717 
A Memoir, entitled “ A Second Geological Survey of Russia in 
Europe,” by Roderick Impey Murchison, Esq., Pres. G.S., F.R.S., 
M. E. de Verneuil, Member of the Geological Society of France, 
and Count Keyserling, was then commenced. 
April 20.—Alexander John Sutherland, M.D., Fludyer Street, 
Westminster, was elected a Fellow of this Society. 
The reading of the Memoir on Russia commenced on the 6th of 
April was resumed and concluded. 
With the exception of a sketch of the Ural Mountains, to be 
given in a subsequent memoir, and of two short notices previously 
read, on the Freezing Cave of Iltetzkaya Zatchita, and on the 
« Tchornoi Zem,” or Black Earth*, the following abstract contains 
the chief results of a second examination of Russia in Europe. 
Following the same method as in the account of their first ex- 
amination, the authors describe the depositary strata in ascending 
order, successively adding to or correcting their previous know- 
ledge of each mass of deposits. 
Silurian Rocks.—The boundaries of these the most ancient fossil- 
iferous strata are more correctly defined than last year, and new 
localities are cited. The lowest subdivisions of blue shale and un- 
gulite grit, which were previously spoken of in certain inland spots: 
only, are now described in the sea-cliffs of the Baltic between 
Reval and Narva, as well as on the banks of the rivers Narva and 
Luga, in which situations, as in the tracts S. and S.E. of St. Peters- 
burgh, they constitute the inferior masses or representatives of the 
Lower Silurian Rocks. 
The Upper Silurian Rocks, chiefly composed of thin-bedded lime- 
stone, occupy the summits of the coast-cliffs in question, and the 
platform on which the river Narva flows from the lake Peicpus to a 
chasm worn by its own action, where it constitutes the picturesque 
falls above the Castle of Narva. It is believed by the authors that. 
this water-fall has receded (like those of Niagara, in America, and. 
other places,) in consequence of a solid tabular rock overlying less. 
coherent strata, which have been undermined and have cccasioned 
the subsidence of the superior layers. In addition, however, to 
these conditions, the wearing away of the vertical cliffs of the Baltic. 
and the retrocession of the falls of the Narva, are supposed, by the 
authors, to have been accelerated by another cause, viz. the direc- 
tion of the symmetrical joints in the overlying limestone. These 
joints present a number of salient and re-entering angles which are 
exposed on the surface of the impending cliffs, and when the softer 
supporting strata have been partially excavated, the dividing lines 
of these natural joints facilitate the fall of the calcareous beds into 
the abyss below. 
Besides the chief masses of limestone which extend over a con- 
siderable tract in the province of Esthonia, (including the Isles of 
Oesel and Dago,) the authors advert to a separate tract near the 
* See Proceedings, anté, pp. 712-714. 
