DRAINAGE. 4.12 DRAKE. as given in Table 1, >y tlic square root of the grade upon whicll. it is proposed to lay the main, as t'ound in Table '2. When it is desired that the main shall carry 1 inch in depth per .T^^-:'^-:^^ Cross-iiectiox of drun, Sbowiiig tile in place. acre in twenty-four hours, multiply this result by 24: if one -half inch, multiply by 48; if one- fourth inch, nniltiply liy Hij. There is nuic-h dillerence of opinion as to the proper depth and distance apart of drains. fSniith, an early worker in this field, at first advocated placing the drains from 2Vj to .3 feet deep, and at intervals of from 10 to 40 feet according to the nature of the land. E.vpcrience, however, has been gradually favoring deeper drains, beyond the reach of plant-roots, and at wider intervals. Even on the most tenacious soils, with subsoils of till, few now think of having drains less than 3 feet in depth, though the distance apart should not in many cases be more than from 25 to 30 feet. The depth, how- ever, depends greatly on the soil — S'.j and 4 feet, with the leader drains 6 inches deeper, are common dimensions. In peaty land the depth has sometimes to be 7 feet. The widtli between drains depends on the wetness of the land and the character of the subsoil. King states that in loose, loamy soils, and especially if under- lain by sand, good drainage will be secured with drains 100 feel apart and .'ii.l. feet deep. On heavier soils, they must be closer." The follow- ing table, given by Parkes. may he studied with profit in this connection: M*89 OF Soil Draixed for Dikferext Depths axi> Dm- TAXTES OF TlL« Depth of drains DiBtanre between drains Mawi of Hoil drained perncpe Feet a 3 4 Feet 24 334 .TO Cubic yards S.MCJ 4.840 6.4.M The principal advantages of drainage of ordi- nary farm-lands are: (1) The removal of stag- nant water, the presence of which favors the formation of chemical compounds injurious to crops, keeps the land cold by evaporation, and delays not only plowing, planting, and sub- sequent tillage operations, but harvesting; (2) the deepening of the surface stratum of friable soil, with the consequent increase of feeding ground for the roots of plants, and the increa.sed capacity of the soil to absorb rains and manures and to retain them and also capillary water during the summer. Drainage is also one of the most etlicient means of removing excess of soluble salts from alkali .soils (q.v.), and thus rendering them tit for the growth of useful crops. Subsoil drainage has been perhaps the most valuable improvement connected with agri- culture. For further information, consult: Btorer, .lyriciillurt-, 7th ed. (New York, 18!)7); DIAGRAM OF DRAIXED FIELD. Stiowlng angle at which branches meet the main drain. Miles, Land Draining (New York, 1807) : King, Irrigation and Itrninagr ( N'ew York, 18!Mt) : and Elliott. "Earni Drainage." in I nitrd tilatea Dr- parlnient of Agrirnllure, l-'armcrs' liallelin JjO (Washington. 1806). See Sw.vmp; S.v.NyA: Bog ; Alkali Soil. DRAINAGE. For the use of this term in phy-in^iaphy. sii' RivKK : Valley: Geology. DRAINAGE TUBES. In surgery, tubes of rublnr (u- ghis- cmpliiycd for removing pus or septic matter from tissues or from cavities. The rubber drainage tulH>s are the ones most fre- quently used. They are of soft rubber, from % to ';; an inch in diameter, and from a few inches to seven or eight indies in length, or even longer, and are perforated l)v nuinciinis holes, from an eighth to onc-iniartcr of an inch in diameter, thmughout their length. The glass tubes are used mainly for abdominal work, and are of large diameter, usually from three-eighths to five-eighths of an inch. For special purposes tubes of metal and hard rubl>er have lM>en em- ployed. When placed in fresh wounds, or in the body cavities after operation, when suppura- tion is alisent. their object is to remove hlood, serum, or discharges which by their sulwequent accumulation might become a source of septic infection. Drainage tubes were first introduced by the distingtiished French surgeon Chas- saignac. DRAKE, AiKXAxnER Wilson (1843—). An .incri<aii artist and critic, horn at Westfield. N. .T. He studied oil and water-color painting, and practiced wood-engraving. From 1870 to 1881 he was the head of the art department of Scribner's Magazine, and afterwards becamB
