ODORS AND LIFE. 193 



concealed in matter make themselves known to us in a still 

 more remarkable phenomenon, to which the name of isom- 

 ery is given. Two bodies, thoroughly unlike as regards their 

 properties, may present absolutely the same chemical com- 

 position with respect to quality and quantity of elements. 

 " But in what do they differ ? " it may be asked. They differ 

 in the arrangement of their molecules. Coal and the dia- 

 mond are identical in substance. Common phosphorus and 

 amorphous phosphorus are one and the same in substance. 

 Now, the odorous principles of plants offer some exceedingly 

 curious cases of isomery. Thus the essence of turpentine, 

 the essence of lemon, that of bergamot, of neroli, of juniper, 

 of savin, of lavender, of cubebs, of pepper, and of gilly- 

 flower, are isomeric bodies, that is, they all have the same 

 chemical composition. Subjected to analysis, all these 

 products yield identical substances in identical proportions, 

 that is, for each molecule of essence, ten atoms of carbon, 

 and sixteen atoms of oxygen, as denoted by their common 

 formula, C 10 H 18 . We see how these facts as to isomery 

 prove that the qualities of bodies depend far more on 

 the arrangement and the inner movements of their minute 

 particles, never to be reached by our search, than on the 

 nature of their matter itself; and they show, too, how far 

 we still are from having penetrated to the first conditions 

 of the action and forces of substances. Among odoriferous 

 essences placed by chemists in the class of aldehydes may 

 be named those of mint, rue, bitter-almonds, anise, cummin, 

 fennel, cinnamon, etc. The rest are ranged in the great 

 series of ethers, which vary widely in complexity, notwith- 

 standing the simple uniformity of their primary elements. 



Such is the chemical nature of most of the odorous 

 principles of vegetable origin. But chemistry has not 

 stopped short with ascertaining the inmost composition of 

 these substances ; it has succeeded in reproducing quite a 

 number of them artificially, and the compounds thus manu- 



