442 MODEKN CHEMISTRY. 



instance more, and this rather from its whimsical nature, than 

 from any connection the substance is likely to have with the 

 uses or ornaments of life. Discovered a few years ago, as a 

 definite compound of arsenic, carbon, and hydrogen, it has 

 been called Kakodyle from its peculiar smell an odour so 

 intolerable, that even the chemist, inured as he is to vile and 

 noxious exhalations, seems to have shrunk back for a time 

 from the work of his own hands. Yet such was the interest 

 attached to this substance, as a compound organic radical, ful- 

 filling in composition the part of an elementary body, that 

 despite the quality just named, and the virulently poisonous 

 and inflammatory nature of its compounds, it has been 

 followed through all its combinations with consummate care ; 

 and no disgust or danger have checked a single experiment 

 which could illustrate the complex affinities of which it forms 

 a remarkable example. 



We have thus far been speaking of the general principles 

 of Chemistry, and of those new methods which have so 

 largely extended its dominion over the material world. In 

 doing this, we have sought illustration from some of the 

 many discoveries crowding the later periods of the science ; 

 to the most important of which we may now more explicitly 

 allude, in completion of the view of the actual state of 

 Chemistry which we are seeking to convey. 



We have already noticed that remarkable series of dis- 

 coveries illustrating the latter half of the 18th century; 

 the separation and definition of the gaseous bodies the 

 decomposition of water and atmospheric air the doctrines of 

 latent and specific heat the determination of the true nature 

 of oxides the principle of elective affinity, &c. To these 

 points, now so familiar, we shall not further advert than by 

 repeating that they gave foundation to Chemistry as a 

 science, and furnished instruments and guidance for the 



