STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 99 



of vegetable matter undergoing a chemical change which differ in 

 composition according to the extent of that change, according to the 

 nature of material and according to the conditions under which the 

 change was made. Many matters have to be considered ; if these 

 be ignored, the comparison is worthless. 



All writers on peat deposits have called attention to the fact 

 that a notable physical change is observable as one follows the peat 

 downward from the surface, the disintegration of vegetable matter 

 increasing so that in the great mass of the mature peat, little trace of 

 organic matter can be recognized by the unaided eye, while in many 

 respects the lower portion bears much resemblance to brown coal. 

 The specific gravity increases with this change. Mills and Rowan^*^ 

 state that young Hanoverian peat has the gravity of 0.113 to 0.263, 

 whereas that of the maturer peat is from 0.639 to 1.039. The 

 chemical change is gradual but more and more marked with increase 

 of depth. Cornet^'** has given three illustrative analyses as follow : 



The ultimate composition is calculated ash and water free. The 

 extraordinary increase of nitrogen in the lowest portion may be 

 dvie in part to the presence of some plankton materials. Jentzsch^*^ 

 says that in the province of Preuss, the peat deposits vary in thick- 

 ness from a few inches to 17 meters. The composition of a peat 

 used for fuel is, water free: Carbon, 56.90; hydrogen, 5.54; oxygen, 

 31.88; ash, 5.66. In his later publication he compares peat from 

 several localities in the same province, thus : 



1*3 E. J. Mills and F. J. Rowan, " Fuel and its Applications," 1889, p. 18. 



1^* J. Cornet, " La formation des Charbons et des petroles," Extrait de 

 I'ouvrage, Geologie, T. III., p. 25. 



1*5 A. Jentzsch, "Die geognostische Durchforschung der Provinz Preus- 

 sen im Jahre 1876," Schrift. k. Phys. Okon. Gesell. Konigsberg, Jahrg. 17, 

 1877, pp. 120, 122 ; " Ueber die Moore der Provinz Preussen," the same, Jahrg. 

 19, 1878, .pp. 128-131. 



