BRITISH ISLES. 37 



Topley, W. On the Channel Tunnel. Rep. Brit. Assoc, for 1876, 

 Sections, p. 253. 



Describes the characters of the beds forming the Straits of Dover ; 

 refers to the various lines of tunnel proposed, and shows that the line 

 through the Chalk is the best. W. T. 



Traill, W. A. On the Occurrence of a Lower Boulder Clay or Till, 



with Shells, in the Counties of Down and Mayo, Ireland. Eep. 



Brit. Assoc, for 1875, Sections., pp. 83, 84. 



The shells occur in four places near the Kilkeel and Whitewater 



Rivers, in Co. Down, and in several places on the Glenulra lliver, near 



Ballycastle, Co. Mayo. The Till overlies glaciated rock, and is overlain 



by the Middle Sands and Gravels. W. T. 



On a Mass of Travertine or Calcareous Tuff, called "the Glen 



. \y u a, A3L1.U.C50 vjIl jlio, v ci i/iuc vji. v^ax^^ai. c^»iio j.uii, \^ci>ij.vu. i/iif v;ixvn 



Eock," near Ballycastle, Co. Mayo, Ireland. Hep. Brit. Assoc, for 

 1875, Sections, p. 84. [See Geological Record for 1875, p. 40.] 



Tyack, William. On a Deposit of Quartz Gravel at Blue Pool, in 



Crowan. Trans. R. Geol. Soc. Comwcdl, vol. ix. part ii. pp. 177- 



181. 



The gravel is about 400 feet above the sea-level, near the watershed 



of Cornwall. It was probably the bed of an old river when the surface 



configuration of the country was verj' different. C. L. F. 



Tyndall, Prof. John. The ParaUel Roads of Glen Roy. Pop. Sci. 



Rev. vol. XV. pp. 375-388, pi. cxli. (map) and woodcut; Proc. R. 



Inst. vol. viii. pp. 233-245, map. 



Gives a history of the subject, a description of the district, and notes 



on the physics of the Glacial Period. Infers that the terraces were formed 



on the margins of lakes dammed by barriers of glacier-ice. W. T. 



Ussher, W. A. E. On the Triassic Rocks of Somerset and Devon. 

 Quart. Journ. Geol. Soc. vol. xxxii. pp. 367-394; 3 woodcut- 

 sections. 



An extension of the paper noticed in the Geological Record for 1875, 

 p. 41. The Trias is divisible into three groups, occupying distinct 

 areas. In that N. of the Mendips the beds consist chiefly of marla 

 with dolomitic conglomerate. The second area lies S. of the Poldeu 

 Hills as far as a N. and S. line through Taunton ; here also the beds are 

 chiefly marls with a little sandstone ; the lower beds are sandstone, and 

 perhaps a breccia. In the third area, including the great mass of tho 

 Trias W. of Taunton and Blackburn, the beds are much more complex. 

 The upper part consists of marls with thin sandstones, underlain by 

 sandstones (these two are the equivalents of the whole scries of tho 

 second area) ; below the sandstones come pebble-beds, to which belong 

 the Budleigh-Salterton conglomerate. Marls underlie the conglomerate. 

 The base of the whole is composed of sandstone, breccia, and occa- 

 Bional clays. This last division probably represents part of tho 



