1)10 



T. G. BONNET ONT THE SERPENTINE AND 



had altogether twenty-one slides prepared from different localities* ; 

 and Mr. S. Allport has kindly permitted me to use others from his 

 collection, admirably cut by himself. I have also procured, for 

 comparison, several others from foreign serpentines. A suspicion 

 of the true nature crossed my mind in 1874, when examining a slide 

 from the black serpentine near Cadgwith (no. 10). A specimen col- 

 lected in 1875 at Coverack Cove rendered the conjecture a certainty ; 

 and a further confirmation was given by my visit to the Ariege, and 

 by specimens collected at other Cornish localities, in 1876. In the 

 following description I shall not take the slides in the order in 

 which their localities are mentioned above, but group them so as 

 best to tell their story. 



Coverack Cove (no. 12). — This serpentine is often considerably 

 decomposed ; but my slide was cut from a well-preserved specimen . 

 To the eye it is a dull mottled red-and-green rock, with ill- defined 

 flakes in the latter part of a silky bronzitic mineral. With the 

 microscope, we see that about two-thirds of the rock consists of a 

 clear transparent mineral of a texture rather like frosted glass, tra- 

 versed by reticulated veins of a golden- coloured (varying to greenish 

 and reddish-brown) serpentine. These serpentine veins run together 

 sometimes like matted roots, and apparently coalesce like the pseu- 

 dopodia of foraminifera (fig. 8). As described in the gabbro above, 



Fig. 8. — Portion of a Slide of 

 Serpentine from Coverack 

 Cove. 



Fig. 9. — Portion of a Slide of 

 Lherzolite {Etang de Lherz, 

 Ariege), showing the form- 

 ation of Serpentine. 



The granulated part unchanged olivine ; the rest rather fibrous serpentine. 

 (Magnified 50 diameters, about.) 



there is the same deposit of iron peroxide (here reddish) parallel to the 

 sides of the fibres, which in the larger patches of serpentine seem 

 either to disappear or to be aggegated in dusky patches. On applying 



* These, with the others used in this paper, have been excellently prepared 

 for mo by Mr. Cuttell, 52 New Compton Street, Soho. 



