54 THE CHICAGO ACADEMY OF SCIENCES. 



made for buildings, quarries, etc., and along the lake shore. It 

 differs from true coal inasmuch as it lacks homogeneity and 

 has a greater part of its vegetable fibers but partially altered. 

 When changed by pressure, it loses a part of its more volatile 

 constituents, becomes more thoroughly consolidated and homo- 

 geneous, and passes into lignite. Peat is without crystal struc- 

 ture, retaining, as it does, the original cell structure. It is 

 somewhat brittle, has a hardness of from 0.5 to 2, and a specific 

 gravity of from I to 1.8. It is brown in color and opaque. 



