Trof. J. Young — Deposits preserved under " Till." 163 



cealment was effected in the presence of very thick Till. It 

 may be said that the ice pushed its moraine profonde before it, but 

 then Hugh Miller's "pavements" have always been referred to as 

 proofs that the ice overrode not displaced the Till already accumu- 

 lated. And this was inferred from the fact that glaciers, when they 

 do override their terminal moraines, grind down their new beds. 

 Professor Geikie has suggested that the upper part of the Till of 

 Scotland may belong to the same series as the inland Till, may 

 indeed have been the product of the same ice-sheet, in which case 

 " they will indicate for us those portions of the great grund mordne 

 which, instead of accumulating on or close to the land, were actually 

 pushed by the advancing ice far out to sea, where they were more or 

 less affected by marine currents, and sometimes received and pre- 

 served marine organisms." Even this passage does not give a clear 

 view of how the Till accumulated on the land to such depths as I 

 have mentioned ; for it must be remembered that Till contains from 

 60 to 65 per cent, of impalpable mud which, had the moraine profonde 

 been accumulated on land, would have been washed away by the 

 waters constantly present beneath moving ice. But the admission 

 that the upper part of the Till might have been laid down in the 

 sea without being wholly rearranged is important. The preparation 

 of a text-book compelled me, four years ago, to record the difficulties 

 which the ice-sheet did not solve, and which I had always pointed 

 out in my lectures. I then suggested as a possibility that the Till, 

 pushed by the advancing ice-sheet off the land, might have gathered 

 on the sea-floor in comparatively undisturbed water, protected by 

 ice, either the land-ice or a mass of ice of greater size and duration 

 than the modern ice-foot. This compromise between land-ice and 

 sea-ice seemed the only possible way of reconciling the thickness 

 of the Till at places with its generally local aspect. Deposits of 

 promiscuous rubbish over stratified material without disturbance of 

 the latter is thus possible, while the crumpling and contortion of 

 the strata in certain places might be the work of bergs or coast-ice, 

 the erosion perhaps due to the subglacier waters. When we are 

 asked to believe that the Till is not merely a product of land-ice, 

 but acci;mulated on land under a moving ice-sheet, and are further 

 asked to accept the erosion, the contortion and the non-disturbance 

 of stratified beds as alike the accompaniments of the passage, not of 

 land-ice, but of the morainic matter pushed forward by it, we are 

 practically asked to give up the attempt to solve a difficulty which 

 has never been really faced. This was, I assume, not Mr. Geikie's 

 meaning ; indeed a foot-note betrays consciousness of the unsatis- 

 factory character of the argument, though the suggestion that the 

 interglacial beds were not eroded by the ice because they were 

 frozen scarcely adds to our knowledge. Mr. Geikie says that the 

 varying, I should call it eccentric behaviour of the ice, is no more a 

 difficulty than the erosion by a river at one point, the deposit of 

 alluvium at another. But this, like all analogies, is a dangerous 

 illustration : the alluvium is thrown out by the river and left. It 

 would indeed be a support if the river laid down thick alluvium 



