ORGANIC COMPOUNDS. 283 



in all its transmutations, an obedience to a most har- 

 monious system is apparent. 



It is curious to observe the remarkable character 

 of many of these natural transmutations of matter, but 

 we must content ourselves with a few examples only. 

 For instance : 



Sugar, oxalic acid, and citric acid are very unlike 

 each other, yet they are composed of the same elements ; 

 the first is used as a general condiment, the second is a 

 destructive poison, and the third a grateful and healthful 

 acid : sugar is readily converted into oxalic acid, and in 

 the process of ripening fruits nature herself converts 

 citric acid into sugar. Again, starch, sugar, and gum 

 would scarcely be regarded as alike, yet their only diffe- 

 rence is in the mode in which carbon, hydrogen, and 

 oxygen combine. They are composed of the same prin- 

 ciples, in the following proportions : 



Carbon. Hydrogen. Oxygen. 

 Starch . . . 12 10 10 

 Sugar . . . 12 11 11 

 Gum . . . 12 11 11 



These isomeric groups certainly indicate some law 

 of affinity which science has not yet discovered. 

 Similar and even more remarkable instances might be 

 adduced of the same elements producing compounds 

 very unlike each other; but the above have been 

 selected from their well-known characters. Indeed, we 

 may state with truth that all the varieties of the vege- 

 table world their woody fibre their acid or alkaline 

 juices the various exudations of plants their flowers, 

 fruit, and seeds, and the numerous products which, by 

 art, they are made to yield for the uses of man, are, all 

 of them, compounds of these three elements, differing 

 only in the proportions in which they are combined 

 with nitrogen, or in some peculiar change of state in 



