452 MISS E. ASTON AND PROP. BONNET ON [A-Ug. 1 896, 



22. On an Alpine Nickel-bearing Serpentine, with Fulgurites. 

 By Miss E. Aston, B.Sc, with Petrographical Notes by 

 T. G. Bonnet, D.Sc, LL.D., F.R.S., V.P.G.S., Professor of 

 Geology and Mineralogy in University College, London. (Read 

 March 11th, 1896.) 



The rocky peak of the Biffelhorn (9616 feet), well known to all who 

 have visited Zermatt and the Gornergrat, forms part of a large 

 mass of serpentine which seems to vary slightly in composition and 

 is generally more or less schistose, becoming in places quite slaty — 

 the effect of pressure. 1 On the summit of this peak the compass, 

 as is well known, exhibits the most extraordinary variations, and 

 the rocks appear to be not seldom struck by lightning. 2 Specimens 

 exhibiting fulgurites were collected on it by both Prof. W. Ramsay 

 and Mr. J. Eccles in 1890, the examination of which has led to 

 some interesting results. 



The geologist, in working over different parts of this large mass 

 of serpentine, observes that, where the original structure is not 

 obscured by subsequent pressure, the rock is not quite uniform in 

 •character — one variety being an ordinary dark green bastite-serpen- 

 tine (sometimes also containing augite), the other being a little 

 tougher and harder under the hammer and slightly rougher when 

 handled ; in short, it is not quite so normal a serpentine as is the 

 other variety. Of this harder kind the upper part (at any rate) of 

 the Riffelhorn peak is composed. 



It will be convenient to speak of the microscopic structure and 

 chemical composition of the rock before describing the effects of 

 the lightning, though the latter was the reason that induced Prof. 

 Ramsay to ask the present authors to investigate the former 

 questions. 3 



Slices for microscopic examination were prepared from four separate 

 specimens. These exhibit slight varietal differences, which, how- 

 ever, are comparatively unimportant. Hence their constituent 

 minerals may be described together. These are : — 



(a) A clear colourless mineral in flakes, which are sometimes rather 

 irregular in outline and vary in size up to about '025 inch. They 

 have a mica-like cleavage, but it is hardly so well defined as 

 in that mineral. The smaller flakes, with crossed nicols, give 

 bluish-white and dull blue tints; the larger fairly bright 

 colours. The majority give straight extinction, but not a few 

 flakes (which correspond in all other respects) extinguish at 



1 See, for details, Bonney, Geol. Mag. 1890, p. 533. 

 a Tyndall, ' Glaciers of the Alps/ 1860, pp. 141-145. 



3 Miss Aston is responsible for the chemical work ; Prof. Bonney for that 

 with the microscope. 



