Geological Society, 381 



the top of Shooter's Hill to those of Kent, on the surface of which the rivers 

 once flowed ; secondly, that these rivers have subsequently washed away all 

 that immense mass of materials which would be requisite thus to reconstruct 

 the surface ; and, thirdly, that, having worn down that surface into nearly 

 its present form, the rivers perpetually shifted their channels, so as to distri- 

 bute the gravel equally over the whole plain of London, yet remained long 

 enough in each channel to lodge there deposits of this gravel 20 ft. or 30 ft. 

 thick. 



A paper was also read, entitled " A few Facts and Observations as to the 

 Power which running Water exerts in removing heavy Bodies,'* by Matthew 

 Culley, Esq. F.G.S. &c., in a letter to Roderick Impey Murchison, Esq. 

 Sec.G.S.F.R.S.&c. 



The heavy rains which fell during three days of August, 1827, swelled to 

 an unusual height the small rivulet called the College, which flows at a 

 moderate declivity from the eastern watershed of the Cheviot Hills, and 

 caused that stream not only to transport enormous accumulations of several 

 thousand tons' weight of gravel and sand to the plain of the Till, but also to 

 carry away a bridge then in progress of building, some of the arch-stones of 

 which, weighing from one half to three fourths of a ton each, were pro- 

 pelled two miles down the rivulet. 



On the same occasion, the current tore away, from the abutment of a 

 mill-dam, a large block of greenstone porphyry, weighing nearly two tons, 

 and transported the same to the distance of a quarter of a mile. Instances 

 are related, as occurring repeatedly, in which from one to three thousand 

 tons of gravel are in like manner removed to great distances in one day ; 

 and the author asserts, that, whenever 400 or 500 cart-loads of this gravel 

 are taken away for the repair of roads, one moderate flood replaces the 

 amount of loss with the same quantity of rounded debris. 



Parallel cases of the power of water are stated to occur in the Tweed, 

 near Coldstream. 



June 19. A paper " On the occurrence of Agates in the Dolomitic Strata 

 of the New Red Sandstone Formation in the Mendip Hills," by the Rev.W. 

 Buckland, D.D. V.P.G.S. F.R.S. &c. &c., was read. These agates are 

 ploughed out of the surface of the fields at Sandford, near Banwell, and are 

 nearly allied to the potato stones, which abound in the new red sandstone 

 formation that surrounds the Mendip Hills. Their prevailing colours are 

 various shades of grey ; their internal structure resembles that of the bird's- 

 eye agate, presenting alternate bands of chalcedony, jasper, and hornstone, 

 disposed in irregular and concentric curves ; some specimens from Worle 

 and Clevedon are of the nature of fine jasper agates, and of a bright red 

 colour. 



A shallow pit, from which the agates are extracted at Sandford, presents 

 the following section : — 



1 . Yellow clay, mixed with magnesia and carbonate of lime - - 6 in. 



2. Yellow dolomite, used as firestone in linekilns ; it crumbles readily 

 to a soft powder, and is filled with specks of manganese, and con- 

 tains veins of small nodules of chalcedony - - 6 



3. Yellow clay, falling to powder, in water, like fuller's earth, and 

 containing much carbonate of lime and magnesia. In this clay the 

 agates are dispersed irregularly, like nodules of flint in chalk - 6 



4. Yellow clay and earthy dolomite, to the bottom of the pit - 1 2 



The author adduces a parallel example of beds and nodules of jasper and 

 jasper-agate in the mountains of dolomite, near Palermo, in a formation of 

 the same age with the new red sandstone of the Mendip Hills. He also gives 

 examples of agates formed in cavities of chert of the green-sand formation, 

 near Lyme Regis, and in cavities of silicified wood and silicified corals and 

 shells. The most beautiful specimens of the two former are from the ter- 



c c 3 



