32 INTRODUCTION. 



of obtaining the influence of the ammonia, 100 lbs. of the car- 

 bonate yields an amount of ammonia equal to 146 lbs. of the 

 sulphate. This result has been found out by long experience, 

 but a knowledge of chemical proportions would have pre- 

 dicted it. 



When substances thus combine in definite proportions, 

 the compounds, generally, bear no analogy to either of the 

 constituents. The new substances formed are in the posses- 

 sion of properties entirely new, and which could not have 

 been predicted previous to experiment ; hence two simple 

 bodies by combining in different proportions form entirely 

 different and distinct bodies, as different as common air, 

 the exhilarating gas, and nitric acid (aquafortis), which are 

 compounds of oxygen and nitrogen ; hence it is, that the al- 

 most infinite variety of vegetable productions are formed by 

 the different combinations of a few simple substances. If, 

 therefore, we wish to produce a greater quantity of any 

 given production, we must supply the conditions which will 

 cause such combinations to take place. Thus, for example, 

 where soils are destitute of animal manures, from which the 

 nitrogen may be procured necessary to form gluten and vege- 

 table albumen in wheat, an addition of nitrate of potash, soda 

 or ammonia, will increase the amount of these substances, and 

 render the grain much more valuable ; an addition of 2^ per 

 cent, of gluten has been thus produced in the same weight of 

 wheat, which would add more than 10 per cent, to its value. 



In consequence of the fact, that each substance has a 

 definite and fixed character, we are enabled, by the aid of 

 afl[inity, to decompose soils, and to compare with them the 

 vegetable products ; hence we can not only learn the rea- 

 son of fertility or barrenness, but also how to remedy de- 

 fects, and thus point out to the practical agriculturist the pro- 

 cess which will secure a bountiful crop. If an analysis of 

 the soil be made before and after the crop, we may determine 

 what the effect of any substance is upon it. By the aid of 



