THE FARMER'S MAGAZINE. 



91 



instead of being a deduction from sufficient data. He 

 says : " With regard to the comparative extent to 

 wliich this power may reside in old and newly -raised 

 soils, I think there can be little doubt that long-culti- 

 vated dry soil — highly charged as it generally is with 

 humus, and having its particles continually pulverized 

 by the operations of tillage and the roots of plants — 

 will greatly exceed in this respect raw newly-raised soils 

 which have long lain in a dead compact state beneath 

 the furrow. The ferruginous eai'ths that frequently 

 abound in some subsoils will, however, on exposure to 

 the atmosphere, take up ammonia to a considerable de- 

 gree after they have crumbled down under the influ- 

 ence of frost, rains, and drought." 



And a little further on we meet with this inference — 

 " If, therefore, the earth contains much humus, alu- 

 mina or clay, oxide of iron, or magnesia, in a state of 

 fine division, its power of absorbing gaseous matters 

 from the air will probably be good." 



The latter part of the essay consists of an examina- 

 tion of the nature and constitution of the various oxides 

 and earthy salts of which the soil is composed, the 

 geological and mineralogical features of this country 

 being first touched upon, and then the simple miner- 

 als — such as quartz or silica, felspar, mica, hornblende, 

 limestone, &c., from which the endless varieties of 

 strata are for the most part ultimately derived — are 

 taken up in succession, and the way in which it is 

 affected by atmospheric influences shown. We glean 

 the following items of information from complete dis- 

 quisitions on the analysis, history, and qualities of each 

 substance : " Although in its pure crystalline state silica 

 is one of the most refractory substances, it is yet in 

 some of its combinations clearly subject to the solvent 

 effects of the atmosphere and rains, as it is found in the 

 stems of our grain crops, and must therefore enter their 

 rootlets in a liquid form. It is well known as a solu- 

 tion in some thermal springs.".... " Silica exists in 

 the soil in several forms and combinations ; under 

 some of these it is little aS'ected by the atmos- 

 pheric influences, but under others it is susceptible of 

 a gradual dissolution — slow, it is true, but still pgrhaps 

 sufficient in many cases for the wants of the cultivated 

 plants.".... "Felspar is frequently one of the most 

 rapidly decomposing minerals, the atmospheric modi- 

 fications of the soil being often due, in a great measure, 

 to its changes." "Although the decay of felspar is 

 generally referred to the carbonic acid of the atmos- 

 phere and the solvent power of water containing that 

 agent, it appears not improbable that the ammonia and 

 nitric acid of the air may also have a share in pro- 

 ducing this effect." The felspar falls down into a powder, 

 forming a clay ; and the fertility will depend upon the 

 amount of alkalies which have escaped bieng dissolved 

 out. The action of the atmosphere upon mica is appa- 

 rently similar to what takes place ini'elspar, the ultimate 

 result being a clay, the potash or magnesia dissolving 

 out. "The hornblende minerals are amongst the 

 most abundant ingredients of our rocks. They are 

 very liable to be acted upon by atmospheric influences, 

 chiefly through the oxidation of the protoxide of iron, 

 which they so abundantly contain . . . . These igneous 



rocks, decomposing under atmospheric influences, form 



soils generally noted for their fertility Dr. 



Fownes found that phosphoric acid is a very usual 

 component part of volcanic rocks, and i-* a principal 

 source of the remarkable fertility possessed by soils 

 derived from their disintegration." "The principal 

 effect of the atmosphere on calcai'eous matter is to dis- 

 solve it through the action of the rain-water containing 

 carbonic acid." " Hardly any soil or rock exists, 

 perhaps none, of which iron does not enter to some 



extent into the composition Disseminated as it is 



so abundantly and so generally through mineral and 

 earthy matters in the forms of its oxides and salts, 

 it becomes a fruitful source of change and disintegration 

 in their composition. This arises from its strong affinity 

 for oxygen : . . . . the salts of the protoxide of iron have 

 so strong an affinity for oxygen that, on being freely 

 exposed to the air, they greedily absorb that element 

 and pass into the peroxide." 



Now, as a conclusion to the essay, we had expected 

 a summary of the principal changes which occur in 

 soils of different kinds when newly deepened and 

 brought into intimate contact with the atmosphere. We 

 hoped that a sort of balance would be struck between 

 the acquisitions and losses to the soil from absorption, 

 and volatilization, and new advice for summer and 

 winter tillage be thus deduced. The above enumeration 

 of the properties and changes of the various ingredients 

 is unsatisfactory ; for though these changes may be 

 proved to occur when each body is acted upon sepa- 

 rately — what is the combined and resultant i)rocess 

 going on when all the varieties of chemical agents and 

 active ingredients are mingled together, and one action 

 may possibly accelerate, neutralize, alter, reverse, or 

 in some way interfere with twenty more ? Just as 

 homoeopaths tell us that a medicine compounded of a 

 number of drugs, each of which is known to operate 

 in a certain manner when administered alone, will not 

 have the intended result of effecting all the changes 

 due to those remedies. 



The only generalized result which our author gives 

 us is, what everybody knew already, that " the influence 

 which the atmospheric forces exert upon the soil is 

 very various and extensive. Their action, indeed, is 

 not rapid nor energetic, and a very perfect exposure of 

 the soil is necessary to catch much of the ameliorating 

 influence. It is not therefore to be expected that a 

 barren soil can be rendered fertile by mere exposure to 

 the air, although it were wrought with a perfection that 

 would have satisfied even Jethro Tull. The im- 

 portance, however, of taking advantage of the manifold 

 benefits to be derived from the air, it is hoped, has been 

 rendered evident in the course of this paper." And 

 then, with a hint as to the advantages of drainage, he re- 

 commends ploughing land into ridges like potato-drills 

 for winter exposure. " Many other benefits, however, 

 than those of the frost will result. Are the oxygen- 

 ammonia— carbonic acid — nothing ? Let the agricul- 

 tural mind therefore be of good cheer ; the atmosphere 

 is a force everywhere present; although his farm may 

 be like Justice Shallow's — ' barren, barren' — he has 

 at least this consolation — * Marry, good air !' " 



