Mr. T. Belt on the Steppes of Siberia. 479 



edge and base of the frond. The authors did not express any positive: 

 opinion as to the function of these processes ; but they suggested that 

 those given off from the non-poriferous face and from the base of 

 calycine fronds, may serve as adventitious roots, and those given off 

 from the margins and from the poriferous face near the margins 

 may be irregularities of growth, unless they are the commencement 

 of new fronds. 



3. " The Steppes of Siberia." By Thomas Belt, Esq., F.G.S. 

 The author described the portion of the Siberian steppes traversed 



by him as consisting of sand and loam. The best section seen by 

 him was at Pavlodar, where he found 1 foot of surface soil, 20 feet 

 of stratified reddish-brown sand, with lines of small gravel, 8 feet of 

 light-coloured sandy silt, 15 feet of coarse sand, with lines of small 

 pebbles and 1 line of large ones, and 6 feet of clayey unlaminated 

 silt, with fragments of the bed rock in its lower half, the bed rock 

 being Magnesian Limestone much crushed at the top. South of 

 Pavlodar the surface was covered with pebbles, which became larger 

 in advancing southward, until the soil was full of large angular 

 quartz boulders. Further south the bed-rock comes to the surface 

 in ridges and low hills, increasing in height until some of them 

 attain 2000 feet. All the rock-surfaces were much shattered, as if 

 by the action of frost, but they showed no signs of glacier-action. 

 The ridges and hills were separated by plains composed of sandy 

 clay, with numerous angular fragments derived from the rocks in the 

 immediate neighbourhood. This is accounted for by the author on 

 the supposition that they formed a series of shallow lakes, frozen 

 over in winter, and that the ice on breaking up carried away frag- 

 ments of the rocks. The distribution of the boulders on the plain 

 north of the ridges was also attributed to floating ice. 



The generally accepted marine origin of the great plain was said 

 to be negatived by the absence of sea-shells in its deposits, whilst 

 Cyrena fluminalis occurs in them. The author regards them as 

 deposits from a great expanse of fresh water kept back by a barrier 

 of polar ice descending far towards the south. In its greatest ex- 

 tension this ice-barrier would produce the crushing of the bed-rock ; 

 and as it retreated, the water coming down from the higher ground 

 in the south would cover a continually increasing surface. 



4. " On the Microscopic Structure and Composition of British 

 Carboniferous Dolerites." By S. Allport, Esq., E.G.S. 



The object of this paper is to supply further and conclusive 

 evidence to show that there are dolerites and basalts of Carboni- 

 ferous age whose original mineral constitution is precisely the same 

 as those of the later Tertiary periods, those of both ages present- 

 ing the same varieties of structure, and that the great alterations 

 which most of the older rocks have undergone constitute the only 

 difference between the two groups. The author describes at some 

 length the various constituents under the following heads, viz. 

 felspar, augite, olivine, magnetite, mica, apatite, glassy matrix, &c. 



