386 Dr. Daubeny's Lines of Inquiry 



from an abundant supply of those materials which afford it 

 these latter principles in greater abundance than nature her- 

 self could provide them, is to make that distinguished writer 

 contradict the very positions, which, more perhaps than any 

 others, arrested the attention of tlie public in his former 

 treatise, and contributed to the unexampled celebrity which it 

 enjoys. 



Nevertheless, as we are dealing, not with the opinions of an 

 author, but with a question of fact, it woidd be interesting to 

 note the rate of growth in a plant, plentifully supplied with all 

 the fixed ingredients which it derives from the soil, but ob- 

 taining no supply of carbonic acid or of ammonia from any 

 other source than from the atmosphere, as compared with that 

 of another in which the fixed and volatile ingredients were 

 both furnished in equal abundance. This inquiry might con- 

 sist — 



1st. In ascertaining the relative growth of two plants, the 

 one manured with burned bones, or superphosphate of lime, 

 and with silicate of potass; the other also supplied with am- 

 moniacal salts. 



2ndly. In ascertaining the effect upon the crops, of a given 

 weight of stable dung, from which the liquid part had been 

 carefully washed away, as compared with that of the same 

 amount where the latter had been carefully preserved. 



Let us suppose for instance the dung from twenty cows to 

 be applied to a particular description of land, and that from 

 twice this number to be separated into its solid and liquid por- 

 tions, the solid portion being spread over a quantity equal to 

 the former, and the liquid portion over a field also of the same 

 dimensions and quality. The results obtained from an expe- 

 riment so conducted might serve to enlighten us with respect 

 to the above question. 



Another very important train of inquiries connected with 

 agriculture relates to the power which plants possess of de- 

 composing chemical compounds — the limits within which this 

 power is circumscribed — and the conditions under which it is 

 exercised. 



We know, for example, that a plant can decompose a com- 

 pound whose ingredients are held together by a very close affi- 

 nity, namely, carbonic acid — we appear to possess an equal 

 certainty as to the decomposition of ammonia by the same 

 agency — we have reason to believe that certain neutral salts, 

 such as chloride of sodium, nitrate of soda, &c., obey the same 

 force — and we may suspect that the fertilizing influence of 

 other compounds is attributable to the same power — but we 

 still need some further facts to inform us what are the limits 



