476 Corresjyondence — Mr. S. G. Perceval 



central water pellucid? And that this central pellucid water only 

 was subjected to the "sudden drainage" ? If so, in former times, the 

 laws of rivers and lakes differed much from those of the present day. 

 The cause supposed is an actual impossibility. 

 Brookwood Park, Aleesford, Georgb Geeenwoob, Colonel. 



%th September, 1871. 



LOCAL MUSEUMS AND SCIENTIFIC SOCIETIES. 

 Sir, — Why does not the British Association exert its influence in 

 stimulating local Scientific Societies to form in their Museums 

 collections representing the Geology, Mineralogy, and Natural 

 History of their own respective neighbourhoods ? Such a system, 

 combined with a central Museum in London, would tend more than 

 anything to the advancement of science. At present, provincial 

 Museums are little better than curiosity shops, with no recognized 

 plan of arrangement whatever. Numerous valuable private collec- 

 tions exist throughout the country, representing the geology, etc., 

 of various localities, which are too often dispersed and lost. Perhaps 

 private Collectors would show more public spirit, if greater zeal and 

 better judgment were shown by local Societies. — F.G.S. (Brighton). 



A SILICIFIED CORAL FROM THE COAST OF SUSSEX, ETC. 

 Sir, — Eolled fragments of a Silicified Coral, resembling the 

 Tisbury Isastrcea, are occasionally found on the coast of Sussex and 

 the Isle of Wight. Major Barnes, of Southampton, who has for 

 many years collected the south-coast agates, has found four speci- 

 mens, one on the beach at Eyde, two at Sandown, and one at 

 Hastings. I also obtained a fine specimen on the beach at Hove, 

 near Brighton. The only locality from which they could have been 

 drifted, if belonging to the Oolite, is Portland. Does the Tisbury 

 Coral occur there ? or, can they be derived from the Upper Green- 

 sand, like the silicified wood found at Hove ? 



Spender Geo. Perceval. 



Occurrence of Diamond in Xanthophyllite.— Writing from 

 St. Petersburgh to the Editor of the Jahrhuch fur Mineralogie, 1871, 

 part 3, Jeremejew announces the discovery of microscopic crystals 

 of diamond in the xanthophyllite of the Schischimskiaw mountains in 

 the Urals. Magnified 30 diameters they are distinctly visible, and 

 with a power of 200, their crystalline form can be determined with 

 great precision. It is a hexakistetrahedron combined with a 

 slightly developed tetrahedron, the faces of the first form being 

 rounded, those of the latter completely flat. The gi-eater part of 

 the crystals are colourless and completely transparent, and some few 

 are slightly brown. They lie in parallel position in the matrix, 

 their trigonal intermediate axes being vertical to the foliation of the 

 xanthophyllite. The green plates of the latter near the rounded 

 aggregations of the talcose slate and serpentine, contain an unusually 

 large number of crystals, and they are also found in these rocks 

 themselves. 



