Correspondence. 429 
shaft at the foot of the escarpment is worked by a level about 125 
feet deep; it appears to thicken, and the sand increases in purity 
- and freedom from crystalline spar to the east, where, under the 
limestone range, it is much farther from the surface. Iam informed 
that the late Mr. Hewson, Analytical Chemist, of Liverpool, could 
detect no trace of metallic oxide or other foreign matter, and ascer- 
tained the sand to be absolutely pure silica with a little water. I 
enclose some of the sand for your inspection: it is, without excep- 
tion, the whitest mineral I have_ever seen, and should think such a 
perfectly pure form of native silica would be of great value in the 
manufacture of the better kinds of glass and pottery. 
I remain yours very truly, Grorce Maw. 
BrenTHALL, BrosEerey: June 19, 1865. 
P.S.—As I recently described, in the pages of the Magazine, some 
deposits of sand in cavities in the Mountain-limestone of the same 
district, I would state that they are of a totally different age and 
character to the sand in the Talargoch Mine lode. I have recently 
observed, over a large district of Flintshire and Denbighshire, a 
great extension of the white sand and clay deposits, older than the 
boulder-clay-drift, similar to those at Llandudno. 
To the Editor of the GEOLOGICAL MAGAZINE. 
Sir,—The President of the Geological Society, in his able addresg 
which appears in the ‘Journal’ of the Society for May 1865, in 
noticing my Memoir on ‘the Geology of the Country around Old- 
ham, including Manchester and its Suburbs,’ makes a strange—I 
might say hap-hazard—supposition, which it is only due to him, 
the Geological Survey, and myself, should not be allowed to pass 
without notice. ‘ 
In recounting the succession of the formations. in the neighbour- 
hood of Manchester, as described in this Memoir, the President says, 
‘ Above them’ (the Coal-measures) ‘come the Permian Rocks, con- 
sisting of Lower Permian Sandstone and Upper Permian Marls; 
and these again are overlain by the Pebble-beds, or Conglomerate 
of the New Red Sandstone or ‘Trias. fe 
‘No fossils are mentioned as occurring in this Conglomerate; but 
as it is described as conformable to the underlying Permian, with 
an inclination of about 10° to the south-west, they (sic) may 
possibly turn out to belong to the Permian series, like the Sand- 
stones described by Sir R. I. Murchison at St. Abb’s Head in Cum- 
berland, and then the Trias would be here wanting altogether!’ 
Now, in the first place, St. Abb’s Head is not in Cumberland, nor 
even in England; and doubtless the President means St. Bee’s Head. 
But, under this supposition, I may state, in the first place, that there 
is no similarity whatever between the St. Bee’s Head Sandstone 
and the Pebble-beds or Conglomerate in the neighbourhood of 
Manchester above referred to; and even supposing that it had been 
conclusively established that the former is of Permian age, it would 
