STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 105 



It is wholly certain that the paraffins are present and that one 

 is not compelled to go outside of the original plants to find a source 

 for these or for the resins. The abundance of conifers leaves no 

 doubt as to one source of the resins and waxes and these are char- 

 acteristic of swamp plants. They are alike resistant to chemical 

 change. The mode of occurrence of the New Zealand Kauri gum 

 afifords the necessary illustration for the resins. Penrose^^^ states 

 that this gum, a true resin, is a secretion of the Agatha australis, 

 now living within an extensive area in New Zealand. The resin 

 accumulates in large quantity on all parts of the tree and the 

 bark, which peels off and is heaped on the ground, is saturated with 

 it. The fresh exudations are unimportant commercially and the 

 supply is obtained from the buried or " fossil " gum. This is found 

 in regions now covered by the Kauri tree, in others whence the trees 

 have been removed as well as in some where the only evidence of 

 former forests is the presence of buried roots and other portions 

 of the trees. At times, the Kauri forests have disappeared and 

 have been replaced by those of other trees, the only proof of a 

 former forest being the gum and the roots. That the antiquity of 

 early Kauri forests is very great appears certain, for there are trees 

 in the newer forests, which are supposed to be not less than i,ooo 

 years old. At some localities, the gum is found in successive layers, 

 separated by clays or sands, evidence of forests destroyed one after 

 the other. The Senegal copal occurs vnider similar conditions. In 

 many cases the resin-filled portions of the trees have been preserved, 

 though all others have disappeared. 



Distillation Products from Peat. — Lampadius published in 1839 

 the results of his investigation of products obtained from peat by 

 distillation at and above the " cracking point." The experiments 

 have been repeated many times and with similar general results. 

 Two recent studies will suffice here. The Ziegler^^^ process of 

 producing coke from peat with saving of the by-products, has been 

 tested on a commercial scale at some places in Germany. About 33 



1"'^ R. A. F. Penrose, Jr., " Kauri Gum Mining in New Zealand," Jotirn. 

 of Gcol.y Vol. XX., 1912, pp. 38-44. 



i^s C. A. Davis, " The Uses of Peat," U. S. Bureau of Mines, Bull. 16, 

 191 1, pp. 128-142. 



