780 iiEPOET— 1893. 



10. In upland valleys filled with ordinary boulder clay the surface of the clay 

 is often obscurely terraced with descending gradients, corresponding to the floor of 

 the bottom of the rock valley, and is apparently due to gigantic flood-waters, which 

 at lower levels deposited glacio-fluviatile gravels, 100 feet above the level of existing 

 streams. 



11. The irregular original deposition of drift mounds upon a plain (also formed 

 of drift) encloses what the late Mr. Mackintosh, F.G.S., called ' mere-basins,' and 

 the American * kettle-holes ' : they are areas in which the natural drainage is ob- 

 structed, and formerly only flowed away by percolation through sand-banks at the 

 sides. They were originally probably all tilled with more or less water. Many of 

 these meres still remain in Lancashire and Cheshire, and vary in size from a few 

 yards to more than a mile across. They are now all more or less artificially 

 drained. The sites of a very large number are indicated by thick peat mosses. 

 These constantly are found resting directly on sand, showing that the outfall of the 

 water in the sands, at the time of the growth of the peat, was closed. 



12. The more closely the surface of the drift-covered ground in relation to its 

 origin is studied, the more recent does the termination of the glacial episode 

 appear to be. 



WEDIVESDAY, SEPTEMBER 20. 



The following Papers and Report were read : — 



1. On the Distribution of Granite Bo'iilders in the Clyde Valley. 

 By DuGALD Bell, F.G.S. 



The object of this paper was to connect the granite boulders which are found 

 in the neighbourhood of Glasgow, Helensburgh, Gonrock, &c., with a granitic 

 tract recently described by Messrs. Teall and Dakyns, of the Geological Survey, as 

 occurring in the mountainous region which lies between the head of Loch Fyne on 

 the one hand and of Loch Lomond on the other (' Quar. Jour. Geol. Soc.,' May, 

 1892). This tract, which occupies about twelve square miles, contains at least two 

 varieties of granite : a porphyritic variety, with large crystals of orthoclase, easily 

 recog^sable, and a non-porphyritic variety ; also, near its margin or junction with 

 the mica schist, bands of tonalite and diorite. These varieties correspond with 

 boulders found in the Clyde valley, especially ia its western part, and along the 

 shores of the various lochs that open out from it. The supposition put forth many 

 years ago by Mr. Smith, of Jordanhill,' that these boulders had been transported 

 from the Ben Cruachan district, was not borne out by the characteristics of the 

 rocks, and was opposed to all that was now known regarding the general glacia- 

 tion of the district. In harmony with that glaciation, however, boulders from the 

 Glen Fyne tract referred to, dispersed by Loch Fyne, Loch Eck, and the Holy 

 Loch; by Loch Sloy, Loch Long, and the Gareloch ; and in a much smaller pro- 

 portion by Loch Lomond (the tract lying almost entirely to the western side of the 

 watershed of that loch), could, it was evident, reach the various localities where 

 they are now found. The author showed specimens of the granite referred to. 



2. On the Derbyshire Toadstone. By H. Arnold-Bemrose, M.A., F.G.S. 



Toadetone is a local name for the igneous rocks interbedded with the Carboni- 

 ferous limestones of Derbyshire. It occurs in a district of 25 by 20 miles. The 

 upper and lower portions of a bed are sometimes amygdaloidal. The spheroidal 

 structure is often well marked, the columnar more seldom and less perfectly. 

 Toadstone varies very much in the amount of weathering it has undergone. It 



' Researches in Niiwer Pliocene and post-Tertiary Geology, pp. 12, 141. 



