566 Reports & Proceedings — Geological Society of London. 



occurrences of magnesite in other countries and its uses. The Bulong 

 district lies in a complex of basic and ultrabasic greenstones, the most 

 prominent members of which are serpentines and amphibolized 

 gabbros, apparently local differentiations of a highly basic magma, 

 intruded as one mass. These are traversed by a number of porphyrite 

 dykes and are in contact with an area of sheared sediments, including 

 slates and pebble beds. The magnesite occurs for the most part as 

 irregular veins in the serpentine and is doubtless formed by the 

 ordinary alteration-processes of that rock. It is comparatively free 

 from lime, but contains moderate amounts of silica and iron. The 

 amount of the mineral present is now wholly uncertain owing to the 

 irregular nature of the deposit and the thick detrital covering, but it 

 appears to be very large, and ranges in quality to 90 or even 95 per 

 cent MgC0 3 . 



:r:k::fo:r.ts j*ji<tjd peoceedings. 



I. — Geological Society or London. 



November 5, 1919.— Mr. G. "W. Lam pi ugh, F.R.S., President, in the 



Chair. 



A lecture was delivered by Hugh Hamshaw Thomas, M.A., 

 F.G.S., "On some Features in the Topography and Geological 

 History of Palestine," illustrated by aeroplane photographs taken 

 during the War. 



The lecturer observed that a perfectly new method of illustrating 

 and investigating some branches of physical geology is afforded by 

 aeroplane photography. It seems firstly to illustrate in a very 

 striking and convincing form many geological phenomena, such as 

 the structure of a volcano or the land-forms resulting from erosion, 

 and may be of value in the teaching of the science. In the second 

 place it may, in certain circumstances, become a valuable means of 

 research, especially in connexion with river-development or 

 denudation in a region which is somewhat inaccessible, or where the 

 surface of the ground is very complicated and the main features are 

 obscured by a mass of less important detail. The lecture dealt 

 principally with the illustration of the physical features of Palestine, 

 and owed its origin to the systematic photo survey made over 

 Central Palestine during the War. The photographs were originally 

 taken for the purpose of constructing detailed maps, and the 

 examples shown had been selected from a large mass of similar 

 material which still exists in the form of negatives, and these may 

 eventually become available in this country for further study and 

 research. The demarcation of the coastal plain from the foot-hills 

 of the upland country is often well shown by oblique air-photographs, 

 and the weathering-out of the flat alluvial ground by the winter 

 rains to give characteristic wadis is clearly seen. In the central 

 hill-country the terraced hills show the relation of the scenery to 

 the underlying rock, but their general sculpture is regarded as 

 belonging to a former period of great precipitation. In arid 



