No CrossRef data available.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
Published online by Cambridge University Press: 01 May 2009
In a paper read before the Geological Society of London, in 1889, I contended that the biotite of the gneisses and schists of Malvern had been produced out of hornblende through the intermediate form of chlorite. As this mineral change is of capital importance in explaining the origin of the Malvern schists, I made it one of the principal topics of the paper, and I trusted that the evidence I offered in support of it would be considered adequate. The further communication on the Malvern rocks, which I read on April 26th of the present year, assumed the adequacy of this proof. I found, however, that in certain quarters some scepticism on the point still existed, and it was suggested that I had overlooked some of the chemical difficulties which seemed to forbid the acceptance of my view. I therefore crave permission to reply to this objection in these pages ; and I desire, at the same time, to point out that since the reading of my paper in 1889, the production of biotite from chlorite has been affirmed by several writers of admitted authority.
page 535 note 1 On the Production of Secondary Minerals at Shear-zones in the Crystalline Rocks of the Hills, Malvern, Q.J.G.S., August, 1889, p. 475.Google Scholar
page 535 note 2 Einige fragen zür Lösung des Problems der Krystallinischen Shiefer, nebst beiträgen zu deren beautwortung aus dem Paläozoicum; Compte Rendu, p. 180.
page 535 note 3 This date is of course prior to 1889, but Prof. Lossen's paper was not known to me till after mine had been sent in.
page 535 note 4 Sur 1' Origine des Terrains Cristallins Primitifs; Compte Rendu, p. 58.
page 535 note 5 Zeits. d. deutsch. geol. Ges. 1890, xlii. p. 450.Google Scholar
page 535 note 6 Neues Jahrb. v. Beilage-Band (1887), p. 643.Google Scholar
page 537 note 1 This rock contains too much potash for a normal diorite. As a large proportion of the felspar is plagioclase, and the silica percentage is only 47, it can hardly be a syenite.
page 537 note 2 Discussed in Quart. Journ. Geol. Soc. (1889), pp. 482–487, 499.Google Scholar
page 537 note 3 Ibid. p. 482.