some Cambridgeshire Sands and Gravels. 139 
Second or Chesterton Terrace. 
Pit near Pike and Eel, Chesterton, 24 ft. above O.D. 
This pit is opened up in fine flint gravel with seams of rather 
coarse sand and in it have been found a good many far-travelled 
rocks, including rhomb-porphyry. To the naked eye the sand 
when dry is white and chalky in appearance. It shows many 
grains of Chalk and flint together with glauconite, fragments of 
the thin shells of fresh-water mollusca, prisms of Inoceramus and 
Kchinoid spines. With dilute hydrochloric acid it effervesces 
strongly, and in the cleaned sample dark grains are fairly 
abundant. j 
The sand yields an abundant heavy residue in which nearly 
all the grains are covered with brown limonite. After treatment 
with strong acid many of these are found to be glauconite or a 
pale brown isotropic material of uncertain character, perhaps 
consisting of colloid silica. The principal minerals identified are 
garnet, hornblende, rutile, zircon, kyanite, staurolite and tour- 
maline. The garnets are mostly subangular and rounded, only 
a few being angular. The grains of tourmaline, which are chiefly 
brown, are well rounded. The minerals in general do not present 
any special features of interest: they are on the whole more 
rounded than in the older gravels. 
IV. Gravéls of the Great Ouse Basin. 
Gravel Pit half a mile S.E. of Fenstanton, 36 ft. above O.D. 
This pit is situated on the north side of the Cambridge and 
Huntingdon road, close to the county boundary. It shows a 
ferruginous gravel of the usual type, with brown ‘pipes’ and 
seams of sand. 
The sand is brown in colour, with very little muddy matter. 
Tt was treated at once with dilute acid, giving only slight 
effervescence, and yielding a remarkably white sample consisting 
of clean bright colourless quartz and rounded grains of white 
flint with much glauconite. In the heavy residue pink garnet 
and bright grains of magnetite were conspicuous before mounting, 
while a few grains of glauconite sank in the bromoform. 
The heavy grains are of unusually large size and garnet is 
predominant, being often extremely angular in shape; other 
transparent minerals are present only in small quantity. The 
minerals recognized are as follows: garnet, generally very angular, 
tourmaline, kyanite in fine large crystals, staurolite, hornblende, 
epidote and rutile; zircon is rare. 
