888 T. G. BOSTNEX ON THE SERPENTINE AND 



a foot wide, colour and texture much as before ; the serpentine 

 adjoining is much baked. In a small excavation on the east side of 

 the quarry, a piece of hornblende schist may be seen included in the 

 serpentine. 



Passing* on northwards we find a granite vein exposed on the 

 north side of the little cove just before reaching Ky nance, and 

 another at the zigzag of the road descending to that cove. Serpen- 

 tine forms the cliffs on the mainland, the large island, the Steeple 

 rock, and some of the smaller skerries ; it is generally of a dull red, 

 mottled with dark green, which often coats the joints (no. 2). 

 Much of it shows the sharp but rather irregular jointing so common 

 in the Lizard serpentine ; one of the nearer skerries, however, 

 exhibits a very distinct jointing in a series of parallel curves, such 

 as we not seldom see in igneous rocks. But three or four of the 

 reefs that rise from the sandy spit joining the island to the mainland 

 are highly crystalline hornblende schist ; and about the same number 

 are little bosses of vein granite : two small bosses of this also lie 

 just opposite to the opening of the cove. Of this there is a larger 

 boss in the middle of the serpentine, above the " Drawing-room " 

 cave, and another on Asparagus Island, just beyond and above the 

 " Post Office ;" these two bake and crack the adjoining serpentine, 

 and resemble that already described. 



By scrambling over the boulders along the beach to the north of 

 the Steeple rock we come (in about 100 yards) to a most interesting 

 and difficult section. At first sight it seems rather to confirm the 

 idea of a passage from hornblende schist into serpentine, the two 

 rocks being apparently interstratified, almost vertically, in a low 

 terrace-like step at the foot of the cliff which is of serpentine. As 

 we face this, we have on the south (1) serpentine, (2) a mass of 

 grey, rather sandy "hornblende schist," about 8 feet thick, with appa- 

 rently many thin laminae of red serpentine, (3) red serpentine (no. 3), 

 rather fissile in structure, two and a half feet, (4) a dark brownish 

 grey rock with crystals rather resembling diallage, two feet, (5) red 

 serpentine, four and a half feet, divided by a thin band of the schist 

 (2), then (6) bedded schist like (2), with the apparent layers of 

 serpentine, for about six feet. Here a branching granite vein 

 breaks very irregularly through the schist on the top of the terrace, 

 and shows again in three places in the shore just at the foot. "When 

 we examine carefully the back of this terrace, we see that all this 

 schistose mass is really included in the main mass of serpentine. A 

 great fragment of schist has been caught up by that rock when 

 molten ; some of the beds composing it have been forced asunder 

 and parted by tongues of serpentine. The apparent interstratifi- 

 cation of schist and serpentine on a smaller scale is due to the fact 

 that a serpentinous mineral has been deposited by infiltration in the 

 schist (as is commonly the case near a junction) ; and, further, the 

 staining of certain layers by red peroxide of iron makes them 

 simulate a rather decomposed serpentine. In two or three 

 cases these may be the ends of thin tongues of intruded ser- 

 pentine ; but inmost the red streak is certainly not hue serpen- 



