flowed outwards from the high-grounds of Wales. The united ice-stream would thereafter continue on its south-westerly course down the Severn valley to the Bristol Channel. I have no doubt that Mr. Mackintosh will yet chronicle the occurrence of chalk-flints and other eastern erratics from localities much further to the south than Ledbury. [W] See Mr. Skertchly's description of East Anglian deposits in _Great Ice Age_, 2nd edit., p. 358. Again, considerable stress has been laid by Mr. Mackintosh upon the occurrence of chalk-flints in the drift-deposits of Blackpool, Dawpool, Parkgate, Halkin Mountain, Wrexham, the peninsula of Wirral, Runcorn, Delamere, Crewe, Leylands, Piethorne (near Rochdale), and other places. "All these flints," Mr. Mackintosh remarks, "belong to the basin of the Irish Sea, and have almost certainly crossed the general course of the northern boulders on their way from Ireland." Here, unfortunately, the Irish Sea intervenes to conceal the evidence that is needed to enable us to track the exact path followed by the erratics in question. I am not so certain as Mr. Mackintosh that the chalk-flints he refers to came from the north of Ireland. Chalk-flints occur pretty numerously in the drift-deposits in the maritime districts of north-eastern Scotland, which we have every reason to believe have been derived from an area of Cretaceous rocks covering the bottom of the adjacent sea; and for aught one can say to the contrary, patches of chalk-with-flints may occur in like manner in the bed of the Irish Sea. I cannot at present remember whether any boulders of the basalt-rocks, which are associated with the Chalk in the north of Ireland, have been recognised in the drifts of the west of England; but if the chalk-flints really came from Antrim, it is more than probable that they would be accompanied by fragments of the hard igneous rocks which overlie the Cretaceous strata of north Ireland. Chalk and chalk-flints occur in the boulder-clay of the Isle of Man, where they are associated, Mr. Horne tells us, with Criffel granite and fragments of a dark trap-rock.[X] Possibly these last are basalt-rocks from Antrim. It seems reasonable, therefore, to believe that erratics of Irish origin have found their way to the Isle of Man; and if this be so, it may be permissible to assume that the chalk-flints of Blackpool, etc. (and perhaps also some of the basalt-rocks), have come from the same quarter. Mr. Horne has no doubt that the Irish erratics were brought to the Isle of Man by land-ice. Referring to the conclusion arrived at by Mr. Close that the Irish _mer de glace_ "was probably not less than 3000 feet in depth," he remarks: "It is highly probable that this great mass of Irish ice succeeded, after a hard battle (_i.e._, with the Scottish ice-sheet), in reaching the Manx coast-line. It is not to be supposed that the normal momentum of the respective ice-sheets remained constant. The moving force must have varied with changing conditions.