ANNIYERSARY ADDRESS OF THE PRESIDENT. Iv 



Petra and the almost equally celebrated sandstones of Nubia. 

 In the two latter regions they are associated with conglome- 

 rates ; but, whilst the relative antiquity of the whole of this thick 

 series bears importantly on many of the most interesting questions 

 respecting the conformation of this corner of Asia and the neighbour- 

 ing part of Africa, the almost total absence of fossils has hitherto left 

 their identification very uncertain. By a singular chance, I am 

 enabled apparently to verify the statement of M. Lartet, that these 

 beds belong to the Cretaceous period. Some few months ago, our 

 late associate Mr. Majendie brought me a dark siliceous pebble, which, 

 on being broken, exhibited a beautifully sharp example of the charac- 

 teristic Lower Cretaceous shell Pecten quinquecostatus. The speci- 

 men was from an old collection, and appears to have been grouped 

 with the well-known siliceous pebbles which are picked up in num- 

 bers in the deserts about Syene, where the Nubian conglomerates 

 either crop out or have been denuded off ; and Mr. Etheridge in- 

 forms me that he has never known the fossil to occur in the upper 

 or flinty beds of the chalk. 



One of the most curious problems in physical geography to be 

 solved by geological inquiry is the true nature of that long meridi- 

 onal line of valley and, in part, of deep depression which extends 

 from Akabah, on the south, through the Dead Sea, the valley of the 

 Jordan, the lake of Tiberias, and the base of the Lebanon, and 

 which, if prolonged (as appears to be consistent with facts) through 

 the rich plain of the Bekaa, and by the course of the Upper Orontes, 

 to the lake of Antioch, occupies some 500 miles in length. The 

 observations of late years have proved what was little expected by 

 the travellers of the earlier part of the present century — that the 

 level of the Dead Sea is no less than 1292 feet* below the level of 

 the Mediterranean ; and most of the hypotheses which have for- 

 merly been suggested to account for the formation of this remark- 

 able valley must be rejected or modified in consequence of the 

 measurements of the levels, which have now been made with 

 undoubted exactness. When first the existence of the line of val- 

 leys (the Arabah) extending from the southern end of the Dead Sea 

 to the Eed Sea at Akabah, was made known by Burckhardt, it was 

 natural to found upon it a theory that the river Jordan had once 

 flowed through the whole line of valley to an embouchure at the 

 Eed Sea ; and the comparatively low watershed which, south of 

 Ain Ghurundel, divides the run of waters flovnng to Akabah from 

 that which takes its course to the Dead Sea was attributed to a 

 slight subsequent change of the levels over a limited tract. But the 

 subsequent discovery of the enormous depression of the lake and 



* The earlier observations of De Bertou, Eussegger, and von Wildenbruch 

 were all considerably in excess, giving a mean of 1416-7 feet. Capt. Symonds 

 reduced it to 1312*2 feet below the sea ; and the report of Sir Henry James 

 made it 1292 feet on the 12th March, 1865. This latter result, obtained by the 

 party under Captain Wilson, is stated to be lower by 2^ feet than the occa- 

 sional level of the water, and 6 feet higher than it sometimes stands in the 

 early summer ; and it coincides marveUously with the level given by Lieut. 

 Yignes of the French navy, viz. 392 met. or 1286 feet. 



