350 



ORGANIC CHEMISTRY. 



riety as produced by varied arrangement. The new 

 substances are, as it were, different patterns, woven 

 from the same colored threads. The gases, of which 

 carbonic acid, light and heavy carburetted hydrogen 

 are the principal, have been already described. Wood 

 vinegar and wood tar form the subjects of subsequent 

 paragraphs. An excess of carbon remains behind as 

 charcoal. The process is called dry distillation. The 

 decomposition may be illustrated with saw-dust, in a 

 test tube, as previously described. 



879. SIMILAR CHANGE IN NATURE PEAT. 



Mention a si- . 



milar change Peat is formed by the decay of vegeta- 

 tn nature. j } j e matter un( } er wa ter. The green slime 



which forms, in the summer, upon stagnant water, is 

 composed of minute plants. These die, each season, 

 and sink to the bottom, until, in the course of years or 

 ages, vast accumulations of vegetable matter are the 

 result. By their partial decay or putrefaction under 

 water, they are converted into peat. The process is 

 analogous to that of dry distillation, and the products 

 similar. Carbonic acid and carburetted hydrogen gases 

 are evolved, while a solid residue of peat remains be- 

 hind. It may be regarded as a half-formed charcoal. 

 Peat contains, in addition to its carbon, a little hydro- 

 gen and a still smaller proportion of oxygen. The 

 carbonic acid evolved in the above process, often makes 

 its way to the surface, at some neighboring locality, 

 in the form of mineral springs. 



880. BITUMINOUS COAL. The formation 



How is bitutm- . , . , . 



nous coal 01 bituminous and anthracite coal is a con- 

 formed? sequence of a similar decay of vast accu- 



