550 T. M. Meade — Present Aspects of Glacial Geology. 



meet the exigencies of the latest discoveries, are immeasurably 

 increased when we attempt to explain these Muirkirk shelly deposits 



on that system. The great bulk of materials enclosed in the Drift of 

 Ayrshire has worked outwards and downwards, as might be expected 

 in a world governed by gravitation. This, I conceive, is the true 

 explanation, taken together with the wider area on which denuding 

 agents could work, of the presence of Boulder-clay covering the 

 country in large sheets at low levels. 



Those who from their studies of glacial phenomena have b^en 

 led to look upon land-ice as the almost exclusive agent in the 

 manufacture and distribution of glacial deposits, ask those who are 

 in favour of the sea origin of a large portion of these deposits to 

 point out in all beds classed as marine,, marine exuvias, and if they 

 cannot do so, consider it fatal to the submergence theory. 



Is not this an extravagant demand to make, for it is really only 

 under exceptional conditions that such organic remains are 

 preserved ? Destruction was everywhere going on from the time 

 of the existence of these molluscs in the icy and stone-laden seas to 

 that in which they have been exposed to destruction and dissolution 

 by percolating acidulated waters when these beds became exposed 

 to subaerial influences. We have seen that where the matrix in 

 which these organic remains are entombed is of a non-porous and 

 dry character, like much of the Boulder-clay of Ayrshire, the 

 remains are preserved even to the epidermis. There is also the 

 example of Clava in Nairn, which the Committee of the British 

 Association appointed to investigate pronounced to be a shell-bed 

 in situ, resting upon 86 feet of coarse gravel and sand, and overlaid 

 by 63 feet of Boulder-clay and sands, showing a submergence of the 

 land to the extent of 500 feet. 



Again, if we look broadly at the distribution of these shelly 

 deposits, we find that they occur all round our maritime coasts in 

 Lancashire, Cheshire, and Wales, in Cumberland and Westmore- 

 land, Wigtownshire and Ayrshire, and along the eastern coasts of 

 Ireland. The same is to be said of the eastern coasts of England 

 and Scotland. Is it probable that land-ice would so universally 

 work from the sea towards the land ? Are we to explain the 

 presence of sea-shells imbedded in Boulder-clay up to 1,061 feet in 

 Ayrshire, 25 miles distant from the coast in a bee-line, by a great 

 glacier proceeding from the Atlantic, crossing Cantire and the Firth 

 of Clyde, and working 25 miles inland, when the travel of the 

 material, excepting as regards some Highland schists, has been in 

 the opposite direction ? l I confess that my education in the 

 principles of Button and Lyell, and my own natural mode of 

 thought, make me averse to such drafts upon our scientific imagina- 

 tion, when there is a simple and direct explanation close at hand. 

 It was well observed by Playfair, some 90 years ago. that " a 

 theory that explains everything explains nothiug." • May we not 



1 See Memoir of Geol. Survey, Scotland, Explanation of Sheet 7. 



2 " Illustrations of the Huttonian Theory." 



