Vol. 52.] NICKEL-BEARING SERPENTINE. 459 



flakes occur, more or less prismatic in outline : these usually give 

 straight extinction and fairly high polarization-tints. Probably 

 they are antigorite. The other constituent (or constituents) has 

 evidently proved more fusible, 1 so that a structure imitating that 

 called ophitic has been produced. In some cases the fused part 

 exists as minute specks or granular patches, or it forms streaks, 

 which are either ' knobby ' or irregular, or like fibres with forked 

 ends. Both these products seem to follow cleavage-planes, and the 

 latter present a tubular aspect, but as the threads are so minute 

 (less than 25 1 00 inch in diameter) it is difficult to be sure of this 

 matter. 



A little of the brown glass, spattered on the ' green schist ' from 

 the Hornli, has been examined in like way : the chips of this are in 

 all important respects so similar to the glass described and figured 

 by Mr. Rutley in his account of the Monte Viso fulgurites that no 

 further description of its characters is necessary. 



The extreme thinness of the slaggy crust, the smoothness of the 

 underlying surface of the tube, and the rapid passage from the one 

 to the other in the case of the serpentine, are remarkable. These 

 tubes look as if they had been drilled with a fine boring-tool, and 

 afterwards coated with a viscous or c slaggy ' varnish, in the 

 making of which only the more fusible parts of the rock have been 

 melted. The holes themselves, except for their sinuous course, 

 -remind one on a small scale of the perforation made by a rifle-bullet 

 in a rather soft material, or that driven through a steel armour- 

 plate by the bolt from a large cannon. The material thus removed 

 appears for the most part to have been blown away to some distance, 

 for we do not find it deposited at the mouth of the orifice. 



Discussion. 



Prof. Ramsay mentioned that, a few days before the visit of 

 Mr. Eccles and himself to the Riffelhorn, they had spent a con- 

 siderable time on the Grorner Glacier, watching the lightning striking 

 the Riffelhorn. It is not improbable that the fulgurites found were 

 formed on this occasion. He mentioned a fulgurite which he had 

 found in 1891 on the summit of Cir Mhor in Arran, in which a slab, 

 a segment of a sphere, nearly a yard in diameter, had been dislodged 

 from one of the blocks of granite of which the hill consists. The 

 granite was glazed, as was also the dislodged slab. He had visited 

 the spot every year since, and at present all trace of glaze has dis- 

 appeared, owing to the weathering of the rock. He also remarked 

 on the probability of the presence of arsenide of nickel in the 

 rock. 



Mr. Rutlet commented on associations of nickel with serpentine. 

 The percentage of nickel oxide shown in the analysis was very 

 high, compared with the amounts, seldom reaching 1 per cent., in 



1 I think that, in both the natural and the artificial fusings, the dark glass is 

 formed by the melting together of the granules of augite and of iron oxide, and 

 the serpentinous minerals have proved more refractory. — T. G. B. 



