Proceedings of the Cambridge Philosophical Society. £18 
the several parts of the coast between the Helford river and 
Loe-Bar. From a general review of the facts presented on 
both sides of the promontory, he concluded, that a section made 
from the heights above Constantine to the mouth of the Hel- 
ford river, and from thence to Old-Lizard-Head, would exhibit 
a series of formations nearly in the following order : 
1. Granite, containing an excess of mica at its junction with 
the slate. 
£. Clay-slate. 
8. Clay-slate, associated with greywacke-slate, and containing 
subordinate beds, in which were a coarse conglomerate, com- 
mon greywacke, and fine grained sandstone. 
4. Serpentine, surmounted by granular diallage -rock, and 
amorphous greenstone, passing into greenstone-slate. 
5. An extensive porphyritic formation, composed of diallage 
and hornblende. 
6. Nearly compact masses formed of the same constituents, 
associated with a very large-grained diallage-rock, and alter- 
nating with serpentine. 
7. Serpentine, irregularly associated with saussurite, diallage- 
rock, greenstone-porphyry, greenstone- slate, and granular fel- 
spar ; the several parts rarely presenting any appearance of 
stratification or order of superposition. 
8. Greenstone-slate. 
9. A formation apparently interlaced with both greenstone- 
slate and serpentine, and composed of chloritlc-slate, (in one 
place associated with thin beds of mica-slate,) talcose-slate, and 
fel spathic- slate. 
By way of conclusion, he endeavoured to identify the ser- 
pentine of the lizard with some foreign formations which appear 
among transition-rocks. 
On a remarkable peculiarity in the law of the extraordinary 
refraction of differently -coloured rays , exhibited by certain va- 
rieties of Apophyllite. By J. F. W. Herschel, Esq., F. R. S. 
Lond. & Edin. F. C. P. S., &c. Fellow of St John’s Coll.— In 
a former paper, Mr Herschel had instanced some remarkable 
deviations from the ordinary law of tints exhibited by certain 
specimens of this substance. Upon reconsidering his results, 
it appeared that these specimens could not be referred exclu- 
