608 PROF. J. W. GREGORY ON [Nov. I9II, 



Though important earth-movements in this area have apparently 

 happened as late as the Pleistocene, they appear to have ceased 

 before historic or even Palaeolithic times. The sea-level cannot have 

 been notably altered at Derna since the date of the Palaeolithic 

 camp at Bonmansur. I saw no recent raised beaches along the 

 coast ; and there are no distinct signs of recent subsidence. Stacey 

 has referred to modern subsidences at Benghazi, while P. W. & 

 H. W. Beechey have referred to indications of the recent advance 

 of the sea seen during their surveys of the ancient Greek ports of 

 Tokra, Ptolemeta, and Mersa Susa. The evidence even at these 

 localities seems, however, to show that there has been no marked 

 displacement of the shore-line since classical times. The sea has 

 no doubt encroached at Benghazi and Mersa Susa, 1 but its advance 

 at both places may be explained by ordinary coastal abrasion, with 

 subsidences due to solution of limestone. The Glycimeris Limestones 

 at Benghazi and Ptolemeta would suggest a slight emergence of the 

 land, and not a subsidence ; but they may have been storm-beaches 

 and dunes subsequently separated from the sea by silting. 2 



The ancient wharf at Ptolemeta, according to theBeecheys' map, 

 is now 150 yards from the shore-line, but the intervening beach is 

 probably due to silting. At Mersa Susa there has been a slight 

 encroachment of the sea near the ancient theatre ; it has, on the 

 other hand, receded at the old harbour, probably through silting, 

 for the ruins of the ancient piers appear to stand at exactly their 

 original level. The maps of Mersa Susa, Tokra and Ptolemeta, 

 revised from the Admiralty Chart by Smith & Porcher, 3 show that 

 there has been no serious change of sea-level since the building 

 of those ancient towns by the Greek coJonists, who began the 

 colonization of Cyreuaica about 620 b.c. 



VI. The Wadis, and Possible Variations in 

 Pleistocene Climate. 



The preceding evidence shows that Cyrenaica is a block of Eocene, 

 Oligocene, and Miocene limestones, which was uplifted in Upper 

 Miocene times (if the Gubah Limestones be Helvetian) and sub- 

 sequently isolated by the foundering of the surrounding areas. The 

 first subsidences in the Lower or Middle Pliocene formed the Tokra 

 scarp and the Gulf of Syrtis, for the Cretaceous rocks — as at Tripoli 

 — are separated from the sea only by Pleistocene deposits. The 



1 The most definite evidence of the advance of the eea is at Benghazi. 

 G. B. Stacey writing in 1867 quoted Arab testimony that horse races had been 

 held 50 years previously, inside the reef where the water was now 5 feet deep ; 

 and he states that the ruins of buildings were to be seen at low water on the 

 reef: Q. J. G. S. vol. xxiii (1867) p. 384. The present brackishness of the 

 wells at Mersa Susa has been regarded as evidence of encroachment of the 

 sea or subsidence of the land by George Dennis, ' On Recent Excavations 

 in the Greek Cemeteries of the Cyrenaica' Trans. R. Soc. Lit. ser. 2, vol. ix 

 (1870) p. 144. 



2 That the shore has receded at Benghazi is remarked by F. B. Goddard, 

 ' Researches in the Cyrenaica ' Amer. Journ. Philology, vol. v, No. 17 (1884) 

 p. 51. 



3 ' History of the Recent Discoveries at Cyrene ' 1864, pi. i. 



