Coal. 25 



there will be if left to the sun's rays alone. 

 During the carboniferous age the earth was a 

 great hotbed. 



The fossils of trees and plants, as well as 

 reptiles, that we find in the great coal measures 

 of the world, show that they were of large 

 tropical growth, and this is shown not only in 

 the temperate zone, but in the zone farther 

 north. For ages and ages this rank growth of 

 vegetation grew up and fell down until a great 

 layer of vegetable matter was formed, which at 

 a later time was covered over by other strati- 

 fications of earth material, so that these great 

 layers of vegetable formation were hermeti- 

 cally sealed and pressed down by an enormous 

 weight that increased as time went on. The 

 formation of coal may be studied even at this 

 day (for it is now going on) by visiting and 

 examining the great peat beds that are found 

 in various parts of the world. It is well 

 known that peat is used as a fuel by many 

 people, especially the peasantry of the old 

 countries. If peat is pressed to a sufficient 

 degree of hardness it burns in a manner not 

 unlike some forms of coal. Peat is a vege- 

 table formation and has been formed by the 

 rank growth of various kinds of vegetation in 

 swampy places. Of course, it lacks the purity 

 of the coal that was formed during the car- 

 boniferous age, because of the much slower 

 growth of vegetation now than during that 



