I.—A Faulted Slate

Extract

It is well known that the slates of the Borrowdale series in the Lake District furnish beautiful illustrations of faulting on a small scale; but so far as I am aware, no description of them, from this point of view, has as yet appeared. The accompanying Plate has been produced in Autotype from one of these slates, the surface of which was first most carefully smoothed and afterwards varnished. Every detail of the faulting is shown in the most perfect manner, and the general tint of the slate is also reproduced. The specimen was purchased at the village of Rosthwaite in Borrowdale; but I was not able to learn the exact locality from which it was obtained. I have little doubt, however, that it came from the Honister quarries. Mr. De Rance tells me that similar slates occur at Tilberthwaite, near Coniston. The plate is of the natural size. The face represented is a cleavage plane, and neither the bedding nor the fault planes are at right angles to this face. The bedding planes make with it an angle of about 40°.