564 Intelligence and Miscllaneous Articles, 



metallic lustre. For the specimen which I present to the Academy 

 I am indebted to the kindness of Professor John Percy, of the 

 School of Mines, London, well known by his important works on 

 Metallurgy. Mr. Weston, Chemist to the Admiralty, has been 

 so good as to furnish me with information on the fact, which he 

 was the first to observe. The ship ' Osborne ' was built at Pem- 

 broke Dockyard, and sent to Portsmouth to be finished. It was 

 there deemed necessary to increase her thickness ; and it was in 

 preparing for that purpose a piece of wood situated near the keel, 

 that they discovered a cavity lined with pyrites. Before being 

 used, this wood had lain, according to custom, for some time in a 

 pit at Pembroke, or perhaps at Portsmouth ; at both places these 

 basins lie between high- and low-water mark and receive a mixture 

 of fresh and sea-water. It must be added that two sewers run 

 into the basin at Portsmouth ; and probably the case is similar at 

 Pembroke ; so that it is not impossible that, besides reducing and 

 sulphuretted substances, the sewers introduce into certain parts of 

 the basins, at least accidentally, a higher temperature than the 

 normal temperature of the sea. 



The surface on which the pyrites is deposited is much blackened, 

 so as to resemble an ulmic substance ; and this bears witness to the 

 reducing effect operated on the vegetable matter. 



There is one mode of present formation of pyrites which is well 

 deserving of attention, but is usually passed over in silence in geo- 

 logical works ; it is that described by M. Bunsen in his important 

 memoir on Iceland*. As shown by that eminent physicist, iron- 

 pyrites is produced in several localities of that country by the 

 vapours of fumaroles charged with sulphuretted hydrogen ; these 

 gaseous substances react upon the iron contained in the silicated 

 rocks through which they infiltrate and which they attack, particu- 

 larly palagonite and pyroxenic rocks. In this case the pyrites has 

 crystallized very neatly in innumerable minute cubes. It is asso- 

 ciated with sulphate and carbonate of lime, of which the base has 

 been taken from the silicated rock and sometimes combined with 

 sulphur in excess. 



Although formed in the wet way, the pyrites of the Boman floor 

 somewhat resembles that engendered by the Iceland fumaroles as 

 regards its mode of dissemination in the rock in which it was pro- 

 duced. 



By the side of these instances of the present formation of pyrites 

 in nature, we must not forget that it was, long since, produced 

 artificially by M. Becquerel, and afterwards by De Senarmont, with 

 the mineral characters of the metalliferous veins. — Comptes Rendus 

 de VAcad. des Sciences, vol. lxxxi. pp. 854-859. 



* Pogg. Ann. vol. lxxxiii. pp. 19/-2/2, 1851. 



