276 Correspondence — Mr. H. H. Iloiiorth. 



centre, producing a spherulite, which, but for the occurrence of 

 intermediate stages, might be supposed to have originated entirely 

 by divergent growth. The authors give details of the appearances 

 presented by intermediate stages of growth. 



The prevailing type of spherulite, both in Lipari and Vulcano, 

 shows in section a dusky fibrous central area, which may possess 

 concentric as well as radial structure, surrounded by an irregular 

 brown cloudy zone of various width. The authors' studies lead 

 them to the conclusion that this type owes its characters to the dual 

 mode of growth, and therefore to the original presence of vesicles 

 in the rock. Commonly the process of infilling does not go so far 

 as this ; on the ends of the felspar fibres plates of tridymite are 

 deposited, and this seems to close the growth. It is clear that the 

 litliophysal structui-e of the Lipari obsidians was formed during the 

 cooling of the mass, and not by subsequent amygdaloidal infilling of 

 vesicles. 



The authors discuss the effect of confined vapours on such rocks 

 as those forming the subject of the paper, noting that these vapours 

 inajf be kept at a high temperature lor a considerable time, each 

 vesicle thus becoming a sphere of hydrothermal action ; so that if 

 the surrounding glass remains at a temperature little below its 

 fusion -point, crystallization will be promoted in it, and at the same 

 time the action of the vapour in the vesicle will produce reactions on 

 its walls. 



An Appendix, by Prof. Cole, treats of the lithophyses and hollow 

 spherulites of altered rocks. While admitting the presence of true 

 lithophyses in many of the Welsh lavas, he is not prepared to 

 abandon a former suggestion that the interspaces between successive 

 coats of the Conway lithophyses result from alteration of a formerly 

 solid mass. In the lavas of Esgair-felen and near the Wrekin he has 

 no doubt as to the production of " hollow spherulites " by ordinary 

 processes of decay. The typical Continental pyromerides are truly 

 spherulitic, as is much of the Wrekin lava. In the latter case and 

 that of the rocks of Boule}^ Bay it will be difficult to distinguish 

 between infilled primary and secondary cavities. 



cos-iEaiEsi^oisrnDEisrcin]. 



"THE EECENT ELEVATION OF THE HIMALAYAS." 

 Sir, — The nummulitic limestones occurring in the Hundes Valley 

 show that in Eocene times the ground where the Himalayas now 

 stand was covered by the sea. This is, I believe, admitted by Dr. 

 Blanford. In the Manual of Indian Geology for which he and IMr. 

 Medlicott are responsible he goes further, and expressly says that 

 "at the close of the Miocene epoch no such mountain harrier as exists 

 at present separated the Indian peninsrda frorn Central Asia " (op. cit. 

 p. 586). The opinion of Dr. Blanford in 1878 therefore was that 

 the Himalayas are of post-Miocene origin. 



The superficial beds which contain the mammalian remains we 

 have been disputing about lie unconformably upon certain speckled 



