The Pliocene Glaciation of Svbalpine Switzerland. 117 



Riffelhorn (near Zermatt) by Prof. W. llamsay, E.R.S., and J. Eccles, 

 Esq., E.G.S. As they showed some very well marked ' lightning- 

 tubes,' the former thought that possibly analyses might prove 

 interesting. These were undertaken by Miss Aston at University 

 College, London. The rock is a serpentine, somewhat schistose from 

 pressure, which has been formed by the alteration of a rock chiefly 

 composed of olivine and augite. One of the analyses gives 4 # 92 

 per cent, of nickel oxide and hardly any lime. Prof. Bonney detected 

 some awaruite under the microscope, but not nearly enough to 

 account for the analysis. Reasons are given to show that the 

 nickel oxide probably replaced lime in the pyroxenic constituent of 

 the rock. 



The tubes, about y 1 ^ inch in diameter, are round in section, 

 cleanly drilled, and lined with a very thin film of dark brown 

 or black glass. The microscopic structure of this is described, 

 as well as that of glass made by melting the rock with a blow- 

 pipe (using oxygen). Some fulgurite-glass from the Hornli has also 

 been examined (much resembling that described by Mr. Rutley 

 from Monte Yiso), and an analysis of this rock is given. 



2. ' The Pliocene Glaciation, Pre-Glacial Valleys, and Lake-Basins 

 of Subalpine Switzerland : with a Note on the Microscopic Struc- 

 ture of Tavayanaz Diabasic Tufa.' By C. S. Du Riche Preller, M.A., 

 Ph.D., E.G.S., E.C.S., A.I.M.I.E., M.l.E.E. 



I. The main object of this paper, which is the sequel to one read 

 last session, was to solve the problem whether the Pliocene glacio- 

 fluviatile conglomerates of the Swiss lowlands were deposited on a 

 plateau or in already existing valleys. Eor the purpose of this 

 enquiry, the author examined last summer a large additional 

 number of glacial high- and low-level deposits throughout the Zurich 

 Valley over an area more than 40 miles in length; and his investi- 

 gations further led him to important conclusions with respect to the 

 combination of causes which determined the formation of the lake- 

 basins lying in the same zone at the foot of the Alps. 



II. The author established the true characteristics of the Pliocene 

 nagelfTuh as distinguished from Miocene, purely fluviatile conglome- 

 rate on the one hand, and from glacio-fluviatile Pleistocene gravels 

 on the other. "With respect to the origin of the Pliocene conglome- 

 rate, he contended that the material composing the same was not 

 transported from a great distance, but was, in the main, derived from 

 the enormous accumulations of Miocene nagelfluh at the foot of the 

 Alps. Specimens of Miocene nagelnuh-pebbles were exhibited, in- 

 cluding the so-called ' Tavayanaz Sandstone,' which the author, in 

 an Appendix to the paper, showed to be diabasic tufa. 



III. The author described in detail a variety of glacial exposures, 

 and showed that Pliocene nagelfluh in situ, of which he exhibited 

 numerous specimens, occurred not only on the ridges of the hills, but, 

 at a gradually ascending level, also at and near the floor of the 

 Zurich Valley. 



