IV CI i iPtinttr.ol,-•° - . ,,, pell'arttnstit. AERATION. • --- AERATION-. i s p--agrieuittire;!..! - 'tined:by Webster,."..ta the 'exposure ••of he soil to the free actiop of air, as essen- Gial to.the growth - of plants." Chem . istry iE is the act of combining with. car. : bopic acitl,..and.is essentially the same process in all cases. The atmosphere consists Of 76 nitrogen and .23 oxygen, with AMA, one part in 500 of carbonic ...Acid. gas, and a very portion :of ac peons yap Or. The air pot' only acts a very, important partin theprocess,of ger : mination,..but furnishes the ,oxygen re - quired . .decompose-: the—carbonic' 0:: • consumed by the living plant, and a large • portion of the gai itself., "It: is . of con sequence, therefore," says Johnson, •qhat this'oxygen of the air should gain . access - to every part of the soil, arrd - thus - to all. the:Tonts ofthe 'plant." This access can be facilitated by any•colture. or Wa.rking which will yender the soil More . porottee '. 4 A square foot of earth in,a_ solid>fo'rm exposes but ,a small .surface- to th,Vaction .'ef the air, and hence abso'rbizfrom 'the '.:tMOSphere bUt pnlvetizTh.this-mass, 4ncLthe N Surface ter:Act - 1,05r exposed, to the. action of :dm i v iiicr e ased .a, millibti .fold, and itslowc4 7 s .Of absorption -from the . atnosp4 it(the sane proportion." So however. w ityout regard to theii2ncehanical porosity of tAtitre, have - been found to absorb. oxygen, With -more ~,,tipidity and in larger qualititylan' oth . Johnston, '‘cabsorb more oxygen than oid or pi...lt - nature - 7than --- Any This eNplains why- so,..littlebenefit , : is ,sometinies derived from fall plowing 'on sandy soils, as well as what terittiOndoes for cltiyey ones. - or rather powr in protoxides of iron and manganese, absorb 'oxygen for conibining with them, wl le ddeaying vegetable matter„ i.n like manner requires a large supply of O±y• gen to aid. their natural decomposition. Besides oxygen and nitrogen, the soil al ,- so, as kefore remarked; absorbs carbonic gas from the 'atmosphere, and pcirtionS.'ef those .*Arious vapors of ammonia and nit rib acid, which, in the the opinion of some chemists, add largely, to its fertility; The great object of.culture is the wra tion of the soil—the putting it-in a state permeable to. air, heat and moisture, through which plants_raceixe the power' of growth.. A deep and mellow soil - also be a moist and warm one, and ,will then be beSt prepared to-absorb` the gas ses beneficial and:necessary to vegetation. ing ddws, assists any Soil in ,deriving.fey tilizing principles from the air. Oil this subject Johnston remarks ;- that the in .Allelic-a of -the dews,and -the gentle- show,. progress-of Tegetation is- limited.to the mere supply of water to the thirsty ground, and of : those vapors .which they bring with them as they. de scA to the earth, but is partly due tilso to the -power which . . they' iintntrt to the moistened soil, of extracting for itself now supplies of gaseous matter from-the sur- rounding atmosphere: • The term tcriition has also been applied - to the change-in tit'c circulating fluids of both plants and - aniMals A by,the an.enc_y_of the air, is the arterialization of the blood by:respiralion, -iii-warin blooded animals.; mid somewhat aludagous prcicess in. the sap of