10 



analysis; or else under the form of 'mixed substances, compound, and ad- 

 mitting of decomposition. Thus, too, organized beings exist under 

 two very different forms of life, which distinguish them into vegetables 

 and animals. 



The first general conception with which we ought to enter upon this 

 comprehensive study of nature, is the mutual dependence of those beings, 

 which, in their co-ordinate whole, compose the system of nature; a de- 

 pendence which requires for each the simultaneous existence of all. Thus 

 a vegetable derives its nourishment from inorganic bodies*, and alters 

 their inert substance, which is unfit for the food of animals, unless it has 

 previously undergone the influence of vegetable life. 



II. OF THE ELEMENTS OF BODIES. 



Another consideration, of equal importance with the former, is the con- 

 vertibility of all those substances so different from one another, and their 

 capacity of being reduced to a small number of simple substances, called 

 elements. The ancient doctrine of Aristotle, relative to the four elements, 

 still prevailed in the schools, with a few modifications, which it had re- 

 ceived from the chemists, when the " Pneumatistsf" demonstrated by 

 their beautiful experiments, that three, at least, of these pretended prin- 

 ciples of bodies, air, water, and earth, far from being simple substances, 

 were evidently formed by the union and combination of several others ; 

 that atmospherical air, for example, far from being an homogeneous fluid, 

 was composed of many different gazes, and that in its purest state, it con- 

 tains at least two very distinct principles, oxygen and azote; that water 

 Is a compound of oxygen and hydrogen, and that earth contains clay, 

 lime, silex. See. 



We have seen added in the present day, to the number of the elements 

 or simple substances, several which were not considered as such, at the 

 tim^when natural philosophers, misled by erroneous metaphysical doc- 

 trines, Uad created out of their imagination?, beings of the existence of 

 which they could find no proof. There is every reason to believe, that the 

 number of substances not admitting of decomposition, limited at present 

 to forty-four, ms,y hereafter be increased or diminished, by the discovery 

 of new principles \\\ simple substances, or of new elements in compound 

 bodies, which have hitherto eluded the investigation of chemists. What- 

 ever may be the success ^f their inquiries, of which it is impossible to 

 foresee the results, or to fix the limits, there is reason to believe, that it 



* MJBBEL, in his treatise on Vegetable Anftomy and Physiology, observes, " that 

 plants have the power of deriving 1 nourishment/from, inorganic matter, which is not the 

 case with animals, who feed on animals and vegetables, or on both; but are never nou- 

 rished on earths, salts and airs." Richerand las adopted the plausible opinion of Mir- 

 bel. Farther inquiry might, however, have shown them that earths and salts" furnish 

 as little direct nourishment to plants as to animals. Indeed it may be observed, that the 

 vegetable kingdom derives the chief part of its iood from dead animal and vegetable 

 matters which, although they contain both " earths and salts" cannot be either rank- 

 ed under these substances, or even classed with them. Copland. 



j This is the name given to the school of modern chemistry, because it originated 

 from the discoveries made relative to the nature of air and elastic fluids. It must be 

 acknowledged, to the credit of metaphysics, that the old errors were forsaken, only at 

 the period when chemists were thoroughly convinced of this truth, that every ide'a is 

 obtained through the medium of the senses, and that nothing is to be admitted* beyond 

 what they demonstrate in actual experiment. Authors Mtc, 



