394 NOTES ON THE LIZARD HOCKS. 



augites, the changes in the former being more advanced than in 

 the latter. The percolating matter from the olivine appears to 

 have a greater effect on the felspar than on the augite, the first 

 formation of anthophyllite being here found, filling the new 

 formed fissures in the felspar, where in contact with the olivine ; 

 more rarely may be seen anthophyllite forming in the fissured 

 augite, but the general change is from augite to actynolite, and 

 this does not appear to have originated from its contact with, or 

 percolations of, olivine matter. 



G-ABBRO FROM DeAN POINT. 



Fig. 14, plate D. — This rock specimen, broken from the 

 mass, and, as in the slide from Coverack, the sections carefully 

 cut from across the principal cleavage way, reveals a more 

 advanced stage in the new hornblende bands, than the former. 

 Every available fissure is filled, and probably many a splinter 

 of felspar, such as is discernable in the slides from Coverack, 

 is used up in the formation of the anthophyllite ; there is yet 

 much olivine unexhausted, and some with but very faint 

 changes visible, while in others the change is apparently 

 complete, and the hornblende occupies a far more extensive and 

 elongated position than the olivines did before the change. 

 This evidence I think proves that the apparent combustion in 

 this rock was not instantaneous, but slow and continuous, and 

 probably not far in advance of denudation. The change of 

 the olivine, also, brings to view magnetic iron, which is in 

 sufficient abundance to strongly deflect the magnet from its 

 normal position. 



Manacle Point. 

 Numerous opportunities have been afforded me by recent 

 quarrying at this Point, to get fresh samples of these rocks, which 

 appear to have offered much more resistance to atmospheric 

 denudation, and the powers of the ocean, than the neighbouring 

 olivine gabbros of Dean Point. They have a higher specific 

 gravity than others of similar felspathic appearance, and show 

 iron in far greater abundance, but the affinity for the magnet is 

 faint in comparison with other rocks of the district. This proves 

 that the iron it contains is not altogether magnetic. Then comes 



