SUGGESTER AND INTERPRETER OF EXPERIMENTS. 7 



5. Of the nature of natural and artificial manures, of the 

 general principles and practices of husbandry, of the special 

 husbandry of the district of its physical character, its geological 

 structure, and of its general climatic relations. 



6. Of the habits of the species of plants on which the ex- 

 periments are to be tried, and of the more common varieties of 

 these species their tendency to become prolific, to degenerate, 

 to be attacked by insects, by parasites, or by disease their 

 relations to certain physical characters of the soils in which 

 they prefer to grow, &c. 



7. Of the general habits, principal varieties, constitutional 

 tendencies, and especially of the structure of the digestive 

 organs of the animals on which experiments in feeding are to 

 be made. 



8. Of the exact state of our theoretical knowledge upon 

 points akin to those on which the proposed experiments are 

 intended to throw light, of the experiments (if any) which 

 have been previously made and published in reference to the 

 same subject, of the way in which they were made, and the 

 quality of the results they have yielded. 



9. Of a clear and definite purpose or end, practical or theo- 

 retical, for which the experiments are to be recommended and 

 undertaken. 



In the maker of the experiments, all this knowledge is not 

 required. He cannot possess too much of it for none of it 

 would be superfluous or without its use but scrupulous fidelity 

 and accuracy in all his proceedings, a careful observation and 

 detail of appearances, and a conscientious record of results, are 

 the most essential qualifications on his part. It is as in a 

 chemical laboratory, where a head and hands are both requisite 

 in the chief while, in the subordinates, skilful, ready, and 

 willing hands are most especially required. 



I shall briefly advert to the several heads of knowledge with 

 which the suggester of experiments ought to be conversant. 



3. Substances of which the plant consists. 



The plant consists essentially of two parts an organic and a 

 mineral part. The former burns away when a plant is put 



