S. V. Wood,jun. — American and British Surface- Geology. 21 



Glacial clay of pure raorainic origin to clay presenting the aspect 

 of having been due to marine deposit only, when the submergence 

 was great enough to cover the Wold near Flamborough to eleva- 

 tions of more than 400 feet, rather favours such a view ; and I have 

 long contended that this difference in the mollusca arises from the 

 Lancashire and other northern clays of Glacial age having been 

 formed at the close of the Glacial period, when the Crag-like fauna 

 of the East Anglian Glacial beds had changed into that purely 

 recent and Europeo-Arctic one which occurs in these clays, and in 

 the Moel Tryfaen bed ; up to which time the ice prevented the 

 accumulation of any deposit in that part of Britain. 



The description given by Mr. Ward of the mounds of stratified 

 sand and gravel in the Lake-country, which he refers to the period 

 of submergence, so precisely corresponds with the Kame drift of 

 the Scotch Highlands, that I think they must belong to the same 

 class of Glacial phenomena, and not be deposits of the period of 

 submergence at all. Indeed, if we consider that wherever the 

 marine sands of the submergence period lay in the way of the 

 glaciers of the second glaciation, they must have been ploughed 

 out and destroyed, we need not wonder that the instances which 

 have occurred of the sands and gravels of this period, such as those 

 at Moel Tryfaen and near Macclesfield, should be so rare as they 

 are, though they are sufficient to prove the great depth of the Glacial 

 depression in those parts of England.^ These mounds, Mr. Ward 

 says, are, at whatever elevation they occur, topped with erratic 

 blocks ; and he deduces from this circumstance the inference that 

 the period of the gravels was a mild one, and was followed by a 

 colder, in which these blocks were scattered over them. Precisely 

 the same feature is, however, exhibited by the Scotch Highland 

 Kames, and the explanation of it which I adopt is different from 

 that of Mr. Ward, and is that as the washing out of the subglacial 

 moraine into gravel took place by the melting back of this non- 

 confluent glacier-ice subaerially, the moraine of blocks which travelled 

 on the surface of the glacier fell from its termination on to the 

 surface of the gravel-heap thus produced. 



Be this, however, as it may, we appear to have in the mountain 

 districts of both England and Scotland precisely such a period of 

 minor or nonconfluent glaciation as that to which Mr. Rome and 

 I first, in 1867, and I in several papers subsequently (especially in 

 one with some detail of circumstances which appeared in the Geol. 

 Mag. for April, 1872), drew attention as explaining the origin of 



1 It is not, indeed, unlikely tliat the polished and broken fragments of shells which 

 occur in the gravels of some of the Welsh valleys, such as that of St. Asaph (some 

 of which were sent me by Prof. Hughes), and even those in the Upper Boulder-clay 

 and Middle Gravel of the North-western counties, of which several small collections 

 from Cheshire and, Lancashire have passed through my hands, got into these gravels 

 and clays of the Hessle period in this way ; and the same remark applies to the 

 Caithness clay, the shells of which are promiscuously scattered through its mass, and 

 are of a far less Arctic character than those of Elie and Errol. The glacier which 

 during the minor glaciation filled the great valley of the Caledonian Canal probably 

 at its commencement ploughed out the marine gravels from that vaUey, and carried 

 them into the Caithness clay then in course of formation. 



