In his interesting paper on “The Origin of Coal,” published in the Geological Magazine for January, 1901, p. 29, Mr. Strahan says: “the Limestone Series generally consists of repetitions of small groups of strata, each group being composed of sandstone, followed by shale, shale followed by limestone.” It is not stated whether this is intended to be an upward or downward succession; but if the former is meant, as it seems to be, the sequence is very different from that which exists in many parts of the country. Amongst the Yoredale Rocks proper—by which I mean the beds in the valley of the Yore and in such parts of the neighbourhood as contain rocks of a similar type—the usual upward succession is sandstone followed by limestone overlaid by shale. That is to say, the limestones very often have basement sandstones, and are nearly always immediately overlaid by shale. There are some cases in which limestone is overlaid by sandstone, but these are quite exceptional.