n 
stated in the introductory lecture, are very few. 
Oxygene, hydrogene, and carbon constitute the 
greatest part of their organized matter. Azote, 
phosphorus, sulphur, manganesum, iron, silicum, 
calcium, aluminum, and magnesium, likewise, in 
different arrangements, enter into their compo- 
sition, or are found in the agents to which they are 
exposed ; and these twelve undecompounded sub- 
stances are the elements, the study of which is of 
the most importance to the agricultural chemist. 
The doctrine of definite combinations, as will 
be shewn in the following lectures, will assist us 
in gaining just views respecting the composition 
of plants, and the economy of the vegetable king- 
dom ; but the same accuracy of weight and mea- 
sure, the same statical results which depend upon 
the uniformity of the laws that govern dead matter, 
cannot be expected in operations where the powers 
of life are concerned, and where a diversity of 
organs and of functions exists. The classes of 
definite inorganic bodies, even if we include all 
the crystalline ‘ arrangements of the mineral king- 
dom, are few, compared with the forms and sub- 
stances belonging to animated nature. Life gives 
a peculiar character to all its productions ; the 
power of attraction and repulsion, combination 
and decomposition, are subservient to it ; a few 
elements, by the diversity of their arrangement, 
are made to form the most different substances ; 
and similar substances are produced from com- 
pounds which, when superficially examined, ap- 
pear entirely different. 
