58 



CHAPTER II, 



CARBON — NITROGEN — SULPHUR — CHLORINE — 

 PHOSPHORUS. 



86. We now come to the consideration of an ele- 

 mentary or simple substance, which has been already 

 more than once alluded to, namely, carbon or charcoal. 

 Carbon is the name applied to the pure element, but 

 common charcoal is so nearly pure, that we may con- 

 sider the two words as meaning the same thing ; it is 

 an essential part of all kinds of fuel or combustible 

 substances, during the burning of which it combines 

 with oxygen, and forms carbonic acid gas, the sub- 

 stance before adverted to as always existing in the 

 atmosphere (37). 



87. The forms of carbon which we are accustomed 

 to see, are almost all black, like common charcoal; 

 but this is not the case with all the varieties of car- 

 bon, for we know that the brilliant transparent gem 

 called the diamond, is really pure carbon, there being 

 no chemical difference between that gem and common 

 charcoal. 



88. There are many substances in Nature which 

 exist in two or more different states, presenting very 

 dissimilar appearances, but being really chemically 



