149 



known instances of their storage in marsh turf and in coal scams indicates that there should 

 he no difficulty in assuming their presence and continual accumulation in the lignite beds. 

 With the denudation of the general area, and the exposure of fresh bodies of lignite at various 

 times, possibly at intervals of a few years, or again with intervals of centuries, the escaping 

 gases would ignite and give rise to all the observed phenomena. While, therefore, it must 

 be conceded that some of these conflagratiors have undoubtedly had their origin in prairie 

 fires or through the agency of man, others, and possibly most of them, have been due to the 

 spontaneous ignition of escaping gases. 



If, upon further investigation, this explanation is found to be satisfactory, it may also be 

 possible to apply it to those Tertiary beds in British Columbia and other western areas 

 where we find metamorphosed clays and standstones containing charred fragments of plants, 

 the majority of which are wholly unrecognizable. 



An application of these facts appears to be essential to a complete understanding of the 

 conditions under which the Tertiary beds of British Columbia appear today, since there is 

 reason to believe that the very remarkable changes in position, and the metamorphosis of the 

 materials of these strata, have been brought about by volcanic activity supplemented by com- 

 bustion of the lignite beds. How far one or the other of these causes has operated within 

 given areas it is at present impossible to say, but a solution of this question is essential to a 

 clear understanding of the sequence of strata and their fioras, in a region where both the 

 Cretaceous and Tertiary formations have undergone a remarkable readjustment incident to 

 the elevation of the Rocky Mountain chain, involving in some cases an apparent mixture of 

 the beds. The final explanation can be reached, in our opinion, only through an exact 

 stratigraphical study of the floras and the rocks in which they are held. It will be profita- 

 ble, however, to review some of the opinions already expressed, and the facts derived from 

 actual field work, as bearing upon this question. 



In 1875, Dr. Selwyn made the following observations^ ; — 



" The local development of volcanic rocks leaves the question open as to whether they have 

 been removed by denudation, or to their never having extended over the entire region. The 

 Lignite Tertiary strata, however, which at present are assumed to have preceded the latest 

 of these volcanic outbursts, occupy undefined but certainly extensive areas between Fort George 

 and McLeod lake, and probably continue thence to the valley of Nation river, with only such 

 interruptions as are the result, partially of the original uneveness of the surface upon which 

 they w^ere laid down, and partly of the subsequent denuding agencies to which they have 

 been subjected, giving rise to outcroppings of the older rocks either as hills or ridges rising 

 above the general level of the country, or appearing as rocky bars or canyons in the deep cut 

 channels of rivers." 



In 1876 Dr. G. M. Dawson^ states that, " On the south side of Tsacha lake, there are 

 numerous fragments of shaly. Tertiary clays, some with obscure plant impressions, leading to 

 the inference that the basalts of the region were cut through in its bed. 



" Underlying the basalts are deposits of arenaceous clays, volcanic mud and pumice, 

 together with diatomaceous clays, and in this formation there are grains of coniferous pollen. 

 There is thus an interlocking of ordinary sedimentary and volcanic Tertiary products. 



1 Geol. Siirv. Can.. 1875-7C, 71-72. 



2 Geol. Surv. Can., 1876-77. 75-80. 



