Reports & Proceedings — Geological Society of London. 571 



eastern slope of the ridge between Le Hocq and Pontac, and the 



section, facing northwards, shows the following succession of beds 



from above downwards : — 



Thickness in feet inches. 



1. Earthy loam, with a layer of rubble . . . .40 



2. Stiff brownish-red clay ....... 1 



3. Yellow loamy clay, containing water-worn pebbles and 



angular fragments ....... 3 4 



4. Coarse brown sand ....... 3 6 



5. Water- worn pebbles, closely packed in a matrix of coarse 



brown sand ......... 4 6 



The rock beneath is fine red granite. The section is terminated at 

 its western end by sloping rock, and there, between the rock and the 

 lower beds, is a layer of stiff brownish-yellow clay about 2 feet thick, 

 which is continued for a short distance under the bed of pebbles. 



The base of the section is about 50 feet above mean sea-level. 



The pebbles in both the upper and the lower beds are mostly of the 

 fine red granite of the locality, but there are some of diabase and of 

 quartzite, as well as a few of flint. Flint is, of course, foreign to 

 the island, but there are many flint pebbles on the recent beaches, 

 especially on the north-eastern coast. Flint pebbles have also been 

 found in at least two low-level raised beaches, and flint pebbles and 

 fragments have been noticed in the yellow clay. Pebbles and fragments 

 of Devonian shale have also been found in what appears to be a 

 remaining fragment of a raised beach on the south-western coast. 



Colonel Warton recently pointed out a raised beach, not previously 

 noticed, in the railway cutting near the Eastern Railway station. 

 This is also on the south side of the island, not far from the coast. 



Its base is about 55 feet above mean sea-level, and it is covered by 

 a thick bed of yellow loamy clay. 



2. "On Tachylyte Veins and Assimilation Phenomena in the 

 Granite of Parijs (Orange Free State)." By Professor S. James 

 Shand, D.Sc, F.G.S., Stellenbosch, South Africa. 



The district described is the neighbourhood of Parijs Township, 

 which is situated on the Vaal River and lies upon the northern portion 

 of the Vredefort granite-mass. 



The so-called ' granite ' near Parijs is a red and grey streaky gneiss, 

 often traversed, both parallel to and across the foliation, by veins 

 of red pegmatite ; these are of a later period of consolidation than 

 the rest of the rock. The author concludes from field-evidence that 

 the grey facies of the gneiss results from assimilation of the country 

 rock by an ascending magma, while the red facies represents the 

 residual portion of the same magma. 



The special interest of the district, however, lies not so much in 

 the granite as in a system of tachylytic veins which everywhere 

 intersects the granitic rocks. These veins range from a fraction of 

 an inch to 2 feet in thickness, but in the thicker veins there are 

 numerous inclusions of the country rock. They are irregular in 

 form, thickness, and direction, and are due to the intrusion of 

 a basic magma which underlay the district. The author describes 

 the microscopic characters of these tachylytes, and comments on their 



