STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 65 



on the sandstones, is a seam of inferior coal, the " upper bed," which 

 is a pitch coal, containing much resin and little constitutional water. 

 The thick bed on Grey River, i6 feet, contains 64 to 68 per cent, of 

 fixed carbon, while another seam, on the coast, has but 38.55 per 

 cent. Hector described the latter as a very superior pitch coal, but 

 its chemical composition suggests cannel ; and it was recognized as 

 such by Campbell,^' who notes its variations in thickness. Within 

 its small area, he saw it 4, 6, 16, 4, and 2 feet. At the border, it 

 thins away to nothing. Cannel is the prevailing type in this bed. 

 Another bed, resembling splint, contains pebbles of sandstone. 



A more detailed study of the Buller Coal Field was made by 

 Cox and Denniston.^^ At Coalbrookdale in Waimangawa Basin, 

 Cox saw two coal seams, 5 and 18 feet thick, separated by 34 feet of 

 sandstone ; but at a short distance away they become 6 inches and 

 II feet 6 inches. The upper bed quickly disappears but the lower 

 one thickens northwardly until it becomes 40 feet, beyond which it 

 decreases. Still farther north, beginning at Mount Frederick in the 

 Ngakawau Basin, this lower seam is 5, 25, 37, 40 and, at center of 

 the basin, 53 feet ; thence it thins away in all directions, the last 

 measurement being 6 inches. Other beds show similar variations. 

 Southwardly from the Waimangawa Basin, the conditions are the 

 same. Descending a stream from Mount Williams, Cox saw an 

 outcrop of shale ; at a little distance beyond, this became a coal 

 seam, 3 feet thick, but worthless because of numerous shale bands. 

 Followed southwestwardly, this, the lower coal seam of other basins, 

 became 3, 8, 20, 40, 20, 20, and 25 feet. But southward from the 

 last measurement the seam thinned away until no trace of it could 

 be found. 



Denniston's descriptions and his numerous sections show the lens 

 form of the coal seams, thickest at center and thinning away to dis- 

 appearance toward the margins of the basins. He notes that coal 

 of the lower seam is not the same throughout a basin. In one area 

 the upper portion is tender but the lower is hard ; in another, the 

 prevailing type is splint or cannel, hard, compact, jetlike, burning 



IT W. D. Campbell, New Zealand Geol. Survey, Reps, for 1876-7, pp. 31-40. 

 18 S. H. Cox, N. Z. Geol. Survey, Reps, for 1874-6, pp. 17-29, 106-119; 

 R. Denniston, the same, pp. 121-171. 



