308 A. d. Jukes-Browne—Granite in a Boring at Bletchley. 
greyish-brown ferruginous and siliceous limestone; the general 
character of this rock is such as to suggest a chemical composition 
similar to that of the above analysis of the ‘‘indurated limestone” in 
the boring, and it has cracks filled with calcite. — 
Mr. Timmins says that from the foreman borer’s account it would 
appear that this bed gradually got harder and harder till they came 
on to the “ granitic rock” at 378’ 5”, and that the depth of colour 
also increased to a rusty brown. 
No. 22. The following are Mr. Timmins’ notes on this rock :— 
‘“‘The boring of this bed proved a very tedious operation, averaging 
about five inches a day, and owing to this incessant grinding of 
débris, large particles of rock were not to be expected: what samples 
there are were found after sifting the whole débris through a sieve 
of 1225 meshes to the square inch. The analysis of a bulked sample 
between 378’ 5” and 390 feet is as follows: 
INMSONMIGIE WHEE sonondnasosococaacneoanbencennseeboe 80°106 
Oxide of iron and alumina...................00.0000+ 11°514 
Calexum\carbonatem eee 3838 
Magnesium carbonate .....-......2---+e.0sse+rcsr2= 640 
Alkalies, ete., not determined ..............sseeces 3°902 
100:000 
Before analyzing this sample, all particles of steel and iron from 
the boring tools and casing tubes were extracted as well as possible 
with a magnet; but it is possible that some of the 114 per cent. of 
iron is derived from the mechanical appliances in use.” 
Samples of this material are preserved in bottles, the larger 
fragments are undoubtedly pieces of a granitic rock; the finer 
material which has passed through the sieve is of a brownish colour, 
and has the appearance of a pounded, fine-grained ferruginous 
sandstone. More will be said of this in the sequel. 
Bed 24 was similar to bed 22, but was not so hard and compact, 
so that more rapid progress was made through it. 
Beds 23 and 25 were clays with a blue colour when first brought 
into daylight, but after a few days in the air the colour began to 
fade, and through gradual gradations it arrived at a light brownish 
tint ; this is probably due to the oxidation of the iron. An analysis 
of one of these clays gave the following results : 
Insoluble siliceous matter ..........cce.eseeeee-eeees 79°807 
Oxides of iron and alumina ................0eeeeee. 13°778 
Calcrmmiicarbomate om -tee-eereeeeeeceeceer ence 2-997 
Midomesiumy carl onate wancecn-ecsecseecutesseeseeon 1-718 
98-300 
Mr. Timmins remarks that it had somewhat the aspect and com- 
position of a fire-clay. As the sample sent to me had rather a 
powdery felspathic look about it, I forwarded it to Prof. Bonney, 
who reported that it appeared to be an ordinary clay, “such as 
might well occur in the Jurassic series”; and that it was not a 
decomposed igneous rock or felspar rolled in situ, and had certainly 
not been baked by contact with igneous rock, as it must have been 
if the beds of “ granitic rock” were intrusive sheets. 
