On the Ancient River-deposit of the Amazon. 567 



that may possibly have brought about the succession in one geological 

 epoch of rocks so distinct in mineral constitution and in fossil con- 

 tents as the Marl Slates, Magnesian Limestone, and Permian Marls. 



6. " The Formation of Rock-basins." By J. D. Kendall, Esq., 

 C.E., F.G.S. 



The author discusses the mechanical difficulties involved in the 

 glacier-excavation theory of lake-basins, and suggests that they are 

 due to the action of falling water engulfed in the crevasses of the 

 ancient glaciers, being thus of the nature of "giants' kettles," though 

 on an enlarged scale. 



7. " On the Diorites of the Warwickshire Coal-field." By S. 

 Allport, Esq., F.G.S. 



The diorites are intrusive in the lower and unproductive measures 

 of the above field and the underlying Millstone Grit below Ather- 

 stone and Marston J abet (two miles south of Nuneaton). The 

 author describes their microscopic characters. One variety is very 

 finely crystalline, and contains brown hornblende ; another con- 

 tains plagioclase felspar with a little orthoclase, small crystals of 

 brown hornblende, many crystals of clear yellowish augite, and 

 several pseudomorphs after olivine, with apatite, magnetite, &c. A 

 mineral also occurs belonging to the hexagonal system, which the 

 author suspects to be magnetite. Other varieties are described, one 

 of which contains augite with hornblende. These rocks differ con- 

 siderably from the syenites of Leicestershire. 



8. " On Lepidodiscus Lebouri, a new Species of Agelacrinitidae, 

 from the Carboniferous Series of Northumberland." By "W. Percy 

 Sladen, Esq., F.G.S., F.L.S. 



9. " On the Ancient River-deposit of the Amazon." By C. 

 Barrington Brown, Esq., A.R.S.M., F.G.S. 



The author described a series of alluvial deposits, varying in 

 thickness from 10 to 1 60 feet, which have been cut through by the 

 river, and form a series of cliffs, giving rise to striking and cha- 

 racteristic scenery. The succession of beds exposed in these cliffs was 

 illustrated by a number of sections ; and it was shown that the strata 

 in question must have been deposited by river-action. It was then 

 pointed out that the river is performing two classes of work — namely, 

 cutting away the older sheets of alluvial matter, and depositing the 

 materials derived from them at a much lower level. The interesting 

 phenomena of the cutting of curves by the river, and the abandon- 

 ment by the river of parts of these curves, giving rise to the forma- 

 tion of lakes, was fully explained ; and in conclusion the author 

 showed by a map what vast areas in South America have thus been 

 covered by these alluvial deposits. 



10. " The Glacial Deposits of Cromer." Bv Clement Reid, Esq., 

 F.G.S. 



The author described the beds shown in the cliffs between Wey- 

 bourn and Happisburgh. The classification adopted was ; — 



