XIV INTRODUCTION. 



But, if he be permitted to ascend from the effects to 

 their causes; if we can determine, and demonstrate to 

 him, the action which is exercised upon vegetation by 

 the air, water, heat, and hght, the sun, various kinds 

 of manure, Sic. &c., and assign to each of these agents 

 the part which it performs in these grand phenomena, 

 how much will he be moved I Even whilst an igno- 

 rant witness of these wonders, he is lost in admiration 

 of them : but, more enhghtened, he will feel this sen- 

 timent constantly increasing, as he rises to the causes 

 which produce them. 



Convinced that we must look, for farther improve- 

 ments in agriculture, to the application of the physical 

 sciences, I think it proper here to establish some general 

 principles, the more complete developement of which 

 will be found in this work. 



The laws of nature are eternal and unchangeable. 

 The natural state of bodies, their respective situations, 

 the changes which they undergo, the phenomena of 

 decomposition and of composition, which animate the 

 whole surface of the globe, are the results of these laws. 



We see, everywhere, that matter is governed by two 

 general laws ; by the power of which all bodies exist in 

 their natural state. The first is exercised upon masses 

 of matter ; the second, upon those molecules of which 

 masses are composed. The one is the general law of at- 

 traction, or gravitation; the other, the law of affinity, 

 or chymical attraction. 



The law of affinity (the only one of which I shall now 

 speak) tends constantly to draw together the particles 

 of which bodies are composed. If this force acted 

 alone, the degrees of density exhibited by bodies in their 



