VOL. XIX. (i) DEEP BORING— TETBURY WATERWORKS 
65 
Bed at Chiselcombe Quarry, Loders Cross, near Bridport, 
Dorset.^ It is full of lamellibranchs, which included Chlamys 
articulata auctt. (very abundant), Eopecten velatus (Goldfuss), 
etc. Masses of coral in a crystalline condition occurred not 
infrequently. The nether surface of the Cephalopoda-Bed was 
irregular and rested on a “ hard cap ” (some 3 ins. thick) to 
the Sands. This hard cap had a waterworn surface, and was 
bored by annelids. 
The Sands, when dry, were grey-green in colour, but a 
pretty green — as at Kemble — when freshly brought up to the 
surface, and therefore moist. 
Dr. Boswell has also kindly examined for me a sample of 
the Cotteswold Sands from about 395 feet down. He reports : 
“ The sample has a fair quantity of calcareous cement, appearing 
in the sand under the microscope as abundant small cleavage rhombs of 
calcite — a result of the slight crushing of the sample. 
‘ ‘ I have not been able to work out the mineral composition thoroughly, 
but its general aspects seem to be those of the Sands from Dorset to 
Yorkshire, there being a remarkably similar (and distinctive as regards 
other formations) mineral suite over the whole of the outcrop where the 
beds are fairly sandy. The constancy of the mechanical composition 
from the coast at Bridport up to Bath and Wotton is also noteworthy, 
but a change sets in as Northampton is approached. 
“As is so often the case in borings, the sand is greyish in colour and 
unlike the yellowish sand at the outcrop. The average size of the grains 
is .125mm. diameter. Even on heating with dilute hydrochloric acid, 
the colour does not change appreciably, but of course the calcite rhombs 
dissolve. The grey-green colour does not therefore appear to be due to 
oxides, carbonate or sulphide of iron. The crop of density— greater 
than — 2.8 contains a good deal of coarse glauconite. As in the case of 
most of the glauconite I have met, the density, instead of being 
2.3, as often stated, runs rather high. This glauconite gives the grey- 
green colour to the sand. The grains are of diameter .2mm., and 
appear to belong to a different generation from that of the other heavy 
minerals (diameter .06mm). Of the latter, the most abundant are small 
angular colourless to pale brownish-red garnets (so characteristic of the 
Inferior Oolite everywhere), muscovite flakes (.4 to .5mm. diameter) some- 
what rounded zircon prisms, blue tourmaline, abraded stumpy apatite 
prisms, coffee-brown to yellow-green rutile, and straw-coloured tabular 
anatase. Ilmenite and magnetite also occur, and possibly green horn- 
blende and staurolite.” 
Between 396 feet and 406 or 408 feet down the Sands 
were of light grey colour and less coherent, but below, they 
were very similar to the portion between 391 and 396 feet, 
only they became more “ clayey ” lower down. 
I Proc. Geol. Assoc., vol. xxvi. (1915), P- 63. 
