connected "wilh the Theory of Agriculture. 389 



portionate to that of the shells which the rock contauis — how 

 it can best be disengaged from its combination with the other 

 ingredients of the rock, and be presented in a soluble form to 

 the plant — whether it is generally associated with fluoric acid, 

 in secondary rocks, as it is in primary ones — and whether the 

 presence of the latter be favourable or injurious to vegetation. 



I have studiously avoided particularizing any species of re- 

 search which might have a direct practical ten(lency, being 

 desirous of confining myself to those which could not well be 

 pursued on a farm intended as a model for the neighbour- 

 hood, and a guide to the pupils educated at the establishment. 



A multitude of other inquiries will however suggest them- 

 selves of a more practical character, such, for instance, as in 

 a manure confessedly beneficial to a particular description of 

 land, but containing various ingredients, to which of them the 

 fertilizing influence is to be attributed. In the case of bones, 

 for example, is it the animal matter, or the phosphate of lime, 

 which improves the crop? in the case of the nitrates, is it the 

 nitrogen of the acid, or the alkali which constitutes the base, 

 that operates advantageously? Such inquiries, however, are 

 too obvious to require to be particularly insisted on, but I 

 must make one suggestion with respect to experiments insti- 

 tuted on manures, as of general application, namely, that it 

 would be highly satisfactory, if in every trial the best propor- 

 tion for use were ascertained, by manuring the field operated 

 upon with quantities varying from the smallest to the largest 

 amount which it has ever been recommended to administer. 



Thus, suppose the quantity of guano added to a field of 

 wheat or turneps to vary from 1 to 6 cwt., let the land be 

 divided into six equal strips; let the first strip be drest with 

 1 cwt., the second with 2 cwt., and so on to the last, which 

 will receive ihe largest amount, namely 6 cwt. By weighing 

 the whole, or an aliquot part of the produce of each strip, the 

 most advantageous proportion of this guano for land of the 

 same quality may be estimated with something like preci- 

 sion, and a sort of standard laid down applicable to other si- 

 milar cases. 



The more subtle and delicate investigations which I have 

 ventured to recommend may appear scarcely feasible in an 

 infant institution, unsupported by royal patronage, and merely 

 maintained by the voluntary contributions of individuals, who 

 look to practical ends and to immediate results only. 



That they would require a large expenditure of time and 

 labour cannot indeed be denied, and that it might be deemed 

 imprudent to divert the resources of the establishment to such 

 uses, is not improbable; but if a fund were to be created for 



