ii PROCEEDINGS OF THE GEOLOGICAL SOCIETV. [vol. lxxvi, 



A Lecture was then 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 first 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 denuda- 

 tion in a region which is somewhat inaccessible, or where the sur- 

 face 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 photographic 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-photo- 

 graphs, 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 then* general sculpture is 

 regarded as belonging to a former period of great precipitation. 

 In arid country, where the underlying rock is laid bare, the aero- 

 plane camera often shows the general geological structure of the 

 district. 



The lacustrine deposits of the Jordan Valley and then- weathering 

 was shown, and also the form of the drainage-channels running 

 down into the main valley. The depression of the Dead Sea with 

 reference to the surrounding country has resulted in the formation 

 of canons in many places. Some evidences of faulting at different 

 periods can be distinguished. 



The Jordan at present forms an interesting study in river- 

 development, and many of its main features were demonstrated. 

 The relation of the Jordan to the Orontes has been considered, 

 and an aeroplane photographic survey of the country between the 

 two rivers indicates that the Jordan probably originated in 

 Northern Syria in earlier times. The Syrian portion of the stream 

 has been captured by the younger Orontes, and this has had a 

 very important effect on the whole topography of the Jordan 

 Valley. 



A further study of the aeroplane photographs already taken, and 

 of the maps made from them, may throw much new light on the 



