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II.—Remarks on Prof. Bonney's paper “On the Crystalline Schists and their Relation to the Mesozoic Rocks in the Lepontine Alps.”
Published online by Cambridge University Press: 01 May 2009
Extract
I Venture to offer some remarks on the above-mentioned paper of Prof. Bonney, which appeared in the Quarterly Journal of the Geological Society for May, 1890 (vol. xlvi. pp. 187–240). As the result of ten years' geological researches in the St. Gothard district, I have become familiar with most of the statements and arguments brought forward by Prof. Bonney; many of them, I am glad to see, agree with my own observations and views, already made known in official and other publications; others, however, I feel bound to dispute.
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page 6 note 1 It will, we are sure, gratify our readers to learn that Dr. Stapff, the writer of the present article, was the eminent engineer of the St. Gothard tunnel. By accident Prof. Bonney has referred to him in the Quart. Journ. Geol. Soc. 1890, vol. xlvi. p. 196, as “the late Dr. Stapf” (for Stapf read Stapff). We are glad to he able to state that Dr. Stapff is alive and well.—Edit. Geol. Mag.Google Scholar
page 7 note 1 I am well aware that these grains and cylinders in the Nufenen schists are usually considered to be couseranite; but the existing chemical analyses allow them to be equally as well regarded as f. i. prehnite, and this interpretation is not contradicted by Prof. Bonney's microscopic analysis, though the shape of the prisms does not agree with the usual habit and mode of occurrence of prehnite.
Comparative analyses:—
I observed the hydraulic character of the Nufenen schists whilst searching for hydraulic lime in the neighbourhood of Airolo, and made some laboratory tests with them.
page 8 note 1 These and other intercalations of special geological interest have been purposely very prominently marked on the profit geologique in order to attract attention to them. For exact measures and details refer to my record: “Geologische Tabellen und Durchschnitte, über den grossen Gotthardtunnel; Specialbeilage zu den Berichten des Schweizerischen Bundesrathes über den Gang der Gotthardbahnunternehmung, 1873–1882.”
page 11 note 1 Zeitsch. d.deutsch. geol. Gesellsch, 1879, p. 407.Google Scholar
page 14 note 1 Faint traces of structures, resembling those on No. 43, have also been lately noticed in a section of No. 47
page 17 note 1 As already mentioned by Prof. Bonney, (loc. cit. p. 198) hand-specimens of these St. Gothard rocks are preserved in the Mineralogical Collection of the British Museum (Xatural History), and sections, taken from the one marked No. 43, show precisely similar structures to those in the accompanying figure.—Edit. Geol. Mag.Google Scholar
page 17 note 2 There is no question here about graphitic mirrors on fissures.
page 18 note 1 “Piottino gneiss” means the uppermost beds which on Mount Piottino (Daziogrande) dip under the mica schist formation. Tessiner gneiss is an old term of Studer's, which refers to the nearly horizontal strata of gneiss along the Ticino, Near the railway station Claro they abruptly assume a shurp southward dip, and are then overlaid by a newer gneiss formation (See pls. ix. and x. of the map and Explanation of the same in deutsch, Zeits. d.. geol. Gesells. 1884, vol. xxxvi.,Google Scholar also Jahrb, Neues. f. Mineral., 1882, vol. i. p. 72, where also the relation between the parallel structure and the stratification of the Piottino gneiss is treated of.Google Scholar