B. Mackintosh — Height of Glacial Drift. 399 



We miglit have in oiir latitude a summer heat of 130°, from the 

 general elevation of the heat of the globe, from an increased volume 

 of the Gulf-Stream, and from a greater prevalence of the west and 

 south-west winds. 



The Pluvial Period which I proposed, and which was so much 

 objected to in the discussion of my paper,* does not require any greater 

 volume of water than has been before suggested by geologists. I 

 find that heights of 80 feet were proposed for the ordinary difference 

 of winter and summer floods, in passages of two different memoirs 

 by Mr. Prestwich, as occurring during what he considers the earlier 

 part of the Gravel Period, 



There is, however, in England, no appearance of tropical vegeta- 

 tion . in the Quaternary deposits, such as we should expect would 

 accompany a temperature of 130°, and we must therefore try one of 

 the other alternatives. 



We could not have rivers varying 80 feet in summer and winter 

 without some such rainfall, except we have pluvial and tidal condi- 

 tions very different from those now in the Thames and Somme 

 Valleys. What we want is to explain the enormous rise of rivers in 

 a cold climate during the Quaternary Period. In the year 1840 the 

 ice brought down by a January flood gorged at a point about 9 

 miles from the mouth of the Vistula, and cut a channel through the 

 sand hills to the sea. This is now the mouth of the Vistula, that 

 passing Dantzic, has been turned into a canal.^ 



I do not intend here to discuss the question of subsidences and 

 elevations, which have affected the surface of the earth so largely, 

 and have no doubt occurred in some localities during the period 

 under consideration. I would, however, remark that in Wealden, 

 Eocene, or Miocene Deltas is there any instance of any large 

 fluviatile deposit having been elevated or depressed evenly over a 

 large area ; while all over the worl d a perfectly even movement of 

 subsidence is supposed to have taken place, just at the mouths of 

 large rivers, in the Quaternary or most recent period, in order to 

 account for modern freshwater Delta deposits containing shells living 

 in the adjoining seas, being now found hundreds of feet below the 

 sea-level, 



( To be concluded in our next number.) 



V. — Glacial Drift of the Central Part of the Lake District, 



UP to 2800 feet above the Sea. 



By D. Mackintosh, F.G.S. 



(Author of Articles on the Drifts of the Borders of the Lake District.) 



DUPING five and a half weeks' examination and study of the 

 glaciated rock-surfaces and drifts of the south-central part of 

 the Lake District, in June and July last, I was fortunate in meeting 

 with many fresh and clear sections in diggings for house sites, drains, 



^ See Quart. Journ. Geol. Soc. Lond., 1868, May 10, vol. xxiv. pp. 455-6, 



2 Pfeffer, " On the Vistula," Dantzic, 1849. The gorging of ice at the mouth of 



the Thames, Seine, and Somme may have assisted in the production of some of the 



remarkable gravel-beds in these rivers. 



