A. J. Jukes-Browne—Granite in a Boring at Bletchley. 359 
To complete the record of the boring, it may here be mentioned 
that water was found at the depth of 390 feet 9 inches in the first 
bed of “granitic rock,” and again in the lowest clay at 410 feet, or 
more probably from a bed immediately underlying this clay, but 
not pierced. In both cases the water was very salt and unfit for 
use, so that the boring was abandoned and a coffee-house is now 
built over the site. 
We may now revert to the so-called “granitic rock.” It has 
already been stated that fragments of such a rock do certainly occur 
among the samples, and there seems no reason to doubt that these 
fragments were brought up from the depths named. As evidence 
on this point I quote a letter from Mr. A. Timmins to Mr. Cameron, 
dated November 19, 1886 :—“‘I enclose a sample of the strata from 
present depth (390ft.) ... I make it out as hornblendic granite, _ 
and have had suspicions for some time. A few weeks ago my 
father brought home a piece of stone similar to the sample, and said 
that he was told by the foreman that it had come up the boring. 
Ever since I have sieved the samples sent to me, and Saturday was 
the first time, since that above mentioned, that I was able to get any 
larger pieces. My suspicions were at once confirmed, and I] make 
out that we have bored through 10 feet of this granitic rock.” | 
With this evidence we may I think take it for granted that pieces 
of a granitic rock did come up from the depths stated in the account 
of the boring. 
Next as to the nature of the rock: two small fragments were sent 
to Prof. Bonney, who was kind enough to examine them and reported 
as follows: “The fragments which you have sent me are of a 
rock closely allied to granite. As far as I can see with a strong 
lens they are likely to belong to the microgranulite of Fouqué and 
Lévy—that is, a rock with felspar quartz and mica or hornblende 
(probably the latter in this case) in a sort of fine mosaic; the in- 
dividual grains not being very definite in form unless showing a 
micrographic structure. It is not a true granite, and yet itis rather 
too crystalline for a normal quartz-felsite ... I never saw one 
like it among the Midland Paleozoics, but it has a general resem- 
blance to the rocks of the Narborough district.” There is no proof 
however that the whole of the thickness given to ‘“ granitic rock” 
in Mr. Timmins’ account of the boring consisted of the rock above 
described ; there is indeed strong evidence for the belief that it did 
not. In the first place I am informed by Mr. Cameron that he went 
over to Bletchley at the time they were boring through this rock, 
and selected small samples out of the foreman’s box from depths 
of 391 feet and 393 to 396 feet. These he has kindly sent to 
me, pointing out that they are simply sandstones, without any trace 
of granitic fragments or minerals. The first is a light-coloured and 
fine-grained sandstone composed of small quartz grains with ferru- 
ginous staining; the second is a dark brown ferruginous sandstone. 
Both are such rocks as occur in the Kellaways Beds at the base of 
the Oxford Clay, and the only way of reconciling their existence 
with the recorded occurrence of granitic rock at about the same depth 
