38 THE CULTURE OF FARM CROPS. 



corrosive and destructive; and corroding substances com- 

 bined become mild and innoxious. 



The laws which regulate chemical action are precise and 

 inviolable, and the elements unite with each other only in 

 constant and definite proportions. We can mix any two 

 gases together, as oxygen and hydrogen; or oxygen and 

 nitrogen, in any proportion we please; but we cannot com- 

 bine them except in strictly definite quantities. We can 

 burn a pound of hydrogen in any number of pounds of oxy- 

 gen, but the hydrogen will unite with only 8 pounds of oxy- 

 gen and make 9 pounds of water ; and this proportion never 

 varies. We can discharge an electric spark in a jar con- 

 taining a mixture of oxygen and nitrogen, and 8 parts by 

 weight of the oxygen will unite with 14 parts of the nitrogen 

 and form an oxide of nitrogen. If there is any surplus of 

 nitrogen it will be left, and any surplus of oxygen will re- 

 main; only so 'much of either will combine with the other,, 

 and no more and no less under whatever circumstances may 

 exist. Moreover, the very same proportion in which any two- 

 bodies will combine with each other is precisely the same in 

 which they will combine with any other. Thus 1 pound of 

 hydrogen combines with 8 pounds of oxygen, and 8 pounds 

 of oxygen combines w T ith 14 pounds of nitrogen; therefore 

 1 pound of hydrogen combines with 14 pounds of nitrogen. 

 These numbers are known as the combining or equivalent 

 numbers ; but there are multiple proportions required in 

 some cases to produce definite compounds ; for instance, to 

 produce ammonia, it is necessary to take 3 proportions of 

 hydrogen to 1 of nitrogen. The emblems of combinations 

 or the mode of representing them is by using the initial let- 

 ter of the element followed in case of multiple proportions 

 or equivalents by a small figure. Thus N Hg. represents 

 one proportion of nitrogen or 14 (pounds) and 3 propor- 

 tions (pounds) of hydrogen, making 17 pounds of ammonia. 



This beautiful law; beautiful in its precision and its 

 simplicity exemplifies the general law of the universe ; which 

 is, order, invariable and unchangeable. This regulates not 

 only the motions of the planets, the earth, moon and stars,, 



