J. A. Birds— On the Me of Man. 227 



origin of the Lower Boulder-clay (though I differ with him as to 

 which is the Lower Boulder-clay), as produced by a resultant from 

 the collision of the Scotch and Cumberland glaciers and from the 

 advance of another great Irish glacier, seems to me very plausible, 

 and may possibly be true. He, however, divides the Post-Pliocene, 

 formations into, in descending order : — 



1. Stratified gravels, sands, and shelly clays. 



2. A Kame series. 



3. Upper Boulder-clay = Scotch Maritime Boulder-clay. 



4. Intermediate beds of stratified sands and gravel. 



5. Lower Boulder-clay = Scotch Till. 



And he accounts for the formation of the first two members of the 

 series by supposing them to have accumulated, not without the aid 

 of icebergs, during the great submergence \ and the last three to have 

 been formed during the first Glacial period, in which there was one 

 or several intervals of retirement of the ice, when the intermediate 

 beds were deposited. 



In my paper I have taken the formations to- occur in just the 

 reverse order, viz. in ascending series : — 



1. Lower Boulder-clay = Mr. Home's shelly clays ; passing up 

 into 



2. Middle Drift = Mr. Home's stratified sands and gravels and 

 Kame series ; and thence into 



3. Upper Boulder-clay, with intercalated beds of sand and gravel 

 = his Upper and Lower Boulder-clays, with the same intercalated 

 beds. 



I may add that I regard my Upper Boulder-clay (yellowish-brown 

 and bluish) as analogous to similar deposits in the mountains of the 

 Lake District ; and the Middle Drift and Lower Boulder-clay as 

 analogous to similar deposits in the Blackpool cliffs. 



The mode in which I conceive each member of the series to have 

 been formed has been already indicated in my paper. 



As to which is the true order of the formations, the question must 

 be determined, of course, by reference to sections, such as that of 

 which Mr. Home has given a lithograph, near the mouth of the Bal- 

 lure Glen, and by all sections thence along the northern base of the 

 hills to Kirkmichael. 



As far as my observation went, I identified the sands and gravels 

 capping the clays at the northern end of the island with similar sands 

 and gravels in the cliffs at Kirkmichael, and on the shore at the Bay 

 of Peel. 



A priori, however, is it not against Mr. Home's view of his Lower 

 Boulder-clay being really such that there should be intermediate for- 

 mations of sand and gravel when the cold was at its extreme, and the 

 ice, according to his showing, 2,000 — 3,000 feet thick ? Is it not 

 much more probable that these interglacial beds should have been 

 formed during the Upper Boulder-clay period, when the cold was 

 much less and the ice thinner? 



And secondly, if all the deposits are assigned to the first glacial 

 period and the great submergence, what memorials are left, beyond 



