Clifton College Scientific Society. ' 59 



rapidly to the south, the amount of dip being about four inches 

 in the yard, till, at Navigation Colliery (near Quaker's Yard), about 

 six miles south of Merthyr Tydvi), they are several hundred feet 

 below the surface. Indeed, after this spot, they run to such a 

 depth that they are perfectly unworkable, and would be lost for 

 ever, but that, luckily for commerce, an ' anticlinal ' throws them 

 up again. They then dip again to the south, and rise to their 

 southern outcrop near Walnut- Tree Bridge, only seven miles north 

 of Cardiff. Thus, in their course from north to south, they de- 

 scribe two synclinals and one anticlinal. They also occur in the 

 Rhoudda Valley. 



Let us first glance at the general configuration of this coal-field. 

 In order to do so we ought to see what difierent formations occur 

 in its neighbourhood. The coal-measures (as seen by the Ordi- 

 nance map *) occupy the greater part of the county of Glamorgan, 

 all the other formations lying in patches round it. We have 

 nothing newer here than the lower secondary (except alluvium, 

 newer pliocene, or post-tertiary formations), consisting of lower 

 lias, rhcetic-beds, keuper, dolomitic limestone, and conglomerate. 

 The last three mentioned are triassic formations. Of the primary 

 formations we have a good collection, comprising the coal-mea- 

 sures and millstone-grit, carboniferous limestone and shale (lower 

 carboniferous), old red sandstone and cornstone (upper Devonian), 

 Ludlow rocks, Wenlock limestone and shale (upper Silurian). We 

 thus see that the coal-measures are by far the largest formation 

 in this district, lying to the north and surrounded on the south by 

 patches of lower secondary or primary formations. This coal-field 

 is composed of lofty hills, whose average height above the level of 

 the sea is 1000 feet, though some (as Garnfach, a mountain south 

 of Hirwain and Twmbarlon, one mile east of Eisca, and the 

 Garths, near Walnut-Tree Bridge) rise to a much gi'eater height. 

 Therefore, but for means provided by the all-wise Creator, the 

 priceless stores of treasures buried in these hills would be almost 

 useless to man, or, at any rate, to the poorer classes, from the 

 difliculty. of carrying them to the market and their consequent 

 dearness, were it not that a means has been found by Him who 

 does all things well, through which the carriage of the coal is not 

 only made j^racticable, but absolutely easy, not only to Wales, but 

 to all parts of Great Britain and the world. A series of valleys 

 intersect the hills in every direction, up which innumerable lines 

 of railway run, so that there is not a colliery in South Wales 

 which cannot send its coal or minerals straight from the pit's 

 mouth to any part of the kingdom by rail. The principal valleys 



* The lecturer exhibited numerous maps and diagrams in illustration of his 

 paper. 



