METHYLOTIC ORIGIN OP OPHITES. 37 



fine augite crystals (fassaite) which occur, mixed with calc-spar, 

 in the drusy cavities and fissures, but the whole mass of the rook 

 is converted into serpentine"*. 



The change of bedded diorite into serpentine, in the Saxon 

 Voigtland, led Breithaupt to suggest that the latter is the result 

 of an alteration of the former. 



Gustaf Rose and Bischof even went so far as to maintain that 

 serpentine may have originated not only from the most widely 

 diverse minerals, but from widely different kinds of rockf. 

 Evidences favouring or demonstrating this conclusion have been 

 made known by Blum, H. Mliller, Naumann, Bernard von 

 Cotta, Fallou, Delesse, F. Sandberger, Allport, Cunninghame, 

 Heddle, Bonney, and others. The Gal way examples we have 

 cited induce us to take the same view. 



Sedgwick declared that he was " disposed to consider certain 

 varieties of serpentine as a modification of diallage rock, rather 

 than a formation distinct from it"J. Sedgwick, no doubt, in- 

 cluded the serpentinyte of the Lizard in this view ; and we 

 should readily have agreed with him as to the character of this 

 rock, but for the fact that what seems to have been taken for 

 diallage we have shown to be pseudomorphic after crystals of 

 common black augite . 



The fact, also stated by us, that the Lizard serpentinyte closely 

 agrees in its porphyritic structure with the dolerite (wakite or 

 melaphyre) of Bufaure, in the Tyrol, inclines us strongly to the 

 view that the former was originally a rock similar to the latter. 



Moreover we are prevented from agreeing with the Rev. Prof. 

 Bonney, who, though tacitly adopting our view as to the methy- 

 lotic origin of the Lizard rock, concludes, from finding it to 

 contain what he regards as enstatite (which we take to be the 

 pseudomorphs named above) and peridote, that it is an altered 

 mass corresponding to lherzolite||. 



Other testimonies in favour of the methylotic origin of ophites 

 have of late years appeared. Professor Heddle, who has lately 



* Bischof, Chemical and Physical Geology, vol. ii. p. 322. 

 t Ibid. vol. ii. p. 417. 



{ Trans. Cambridge Phil. Soc. vol. i. p. 321 (1821-22). 

 London and Edinburgh Phil. Mag. ser. 5, vol. i. pi. 2. fig. 2. 8ee aiso 

 concluding portion of Chapter III. and footnote f. 

 || Quart. Journ, Geol, Soc. vol, xxxiii. p. 921, &c, 



