Mr. T. F. Jamieson on the Glacial Period. 151 



section connecting the Silurians of Russia and Scandinavia, and pass- 

 ing through the islands of Gothland and Oesel. The paper is accom- 

 panied •with a map and a tabulated list of the fossils found at the 

 several horizons which have been distinguished by the author. He 

 points out which of these species are found ranging into other areas, 

 and proposes eventually to publish figures and descriptions of the 

 characteristic Russian forms. The first part of the author's palaeon- 

 tological work has just appeared in the shape of a memoir describiug 

 60 species of Trilobites of the genera Phacops, Cheirums, and Encri- 

 nurus. The total number of species of the Trilobites is about 150, 

 of which, only about 15 occur in the Upper Silurian. 



6. " On Chilostomatous Bryozoa from Bairnsdale (Ctippsland). - ' 

 By A. W. Waters, Esq., P.Ct.S. 



7. " The Silurian Species of Glauconome, and a suggested Classi- 

 fication of the Palaeozoic Polvzoa." Bv (x. TV. Shrubsole, Esq., 

 F.G-.S., and G. R. Vine, Esq. * 



8. "On the Cause of the Depression and Re-elevation of the 

 land during the Glacial Period." By T. P. Jamieson, Esq., P.G.S. 



The author commenced by noticing the theory advanced by Adhe- 

 mar and Croll, according to which the submergence was due to the 

 effect of a polar ice-cap causing a displacement of the earth's centre 

 of gravity and thereby drawing the ocean towards the ice-covered 

 pole, and proceeded to show that this theory is opposed to the geolo- 

 gical evidence, according to which the amount of submergence has 

 been unequal in adjacent areas and along the same parallels of 

 latitude, showing that the movement has been in the land and not 

 in the sea. The facts of submergence also prove that no such cap 

 of ice could have existed at the time in the northern regions. 

 Sundry other objections were also pointed out. The author then 

 went on to state his own hypothesis, which is to the effect that the 

 depression of the land was caused by the weight of ice laid upon it, 

 and the re-elevation by the disappearance of the ice. The amount 

 of depression would depend partly on the weight of ice and partly 

 on the elasticity or yielding nature of the ground beneath it. He 

 then proceeded to consider what was the weight of ice that probably 

 existed, and referred to the elastic and flexible nature of the earth's 

 crust, as evinced by earthquakes &c. 



He further considered the relation of time to pressure, and touched 

 upon the probable rate of subsidence, which he supposes to have 

 been very slow and gradual. The recovery of level, he thinks, would 

 also be very gradual, and probably, in most cases, not complete. 



He next proceeded to show how his hypothesis is borne out by an 

 appeal to geological evidence in various countries, taking England, 

 Ireland, North America, and Greenland as examples. He further 

 pointed out its application to the facts connected with the loess beds, 

 Fjord latitudes, and lake-basins, and concluded with some observa- 

 tions on the remarkable connexion between glaciation and submer- 

 gence in all countries. 



