Reviews — Western Australian Geology. 477 



VI. — On the Splitting of Coal Seams by Pauxings of Dikt. 



Part I : Splits that IIejoin. By P. F. Kendall. Trans. Inst. 



Min. Eng., vol. liv, p. 460, 1918. 

 rilHE explanation of the splitting of coal-seams that has so long 

 1 done duty in text-books is unsatisfactory and often inapplicable 

 to actual instances, since it is frequently found that the upper 

 portion of the split seam is convex upwai'ds while the lower portion 

 is horizontal. , Professor Kendall has made a careful study of split 

 seams in the Yorkshire coal-field, especially in the Silkstone or 

 Middleton Main and Haigh Moor seams at Whitwood, Ackton Hall, 

 Methley, and South Kirkb)'. The explanation put forward depends 

 on the well-known fact that peat on conversion to coal undergoes 

 a very great reduction in volume, here estimated at 20 to 1. 

 A trough-like wash-out in a bed of peat, filled with sand or mud, 

 would be much less compressed than the peat; the whole mass 

 would settle down in a ridge-like form with a thin layer of coal 

 above and below the sandstone or shale, the form of the mass thus 

 undergoing inversion in cross-section. 



By mapping the known position of the edges of split seams it has 

 been found possible to trace out the courses of Carboniferous rivers 

 over distances of several miles, and the method of investigation 

 pursued seems likely to lead to results of great practical and 

 scientific interest. 



li. H. E. 



VII. — Some Problems op Western Australian Geology. Presidential 

 Address to the Royal Society of Western Australia, delivered on 

 July 11, 1916, by A. Gibb Maitland, F.G.S. pp. 34, with 

 38 figures. Perth, 1917. 



IN this presidential address the author deals chiefly with the 

 NuUagine formation. This series of rocks has a very wide 

 distribution in the state, and is composed chiefly of sandstones, 

 quartzites, conglomerates, dolomitic limestones and igneous rocks, 

 dolerite dykes and sills, with lavas and ashes at one horizon. 

 The series, the lower members of which are gold-bearing, rests 

 with a very marked unconformity on the underlying rocks, which are 

 everywhere metamorphosed and of pre-Cambrian age. The sequence 

 begins with a basal con<>lomerate, which is followed bj' an outbreak 

 of lavas and ashes, cliiefly andesitic, but in places rhyolitic, which 

 appear to have been produced by fissure eruptions, as few volcanic 

 foci have been discovered. These rocks are followed bj' dolomitic 

 limestones, which are in turn overlaid by a sandy series with 

 haematite and magnetite, bearing quartzites or jaspers, having some- 

 times as much as 37 per cent of iron. The ferruginous bands are 

 thin and interbedded with light-coloured quartzites, so that a banded 

 rock is produced. 



The dolerite sills are of very uniform composition and do not 

 seem to have undergone much metamorpliism since their intrusion ; 

 they are accompanied in the more disturbed areas by quartz reefs 

 with gold and copper. The reservoir which supplied this igneous 

 material seems to have been situated about latitude 26° S. There 



