SOLIDIFIED SUNLIGHT. 153 



region of North Carolina ; also the excellent coal of Wyoming 

 Territory, and that of similar excellence in Washington Terri- 

 tory, in the Cascade mountains. The latter exists in great 

 abundance and of several varieties, one of which has the ap- 

 pearance of anthracite. It is widely exported to San Fran- 

 cisco and the Hawaiian islands. 



Brown Coal is of Csenozoic age. It is next in order of 

 hardness and value. It varies, however, from a variety quite 

 firm and compact, with a blackish color, to varieties of brown 

 color and composed distinctly of vegetable fragments. 



Peat is a vegetable accumulation formed at the present 

 surface, from mosses, leaves, and sticks, and is not yet consoli- 

 dated into the condition of a coal. It is used, however, 

 extensively as a fuel, especially on the continent of Europe, 

 where the traveler may see it cut out in blocks and piled up 

 like bricks drying in the sun. The city of Paris is warmed 

 chiefly by peat. Many efforts have been made in America to 

 reduce peat to a cheap and efficient fuel ; but for the present, 

 it is unable to compete with our other natural combustibles. 



Coal occurs in strata not in veins interbedded with sedi- 

 mentary rocks. Shales, clays, and sandstones exist extensively 

 in Coal Measures ; and in some regions, limestones are inter- 

 stratified. The latter contain fossil shells, and are manifestly 

 of marine origin. The coal must have been produced on the 

 land. Some of the .clays are apparently the soil in which 

 the vegetation grew, since the roots are found extending into 

 them. The shales were deposited in quiet, muddy waters, 

 within easy reach of the products of the land, since they con- 

 tain immense quantities of fronds and other vegetable matters, 

 generally in a fine state of preservation. 



In regions somewhat disturbed, like Pennsylvania, the 

 strata of coal make outcrops like limestones, shales, and sand- 

 stones. Mining is then prosecuted from the "crop" by 

 carrying an excavation or drift along the slope of the coal 

 stratum. If possible, the place is so selected that the slope 

 may ascend from the mouth, so that the water reached may 

 flow out spontaneously. If this is not practicable, then pump- 



