almost exactly in the face of the supposed Criffel current? Here an ocean-current is obviously out of the question; and accordingly we are told that this dispersion of Welsh boulders was probably the result of wind. But why should this wind have propelled the floating-ice so far and no further in an easterly direction? Surely if floating-ice was swept outwards from Great Arenig as far as Eryrys, bergs must have been carried now and again much further to the east. And if they did not sail eastwards, what became of them? Did they all melt away immediately when they came into the ice-laden current that flowed towards the south-east?[Y] A still greater difficulty remains. The Criffel and Cumbrian erratics suddenly cease when they are followed to the south, great quantities of them being accumulated over a belt of country extending from beyond Wolverhampton to Bridgenorth. What was it that defined the southern limits of these northern boulders? It is clear that it could not have been high-ground, for the Severn valley, not to speak of low-lying regions further to the north-east, must have been submerged according to Mr. Mackintosh's hypothesis. There was therefore plenty of sea-room for the floating-ice to escape southwards. And yet, notwithstanding this, vast multitudes of bergs and floes, as soon as they arrived at certain points, suddenly melted away and dropt their burdens! In what region under the sun does anything like that happen at the present day? Mr. Mackintosh thinks that the more or less sharply-defined boundary-line reached by the erratics "could only have resulted from close proximity to a persistent current of water (or air?) sufficiently warm to melt the boulder-laden ice." He does not tell us, however, where this warm current of water or air came from, or in what direction it travelled. He forgets some of his own facts connected with the appearance of erratics of eastern derivation, and which, according to him, point to an ocean-current that flowed across from Lincolnshire into the very sea in which the Criffel granite and Cumbrian boulders were being dropt. The supposed warm ocean-current, then, if such it was rather than air, could hardly have come from the east. Neither is it at all likely that it could have come from the west, sheltered as the region of the Severn valley must have been by the ice-laden mountains of Wales. Again, the south is shut to us; for there are no erratics in the south of England from which to infer a submergence of that district. If it be true that all the northern erratics which are scattered over the low-grounds of England, Denmark, Holland, Germany, Poland, and Russia, owe their origin to boulder-laden ice carried by ocean-currents, no such warm water as Mr. Mackintosh desiderates could possibly have come from the east or south-east. We are left, then, to infer that the supposed warm current[Z] must have flowed up the Severn valley directly in the face