435 



The most common farmer observes a difference in soils ; and 

 his familiar observation enables him to choose with advantage 

 for his different crops. The most common farmer is aware of 

 the importance of manure. Practice soon teaches a man the 

 times of sowing and reaping and the common modes of saving 

 and using his crops. But why should we be satisfied with 

 this ; and why should we think that this is all? 



The soil may be suited to some crops better than to those 

 which we now cultivate upon it. It may be deficient in some 

 elements ; it may superabound in others. Both of these cir- 

 cumstances may have a material bearing upon its culture and 

 productiveness. It may have intermixtures, which are poison- 

 ous to some products, but which art would enable us to cor- 

 rect, or modify. How shall we come at these secrets but by 

 scientific and laborious chemical analysis ? The subject of 

 manures is matter of vast importance to the agricultural inter- 

 est. As yet we are comparatively in the infancy of knowledge 

 in respect to them. The power of some substances to affect 

 the crop, when applied to the soil, are among the profound 

 wonders of nature. Who, before experience had taught us 

 what it has, would not have ridiculed the idea that half a 

 bushel of ground plaster of Paris strewed over an acre of 

 ground, would cause land otherwise unproductive, to be- 

 come covered with a most luxuriant vegetation and to yield 

 tons of hay to the cultivator ? Yet who will pretend that this 

 is any thing more than the first step in the profound science 

 of manures and their influence upon vegetation. 



Various mineral manures of extraordinary efficacy are now 

 coming into use in Great Britain and in this country, as for ex- 

 ample, saltpetre and the nitrate of soda? What is to solve the 

 secrets of their operation, and consequently determine the best 

 modes and times of applying them, but the science of chemis- 

 try, aided by practical observation ? 



" The fit period," says Daubeny, " for collecting the fruits of 

 the soil, depends upon the physiological fact, that the farinaceous 

 matter which constitutes the nutritive portion of those tubers 



