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VII.—Notes on the Probable Origin of Some Slates

Published online by Cambridge University Press:  01 May 2009

W. Maynard Hutchings
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Extract

Mr. Sorby, in his Address as President of the Eoyal Microscopical Society in 1877, dwelt very forcibly on the interest and value attaching to researches into the original nature of the materials composing sedimentary deposits, and stated that, so far as he was aware, but little had been done in this direction by means of the microscope (Monthly Microscop. Journal, vol. xvii.).

Type
Original Articles
Information
Geological Magazine , Volume 7 , Issue 6 , June 1890 , pp. 264 - 273
Copyright
Copyright © Cambridge University Press 1890

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References

page 269 note 1 It should be understood that by tbe use of the word mica there is no intention to infer that anything sufficiently definite is ascertainable about the substance in question to enable it to be certainly referred to any recognized variety of mica. The word is used only to express the fact that the observable characters of the mineral, including such of its optic properties as can be ascertained, bring it into close resemblance to some of our known micas.

page 270 note 1 Among other material examined, I am indebted to Mr. G. II. Askew, of Aspatria, near Carlisle, for a series of specimens of the cores from a bore-hole put down at that place to prove the coal-seams. This series of clays, shales, and micaceous sandstones, extending to 800 feet in depth, proves to have been all derived, like the beds in the Newcastle coal-field, from the waste of a granite with two micas; and the changes undergone by the materials of the deposits have been the same.