DR. DAUBENY ON THE ROTATIOiN OF CROPS, ETC. 183 



he ultimately adopted, and having made such preliminary trials on one of the crops 

 which he afterwards analysed, as tended to satisfy me, that on those points in which 

 the plan differs from that proposed by Dr. Will, our method deserves the preference, 

 on the score of convenience, if not with respect to accuracy. 



In a case of this kind, experience alone can determine the degree of confidence 

 which is due to the results obtained, but I ought not to withhold my own individual 

 testimony to their fidelity, from having witnessed the manner in which they were 

 conducted by Mr. Way, his perfect familiarity with the processes which he pursued, 

 and the scrupulous care taken by him in repeating every step in the investigation, 

 which presented anomalous results, or appeared from any cause open to suspicion. 



But to complete my design, an analysis of the soil, as well as of the crops which 

 grew in it, was requisite, and to this subject therefore my attention was next 

 directed. 



Now, when we consider the nature of a soil in an agricultural point of view, or 

 in reference to its suitableness for the growth of various kinds of vegetables, two 

 questions naturally come before us ; namely, what amount of ingredients capable of 

 being assimilated in the course of time by the crops does it contain ; and secondly, 

 what is the amount of those which are present, in a condition actually available for 

 their purposes, at the precise moment when the examination is undertaken. 



Both the above points are obviously quite distinct from that of the total amount 

 of ingredients actually existing in the soil, and hence some might be disposed to 

 add to the labour of the two preceding investigations, that of ascertaining the whole 

 of its constituents, whether in a state to be affected by the ordinary agents of decom- 

 position, or not. 



The latter question, however, seems to me to possess, with reference to the agri- 

 culturist, only a speculative interest, and when introduced into a Report intended for 

 his use, may be more liable to mislead than to instruct, unless due caution be taken 

 to point out to him, how much of each ingredient is to be regarded as inert, and how 

 much of it as applicable to the future or present uses of the plant. 



Let us take the case of a natural soil, composed of certain kinds of disintegrated 

 lava, or even of granite, in which it is evident, that an actual analysis, conducted by 

 means of fusion with barytes, or lead, or by those other processes which chemists 

 employ for decomposing compounds of a refractory nature, would detect the presence 

 of a large per-centage of alkali, not improbably of a certain amount of phosphate of 

 lime, and in short would indicate an exuberant supply of all those ingredients which 

 plants require for their support. Nevertheless a soil of this description, in conse- 

 quence of the close union of the elementary matters of which it consists, and of the 

 compactness of its mechanical texture, might be as barren, and as incapable of im- 

 parting food to plants, as an artificial soil composed of pounded glass is known to 

 be, notwithstanding the large proportion of alkali which it contains. 



