122 Reviews — Re v. T. G. Bonney’s Cambridgeshire Geology. 
ZRIEJ'VIIEWS.. 
I. — Cambridgeshire Geology. A Sketch for the Use of 
Students. By T. G. Bonney, M.A., F.G.S., etc., Tutor and 
Lecturer in Natural Science, St. Jobn’s College, Cambridge. 
(Deigbton, Bell & Co., 1875.) 
T HIS sketcb of Cambridgeshire Geology is stated in the preface to 
have been published to give to beginners some information on 
the local geology of this district. A pamphlet on tbis subject was 
privately printed by the late Prof. Sedgwick in 1861. Since tbat 
perod many papers have been written on the geology of this part 
of England. Mr. Bonney gives a short accouut of the strata of the 
Mesozoic period, and the nature of their Variation when traced 
diagonally across England from the Southern counties. The physical 
geography of the Cambridge district is thus described : “ The valley 
of the Cam is a wide alluvial plain, bounded on the eastern side by 
a clearly-marked escarpment of the Lower Chalk, on the Western by 
more irregulär hilly district, consisting partly of outliers of Lower 
Chalk, partly of inferior deposits capped by Boulder-clay. The 
right bank of the valley is formed by the edge of the great Chalk 
plateau, which has been corroded by the action of rain and rivers 
into undulating hills and valleys. From this Chalk plateau sundry 
streams descend towards the Cam, forming wide valleys with slielv- 
ing sides, occupied in places by alluvial deposits. The fen land does 
not extend to Cambridge, its nearest inlets are four to five miles 
distant ; thence it extends to the sea, as a widespread tract of per- 
fectly flat land, scarcely above the sea-level.” Next follows a descrip- 
tion of the Jurassic strata, which, in the neighbourhood of Cambridge, 
consists of a vast argillaceous deposit, with a few local and partial 
calcareous beds, the lower part of which is Oxford Clay, and the 
upper part is Kimmeridge Clay ; in some places tliese graduate one 
into the other, without any very clear line of demarcation. The 
lower beds of the Oxford Clay, containing A. Duncani, etc., may be 
seen at St. Neots ; the higher beds at St. Ives, where the deposit 
consists of a pale bluish-grey fine clay, with occasional calcareous 
coucretions, crystals of selenite, and lumps of pyrites often altered 
into limonite. Grypliea dilatata is very abundant, also Am. cordatus, 
Mariae, Eugenii and Hecticus, and Belemnites haslatus. The most 
important of the calcareous zones is that at Eisworth, described by 
Prof. Seeley (Ann. and Mag. Nat. Hist. ser. iii. vol. x. p. 98). The 
Transition Clay has been called by Prof. Seeley Ampthill Clay. Near 
Upware there is a low broad ridge of Limestone, which Mr. Bonney 
regards as a representative of the Coralline Oolite. 
The Kimmeridge Clay is best seen at Eoslyn Pit, near Ely. It 
is of a bluish-black colour, containing Septaria. Among the fossils 
are Lingula ovalis, Ostrea deltoidea, Exogyra virgula, Am. biplex, 
Trigonel/ites latvs, and several genera of fishes and reptiles. 
The Neocomian deposits of Potton and Upware are next described. 
Mr. Bonney adopts the same view with regard to the age of these 
