Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/265

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1869.]
HULL—GEOLOGY OF CHESHIRE.
171

In constructing some of the railways of South America the granite was found to be so soft, from decomposition, that it could be cut with the pick and spade; and this softened granite, when washed, produced gold.

Prof. T. Rupert Jones considered that, by means of Dr. Sutherland's communication, the Laurentian and Silurian rocks were now, for the first time, to be recognized as existing beneath the Dicynodon-rocks of the Natal ridge.

February 10th, 1869.

Moreshwar A'tmáráni Tackhadakar, Esq., 3 St. George's Square, Primrose Hill, N.W., and Henry Spicer, Jun., Esq., 22, Highbury Crescent, N., were elected Fellows of the Society.

The following communications were read:—

1. On the Evidences of a Ridge of Lower Carboniferous Rocks crossing the Plain of Cheshire beneath the Trias, and forming the boundary between the Permian Rocks of the Lancashire Type on the North, and those of the Salopian Type on the South[1]. By Edward Hull, Esq. M.A., F.R.S., District Surveyor of the Geological Survey of Scotland.

It has generally been supposed that the Triassic plain of Cheshire, almost encircled as it is by coal-fields, is itself a great repository of coal-bearing strata having few or no interruptions to its continuity, except towards the southern margin, where the Triassic and Permian rocks, overlying at intervals thin and marginal representatives of the coal-measures, approach the Cambrian and Silurian districts of Shropshire. I myself for a long while held and defended this view; nor was I aware until recently that it had ever been controverted. I am informed, however, by Mr. Jukes, that in a discourse which he delivered before the British Association in Birmingham, "On the Position and Extent of Coal-measures beneath the Red Rocks of the Midland Counties," in 1865, he expressed his opinion of the probability of ridges or bosses of rocks older than the coal-measures underlying the Trias of the plain of Cheshire and Salop, and throwing the Upper Carboniferous beds into detached coal-fields. These views were illustrated by large diagrammatic sections; unfortunately no report of this lecture is published in the Transactions of the Association.

With my own mind fully imbued with the idea of a continuous sheet of coal-measures stretching beneath the New Red Marl from the southern margin of the Lancashire coal-field as far south, at least, as the Lias of Prees, near Whitchurch[2], I last winter (1867) was

  1. Communicated with the consent of the Director General.
  2. In this direction the old rocks which formed the original margin of the Carboniferous basin may be expected to occur in promontories projecting northwards under the Trias and Permian beds. (See Map, p. 183.)