202 HISTORY OF CHEMISTRY. 



like the Latin names of the ancient metals, aurum y 

 ferrum. This artifice is a convenient nomenclature 

 for the purpose of marking a recognized difference ; 

 and it would be worth the while of chemists to 

 agree to make it universal, by writing molybdenum 

 and platinum; which is sometimes done, but not 

 always. 



3. I am not now to attempt to determine how 

 far this class, Metals, extends; but when the 

 analogies of the class cease to hold, the nomencla- 

 ture must also change. Thus, some chemists, as 

 Dr. Thomson, have conceived that the base of Silica 

 is more analogous to Carbon and Boron, which 

 form acids with oxygen, than it is to the metals; 

 and he has accordingly associated this base with 

 these substances, and has given it the same termi- 

 nation, Silicon. But on the validity of this analogy 

 chemists appear not to be generally agreed. 



4. There is another class of bodies which have 

 attracted much notice among modern chemists, and 

 which have also been assimilated to each other in 

 the form of their names; the English writers calling 

 them Chlorine, Fluorine, Iodine, Bromine, while 

 the French use the terms Chlore, Phtore, lode, 

 Brome. We have already noticed the establish- 

 ment of the doctrine that muriatic acid is formed 

 of a base, chlorine, and of hydrogen, as a great 

 reform in the oxygen theory ; with regard to which 

 rival claims were advanced by Davy, and by MM. 

 Gay-Lussac and Thenard in 1809. Iodine, a re- 



t 



