DIFFERENCE OF SAME GROUPINGS. l8l 



greatly the decomposition of all organic sub- 

 stances used for fertilizers in agriculture. 







ISOMERIC BODIES. 



Isomeric bodies do not always manifest the 

 same peculiar properties. The oil of turpentine, 

 of 'lemon, and of roses, being analyzed, appear to 

 be composed of the same identical proportions ; 

 and yet they transmit different reactions through 

 the sensorial nerves. 



Chemists have tried to convert resin into butter 

 on isomeric principles ; " but the scent of the resin 

 will hang round it still." Similar attempts con- 

 tinue to be made to convert oils and fat into 

 butter. 



The reflection of colors from the surface of iso- 

 meric bodies appears to be remarkably uniform ; 

 as discovered by Graeby and Silberman, in- substi- 

 tuting the colors called "Aniline," derived from 

 coal-tar, for the coloring matter in madder, now 

 generally used for dyeing cloths red, purple, and 

 violet. 



Not only do different kinds of molecules reflect 

 vibrations of light with different intensity, corre- 

 sponding to a chromatic scale of colors, but also 

 peculiar dark lines, or markings (discovered by 

 Frauenh offer), on which is now based what is 

 called " Spectrum Analysis." This is the most 

 delicate known test for determining the kinds of 

 molecules contained in compound substances, and 



