40 



THE GhlOLOGIST. 



raeml)ers, five shillings a-year. All members will be entitled to copies of Avhatever 

 printed minutes of the proceedings of the Association are issued. The first meet- 

 ing of the Association for business, will be held on an early day in January, which 

 will be duly announced to subscribers, and when an inaugural address will be 

 delivered by the Chairman. 



Chalk Spo:^ges of Yorkshire. — " Sir, — I think a paper, accompanied by 

 sketches, of the sponges from the chalk of Flamborough Head, would be very accept- 

 able to many of your readers. I do not find them described in any of the popular 

 books, although probably they are to be found figured in some of the works on 

 Yorkshire.— Yours, &c., X. Y." 



Mammalian Remains near Wells. — " Sir, — Seeing in one of your maga- 

 zines of this year a request that Geologists would fiirnish you with the localities 

 where the remains of mammals have been observed m the provinces, I beg to 

 inform your readers that I found several teeth of Rhinoceros and of Elephants on 

 the side of the Mendip Hills, about two miles from the city of Wells, and close to 

 the celebrated Wokey Hole cavern ; they were about fifteen feet below the surface, 

 in a conglomerate resting on the dolomite Hmestone. — Yours, &c., Francis 

 Drake, Leicester." 



Manner of cutting Films of Selenite. — (See Vol, I. p. 444.) — " Good, large 

 crystals of selenite can be split into laminae of uniform thickness with a penknife ; 

 but much care is required, and many failures occur. This is the method I have 

 always employed for my own pui-poses, Avith sufficient success. — H. C. Sorby." 



Mineral- Veins. — (See Vol I. p. 450.) — " If a portion of limestone be placed in 

 the solution of any salt of the peroxide of iron, or a salt of the jjrotoxide exposed 

 to the air, a deposit of the peroxide of iron is formed on the limestone. No such 

 effect is produced by a fragment of sandstone ; and, in some cases, at all events, 

 this will, I think, explain what your coiTespondent refers to. — H. C. Sorby." 



Mineral-Veins in Limestones and Sandstones. — "Dear Sir, — In reply to 

 the very candid request of your coiTespondent, I beg to say, that the examples 

 which have led me to amve at the conclusion that mineral-veins, in general, 

 contain more iron in limestone than in siliceous strata, are those afforded in the 

 lead-mining district of the north of England ; more particidarly in that part of it 

 comprising Alston Moor, Allandale, and Weardale. The lead-bearing strata in 

 these localities are of the mountain-limestone series, and consist of alternating 

 members of calcareous, siliceous, and argillaceous characters. Interstratified witli 

 these beds is one of basalt, locally called the great whin-sill, and of considerable 

 thickness, amounting in some places to 30 or 40 fathoms, or even more. Higher 

 up in the series is another of the same nature, which may l3e observed in the Wear 

 Valley between Stanhope and Eastgate, but this seems to be of veiy limited extent. 

 The great whin-siU lies at a considerable depth below the surface in Weardale, 

 nevertheless, it has been sunk through at Pasture Grove mine, where a very 

 productive vein is being worked. It has also been penetrated at Slit mine, near 



lay open a very considerable thickness of strata. Owing to the rise of the beds in 

 a westerly direction, the same sills which have to be sunk into in Weardale are 

 accessible by adits at Alston Moor. The thickness of strata from the upper 

 surface of the great whin-sill to the top of the lead-measm-es is about 180 fathoms. 

 In this space are included 10 beds of limestone, 27 of sandstone, 29 of plate, 3 of 

 an argillo-siliceous nature, and 5 of sulphureous coal : the aggxegate thickness of 

 each set being as follows, namely, limestone 179 ft., sandstone 345ft., plate 414ft., 

 argillo-siliceous beds 147 ft., and coal 5 ft. Although these strata do not maintain 

 a perfect uniformity of thickness throughout, yet, the above may lie taken as 

 approximating to accuracy sufficiently for the present purpose. The limestones and 

 sandstones are the chief metalliferous strata, and, in the above section, the thick- 

 ness of the former to that of the latter is as 1 to 1-91, without including the sili- 

 ceous in the argillo-siliceous beds. The argillaceous strata are seldom productive 

 of lead-ore, except in some veins which carry a rider, or vein-stone, where they are 

 said to be mineralized. Dividing the lead-measures which lie above the whin-sill 

 into three divisions, the middle is the richest and most extensively worked. From 

 long experience in working these mines, it has been noted as a fact, that tlie veins 



