ANNIVERSARY ADDRESS OF THE PRESIDENT. 11 



ancient districts, or of investigating analogous formations in foreign 

 lands, will turn to ' Siluria ' as a friend and guide. 



Physical Structure of Palestine. — An idea has obtained footing, 

 even in well-informed circles, that the geological structure of the 

 Holy Land is almost entirely unknown ; and our presumed ignorance 

 has been cited as one of the special reasons for promoting the pro- 

 posed exploration of Palestine. The partial knowledge which we 

 possess may, it is true, stimulate a desire for more ; and the numerous 

 subjects of interest which exist in those regions demand a more 

 thorough attention than has yet been accorded to them; but we 

 must not forget the important contributions, some of them a quarter 

 of a century old, of Dubois de Montpereux, of Russegger, Anderson, 

 Lartet, and others, to which has recently been added an unpretend- 

 ing but very readable volume by Prof. Oscar Praas, of Stuttgart *. 

 Happily breaking away from the fetters imposed by the halting frag- 

 mentary entries of a journal, the author starts from the crystalline 

 nucleus of the Sinai peninsula, and describes with the fervour of a 

 northern, to whom such sights are new, the naked charms of its bright 

 minerals and particoloured rocks, free from the encumbrance of soil 

 and of vegetation. The home of the turquoise, worked for some years 

 past by Major Macdonald, he describes as being in the cracks of the 

 porphyries of the Megarah valley, where that valued gem is associ- 

 ated with oxides of iron, especially of those kinds termed bean ore 

 and pisolitic ore, and would appear to have been deposited by the 

 same agencies. In the same {i. e. the northern) district of the Ser- 

 bal, as well as in the central group of the Hebran and el Schech, 

 the peculiar weathering of the granite is very observable, not only 

 as producing the most strange and fantastic forms, but as appearing 

 to proceed from the centre of the blocks towards the circumference, 

 and thus giving rise to rounded hollows which, somewhat enlarged 

 and modified by art, have served as the abodes of troglodyte hermits 

 in the early ages of Christianity. As the traveller passes over the 

 totally arid surfaces of granite, syenite, and porphyry, if there be 

 seen, in valley or on mountain-side, the bright green of an oasis, or 

 if water makes itself visible rising from the rocky fissures, it is almost 

 invariably where a portion of gneiss or mica-schist will be found in 

 close proximity, and where it has forced the liquid to the surface, 

 doubtless, by its foliated structure and greater freedom from vertical 

 planes of division. 



The mingled syenites, granites, and porphyries of Sinai form a 

 striking feature of the geological map published many years ago by 

 Eussegger ; but although these, with various other igneous rocks, are 

 shown to correspond with large masses of the same order in the 

 African deserts bordering the Gulf of Suez, and again with a number 

 of smaller protrusions in a line running northward towards the Dead 

 Sea, there is a great lack of further definite information. Dr. Praas 

 gives a picture of the frequency with which greenstone dykes cut 

 through the granite; on making the ascent of the Serbal, he 



* Aus dem Orient. Geologische Beobachtimgen am Nil, auf der Sinai-Halb- 

 insel und in Syrien, von Dr. Oscar Praas. Stuttgart, 1867. 



