A Ramble in West Sitropihlrr. 351 



but I have not been so fortunate as to bit; on the exact spot. 

 Indeed, I recommend those who explore this region to be 

 moderate in their hopes of making a collection of fossils. 

 Some spots of extraordinary richness are occasionally found, 

 from which it is possible to carry off a profusion of capital 

 specimens in an excellent state of preservation ; but you may 

 examine many a dreary cubic yard, or, I might even say, cubic 

 mile of rock, without being repaid by a single fossil. A couple 

 of summers ago, I was applied to by a gentleman, who pro- 

 fessed to be an ardent collector, for some information as to 

 the best localities in which to look for fossils; and having 

 given him as accurate directions as I possibly could, he started 

 on a three days' tour through the district. But when he 

 returned, the whole of his spoils were contained in his waist- 

 coat-pocket. This may appear discouraging, but it must not 

 be supposed that all are equally unfortunate ; on the contrary, 

 some of my most satisfactory fossil-hunting clays have been 

 spent among the Llandeilo flags. I shall not attempt to enter 

 upon the large subject of the fossils to be obtained here, since, 

 to do it justice, it would be necessary to copy largely from 

 Sir R. Murchison's important work ; armed with which, no one 

 can be at a loss to ascertain and classify his spoils. Suffice it 

 to say, that they consist chiefly of tribolites of various kinds, 

 orthoceras, and lingulas, interspersed with a few bivalve shells. 

 The most interesting feature in the lithological character 

 of the rocks of this neighbourhood, is the occurrence among- 

 them of several layers of what Sir R. Murchison describes as 

 " felspathic aglomerates and ash beds, or volcanic grits, as well 

 as slaty porphyries, with crystals of felspar. Some of them 

 alternate in ridges with the schist containing tribolites, others 

 constitute courses of a few inches thick only, and occasionally 

 include fragments of Ogygia Buchii. Organic remains are also 

 found in beds composed almost exclusively of igneous mate- 

 rials, thus showing that volcanic action was rife at the sea 

 bottom in which these lower Silurian strata were accumulated." 

 And to account for these facts, that is, for the alternate layers 

 of shale and felspathic rock, he supposes that these gritty beds 

 were formed of the debris of submarine volcanoes. In recent 

 times such have occurred, of which Graham Island, in the 

 Mediterranean, is an instance. A cone of ashes and other 

 volcanic products is formed, and is pushed upwards to a con- 

 siderable height above the surface of the sea ; subsequently it 

 is attacked by the waves, and the scoriae of which it was com- 

 posed is spread out over the sea bottom. This in time is 

 covered by the deposit of mud which, under ordinary con- 

 ditions, is ever going on. A fresh eruption, and another 

 cone would supply a second layer of felspathic ash, and so on 



