Advancement of Agriadbiral Science. 385 



composition will enable us to trace to its true orig;in any failure 

 that may have occurred in its use on land previously benefited by 

 its application, and to discriminate between the above source of 

 disappointment, and another w^hich will probably be found con- 

 nected with a deficiency in some other material which the plant 

 requires for its nutrition, and which the salt is not calculated to 

 supply. This kind of knowledge will moreover enable us to 

 predict, not only the kind of soil and the description of crop 

 which the salt will be found to favour, but likewise what other 

 substances are likely to furnish a substitute for it when it chances 

 to be wanting. Thus it may be confidently predicted, that if the 

 operation of nitrate of soda be such as has been represented^ 

 certain compounds of ammonia might to a certain degree serve 

 in its place, and produce those effects upon the crop which have 

 been traced to the evolution of nitrogen from the salt in question. 



I am far indeed from meaning to contend that scientific investi- 

 gations ought to supersede the use of other more empirical 

 methods of advancing agriculture ; for all general scientific con- 

 clusions perhaps are subject to some degree of uncertainty, and, 

 owing to the imperfection of all our knowledge, even the best 

 established truths are liable to mislead, when we attempt to deduce 

 practical inferences from them. No sooner, indeed, have we 

 crossed the threshold of the temple of Truth, than the mists that 

 obscure our path render every fresh step we take in advance more 

 difficult, and may prevent us from steering our course aright, 

 even though assisted by the light which emanates from the sacred 

 precincts. 



But still I cannot but contend, that in conjunction with, or 

 rather perhaps as preliminary to, those empirical trials which 

 practical men are willing to undertake respecting a given manure, 

 it would be highly useful, if a course of experiments were set on 

 foot to determine the exact mode in which it operates upon the 

 soil and upon the crop. And I know not how such experiments 

 can well be instituted, except it be on an experimental farm, esta- 

 blished for the purpose, and placed under scientific hands. Pro- 

 ductive of no immediate advantage to the land on which they are 

 tried, beyond what could be equally well attained by a much in- 

 ferior expenditure of labour, they are not likely to be taken up 

 by any private individual, who combines practical experience and 

 pecuniary resources with the requisite scientific skill ; and even if 

 such a person were to present himself, what guarantee can we 

 offer to the world that he possesses the requisite qualifications ? 



1 therefore fear that such trains of research as I have alluded 

 to will never be conducted in a manner calculated to command 

 he confidence of the public, until an experimental farm be set up 

 or the purpose ; and when so wide and important a superstructure 

 is to be raised upon the principles we aim at establishing, it is 



