .2 ft. higher than station I-1. In the column headed “Elevation” the first station 1s given arbitrarily a hight of 10 feet above an assumied datum. plane to avoid minus signs. ‘The level is now trans- ferred to b and the distance of I-2 below the instrument found to be 4.2 feet which is entered in the column ‘“back- sight” as before. Turning now upon I-3, its reading is found to be 4 feet and this is entered in the column ‘‘fore- sight.” The difference in level between the back sight and fore sight shows the difference in level between the two stations o14 and is placed in the column headed “difference.” The first difference added ito the datum, 10, gives 10.2, the hight of station I-2 above the datum nlanes The second differ- VI NN: IV spot II I - - - t i} ae U ———10:3—ar—10;6 1044 10 AD ral iG, 188.—Showing method of leveling a field, ence, .2, added to the elevation of station I-2 gives 10.4, the elevation of station I-83 above datum. In this manner the level is moved from station to station until e is reached when it is transferred to f and back sights and fore sights taken as before, and entered in the ttable to connect the first line of observations with the new one just begun. Proceeding as. - fore the level is moved from f to @ and then through h, i, j, k and | to m and so on until chen field is all aiid When proceeding from higher to lower levels the differences must be subtracted rather than added to obtain the elevation of the lower station. Fig. 184 shows the relation. of the level to the target rod along a single line of stations shown in profile. 315 Table giving data obtained in leveling field of Fig. 133. Statini. Back-sight. Fore-sight. Difference. Elevation I-1 4 10 I-2 4.2 3.8 nek 10.2 I-3 3.8 4 2 10.4 1-4 4 3.6 +2 10.6 I-5 3.9 38 “a 10.8 1-6 4 3.7 Ay 11 II-6 38 3.98 02 11.02 II-5 3.9 3.995 .195 10.825 II-4 4 4.095 .195 10.63 II-3 4.1 4.19 19 10.44 II-2 3.9 4.26 .16 10.28 II-1 3.8 3.98 .08 10.2 III-1 4 3.6 ee 10.4 ITI-2 3.9 3.96 .O4 16.44 III-3 4.2 3.775 .125 10.565 IIl-4 4.1 4.045 .155 10.72 III-5 3.8 3 93 ai by 10.59 III-6 41 3.625 185 11.075 IV-6 4 4.185 .085 11.16 IV-5 3 84 16 Ml 388. Contour Map of Field.— When the field has been laid out as represented in Fig. 133, and the elevations of the several stations transferred to the map, the figures show at Cr betel: ithe ae Pet a E Pia te ee a, bl APL ieee) g Fig. 134.—Showing method of leveling. a glance where the field is high and where it is low. — If now lines are drawn upon the map through all places hay- ing the same elevation the topography of the field becomes still miore evident to the eye. Such lines are called con- tours or contour lines, and such are the dotted lines in the map. 389. Location of Mains and Laterals.—It is clear from the contour map that the highest station in the field is VI-6 and the lowest I-1. If then we are seeking the steepest fail or gradient for the main it will be found along a straight 516 line connecting these two stations. Of course no field will be found with so regular a slope as this but the principle is no less true for being so simply stated. VI Vv TY, Il IL 1 iG, 1385.—Showing a system of tile drains laid out on the leveled field of Vig. 188. (Krom Irrigation and Drainage.) If such a field is to be drained by placing laterals 100 feet apart about the maximum fall for them, and the mini- mum amount of tile and ditching, will be secured by placing the laterals along the lines of leveling, in which ease the lines I, II, III, 1V, V, VI «will constitute the laterals on one side of the main and the lincs 1, 2, 3, 4, 5, 6 the laterals on the other side, as represented in Fig. 135, Since the lines | and 1 are both radii of the same circle and have the same elevation at their outer extremities the fall or gradient will be the same or .2 of a foot per 100 feet, as shown on the contour map, but along the lines V and 5 the gradient will be .15 feet per 100 feet or 1.8 inches instead of 2.4 inches per 100 feet along the lines I and 1. The fall 947 oul is therefore not uniform for all the laterals nor can it be when they are placed along parallel lines. If the field required drains every 50 féet then a greater mean fall could be secured and less tile would be required if a system like that of Fig. 136 were adopted. IG. 136.—Showing a second system of drains laid out on the field of Vig. 188. (From Irrigation and Drainage.) 390. Laying Out Drains——When the positions of the mains and laterals have been decided the next step is to mark them with “grade pegs” and “finders.” ‘The grade pegs are short, driven securely into the ground just ‘to one side of the intended ditch, and are placed at regular inter- vals apart. ‘To ene side of the grade pegs are placed longer ones called “finders” upon which is to be recorded the depth below the grade peg the ditch is to be dug. 391. Determining the Grade and Depth of the Ditch.—In doing this work the leveling begins at the outlet and the 318 steps are the same as those already deseribed for the field leveling, the results being recorded in a ‘table calling for two more columns when worked out than were needed in the field work. ‘These are indicated in the table below: Table showing Field Notes for determining depth of ditch and grade of drain, Station |Back-sight|Fore-sight.| Difference.|Elevations | Grade line Denn of Outlet 7 — -- 7 i 0 0 4 — 3 10 7 3 50 3.97 3.87 18 10.18 7.12 3.01 100 4,2 3.83 14 10.27 7.24 3.03 150 4.1 4.08 12 10,39 7.36 3,038 200 3°95 3.99 mil 10.5 7.48 3.02 250 4.87 3.82 mp tj 10 63 7.6 3.03 800 4 3.69 18 10.81 7.72 3.09 350 4,25 3.83 stil 10.98 7.84 3.14 400 4 08 4.1 15 11.13 7.96 3,17 450 4.05 3.96 12 11.25 8.08 8.17 500 397 3 95 Au 11.35 8.2 3.15 550 3.75 3 97 -— 11,85 8.02 3.038 11.36 8.44 2.92 600» no 3.74 —) — In Fig. 137, which is a profile of the data in the table showing the outlet of the drain at A, the first. stake at O and the second at 50, ete., up to 600, both the lines of grade and the datum plane are shown. On each numbered stake is given the depth of the ditch below the top of the grade peg, and below the peg has been set the hight of the bottom of the ditch above the datum plane. Since the outlet in this ease is 7 feet above datum and the surface at 600 feet is 11.36 feet the total fall is 11.36 feet — 7 feet — 4.36. But if the depth of the diteh at the upper end is made 2.92 feet the available fall will then be 4.36 feet — 2.92 feet — 1.44. Since the diteh is 12 times 50 feet long the fall will be 1.44 Ta" or .24 feet per 100 feet. At each 50 foot station then the bottom of the diteh above datum plane will be found by == .12 feet per 50 feet. adding .12 foot, to 7 feet, which is the height of the outlet, for that of the second station; then .12 feet added to this gives the third station and so on, ‘thus: 4. 7.12, 7.24,°7:36, 7:48, 7.60, 7.72, 7:84, 7.96, 8.08 8.20, 8.32, 8.44. Ze Fic. 187.—Profile of ditch staked ready for digging, with depths for the ditch at the several stations. If these numbers are subtracted from the hights of the surface of the ground at the respective places the differ- ence will be the depth the ditch must be dug at those places, and the figures which are placed upon the finders for the instruction of the men in digging. These figures are given in the table in the column ‘depth of ditch.” The experienced drainage engineer with accurate tele- scope level makes the details of leveling, establishing the grade and marking the grade pegs simpler than here given but it is not safe for a farmer with a cheap level to follow his methods. 392. Changing from One Grade to Another.—It may hap- pen in laying out the ditch that it is impracticable to fol- low a single grade on account of having to dig too deep in some places or of leaving the tile too close to the surface in others. Suppose in the last profile (891) the ditch was to be 500 feet longer and that in this 500 feet there had been Joy Apvel P[PF G2 UT peynqrusip an 3 TIMOUS—ReT “91J a rise of but 6 inches. It is clear that to hold a single grade, making the upper end of ihe ditch 2.92 feet deep, would require a greater depth in other portions than necessary. but if the grade is changed at the 600 foot station so ag to give a fall of .l ft. per 100 ft. a sufficient depth will be secured and labor in digging saved, iG, 189.—Showling the ditching line and the commencement. of digging. 393. Ditching Tools.— In digging a ditch it is a matter of first importance to have suitable tools; and whatever else is chosen the men should be provided with first class spades, kept sharp and free from rust. ‘The spade whieh gives the best satistaction has a lone, thin, narrow and eurved blade. The curvature is of first importance in giving @reater stiff hess and allowing the blade to be made thinner and lighter, The spade should be narrow and thin to enable the user to force it full length into the soil with the pressure of the foot and so as to be able to leave the bottom of the ditel harrow, removing as little earth as possible, In Iie. {81 are shown two forms of spades, four tile hoes, which are used in finishing the bottom of the diteh and removing the loose earth, and a tile hook, used in plac- ing the tile, The series of half tones shows these different tools in use. 394. Making the Ditch Narrow and Straight.—'T'o make the ditch stright a strong light line is stretehed taut near the surface and 4 inches back from the edge. Lf the diteh is to be only 2.5 to 83 feet deep it need be no wider at the top than one foot, as shown by the length of tile in Fig. 139. Where the ditch must be 4.5 to 5 feet and receive a G inch tile, as shown in Iie. 141, it must have a width at the top of 15 to 18 inches. The ditcher is trained to eut the walls straight with an even, slope to the bottom so as to leave a straight line along the bottom to receive the tile. In Fig. 140 it will be seen that four men are working in line to complete the depth of the diteh whieh is 4.5 feet at the place. 395. Shaping the Bottom and Bringing It to Grade.—In Mie. 141 the man in the foreground is using the tile hoe to clean out the last loose earth and to bring the bottom to grade and proper shape to receive the tile. The grade is secured by stretching the ditcher’s line tight, and on the slant the bottom of the ditch is to be given, and at a known hight above it. It is then only necessary for the exper- ienced man to use a measuring rod to secure the depth and grade desired, digging a main ditch. ‘n in line 140.—Showing four m Fic When the requisite skill and judgement have not been acquired for this work the man is provided with a meas- uring stick with a sliding army which extends at right angles to the rod and long enough to reach the grade line. It is then only necessary to hold the rod or “diteher’s square” plumb to know whether the ditch has the depth desired, 396. Placing the Tile.—\When the ditch has been finished the tile are laid with the tile hook, as represented in Fig. [42. With the aid of this tool they are placed rapidly and accurately without getting into the diteh. Great care should always be taken to turn and shift the tile until a perteetly close joint is made all around. It does not do to simply have them meet on the upper edge, they should fit squarely and closely through the entire circumference and if necessary tile too much warped to permit of this must be discarded, Some prefer to place the tile with the hand, standing in the ditch upon them, covering them as rapidly as laid with + to G inches of earth, taking care to get it thoroughly packed and not to get the tile out of alignment. The greatest care should be exercised to pack the earth thoroughly about the joimts so as to avoid large open cavities through which the water may rush during heavy rains, Washing dirt into the tile. Tile laying should begin at the outlet of the maim, pro- eceding upward to the first lateral, where the junction should be made and tile enough laid in the lateral to per- mit the main to be partly filled. ‘Phe main may: then be earried on until the next lateral is reached, when this should be commenced as before. Care should be exercised not to leave the upper end of an unfinished line ot tile open for heavy rains to wash mud into it. If the Tine eannot be finished before the rain the end may be guarded by closing it with a board, brick or buneh of grass. a 1) the inishing r t and ditel methed of cleaning the Showing ‘oot 9811) 9) Sutsn ‘qoirp 3m) yo doy OY} WOT If} aq q- Oi TACT —SPT “O14 ‘PeTOAND THA OALT daft] oy) TeIR (OUD OT) SUT Jo | 328 397. Filling the Ditch.— After the tile have been placed and covered with the first laver of earth the balance may be put in by any convenient method. iA common and ex- peditious way is represented in Fig. 1453 where a plow is drawn by a team attached to a long evener. For the finish- ing the ordinary road grader makes an efficient tool. Still another n ethed is to use a light board seraper pro- vided with handles to be held against the bank of earth, which is drawn into the ditch by a team on the opposite side drawing from a rope and backing when the scraper is emptied. RURAL ARCHITECTURE. CHART En xe i STRENGTH OF MATERIALS. A knowledge of the principles governing the strength of materials is helpful along many lines of farm practice and particularly in the construction of farm buildings. 398. A Stress.—When a post is placed upon a foundation and a load of two thousand pounds set upon it the post is undergoing or opposing a stress of two thousand pounds. When a rope is supporting a load of one thousand pounds in. a condition of rest it is subject to a stress of one thou- sand pounds. The joists under a mow of hay are subjected toa stress measured by the tons of hay which they carry. 399. Kinds of Stress.——Solid bodies may be subjected to three kinds of stress which tend to break them and will do so if the stress is great enough. These are: 1. A crushing stress, where the load tends to crowd the molecules closer together, as when kernels of corn are crushed between the teeth of an animal. 2. A stretching stress, as where a cord is broken by a load hung upon it. 3. A twisting stress, as where a screw is broken by trving to foree 14 into hard weod with a serew-driver. 400. Strength of Moderately Seasoned White and Yellow Pine Pillars.—-Mr. Chas. Shaler Smith has deduced, from experiments conducted by himself, the following rule for » 330 strengih of moderately seasoned white and yellow pine pillars: Rule.— Divide the square of the length in inches by the square of the least thickness in inches; multiply the quo- tient by 004 and to this product add 1; then divide 5,000 by this sum and the result is the strength in pounds per square inch of area of the end of the post. Multiply this result by the area of the end of the post in inches, and the answer is the strength of the post in pounds. In applying this rule in the construction of farm build- ings the timbers should not be trusted with more than one- fourth to one-sixth of the theoretical load they are com- puted to carry, because the theoretical results are based upon averages, and there is a wide variation in the strength of individual pieces. Table of breaking load in tons, of rectangular pillars of half seasoned white or yellow pine firmly fixed and equally loaded, computed from C. S. Smith’s formula. ass Dimensions of rectangular pine pillarsin inches. ae 5 ae Sig A | 4x4] 4x6] 4x8 4x 4x12} 6x6 | 6x8 | 6x10} 6x12) 8x8) 8x10) 8x12|10x10 | 10x12 $ tons tons fone, fons fang tons jtons | tons | tons 3} 44.5) 59.3) 74.1] 88.9]109.7/126.9)152.3} 182.7] 219.2 34.6) 46.2] 57.7] 69.2) 8t.2/105.3/126.3] 158.6] 190.3 27.2) 36.3] 45.4) 54.4] 69.7! 87.1)104.5] 136 7} 164.0 21.7) 29.0} 36.2) 43.5] 57.9] 72.3] 86.8) 117.4/ 140.9 17.7) 23.5) 29.4] 35.3) 48.4! 60.6) 72.7] 101.0) 121.2 14.6] 19.4/ 24.3] 29.1 40.8} 51.0] 61.2] 87.2) 102.6 12.2] 16.2) 20.3] 24.3) 34.8) 43.4] 52.1) 75.7] 90.8 10.3) 13.7) 17.2} 20.6} 29.9] 37.4] 44.8/ 65.8) 79.0 8.8} 11.7} 14.7] 17.6 25.9] 32.3] 38.8] 57.9} 69.4 In the application of the rule for the crushing load for posts in barn building the length referred to is the greatest distance between any supports which prevent the post from bending. 401. Bearings for Posts.—In order that a post may carry its maximum load it is important that it rests squarely upon its support and that the load carried presses squarely upon the post. If the ends of the post are not square or if the bearing is out of true so that the strain comes upon one edge the carrying power is greatiy lessened. 402. Tensile or Stretching Strength of Timber.— The ten- sile strength of materials is measured by the least weight which will break a vertical rod one inch square firmly and squarely fixed at its upper end the load hanging from the lower end. Below are given the results ot experiments with different varieties of wood, but the strengths vary greatly with the age of the trees, with the part of the tree from which the piece comes, the degree of seasoning, ete. (Blimp pie cote ree €, )00 lbs. per square inch. American hickory...........-. 11,000 lbs. per square inch. Miao lacy. entities ace seer 10,000 Ibs. per square inch. Oak, white aud red. .. ...... 10,0U0 lbs. per square inch. IRoplareerc a tact een ada ace 7,090 lbs. per square ineh. Wibiterpine: sas eis cxcsisees ae 10,0009 Ibs. per square inch. 403. Tensile or Cohesive Strength of Other Materials,— Amoericancast iron)... °° ....-02se-+-4+20- «c-:eee 16,000)to 28,000))bs. per sq- inch. Wrought iron wire, annealed.... ...... ....... 30,000 to 60,00) lbs. per sq. inch. Wrourhtrromowire warden estas cee eeceete 40,000 to 100,000 lbs. per sq. inch. Wrought iron wire ropes, per sq. in. of rope..... 338, 000 lbs. per sq. inch. Leather belts, 1,50) to 5,0U0, good................ %,000 lbs. per sq. inch. Rope wmaniladhostencesm cess tee ome meee 12,(02 lbs. per sq. inch. OPO TOMI Destrasect nts cams et Ler eae 15,000 lbs. per sq. inch. 404. Transverse Strength of Materials. When a board is placed upon edge and fixed at one end as represented at A, Fig. 144, a load acting at W puts the upper cdge under a stretching stress. B — —.- = pene ios Hy Irie. 144. We know from experience that in case the board breaks under its load when so situated the fracture will oeeur 99% ee somewhere near 5-6. Now in order that this may take place there must be, with white pine, according to (402) a tensile stress at the upper edge of ten thousand pounds to the square inch, and if the board is one inch thick the upper inch should resist a stress of 10,000 pounds at any point from 5 to 1; but we know that no such load will be carried at W. The reason for this, and also for its breaking at 5 rather than at any other point, is found in the fact that the load acts upon a lever arm whose length is the distance from the point of attachment of the load to the breaking point, wherever that may be, and this being true the great- est stress comes necessarily at 5. If the board in question is 48 inches long and 6 inches wide, it will, in breaking, tend to revolve about ihe center of the line, 5-6, and the upper three inches will be put under the longitudinal strain, but according to (402), is ‘capable of withstanding 3 10,000 Ibs. = 30,000 Ibs. without breaking; but in carrying the load at the end as shown, this cohesive power is acting at the short end of a bent lever whose mean length of power arm is oiue-half of 4—5 or 1.5 inches, while the weight arm is forty-eight inches in length. It should therefore only be able to hold at W 937.5 pounds, for as BSCE A= WSew A. we have 30,000 «1.5 = W x 48. 45, 000 = 5 = 48 937.5 lbs. whence W = When a board, in every respect like the one in A, Fig. 144, is placed under the conditions represented in either B or C, Fig. 144, it should require just four times the load to break it, because the board is practically converted into two levers whose power-arms remain the same, but whose weight-arms are only one-half as long each. 405. The Transverse Strength of Timbers Proportional to the Squares of their Vertical Thicknesses.—(‘ommon experi- ence demonstrates that a joist resting on edge is able to 999 OOO carry a much greater load than when lying flat-wise. If we place a 2x4 and a 2x8, which differ only in thickness, on edge their relative strengths are to each other as the squares of 4 and 8, or as 16 to 64. That is the 2x8, containing only twice the amount of lumber as the 2x4 will, under the con- ditions named, sustain four times the load. The reason for this is as follows: In Fig. 145 let A represent a 2x4 and B a 2x8. In each of these cases the load draws lengthwise upon the upper half of the joist, acting through a weight- IG, 145. arm IF, W, ten inches in length, to overcome the force of co- hesion at the fixed ends, whose strength, according to (402) is ten thousand pounds per square inch, or a total of 2>< 2 « 10,000 lbs. = 40,000 lbs. in the 2 4 joist, and of 2 « 4>« 10,000 Ibs. = 80,000 Ibs. in the 2 >< 8 joist. These two total strengths become powers acting through their respective power-arms F, P, whose mean lengths are, in the 2x4 joist, one inch, and in the 2x8 joist, two inches. Now we have P5Ge A = "W XW LA, and substituting the numerical values, in the 2x4 joist, we get 4 10,000x 1=W» 10 or 4 10,000 = 10 W, and W = 4,000. Similarly, by substituting: mumerieal values in the ease of the 2x8 joist we get, 8 10,000 x 2 W & 10, or 16 10, 000 10 W, ancl W 16, 000. It thus appears that the loads the two joists will carry are to each other as 4,000 is to 16,000, or as 1 is to L; but squaring the vertical thickness of the two joists im ques- tion we get, for the 2x4 joist 44 16, and for the 2 8 joist 8x 8 O4; but 16 is to 64 as 1 is to 4, which shows that the transverse strengths of similar timbers are proportional to the squares of their vertical diameters. 406. The Transverse Strength of Materials Diminishes Di- rectly as the Length Increases..-1} will bo readily seen from an inspection of ig. 145, that lengthening the pieces of joists, while the other dimensions remain the same, lengthens the long arm of the lever, while the short arm re- mains unchanged; and sinee the foree of cohesion remains unaltered, the lord necessary to overcome it must be less in proportion as the lever arm upon whieh it aets is increased, Thus, if the 2x8 in Iie. 145 is made 20 inches long, we shall have, P< PA W» WA and by substituting the numerical values we get 80,000 2 W » 20 W 8, O00 instead of 16,000, as found in (405), 407. The Constants of the Transverse Breaking Strength of Wood. Since the laws given in 404, 405, and 406 apply to all kinds of materials, it follows that the actual breaking strength of different kinds of materials will depend wpon the cohesive power of the molecules as well as upon the form and dimensions of the body whieh they constitute. The breaking strength of a beam of any material is always in proportion to its breadth, minltiplied by the square of its depth, divided by its length, or Breadth » the square of the depth length and if the breadth of a piece of white pine in inches is 4, its depth in inches 10, and its length in feet 10, we shall have, taking the length in feet, Now if we find by actual trial, by gradually adding weights to the center of such a beam, that it breaks at 18,000 pounds, including half its own weight, the ratio be tween this and forty will be 18, 000 40 ; and as this ratio is always found for white pine, when the breadth and depth are taken in inehes and the length in feet, no matter what the dimensions of the timbers may be, 450 is called its breaking constant for a center load. or other materials this constant is different, and has been determined by experiment and given in tables in various works relating to such subjeets. The following are taken from Trautwine. 408. Breaking Constants of Transverse Strength of Differ- ent Materials.— Woops American ‘White Ash.:caac,.c hss cuiecee nice eae ana eee eee Coa GoOb lise Black Ashen. ceg: Sass meee toca Caceres see Ig Re EEE eee 600 Ibs. American YollowsBinche .sencriccccs tees seer e ec eee EE Oe eee 850 lbs. American, Hickory and Bittor-nite s.aceess cere neeeee ee eee 800 Ibs. archand) Damaracls: #cosaactee ae eee eee eee 400 lbs. be AG) ALB e210} Kham vas atin ier Meee Poe Cena RSS Aa oF Sete em 750 lbs. American White Pinel. crctoae cebcee Cee eee eee 450 lbs. American VellowsPine ss: ) seo alone maces ete eee ee 500 lbs. 1 5X0) 8) C2 aberdeen ear a, War eee senda Mir oie ean Tem I RTI nt Ree tT oe 550 Ibs. American, White: Oak: =s-sanen ascent er ee ree 600 Ibs. American s breadth in inches « Constant in inches ) Breaking load = reaking loac Length in feet. What is the center breaking load of.a white pine 2x12 joists 12 feet long? 9. DIvan) } i= Breaking load = dees ial —— poate 10, 800 Ibs. What is the breaking load for the same 10 feet long? 14 feet long 416 feet long? 18 feet long 4 Solve the same prob- lems for other woods. 410. General Statements regarding the Quiescent Breaking loads of Uniform Horizontal Beams.—If the center quiescent breaking load be taken as 1, then, when all dimensions are the same, to find the breaking load: (1) When the beam is fixed at both ends and evenly loaded throughout its whole length, multiply the result found by (409) by two. (2) When fixed at only one end and loaded at the other, divide the result obtained by (409) by four. (3) When fixed only at one end and the load evenly distributed divide the result obtained by (409) bv two. (4) To find the breaking load of a cylindrical beam, first find the breaking load of a square beam having a thickness equal to the diameter of the log and multiply the result by the decimal .589. 411. Breaking Load of Rafters.—In finding the breaking load of timbers placed in an oblique posi- tion, as shown in Fig. a x , A 146, take the length of the c DIN rafter equal to the hori- Fic. 146. zontal span A, C, and pro- ceed as in (409) and (410), 412. Table of Safe Quiescent Center Loads for Horizontal Beams of White Pine Supported at Both Ends.—In this table the safe load is taken at one-sixth of the theoretical break- ing load. This large reduction is made necessary on account of the cross-grain of timbers and joists and the large knots 308 which weaken very materially the pieces. Where a judi- cious selection is made in placing the joists, laying the in- herently weak pieces in places where little strain can come . upon them, much saving of lumber may be made. Span 10 feet. Span 12 feet. Span 14 feet. Span 16 feet. Breadth. Breadth. Breadth. Breadth. | 2in.| 4in.| 6in.|! 2in.| 4in.| 6in.|| 2in.| 4in.| Gin.|) 2in.| 4 in.| 6in. lbs. | lbs. | lbs. |] lbs. | lbs. | lbs. |] lbs. | Ibs. | lbs. || lbs. | Ibs. | Ibs. ae 240 450) 720 209 400 600 172 344 516 150 300 450 Giecae 540} 1,080) 1,620 450 900} 1, 350, 356 772) 1,158 336 672) 1,008 Birnie 960) 1,920) 2, 880 800} 1,600) 2,400 686| 1,372) 2,058 600} 1,200) 1, 800 0....| 1,500| 3,000] 4,500]] 1,250] 2°500| 3,750|] 1,072| 2,144] 3,216|| 936] 1,872) 2,808 2....| 2,160) 4,320} 6,480]} 1,800) 3,600) 5,400)| 1,544) 3,088} 4,632)] 1,350] 2,700) 4,050 Breadth. | Breadth. | Breadth. Breadth. 4in.]10 in.|12 in.;| 8 in.|10 in. /12 in.|} 8 in./10 in.|12 in.|| 8 in. |/10 in. {12 in. felbsslbs: lbs: | absen lipses| lbs: lbss |mlibsss lose elbseu|slosealel bss ...-| 960] 1,200) 1,440 800) 1,000) 1,200}, 688 860} 1,032 600 750 900 ..| 2,160} 2,700) 3, 240}] 1,800} 2,250) 2, 70U}| 1,544] 1,980} 2,316)| 1,344) 1,680} 2,016 .-.| 3,840 4, 800 5, 760|} 3,200) 4,000] 4,s00]| 2,744) 4,480) 4,116 | 2,400} 3,000) 3,600 ..--| 6,000] 7,500} 9,000}| 5,000) 6,250) 7,500}| 4, 28s) 5,360} 6, 422'| 3,744! 4,680) 5,616 ..| 8,640 10, 800/}12, 960}| 7,200) 9,000}10, 8U0); 6,176) 7,720) 9,264 | 5,400) 6,750) 8, 100 —"— roto, 413. Selection of Lumber to Increase Carrying Capacity.— It is possible to greatly increase the carrying capacity of a lot of joists or of a set of beams by giving attention to the lumber used, selecting the evide ntly strongest pieces for use where it is known the heaviest strains will come. Some- times a joist should be reversed or turned the other side up in order to enable the piece to render its highest service. In the arrangement of joists under a hay bay or granary, where heavy loads are to be carried, the cross-grained pieces and those with exceptionally large knots should be well dis tributed among the stronger ones, making the evidently weak come between those evidently above the average in strength. 414. Braces.—There are two principles underlying the use of braces to give greater strength to lumber. 1. That of equalizing the load, making it fall more heavily upon the 339 stronger members. 2. That of shortening the free span. The first case is illustrated in the rows of bridging used between the joists in a floor. In these cases wheu a weak member is bridged between two stronger ones a pertion of its load, because it vields soonest, is thrown by the bridging upon the stronger, and stiffer floors are thus secured and the breaking of individual pieces prevented. Braces in nearly all cases are, in principle, either posts or else they are suspension rods which allow the strength of the material to be utilized unaffected by the principle of leverage, the stress being a direct. pull or a push, bringing into play the full tensile or crushing strength of the ma- terial. To shorten the free span of an 18-foot joist or timber two feet at each end by means of suitable braces is in- creasing its carrying power 28.5 per cent. It is much more important to pay striet attention to these matters of strength at the present time than in former years both because lumber is higher and often of muecn inferior quality. 415. Constructing Timbers from Two-inch Lumber.—It is often not only cheaper but better to construct Sx10 or 8x12 beams by putting together 2x10 or 2x12 plank, the timber thus constructed cften being stronger than a solid cye would be because weak places are more likely to be distributed so as to give a greater mean strength. It is of course not true that a 10x10 so made would be stronger than a solid timber of the same dimensions if both were of highest gerade lumber. 416. Form of Barn Frame.—[ uring pioneer days, when saw mills were none or few, it was much easier to secure the needed stability for a barn by hewing a few heavy timbers of suitable length and putting them together with braces than it was to use the 2 inch lumber now so common in the frames of dwelling houses. Since the old type of barn frame was depended upon to D340 give the needed stability, little or no support coniing from the siding or sheeting, it was necessary to use large timbers vik ant P INT Sa . nN V INN A) NS \ leat eT ih a nF (aa kia, 147, and to frame them, together and brace them very securely making a structure costly both im material and labor. 417, Plank Frame.—The high price of lumber has led to an effort to imitate the construction of the old hewn timber frame barn in the construction of essentially the same type of frame but using plank spiked together instead of’ tim- bers. This type of frame is represented in Fig. 147, The frame so made is strong and not as expensive as one of heavy timbers at the present prices but it is neither as sunple in construction nor as cheap as a frame for most barns can be made. Now that the conditions which made the heavy timber frame a necessity have disappeared there is no need of imitating it by splicing lumber. 418. Balloon or House Frame.—The reason for not ad- hering to the old type of barn frame is because ir permits of no advantage being taken of the inherent strength of the siding and shecting to give the barn its needed ability to withstand wind pressure, When the two inch lumber used in the plank frame is treated as studding and the siding and sheeting are put on horizontally, and securely nailed, the whole covering of the barn then braces it from all sides and does double duty by largely dispensing with braces. To distribute the plank, using them as studding rather than building them into timbers forming bents, does not give them less power to withstand pressure from within or without and nich less lumber, less nails and less labor are required, Where the building is long and broad so as to require the sides to be tied, bents may be used and made in the ordinary way except that less lumber need be used at the walls. 419. The Round Barn Frame.——T he strongest possible structure for a barn, with the least unount of lumber in its frame and the least special attention to bracing, is secured Coy to PARSB =s/5 TTT Y 0 4 vi i AEA 5 OAA HP EI ite a Dy mE» D = | is 148.— Showing frame and feneral plan for a eylindrical barn. AS barn tloor extending around the silo; B, hay bay; C, granary; and T, tool room. 21 IG. 342 when the barn is made eylindrieal in form and the studding set upon the cireumference of a cirele as represented ia Figs 148 and 149. In this type of barn not only is the smatlest mumber of studding required to form the outer scESES ee, (ie suena Te. f HE ul # HT zs Vo rs oF “ale il Mia, MW9—,Showing frame and general ae of a ecylindrlenl barn, A, dvivewnys behind entitle: By feed alley; Cy, platforms tor cattle, part of the frame but smaller sizes can be used, for the reason that every board in the siding is a portion of a hoop which makes spreading impossible, ‘while at the same time they are arched against the wind and take its pressure with a crushing stress, With barns of this type 2x4 studding set 2 feet apart have ample strength for all diameters up to 40 feet and 2x6 studding is large enough for barns 40 to 100 feet in diam- | eter, ee ie (| 345 CHAPTER XVII. WARMTH, LIGHT AND VENTILATION. CONTROL OF THM PERATURE. The life activities manifested in the animal body involve the continuous maintenance of a train of chemical changes which give rise to or inaintain them, These chemical changes, like all others, can only begin at a certam ten perature; below this they cease; within a certain range they vo forward at normal rates; above this temperature reac tions occur which interfere with the life activities, making them abnormal or causing them to cease, 420. Automatic Control of Temperature..lhe animal body is so constituted that within certain limits the normal temperature of the body may be maintained automatically, if only sufficient food is supplied. If outside conditions are such as to lower the temperature of the body the nervous system reacts, setting’ in operation a train of changes which evolve heat fast cnough to meet the greater loss. Tf on the other hand the surrounding temperatures are too high and the body is becoming too warm the heat producing: reac tions are inhibited or perspiration is stimulated to reduce the too high temperature by bringing the blood to the skin, where the temperature may be lowered by the evaporation of water in the same manner that the wet bulb of a ther mometer is cooled by the loss of heat which does the work of evaporation, 421. Normal Animal Temperatures. The normal temper- atures which must be maintained within the animal body 344 vary with different species of animals but among the warm blooded forms the range is not wide, as indicated in the table below. FLONAG ict ea syieacaedes 100.4°F, to 100.8°F. Cattle ...0.0. ay KO) to 102 SGD wa cen eoterns 101.38 to 105.3 probably 103.6 to 104.4 SWING saiceieseecen esta GLUULe to 105.4 DOS Kiev ks ahah blanc: ease to 101.7 Any marked departure from these temperatures in the animal body, either up or down, results in physiological disturbances which injure the health of the animal. 422. Best Stable Temperature.—The data for a rational practice with veference to this point have yet to be de- termined experimentally. At present rules can be formu- lated only from general considerations. Since most of the bodily functions result in the genera- tion of more or less heat and since the temperature must be kept below 100° to 105° it is clear that no active animal should be surrounded by temperatures as high as the nor- mal temperature of the body. One of the main objects of the circulation of the bleod through the skim is to lower its temperature before it returns to the interior, so that those parts may be cooled. In our ease we become uncomfortable in a surrounding temperature much above 72° and the same Is true of our domestic animals. Stables should then as a rule have a temperature lower than 72° TF. but how much must depend upon eireum- stances. ‘The right surrounding temperature is that whieh will permit the necessary loss of heat from the body with only the normal rate of perspiration. Reasoning from general principles it is to be anticipated that animals which are being fed heavily, like fattening swine, steers or sheep, as well as mileh eows, will do better in somewhat cooler quarters because (1) the larger activity necessary to produce the extra assimilation desired would develop more heat which must. be removed from the body, and (2) beeause the aim is to induce such animals to eat as much as they can convert economically into flesh and milk and warm quarters must make the demand for food less. It has been found with man that when fasting and at rest under a temperature of 90° I. he consunved 1,465 cubic inches of oxygeim per hour, but under the samie conditions except a temperature of 59° I. the amount of oxygen was 15 per cent. greater and the amountof carbon dioxide given off also 13 per cent. greater, showing that a higher rate of constunption of food in the body was maintained and hence that the man would be required to cat more. It is with the cow and fattening animals as it is with a threshing machine, it requires a higher rate of waste of energy to run the machine rapidly than it does to run. it slower, but the saving in time of all employed ito manage the machine more than pays for the greater waste. So the cow may require an extra amount of food for termjperature maintenance to overcome the cooler quarters but she is likely to eat enough more food to enable her to make more milk and a higher profit when all items of expense are taken into account. With animals on simply a maintenance ration the aim is to carry them with the least amount of food and henee in as warm quarters as will be healthful. It seems likely that the best temperature surroundings for animals being crowded will be found between 40° and 50° I. and for animals upon maintenance rations from 50° to 65° or even 70° F. 423. Heat-Proof Construction Impossible.——-No enclosure or building can be so constructed that all the heat it con- tains will be prevented from escaping. If it is kept above freezing through cold winters there must be within the en- closure a source of heat. So, too, no enclosure or building can be so thoroughly made as to exclude all heat and hence it is impossible to build a “cool room” which will not get warmer during the summer unless if contains some means of removing the heat which enters. The out-door root cellar which does not freeze during 346 the winter is prevented from doing so by the heat which enters it through the bottom. The same cellar during the summer grows gradually, warmer as the season advances and is only relatively cool because part of the heat entering above is conveyed through the bottom into the earth, to re- store that which kept the cellar from freezing during: the winter, The warm stable which does not freeze is kept so by the heat of the animals sheltered, and the warmly con- structed stable only makes less animal! heat needed to main- tain the temperature; the walls in themselves are not warm. So, too, no garment however made is in itself warm. We call it warm when the loss of heat through it is slow. 424. Means of Controlling Temperature.—-\When it is de- sired to construct a room which will be warm in winter or one which will be cool in summer the same principles must be employed in each. In the first case it is desired to re- tain the heat produced in the room; in the second ease to prevent heat coming through the same walls, but from the opposite direetion. To secure either of these ends two essentials of construe- tion must be observed. The walls must be as nearly air tight and as poor conductors of heat as possible. In the construction of a warm house, a warm stable, a cool ice house or a cool curing room for cheese the greatest attention should be paid to securing air tight walls because, no mat- ter how poor conductors are put into the walls, if there are eracks about doors and windows or open joints in the wall, the effect of wind pressure and wind suction will be ‘to change the air in the room so rapidly that it will be diffi- cult to keep it either warm or cold. 425. Solid Masonry Walls.—Stone basements with solid walls are sufficiently warm for stables but they are too good conductors of heat to be suitable for dwelling houses in cold climates where the inside temperature must be maintained at 72° F. Hollow brick walls, when plastered with a close textured mortar, through which air cannot pass readily, are 347 better than solid masonry but are not as warm as those well constructed of all wood and good building paper. An unplastered brick wall, or a brick wall plastered with coarse lime mortar only, 1s one of the poorest which can be used either to retain or exclude heat. Its pores are so open that the smallest wind pressure or wind suction causes a ready flow of air through every portion of the wall, changing the air of the room quickly. lor cheese curing rooms, where the temperature is to be held down by means of cold air ducts, masonry wells, even when made air tight, are not suitable because they are such good conductors of heat and so massive that they tend to inaintain a uniform temperature in summer somewhat higher than the mean of the air outside. 426. Hollow Masonry Walls. When stone or brick walls are made hollow they become much warmer in winter and cooler in summer than when built solid because the air is a much poorer conductor of heat. The thickness of the air space is not important and one-half an inch thick is prac- tically as serviceable as one of 6 inches. Where basement or semi-basement curing’ rooms for cheese are constructed the upper four feet of the wall should be made with a dead air space ito prevent the heat of the warm soil as readily reaching the interior. So, too, in the case of dwelling houses in cold climates, whether they have cellars under them or not, it 1s important to make the upper 3 or 4 feet of the wall hollow for the reason that the cellar will be warmer and hence the floors under the living rooms above. 427. Brick Veneered Walls.— Where brick are cheap and lumber high, walls made of 2x4 studding sheeted inside and outside with matched fencing and then veneered with brick make a very durable and warm building. The brick will not decay and the expense of nails and frequent paint- ing are avoided. It does not do to depend upon the brick for warmth, how- 348 ever; they simply take the place of the siding and paint. Where the house is simply sheeted outside with common boards and veneered with briek, and then lathed and plastered inside, the building will be very cold because the wind will go easily through the brick and the cracks in the sheeting. 428. All Wood Walls.— lor the construction of dwelling houses, cheese euring rooms above ground and ice houses there is no type of wall so effective and so cheap im first cost as the all wood wall where good building paper is used with the lumber. For a dwelling house a reasonably warm wall is secured when the studding are sheeted outside and in with one layer of tongued and grooved fencing, covered outside with 2-ply acid and waterproof paper and lathed and plastered inside. The imside sheeting is warmer than back plastering and better because it gives a more solid wall, and lath may be used on it for furring. LIGHTING FARM BUILDINGS. The lighting of farm buildings is required to secure three important objects: (1) facility in doing work; (2) needs of the animals housed, and (3) healthful conditions. In the dwelling house much care should be exercised to secure an ample amount of light in the kitchen, in the dining room and especially in the main living rooms. An abundanee of light is needed in the kitehen not only to facilitate the work but to make the best intentions and efforts toward cleanliness more certain. It. requires an effort to be gloomy and feel ugly in the faee of a hearty laugh, and a bright cheerful room has much the same effect upon those who occupy it. 429. Efficiency of Windows.— There are many conditions which affect the efficiency of windows in lighting a build- 349 ing. Trees or buildings near by, which cover a consider- able portion of the sky, may reduce the light entering a window very much. Much more light comes from the sky high above the horizon than from low down and hence a porch over a window cuts out a very large share of the heht which might entier it. Buildings which have thick walls require larger win- dows to admit the same amount of light as would enter through windows in ithin walls. Basement stables with heavy stone walls require larger windows beeause the walls are thick, and so with a brick or stone house. Windows long up and down admit much more light than windows of the same dimensions with their long axis horizontal because much more light comes from the upper portion of the sky. So, too, windows extending from near the ceiling toward the floor light the room bettier than when extending from near the floor wp. 430. Position of Windows.—Livine rooms and stables should if possible be arranged so that the body of heht may come from the south side where the direct. sunshine may enter the windows. In a dwelling house in the win- ter this is very important because then the amount of hieht is smallest at best and the family must be more closely confined and therefore need the direct sun then most. For poultry and for swine south windows are specially de- sirable. Large windows at the south are not as objee- tionable for heat in summer as might at first be thought. because the sun is so high that a large portion of the direet sunshine is reflected from the glass and previented from entering the house; but during the winter, when.the sun is low, the advantage which comes from its heating effect as well as the light is very considerable. VENTILATION OF FARM BUILDINGS. In the physiological sense air is as taieposable to the cow and horse as is water, grain, hay or grass; so, too, is it as essential to the development of power in the steam engine as is the water and the fuel. It is so abundant about us and we procure it usually so unconsciously that its necessity does not oceur to us. But when large numbers of animals are housed together in close stables ample pro- vision must be made for the ingress and egress of air. 431. Necessity for Ventilation The need of ventilating dwellings and stables grows out of several conditions: (1) The consumption of the oxygen which is the essential in- gredient; (2) the exhalation from the lungs of carbon dioxide, moisture, ammonia, marsh gas (C Hi aud organic matter; (3) the accumulation in the air of occupied stables and dwellings of bacteria and other micro-organisms as well as solid dust particles. 432. Carbon Dioxide in the Air.—This gas is given off from the lungs with each respiration in nearly the same ratio that the oxygen is removed, hence air once breathed is not only deprived of a portion of its oxygen but it is di- luted with an equal volume of carbon dioxide and is there- fore rendered doubly unfit for use again. That air once breathed from the lungs is not. suited to further use can be clearly and foreibly proved by filling a quart Mason jar with air from the lungs, by blemiee through a rubber tube, and then quickly lowering a lighted taper into it, which is quickly extinguished, showing that the air has lost so much oxygen and gained so much carbon dioxide that the taper cannot burn in it. 433. Moisture from the Lungs and Skin.—The moisture taken with the food and as drink musit be again removed vo1 from the body and a large portion of it leaves through the lungs and skin in the form of invisible vapor. If the air of a stable or dwelling is not changed with sufficient. fre- quency it becomes so damp as to interfere with the proper action of the lungs and skin in this respeet, and it is im- portant that the ventilation should be strong enough to prevent the air becoming too damp. One of the surest indications of an improperly venti- lated stable is the condensation of moisture on the walls, ceiling and floors. It is sometimes remarked that cement floor, and stone basements are objectionable because they “draw moisture,” making the air damp. The truth is the stables are insufticiently ventilated and the moisture from the animals condenses upon the cement floor and stone walls simply because these happen to be colder. Instead of “drawing” moisture and making the air damp they have exerted exactly the opposite effect by condensing the moisture from the air, leaving it dryer than if the con- densation had not occurred. 434. Ammonia and Organic Matter Removed from the Lungs.— When one passes from the fresh air into an oceu- pied stable or room where the air has been rendered im- pure from imperfect ventilation a depressed feeling and offensive odor are recognized and sometimes this effect may be so strong as to produce nausea. When these odors and the odor of ammonia cam be detected it is positive proof that the air needs changing more rapidly. Some of the organic matter given off from the lungs is strictly poisonous and so much so as to produce death in a few moments. [Tf a live mouse is kept in a sealed pint fruit jar until it is nearly suffocated, as shown by its action, another mouse introduced into this jar will die at once, while the one which vitiated the air may be removed and it will apparently recover. It appears as if the organic principle eliminated from one animal is more poisonous when breathed by another, even of the same kind. 352 So poisonous is the organie principle removed from the lungs that Brown-Sequard in 1887 condensed the vapor of expired air and injected 15 ce. of it into a rabbit which died from the effects. Brown-Sequard considered the substance a volatile alkaloid secreted by the lungs. Water standing over night in a poorly ventilated room or stable comes to have a very disagreeable taste from the absorption of impurities from the air and this is one of the most serious objections to keeping water standing in the stable for cows or other animals. 435. Micro-organisms and Dust in the Air.—It has long been recognized that the air of old and poorly ventilated houses, especially if they are not kept clean, contains many more dust particles, spores and micro-organisms than newer and better ventilated houses do. The same must be true also of stables but in a higher degree. The amount of dust and of organisms as well is almost always more abundant in occupied rooms than in the open air. This would be expected both because of the slowing down of air movements after entering the house, which acts exactly like a silt basin in a line of tile, and because of their production there from various causes. Strong ventilation tends to remove these organisms and dust particles with the air from the compartments and this is the rational basis for airing a bedroom or any other after sweeping. The air has been filled with both sets of impurities and opening the windows or using any other means of producing a strong eurrent will help to clear the room. 436. Bad Ventilation Predisposes to Disease.—The most helpful health rule which man can adopt for himself or for his domestic animals is to avoid whatever tends to weaken the system and to take advantage of whatever tends to greater vigor. It should be clearly recognized that the germs of diph- theria, of tuberculosis, hog cholera and other contagious diseases are liable to be met with almost any day and in any place and that wherever a proper breeding place may be found the disease is liable to start and from it spread by force of greater numbers of germs. While therefore the micro-organisms usually found in greatest numbers in dusty houses and stables poorly venti- lated and cared for are not in themselves a source of dan- ger, the run-down, weakened condition which poor ventila- tion is sure to engender will certainly tend to start a case of contagious disease and then, with greater numbers of germs in the air to be introduced into the system, animals of greater vigor must succumb to these invisible foes be- cause of their vast numbers. Ample ventilation then should always be secured, first, as an indispensible condition for maintaining the power to resist disease, and second, in case of disease, to both clear the air and to give the animals an opportunity to defend themselves against this type of foe. 437. Amount of Air Respired.—The amount of air ordi- narily taken into and put out of the lungs by man. with each respiration is given by different observers as follows: LGU BOG? cctsteyp betes ce chee stn soe eee at 20) = 80 cubicimchas Valentin: 3.,ntie scsen eerie huecen bes. Ad =92 onbie inches WABLOTOAU: poitaoe -cisaduld 44 aeliinase ea poaeericae, 10° = AD cubic inches CORtMIUIA ger nok hen Mesos ba OL ee ele cubic inches WMSCMINGOM, A.a--'2 7. 2e-2e seein see ene cs ae 1G) — 20leubicdnches AONE Ratt, ah ti econ Gata eta os oe 15.2 — 46 cubic inches or an average of about 30 cubic inches, The amount of pure air which must be breathed in order to supply ‘the oxygen needed by different animals, deduced from Colin’s table, is given below: 354 —d Atk BREATHED IN) |OXYGEN CONSUMED IN ! | 24 HOURS. 24 Hours. ANIMAL, i Per 1,900 Per 1,000 lbs. of Per head. lbs. of Per head. weight. | weight. cu. ft. cu. ft. lbs. | lbs. Mba 2 hice et eee rele 2, 833 425 12.207 1.831 Horse Sq01 of 3, 401 13.272 13.272 OW ert ce ee Cae nae 2,504 2, 804 11.04 11.04 Swine 226 Oks eect katcentaeecnes 7, 3833 1. 103! 29.698 4.456 Shea poccca. cooks ee as aoe mersaenane 7, 259 726 29.314 | 2.931 EEN? saat oe one ne a iecioseeaee mee 8, 278 24.84 24.84 .075 438. Amount of Air Used Compared with Feed and Water.— A 1,000-pound cow requires daily the equivalent of about 30 Ibs. of hay and grain and 70 ‘Tbs. of water or, in round numbers, 100 Ibs. per head and per day of solid and liquid food. A cubic foot of air weighs about .08 Ibs. hence, from the table in (487), we have 2804 < .08 lbs. = 224.32 Ibs. which shows that a eow needs to be supplied with twice the weight of pure air that she does of food and water com- bined. fe are yet ithe sufficiently exact data to permit this problem to be concisely stated for stables used for domestic animals. In absence of exact data and in view of the unavoidable leakage of air through the walls and about windows and doors we have arbitrarily assumed that if the air is changed in the stable at such a rate that it at all times contains no more than 3.3 per cent. of air once breathed fairly good ventilation would be provided. 440. Rate of Supply of Air to Stables. s of (439) the number of eubie feet of air per head and per 355 hour, using the data in the table of (487), wonld be as stated below: PMiorshorsest-.s..ccraee 4,296 cu. ft. per hour per head. For cows.............. 3,542 cu. ft. per hour per head. For swine.......... .. 1,292 cu. ft. per hour per head. Forsheep. <2... -.... 917 cu. ft. per hour per head. Hon ens s..sacerae are 31.4 cu. ft. per hour per head. - 9-0- { erat Me ic. 150.—Simplest method of taking air into stone or basement stable. A B and A B show where the air enters. These flues may be made out of ordinary 5 or 6 inch stove pipe with elbow, or galvanized iron conductor pipe, or the pipe through wall may be ordinary 5 ineh drain tile. with stove pipe and elbow on inside, or the flue may be made of 6 inch fencing. The weights here assumed are 1,000 lbs. for the horse and cow, 150 Ibs. for the hog, 100 Ibs. for sheep and 3 lbs. for the hen. With different weights the amounts would change somewhat in proportion to the size of the animals. 441. Capacity of Ventilating Flues.—With the data in the last section, and the number of animals to be provided with air, the capacity of ventilating flues should be such as to ensure an air movement equal the rate given in the table of (440). It is practicable to construct ventilating flues through which the air from stables will travel at the rate of 200 to 500 feet per minute without mechanical forcing or the aid of heat, other than that derived from the ani- mals in the stable. With a ventilating flue 2x2 fect inside measure 20 cows would be supplied when the current in the flue was at the rate of 295 feet per minute. At this rate 40 cows would 356 need two flues 2x2 feet inside measure; 60 cows three ; 80 cows four and 100 cows five. Mig, MHl.—Modifleation of Mig. 150 where on the right a noteh is left in the wall when building, so that the flue rises flush with the inside of the wall. While on the left side the flue is shown built in the wall, This may be done by building around 5-ineh drain tile or around a box made of fencing. 442. Cubic Feet of Space in Stable per Animal.—It has been customary with sanitary engineers in planning hospi- tals, prisons, school rooms, ete., to allow so many cubie feet of space per occupant, but the number chosen has not Mig, 162.—Method of taking air into a bank barn on the up-hill or bank side. The air flue is made in the same way as deseribed in Figs. 150 and 181, but on the outside has its end covered as represented at A on the lett with a length of 6 or 8 inch sewer tile with its top coy- ered with a enap of coarse wire screen. Drain tile would not answer for the outside exposure at the surface of the ground as frost would enuse it to erumble, Wood could be used and replaced after rotting has occurred, been to supply the proper amount of air but rather to avoid drafts too strong for health and conifort. It should be distinetly stated that in matters of ventala- B57 tion it is cubie feet of air rather than cubic feet of space which should be provided, and in the construction of stables the amount of space need be only so much as is required to permit ample room and freedom to care for the animals. WiG. 1538.—Two methods of ventilating a dairy barn. On the left the ven- tilating flue D F rises straight from the floor, passing out through the roof and rising above the ridge. One, two, or three of these would be used according to number of cattle. The flues should be at one or the other side of the cupola rather than behind it. On the left CE represents how a hay shoot nay be used also for ventilating flue. In each of these cases the velitilating flue would take the place of one cow, This method would give the best ventilation but has the objection of eecupying valuable space. C, in the feed shoot, is a door which swings out when hay is being thrown down, but is closed when used as a ventilator, the door not reaching quite to the floor. To take wir into this stable if it is built of wood with studding, openings would be lert at A abour 4x12 inches every twelve to six- teen feet, and the air would enter and rise between the sheeting of the inside and the siding on the outside, entering at B as repre- sented by the arrows. If the barn is a basement or stone structure the air intakes could be such us described in figures 150, 151, and 152. Twenty cows should not be housed in a space much less than 28x33 feet, with ceilings 8 feet in the clear. In wari Climates there is no objection, except the matter of cost, to high stables, but where it is cold high ceilings per- 22 mit the warm air to rise so far above the animals as to leave the stable cold at the tloor. 443. Forces Which Produce Ventilation.— The movement of air currents into and from a ventilated stable is caused 1. By the wind pressure against the building tending to force air into the stable. 2. By wind suction on the leeward side of the stable tending to daw air out. 3. By aspiration across the top of the ventilator. 4. By the difference in temperature between the air in the stable and that outside. When the wind is blowing against a building there is an increase of pressure above that inside which forces air into the stable through any available opening and then out again on the opposite side or up the ventilating flue. At the same time there is a low pressure on the lee side whieh tends to draw air through any openings on that side. Where the ventilator rises above the roof as a chimney does the movement of air across its top produces a di- minished pressure and the air is aspirated out on the prin- ciple of the aspirator used on perfumery bottles. The difference of temperature causes a difference of pressure because of the expansion making the air in the stable relatively lighter than that outside; and the longer the chimney or ventilating flue the stronger will be the draft, both from difference of temperature and the aspi- ration across the top of the chimney. 444, Essential Features of a Ventilating Flue—.\ ovood ventilating thie must have all of the characteristics pos- sessed by a good chimney. It should be construeted with ur-tight walls so that no air ean enter except from the stable. It should rise above the highest portion of the root so as to get the full force of the wind. It should be as nearly straight as practicable and should have an ample cross section. Stronger currents through the ventilators 359 will be secured by making one or a few large ones than where many small ones are provided, and it is usually best [P'rG. 154.—Second best methed of ventilating an ordinary barn. The air comes il as described in the other figures. and passes out through one or more yeutilators rising against the side of the barn and pass- ing out through the roof, us represented at A C KE. To make these flues if the barn is a balloon frame, the best method would be to secure the lightest galvanized irom in eight or ten foot lengths, and place the studding where the fines are to be, the right distance apart, so that a width of the metal covers the space between two studs. Sheets of this metal nailed on opposite faces of the stud would make an air-tight flue. On the cutside, this metal would be covered with the siding. On the inside in the stable, with the sheeting, but in the barn above nothing would be needed except perhaps an occasional shield to prevent the hay from crushing it in. If it is not desired to carry the flues through the rocf, they may end just below the plate, and the air pass cut through the cupola. The method repre- sented, however, would give the strongest draft. The width of stud- ding used for the fiue would vary with the number of animals to be provided for. to have as few as practicable and not leave the air impure in distant parts of the stable. 445. Location of Ventilator.—The best location for the ventilating shaft is near the center of the stable where 360 such a position will not interfere with the work. It is not often that this position can be utilized, and when it can- ic, 155.—Modifieation of Fig. 157, where the air passes straight out through the roof, instead of being carried in and out through the ridge of the roof. This method weuld give a styvonger current, un- less the ventilator passes straight down to the floor between the cows, as represented in Fig. 158. not it may be located in various places, as indicated in Figs. 153 to 160. 446. Openings to the Ventilator.— The ventilator should reach to the stable floor so that air may enter the shaft from that level. This is very important beeause: (1) The animals not only stand and lie low down but are so consti- tutedas to breathe the impurities directly to the floor where 561 the carbon dioxide tends to remain, because it is heavier than the rest of the air in the stable, even although its temperature is higher. Wic, 156.—Represents a method of carrying the flues up the sides and then along under the roof between the rafters, so as to reach the ridge either under the cupola, or at other places on either side. Suck a flue could be made very tight, by nailing the light galvanized iron on the outside and inside of studding, and rafters, having a sufficient width to give the proper capacity for the ventilating flues, and such a system of ventilation would work fairly well but could not be expected to do as effective service as the methods shown in Figs. 153, 154, 158 and 159. (2) The coldest air is at the floor and the warmest at the ceiling and it is the cold air which should be removed during the winter rather than the warm. There should be an opening provided at the ceiling for warm air to escape when the stable is too warm and when it is desired to force the ventilation at the expense of the heat developed by the animals. Both of these openings should be provided with regu- lating valves so that either or both eye be partly or com- pletely closed. 362 447, Entrance for Fresh Air. When a stable has been made close and warm, requiring attention to ventilation, provision must be made for air to enter the stable as well as to leave it. This may best be done as represented in Figs. 150--158 and 158-160. let a i “ hoe AWN Z\~ a ~ OA A ae F Ch En ES : ( IG = 8 pra NC Sie Sree: [ teh ~li I lig. 167.—Shows method of ventihiting an ordinary barn, where the aic is taken out of the stable through flues built between the stuading and between the joists of the ceiling, the air then rising, through ventilating shafts, made against or as a part of one or more of the purline posts. The air enters at A A and FG, following the arrows and passing out along the lines C D WW. These ventilators, if de- sired, ean be carried out straight through the roof, or may be ter- minated inside under the purline plate, or as represented in the figure. The cross section at the right shows how 2x12’s and 2x6's may be nailed together and placed so as to constitute a purline post, and at the same time a ventilating flue. The two sides of the purline post or ventilating flue are represented closed with sheets of galvanized iron. They may also be closed with well seasoned matched flooring, The number of bends necessary in this plan is an objection, as they interfere with the draft more or less. In all of these eases it will be noted that the fresh air enters at the ceiling, ‘This is for the purpose of mingling it with the warmest air of the stable so as to raise its tem- — -~ _ -~ perature before it falls to the floor, In this way the heat which is wasting at the ceiling is saved and the animals are prevented from lying in cold air, Provision is further made for the air to enter the intakes outside at a distance of 8 or more feet below thie ceiling: so as to prevent the warin air being drawn out at these places by suction or to pass out direetly as it would if they opened direetly through the walls. These openings should be placed on all sides of the stable if possible so as to take advantage of the wind pres- sure at all times in inereasing the draft. It, is better to have many small openings than a few large ones beeause thie cold air is better distributed, lessening crafits. 448. Construction of the Ventilators.— he best form of ventilating flue is that represented in Tig. 160, made of galvanized iron in cylindrical form. Another good form is sfu = aie — ——* —— WiG 158.—Method of ventilating a lean-to stable. The alr enters as rep resented by the arrows at A Bb and passes out through a flue built on the inside of the upright or main barn, This flue may rise di rectly through the roof, ov it may end at as shown In the figure, the air passing through a eupola, If the upright barn bas a bal loon frame, then the space between the studding could) be used is ventilating flues in the same manner as deseribed in’ Wig. 154, These floes could be made tighter by coverng Inside and out on the studding, with the lightest galvanized tron. 364 represented in rig. 157, where the sides are also made of galvanized iron. As a substitute for galvanized iron in this form of ven- tilating flue a good rooting paper may be used, such as the ruberoid roofing made by the Standard Paint Company. 449. Ventilation of Basement Stables.—'There is a general impression. that basement stables are necessarily unhealth- ful. This idea has grown out of the faet that it has been possible to make these stables much closer and warmer than ordinary over-ground forms, and where ample venti- lation has not been provided they have been damp and close. HAY RAO RA RR Shy nen Wie. 159.—Method of ventilating a barn where a silo or granary occupies the central portion, The air enters at A B and the ventilating flues are the spaces between the studding whieh form the walls of the silo, or other structure. The air entering at C in openings left all around the silo, and passing out at D at the top. Where basement stables are well lighted and properly ventilated there is no objection to them on sanitary grounds and they have many points in their favor where the conditions admit of their being easily constructed. Methods of introducing the air into these stables are repre- sented in Figs. 150 to 152. 5 (1a. 160.—Is a section of the cow stable of the dairy barn at the Wis- eonsin Wxperiment Station. A single ventilating fue D I rises above the roof of the main barn, and is divided below the roof into two arms A BD, which terminate at or near the level of the stable floor at A A. These openings are provided with ordinary registers, with valves to be opened and closed when desired. Two other ventilators are placed at B B, to be vsed when the stable is too warm, but are provided with valves to be closed at other times. C is a di- reet 12-inch ventilator lending into the main shaft, and opening from the ceiling, so as to admit a current of warm air at all times to the main shaft to help force the draft. This ventilating shaft is made of galvanized iron, the upper portion being 3 feet In diameter, The covering on the outside is simply for architectural effect, O66 CHAPTER XVIIL PRINCIPLES OF CONSTRUCTION. RELATION OF COVERING TO SPACE ENCLOSED. Tho first cost of a building, when expressed in terms of cubic feet enclosed, is influenced much by its relative di- mensions. 450. Relation of Walls to Floor Space.— The form of floor space which ean be enclosed by the smallest amount of wall is a circle, and Fig. 161 represents equal amounts of floor space enclosed by the circle, the square and the oblong. If the cirele encloses a floor space of 1,600 square feet the length of the outside wall will be about 148.7 feet; the square would then be 40x40 feet and have 160 feet of out- side wall; while the oblong would be 20x80 feet and have an outside wall of 200 feet. 144 ft. 160 ft 200 ft. MiG. W1.—Shows equal areas enclosed by three types of walls. The square which encloses the same floor space as a circle requires 11.44 per cent. more wall, while the oblong whose length is twice the breadth requires nearly 40 per cent. more wall. This means that 40 per cent. more siding, more nails and more paint would be required to cover an oblong building, where the length is twice the width, than would be required for a circular one enclosing the same Hoor space. Comparing the square with the oblong building: it re- quires 25 per cent. less wall to enclose it. From these rela- tions it is clear that wherever it is practicable to avoid long narrow buildings there will be not only a saving in mater- ials but the buildings may more easily be kept warm in winter and cool in summer, and in the case of silos there will be less loss of silage. _COuRT a ae WALK DleSAcE Cpe __ GUTTER oe GUTTER w = AL LLS veer a a 1 3° haste bis] gP 7 FEED PASSAGE | 150 FT D. HARNESS C ASE S. SHOOTS H. HYDRANTS FEED PASSAGE BOX STALL WK10 12x10 8x10 “GUTTER PASSAGE 1G. 162.-Showing the same conveniences in two types of horse barns. In Fig. 162 are represented two plans for horse barns providing nearly identical accommodations. The longer one is 105 feet 10 inches in length, 30 feet wide with 18 foot posts. The second is 75 feet 10 inches x 44 feet and re- quires over 8 per cent. less wall and over 6 per cent. less oor space, 451. Relation of Hight to Capacity.—In the building of barns, silos, ice houses, grain bins and root. cellars the more depth or hight which ean be secured the larger will 368 be the capacity in proportion to roof, ceiling or floor, The material for flooring and roofing a low building is usually no less than is required for a high building and yet the cubic contents are in the ratio of their depth. In the ease of hay barns and silos the capacities increase much faster than the hight because with greater depth of material it is compressed and on this account greater stor- age capacity is secured. Total Outside Surfaces. Lxcess of floor spac A 19189 Sq ft covered by the : ae . Round Barn PAR Above A Above B C 39834" LOIN 87 Total F loor-Space | A 5136 Soft | B 66l6 © Call PGR LD 13300; - Is 1/4 46 ft Radius. \ 2 8ft Posts y Wie, ) 3 -Diagram showing the comparative outside surface and amount of Mlvor space in four sets of barns represented in Figs, 164, 165, 166 an? 167. Pie. 164.—Cylindriea? barn Which accommodates 98 CODGUNS a granary and taal) cows and 10 horses, 16x40 feet, and a 4(0-ten silo. house, each equivalent to a floor space Fra, 165. Buildings whieh shelter 87 cows and 15 horses, 452. Combined and Separate Construction.—The amount of capital required to build and maintain in repair a large number of small buildings is greater than that required for a single consolidated structure providing like accommo- dations. This is clearly illustrated by the comparative chart, Fig. 163, which represents the relations of build- ings shown in Figs. 164, 165, 166, 167. Taking the cylindrical barn as a standard of compari- son, 1t provides shelter for 98 cows and 10 horses, contains a 400 ton silo, a granary 16x40 feet, a tool space 16x40 and storage capacity for all the hay needed; and yet its roof and side area is only 269 feet more than the group of buildings in Fig. 165, which shelters only 37 cows and 15 horses, has no silo, no tool house and not enough space for hay. IG. 16¢.—Group of buildings which shelter 114 cows and § horses. Comparing with the buildings of Fig. 166, their aggre- gate outside surface exceeds that of the standard by an 3T1 area 64x64 feet and yet they provide cramped quarters for only 114 cows and 8 horses. Seas ic. 167.—Group of buildings which shelter 144 cows and 14 horses with tool house aud granary. In the group of buildings shown in Fig. 167, there is an aggregate outside surface exceeding that of the round barn by 140x140 feet, or more than twice, and they have less floor space by an area of nearly 40x40 feet, and the group of buildings shelters but 836 more cows and 4 more horses. In this last group the buildings are both low and narrow, causing extreme wastefulness of lumber. Pic. 168.—Consolidated type of barn showing driveway to second and chird floor. 372 453. Saving of Labor.—It is possible to care for animals with less labor and time where all are brought together under one roof than it is where they are scattered through many buildings and Figs. 164, 168, 169, 170 and 171 rep- resent a consolidated type of barn with composite fune- tions, where all of the stock are brought together under one roof. ee OP ee = =| Fie. 109.—Coprsolidated type of barn showing driveway to first and second floor. Economy in labor is of much greater moment than economy in material because the material simply repre- sents money invested in this case while the extra labor re- quired is a continual expense of a high order. 454. Distribution of Animals in Stables.—The general arrangement of animals in stables must vary in detail in almost endless variety, and individual cireumstances must determine just what is best. Three types of arrangement for cows are illustrated in cross-section in Figs. 150 to 159 under the chapter on ventilation, and Fie. 162 represents two convenient groupings for horses. While Fig. 170 shows one plan of division and arrangement of space in a eylindrical barn. Fic. 170.—Showing plan of the three floors of Figs. 168 and 169, ena ee Aes hie Za soe a re a jae een Bee ora” it aa ee ae ll Fic. 171.—Showing less consolidated type of barn with silo partly outside. 23 374 A combined cow and horse barn with silo outside has the arrangement shown in Fig. 172 and permits the work being easily done. 455. Avoiding the Use of Posts.—In cow stables having a second story it will often be possible to carry tthe floor upon the uprights used to form the stalls or ties for the cows and in this way save lumber by making the same SaaS SS = (SLE ST HARNESS CLOSE =r HORSE STABLE tH il Hi “AWM AZITIY BARN FLOOR DAWE WAY CLEANING MANURE ALLEY Ss [| 7 HAY CHUTE < x MANURE DROP 18 CLEANING ALLEY 7 2 SO oS Se A St —— BS ee Beets >yS—ouu —— i — =) Fic. 172.—Plan of combined cow and horse barn with silo outside. pieces render double duty, and at the same time avoid the inconvenience of the posts and save the space they would occupy. This plan is illustrated in the various figures showing methods of ventilation. a STABLE FLOORS. 456. Essential Features——The essential features of a good stable floor are: (1) Imperviousness to water and urine. (2) A surface sufficiently even to be readily and thoroughly cleaned with a small amount of labor. (3) A durability approximating that of the building itself. (4) Fic. 173.—Rectangular barn showing driyeways to second and third floors. A reasonably low first cost. There are two materials which have been used in the construction of stable floors which fulfill these requirements; they are concretes made either with Portland cement or asphalt. The asphalt is superior to the Portland concrete in being a poorer con- ductor of heat while the cement has the advantage of less first cost. 457. Cold and Warm Floors.——_!t is urged against the con- crete as compared with wood floors that they are cold. The meaning is that they are better conductors of heat and so serve to carry the heat away from the body of the animal ‘apidly. It is true that they do convey heat faster than wood and when used in cold climates without bedding are worse than wood from this standpoint. They are not. as bad in this respeet, however, as many imagine. In the first place the stable ought not to fall below 40° F., and when 376 this is true the floor will only have this temperature and will not lead to inconvenience if other conditions are right. In the second place no animal should be required to le ig. 174.—Reetangular barn with drivew2= to first and third floors. same as Wig. 173: even upon a naked wood floor and when plenty of bedding is provided the cement floor is not too cold fer warm stables kept clean. 458. The Use of Bedding. No farmer whe is attempting to maintain the fertility of his land at the standard of best yield ean afford ito use no bedding or even a scanty supply. He can better afford to overfeed with hay so that the least nutritious portions are rejected and use this for bedding, than go without, because the extra amount of manure made and the greater comfort and cleanliness of his animals will pay a good return for it. The waste roughage of the farm, when used as bedding and mixed with the manure, in- creases. the value of both because it increases the ‘total quantity of manure so much that the fields ean be dressed more frequently, thus holding the humus content higher 377 and the soil in better tilth, both essential conditions for large yields. The liability of animals to kick the bedding off from the floor is not a sufticient reason against cement floors. It is only when too little bedding is used or it has not the right texture that the floor is left seriously exposed. 459. All Wood Floors.—These floors are generally laid in one of two ways, either close upon the ground, nailed to stringers bedded in the earth; or else upon joists with an air space between the floor and the earth. | When laid in either of these ways they are certain to wear out through the tramping of the animals and the use of the tools in cleaning the stables, but if conditions are favorable so that rotting does not occur 'they may last as long as 6 to 12 years. It is oftener true that wood floors give out from decay before they do from wear. Where the floor is kept con- tinually saturated with moisture it will not decay; and when kept continually dry it gives out only through wear, but when it contains the right amount of moisture ithe growth of moulds, causing the decay, takes place. When the floor is bedded in a close textured clay soil, where the subsoil is close and all the time saturated with water, decay will go on very slowly; but where the soil is dry and open, and especially if this is the character of the subsoil, decay may destroy the floor in 3 to 5 years. So, too, where the floors are laid upon joists on the ground and a dead air space left beneath, decay is certain to occur in 3 ito 5 years, but if the joists are so arranged that there is free circulation of air beneath, destruction from decay is not likely to oceur. 460. Making Wood Floors Water Tight.— Wood floors are made so as to prevent water from running through them by using more than one layer with some waterproof com- position between them. For heavy floors matched plank are laid and coated with a layer of coal tar roofing com- position and then upon this a second layer of plank is laid, painting ithe joints with the same composition before drawing them together, Lighter floors ave made in the samo way, using tongued and grooved flooring. 461. Stone Floors.— Thoroughly durable floors for cow and horse stables are made by bedding in elay rounded cobble stone, 4 or 5 imehes in diameter, and using upon this an abundanee of bedding. — The uneven surface holds the bedding so well that the animals are fairly comfortable and neither wear nor decay will destroy them. The most serious objection lies in the difficulty im maintaining elean- liness. Where a good gutter is made behind the cows and a row of eut stone 10 or 12 inches wide are set for the hind feet to stand upon a durable and quite satisfactory floor is se- cured, 462. Macadam Stable Floors. \ floor more even in sur- face than (461) can be made out of carefully constructed macadam work, such as is used in making stone: roads, giving ita thiekness of 5 or 6 inches. Where this is used there should be provided cement gutters and mangers as represented in Fig. 175. Wa. 75. Shows method of making a maeadam stable floor with cement mangers and gutters, Before laying sueh a floor the ground should be shaped and made thoroughly hard by tramping or ranining. The crushed stone should be put on in two layers, thoroughly compacting the first layer and filling the voids with sereen- 379 ings before the surface layer is made. Indeed the method should be the same as that followed in making a good stone road. 463. Macadam Surface for Barnyard.— The paving or flooring the barnyard with macadam surface is perhaps the best solution of the difficult problem of maintaining a hard dry yard. = On account of the puddling of the soil by the tramping of feet, surface drainage is all thar ean be adopted and hence even when the yard has been macadamized it is necessary to scrape the manure into piles so that. the water may flow away. CONSTRUCTION OF CHMENT FLOORS AND WALKS. 464. Kinds of Cement.— There are two classes of cement on the market, Common and Portland. Of the common cements in the United States familiar brands are Akron, Louisville and Milwaukee. = They are suitable for laying walls below ground and plastering cisterns but will not answer for stable, cellar or creamery floors, nor for walks, because they do not make a hard enough stone. For walks and floors some brand of Portland cement, should be used. These are American, Knelish or German according to the country in which they are manufactured. American brands are Vuleanite, Alpha, Atlas and Wol- verine, 465. Cement Concrete.—The making of cement conerete is in effect the production of artificial stone by binding: to- gether pieces of rock and sand with Portland cement. The cement is too expensive to be used by itself for ordinary work and the making of cemen! concrete aims to produce the largest bulk of strong rock with the use of the least pos- sible amount of the more costly cement. This is secured when only so much space is left between the materials bound together as will leave room for the cement to form SSO a thin layer between the faces of the fragments to be joined together, 466. Materials for Concrete Floors. ‘lhe materials used for coment walks and floors should be (1) as large, clean fragments of hard roek as ean be readily mixed and worked into the forms and thickness of layer desired; (2) a finer grade of erushed rock or eoarse clean gravel which will readily pack into the voids between the larger fragments 5 (3) a clean, coarse, sharp sand to fill the pores between the fragments of gravel or fine screenings; (4) enough Port- land cement to fill the space between the sand and bind the Whole together; (5) and finally, water enough to wet all surfaces, fill the pore space of the cement and make the mortar plastic, 467. Presence of Earth, Loam or Dust.—It is of the great- est Importance that all of the materials used be perteetly clean and free from dirt or other fine grained material having the texture of ithe cement itself. Tf a tine dust is present in the roek, gravel or sand it will tend to form a laver over the surfaees of the fragments whieh prevents the cement from coming in contaet with the pieces whieh are to be cemented together and a weak conerete results. The fundamental is to have nothing but hard rock frag- ments hirge enough to be cemeniled together and nothing fine present but the cementing material itself, In the conerete pavements used on the streets of London, and which have a mueh longer life than the best paving blocks, great care is taken to wash out of the crushed granite and its sereenings all dust particles before using them, although the dust may be from the granite itself. 468. Wetting the Crushed Rock Before Use.—'There are {wo important reasons why erushed rock or coarse screened eravel, to be used as the body of conerete, should be wet be- fore mixing with the cement. ‘These are (1) to displace as much adhering air as possible, and (2) so as not to draw 38 I out from the cement ithe water needed to maintain its plasticity and to assist in the setting. If the coarse materials are mixed with the cement dry a large amount of air will be set free and entangled in the conerete, Which will prevent all spaces being filled, but the chief difficulty comes from the am preventing the cement from adhering to the surfaces. So strongly docs air adhere to coarse sand that it must be boiled some time under water before it is all removed. 469. Ratio of Ingredients for Concrete..—'The amounts of ach ingredient required to make a solid conerete with all spaces filled depends upon the pore space in the different materials, ‘Trautwine assumes that for each ingredient the voids are near enough to 50 per cent, so that as a safe work ing basis this should be taken, To make a cubie yard of conerete it would be necessary to use, on Trautwine’s basis, Crushed rock, Gravel or sereenings, Coarse sand, Comment, 27 cu, ft. 3.5 cu. ft. 6,25 cu. ft. 3.125 cu. ft. This ratio for pore space is certainly larger than is likely to oecur and for farm purposes it will be safe enough to take the ratios of Crushed sock. Gravel or sereonings, Sand Coment 27 cu. ft. 12.69 cu. ft, 5.58¢eu ft, 2,122 cu, ft. These figures assume the pore space of the rock to be 47 per cent., of the gravel 44 per cent. and of the sand 38 per cent. 470. Ratio of Ingredients for Finishing.—Where good plastering sand is used for making the finishing surface the pore space to be filled will be about 85 per cent. and this would require a little more than one of cement. to three of sand, and unless there is some gravel or screenings to use with the sand it will be safer to make the facing 2 of sand to 1 of cement. 471. Thickness of Floor.—For most stables where the ground has been well firmed and shaped a thickness of 4 inches of conerete and one-half inch of facing will be enough; for house cellars and for the bottoms of silos 3 inches of conerete and one-fourth ineh of facing will do. For creameries and milk rooms the conerete better be 4 inches and the facing a full half inch, made rieher in ee- ment, in the ratio of one to one. 472. Making the Concrete.—The cement, sand and gravel are put together dry on a mixing board and thoroughly worked over, then enough water added to make a stiff paste. The right amount of crushed rock is thoroughly drenched with water and the whole mixed by shoveling until the rock is thoroughly meorporated with the cement. 473. Laying the Concrete.— The floor of the stable should first be given the proper form and very thoroughly tamped so that no settling shall occur after the floor is laid. The conerete should be laid in blocks four or five feet. square, building alternate blocks first, Fig. 176, so as to give time SZ EE) ZEA Wer. 176.—Shows method of laying cement floors in blocks to prevent cracking. for setting and prevent a strong union of the blocks. — If the floor is not laid im this manner shrinkage eracks will occur. The conerete should be made only as fast as used » > VO” and should be thoroughly rammed until the fine cement shows as a layer on the surtace. After standing a short time, but before the concrete has set, the finishing surface should be applied and thoroughly troweled until it is even and smooth. Fig. 177 is a cross section of floor and mangers. Fic. 177.—Sbhows cross-section of cement stable floor with mangers and gutters. For a cellar or creamery floor, where it is desired to have a fine smooth surface, easily cleaned, after troweling, it may be wet with a whitewash brush and some pure dry ce- ment sprinkled over, which is troweled until it is hard, smooth and glossy. When the second series of blocks in a given tier is made and the surface finished it is necessary to eut through the finishing layer exactly above the joint in the conerete, to prevent cracking, and then neatly round the joint. 474, Cost of Materials for Cement Floor.—T aking mater- ials at the prices given and the concrete 4 inches thick, made in the proportions of (469) the cost per 100 square feet of floor, and the amount of materials will be as given in the table below: The floor made of wood 2 inches thick, laid upon 2x6’s, 16 inches from center to center, would cost $4.12 or $4.95 per 100 square feet when the price is $15 or $18 per thon- sand. This makes the concrete 99 cents per 100 square feet more than the lumber, comparing the lowest prices in each case, and $1.72 more, comparing the higher prices. os Material required for 100 square feet of concrete floor 4 inches thick with one-half inch of facing. Material. Amount. Cost per 100 sq. ft. Crushedyrocles. -cnentncn ncteenete 1.23 cu. yds.......| $ .80 percu yd. $ .984 Sandfandtorave beeen ee aeacleieee ede IC Un Cl Senet 50 percu. yd. — .365 Gemie nit) X sissies awe serie = eee etiereeter Sl OLCWibreserolnes 1.00 per cwt. 3.760 Potala o- eco aLee Crushedirock fen eeee ee ce eee EC iCUN VO Saeacere te AOU mpeMmCUliVGumel aad Styaveleheel iti lecousnoaecosssadenancosl alos CMls \KSlSs amcces .15 percu. yd. .5p Cementenceee cee t conc bee saree SUIGEC Wits cameras 1.30 per cwt. 4.89 dl Boy eta) (Ree ems oe Aeetnn =, irk we eran ney al cae eS ge Men ORCI Thos Lena Gea Nae Oe OR ON Where crushed rock cannot be had, but coarse gravel and plastering sand are available, a good floor can be made, but more cement must be used, usually 4 of sand and gravel to 1 of cement. TIES FOR CATTLE. The methods of tying cattle must vary widely with the taste and objects of the owner. The essential objects to be secured are: (1) comfort for the animals. ‘This is neces- sary whether the main object is milk, breeding or beef ; (2) cleanliness, and (3) economy of time in tying and of space. es FiG. 179. FI stauchion. 475. The Stanchion.—There is no tie for cows, if we ex- cept the plain halter or rope, which has been so universally 90” oOo” used as one of the forms of stanchions represented in Figs. 178, 179 and 189. It is the simplest, cheapest and most ex- peditious tie invented and the swinging forms which per- mit the yoke to turn and to move a little back and forth provide a reasonable amount of comfort; and where the width of the platform is adapted to the size of the animal they secure as high a degree of cleanliness as is practicable. Fie. 180.--Thorp stall. {FiG. 181.--Drown + tall. 476. Adjustable Stalls—The four stalls represented in Figs. 180, 181, 182, and 183 are designed to give the cows the maximum amount of freedom of head movement but to force them to stand close enough to the gutter to prevent the platform being soiled. The manger or the head of the stall is made adjustable so as to crowd the cow back against the chain in the rear which confines her. Practically there is no form of tie which can prevent the cow from soiling the platform upon which she stands on account of the un- changable habit of shortening the body by humping the back when the evacuations oceur. VL WY) Na Len aaa WAN wy a -— Fic. 182.--Roberts stall. Fic. 183.--Bidwell stall. 386 The two stalls, Figs. 185, 186, have been designed to se- cure cleanliness in spite of this habit. In the Newton tie it is expected that while the cow is standing the yoke to which she is tied will foree her back sufficiently to prevent the difficulty. In practice, however, there is necessarily so Fig. 184.--Baker tie. Fra. 185.—Newton tie. much freedom at the neck that the object is not secured. The Model tie” provides a bar on the floor, just in front of where the cow’s feet are forced to be while standing and feeding, and which is so much of an obstruction that im order to lie in comfort she steps forward enough to he on the clean bedding. Fig. 186.—Knapp tie Fic. 187.—‘‘Model tie. 887 477. Movable Halter Ties.— Another class of ties repre- sented in Figs. 184, 188, attempt to confine the cow in movements forward and backward by using a short chain which slides at the other end in such a manner as to per- mit freedom of motion up and down. ey eee Fia. 188.—-Chain tie. Fria. 189.—Rigid stanchion. 478. Tight Side Partitions.—here is an effort among some feeders to prevent the animal from moving sidewise so as to interfere with the neighbor, either by stepping uponthe feet or teats of the cow lying down or of taking the food from the manger. Where such provisions are insisted upon it should be kept in mind that anything which tends to enclose the cow, especially her head, in a tight box tends in a high degree to defeat the purposes of good ventilation by confining the air once breathed about the animal, hence such arrangements should be slatted or else open at the level of the floor. So, too, wherever box stalls are used these should be slatted or open at the bottom and not “boxes” as they too often are. 479. Tying for Feeding Only.—For calves, young cattle and feeding steers there is perhaps no mode of confining the animals in the stable so good as to give them complete freedom except at the time of feeding, using plenty of bed- ding on a cement floor which is cleaned as often as needful. g 388 In such cases the stanchion tie is the best as everything is then reduced to the simplest conditions. 480. Mangers.—One of the simplest mangers for feeding cows is represented in Fig. 177, and when made of cement as represented in the cut it is the best for feeding, cleaning and watering, where large: numbers of animals are to be handled with the greatest economy. The manger should have an inside width of at least 2 feet, a depth of 8 imches and should have its bottom 3 or 4+ inches above the plat- form upon which the cows stand. 481. The Manure Drop.—This should have a width for adult cows not less than 18 inches and not more than 20 inches. Its depth next to the animals may be 8 inches and on the rear side 6 inches. These dimensions give ample capacity to prevent the walk behind from being soiled and make it easily cleaned. On some accounts a depth of 6 inches next to the cows and 6 inches in the rear is best; and where a wagon 1s driven behind the animals to clean the stable a depth be- hind of only 4 inches gives less hight to lift the manure. PROVISIONS FOR WATERING. Where there is a well of ample capacity, and 30 or more cows are kept, the best arrangement, everything considered is to pump ‘the water from the well at the time it is needed. This plan provides water that is both fresh and natural temperature, and does away with expensive storage tanks. In ease the power is pumping waiter faster than is needed it is a simple matter to provide an overflow, returning the water to the well. 482. Watering in the Barn.—In climates having severe winters it is best, if practicable, to water the animals in the barn, and where a good fresh running stream can be 389 maintained the ideal way is to have the water before the cows all the time so that it can be taken when desired. It is not desirable to keep water standing before the cows continuously as it is certain ‘to become foul; but it may be maintained during the greater part of the day if the drink- ing basins or troughs are emptied clean each evening. 483. Methods of Watering in the Stable-—We have seen but two reasonably satisfactory methods of watering a large number of eattle in the stable, and these are either to clean the manger and run the water into that or else to have a special long watering trough used for that alone. Pie. 190.—Simple arrangement for watering cows in stable. The simplest arrangement of special trough is repre- sentedin Fig. 190, and extends the full length of the stable, the water coming to it from above so that the supply pipe is entirely above ground where it can be gotten at and can be emptied at once after using. The trough is covered its entire length with a hinged lid, but in front of each cow the lid is ent so the cow can raise a section with her nose when drinking, letting it fall when she is through. 484. Storing Water in Tanks.— Where there is a basement barn the best arrangement for a storage water tank is a 24 390 cement lined cistern beneath the surface in the hill above the barn. Such a cistern is less expensive, 1s a permanent improvement and will keep the water warm and clean. We have seen cases where a satisfactory cement lined cistern is built entirely above ground and then covered in by grading a mound of earth about and over it suticient to make it frost proof. Such a cisterm should be provided with a man-hole so that it may be entered if necessary. 485. Watering Trough.—Where stock is watered in the yard a good arrangement for winter, where the ground is porous, is represented in Fig. 191. The tank is a galvan- ized cylinder 3 or more feet in diameter and 5 feet deep which stands in a dry well 15 or more feet deep and so ar- ranged that the warm air from the bottom of the well all the time surrounds the tank and keeps it from freezing. Water may be pumped into this direct or it may be sup- plied from the bank cistern. When it is necessary to empty the tank the plug can be removed and the water al- lowed to drain into the dry well. Fic. 191.—Representing a storage reseryoir and drinking tank arranged to ‘ avoid freezing. It is of course important to provide a warm jacket about the tank and cover, as represented, so as to assist in keeping the water warm. Go jae ARRANGEMENTS FOR UNLOADING HAY. 486. Unloading Direct from Wagon.—Where the hay is not to be litted and can be rolled directly from the wagon with the fork into the bay, there is no simpler and more ex- peditious way; and where the load can be driven to the top of the barn, as represented in Figs. 168, 171 and 173, there is little need of other mechanical arrangements. iil ie hy iy ‘in ~~ ah i a Vis , ily ti Hh a Wi Fie. 192.—Curved track and hay carrier for use in Gulingric al barn. 487. Unloading Hay in Cylindrical Barns.—Where the cylindrical type of barn is used there are two methods of distributing the hay; (1) that represented in Fig. 192, where an ordinary hay carrier is moved over a curved track and (2) that re presented in Fig. 193, where an ordinary hay carrier delivers the hay upon a central inclined plat- form, which is turned about by the operator in the bay so as to deliver the hay at any desired point. 488. Tilting Hay Distributor.—It is possible to take ad- vantage of the principle illustrated in Fig. 193 for distrib- GRANARY 4 ; ae aR Jt Pie. 193.—Ordinary hay carrier and revolving platform for distributing hay in eylindrieal barn, Fic. 194.—Representing a movable, tilting platform for distributing hay in rectangular barn. uting hay in ordinary rectangular barns, whose timbers are not in the way. Fig. 194 represents a tilting platform, which rocks upon two bars carried by four cables secured to pulleys which roll along tracks or cables secured to rafters, as shown in the cut. With this arrangement hay may be dropped at either side or in the center of the bay, as desired. CHAPTER XIX. CONSTRUCTION OF SILOS. 489, Conditions Essential for Preserving Silage.— The only conditions necessary for preserving good corn and clover silage, are close packing in an air tight strueture when the materials have reached the right stage of matur- ity. Whatever means may be adopted to exclude air from these materials will preserve them as silage. If air ean find access to it spoiling will be inevitable and the rate and extent will be greater the more readily air can gain access. 490. Depth of Silage.—'The depth of silage should be made as great as practicable (1) beeause in this way the largest amount of feed per eubie foot may be stored. (2) There is less loss relatively at the surface. (38) The strong lateral pressure forces the silage against the walls so closely that less air enters and henee there is less loss, 491. Silo Walls Must be Rigid and Strong.— ‘The outward pressure of cut corn silage when settling, at the time of filling, increases with the depth at the rate of 11 Tbs. per equare feet for each foot of depth. Ata depth of 10 feet the lateral pressure is 110 Ibs. per square foot, at 20 feet it is 220 Ibs, and at 380 feet 830 Ibs. Because of this great pressure silo walls must be made very strong when they have a depth of 20 or more feet, It is difficult, to make deep rectangular silos whose walls will not spread as represented in Fig. 195, and where this takes place the walls are crowded away from the silage so much that air can cirenlate wp and down next to the walls and this results in heavy losses, ~ oo! In cireular silos the pressure is sustained by the tensile strength of the materials in the walls, which gives them the greatest possible advantage. Wig 195.—Ilustrating how the bulging of reetangular wood: silo walls allows air 10 come down the sides between the walls and the silage, causing it to spoil, The amount of spreading is exaggerated in the figure for clearness of illustration, but it is none the less real. 492. Silo Placed Deeply in the Ground.—IJn most cases it is best to allow the silo to extend as deeply into the ground as convenience in removing the materials will permit. This ean always be as much as 3 feet below the feeding floor and in the case of bank barns where the silo can be placed in the 5396 hill a depth of 11 or more feet ean easily be secured, Placing the silo deep saves elevating the silage so high when filling and a large portion of it is below frost. Coan ace UY LWQOy LAS VOD ISSINT OM IIE LENO. Ces Ga CS Ie a Ge ONE FOOT ARH HRC at SS ASSES EI EL YY I” ~ i. a SHON § Wie. 16.—Showing an all-stone silo with conical roof and openings for feeding doors; the heavy black dots 1, 1, 1 show where iron rods may be bedded in the wall to prevent cracking from the pressure of the sllage. Method of constructing silo door and door jamb for stone stlo. EX shows cross section of silo door, FE shows how the door jamb is made to make it air tight, and how the door is held in place with lag bolts against a gasket of ruberoid rooting. 493. Protection Against Frost.—It is not necessary to build a silo so as to be entirely frost proof in cold climates, but it will pay to build them reasonably wann where they are to be fed from during cold weather. The freezing of silage does not injure it seriously but it is not well to feed it when frozen. If a silo is not to be opened until warm weather no special attention need be given to warnith. If a silo is 10 to 13 feet in the ground and only 20 feet above ground, the settling and the early feeding before severe cold weather will usually have carried the surface of the silage so low that little inconvenience from frost will be experienced even in stone silos. In all the wooden silos, ex- cept the questionable stave types, the construction needed for strength and to keep the air from the silage will usually be a sufficient protection against frost. CONSTRUCTION OF STONE SILOS. Whenever stone can be had on the farm suitable for building purposes these may be used in silo construction, thus converting idle into active capital. So far as the silo itself is concerned no better or more durable material can be used, and where it can be 10 to 13 feet in the ground the inconveniences from freezing will be small, and the stone silo will be found one of the cheapest of the thor- oughly good forms. Great pains should be taken in build- ing the walls to fill all spaces between stones solid with smaller ones and mortar and to have them. thoroughly bonded in order to secure strength and prevent cracking. 494, Laying the Wall.—The portion of the silo wall which is below ground better be about 2 feet thick and laid in one of the cheap brands of cement rather than lime, the cement being desirable because lime mortar becomes hard so very slowly in heavy walls, especially below ground. After the wall is two feet above ground good lime mortar may be used, but in this case there ought ito be at least two months for the wall to scason and set before filling. The upper portion of the silo wall need not be heavier than 18 inches, and if the size of stone permit of it, the outer face of the wall may be drawn in gradually to a thickness of 12 inches at the top. Too great care cannot be taken in making the part of the wall below and near tthe ground solid, and especially its outer face, so that it will be strong where the greatest strain B98 will come. It is best also to dig the pit for the silo large enough so as to have plenty of room outside of the finished wall to permit the earth ee filled in behind to be very TSS thoroughly tamped, so as es to act as a strong backing Pa for the wall. This is si urged because a large per cent. of the stone founda- tions of wood silos have cracked more or less from one cause or another and these eracks lead to the spoiling of silage. GSB8aSe asec @absSsl SES "Sase a ws e : : a si Flat quarry rock, lke Bo ; : = is Hs limestone, will make the strongest silo wall, be- ‘vause they bond much better than boulders do, , and when built of lime- , stone they will not need to be reinforced much with iron rods. It will be Fic. 197—Shows the method of jacketing a best even in this ease stone silo to protect it against frost: the . 2 heavy black squares are bloeks bedded into however, to use the lron the stone wall to which girts or studs may... be nailed to carry the siding. tie rods between the lower two doors. 495. Plastering. The inner face of the silo wall should be plastered with a thin eoat of rich cement not leaner than 1 of cement to 144 or 2 of clean sharp sand. If the mortar is not rich and troweled smooth, the acids of the silage will act upon it much more rapidly, dissolving out the lime and leaving it open and porous. It will usually be prudent also ito whitewash these linings every two or three years, especially the lower portion where the silage is longest in contaet with the cement, in order to prevent softening, using cement to make the whitewash. 496. Doors.—Doors for filling and feeding should be ar- ranged as represented in A, Fig. 196, and it the lower one 1s long, cutting out a good deal of the wall, an iron rod should be bedded in the wall above it to prevent cracking between the doors. The rod should be of 2 inch round iron bent to the curve of the circle and about 12 feet long. The two ends should be turned short at right angles, so as to anchor better in the mortar. In deep stone silos, which rise more than 18 feet above the surtace of the ground, it will be safest to strengthen the wall between the two lower doors with iron tie rods and, if such a silo is built of boulders, it will be well to use rods enough to make a complete line or hoop around the silo about two feet above the ground, as represented in Fig. LoS: Fie. 198.—Showing method of bedding iron rods in stone, brick o Se erete silo walls to increase the strength. lhe heavy lines with en bent represent the iron rods. The door jainbs for the stone silo are best mi ade of 4x4’s framed together and set far enough apart to give a depth four awalieg less than the thickness of the wall. This will allow mortar to be filled in between the 4x4’s to make an 400 air-tight joint. A 6-ineh board may be fitted around the outside of the inner side of the door jambs to form the rab- bet for the doors, or the jambs may be made as represented in Fig. 196. There will be slight shoulders left in the round stone silo above and below the doors when these are made flat, and these should be filled out with mortar when plastering, giving a long, gentle slope back to the wall. The door is best made of two layers of 6-inch flooring, tongued and grooved, crossing at right angles, nailed or screwed together, with a layer of good acid- and water- proof paper between, as shown at EK, Fig. 196. To make the door fit perfectly air-tight there should be tacked to the face of the door jamb, all around, a wide strip of thick roof paper or strips of old worn out rubber belting, and the door drawn up against this with four 4x4 inch lag bolts pro- vided with washers. If one prefers to do so the door may be made small enough so as to leave a half-inch space between it and the jamb all around, and this space filled with puddled clay after the deor is put in place. Either of these methods is better than to tack strips of tar paper over the joints. CONSTRUCTION OF BRICK SILOS. Very excellent silos may be made of brick, as repre- sented in Fig. 199, and where brick of a good quality ean be obtained at $4.25 to $7.00 per thousand a silo which will last indefinitely may be made at a moderate cost. 497. Foundation.—The foundation of the brick silo is best made of stone, wherever these may be had, carrying the stone work up at least a foot above the ground and be- ginning below frost line. The brick work will then be set with its inner face flush with the inner surface of the stone work. If the silo is to be earried 20 or more feet above the stone wall it will be desirable to bed a 23-inch round iron hoop 401 into the upper surface of the stone work in order to guard against cracking the wall by the pressure of the first filling before the mortar has had time to thoroughly season, which Fic. 199-—Shows an all-brick silo with wail 14 inches thick made of three courses of brick, the outer course being set so as to form a 2-ineh dead air space as high up as the shoulder. does not take place until after five or more months. The method of laying the sections of iron red in the wail is rep- resented in Fig. 198. 402 498. Walls.—In cold climates it will be best to make the lower portion of the wall, up to within 10 feet of the top, with a 2-inch dead air space, using three courses of brick, thus making the wall 14 inches thick, for all the smaller and medium sized silos. If the silo is to exeeed 24 feet inside diameter the lower third of the brick wall should be made of four courses of brick and 18 inches thick, the second third 14 inches thick, and the upper third 8 inches, solid. The dead air space should be next to the outside and this course of brick should be tied to the inner wall as frequently as necessary to make it stable. 499. Strengthening the Walls.——The tendency of the pressure of the silage to crack the walls of round silos in- creases with the depth and with the diameter of the silo. The tendency of the silage to burst a silo 26 feet inside diameter is twice as great as in one 13 feet in diameter and the same depth, and this makes it necessary to strengthen the walls of the larger brick silos. In all brick silos there should be an iron tie rod bedded in the wall, in the manner illustrated in Fig. 198, between each of the lower doors to compensate for the weakening caused by the doors; and in the larger silos these ties should extend entirely around the silo in the manner shown in Fig. 198. 500. Wetting Brick.—It is very important in laying the brick for a silo wall that they should be wet and especially if the work is done in hot, dry weather. If this is not done the brick will so completely dry out the mortar that 1t can- not set properly and become strong. 501. Making Walls Air Tight.—There are several ways in which this may be done, and some of these will be given in the reverse order of their effectiveness. 1. After the wall is finished it may be simply given ‘two coats of thick cement whitewash, and this repeated every two or three years as ithe acid of the silage dissolves it away. 2. The face of the brick wall may be given a good, rich 403 eoat of cement plaster, one-fourth to one-half an inch thick, and then this be kept whitewashed so as te neutralize the acid and prevent it from softening the cement. 3. The wall, or at least the inner portion, may be laid in rich cement mortar, making the horizontal joits about one- fourth of an ineh thiek and the vertical ones a half inch thick, taking great care to get all jomts of the inner tier of brick thoroughly filled with mortar. This method wiil place the cement where it will not be as readily affected by the acids and frost and does away with the necessity of plastering, care being taken to lay the brick smoothly and to poimt the joints carefully. Milwaukee cement will answer for this work. Whitewashing the inner face of such a lining will be sufficient for smoothness and tightness. 4. The very best possible lining which could be made would be secured by using the small, thin size of vitrified paving brick. These may be set on edge, to reduce both the cost and the number of cement joints. It will be nee- essary to tie this course occasionally to the main wall by turning a brick endwise. Rieh cement mortar should be used and the joints made thin but thoroughly filled with the mortar. Such a lining would give a surface like a stone jug, thoroughly air-tight and indefinitely permanent. 502. Doors.—The jambs may best be made of 3x6’s or 3x8’s rabbetted two inches deep to receive the door on the inside. The center of the jambs outside should be grooved and a tongue inserted projecting three-fourths of an inch outward to set back into the mortar and thus secure a thor- oughly air-tight joint between the wall and jamb. The doors are best made as described under the stone silo, of two layers of matched flooring with paper between. CONSTRUCTION OF BRICK-LINED SILOS. Next to the all-masonry silos in point of durability and efficiency must be ranked the masonry lined silos, of which 404 there are several types,as follows: (1) Stone silos, jacketed with wood; (2) concrete lined silos; (3) brick lined silos; (4) lathed and plastered silos. Fre. 200.—Showing a brick lined round silo with bricks set on edge and plastered with cement. Dots A, A show where an iron rod may be bedded in the wall to prevent spreading. Of these types the brick lined silo is likely to come into the more general use, and its construction will be deseribed first. 405 503. Foundation and Sill.—Like the brick silo, this form should have a stone foundation, wherever it is practicable to obtain the material for it. Upon this should first be laid the sill made of 2x4’s cut in two-foot lengths with the ends beveled so that they may be toe-nailed together and bedded in cement mortar upon the wall in the manner represented in Fig. 201. The sill is set just far enough back from the inside of the wall so that when the brick are laid they come flush with the inside of the silo wall. hic. 201.—Showing method of making the sill of brick lined and of round wood silos. BK, plan of studdiug for all-wood, brick lined or lathed and plastered slio. 504. Setting Studding.—The 2x4 studding are next set up and toe-nailed to the sill. A stud is first set at each angle of the sill, plumbed and stayed from a post set in the center of the silo. After four or five of these are set and plumbed from the center they should be stayed from side to side by tacking to them a strip of half-inch sheeting bent around the outside as high up as a man can reach, taking care to get each stud plumb in this direction before staying. After the alternate studs have been set up in this manner the intervening ones may be put in place, toe-nailed to the sill and stayed to the rib holding the others in place. 505. Sheeting. The next step should be to put on the outside laver of sheeting which, for all of the silos less than 25 406 30 feet in diameter, should be three-eighths inch lumber made by buying a good quality of fencing and taking it to the mill to have it sawed in two. The usual price for sawing fencing in two in this way is $1.00 per thousand. The reason. for getting fencing and having it sawed in this manner is to save expense. It is the custom of dealers to charge the same price for half inch as for ich lumber, and hence buying good fencing and haying it sawed reduces the cost just one-half, less the cost of sawing. The studding should be covered inside and out with this sheeting, nailing thoroughly with S-penny nails, two nails in each board at every stud. The object of the boards is to act as hoops and give the silo the needed strength. 506. Siding.— If the silo is out of doors it will need to be covered with house siding with the thick edge rabbetted, o1 else veneered with a single course of brick. Several silos have been sided with halfaneh lumber with both edges beveled at an angle of 45 degrees to take the place of the rabbet. This method gives greater strength, but is not likely to keep out rain as thoroughly. 507. Lining.—The brick lining of the silo should be laid in rich Milwaukee, Akron or Louisville cement mortar, the bricks being previously wet. The most mgid lning will be secured by laving the brick flatwise, making the layer 4 inches thick, but with one-half the amount of brick they may be set on edge, thus considerably lessening the cost. If set on edge, as represented in Fig. 200, a row of spikes should be driven into the studding through the joints ot every fourth course to hold the brick more securely in place until the cement has had time to season, The mortar should not be made more than one-fourth of an inch thick and great care should be taken to leave no open space anywhere. The necessity of plastering the wall may be avoided by filling behind each brick with one-half an inch of mortar, which will keep out the air as well as if on the front side and there will be the additional advantage 407 of the cement not coming in direct contact with the silage juices. If care is taken in setting the brick so as to secure a smooth face, pointing the joints carefully, it will not be nee- essary to even whitewash the wall and a permanent lining requiring no attention will thus be secured. In this form of silo the brick may have one face filled with coal tar, or the vitrified paving brick may be used, giving a lining wholly air tight and permanent. ROUND PLASTERED SILO. Where brick ave high, lumber low, and clean, sharp sand may be readily obtained, a cement plastered lining may be made to take the place of the brick lining, using the Mil- waukee, Akron, Rosendale or Louisville cement in making the mortar. The first coat is usually made with hair and a little hme to make it hang to the wall better. There are a good many of these lathed and plastered cylindrical silos in Racine and Kenosha counties in this state, and across the line in Illinois. Some of these have been in use since 1889 and have given good satisfaction. 508. Construction.—The frame work of the silo should be made exactly like that of the silo with brick lining: ex- cept that there should be two layers of half-inch sheeting on the inside with a layer of 3-ply Giant P. and B. paper between, or other of as good quality. After the woodwork of the silo has been completed it should be lathed and plastered with a cement mortar made of 1 of cement to 2-of sand. If wood lath are used there should be furring strips of lath nailed to each stud up and down and the lath nailed through these. If metal lath is used this may be nailed direetly to furring strips of lath nailed to the studding over the liming and the plastering then done. It should be understood that it would not do to lath and plaster a rectangular wood silo because the springing of the 408 walls would crack the cement. It should be understood further that on account of the fact that the layer of cement is so thin it is a matter of greater importance to keep the Fie. 202.—Sbowing an all-wood round siio on stone foundation. H rep- resents a method of sawing boards for the conical roof. surface whitewashed to prevent the acid from softening the cement and rendering it porous. It is because of this also that two layers of lming with paper between are recom- mended. 409 CONSTRUCTION OF ALL WOOD SILOS. Up to the present ‘time more silos have been built of wood than of any other material, and since 1891, the majority of wood silos built have been after the model represented in Fig. 202. Very few silos of the rectangular type are now built unless they be of stone. 509. Foundation.— There should be a good, substantial masonry foundation for all forms of wood silos and the woodwork should everywhere be at least 12 inches above the earth to prevent decay from dampness. There are few conditions where it will not be desirable to have the bottom of the silo 3 feet or more below the feeding floor of the stable and this will require not less than 4 to 6 feet of stone, brick, or conerete wall. For a silo 30 feet deep the founda- tion wall of stone should be 1.5 to 2 feet thick. fivefeer Fic. 203.—Showing two methods of placing the wood, brick lined or lathed and plastered silo on a stone foundation. A shows the silo set with upper portion flush with the inside of the stone wall, and B shows the upper portion flush with the outside of the stone wall. The inside of the foundation wall may be made flush with the woodwork above, as represented in Fig. 203 A, or 410 the building may stand in the ordinary way, flush with the outside of the stone wall, as represented in Fig. 203 B. In both cases the wall should be finished sloping as shown in the drawings. 510. Cementing the Bottom.— After the silo has been completed the ground forming the bottom should be thor- oughly tamped so as to be solid and then covered with two or three inches of good conerete made of 1 of cemenit to 38 or 4 of sand and gravel. The amount of silage which will spoil on a hard clay floor will not be large, but enough to pay a good interest on the money invested in the cement floor, Lf the bottom of the silo is in dry sand or gravel the cement bottom is imperative to shit out the soil air. 511. Tying Top of Wall.—In case the wood portion of the silo rises 24 or more feet above the stone work and the diameter is more than 18 feet rt will be prudent to stay the top of the wall in some way. If the woodwork rises from the outer edge of the wall, then building the wall up with cement so as to cover the sill and lining as represented in Fig. 207 will give the needed strength, because the wood-work will act as a hoop; but if the silo stands at the inner face of the wall, it will be best to lay pieces of iron rod in the wall near the top to act as a hoop. Where the stone portion of the silo is igh enough to need a door it is best to leave enough wall between the top and the sill to allow a tie red of iron to be bedded in this portion. So, too, the lower door in the woodwork of the silo should leave a full foot in width below it of lining and siding uneut to aet as a hoop, where the pressure is strongest. 512. Sills and Studding.— The sill in the all-wood silo may be made of a single 2x4, eut in 2-foot lengths, in the manner represented in Fig. 201 and deseribed under the brick lined silo. r 411 The studding of the all-ewood round silo need not be largerthan 2x4 unless the diameter is to exceed 30 feet, but the to »y should be set as close together as one foot from center center, as represented in Fig, 201, B. This number of studs is not required for strength but they are needed in order to bring the two layers of lining very close together SO as to press the paper closely and prevent air from enter- ing where the paper laps. & N LLIN LLL LP VL LV V ZEAL A a ‘J Ne YAN WS SQ hic. 24.—Showing the construction of the door for the all-wood silo. in G is a cross-section of the door resting against the door jamb, which is provided with a gasket of three-ply ruberoid roofing and held in place with four lag bolts and washers, the door opening on the inside, F is a front view of the door made of two layers of four jnebh or six inch tongued and grooved flooring with a Jayer of three- ply acid and water proof J. & Ve. paper between. To stay the studding a post should be set in the ground the center of the silo long enough to reach about 5 feet above the sill and to this stays may be nailed to hold in place the alternate studs until the lower 5 feet of outside £12 sheeting has been put on. The studs should be set first at the angles formed in the sill and earefully stayed and plumbed on the side toward the center. When a number of these have been set they should be tied together by bending a strip of half-inch sheeting around the outside as high up as aman ean reach, taking care to plumb each stud on. the side before nailing. When the alternate studs have been set in this way the balance may be placed and toe- nailed to the sill and stayed to ithe rib, first plumbing them. sideways and toward the center, On the side of the silo where the doors are to be placed the studding should be set double and the distance apart to give the desired width. A stud should be set. between the two door studs as though no door were to be there and the doors cut out at the places desired afterwards. The con- struction of the door is represented in Fig, 204. 513. Sheeting and Siding.—'The character of the siding and sheeting will vary considerably according to conditions and size of the silo. Where the diameter of the silo is less than 18 feet mside and not mueh attention need be paid to frost, a single layer of beveled siding, rabbetted on the inside of the thick edge deep enough to receive the thin edge of the board below, will be all that is absolutely necessary on the outside for streneth and protection against weather, This statement is made on the supposition that the lining is made of two layers of fencing split in two, the three layers constituting the hoops. If the silo is larger than 18 feet inside diameter, there should be a layer of half-inch sheeting outside, under the siding’. If basswood is used for siding care should be taken to paint it at once, otherwise it will warp badly if it gets wet before painting. In applying the sheeting begin at the bottom, carrying the work upward until staging is needed, following this at onee with the siding. Two 8-penny nails should be used 413 in each board in every stud, and to prevent the walls from getting “out of round” the succeeding courses of boards should begin on the next stud, thus making the ends of the boards break joints. to When the stagines are put up new stays should be taeked eine | A the studs above, taking care to plumb each one from side to side; the siding itself will bring them into place and keep them plumb the other way if care is taken to start new courses as deseribed above. 514. Forming the Plate.-—Whien the last staging is up the plate should be formed by spiking 2x4’s, cut in two-foot lengths, in the manner of the sill, and as represented in. Fig. 205, down upon the tops of the studs, using two courses, making the second break joints with the first. BiG. 205.—Showing construction of conical roof of round silo where rafters are not used, The outer cirtle is the lower edge of the roof, the second circle is the plate, the third and fourth circles are hoops to which the roof boards are nailed. The view is a plan looking up from the under side. 515. Lining for Wood Silos.—There are several ways of making a good lining for the all wood round silo, but whichever method is adopted it must be kept in mind that 414 there are two very important ends to be secured with cer- tainty. These are (1) a lining which shall be and remain strictly air tight, (2) a lining which will be reasonably permanent. Galvanized Iron in Silo Lining.—The tightest ning for a wood silo may be made with a hght weight of galvanized iron, No. 28 to No. 32. Where the silos are 18 feet in diameter or less this may be put directly upon the studding, buying the strips $ feet long and 36 inches wide, so as to be nailed on up and down and exactly cover the space be- tween three or four studs. Headers should be put im every 8 feet to nail the ends of the sheets to between the studs, and these are best when sawed to the curve of the silo. The metal should be put on with roofing nails, nailing close so as to make the joints tight. After the metal is in place it should be given a heavy coat of asphalt paint, taking special care to make it heavy where the nails and laps come so as to shut out the air. When the metal is in place and painted it should be covered with a layer of sheeting made the same as that used outside, by splitting good fencing in two. The object of this laver of sheeting is, first to take the pressure of the silage; second, to act as a hoop for strength, and third, to keep the silage from softening and wiping the paint from the metal hning. Were it not for the fact that the heat of the silage tends to soften the paint, and its settling to wipe it off, it would be better to let the metal come next to the silage. Where the silo is more than 18 feet in diameter it will be best to use two layers of fencing split in two, placing the galvanized iron between the two layers. In these cases the sheets of metal may be put on horizontally, using those 36 inches wide. All Wood Lining of 4-inch Flooring—If one is willing to permit a loss of 10 to 12 per cent. of the silage by heat- ing, then a lining of tongued and grooved ordinary 4-inch white pine flooring may be made in the manner repre- sented in Fig. 206, where the flooring runs up and down. 415 When this lumber is put on in the seasoned condition a single layer would make tighter walls than can be secured with the stave silo where the staves are neither beveled nor tongued and grooved. In the silos smaller than 18 feet in- side diameter the two layers of boards outside will give the needed strength, but when the silo is larger than this and deep there would be needed a layer of the split fencing on the inside for strength; and if in addition to this there is added a layer of 5-ply Giant P. and B. paper, a lining of very su- perior quality would be thus secured. Lining of Half-inch Boards and Paper.—Where paper is used to make the joints between boards air tight, as represented in Fig. 207, it is ex- tremely important that a quality which will not decay and which is both acid and water-proof be used. A paper which is not acid and water- proof will disintegrate at the joints in a very short time and thus leave the hning very defective. Great care should be taken to have the two layers of boards break joints at their centers, and the paper should lap not less than 8 to 12 inches. The great danger with this type of lining will be that the boards may not press the two layers of paper together close enough so but that some air may rise between the two sheets where they Fic. 206.— Showing the construc‘ ion of the all-wood silo where the lining is made of ordinary four inch floor- ing running up and down, and nailed to girts cut in between the studding every four feet. overlap and thus gain access to the silage. It would be an excellent precaution to tack down the edges of the paper 416 closely with small carpet tacks where they overlap, and if this is done a lap of 2 inches will be sufficient. WZZZAA LAA EES EE EES SS ONE FOOT Wra. W7.—D, Showing method of constructing the all-ewood round silo and connecting it with the wall flush with the outside. This figure shows the most substantial form of construction with three layers of half-inch lumber and two layers of three-ply acid and water proof BP. & B. paper between them. A very excellent silo is made after this plan omitting the inner Inyer of lining and paper and the layer of paper on the outside. With small silos 15 feet in diam- eter only the siding on the outside is necessary for strength and protection against weather, fh, Showing method of construction for ventilating the spaces between the studding in all-wood and lathed and plastered silos. The jower portion shows the intakes of fresh air frou: the outside at the bottom, and the upper portion shows where the air enters the silo at the plate to pass out at the ventilator in the voof. Such a lining as this will be very durable because the paper will keep all the hunber dry except the inner layer of half-inch boards, and this will be kept wet by the paper and silage until empty and then the small thickness of wood will dry too quickly to permit rotting to set im. A still more substantial lining of the same type may be secured by using two layers of paper between three layers of boards, as represented in Fig. 207, and if the climate is 417 not extremely severe, or if the silo is only to be fed from in the summer, it would be better to do away with the layer of sheeting and paper outside, putting it on the inside, thus securing two layers of paper and three layers of boards for the lining with the equivalent of only 2 inches of lumber. 516. Construction of Roof.— The roof of cylindrical silos may be made in several ways, but the simplest type of con- struction and the one vequiring the least amount of mater- ial is the cone, represented in Figs. 202 and 205, If the silo is not larger than 15 feet inside diameter no rafters need be used, and only a single circle, like that in the center of Fig. 207, D. This is made of 2- inch stuff cut in section in the form of a circle and two layers spiked to- gether, breaking joints. ery silo which has a roof should be provided with aie ventilation to keep the underside of the roof dry and in the ease of wood silos, to prevent the walls and lining from rotting. One of the most serious mistakes in the early construction of wood silos was the making of the walls with dead-air spaces which, on account of the dampness from the silage, lead to rapid “dry rot” of the lining. In the wood silo and in the brick lined silo it is important to provide ample ventilation for the spaces between the studs, as well as for the roof and the inside of the silo, and a good method of doing this is represented in Fig. 207, E, eae the lower portion represents the sill and the upper the plate of the silo. Between each pair of studs, where needed, a one and one-fourth inch auger hole to admit air is bored through the siding and sheeting and covered with a piece of wire netting to keep out mice and rats. At the top of the silo on the inside the lining is only covered to within two inches of the plate and this space is covered with wire netting to prevent silage from being thrown over when filling. This arrangement permits dry air from outside to enter at the bottom between each pair of studs and to pass 418 up and into the silo, thus keeping the lining and studding dry and at the same time drying the under side of the root and the inside of ithe lining as fast as exposed. — In. those ‘ases Where the sill is made of 2x4’s eut in 2-foot lengths there will be space enough left between the curved edge of the siding and sheeting and the sill for air to enter, so that no holes need be bored as. described above and repre- sented in Fig. 207 E. The openings at the plate should al- ways be provided and the silo should have some sort of ven- tilator in the roof. This ventilator may take the form of a cupola to serve for an ornament as well, or it may be a simple galvanized iron pipe 12 to 24 inches in diameter, rising a foot or two through the peak of the roof. 518. Painting Silo Lining.—It is impossible to so paint a wood lining that it will not become wholly or partly satur- ated with the silage juices. This being true, when the lining is again exposed when feeding the silage out, the paint greatly retards the drying of the wood work and the result is decay sets in, favored by the prolonged dampness. For this reason it is best to leave a wood lining naked or to use some antiseptic which does not form a water proof coat. THE STAVE OR TANK SILO. We have examined personally the past season 19 stave silos and have made a careful study of the unavoidable losses in one of these. We have also studied the unavoid- able losses in two kinds of small stave silos. As a result of these observations it has been demonstrated that there are several very serious objections to stave silos intended as per- manent buildings out of doors. Some of these are stated below: 1. When the silo is empty the staves shrink and loosen the hoops and in this condition the wind racks the building, getting it out of round, out of plumb, and out of place upon the foundation. It is mueh more easily blown down than 419 other forms of silos. Two of the fourteen owt-of-door silos visited had been blown down; one of these was abandoned and the hoops sold to another farmer; the other was set up again at ‘the expense of a day’s drive for new staves and get- ting the carpenters to set it up, the accident happening just as they were ready to fill the silo last fall. A third silo of the fourteen out-of-doors we visited had moved on the foundation so much that I could put my arm up through between the stone wall and the outside ot the staves. This silo had been staved to the end of the barn, using fence wire for guy rods. Three others of the fourteen out-of-door stave silos had been found so unsatisfactory that they were subsequently lined on the inside to prevent the silage from spoiling, and in two of these three the inner lining has rotted out on ac- count of the dampness which the outside staves confines. 2. There is great danger of the hoops being broken by the tense pressure of the silage increased by the swelling of the staves. In one of the silos visited eight out of ten hoops ou one side of the silo and six out of ten on the oppo- site side had sheared in two the 2x4’s used tor Ings; but, by a fortunate coincidence, ‘two of the ten hoops remained intact to hold the silo up, assisted by some half-inch boards which had been bent around the inside of the silo at the top to prevent the staves from falling in. In another silo where 4x4 oak pieces had been used as lugs, the 2-ineh iron washers had been erushed their full depth of one-half inch into the hard wood and two of the pieces of wood had been badly injured by the severe strain upon them. In a fourth silo where the hoops were provided with iron Ings the staves on one side had been thrown into the silo by the swelling of the wood. It is urged by the advocates of these silos that with a little care and judgment the nuts of the hoops may be tightened or loosened as needed and such accidents averted. There is enough truth in this statement to induee many farmers with limited means to take the risk, but life is too short and there are too many other things to engross the at- tention of good farmers for them to le awake nights won- dering whether the silo hoops are too tight or to loose, 3. Staves do not contain the same amount of sapwood im all parts and for this reason shrink unequally, with the re- sult that after 3 or 4 years’ use there are places which do not close up tightly on swelling and which open again on the sunny side of the silo, and thus adinit air, even where the silage is in contact with them. Three of the silos visited showed these peculiarities, and in one of them visited last winter we could see through be- tween several staves on the south side of the silo close to the silage surface, on the inside. 4. The expansion and contraction of the staves during wetting by the silage and drying when the silo is empty makes it difficult to securely anchor a permanent roof and impossible to connect the staves permanently with the foun- dation, so as to be air-tight. Something must be done each season to cement the joints between the staves and foun- dation or air will enter. 5. There is no reason to hope that good silage with small losses in dry matter can be made in ithe stave silos which are not carefully constructed of good lumber with the staves both beveled, and tongued and grooved. It is reall more difficult to make a stave silo air tight than it is to make a tank water-tight, and we have found by careful tests-that the unavoidable losses in a new stave silo next. to the walls were as high as 24 to 28 per cent. 519. Construction of Stave Silos.— There are three meth- ods adopted in the construction of these silos. The best and only one which should be used in the permanent silo is that represented in Fig. 208, where the staves are both beveled and tongued-and-grooved; the second is where the staves are beveled so that the Hat surfaces fit together ac- curately as water tanks are made; the third plan uses the lumber without either beveling or tonguing-and-grooving, and this both observation and principles of construetion in- 421 dieate should be adopted with very great hesitation and as a temporary makeshift only until more experience and ex- act knowledge has been obtained regarding their perma- nent efficiency. AA MILILAOTELALLTE EEE. =WWiWwnnit Fie. 208.—Showing the construction of the stave silo. A shows the silo complete on stone foundation with four feeding doors. B is cross- section of four staves showing how they are tongued and grooved to make them air tight. C shows a method of splicing staves. D shows iron lugs for tightening hoops. F is front view of door viewed from outside. G cross-section of same. E is a vertical section show- ing the shoulder against which the door rests, and upon which should be a gasket of three-ply ruberoid roofing. The door should also be ean ene against it with four lag bolts and washers, opening from the inside. This third plan has been recommended because the first cost is relatively low and because it is assumed that the pres- 26 422 sure due to the swelling of the wood and the rigidity of the hoops will result in crushing the edges of the staves to- gether so as to make a sutticiently tight joint to preserve the silage. 520. Lumber for Staves.—The lumber selected for the staves of this type of silo should be of the grade known com- mercially as “tank stuff,’ and lumber freest from knots and stiaightest graimed is best. Wood is quite air-tight under low pressures in directions across the grain but along the grain the air passes more or less freely. The Washing- ton cedar appears to be an excellent wood for this purpose, as it shrinks much less than the pine after the silage is re- moved and, for this reason, the building will be much more stable when empty and less liable to burst the hoops when filled. Where the silo is to be deeper than can readily be secured with single lengths of lumber the staves may be spliced in the manner represented at C, Fig. 208, where a saw-cut 1s made in the ends of the two staves and a piece of galvanized iron, a little wider than the stave is sipped into it. This crushes into the wood on the sides and forms a water tight joint. 521. Foundation of Stave Silo.—On account of the ten- deney of the stave silo to work off from the wall when elpty a flat cement floor has been recommended, made ot sand and gravel or crushed rock, forming a bed of concrete abowt 12 inches thick. = This is perhaps as good as can be done under the cireumstances but it precludes the exten- sion of the silo into the ground. If the silo stands upon a stone wall, as represented in Fig. 208, it will be prudent to have a shoulder jutting into the silo as much as 2 inches and a similar amount on the out- side, to permit of some movement on the foundation. 522. Hoops for Stave Silo.—Five-eighths inch round iron rods, in about 16-foot lengths, form the best hoops and they 425 should be provided with long threads and joined with iron lugs and nuts, as represented in D, Fig. 208. The iron lugs should always be used in preference to the 2x4’s or 4x4’s because they are better in every way. So, too, should they be used in preference to posts set up against the silo outside or shaped to act asa part of the staves as has been recom mended. In visiting over 100 silos in 1891 it was found that wherever a silo lining had a heavy timber back of it, the holding of dampness caused rotting there in three or four years, and it is quite certain that the use of iron lugs is the safest way to avoid this danger in stave silos. 523. Doors for Stave Silos.— A good method of construct- ing doors for the stave silo is represented in Fig. 208. Two inch lumber is bolted to the staves on the outside, pro- jecting two inches into the doorway all around, thus form- ing a rabbet against which the door may rest. A strip of thick ruberoid roofing should be used on the rabbet under the door and the door drawn down tight with four lag bolts and washers. A common way of making these doors is to cut. the staves out on a bevel and make the door fit into this beveled cut directly. If the work is carefully done and then, at the time of filling, if the face of the bevel is plastered with a thick coat of puddled clay and the door forced tightly into this a fairly close joint nay be secured, 524. Pit Silos.—In localities where both lumber and masonry are expensive or cannot be had, and where the soil is of such a character that a pit 15 to 20 feet deep may be sunk in the ground, a good silo may be made in this way. The most serious objection to such a silo is the ineon- venience of removing the silage to feed. If the soil is of such a character that it will not cave in the pit may be made circular in form, of the desired size and depth and then plastered with cement in the manner of a cistern. If there is a little difficulty in the walls stand- 424 ing the pit may be made with sloping sides, smallest at the bottom. In using such a silo, especially when filling it, care should be observed in going into it when there is a possibility that ‘carbonic acid has accumulated to a dangerous extent. There need be no danger in using such a silo if caution is observed as stated on page 427. 525. Weight of Silage per Cubic Foot.—The weight of corn silage increases with the depth below the surface, with the amount of water in the silage, and with the diameter of the silo. In silos of small diameters the amount of surface in the wall is so much greater in proportion to the silage contained that the friction on the sides has more influence in preventing the settling of the silage. In the following table will be found the weights of silage per cubic foot in round silos given for different depths and the mean weight of silage above the given depth: Table showing the computed weight of well matured corn sil- age at different distances below the surface, and the com- puted mean weight for silos of different depths, two days after filling. Went Mean Weight |. Mean Weight | Mean Depth Reerit weight} Depth /of silage|weight of| Depth |of silage| weight of of Otor. of sil- | _ of at silage of at silage silage. ent |a28e per silage. ‘different |percubic| silage. |different | per cu. . | cu. ft. depths. foot. depths. foot. depths. Feet. | Lbs. Lbs. Feet. Lbs. Lbs. Feet. Lbs. Lbs. 1 18.7 18.7 18 373 28.3 25 51.7 36.5 2 20 4 19.6 14 38.7 29.1 26 52.7 37.2 3 22.1 20.6 15 40.0 29.8 27 53.6 37.e 4 rab yatt 21.2 16 413 30.5 28 54.6 38.4 5 25.4 22.1 17 42.6 31.2 29 55.5 39.0 6 27.6 22.9 18 43.8 319 a 56.4 39.6 7 28.5 23.8 1y 45.0 32.6 31 57.2 40.1 8 | 30.1 24.5 20 46.2 33 3 32 48 0 40.7 9 31.6 25.3 2t 47.4 33.9 33 58.8 41.2 10 33.1 26.1 22 48.5 34.6 34 59 6 41.8 11 34.5 26.8 23 49.6 35.3 35 60.3 42.3 12 35.9 27.6 24 50.6 35.9 36 61.0 42.8 526. Capacity of Silos—The amount of silage which may be stored in a silo increases in a higher ratio than the depth 425 increases. < 100 -= 3,885 < W. D. 6, 4000 whence W. D. = 3.8858 == 16547 or about a 16.5 per cent. grade. That is, a grade of 16.5 feet in 100 feet is the steepest dirt road a team can be ex~ 435 pected to carry the load over which it was able to bring over a level dirt road to it. These results have been computed from the standpoint of an 800-pound horse, but since the ability of a team to work is in a general way proportional to its weight the same results would have obtained had we taken the 1,600- pound horse with a proportional load. 533. Good Roads Make High Grades More Objectionable.— When the good macadam road bed is substituted for the common dirt road then the same draft, 140 pounds, which draws a ton on the dirt road will draw 140 60 — 21 times as much or 4, 6662 lbs. = 2! tons. on the level macadam road. Since it requires but 60 Ibs. to move a ton on a macadam road it will require 60 < 21 — 140 lbs. to draw the 2% tons on the level road, hence the effective power of the team will be 400 — 140 = 260 lbs. Up how steep a grade will 260. lbs. carry the team and 214 tons? Solving this as we did the other we get 260 < 100 = 6, 2662 < W. D. 26,000 whence W. D. = 6, 2662 = 4.149 or a little more than a 4 per cent. grade. That is to say, when a dirt road is improved so as to reduce the draft from 140 lbs. per ton to 60 lbs. per ton then, in order to utilize this improved road with equal effectiveness under the con- ditions assumed, the 6.2 per cent. grade should be reduced to 4 per cent.; and the highest grade could not exceed 10.53 per cent. 45 DRAFT OF WAGONS ON THE LEVEL. There are many factors which modify the draft of a wagon over a level road and some of the most important of these are: 1. Smoothness of the road-bed. 2. Rigidity of the road-bed. 3. Width of the tire. 4. Diameter of the wheel. 5. Distribution of the load on the carriage. 6. Direction of the line of draft. 7. Rigidity of the carriage. 534. The Smoothness of the Road-bed.—When the road- bed is not smooth and has numerous ruts, stones or other obstructions upon its surface, the draft of the load is im- creased and the wear on the vehicle and on the road-bed is also greater so that much effort and care should be ex- ercised to have the road smooth. The increase .in the mean draft of the load is not so great, however, as the other dithiculties which result for the reason that when the wheel enters a rut or passes down off from an obstruction there is a push forward which tends always to give back a portion of the energy expended in raising the load upon the ob- struction or out of the rut. 535. Rigidity of the Road-bed.—.\ yielding road-bed is perhaps the most serious defect of roads, and the one whieh increases the draft more than any other. If a wheel is steadily cutting into its road-bed it is continually tending to rise over an obstruction or out of a rut, or it is doing what is in effect all the time passing up a grade, as repre- sented in Fig. 210, the hill being steeper in proportion as the wheels are smaller. Tn Fig. 209 is represented a method of measuring the in- crease in draft due to the wheel rising over an obstruction whose hight is a stated per cent. of the radius of the wheel. 435 The arrangement at C is provided with a screw and gradu- ated so that the block may be raised or lowered at will, setting it so as to represent the wheel passing over an. ob- struction, 3, 4, 5, ete., per cent. of the radius of the wheel. 3y setting the road-bed inclined as shown in the figure, the if aft 1s first noted and then the thumb screw at D is turned until the wheel rises upon the block and the difference be- tween the two readings of the scale expresses the increased draft due to the obstruction. When the obstruction is only four per cent. of the radius of the wheel the draft is increased more than two-fold. That is to say, if a wheel is 48 inches in diameter, an ob- struction of four per cent. would be only .96 of an inch, and yet the draft is made by it more than: twice as heav y: When the wheel cuts in one ineh the draft would not in- crease quite so much because the wheel never rises quite out of the rut, but the difference between the draft on the macadam, and dirt road is due mostly to the difference in the yielding, or cutting in of the wheels. An experiment conducted by the United States Depart- ment of Agriculture, testing the draft of ordinary wagons on a steel wagon road, showed that a single small horse 456 easily drew 11 tons, or 22 times the weight of the animal, and it is stated in the report that the horse could readily have hauled 50 times his own weight. ‘This would be, for a 1,000-pound horse, 25 tons, but of course with sueh a load the road must be practically level, for a grade of one per cent. would increase its draft 500 pounds. 536. Draft of Wagon Shown by English Trials.—'The power required to draw a four-wheeled wagon over roads of different characters has been tested and the following expresses the results in pounds per 2,000 lbs, of gross load : On cubical block pavement ............ 28 to 44 Ibs. per ton Onimacnd amend vera cuiesateeants at 55 to G67 lbs, per ton Onveviavel oad ci aanniet avec cmioal ate tat vals 75 to 140 Ibs, per ton COMPLE eMO Aen nist riaaalaateate nate are ... 20to 44 Ibs. per ton Onicommonicint vOAte cnet aaa 75 to 224 Ibs, per ton 537. Draft With Different Widths of Tire.—Prof. J. H. Waters’ has made an extended series of trials to test the effect of the width of tires on the draft of loads under dif- ferent conditions of road. [le used always a net load of one ton, but the 6-inch tired wagon was 245 pounds heavier than the 1.5 inch, making the gross loads 8,225 and 2,080 pounds respectively, when the wagons were free from mud, The following are his results: On macadam streets, wide tire 26 per cent. less than narrow tire. On gravel road, wide tire 24.1 per cent, less than narrow tire, On dirt roads, dry, smooth, free from dust, wide tire 26.8 per cent. less than narrow tire On clay road, with mud deep, and drying on top and spongy beneath, wide tire 52 to 61 per cent. less than narrow tire, On meadow, pasture, stubble, corn ground and plowed ground from dry to wet, wide tire 17 to 120 per cent. less than narrow tire. On the other hand he found that when the roads were covered with a deep dust, or with a thin mud but hard be- low, the narrow tired wagon gave the lightest draft. Also when the mud was thick and so sticky as to roll up on the wheel, loading it down, and again when narrow. tired wagons had made deep ruts in the road which the wide ' Bull, No, 39, Missouri Agr. Exp. Station. tired wagon tended to fill up, the narrow wheeled wagon gave the lightest draft. 538. Size of the Carriage Wheel. s plain from what has been said, that on yielding road-beds the draft must necessarily be heavier, other things being the same, the smaller the wheels of the vehicle. This must be so both because small wheels present less surface to the road-bed to sustain the load, and because when the wheel has de- pressed the surface it must move its load up a steeper grade than the large wheel. It follows also from these state- ments that wagons with small wheels must be more de- structive to the road itself, whether this be of dirt, gravel, stone or iron. Some unpublished data bearing upon this point are given here by permission of Prof. T. J. Mairs of the Agr. “Exp. Station, Columbia, Mo. Wagons with three sizes of wheels were used in these experiments : 1. High, 44 inch front wheels and 56 inch hind wheels. 2. Medium, 36 inch front wheels and 40 ineh hind wheels. 3. Low, 24 inch front wheels and 28 inch hind wheels, all having tires 6 inches wide. The total load including the wagon was: For 1, 3,762; for 2, 3,580, and for 3, -3,362 fons The drafts in his trials are stated in the table below: High Medium Low Description of Conditions. wheels. | wheels. | wheels. Lbs per| Lbs. per} Lbs. per Dry gravel road; sand 1 inch deep; some small, ton. ton. ton. HOOSOISLODESS nase. o: Seno meinen Tone Seer ares Seale ness 84.48 90.45 110.2 Gravel road up grade 1 in 44; covered with one-half inch wet sand; frozen orca paidcste- lek es 123.0 132.1 173.1 Dirt road frozen ; thawing one-half ‘inch: rather rough; mud sticky ee eer oe tein an rene oes 100.6 119 2 139.1 Timothy and blue grass sod, dry, grass cut......... 131.9 145.2 178.8 Timothy and blue grass sod, wet and spongy. 172.9 202 6 281.1 Cornfield, flat culture, with Span teat cultiva- tor; across rows; dry on top.. hae Ae 178.5 201.2 265.1 Plowed ground not harrowed, dry and cloddy...... 252.5 302.8 373.6 27 438 For use on the farm the advantage of truek or low wheels comes in the saving of labor in high lifts in placing manure and other materials upon the wagon, and here a sacrifice of strength of the horse may advantageously be made to save that of the man. A lighter draft and lower life in handling loads are secured by using the low down carriage bed in the upper part of Fig. 211, than are possi- ble with the very low whecled wagons shown in the same eut. 539. Distribution of Load on the Carriage.—\Vhen there is nothing to prevent doing so, the load carried by the wagon should be so distributed upon the wheels as to be di- vided proportionately to the surface the wheels present to the ground, and when the front wheels are smaller they should carry a smaller load. When eare is not exercised LLL in this matter there is danger, especially on soft roads and. in the field generally, of very materially increasing the labor of hauling. When the load is heaviest on one side the wheels of that side are unduly depressed, thus increas- ing the draft. The tilting of the wagon in this way throws 439 the center of the load to one side still further and to a very serious degree if the load is high, as is the case in hauling hay or cord-wood. 540. Heaviest Load on the Hind Wheels.—Jn loading the ordinary wagon the heaviest load should be placed on the hind wheels fer three important reasons: First, because they are larger and will not depress the road-bed so much and will draw easier if they do; second, when the wheels track, the front wheels make a road, by firming the ground, over which the balance of the load may be more easily drawn; third, when the axle of the front wheel is free to be turned, as in the common wagon, the slight inequalities of the road-bed tend all the time to keep the tongue vibrat- ing, so that there is a strong tendency, by this to and fro swinging, to cause the front wheels to cut more deeply into the ground and thus increase the draft. On a very rigid road-bed this matter is not as important as in doing field work, but the differences are large enough on earth roads so that they should never be overlooked. In the following table some observed differences are re- corded : Dry sheep Dry pasture, meadow. Lbs. per ton.|Lbs. per ton. Moad equally, oncourawheels scm + cs6 . o/c ! CO bo PARTS PLAYED BY THE DIFFERENT INGREDIENTS. The atmosphere as a whole, in its relation to living forms, plays the important function of an equalizer of tem- perature, preventing the occurrence of such excessively high and extremely low degrees as would otherwise be pro- duced when the sun is above or below the horizon. 610. Oxygen.—Oxygen is essential to both plants and animals, it being indispensable to the activities of the proto- 490 plasm of living cells, whether this be in the root, stem or leaf of plants or in the tissues of animals. In the develop- ment of muscular and nervous energy large quantities are used by the animal kingdom, and other large volumes are used by man with fuel as a source of power and heat. 611. Nitrogen.—The nitrogen of the atmosphere is pri- marily the source of all nitrogen compounds of living forms; and by its dilution of all the other ingredients it modifies their physiological effects. 612. Water.— Moisture in the atmosphere greatly influ- ences the temperature of the earth’s surface, as it is very opaque to dark heat waves radiated back into space. The frosts forming under clear skies and the absence of them when the air is damp are evidence of this influence. But the chief function of water is found in its large movement to the land in the form of rain and snow and its return from the fields through springs and rivers to the seas. As it falls it is food for plants and drink for animals, as it re- turns it carries away soluble salts which, if left, would de velop sterile “alkali” lands. 613. Dust.—The dust particles give to the sky its blue color and by their radiation of heat into space become cold centers upon which moisture condenses and snow flakes form. In this way they greatly influence the precipita- tion, making it less violent than it might otherwise be. 614. Carbon Dioxide.—Carbon dioxide is the source of all the carbon entering into the constitution of the tissues of both plants and animals, and it is a constituent of the great majority of feeding stuffs and of most organic com- pounds. From recent investigations it is held that carbon dioxide plays an important part, with water, in lessening the transparency of the atmosphere to dark heat rays radiating from the earth into space, and in this way holds our tem- 491 perature much higher than it could be with this gas absent; and Chamberlin has proposed the working hypothesis that long period changes in the amount of carbon dioxide in the atmosphere may be the cause of the recurrent glacial periods to which the earth has been subjected. 615. Pressure of the Atmosphere.—T he air, like all other substances, has weight, and this weight causes it to exert pressure proportional to the amount above a place. Its mean pressure at sea level is equal to 14.73 pounds per square inch. A) j Cos \ 502 South of the equator, where it is winter, the high pres- sure ealm belt has moved nearer the equator so that the air is blowing off the three continents and they are experienc- ing their dry season. 628. Monsoon Winds.— Where the world system of winds is so strongly influenced by the land areas as is the case notably in the region of the Indian Ocean they have been given the special name of monsoons, and these give to In- dia its rainy season, when they blow from the ocean, and its dry season, when they blow from the land. ORDINARY STORMS. Besides the world system of winds, which have been de- scribed, and the continental winds with their intensified forms called monsoons, which change with the seasons, there are others of smaller magnitude and shorter duration which give rise to our ordinary storms and the still more local tornadoes and thunder storms which are associated with them. These are technically called cyclones or ey- clonic storms. 629. Cyclones.—Most of the rainfall of temperate climates and much of that which falls between the tropies and the equatorial calm belt, occurs during the passage of these cyclonic systems of wind movement, represented in Figs. 238 and 239. In these winds the surface air moves spirally about a center, going to the east as it passes toward the poles and to the west of the center when it comes toward the equator. Air coming from the eastward of a cyclonic center always passes to the polar side, while that coming from the west always passes to the equatorial side. 630. Cause of Wind Directions in Ordinary Storms.—The cause of the wind directions in ordinary storms is the same as that of the direction of the general earth currents, that is,—the form and rotation of the earth. As the air leaves the equator it passes over land moving eastward slower than it and hence outruns, appearing to blow from the Bre) oe iG. 288.—Diagram of surface winds in a typical cyclone. (After Ferrel.) S. W. toward the N. E. in the northern hemisphere, and from the N. W. toward the 8. E. in the southern hemi- sphere. If it approaches the equator it travels over land moving eastward faster than it does and hence appears to come from the N. EK. in the northern hemisphere and from the S. E. in the southern. Where the wind approaches the center from the east it can only do so by having its eastward motion with the earth made slower than the earth’s surface in the same latitude ; dO04 while if it approaches the center from the west it ean only do so by traveling eastward faster than the earth itself and these changes in velocity cause winds from the west. to move toward the equator side of the storm center, while those from the east always go to the polar side. The effect is the same as would result from checking or increasing Anticyclone Fie. 239.—Diagram of upper winds in a typical cyclone. (After Ferrel.) the rate of rotation of the earth upon its axis. Making it rotate faster would throw the air and water also toward the equator, while slackening its speed would permit both air and water to move toward the poles. 631. Progressive Movements of Storms.—Cyeclonic storms in all parts of the world have a progressive movement 505 FIG, Chart I. Tracks of Centers of Low Areas. March, 1900. — 240.—Chart of paths of Low areas across the United States, March, 1900, 506 across the earth’s surface and the general direction is that of the prevailing winds of the part of the earth in which they are. That is, in the temperate zones they tend to move away from the equator and toward the east, while in the tropical zones they tend to move toward the equator and toward the west. 632. Direction of Storms in the United States.—In the great majority of cases the storms of the United States travel from some westerly toward some easterly point and the mean direction is a little north of east. Very many of these storms travel for a time from the northwest toward the southeast until they near the longtitude of the Missis- sippl river, when they very often turn their course strongly to the northeast, and Fig. 240 represents the course of the storm centers as they traversed the country during March, 1900, there being 13 of them in all. Wherever the storms of the United States originate or enter the territory they nearly all leave it by crossing the New England states. 633. Rate of Travel of Storms in the United States.— There is a very wide range in the rate at which the storm centers progress across the United States, but the average is from 26 to 30 miles per hour. ‘The circles in the paths of the several storm tracks in Fig. 240 mark the positions of the storm centers at intervals of 12 hours. 634. Diameters of Storms.—'The diameter of these ey- clonic wind systems in the United States is generally from 1,500 to 2,000 miles, the longest diameter being usually from the southwest to the northeast. A typical one of these storms is represented in Fig. 241, where the heavy lines are drawn through places having the same weight of air above them, while the dotted lines are lines of equal temperature. Tt will be seen that this wind system reaches from north of the Great Lakes to well into Texas and from North Dakota to Tennessee. 5O7 Fic. 241.—Chart of strongly developed low area in the vicinity of the Great Lakes. 635. Duration of Ordinary Storms.—'The length of time one of the ordinary cyclonic storms of the atmosphere lasts is very variable. In some cases they are of but a few days duration ; at other times they last for wecks together and in that time travel long distances. It is common for them to cross the United States, the North Atlantic and the whole of Kurope; and one, unusual at least in the completeness of its known history, has been followed from the vicinity of the Philippine Islands, across the Pacific, across North America and the North Atlantic; across Europe and well on toward the central portion of Siberia, where lack of sufficient observations prevented following it farther. 636. Relation of the Region of Precipitation to the Storm Center.—The region over which rain or snow falls during 508 the passage of cyclones across the United States lies usu- ally in advance of the central LOW, much as represented by the heavily shaded area in the diagram Fig. 242, and at a distance of 200 to 700 miles from the center. In this area the precipitation is most continuous and steady over the eastern and northern portion, where the surface winds range from 8S. EK. to N. EK. in direction. To the southeast and south of the low center, where the winds are S. and 8. W., there is a general tendency for the pre- cipitation to oceur in the form of showers, to be more vio- lent in character, and local rather than wide spread. Fig. 242.—Diagram of storm area. 637. The Origin of Ordinary Storms.—There is as yet no general agreement among students of meteorology regard- 5O9 ing the origin of cyclonic winds and storms, some think- ing that the low areas are primary and that the areas of high pressure result from the overflow of air from one or more of these which overlap; while others maintain that the high areas are primary and that the low areas are see- ondary. At the present time the former view is able to bring much the stronger evidence to its support, so far as the operation of well established physical principles are concerned, and, with some modifications, seems likely in the end to prevail. 510 CELA ER ALY: WEATHER CHANGES. The forecasting of weather changes from 24 to 36 hours in advance is based upon several well established facts: (1) Rainy or cloudy weather is usually associated with areas of low pressure, about which the winds move as rep- resented in Fig. 242. (2) Fair or clear weather is usu- ally associated with regions of high pressure. (3) Both low and high areas have prevailing dimensions and move im the United States from the west toward the east. If areas of low pressure always had the same diameter, and if they traveled at the same rate and in the same di- rection, it would be possible for anyone to forecast the weather changes with much certainty 12 to 36 hours in ad- vance. But with all the irregularity of form, dimension, intensity, rate and direction of motion, it 1s possible for even a local observer to form a rational judgment of the approach, time of arrival and passage of an ordinary storm. Indeed, it will seldom happen that a strongly de- veloped storm can approach a locality without giving sure signs of its coming 12 to 24 hours in advance. 638. Prevailing Winds.—In the forecasting of weather changes it is Important to have clearly in mind the direc- tion of the prevailing winds of the locality, or those which are not due to the storm whose approach is to be forecast. In most parts of the United States east of the Rocky Mountains the prevailing fair weather winds are from some westerly quarter and they should be the southwest winds of the general world and continental system unless modified by local conditions, such as give rise to “land and sea breezes” or “mountain and valley winds.” 514 639. Locating the Storm Center.—When the weather has been for some time fair and the prevailing winds are blow- ing, the first indication of an approaching storm is usually to be found in the long thread-lhke or hair-like curved eir- rus clouds represented in the outer front side of Fig. 242. If these are seen strongly developed in any quarter of the sky it is usually true that a more or less strongly developed low area exists in that direction. If these appearances first develop to the east of a north and south line the first probability is that this storm will not reach the observer because it is already past and tray- eling away from rather than toward the place. On the other hand if the cirrus clouds show themselves well developed to the west of a north and south line, and especially if between the southwest and northwest, then a storm center is located where its future course may bring it over the locality. 640. Change in Wind Direction.__If a storm is approach- ing from the westward in the direction of the cirrus clouds these will advance and in a few hours will overspread the sky, the wind will decrease and finally shift to a direction which will indicate the approach of the storm, and more definitely the direction of the low area from the observer. 641. Direction of the Storm Center Indicated by the Wind.—When a storm has advanced far enongh to give definite direction to the wind it is then possible to judge from this the location of the storm center. Standing with the back to the wind and extending the right arm directly in front, and the left arm at right angles to this, the storm center is usually in a direction somewhere between the two hands; this will be clearly seen from a study of Fig. 242 and also of Fig. 241. It will sometimes happen that winds blowing outward from a HIGH, or region of heavy pressure which has passed to the eastward, may be mistaken for those due to an approaching storm, because they are easterly, but the DD character of the sky and the weather, with experience, will usually serve to distinguish these anticyclonic winds from those belonging to the cyclone or storm proper. 642. Discovering the Course the Storm Is Traveling.— After having observed the existence and direction of a storm center 1t is Important to know whether it will pass to the north or south of the locality or whether it will move directly across it. This can be foretold by the changes in the direction of the wind. Referring again to Fig. 242 it will be observed that if the storm center comes directly toward the observer the direetion of the wind will hold steady in the S. E. until after the storm has passed, when it will shift abruptly to the N. W., as indicated by the ar- rows laid on the axis of the storm track. If, however, the storm center is passing considerably to the north of the ob- server the winds will shift toward the south, finally becom- ing S. W. But if the low area is passing to the south of the observer then the winds will shift around by the north, becoming finally N. W. and then W. If the winds hold steady, or if they shift to the north, a general rain or snow may be expected, unless the storm center is too distant, but if it is shifting toward the south, showers, rather than widespread precipitation, may be an- ticipated. After watching the progress of storms during two or three months, comparing them with the daily weather maps, one becomes able to recognize with much certainty the approach of all well marked storms and to forecast their course and the character of the weather 12 to 24 hours in advance. Mistakes will occur, just as they do with the Weather Bureau expert having a much wider knowledge before him, but with a little experience. the judgment becomes much more reliable than would at first be expected. 643. Temperature Changes Connected with Storms.—Dur- ing the colder portions of the year the temperature changes, which are associated with the progress of a storm across Ayilt cy the country, are often very marked. The general rule is that with the approach of a storm the temperature rises above the normal for the place and season, if it is the cold part of the year, but after the storm passes the temperature falls below the average. The rise in temperature is due to three causes: (1) The warming of the air by the heat due to the condensation of moisture; (2) the checking of radiation by the moisture in the air; (3) the importation of warmer air from farther south under the influence of the storm center. It was shown in (41) and (42) that the formation of a pound of water at 212° from a pound of steam at 212° is associated with the development of 966 heat units, and the freezing of a pound of water is also associated with the ap- pearance of 142 heat units. When, therefore, a pound of snow forms in the air from a pound of water vapor there is imparted to the air in which this oceurs 966 + 142 = 1108 heat units and if snow enough falls to represent an inch of rain the heat produced in the air is at the rate of about 62 IL sh: om = 5761.6 heat units a per square foot of the surface upon which the snow falls. The warming of the atmosphere when it snows heavily must be very considerable and this is why it is seldom more than a few degrees below freezing when a heavy snow is in progress. The low temperature following a storm is due to three chief causes: (1) The rapid loss of heat by radiation from the ground under the clear sky; (2) the descent of cold air from high altitudes; and (3) the importation of colder air from farther north under the influence of the storm center. If reference is made to Fig. 241, it will be seen that the southeast quadrant has a mean temperature of 59° F., while the northwest quadrant has a mean temperature of 514 only 17° F., 42° colder. In the northwest HIGH there is a temperature of —10° F., while to the east of the LOW, above 60°, or a difference of 70° F., and while a part of this difference is due to difference of Iatitude, most of it is due to the effect of the storm. 644. Barometric Changes Connected with Storms.—|)ur- ing the progress of a storm across a given station the bar- ometer falls more or less gradually until the center has reached the place and then it begins to rise, and may con- tinue to do so until a pressure greater than is normal has been attained. The changes of the barometer, therefore, become indices of the approach, progress and passage of a storm, and so, too, in a less degree, may temperature changes also, during the winter. If the barometer falls faster than usual, if the wind velocity increases rapidly and rapid changes in the wind direction oceur, the indica- tions are either that the storm center is approaching at a high rate of speed or that its diameter is small and hence that it is likely to arrive sooner after indications have de- veloped. 645. Cold Waves.—Cold waves in the United States are usually the result of a strongly developed storm which has traversed somewhat slowly the southern and eastern states. When these conditions prevail a HIGH area with clear sky and descending cold air from above forms over Mani- toba, or the northern boundary of the United States, and the strongly developed. LOW area, traveling slowly, sets this body of cold air in motion toward it, which often at- tains a velocity of 25 to 40 miles per hour. Under these conditions intense cold is rapidly transported southward and eastward with the speed of an express train, and ocea- sionally temperatures even below zero are transported as far south as northern Alabama. Besides the extremely cold waves just referred to there are others more common, which are due principally to the first two causes named, and are usually coincident with the Or HIGH areas, following them in their course aeress the country. 646. Forecasting Warm and Cold Weather.—Since strongly developed storms tend to draw the air into them- selves across long distances, it is clear that when they pass to the south during the cold months of the year cold waves are likely to follow their passage. On the other hand, if the low area has passed to the north it can only bring air from the south northward, importing but little cold with it. To be able to forecast the path of a storm then is also io be able to forecast the temperature changes which are likely to follow. 647. Long Warm and Dry Periods.—It frequently hap- pens that a series of storms follow along a single track, one after another for several weeks together, and Fig. 243 rep- | Fig. 243.—Chart showing conditions which determine dry weather in the eastern United States. resents one of these sets of conditions. During the month of October, 1895, all but four of the fifteen low areas re- 516 corded by the Weather Bureau, moved along axes within the northern belt marked “axis of low areas.” It is clear that so long as such conditions as these pre- rail but little rain could fall in the United States, and all the northern portion must have unusually warm weather. The weather must be clear and dry because along the axis of high pressure the air is descending from the higher al- titudes where it is already dry, and in descending must become still dryer because of increasing temperature due to compression. As this is the air which must be drawn toward the low areas on either side of the axis it could con- tribute but little moisture for rainfall in either system of lows, and the map shows that but little fell. Scaleof miles 5 Pie. 244.—Path of the West Indian Hurricane of Sept. 1-11, 1900. So long as a high pressure oceupies the Gulf and At- lantic states, this effectually shuts off the moist gulf and ocean air and forces the storm centers to maintain a high northerly course. Then, too, as long as storms pursue a alee course off the Atlantie border they also must shut off the moisture from the northern states and tend to maintain warm, dry weather there. Whether in this case the two systems of low areas were the cause of the belt of high pressure which prevailed, or whether the high pressure belt simply marks the place where, for some reason, the upper air from the general wind system was falling to the earth, the outcome, so far as the weather is concerned, must be essentially the same. 648. Tropical Cyclones.—-[)uring the latter part of Aug- ust, September and the fore part of October it frequently happens that storms of unusual magnitude, intensity and destructiveness originate in the north tropical zone of trade winds, somewhere in or to the east of the Carribean Isl- ands and, after traveling westward with the prevailing Ne o\\ SY Sox Cape naitien Santo Dp, in oy es Fie. 245.—Path of West Indian Hurricane of Aug. 7-14, 1899. winds of that zone, they finally make their way northward across the tropical calm belt and break into the zone of southwest winds, making their way northward and east- ward, as represented by the two storm tracks in Figs. 244 and 245, the former being the storm which produced the terrible destruction of life and property at Galveston on 32 518 September 8, 1900, when more than 5,000 human lives and $20,000,000 of property were lost. The severe cold winds which are designated as the “Northers of Texas” owe their origin to storm centers of unusual intensity off the Gulf coast, which set large bodies of air in motion from the northward, drawing it into them- selves as they pass along to the southward and eastward. THUNDER STORMS, HAIL STORMS AND TORNADOES. Associated with the ordinary storms which have been deseribed in a preceding section there are others much more local in their character, shorter in duration, but often more violent in wind movement and precipitation. These are thunder storms, hail storms and tornadoes. 649. Relation of Tornadoes and Thunder Showers to Ordi- nary Storms.—(Careful study of the time of occurrence and distribution of these storms has shown that they are almost always associated in a definite way with some cyclonic wind movement, and that they usually originate to the southeast, south or west of south of a storm center, in the region designated by the cumulus clouds in the diagram, Fig. 242. 650. Tornadoes.— Tornadoes are whirling winds of ex- treme violence which last but a short time, progressing al- most always from the southwest toward the northeast, often at the rate of a mile per minute, sweeping a belt 40 to 80 rods wide and several miles long. Sometimes the width of the zone of destructive winds may reach a full mile. At the center of the tornado the moisture is swept together by the revolving winds into a dark funnel-shaped cloud, where the velocity of the whirling air may be so great that few structures can withstand the enormous pressure they develop. 7°” EAC = c ester es ee : we >, —_ > Ci th gt ma,” r storms, ram showing the crigin ot tornadoes and thunde 246.—Diag PIG. 020 651. Schools of Tornadoes._—_When the conditions are ex- tremely favorable for the formation of tornadoes they often appear in schools, originating one after another or simul- taneously, as the main storm center progresses across the country, and Fig. 246 shows how these local but violent storms are related to a storm center and how many may develop in the southeast quadrant as it travels along. In this figure the short, heavy straight lines to the southeast of the center represent the paths of tornadoes which devel- oped during its course. 652. Distribution of Thunder Showers.— Thunder show- ers, like tornadoes, originate in the great majority of cases to the southeast and south of a well developed storm center and often large numbers of them, scattered over consider- able areas, form as the storm progresses, much as is the vase with tornadoes, and Fig. 247 is a diagram showing the advance of the front along which thunder showers orig- inated in a storm of early May, 1892, as recorded in the Monthly Weather Review of that month, p. 138. On May 3 a long low area had advanced from the south and west and at 8 P. M. its lowest portion was central north of Lake Huron. The front of the thunder shower line had reached the east end of Lake Erie at 2 P. M. of the same date and showers were in progress along the line marked 2 P. M. in Fig. 247. As the storm center ad- vaneed the thunder-shower-front also moved forward and swept across the state, as shown by the curves on the dia- gram, reaching Long Island at 2 A. M. on the morning of May 4th, the front thus progressing from 20 to 30 miles per hour. 653. Conditions Under Which Thunder Showers and Tor- nadoes Originate.—In the diagram of Fig. 246 are repre- sented the wind directions and temperature relations which exist when conditions are favorable for the formation of both of these classes of storms. There is a region of warm moist southerly winds to the south and east of the low area 521 and another region of decidedly colder winds blowing from the west and north of west; and it is along the meet- ing of these two systems of winds that thunder showers tend specially to form, and in advance of it that the tor- nadoes have their birth. MiG. 247.—Diagram showing the progressive development of thunder StOrmMs. 654. Formation of Tornadoes.—The most satisfactory ex- planation of the formation of tornadoes is represented in the lower portion of Fig. 246, which is a cross-section of the lower portion of the atmosphere at right angles to the line dividing the two systems of winds shown in the upper portion of the same diagram. It is supposed that, under these conditions, the cold west and northwest winds at times over-run the moist warm and lighter southerly stratum, thus producing a condition of unstable equilibrium. When such conditions have been developed the warm air, at some point, is supposed to break up through the over-running colder layer, as shown in the lower right-hand corner of the diagram, and in do- KOC 522 ing so is thrown into a rapidly whirling movement in the same manner that water runs into whirls in discharging through the bottom of a wash-bowl. When the volumes of air which must change places are large and the stratum of cold air deep, there comes ultimately to be developed an enormous rotary velocity which gives to the air an ex- tremely destructive power. Fie. 248.—Diagram of the path of a tornado. 655. Explosive Violence of Tornadoes.—At the center of a tornado cloud the rapidly whirling motion reduces the air pressure at the center of the funnel so much as to pro- duce a high vacuum, and when a building lies in the path of the funnel the vacuum surrounds it so suddenly that, often the great pressure of air within the building will throw the walls outward or lift the roof off before the air has time to escape into the vacuum formed by the tornado. 523 656. Unsteady Action of Tornadoes.— A tornado seldom displays a uniformly destructive power and oftentimes the point of the funnel fails to reach the ground and con- siderable gaps are passed in the path where little damage is done. This unsteady action is often due to the slowing up of the rotary motion in the cloud due to the great fric- tion developed at the ground. After withdrawing to the upper air the speed increases sufficiently to allow the fun- nel to grow to the surface again and resume the destructive work. When the funnei reaches the surface it does not always describe a straight path along the ground, but tends to cross and recross the main axis of movement. OPEN FIELD OPEN FIELD 42 FEET \NOT TORN 4SFEET)NOT TORN poo TORN Coe SESH TORN |OOWN BU ISuEey TORN pNoT!ToRN, BUT FILLED IFILLEO § DOWN jFnceowir [ED WITH COWN |TORNIDOWN WITH A UB- twitk |RUBBIEH, sd WN {BISH ON ispisn | JON NORTH sSOUTH sive fon THE! Sipe : {NORTH 1 RAIL FENCE x RAIL FENCE Fic. 249.—Diagram showing the rotary movement of winds in a tornado. 657. Character of the Tornado Path.—It is usually true that the path of a destructive tornado is not symmetrical, one side being wider than the other, as represented in Fig. 248, where it will be seen that the northwest side is nar- rower than the southeast side. Not only is the zone of de- structive winds wider on the south side but that of the sensible winds is also. On account of this character of the tornado track it is clear that if one has an occasion to escape from an ordinary tornado, the shortest path would he to the northwest, at right angles to the line of progress. The evidences of a rotary motion of the air in a tornado are abundant and conclusive, and in Fig. 249 are repre- sented some of these. 658. Formation of Thunder Showers.—Thunder showers appear to have an origin similar to that of tornadoes, but evidently occur where there is less air to change places, and probably also where the depth of the overlying stratum is less. Indeed, it appears very often, if not generally, true that a volume of cold heavy air has dropped directly to the ground and is moving bodily against the warmer moist air, which it is forcing upward, as represented in the lower left-hand corner of Fig. 246. The rapidly ascending warm moist air is cooled by expansion and by mixing with the cold air, thus giving rise to the heavy precipitation so often observed. The horizontal rolling movement shown in the diagram is often violent enough and involves so great a hight in the atmosphere, that often raindrops are carried round and round until they become very large before they are able to fall. If the vertical cireulation reaches above the zone of freezing temperature the raindrops freeze, forming hail. These hail stones, in the most violent storms, are often carried around with such force and so many times that they become very large before they are able to overcome, by their weight, the velocity of the air, and fall to the ground. 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