146 



salient features of the data in order to ascertain, if possible, (1) the probable causes of such 

 fires: and (2) the. probable connexion between conflagrations of this kind and certain meta- 

 morphosed, plant-bearing rocks of Tertiary age, to be met with in various parts of British 

 Columbia, as well as in the eastern lignite area. 



The Bad Lands of the Upper Missouri and its tributaries owe their very remarkable 

 character and extremely interesting features to the presence of highly metamorphosed clays 

 and sands, accompanied by pumiceous and lava-like materials, undistinguishable in character 

 from true volcanic products, but occurring over an extensive area, remote from any region of 

 true volcanic action. This metamorphosis is solely the result of the burning out of beds of 

 lignite co-extensive with the Bad Lauds of the Lignite Tertiary. 



This formation extends, in the United States, from near the 100th to about the 108th 

 meridian, and from the 43d to beyond the 49th parallel, or over an area of about 500 miles 

 in an east and west direction, and more than 30 miles north and south. Its southern border 

 is quite irregular, being broken into by the Black hills, between which and the Big Horn 

 mountains it extends southward as far as the 43d parallel. An outlying district west of the 

 main chain of the Rocky mountains, on the Gros Ventres fork of the Snake river, is also 

 referred to. At the time of these observations, although the extension of the Lignite Tertiary 

 into the valleys of the Saskatchewan and Mackenzie rivers was well known, there were no 

 data at hand which would permit of tracing the phenomena of metamorphism much to the 

 northward of the Missouri river. But the results reached by Dawsoni^ would seem to indicate 

 that to the 185,500 square miles of territory in the United States, there must be added at 

 least 53,000 square miles for Canada, making a total of 238,500 square miles occupied by the 

 Lignite Tertiary formation. Within this area the lignite occurs in beds from a few inches to 

 eighteen feet in thickness, and the quality varies from a mere carbonaceous shale to a texture 

 BO compact and dense as to present the general appearance of cannel coal. 



The lignite seams are overlaid by beds of sand or clay containing recognizable remains 

 of plants, often in a very beautiful state of preservation, and some of these have been 

 accurately figured by Sir John Richardson in his report for 1851. There are also alternating 

 metamorphosed beds of greyish cinders, pumiceous matter, clinkers and indurated clay of a 

 bright brick red colour, varying in thickness from a few feet to twenty or more. The yield- 

 ing nature of the horizontal strata has permitted the material to be excavated by streams, 

 and the entire country is traversed by deep channels and numerous gullies, varying in depth 

 from one hundred to three or four hundred feet, and so extensive that only narrow ridges and 

 isolated buttes, with their naked and almost vertical slopes, are left to indicate the former 

 general level. Dawson observes that^ ; " in no part of the world does the destruction of 

 mineral fuels seem to have occurred on so vast a scale as in the central plateau of this conti- 

 nent. The appearances produced by this action were found in almost all localities in which 

 lignite occurred" ; and from the data given by both Allen and Dawson the metamorphosed 

 area would seem to embrace no less than 8,000 square miles. The alteration extends much 

 farther above the position of the lignite beds than below it. The layers immediately above 

 the lignite are frequently altered to hard, jaspery or porcelain-like rock breaking with a 

 conchoidal fracture, and in this substance impressions of stems and leaves of plants are some- 

 times recognizable. 



1 Brit. N. A. Bound. Comm., p. 152. 



2 Brit. N.A. Bound. Comm., p. 164. 



