THE
QUARTERLY JOURNAL
OF
THE GEOLOGICAL SOCIETY OF LONDON.
PROCEEDINGS
OF
THE GEOLOGICAL SOCIETY.
June 22, 1870.
Horace Pearce, Esq., 21 Hogley Boad, Stourbridge, and Samuel Spruce, Esq., of Tamworth, were elected Fellows of the Society.
The following communications were read : —
1 . Notes on the Lower portion of the Green Slates and Porphyries of the Lake-district between Ulleswater and Keswick. By Henry Alleyne Nicholson, M.D., D.Sc, M.A., F.R.S.E., F.G.S., &c, Lecturer on Natural History in the Medical School of Edinburgh.
Overlying the Skiddaw slates of the Lake-district and underlying the Coniston limestone is a great series of rocks which are mostly of igneous origin, and were originally named by Prof. Sedgwick the " Green Slates and Porphyries." These rocks consist essentially of stratified felspathic ashes associated with sheets of contemporaneous trap. The ash-beds are mostly cleaved, and they constitute the well-known " green slates " of Cumberland and Westmoreland, whilst the traps are often porphyritic. The origin, therefore, of the name proposed by Prof. Sedgwick is obvious ; but there are many reasons why some local name would be preferable. Near the summit of the group is a band containing Caradoc fossils, so that the age of this portion of the series is unequivocal ; but no organic remains have ever been detected as yet in the lower portion of the green slates, so that the exact age of this is somewhat uncertain. The entire series of the green slates and porphyries is exhibited over a very extensive superficial area, comprising the central portion of the Lake-district proper, and extending about twenty-five miles along the strike, from E.N.E. to W.S.W., and about thirteen miles in the direction of the dip, from N.N.W. to S.S.E. So much repetition, however, takes place, in consequence of folding and of faults, that it is very questionable if the entire
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