178 Scientific Jntelligence — Geology and Geography. 



2- Dctrrmination of the Amount of Depression of the Dead Sea below 



the level of the Mediterranean In an article published in the 29th 



vol. of this Journal, p. 96, we detailed, at considerable length, the 

 various conclusions regarding this depression deduced from the ob- 

 servations and experiments of Schubert, Moore and Beek, Bertou 

 and Russegger. Since that time its amount has been estimated at 

 1200 feet from data obtained by the late Sir Daniel Wilkie. We 

 :ire glad to find, by the following remarks contained in Mr Hamil- 

 ton's address to the Geographical Society of London, that this in- 

 teresting problem has now been completely and satisfactorily solved 

 by Lieutenant Symonds of the Royal Engineers : — " This officer, 

 during the last year, carried a line of levels across from J.; "'■i. to the 

 Dead Sea by two different routes ; and the results, corresponding to 

 within an insignificant fraction, give 1311.9 feet for the depression 

 of the Dead Sea below the level of the Mediterranean, being a very 

 few feet less than that given by M. Bertou. Lieutenant Symonds, 

 by the same operations, found the level of the Lake of Tiberias to 

 be only 328 feet below that of the Mediterranean, making an in- 

 clination of nearly 1000 feet between this lake and the Dead Sea, 

 a distance of about 70 miles." 



3. On the Grooves and Polished Surfaces at the contaetof Ancient Se- 

 condary Strata. — Professor Rog'ers, at a late meeting* of the As- 

 sociation of American Geologists, made some remarks respecting 

 the grooved and polished surfaces at the contact of ancient se- 

 condary strata. He thinks he has seen unequivocal instances of 

 these in Pennsylvania. Their production, at periods when the 

 earth's temperature was manifestly incompatible with the exist- 

 ence of ice, would seem to demonstrate that angular detrital 

 matter, urged by water, is able of itself to score and polish the 

 surfaces of rocks. 



Professor W. B. Rogers continued the illustration of this sub- 

 ject, by calling attention particularly to the evidences of ancient 

 denudation and drifting action, so strikingly displayed along the 

 place of junction of the Oriskauy sandstone (Formation VII., of 

 the Reports), and the subjacent limestones Formation VI.). 

 In many districts the limestone has been irregularly denuded, 

 and even to a great extent removed ; and at the same time 

 fragments of the limestone and fossils, water-worn and blended 

 with coarse sand and gravel, have been accumulated to form 

 the lower beds of the Oriskany rock. The rapid fluctuation 

 in thickness of the upper limestones, as witnessed in Virginia, 

 Pennsylvania, and Western New York (near Black Rock, for 

 example), Professor R. ascribed lather to the irregular force of 



