^{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.