238 PROF. T. G. BONNE Y ON CRYSTALLINE SCHISTS AND THEIR 



In continuatiou of his remarks Dr. Geikie complimented the 

 Author on his courage in returning to this difficult ground, but 

 notwithstanding the arguments so skilfully brought forward that 

 evening he was not convinced of an error on the part of the Swiss 

 geologists. Even the Author's own sections gave some countenance 

 to their views, since the dark garnetiferous schists might quite well 

 be part of the same series as the JBelemnite-schists. In metamorphic 

 regions there must be some line, on one side of which fossils are 

 recognizable, on the other not so. In the Alps, as Heim and 

 his associates contend, the Belemnite-schists, which have become 

 markedly crystalline, may be less altered portions of masses from 

 which all trace of fossils has been generally obliterated. 



Mr. EccLES declined to say anything with respect to the Andermatt 

 section. As to the Yal-Piora schists, and their relations to the 

 rauchwacke, he fully concurred with the Author's views thereon, and 

 especially in respect of the frequently changing position of the 

 rauchwacke in relation to these schists. He criticized the sug- 

 gestions of Von Eritsch with reference to this series of beds, and 

 pointed out the curious position of the calc-mica schists on this 



(and the translation appears to me to represent accurately the sense of the 

 original German) justify the position which I have taken up in this paper. 

 Indeed, I find it -very diificult to reconcile perfectly the present letter with 

 that essaj^ or the published statements of Swiss geologists ; and if I might 

 venture to put my view of the case rather bluntly, I should be obliged to say, 

 " It is not so much that I have misunderstood you as that you have mis- 

 understood Nature." Hence, to contend further on the point, whether Dr. Heim 

 did or did not include rocks of Jurassic age among crystalline schists, is needless, 

 for if I am right as to the following matters, the dispute is one "-de land 

 cwprindr I beg leave, then, to observe that : — 



(1) Carboniferous rocks are only incidentally mentioned in my paper, so 

 that I fail to see the full force of Dr. Heim's reference to such rocks in another 

 part of the Alps. Some of these, however, I have examined, and think I know 

 them well enough to demur to Dr. Heim's statements concerning them. I have 

 seen, in the Berne Museum, the specimen with "the Calamite-like stem." 

 When this rock is proved to be a gneiss I shall be prepared to consider the 

 propriety of extending this name to the Gres Fehpathiqiie of Normandy, or 

 that of mica-schist to some rocks of Carboniferous age at Vernayaz, in Canton 

 Valais, or of calling the Torridon Sandstone of Scotland a granite. 



(2) One of the main purposes of the present paper is to prove that a great 

 group of true crystalline schists (some of which contain garnets, staurolites, 

 &c.) does exist in the Lepontine Alps, and that in these Belemnites or other 

 fossils never occur. 



(3) Also to prove that the supposed infra-position of the Eauchwacke 

 (Triassic) to this group is the result of misinterpretations of the stratigraphical 

 evidence, and that this Eauchwacke (a comparatively unaltered rock) contains 

 fragments of more than one member of the above-named group of schists. 



(4) Also to prove that the schistose (Jurassic) rocks, in which Belemnites 

 and other fossils occur, only resemble superficially the above crystalline 

 schists, and do not contain (not to mention other minerals) authigenous 

 garnets or staurolites, the minerals which have been taken for these being 

 certain hydrous silicates, the presence of which does not indicate any extreme 

 metamorphism. 



Hence, in my opinion, Dr. Heim in his letter does not adduce any fresh 

 evidence, but only reiterates the mistakes, as they appear to me, in correction 

 of which my paper was written. — T. G. Bonney. 



