Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/238

 of the rocks that I have seen intersected, with some additional localities.

The induration which the secondary rocks undergo when traversed by dykes has often been noticed; it is not my intention now to discuss this subject; I shall only mention that the induration does not extend far from the dyke, and that the phenomena though very frequent are not universal. I have only noticed one instance of remarkable change in a primitive rock contiguous to a dyke. In the case I allude to, viz. in the lead mine of Kildrim in the county of Donegal, mica slate adjacent to the dyke had its texture quite loosened, and was in a dusty state.