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THE GEOLOGIST, 



ferns, with cuts. This last would perhaps prove most useful, because it can be 

 purchased for a small sum ; whereas the large works alluded to above are ex 

 pensive. They are in the libraries of the British Museum, the Geological 

 Society, Somerset House, and the Geological Survey, Jermyn-street. We can- 

 not do better than call attention to the fine collection of fossil ferns in Room I, 

 of tlie North Geological Gallery in the British Museum. A great addition has 

 just been made by the purchase of the valuable, and in many instances unique, 

 specimens of oolitic plants from Scarborough, which formed the collection of 

 Mr. Bean, a gentleman who has devoted very many years of his life to their 

 accumulation. By applying to the keeper of the geological department, the 

 student may obtain permission, as in all the other departments of our national 

 museum, to visit the collection on private days ; and every facility is afforded 

 for the examination and comparison of specimens. The characters, so important 

 in the classification of recent ferns being frequently absent or wanting in the 

 fossil remains, the palgeobotanist is compelled in many instances to accept the 

 most worthless and least reliable characters, in order to form some sort of clas- 

 sification to guide others who may follow him in his labours. 



We have seen some coal-ferns from Ilmenan (Germany) with fructification ; 

 but this condition is rare. 



We must not forget to mention H. B. Geinitz's magnificent work on the 

 Saxony coal, " Die Yersteinerungen der Stein-Kohlenformation in Sachsen," 

 folio, Leipsic, 1855, with numerous plates, as a first-rate source for information 

 on some fossil ferns ; especially as he has taken much trouble to reduce to 

 their true specific limits the very numerous forms of fragmentary ferns re- 

 garded by authors as typical of so many species. In the 2nd, volume of 

 Mantell's " Wonders of Geology" 8vo., 2 vols., Bohn, London, 1858, several 

 references to descriptions of fossil ferns will be found m the chapter on coal. 



Mr. Gregory, of No. 4, King William-street, Strand, has recently obtained 

 some very good specimens of Cydopteris Hibermca from Ireland, in full fructi- 

 fication ; and we believe that he has also some foreign specimens of other ferns 

 in the same state. 



Cemented Rock-debris, neae Blanchaed, Noe-thumbeeland. — Sie, — ■ 

 In the November number of the " Geologist" I observe a paper on the os- 

 siferous fissures at Oreston, near Plymouth, by W. Pengelly, P.G.S., in which 

 the author states it as his opinion that the cavern originally communicated with 

 the surface by an opening sufficiently wide to allow the passage of all its con- 

 tents ;" and that this opening had afterwards been fiUed up by " large angular 

 fragments of limestone cemented by carbonate of lime, easily enough mistaken, 

 without a careful inspection, for ordinary bmestone somewhat rich in coarse 

 veins, and which the quarrymen say is as hard as the surrounding rock." 



This reminds me of a circumstance which lately came under my notice of a 

 mass of shale-debris having become cemented in the same manner. 



In working a lead mine it is customary to drive strong pieces of timber, 

 locally called " stemples" betwixt the sides of the vein, at short distances apart. 

 These are covered by other smaUer pieces caUed " polings," reaching from one 

 stemple to the other. Upon these the workmen deposit their rubbish. 



In a mine at Shildon, near Blanchland, in the county of Northumberland, 

 there is a spring of water highly charged with carbonate of lime, which having 

 filtered for a considerable number of years thi'ough the debris consisting of 

 shale deposited as above, has so hardened and cemented it together, that, the 

 timber having decayed, the cemented rock not only retains its position, but it 

 would require blasting to remove any part of it, being as the miners declare 

 actually harder than the origmal bed. 



This I think would support Mr. PengeUy's theory. — Yours respectfully 

 T. Hutchinson, Waskciiey Park, near Darlington. 



