86 OBJECTS OF THE THEORETICAL EXPERIMENTER. 



field and house experiments, he will aim to solve them in re- 

 ference to the special circumstances in which he lives, and with 

 a view to his own especial money profit. It is a part of his 

 profession to make such experiments ; but, at the same time, 

 both to devise and to conduct them so prudently, and on such 

 a scale, that they can never, should they fail, be productive of 

 any loss which he will seriously feel. 



The theoretical experimenter, again, has other objects, which 

 he pursues either alone or conjointly with those which the 

 purely practical man keeps, before him. He tests theoretical 

 views and hypotheses ; tries the value of the deductions and 

 inferences to which the results of analysis" seem to lead ; inves- 

 tigates questions in practical physiology ; inquires into the kind 

 and mode of vegetable nutrition; the relation of manuring 

 substances in composition, form, and chemical or molecular 

 constitution, to the composition and state of the soil, to their 

 action on this or that plant, at this or that period of its growth ; 

 the necessity of this or that substance, in this or that form, to 

 the growth of particular plants in this or that soil or climate ; 

 the influence of one substance in modifying the action of an- 

 other upon a given plant ; of different substances in modifying 

 the composition of the plant produced by their assistance, and 

 its consequent greater or less value for food and other purposes. 



Such as these are the additional questions which the theoretical 

 experimenter seeks to solve by the trials he makes in the field. 

 They are not inconsistent with the questions asked of nature 

 by the practical man. Though higher in aim and character, they 

 may be conjoined with his ; and though they demand know- 

 ledge wider in its range, and more precise in character and 

 involve a greater attention to strict accuracy in the execution, 

 yet in neither respect are they beyond the powers or means of the 

 instructed agriculturist. It is an inducement to the latter also to 

 take up such higher questions, that, by the charm arid interest 

 which attaches to them, they give to rural life a new character, 

 imparting to it a portion of that intellectual exercise and excite- 

 ment for which men usually repair to towns, and the want of 

 which is not unreasonably supposed to retard the diffusion of 

 useful knowledge in all purely agricultural districts. 



