Geological Society of London. 419 



the Malvern Hills, "with a view to the determination of the chemico- 

 physical processes which have contributed to their formation, Mr. 

 Timins has arrived at the following general conclusions in regard to 

 those rocks of eruptive origin : — (1) that, in the intrusive trap-rocks, 

 the ratio of the oxygen of the silica to that of all the bases taken 

 together, varies progressively from 5:4 to nearly 2:1 ; (2) that the 

 relative proportions of the several bases vary considerably in different 

 rocks, and often characterize particular localities ; (3) that the chemi- 

 cal composition of the eruptive rocks does not vary according to 

 their age ; (4) that the atomic proportions of the silica to the bases 

 is generally highest in the largest masses of trap, and lowest in the 

 smallest masses ; (5) that in the same masses of trap there is an 

 appreciable increase in the silica towards their centres, and that the 

 primary source of all the trap-rocks in the Malvern Hills was nearly 

 a bi-silicate, which, during the various processes by which it has 

 been brought to the surface, has become united, more or less, with 

 other substances, assimilating metallic oxides, lime, magnesia, or 

 alkalies, according as one or another might be locally prevalent, just 

 as, in modern times, the lava of Vesuvius takes up soda, and that of 

 Etna lime ; and (6) that in all the eruptive rocks the atomic propor- 

 tion of the silica to the bases varies according to a common law. 



8. " On the Eelative Distribution of Fossils throughout the North 

 Devon series." By Townshend M. Hall, Esq., F.G.S. 



The author gave a table showing the relative distribution of the 

 organic remains throughout the members of the Devonian system of 

 North Devon. The subdivisions of the rocks employed by Mr. Hall 

 are: — (1) The ''Pilton Beds," highly fossiliferous ; (2) " Cucullasa 

 Zone," a term proposed in place of that of the " Marwood Beds," 

 and suggested by the abundance of the shells of several species of 

 CucuUcBa, which are contained in the sandstone of the series ; (3) 

 the " Morthoe group," unfossiliferovis ; (4) the " Ilfracombe group," 

 containing corals and several species of Brachiopods in good pre- 

 servation ; (5) the "Martinhoe group," unfossiliferous ; (6) the 

 " Lynton Beds," with few fossils; and (7) the "Foreland grits," 

 which are without fossils, and the lowest of the series. 



9. " On the Geology of the Princess Islands in the Sea of Mar- 

 mora." By W. E. Swan, Esq. Communicated by Sir E. I. Mur- 

 chison, Bart., K.C.B., F.E.S., F.G.S., etc. 



Mr. Swan pointed out the existence of a considerable mass of 

 Devonian strata, partly fossiliferous, in sevei-al of these Islands, of 

 an age different from that of the beds of the Bosphorus, which latter 

 he has shown in a former pajDer to belong to the lowest of the 

 Devonian series of tlie Ehine. The presence of remains of fish in 

 the above strata, and of an ancient coral-reef in one of these islands 

 (Andirovitho), was also noticed. 



The rocks which form the remaining portions of these Islands are 

 (1) Trachytic, of younger age than the Devonian strata, and (2) 

 Trappean, more recent than the Trachytic. The Quartz rocks, of 

 which some of the islands are largely, and others entirely composed, 

 are altered sandstones of Devonian age. 



