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perfect growth. Where the want of fertility arises from the ab- 

 sence of one or more of these constituents, or their being locked 

 up in combinations in which plants cannot use them, chemical 

 analysis is perfectly competent to detect the cause of the evil 

 and point out its remedy. 



But the growth of plants is influenced by a multitude of other 

 circumstances to which chemical analysis can furnish no clue. A 

 soil may abound in all the elements of a very fertile one, and 

 yet be perfectly barren. The soil of the great Colorado desert 

 in California, which I have recently analysed, furnishes a good 

 example of this. It possesses in abund ince every element neces- 

 sary to extreme fertility, but is entirely barren from the want of 

 water. 



The reverse of this also frequently occurs. The chemist re- 

 ceives a specimen of soil, in the chemical constitution of which he 

 can detect no deficiency, and in his laboratory, he can assign no 

 cause for its alleged unproductiveness. An examination of the 

 locality probably shows him that it is underlaid by a stiff tena- 

 cious subsoil, which retains an excess of water, and no provision 

 has been made for drainage. 



The difference in the mechanical texture of stiff and loose soils 

 is familiar to every one. The fertility of many stiff clays may be 

 seriously impaired by ploughing too wet, rendering them tough 

 and impenetrable to the tender rootlets of plants. In this case, 

 as no chemical change takes place, the chemist in his laboratory 

 would seek in vain for the cause of the difficulty. 



Every attempt to improve the character of a soil must therefore 

 be preceded by a judicious consideration of its mechanical texture, 

 its power of absorbing and retaining water, and its capacity for 

 heat. Hence it is important that the agricultural chemist should, 

 if possible, himself examine the locality, in order fully to esti- 

 mate the wants of the soil. The employment by every State, of 

 an agricultural chemist, who should visit in person every part of 

 the State, is therefore strongly to be recommended. 



In the next place it is requisite that an analysis of the soil, in 

 order to be of much value, should be thorough. It must include 

 separate estimations of the parts soluble in water and in acids, 

 and the insoluble portion. For the portion soluble in water rep- 

 resents what is available for the wants of the growing crop, 



