304 Lieut.- General C. A. McMahon — 



causes, in part, it would be equally in accordance therewith. They 

 are, in either case, a stumblingblock to that of Sir Joseph Prestwich. 



The PalEeolithic implements, however, that have been found in 

 the Eubble Drift, present rather a difficulty. For such implements 

 usually appear to be of later date than the Chalky Boulder-clay. 

 And, if this theory be correct, one would suppose that the Rubble 

 Drift should have been formed contemporaneously with that deposit, 

 if not previously. I hardly think it can be the equivalent of the 

 Trail, as held by Mr. J. Allen Brown (Journ. Anthrop. Inst., vol. xxii, 

 p. 66), because, in that case, a strong semi-glacial deposit would be 

 the equivalent of a compai'atively weak one situated farther north, 

 which scarcely seems probable. 



But this is a question of probabilities, not of facts. Mr. Clement 

 Reid's theory not only gives a satisfactory explanation of the origin 

 of the Rubble Drift, but also refers the formation of the dry chalk 

 valleys to the same cause. This speaks volumes in its favour, for 

 the value of a scientific theory depends upon the range of phenomena 

 that it co-ordinates. 



V. — Notes on the Age and Structure of the Gnbissose-Granite 

 OP THE Himalayas with reference to Mr. Middlebiiss's 

 Memoir on the Geology of Hazara. 



By Lieut. -General C. A. McMahon, V.P.G.S. 



I AM indebted to Mr. C. S. Middlemiss, Superintendent of the 

 Geological Survey of India, for a copy of his Memoir on 

 the Geology of Hazara and the Black Mountain recently published.^ 

 Mr. Middlemiss has embodied in his Memoir the results of an 

 unfinished survey by Mr. A. B. Wynne, late of the Geological 

 Survey of India, and by linking these with his own more recent 

 work, has given us an interesting and valuable Memoir on the 

 Geology of the Himalayan district of Hazara. 



As there seems to be no prospect of a systematic survey of 

 the whole Himalayas being undertaken during the lifetime of 

 the present generation, the geological student has to content himself 

 with such information as observers are able to glean during visits 

 of limited duration to these mountains. The Government of India 

 doubtless considers the search for coal, and other economical pro- 

 ducts, as more pressing than investigations having the elucidation 

 of theoretical problems for their aim ; hence the members of the 

 Geological Survey are only able to devote limited periods during 

 occasional visits to the Himalayas to pure geology. 



Mr. Middlemiss's Memoir contains a mass of well-digested facts, 

 and he draws many inferences from those facts with which I cordially 

 agree. There are some theoretical questions, however, which have 

 an important bearing on the history of the Himalayas on which 

 we differ ; and I propose, for the sake of brevity, to limit myself 

 in this paper to the discussion of these questions. 



^ Memoirs of tlie Geological Survey of India, vol. xsvii. 



