892 T. (3. BONNET ON THE SERPENTINE .VXD 



schist by the track which ascends it ; the adjoining islands appear to 

 be one serpentine, the other schist. 



The hornblende schist on each side of the cove has a fairly regular 

 strike, of about S. 23° W., running straight at the main mass of 

 serpentine, and dips at a high angle (about 86°) on the western side ; 

 north of the above spot I could not find any more serpentine. 



The Eastern Coast. 



(a) The Coast to CoveracJc. — The sections on this coast are, on the 

 whole, more complicated than those on the western. Commencing at 

 the narrow cove of Perranvose near Landewednack, we find this cut 

 down to the shore through hornblende schist ; but by turning aside 

 along a track before the steepest part of the descent, we are in a 

 few minutes brought to a serpentine-quarry at the top of the cliffs 

 above the sea. 



By the side of the road leading into this, the junction of the 

 serpentine with the hornblende schist is well seen. The former 

 overlies the latter, following very nearly the plane of its bedding, 

 which here dips at about 40°. The last foot or so of the serpentine 

 is extremely rotten, crumbling into dust under the fingers; the 

 hornblende slate is also rotten, and stained red ; hence, as is often 

 the case, the junction may be easily overlooked. Its nature, how- 

 ever, is clear ; for careful search will detect two small tongues of 

 serpentine a few yards distant in the hornblende slate — the larger 

 about 2 feet in diameter. They are extremely rotten, but un- 

 doubtedly are serpentine. 



The quarry furnishes some handsome varieties of this rock, gene- 

 rally a compact purplish or reddish brown groundmass, mottled and 

 veined with pistachio green, in which are small groups of bronzite 

 crystals of greenish hue and submetallic lustre, and sometimes 

 veins of brightish red haematite (no. 9). Some masses are almost 

 wholly of a grey-green colour ; but this is only the result of decom- 

 position ; in some, minute crystals of magnetite are common. The 

 lower part often exhibits a curious fissile structure, the cracks 

 being filled by calcareous films. Sometimes the latter are about | 

 inch thick and the mineral is aragonite. 



By descending the " tip " of the quarry to the beach and walking 

 to the end of a little headland, we have further proof of the intru- 

 sive character of the serpentine. The headland consists of horn- 

 blende schist, resting on serpentine which forms a little isthmus ; 

 the slope on the south of the " tip " shews hornblende schist with 

 intrusive tongues of serpentine ; then two or three more masses of 

 hornblende schist crop out in the slope ; and finally there is a small 

 headland of that rock. On the other side, beyond the debris, is ser- 

 pentine curving round to another little headland of the same rock. 



Rounding this, we enter a second little recess, and passing two frag- 

 ments of schist included in the serpentine, come, on the opposite side, 

 to a third of the most singular shape. Any one looking at the outline 

 only, would take it for a dyke (see fig. 1). The bedding however, 



