402 
THE OEOLOGIST. 
fprns, ml li puts. Tliis lasi would prrliaps prove most useful, because it can be 
purchased for a small sum ; whereas the large works alluded to above are ex 
jieusivc. They are in tiic libraries of the liritish Museum, the Geological 
Society, Souiersct House, aud (he (ieulogieal Survey, Jcruiyu-street. We can- 
not do better than call attention to the fine eolleetion of fossil ferns in lloom I, 
of the North Geologie;il Gallery in the i^ritish Museum. A great addition has 
just been made by the purchase of the v;dual)le, and in many instances unique, 
specimens of oolitic plants from Scarborough, which formed the eolleetion of 
Mr. Bean, a gentleman who has devoted very many years of liis life to their 
aeeuuiulation. By apjilying to the keeper of the ' geological department, the 
student may obtain jiermission, as in all the other departments of^ our national 
nniseum, to visit the collection on private days ; and every facility is afforded 
for tJie examination and comparison of specimens. The characters, so important 
in the elassidcation of recent ferns being frequently absent or wanting in the 
fossil remains, the pahcobotanist is compelled in many instances to accept the 
most worthless and least reliable characters, in order to form some sort of clas- 
silieation to guide others who may foUow hiui in his labours. 
We have seen some coal-ferns from llmenan (Germany) with fructification ; 
but this condition is rare. 
We must not forget to mention 11. B. Geinitz's magnificent work on the 
Saxony coal, "Die Versteinerungen der Stein-Kohlenformation in Saehsen." 
folio, Leipsie, 1855, with numerous plates, as a first-rate source for information 
on some fossil ferns ; especially as lie 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" Svo., 2 vols., Bohn, London, 1858, several 
references to descriptions of fossO ferns will be foutul in the chapter on coal. 
Mr. Gregory, of No. 4, King William-street, Strand, has recently obtained 
some very good specimens of Ci/i-Jopferii; llUicnuca from Ireland, in full fructi- 
fication ; and we believe that he has also some foreign specunens of other ferns 
in the same state. 
Cemented Kock-debris, ne^ve. Blanchabd, Northumberland. — Sir, — 
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., iii wliicli 
the author states it as his opinion that the cavern originally eommmiicatcd with 
the surface by an opening sufficiently wide to allow the passage of all its con- 
tents ;" and that this opening liad afterwards been filled up by " large angular 
fragments of Limestone cemented by carbonate of lime, easily enough mistaken, 
without a carcfid inspection, for orduiary limestone 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 smaller pieces called " polings," reaching from one 
stemple to the other. Upon these the workmen deposit their rubbish. 
In a mine at ShUdon, near Blanehland, in the county of Northumberland, 
there is a spring of water highly charged with carbonate of lime, wluch 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 declai'C 
actually harder than the origuial bed. 
This I think would su])port Mr. Pengelly's theory. — Youi-s respectfully 
T. Hutchinson, Waskcrley Park, near Darlington. 
