350 
THE GEOLOGIST. 
Leaving this iuteresiiiig inquiry to be fully treated of by some of oiir cor- 
respondents who may have ahxady turned their attention to the subjeet, we 
may suggest that the slow process of rubbing stones, first rndely fashioned by 
fraetTirc, into dclinile shapes with smooth surfaces by the friction of one piece 
on another, was probably the actual process of manufacture, however long a 
time it may have required. The hole may have been produced by the slow 
grinding of pieces of Hint into the stone, possibly by means of some rude 
revolving apparatus. At all events the maniifactiu-e of these hammer-heads 
must have been extensively carried on throughout the country, especially in 
the midland and northern countries, whence specimens of almost elaborate 
workmanship have been not unfrequently obtained. 
Mr. Thomas Wright, the eminent antiquary, we know entertains the opinion 
that the better formed of the antique stone implements were contemporaneous 
with those of metal, and were made with metal tools. 
Geology of Cornwall. — In our reply, page 199, to the inquiiy respecting 
the geology of Cornwall, references to Sir Henry De la Beche's excellent 
" Report on the Geology of Cornwall, Devon, &c.," and to the E,ev. Professor 
Sedgwick's "Memoir on the Slate llocks of Cornwall and Devon," in the 
Journal of the Geological Society, vol. viii., p. 1, were accidentally omitted. 
Geology of Heading. — Dear Sir, — I read in the April number of the 
"Geologist," page 151, in Mr. Charles Hickman's letter, some reference to 
the geological series of deposits in this neighbourhood. We are referred to 
the Quarterly Journal of the Geological Society for further information, but I 
fear it is not in my power to get that ; so may I, as a constant subscriber ever 
since the first issue of your valuable magazine, beg of you to give us a little 
information occasionally as to the strata and fossil varieties in this neighbour- 
hood. The only one I have found has been a large oyster in the chaDc beds of 
Caversham. 
I hope you will excuse my taking this liberty.— Yours much obliged, A. H. 
Reading. 
If we are not favoured by some correspondent with a detailed account of the 
chalk, Thanet sands, Woolwich beds, London clay, and gravels of the Reading 
district, we will take an early opportunity of fulfilling our correspondent's 
request. But we hope that this interesting county will find its own geologist. 
The neighbouring district of Newbui-y, consisting of very similar fomatious to 
those of Readuig, has been described in a little pamphlet by Mr. T. Rupert 
Jones (Geol. Hist., Newbury, 1S51. Blacket, Newbury; Lovejoy, Reading.) 
Geology of Sligo. — I see with surprise that you have in last " Geologist," 
page 317, mistaken the band of mica-sehist and other hard old transition rocks 
which form the Ox mountains in Sligo and Mayo for Old Red Sandstone. The 
latter is very thin, and but rarely seen in the neighbourhood of Sligo, according 
to Sir Richard Griffiths. 
The limestone of Sligo is peculiar and milike the great mass of that forming 
the centre of Ireland ; it seems to be a great development of the lower beds 
resting upon certain others (sandstones) conformably, concerning which there 
is a difference of opinion, viz., as to whether they are really below the lime- 
stone, or are interstratified with it at a considerable height in the formation. 
I had hoped to have investigated this point when I was last at home, but 
was prevented by the weather. Now, however, we may perhaps hope to hear 
something of the rocks La that country from your correspondent, particularly 
if he should be connected with the railway which is being made, and wUl cross 
both the range of older rocks and that of the Curlew mountains, formed, 
I believe, in some places of Old Red Sandstone. — Very truly yours, 
A. B. Wynne. 
HiBBERTi ON Fossil Fish of Burdiehouse. — Sir, — Can you inform me 
