436 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 28, 



the mounds below a certain height, points to a cold period succeeding 

 one less cold. Moreover the mounds between 800 and 1000 feet, 

 which contain boulders, show the presence of floating ice at a time 

 when the land was thus far submerged ; if a mild period succeeded 

 that time and continued until the non-boulder-bearing mounds were 

 formed at various heights between 800 and 250 feet, it is evident 

 that the scattered boulders upon the mounds could not have been 

 deposited by floating ice. Hence they must either have been left 

 by a new set of large glaciers, produced after the emergence of the 

 land, or the above theory falls to the ground. That glaciers did 

 exist after the emergence of the land is sufficiently evident ; but that 

 they were of such size as to spread out into much of the low ground 

 there is no evidence, even if it were likely that great glaciers could 

 ride over mounds of loose sand and leave boulders perched upon 

 them. Therefore the supposition that the mild period occurred 

 during the re-elevation of the land is false. 



But another supposition is possible. The mild period may have 

 come on before the subsidence even commenced, and have continued 

 until the land had sunk some 800 feet beneath the sea. During the 

 gradual sinking sand and gravel bars might be produced at various 

 heights, when there was no floating ice to transport large boulders. 

 But if cold then began to return, the mounds above 800 feet might 

 contain ice-transported blocks, and boulders would be dropped 

 upon the earlier-formed mounds. And this, I think, is what really 

 did happen. 



It may, however, be that the boulder- containing mounds above 

 800 feet were formed not during the subsidence, but during the re- 

 elevation, even although they seem from their position to be one 

 with the non-boulder-bearing mounds at slightly lower elevations. 

 For when the land stood at about the same height during subsidence 

 and during elevation, there might be a like tendency to the forma- 

 tion of sand bars at nearly the same spots, only that in the one case 

 the mounds would not contain boulders — during a mild period — and 

 in the other case they would — during the succeeding cold period. 

 Hence, while the occurrence of mounds without contained boulders, 

 but having boulders upon them, points to a submergence with a mild 

 period, at all events until the land had sunk some 800 feet, it is 

 merely the absence of such mounds at a greater elevation than 800 

 feet that would suggest the cold period then coming on. Mr. James 

 Geikie, in his admirable memoir on " Changes of Climate during the 

 Glacial Period," after pointing out that the mild period had come on 

 before the subsidence commenced, expresses his belief that the cold 

 only began to return when the submergence was approaching its 

 limits. If future investigations in the lake-district should lead to 

 the discovery of mounds without contained boulders at a higher 

 elevation than 800 or 900 feet, my observations would almost com- 

 pletely support his conclusions. I may add that I purposely re- 

 frained from consulting Mr. Geikie's paper until I could form my 

 own conclusions from such evidence as these facts afforded, and was 

 then most pleased to find that our inferences were so nearly alike. 



