408 Frof. T. G. Bonney — Remarks on Serpentine. 



chiefly of micaceous and liornblendic schists, that the Cornish ser- 

 pentines ajDpear, accompanied by so-called gabhros and greenstones." 

 I thought my first paper made it clear that the serpentine was always 

 seen in association with the middle and upper gToups. Further, in 

 my second paper, I say of a diabase, which near Polpeor is intrusive 

 in the lowest group, " it is the only igneous rock which I have 

 detected in this group," Of course, as I believe the serpentine to 

 be an intrusive rock, it must break through the lowest (micaceous) 

 group, and at Porthalla it is not far from the upper part of it, but, 

 curiously enough, it is never seen actually to cut it. 



On the same page he also says : " Boimey has extended his obser- 

 vations to the serpentine and associated rocks in Italy, which he 

 includes under the general title of ophiolites." I have never, so far 

 as I can remember, used the word ophiolite; and if there is one thing 

 for which I have striven, it is the resti'iction of the term serpentine 

 to one kind of rock. Again, on p. 179 he says, with reference to 

 the three districts noticed by me in Italy, " In each of these districts 

 [Bonney] . . , supposes an intrusion of serpentine, or rather of 

 olivine rock, among crystalline schists,^ followed by a later intrusion 

 of gabbro." Near Genoa I speak of the serpentine as probably 

 intrusive to "an indurated shale of schistose aspect;" at Monte Rosso 

 in " a dark-coloured rock, which is now rather schistose-looking, 

 and greatly crumpled and crushed, but apjoears to have been origin- 

 ally a shale with irregular stony bands or concretions ;" and in 

 another place as including a mass of "an indurated argillaceous rock;" 

 at Figline (the third locality), as "clearly intrusive in stratified 

 rock, probably of Tertiary age ! " 



In the present paper it is my intention to recapitulate very briefly 

 the evidence in favour of the following statements in those regions 

 which I have examined, (1) that serpentine is in many cases dis- 

 tinctly proved to be an intrusive rock ; (2) that it has come from 

 the hydi-ation of a jDeridotite. First, as regards Cornwall, both on 

 the eastern and western coasts of the Lizard peninsula, the serpentine 

 and the hornblende schist may be repeatedly seen in contact, with 

 the following results : — 



(1) That in certain cases the evidence as to the nature of the 

 junction, whether it be intrusive or a fault, is indecisive, both rocks 

 being so rotten and stained on either side of the line of parting that 

 it is impossible to decide. These cases of course cannot be quoted 

 by any disputant ; they prove no more than does a defaced page of a 

 manuscript in a controversy about the language in which it is written. 



(2) That in many cases the serpentine cuts sharply across the 

 broken edges of the strata in both the hornhlendic and the graniditic 

 series, and thrusts wedges between and tongues into them ; that the 

 lines of junction are often perfectly clean, sharp, and distinct, the 

 serpentine sometimes following for a time a line of bedding, then 

 cutting indifferently across layers of different mineral composition, 

 some hornhlendic, some mainly a quartz-felspar rock. 



(3) That repeatedly, especially on the east shore, masses of the 



^ The italics are mine. 



