On tlie Serpentinite of the Lizard. 281 



intimate mixture of felspathic and quartzy matter. The laminae 

 are regular, even, and widely continuous, so that they have 

 quite the appearance of having resulted from sedimentation. 

 On the other hand, there are places in the neighbourhood, 

 especially on the shore between Poltesco and Kenwick Cove, 

 where a rock, essentially serpentine, encloses separated masses, 

 in beds, of semimetamorphosed sandstones and argillites, the 

 latter possessing the character of imperfect hornblende schists. 



These no doubt would be "embarrassing" cases to De laBeche; 

 but now that important discoveries connected with serpentine 

 have of late years been made, they cease to be such any longer. 

 Hence we shall adopt the opinion (fully confirmed by our own 

 researches in ophite) entertained by some of the leading mine- 

 ralogists and mineralogical chemists (Bischof, Dana, Gr. Rose, 

 Blum, Haidinger, and others), and disputed by only one autho- 

 rity of eminence*, that serpentine is in all cases the product 

 of chemical changes or methylosis, effected in a preexisting 

 mineral or rock of another kind, and analogous to pseudomor- 

 phism in crystalline solids. Obviously changes of the kind 

 may take place in igneous as well as metamorphic rocks, mean- 

 ing by the latter term aqueous deposits that have undergone a 

 superinduced crystalline or structural transformation. 



As regards the intersecting masses above noticed, it seems 

 almost certain that they were originally igneous injections ; 

 and with respect to the bedded masses, such as the one occur- 

 ring at the mouth of Poltesco Cove, it would seem probable 

 that they have been in their origin argillaceous and arenaceous 

 sediments, which became converted into hornblende schists, 

 gneiss, and other metamorphics. 



There are various kinds of igneous rocks in the Lizard : 

 some are hornblendic or dioritic ; others, in the form of inter- 

 secting dykes and intercalary beds, are pyroxenic or doleritic. 

 We have little to say respecting the former, as time would not 

 admit of their being properly examined on the occasion already 

 notified. "We shall therefore offer no decided opinion as to 

 whether any of the Lizard serpentinite is a methylosed form 

 of an igneous hornblendic rock ; but it may be remarked that 

 the hypersthene variety of the latter, occurring at Crouza and 

 other places, seems, if itself is not a changed product f, to have 

 been converted into the so-called diallage, common in some of 

 the serpentinites. We have, however, to notice a fact which 

 goes far to prove that much of the latter rock around Poltesco 

 Cove was originally a dolerite. 



* Dr. Sterry Hunt maintains that serpentine is an original chemical 

 precipitate. 



t The Crouza stone has much the appearance of having 1 undergone a 

 change ; so that it may have been originally like the hypersthenite of Vol- 

 persdorf, Moravia. 



