CoaL 27 



layers are formed will be the subject of a 

 future chapter. 



From the position that the coal measures 

 occupy, being entirely under the Secondary 

 and Tertiary formations, it will be observed 

 that they are very old. If we should examine 

 a piece of ordinary bituminous coal we should 

 find that there are lines of cleavage in it paral- 

 lel to each other, and that it is an easy 

 matter to separate the lump on these lines. 

 If we examine the outcrop of a coal bed we 

 will find that these lines of cleavage are hori- 

 zontal. This indicates that the great bulk of 

 vegetable matter of which the coal formation 

 is made up has been subjected to tremendous 

 pressure during a long period of time. If we 

 further examine the structure of a body of 

 coal we find the impressions of limbs and 

 branches as well as the leaves of trees and 

 various kinds of plants. We shall further 

 find that these impressions lie in a plant in 

 the same direction as the line of cleavage. 

 This is a point to be remembered, as it helps 

 to explain the nature and structure of other 

 formations than those of coal. Not only are 

 leaves and branches of vegetable matter found, 

 but fossils of reptiles, such as live on the land. 

 Sometimes there is found the fossil of a great 

 tree trunk standing in an erect position, with 

 its roots running down into the rock below 

 the coal bed, while the trunk extends upward 



