Correspondence — Prof. T. G. Bonney. ■ 481 



does not relinquish his studies, but is now engaged on a Mono- 

 graph of the recent species/ which it is to be hoped he may be 

 spared to complete to his own satisfaction and the undoubted benefit 

 of Science. W. H. Dall. 



OOie-I^^BSI^'OIsriDIEIsrGIB. 



COENISH SERPENTINE. 

 Sir, — I cannot reply fully to Mr. J. H. Collins's paper on the 

 Cornish serpentine, published at page 298 of this Magazine, in 

 which he repeats his mistakes as to the serpentine of Porthalla, 

 "until I have obtained permission from the Council of the G-eological 

 Society to have slices prepared for microsopic examination from the 

 specimens which he presented in illustration of his paper published 

 in vol. xl. of the Quarterly Journal. After this I think I shall be 

 able to demonstrate that he has wrongly interpreted the very 

 specimens on which his hypotheses are founded. In the mean time I 

 will merely remark : (1) That the formation of the mineral called 

 serpentine in the crevices of a rock no more proves that the rock 

 serpentine is not of igneous origin than the occurrence of the mineral 

 quartz in an adjacent vein proves that a quartz-felsite is not of 

 igneous origin. (2) That (contrary to Mr. Collins's assertion) there 

 is no essential distinction between the serpentine of Porthalla Cove 

 and that from other parts of the Lizard district. There is as much 

 difference as, but no more than may be commonly found between two 

 dykes or two lava-flows in the same volcano. (3) That the sei-pen- 

 tine of Porthalla in its relations to the hornblende-schist exhibits the 

 usual indications of the intrusion of one rock to a plastic condition 

 into another. The second and third of these statements will 

 no doubt be put aside by Mr. Collins, like those of Mr. Somervail, 

 as merely " a repetition of the dogmatic assertion." But in excuse for 

 this dogmatism, I may remark that the question at issue between 

 Mr. Collins on the one side and Mr. Somervail, myself, and those who 

 have worked with me at the Lizard on the other, is really one of the ob- 

 servation of facts. He in effect says, " I cannot see any evidence of the 

 intrusion of the serpentine into the hornblende schist." We reply, " To 

 our eyes the junctions (with the usual indications) are often so plain 

 that we doubt whether you really know for what to look." I may 

 further plead in excuse of a little dogmatism on my own part that 

 if there be one rock which I ought to know better than another it is 

 serpentine {i.e. the rock of the Lizard type), of which I believe 

 I have studied more examples and possess a larger collection than 

 any other person in England ; and if there be one class of phenomena 

 with which I should be familiar, it is the junctions of rocks, whether 

 brought about by igneous intrusion or by " the subsequent move- 

 ments of the strata," subjects to which for the last ten years I have 

 paid special attention. T. G. Bonney. 



1 This Monograph is, we understand, shortly to be published by the Liunncan 

 Society of London in its Transactions. — Edit. 



