318 Notices of Memoirs — The Oilfields of Egypt. 



of lime. Mr. Lucas contributes a chapter on the solubilities of these 

 two substances in -water and saline solutions, in which he shows that 

 the relative solubility of gypsum increases up to a certain point as 

 the salinity increases; and Dr. Hume points out that the under- 

 ground waters at Jemsa have approximately the composition most 

 favourable for the solution of gypsum. There appears to be strong 

 reason for believing that the circulation of water in the saliferous 

 formation has brought about great changes in the nature and distri- 

 bution of the original materials. 



Salt which has been met with in several bores does not occur in 

 one central core as in the Roumanian fields, but is interstratified 

 with shales and gypsum. It is best developed in the minor anti- 

 clines, and "Professor Mrazec was strongly impressed with the idea 

 that these strata [the salt-beds] were derived by a leading action 

 from salty clays, similar to those well developed at the surface, 

 whereas beds of salt have never been noted on the large scale in the 

 above ground observations". Dr. Hume suggests that the saliferous 

 deposits were formed in a slowly sinking area into which sea-water 

 could gain access, that the evaporation over this area was sufficient 

 to cause the precipitation of gypsum and salt, and that while this 

 was going on streams were bringing down clay and calcareous 

 matter from the surrounding land. 



The similarity in many respects of this formation to that of the 

 Roumanian oilfields is referred to. May we not extend the 

 correlation? Aturia aturi is a characteristic fossil of the " Schlier" 

 which, according to Suess 1 and others, includes the Carpathian salt- 

 beds, and probably also those of Armenia and Azerbigan, of the 

 Iranian tableland as far as Khorasan, of the valley of the Tigris, 

 and of the coast of the Persian Gulf. Doubt may exist as to the 

 precise correlation of all these saliferous formations which, as Suess 

 says, " afford us the spectacle of a great expiring sea " ; but it seems 

 clear that, both as regards age and mode of formation, the deposits of 

 the Egyptian oilfield are closely allied to them ; and it is with them 

 that some of the most important oilfields of the world are intimately 

 associated. 



No definite opinion is expressed as to the origin of the petroleum, 

 but the porous limestone (Jemsa) and the Nubian Sandstone 

 (Rarquada) are regarded as reservoir rocks. Indications of oil 

 are most conspicuous on both sides of the Gulf of Suez, and as the 

 overfolding of the anticlines is directed towards the Gulf, it is 

 suggested that the post-Miocene stresses probably reached their 

 greatest intensity in this region, and may therefore have forced the 

 oil into any rocks in the neighbourhood capable of containing it. 



No detailed records of bores are given, except the four at Jemsa, 

 and no statistics of production. It is to be regretted that so much 

 secrecy should be considered necessary by those engaged in controlling 

 and developing the economical resources of a country, and very 

 doubtful whether it is not carried much further than is required for 

 commercial purposes. Rivals generally find out sufficient for their 

 purpose, and the progress of science is, therefore, often unnecessarily 

 1 Face of the Earth, vol. i, p. 309, English translation. 



