﻿Vol. 6 1.] PBOCEEDLNGS OF THE GEOLOGICAL SOCIETY. lxxxix 



sequence of the rocks in the south of Skye had been so completely 

 confirmed by the much more detailed work of Mr. Harker. The 

 admirably- constructed map on the wall, and the striking slides 

 shown on the screen, brought the whole scenery and geology vividly 

 before the eye, and he had to thank Mr. Harker for the very great 

 pleasure which the exhibit had given him. 



Prof. Watts congratulated Mr. Harker and Dr. Teall, on the 

 publication, on the 6-inch scale, of the most accurate and detailed 

 piece of igneous-rock mapping hitherto executed in the world. 



Dr. F. H. Hatch, in exhibiting lantern -slides of the 

 'Cullinan' diamond, said that the photographs were made by 

 Mr. E. H. V. Melvill, to illustrate a description of the stone which 

 Dr. Corstorphine and the exhibitor had received the permission of the 

 Directors of the Premier Company to make, and which they proposed 

 shortly to publish. The photographs showed the diamond from four 

 points of view and its actual size. The stone was a portion (probably 

 less than half) of a distorted octahedral crystal. As it now existed, 

 the stone was bounded by portions of four original octahedral 

 surfaces and by four cleavage-planes. The former showed in places 

 a slight curvature, a mammillary structure, striations, and tri- 

 angular pittings, while the cleavage-surfaces were distinguished by 

 greater regularity and smoothness. The stone weighed 3024f 

 carats. Its greatest linear dimension was 4 inches. It was of 

 remarkable purity for so large a stone, approaching ' blue-white ' 

 in colour. It was found at the beginning of the present year, in 

 the ' yellow ground ' of the Premier Mine, at a depth of 18 feet 

 below the surface. The Premier Mine was a true ' pipe,' situated 

 on the farm of Elandsfonfcein, 20 miles north-east of Pretoria 

 (Transvaal). 



Mr. A. P. Young said that he wished to know whether there was 

 marked adhesion of the matrix to any of the surfaces, and whether 

 the exhibitor could add anything on the subject of experiments 

 reported to prove the etching of diamond by the fused ' blue ground.' 



Dr. Hatch replied that the specimen had been cleaned in the 

 usual way with hydrofluoric acid, but there was no sign of the 

 surface having been etched in the manner suggested. 



The following communications were read : — 



1. ' Observations on some of the Loxonematidse, with Descriptions 

 of two New Species.' By Miss Jane Donald. (Communicated by 

 Prof. Theodore Groom, M.A., D.Sc., F.G.S.) 



2. ' On some Gasteropoda from the Silurian Rocks of Llan- 

 gadock (Caermarthenshire).' Bv Miss Jane Donald. (Communi- 

 cated by Prof. Theodore Groom, M.A., D.Sc, F.G.S.) 



VOL. LXI. q 



