Geological Society of London. 91 



the discharge of the Ehine below the Lake of Geneva was 35 inches, 

 and the discharge of the Mississippi only 7 inches, that the little 

 excess of discharge from glacier-rivers might be only due to the 

 elevation of the snow-covered land. He explained the serrated form 

 of the higher Swiss mountains by supposing in the Glacial Period the 

 snow and ice were only formed at comparatively low levels, all the 

 vapour as it arrived being absorbed by clouds discharging near the 

 level of the sea. Nordenskiold remarks that in the 80th parallel of 

 latitude the hills near the coast are bare of snow in summer, while 

 the low ground near the sea is always encumbered with ice and 

 snow. The same cause produces early abstraction of vapour, and 

 may enable the Poles to be free from ice. The ice-cap must have 

 been much thicker at the 70th parallel than further North. 



With regard to his description of the Quaternary deposits, Pro- 

 fessor Prestwich first reduced these strata to systematic order. The 

 writer differed from him as to climate, the divisions of the beds, and 

 the age of the valleys, etc. These strata have a local character in 

 England, but in other parts of the world Mr. Belt has found the 

 contrary to be the case. 



With regard to Dana's Eiver Mississippi in Quaternary times 50 

 miles wide, Mr. Tylor thought a river 50 times as wide as the pre- 

 sent Mississippi must be 2-| times as deep, and according to his 

 formula would have 5 times the present velocity. Such a river 

 would want 625 times the present snowfall or rainfall to fill it. 

 The melting of Dana's ''Great Glacier" would therefore have the 

 character of a debacle, without the name. The old Mississippi would 

 have exhausted such an ice-cap almost in 30 years. 



The depression of the Mississippi Valley, supposed by Dana to have 

 occurred in the Gravel Period, should be proved by examination 

 from flexures to have actually occurred, as the land is never raised 

 or depressed without a series of flexures being formed ; interference 

 with the regularity of the slopes and junctions of modern main and 

 tributary rivers was referred to as not affording evidence of any 

 disturbance. Mr. Tylor referred to the double system of flexures of 

 elevation in the Wealden area, which he had shown, in 1868, were 

 not fractures, as Hopkins had thought. Flexures had determined the 

 course of the Wealden rivers. In that area valleys and gorges were 

 produced actually resulting in the Quaternary Period from denuda- 

 tion. A north-and-south flexure of 1000 feet in a mile had occurred 

 at Guildford, and had caused the gorge of the Wey at the point where 

 the strata had also been especially depressed by an east-and-west 

 single flexure of small amount per mile, but extending over a length 

 of 20 miles. 



The contour of a section, measured by A. Tylor, of some remark- 

 able marine fossiliferous gravels at Coalbrook Dale, was compared 

 with the contour of the modern Chesil Beach. This remarkable 

 fact of isolated marine gravels in the Severn Valley apparently 

 formed of remanie'd fluviatile gravel at a height of 200 feet above 

 the sea, without trace of similar beds between Bridgnorth and the 

 sea, was then dwelt upon, and the Moel Tryfaen beds were described, 



