540 Kennj Woodivard — Address to the Geologists' Association. 



I endeavoured to express, by a diagram, to how merely superficial 

 a film of the earth's surface our knowledge is after all confined. 



Such trivial modifications of elevation or depression as we see are, 

 after all, only skin-deep ; they are but wrinkles left by the hand of 

 Time on the still fair face of Mother Earth. 



Passing from the formation of mountain-chains to the meteoric 

 agencies which have shaped them, and given to one and all the out- 

 ward forms they wear to-day, we cannot but express our thanks to 

 the Duke of Argyll for the very clear and able manner in which he 

 has endeavoured to direct the current of geological ideas concerning 

 that much-debated subject. Glacial action ^ — one of the most 'potent 

 agents with which the geologist is acquainted, and which has un- 

 doubtedly played a most important part throughout our Northern 

 Hemisphere in Pliocene and Quaternary times. When however 

 ardent geologists invoke its aid, in the form of a great polar ice-cap, 

 capacious enough to enwrap " e'en the great globe itself," alike forget- 

 ful of the fatal consequences to its Fauna and its Mora, I feel obliged 

 as a paleontologist to protest against such severity. 



Yet so strong is the faith in this universal panacea of ice, that 

 Prof. Agassiz, when travelling in Brazil-^— aZmosi beneath the equator 

 — actually saw, in imagination, a mighty glacier upwards of 

 4000 miles in length, filling the vast valley of the Amazons, and 

 stretching from its source in the Andes to Para, jDushing its mighty 

 terminal moraine before it to the sea. Then the glacier was melted, 

 and became a huge lake with block-laden icebergs on its surface. 

 Then the terminal moraine became weakened, and at last burst, and the 

 A'-ast flood of waters rushed seawards, leaving many a wreck behind I 



This view of the glacial origin of the valley of the Amazons, 

 writes Mr. C. F. Hartt, appears, from subsequent examination, to 

 have been purely hypothetical, and the geological reading of the 

 beds wholly erroneous,^ 



Prof. Phillips, in his "Geology of Oxford and the Valley of the 

 Thames," and subsequently Mr. Henry Walker, F.G.S., have shown how 

 the erratics of Cumberland, of the Midlands, or of Wales, may have 

 been ice-borne and deposited upon the then submerged sui-face of the 

 London area ; and in company with Mr. Walker we have examined 

 and endeavoured to learn the reading of the Glacial Drift at Finchley, 

 the full account of which he promises to give us in his forthcoming work. 



The valuable paper by Prof. Nordenskiold on Greenland^ has con- 

 tributed much information as regards ice-formation and ice-action of 

 immense value to geologists, and well calculated to have a modifying 

 and corrective influence over our discussions of glacial theories. 



Apart from astronomical causes, which must undoubtedly be 

 invoked in order to bring glacial conditions down to such low 

 latitudes as England and the South of France, we have in history 



^ See the Duke of Argyll's Address as President of the Geol. Soc, Lond., Quart. 

 Journ. Geol. Soc. 1873, vol. xxix. p. xxx. and p. 508. 



^ See Silliman's American Journal, No. 19, for July, 1872, article by Oh. F. Hartt, 

 p. 53. 



3 See Geol. Mag. 1872, Vol. IX. pp. 289, 355, 409, 449, 516, 



