2 1 6 Geological Society. 



viously existed below that sea, must beat the strata underneath 

 its bottom, because they are now protected by a bad conductor. 

 The consequence must be, that they will raise, by their expan- 

 sion, the newly formed beds above their former level j — and thus 

 the bottom of an ocean may become a continent. The whole ex- 

 pansion, however, resulting from the altered circumstances, may 

 not take place until long after the filling up of the sea; in which 

 case its conversion into dry land will result partly from the filling 

 up by detritus, and partly from the rise of the bottom. As the 

 heat now penetrates the newly formed strata, a different action 

 may take place ; the beds of clay or sand may become consoli- 

 dated, and may contract instead of expanding. In this case, 

 either large depressions will occur within the limits of the new 

 continent, or, after another interval, the new land may again sub- 

 side, and form a shallow sea. This sea may be again filled up 

 by a repetition of the same processes as before : — and thus alter- 

 nations of marine and freshwater deposits may occur, having inter- 

 posed between them the productions of dry land. 



Mr. Babbage's theory, therefore, may be thus briefly stated. — 

 In consequence of the changes actually going on at the earth's 

 surface, the surfaces of equal temperature within its crust, must 

 be continually changing their form, and exposing thick beds, 

 near the exterior, to alterations of temperature; the expansion 

 and contraction cf these strata will probably form rents, raise 

 mountain-chains, and elevate even continents. — The author admits 

 that this is an hypothesis ; but he throws it out, that it may be sub- 

 mitted to an examination which may refute it if fallacious, — or, if 

 it be correct, establish its truth, — because he thinks that it is de- 

 duced directly from received principles, and that it promises an 

 explanation of the vast cycles presented by the phenomena of 

 geology. 



March 26. — A letter was first read from Charles Denham Or- 

 lando Jephson, Esq., M.P., F.G.S., to George Bellas Greenough, 

 Esq., P.G.S., " On Variations of Temperature in a Thermal Spring 

 at Mallow." 



The observations recorded in this letter were made principally 

 during the autumn and winter months of 1833. The extreme 

 variations were 67° and 71 tV» the difference depending in Mr. 

 Jephson's opinion on the quantity of water acted upon. From 

 80 to 100 yards north of the spring at which the observations 

 were made, are other thermal springs, the temperature of which 

 is 1° higher, and from 60 to 80 yards to the south is a cold spring, 

 having a temperature of 54-°. The formation from which the waters 

 issue is limestone. 



A letter was then read from William Henry Egerton, Esq., 

 F.G.S., addressed to Charles Lyell, Esq., For. Sec. G.S., " On 

 the Delta of Kander." 



The Kander in its ancient course flowed parallel to the Lake of 

 Thun, and emptied itself into the Aar, beyond the village of 

 Heiraberg j but in consequence of the injury done to the land by 



