524 Correspondence — Mr. J". W. Judd. 



combined action of subaerial erosion and subterranean movement, he 

 finds two obstacles to his acceptance of the same explanation in the 

 case of certain smaller lakes. Most happy should I be if any remarks 

 of mine sufficed to meet the difficulties expressed by so candid a 

 reasoner as Mr. Miller. 



His first argument is propounded by Mr. Miller in the following 

 terms : " It appears to me that no halting-place can logically be 

 found by those who, with Sir Charles Lyell, allow only •' some 

 mountain tarns ' to Prof. Eamsay's demand for lakes ; that either a 

 glacier is inadequate to hollow even a tarn, or that it can enlarge it 

 to any reasonable proportions." Need I point out to my friend that 

 everj^thing in this controversy depends on the sense that we are to 

 attach to this highly elastic phrase " reasonable proportions." If any 

 one, for example, were found bold enough to suggest that the rock- 

 basins of the Black Sea, or the two occupied by the Mediterranean, 

 or the larger ones which hold the Atlantic, Pacific and Indian Oceans 

 respectively, were scooped out by glaciers (and really one would not 

 be surprised at anything being claimed for ice-action at the present 

 day), of caurse Mr. Miller would admit that these were beyond " rea- 

 sonable proportions," to be produced by such a cause. Yet it would 

 certainly be as easy to adduce a series of rock-basins, constituting an 

 insensible gradation from a Scotch loch up to even the largest ex- 

 amples which I have cited, as it would be to construct a similar series 

 downwards into the tiniest tarn. There is surely no more want of 

 logic in stopping at one point rather than at another in this perfectly 

 graduated series. My own faith in the powers of glacier erosion stops 

 short of anything that, without flattery, could be called ''a lake" at 

 all ; some are gifted with powers of belief that will embrace Cumber- 

 land meres and Highland lochs ; more strongly constituted minds do 

 not pause before an Alpine lake ; and a few (but these must be 

 inspired with " faith that could remove mountains ") have claimed 

 that Lake Superior itself may be '' glacier-formed." I cannot help 

 thinking that Mr. Miller will, on reflection, perceive the fallacy em- 

 bodied in the oft-repeated assertion that, granting irregularities of 

 surface may be produced under a glacier, all that is required for the 

 production of the vastest lakes is a sufficient volume of moving ice. 

 Does not a Highland burn wash out many a tiny basin under its 

 waterfalls, and at other points in its course ? Yet who would venture 

 to assert that, because the Mississippi has many thousand times the 

 volume of the Highland burn, it could make basins many thousand 

 times as big ? 



In the second argument raised by Mr. Miller, great stress is laid 

 upon the undisturbed condition of the so-called Cambrian beds of 

 Sutherland. But while, as compared with neighbouring rocks, these 

 appear " nearly horizontal," I have not the smallest doubt that 

 when they come to be carefully studied in detail, their wonderful 

 parallelism and regularity will be found — as in the case of the Alpine 

 dolomites, which present quite as regular an appearance when seen 

 from a distance — to be a mere optical delusion ; and that these 

 ancient masses have been subjected to flexures and fractures not a 



