50 
THE GEOLOGIST. 
formly employed flint knives in sacrificing animals, and for circum- 
cision. From this absence of all reference to flint or stone weapons 
in the earliest writings of the "VYelsh, it seems to follow, either that 
the writings cannot be depended upon to supply precise information, 
or that the men who made the flint weapons were of another race, 
possibly much earlier inhabitants of the island. 
Thirdly, whence was the material obtained ? There are no flints 
in the formations and strata of the vicinity, — that is certain. But 
then they may be picked up any day by a careful search on the 
shore ; and so may granite boulders and worn fragments of igneous 
rocks. 
The chert of these implements is peculiar. It is of a dull, opaque 
green colour, full of minute grey spots. I do not at present know 
of any like it in these parts ; but one lump, tide-borne to the coast, 
would have supplied all required for the sixteen fragments of this 
kind found. 
COEEESPONDENCE. 
Age oftlie JSlackJown Greensand. 
Sir, — The question as to the true position in the Greensand series of the 
"Whetstone" deposits of Blackdown, in Devonshire, is one which, so long 
as it remains uncertain, must naturally force itself upon every geologist ii 
who either studies or collects the fossils of the Greensand formation ; and, !' 
therefore, although this question is neither new^nor of universal importance, 
I trust that I may be permitted to refer to it in the present instance. 
The question is simply this— Are these (Blackdown) deposits equi^^alent 
to the Upper Greensand, to the Gault, or to a portion of the Lower Green- 
sand ? or do they represent the whole of these in an exceptional form ? 
In parts of Kent or Surrey, where the Lower Greensand strata rest 
upon Weald clay, and are everywhere separated from those of the Upf)er 
Greensand by an intervening bed of Gault, such a question would be 
readily determined. But at Blackdown the case is different, the Greensand 
being there found to rest upon red marl, and the Gault either absent or 
imperfectly developed ; so that, in default of the usual direct evidence, the 
geologist must be content with such indirect conclusions as can be drawn jj 
either from the general appearance of the deposits or from a comparison 
of the organic remains with those contained in other portions of the Creta- 
ceous series. Whether or not this last method has been carried out by 
those who consider the Blackdown deposits to be of Upper Greensand age, 
I have not hitherto been able to ascertain. 
In the British Museum all the Blackdown fossils are marked as Upper 
Greensand, in the Museum of Practical Geology, more cautiously, as 
Greensand ; while in both they are ranged side by side with fossils from 
Warminster, — a locality where the Upper Greensand is well defined by the 
presence of the Gault. Now, supposing Uj^per Greensand deposits to pre- 
vail equally at Blackdown and Warmmster, one might expect to find a 
considerable resemblance between the fossils from these two localities ; 
yet, on comparing the specimens, the fact proves itself to be quite the 
reverse ; for, at a rough computation, I find that out of 156* Blackdown 
* These and the following numbers refer to MoUusca only. 
