390 PHOF. J. F. BLAKE ON THE M02s^lAN AND 



these fragments are of purple slate, such as the western part of the 

 series alone will yield. 



These considerations make it, I think, pretty certain that in going 

 from east to west we are passing over an ascending sequence. 'Not 

 is there the slightest trace of a synclinal, anticlinal, or any other 

 folding. There are disturbances here and there, but they have very 

 little effect, and are mostly confined to the eastern slopes. Except 

 for being compressed and hardened, they are very little altered, and 

 if there is any cleavage it must affect the slates only, and be there 

 confounded with the bedding ; only in one place, in Stony Batch, 

 did I observe an oblique cleavage. 



The distribution of the various groups on the surface is indicated 

 on the map. It is very possible that the lines of separation there 

 marked do not always indicate the same horizon in the series as they 

 should do, but the general tendency of all the rocks in one direction, 

 wherever their strike can be observed, and the remarkable scoring 

 of the hill-sides by the parallel crests of the harder strata, leave no 

 doubt that the whole is an ordinary sedimentary series, simply 

 turned up on end so as to dip at an average of about 80°, the lowest 

 dip being seen generally on the west, though it is seldom if ever 

 lower than G0°. This will give the series a total thickness of not less 

 than 3 miles. 



The careful lithological description given of the series by Salter 

 relieves me from the necessity of saying much on this point, which 

 is pretty familiar to geologists ; but there are one or two obser- 

 vations of importance. 



It is plain that the oldest member of the series in this locality is 

 not a basal deposit. Its uniformity, the fineness of its material, and 

 its calcareous bands, all give it great resemblance to the higher 

 Welsh Cambrians, and show it to be the product of very settled con- 

 ditions, and to represent the most tranquil portion of the period of 

 the general formation. It must in fact be the upper part of a series 

 whose lower part is not revealed within the district. It could not 

 possibly be derived from the washing down of such volcanic rocks 

 as are found on its eastern border, nor without many intermediate 

 siftings from any series of gneissic or granitic rocks. If therefore 

 these rocks be Monian, as I hope to show, they must belong to the 

 upper part of it. The gradual coming on of coarser rocks indicates 

 a rising of the area of deposition, with the denudation of new and 

 less distant masses. First we have the fine banding which indi- 

 cates perhaps a littoral condition of things, and then an alterna- 

 tion. The greywackes and grits are at first of a finer character, 

 with very little mica, but the upper parts of groups 4 and 5 are often 

 coarser and more micaceous, and they gradually put on a purple 

 hue, but are invariably well bedded. As we approach the top, this 

 last fact is about the only reliable character, and it is extremely 

 hard, if not impossible, to distinguish some hand specimens of the 

 hard grey wackc from the overlying grits. One well-marked band at 

 the top of Ashes Hollow is far coarser than these grits, and contains 

 abundance of small purple fragments, as though it had been derived 



