46 report — 1842. 



ner in which every assistance was afforded ; and apologizing for his wish to condense 

 into a brief address the numberless topics to which he wished to have adverted, he 

 referred the assembly to the Proceedings of the Geological Society, and intimated 

 that a work and map descriptive of the geology of Russia would soon be offered to 

 the public. 



Contributions to a Geological Sketch of North Asia. By Adolphe Erman, 

 Professor at the University of Berlin. (Accompanied by a coloured Geo- 

 logical Sketch of the Land between long. 100° and 160° East from Paris, 

 lat. 51° and 63° North, and a Collection of 200 Geological Specimens.) 



In addition to a continued series of magnetical observations and other scientific 

 investigations, the author was led to notice a variety of interesting geological pheno- 

 mena in the country above defined. The volcano of Klioutchi (14,780 Paris feet in 

 height), with the streams of lava rushing down (to the height of 8000 feet), and the 

 clouds of steam of volcanic ashes and cinders, extending to the height of nearly four 

 English miles, was first noticed; and the author then presents a geographical sketch 

 of the Valley of the Lena, of the Aldan Mountains, and theMarikan belonging thereto, 

 and of the immense volcanic area of the Kamtschatkic peninsula. 



The borders of Lake Baikal consist of actual triturative conglomerate, alternating 

 with granite, and belonging to the coal formation. North-east of this lake is wide 

 table land 1600 feet above the sea, giving origin to the sources of the Lena, which 

 flows in a narrow regular valley, with mural cliffs, and having horizontal strata of 

 sandstone and marls, chiefly of red colour, often ripple-marked. This red formation 

 occurs also at Oust Kouck with salt and cellular (magnesigenous?) limestone. Near 

 Kirensk these sandstones foid round a boss of the same limestone in a purer state. 

 Near Jerbinsk this limestone, in lofty ranges, is largely cavernous, and in the caverns 

 (200 feet above the river) arc stalactites of ice, which also invests the walls and covers 

 the floor. Referring to his collection placed on the table, M. Erman here drew at- 

 tention to an Amphus in the red strata of the Lena, near Krywslouzk, and to the 

 probability of these red and variegated strata being of the geological age of the De- 

 vonian group. 



The Aldan Mountains (4000 Paris feet above the sea) show, on the right bank of 

 the river Aldan, vast limestone rocks of the same kind as those of Jerbinsk in the 

 valley of the Lena, Up the picturesque cross valley of Bjellaja, these calcareous 

 rocks extend, and undulate near some dolerites which have broken through them. 

 At the sources of the Bjellaja river these limestones dip westward, and rest upon 

 slate rocks. Partially calcareous under the limestone, these bluish-gray slates be- 

 come purely argillaceous in their deeper masses (" chemically of the nature of mica"), 

 and beyond" the Allachjuna valley, are followed by grauwacke, occupying a breadth 

 of thirteen miles, and an elevation from 1500 to 4000 feet. The slates contain some 

 small traces of coal. Near the slates are mountains of compact siliceous rock, 

 speckled black hornblende and felspar. It is difficult, especially on going eastward 

 from Lake Tungor through the Aldan chain, to determine whether these spots are 

 crystals or fragments. In the pass called Kapiten Mountain, this rock alternates 

 with conglomerate in vertical strata. 



The watershed of the glacial and the great ocean lies in the third or easternmost 

 part of the Aldan system, which consists of petrosiliceous porphyry with hornblende 

 crystals, and judging from the gravel brought down by the affluents to the Ochota, 

 granite and serpentine exist in this part of the chain. 



Respecting the mineral called Marekanite, M. Erman made some investigations at 

 Ochotzk, which led him to recognize that these stones occur not merely in loose 

 pebbles, but in massive rocks. 



On the eastern side of Ochotzk, granite projects in steep cliffs over the sea; then 

 a fclspathic grauwacke rock, in steeply inclined strata, and containing very thin coal- 

 beds, as in the grauwacke Aldan Mountains. Near a great dyke of pyroxenic por- 

 phyry, the strata have been altered by heat to marekanite or pearlstone. In a ravine 

 the degrees of metambrpnism from this cause may be seen, from the carboniferous 

 grauwacke through pitchstone with hyaline quartz, to marekanite and trachyte. 



Regarding the volcanoes and the other interesting geological phenomena of the 



