ANNIVERSARY ADDRESS OF THE PRESIDENT. 183 



The Secondary Rocks. 



The Trias, so largely developed in other parts of Europe, is un- 

 known in European Russia. 



It is remarkable that, except one member of the oolitic series, the 

 whole of the secondary formations between the Permian and Creta- 

 ceous groups should be wanting in Russia, and that with the ex- 

 ception of a very limited and even doubtful oolitic deposit in Vir- 

 ginia, not a trace of them should have been found from the Atlantic 

 to the Mississippi, and even as far west from that river as any geo- 

 logist has yet penetrated. Professor Rogers rests his determination 

 of this deposit in Virginia as belonging to the lower part of the 

 oolitic series, solely on the striking resemblance as a group of cer- 

 tain plants, accompanying a bed of coal which it contains, to those 

 which are found associated with the oolite coal of Brora, Whitby, 

 and other European localities. He says that, " judging by litholo- 

 gical indications alone, perhaps no more probable conclusion would 

 have been reached on the subject than that of the able geologists 

 Mr. Maclure and Mr. R. C. Taylor, the former of whom assigned 

 this deposit, consisting of slates and of coarse grits composed of the 

 materials of granite so little worn as to have the aspect of that rock 

 in a decomposing state, and resting upon gneiss, and without any 

 calcareous bed, to the period of the Old Red Sandstone ; the latter 

 to the " transition carboniferous deposits." If it be true, that in the 

 Alps species of plants identical with those of the Carboniferous pe- 

 riod have been found in undoubted Jurassic beds, it becomes doubt- 

 ful whether the mere " resemblance as a group" of the plants in the 

 Virginian beds is conclusive evidence, opposed as it is by the litho- 

 logical character of the deposit, and the most remarkable circum- 

 stance of the entire absence of the oolitic series in any other part of 

 the American continent. In a letter I had from Mr. Lyell, who 

 last December passed through Virginia, he informs me that he had 

 seen some specimens of coal plants and of ichthyolites from this de- 

 posit, which throw some doubt on its being of the oolitic age, espe- 

 cially when he compares the list with those from Connecticut, and 

 that he intends to return to the spot in April next, in the hope of 

 being able to determine their true age more precisely. 



The only member of the oolitic series found in Russia is a repre- 

 sentative of our Oxford clay and the beds immediately associated 

 with it, — that which the French geologists call the Terrain Oxfordien. 

 Nor, where these Jurassic beds occur, do they occupy any great extent 

 of surface, but are in detached spots, at remote intervals, in isolated 

 basins, patches or stripes. They are composed of slightly coherent 

 dark-coloured pyritous shales, sands and calcareous concretions, 

 sandstones and marlstones, very seldom solid calcareous beds, and 

 throughout with a surprising uniformity of character. Tiiey are 

 besides of little vertical thickness compared to tlie same series in 

 other countries of Europe, tlie most considerable not exceeding 400 

 feet. They form low masses, which no doubt were at one time more 

 connected, and have been subjected to powerful denuding causes. 



