24 PROF. T. G. BONNET ON THE [Feb. 1 896,, 



by a calm day, we closely examined, from a boat, the whole line of 

 cliffs from Church Cove to Cadgwith. We found that, after passing 

 the huge mass of hornblende- schist which forms the crags of Cam- 

 barrow and the gloomy portal of Dolor Hugo, the rock, on approaching 

 the archway leading into the ' Prying Pan,' continues, for some 

 distance above the sea-level, to-be a true hornblende -schist, but that 

 there are, in the upper part of the cliff, several reddish granitic veins, 

 the direction of which appears to have a rough correspondence with 

 the structure of the former rock, while the cliff above these assumes 

 a more i granulitic ' aspect. On the southern side of the entrance- 

 to the ' Prying Pan/ a fault, or group of faults, brings serpentine 

 and typical • granulite ' against hornblende-schist. But, immediately 

 beyond the archway, the headland between it and Cadgwith Cove 

 presents the following section. The upper part of the cliff, beyond 

 all question, consists of the granulitic rock ; while the lower part r 

 at the south-eastern corner, for a considerable height above the sea, 

 is no less typical hornblende-schist. The two rocks gently descend 

 in a northerly direction until, near the north-eastern angle, the 

 hornblende-schist gradually disappears beneath the water and the 

 mainland crags consist wholly of typical banded granulite ; though 

 even here the hornblende-schist still appears in some skerries very 

 near to the shore. Passing round into the cove, we find that its 

 southern side, as we formerly stated, consists mainly of the ' granulitic 

 group,' but that near the water's edge the rock generally is a horn- 

 blende-schist. 1 No sharp line can be drawn between the two groups,, 

 but between the well-banded and thoroughly typical representatives 

 of each there is usually a zone from 7 to 10 yards in thickness, 

 rather neutral in character : veins of a reddish granitic rock, 

 breaking, on the whole in a horizontal direction, through a dark 

 rock which now and then resembles the basic member of the granu- 

 litic group more closely than the dark part of the hornblende-schist. 

 Obviously, if both these groups are igneous in origin, this super- 

 position cannot count for much. It may, however, have the signi- 

 ficance, that, on the assumption of the hornblendic rock being the 

 earlier extrusion, the upper part of its mass would offer less resist- 

 ance under ordinary circumstances to the passage of an intruder. 

 Hence the phenomenon may have a bathymetric significance, if it 

 has no other. 



IV . Relations of the Serpentine to the ' Granulite ' and to 

 the Hornblende-schists. 



Before discussing the group of sections near Ogo-dour and east 

 of the Lion Rock, from which my friends have drawn certain con- 

 clusions, 2 I must make a few remarks upon the general principle,, 

 which, as it appears to me, is implied, if not actually enunciated in 



1 It is regularly banded, the white felspar and dark hornblende showing a 

 hypophitic structure, and differs only from the most normal hornblende-schists 

 in becoming here and there slightly micaceous. 



a Quart. Journ. Geol. Soc. vol. xlix. (1893) p. 210. 



