^0. 5.] DAWSON — LIGNITE FORMATIONS. 251 



horizontal attitude cuid easy accessibility, and could probably bo 

 mined by a system similar to that known as long wall, at the 

 expense of a comparatively small amount of mine timber, which 

 in these woodless regions would be a great advantage. The 

 iron-stones, though occurring frequently in proximity to the 

 coals, have not yet been observed in workable quantity, but it 

 is highly probable that further explorations may bring such 

 localities to light. The ores are among the best of their kind, 

 both as to percentage of iron and freedom from sulphur and 

 phosphorus. None of the lignites yet discovered yield however 

 a coherent coke suitable for the smelting of iron in the blast 

 furnace.* 



The conditions implied by the nature of these deposits are 

 marshes, lakes and estuaries, on a grand scale, and from which 

 the sea was for the greater part of the time excluded. The 

 previous deposits of Cretaceous age show that at that time the 

 ■whole western part of the continent was covered by a sea of 

 some depth, in which during a long time before the advent of 

 the lignite period, fine silty and muddy sediments were laid 

 slowly down, and included the remains of Cephalojwda and 

 LamelUhrnncldata peculiar to that age. Then came on a period 

 ■of emergence, coarser sediments were carried by the waters, and 

 at last the sea was entirely shut oiF from the area in question 

 and replaced by great lakes of fresh water, with wide swampy 

 margins, where the lignites were slowly formed by the growth ol 

 trees and peaty moss. 



Much (juestion has lately arisen with regard to the true age 

 of the representatives of these deposits in the Western States. 

 The plants as compared with those of European formations, have 

 a comparatively modern aspect, and were originally referred on 

 good authority to the Miocene. The molluscous fossils occur- 

 ring in marine beds connected with the base of the formation on 

 its western margin, show Cretaceous affinities. Cope maintains 

 that the Cretaceous age of the greater part, if not the whole of 

 the formation, is proved by the existence in it of a few relics of 

 Dinosaurian reptiles. It would seem indeed that in the regular 

 passage of beds of well marked Cretaceous age upwards into the 

 Lignite Tertiary formation, we have a case of the blending of 



* Mr. MilU-r, in some remarks made after the reading of tlii« paper, 

 mentioned the successful emphiynient of charcoal made from similar 

 lignites in Uermauy, in iron Buielting. 



