18 EEPOET— 1880. 



always well stratified, where they approach the underlying Laurentian 

 gneiss ' they become pebbly, passing into coarse unstratified agglomerates 

 or bonlder-beds.' In the Gairloch district ' it is utterly nnstratified, the 

 angular fragments standing on end and at all angles,' just as they do in 

 many modern moraine mounds wherever large glaciers are found. The 

 general subject of Paleozoic glaciers has long been familiar to me, and this 

 account of more ancient glaciers of Cambrian age is peculiarly acceptable. 



The next sisn of ice in Britain is found in the lower Silurian rocks of 

 Wigtonshire and Ayrshire. In the year 1865 Mr. John CaiTick Moore 

 took me to see the Lower Silurian graptolitic rocks at Corswall Point in 

 Wigtonshire, in which great blocks of gneiss, granite, &c., are imbedded, 

 and in the same year many similar erratic blocks were pointed out to me 

 by Mr. James Geikie in the Silurian strata of Carrick in Ayrshire. One of 

 the blocks at Corswall, as measured by myself, is nine feet in length, and 

 the rest are of all sizes, from an inch or two up to several feet in diameter. 

 There is no gneiss or granite in this region nearer than those of Kirkcud- 

 brightshire and Arran, and these are of later geological date than the strata 

 amid which the erratic hlocJcs are ivibedded. It is therefore not improbable 

 that they may have been derived from some high land formed of Lauren- 

 tian rocks of which the outer Hebrides and parts of the mainland of 

 Scotland form surviving portions. If so, then I can conceive of no agent 

 capable of transporting large boulders and dropping them into the Lower 

 Silurian mud of the seas of the time save that of icebergs or other float- 

 ing ice, and the same view with regard to the neighbouring boulder-beds 

 of Ayrshire is held by Mr. James Geikie. If, however, any one will point 

 out any other natural cause still in action by which such results are at 

 present brought about, I should be very glad to hear of it. 



I must now turn to India for further evidence of the action of palaeo- 

 zoic ice. In the Himalayas of Pangi, S.E. of Kashmir, according to 

 Medlicott and Blanford, ' old slates, supposed to be Silurian, contain 

 boulders in great numbers,' which they believe to be of glacial origin. 

 Another case is mentioned as occurring in ' transition beds of unknown 

 relations,' but in another passage they are stated to be ' very ancient, but 

 no idea can be formed of their geological position.' The underlying rocJcs 

 are marlced hy distinct glacial striations. 



The next case of glacial boulder-beds with which I am acquainted is 

 found in Old Red Sandstone in Scotland, and in some places in the north 

 of England, where they contain what seem to be indistinctly ice-scratched 

 stones. I first observed these rocks on the Lammermuir Hills, south of 

 Dunbar, lying unconformably on Lower Silurian strata, and soon inferred 

 them to be of glacial origin, a circumstance that was subsequently con- 

 firmed by my colleagues. Prof, and Mr. James Geikie, and is now familiar 

 to other officers of the Geological Survey of Scotland. 



I know of no boulder formations in the Carboniferous series, but they 

 are well known as occurring on a large scale in the Permian brecciated 

 conglomerates, where they consist ' of pebbles and large blocks of stone, 



