﻿part 3] 



THE PSEUDOTACHYLYTE OP PARIJS. 



217 



to escape through a small hole in a granite stopper, will at once 

 recur to the memory. Here is not only a possible source of the 

 vein -material, but an explanation of the high temperature to 

 the action of which that material testifies. I hardly dare offer 

 this as a serious hypothesis, since it takes us away from known 

 causes altogether; but, when one is dealing with an extraordinary 

 phenomenon, no possibility is too extraordinary to be worthy of 

 consideration. 



In brief, the material of the pseudotachylyte seems to be 

 melted granite — this is indicated by the chemical characters, and 

 is consistent with the microscopical evidence ; it behaves towards 

 the granite like an igneous intrusion — this is established by the 

 field -observations. The source of the heat and the mechanics of 

 the intrusive process remain obscure. 



IX. Literature. 



F. H. Hatch. — ' A Geological Map of the Transvaal ' in Hatch & Corstorphine's 



' Geology of South Africa' 2nd ed. 1909. 



G. A. F. Molengraaff. — ' Remarks on the Vredefort Mountain-Land ' Trans. 



Geol. Soc. S. Africa, vol. vi (1903) pp. 20-26. 

 F. W. Penny. — ' The Relationship of the Vredefort Granite to the Witwaters- 



rand System ' Q. J. G. S. vol. lxx (1914) pp. 328-34. 

 W. King & R. B. Foote. — ' On the Geological Structure of the Districts of 



Trichinopoly, Salem, &c.' Mem. Geol. Surv. India, vol. iv (1864) pp. 223-377. 

 T H. Holland. — ' The Charnockite Series ' Mem. Geol. Surv. India, vol. xxviii 



(1900). 



B. N. Peach & others. — ' The Geological Structure of the North- West High- 



lands of Scotland ' Mem. Geol. Surv. 1907. 

 A. Harker. — 'The Tertiary Igneous Rocks of Skye ' Mem. Geol. Surv. 1904, 

 p. 167. 



C. T. Clough, H. B. Maufe, & E. B. Bailey. — ' The Cauldron Subsidence 



of Glen Coe ' Q. J. G. S. vol. lxv (1909) pp. 611-76. 



H. Backlund. — ' Algunas Observaciones sobre Rocas Notables provenientes 



de Olavarria ' Direccion General de Minas, Boletin No. 2, Buenos Aires, 

 1913. 



Appendix [September 1916]. 



Some fresh Analyses of the Granite and Pseudotachylyte 

 of Parijs, made by Dr. H. F. Harwood. 



Through the kind mediation of Dr. Arthur Holmes, Dr. H. F. 

 Harwood, of the Imperial College of Science & Technology, has 

 lately been induced to undertake . the analysis of the granite and 

 pseudotachylyte, in- order to settle the question of the origin of 

 the latter. For this purpose I supplied him with : — 



(1) the residue of the material already analysed by Mr. R. A. Page and 



described by me in the foregoing pages, and 



(2) a large block from the locality shown in PI. XVII, fig. 1, consist- 



ing of part of the tachylyte vein (2 a) and part of the granite 

 wall (2 b). 



