152 WALKS AND TALKS. 



region. It has afforded an enormous quantity, and some of the 

 best varieties are said to be about worked out. 



The other varieties of coal are bituminous. That is, they 

 contain hydrocarbons partly of the nature of bitumen. But 

 the term as a designation for a variety is restricted to the black 

 coals occurring in the region east of the Rocky mountains, 

 chiefly in the Palaeozoic System. In structure they are dis- 

 tinctly stratified sometimes with films of earthy matter 

 between the laminae. They are apt to break in flattish or thin 

 fragments, and they possess an earthy or resinous luster. 

 They burn with much bright flame which arises from the 

 hydrocarbons expelled and ignited. These coals are the source 

 of the illuminating gas of our cities. 



From the typical bituminous coals we may separate the 

 Cannd Coals. These have an earthy luster, a fine compact 

 constitution, and are often thick bedded, with only obscure 

 stratification within the bed. They burn freely and brightly 

 when rich, and were used in the earliest manufacture of 

 illuminating gas and kerosene, or "coal oil." This manu- 

 facture had attained a prosperous stage of development when 

 the discovery of the large supplies of petroleum caused its 

 ruin. Cannel coal has no standard degree of purity. It 

 consists of carbonaceous and aluminous particles mixed in 

 varying proportions. It degenerates, on one hand, to a mere 

 black shale, and on the other, attains a state in which it is 

 almost free from earthy admixture. 



Among the typical bituminous coals, we distinguish the 

 caldng and the non-caking. The former when ignited, seem to 

 fry with an exudation of a fluid bitumen, which evolves much 

 gas and hardens into a crust somewhat impervious to the air, 

 and thus obstructing the draft. The latter burn freely, with- 

 out an incrustation. 



Besides the Paleozoic bituminous coals we find excellent 

 Mesozoic bituminous coals. These are solid, but less valuable 

 than the others ; though they are a boon to many regions 

 otherwise scantily supplied with fuel. Of this kind is the coal 

 mined near Richmond, Virginia, and in the Deep river 



