902 T. G. BONNET ON THE SERPENTINE AND 



unlike a decomposed serpentine. Careful examination, however, 

 shows that we have here, highly metamorphosed and entangled in 

 the serpentine, another mass of sedimentary rock, which has once 

 consisted of lenticular bands of a more sandy character, in a mud 

 whose mineral composition somewhat resembled that of horn- 

 blende. 



The first stage has been the conversion of the former into a kind 

 of granulite, the latter, probably, into a hornblende schist. Torn 

 off and squeezed by the igneous mass (now serpentine), the harder 

 bands have been crumpled up, and in some cases forced into the 

 softer, which at last, by slow action of water, have been converted 

 into a rotten chloritoid and rather serpentinous schist. The ser- 

 pentine around is also rotten near the junction. In some places 

 the two rocks are so altered by addition and subtraction of mineral 

 constituents that it is almost impossible to fix their precise boun- 

 dary ; still I am convinced that the above explanation is the correct 

 one. 



I have examined a slice from the most granitoid part of this rock; 

 and, though highly altered, it quite confirms my view. It consists 

 of quartz, felspar, orthoclase, and some plagioclase, with a little of 

 some variety of magnesia mica. The felspar is full of microlithic 

 alteration products. In the quartz are a good many minute cavities 

 and shapeless microliths — also some microliths of larger size, which 

 may be apatite. Here and there a piece of the felspar (it is not very 

 characteristic) is full of minute branching empty cavities or micro- 

 liths (I rather think the latter), which would certainly be quoted as 

 canal systems by the opponents of Eozoon. I have seen something 

 similar in a granitoid rock from Holsteinborg (Greenland), but at 

 present can do no more than record the occurrence, hoping to return 

 to the subject on a future occasion. It is the nearest approach to 

 an organic structure that I have ever seen*. 



From Kennack Cove we proceeded along the cliffs to the headland 

 of Karak Clews, about a mile distant. So far as I saw, serpentine 

 continues all the way; and just before reaching the point called 

 Cam Sparnack a small quarry affords some very pretty varieties 

 (no. 11) — one a rich red mottled with dark olive green, the other 

 claret-colour with similar markings, both containing in the green 

 part small crystals of greenish bronzite with a submetallic lustre. 

 Karak Clews is a bold headland formed by the extremity of a great 

 elongated mass or broad dyke of coarse gabbro, which, according to 

 the map, is about two miles long and a furlong broad. The head- 

 land terminates in a narrow ridge leading down to a precipitous 

 mass of rock running some little way out to sea; the general 

 direction is nearly N. and S., the mass further inland for most of 

 its course having a N.W. strike. 



There are very few places more instructive than this to the student 

 of igneous rocks. Broadly speaking, the ridge consists of gabbro, in 

 which so many pieces of serpentine are entangled that it would 



* Perhaps tho structure erroneously described as a Lauren tian organism, 

 ' Nature,' xiv. 8, 68, may have been this. 



