﻿Revieics — Rev. T. Q. Bonneijs Cambridgeshire Geology. 123 



deposits as that expressed in papers which have appeared in this 

 Magazine. The Gault in this district is described as a pale bluish- 

 grey tenacious clay, in which are concretions of iron pyrites, small 

 crystals of selenite, and light brown phosphatic nodules ; its thick- 

 ness at Cambridge is about 115 feet, near Hitchin 214. Its upper 

 surface is uneven. The base of the Gault contains several fossils, as 

 Inoceramus concentricus, Nticula pectinata, Belemnites minimus, etc. 

 Besting on the eroded surface of the Gault there is a stratum barely 

 a foot in thickness, full of green grains of glauconite and black 

 nodules of phosphate of lime, looking like a sediment from the 

 purer marl above ; it contains erratic boulders covered with 

 Plicatula sigiUina, as was pointed out by Prof. Seeley in the third 

 volume of this Magazine. This bed is remarkable for the number 

 of fossil fishes, Deinosaurs, Ornithosaurs, Chelonians, etc., which it 

 contains ; Mollusca, Crustacea, Coelenterata, Foraminifera, are also 

 abundant. Mr. Bonney supposes the phosphatic nodules to have 

 been formed by concretionary action. He regards some of the 

 fossils as having been derived from the Gault. We cannot agree 

 with him in calling this seam Chloritic-marl ; as the fossils proper to 

 the bed are those of the Chalk-marl, and the characteristic fossils of 

 the Chloritic-marl are almost entirely absent. The Chalk round 

 Cambridge contains Holaster suhglohosus, Inoceramus Cuvieri, etc. 

 (see Seeley, Geol. Mag. Vol. I. p. 153). The Post-Pliocene de- 

 posits of Cambridgeshire are described in the following order : — • 

 1. Boulder-clay. 2. Coarse Hill Gravel. 3. Fine Gravel of the 

 Plains — this is well seen at the Barnwell Gravel Pit ; it contains 

 Cyrena Jluminalis, Hydrohia marginata and Unio littoralis, all 

 now extinct in England ; along with these are found existing 

 species of land and fresh-water shells, and bones of Bos, Equus, 

 Bhinoceras tichorJiinus, Elephas, Hippopotamus, etc. ; flint imple- 

 ments have also been found. A deposit of gravel at March contains 

 marine shells. 4. Older Peat, 5. Buttery Clay. 6. Newer Peat. 

 Next follow five appendices to the work. The first contains an 

 account of the Upware Sections, with which the readers of this 

 Magazine are well acquainted. The second, an account of the Koslyn 

 Pit, El}?-, reprinted from this Magazine. Third, a short account of 

 the Hunstanton Eed Eock, which Mr. Bonney considers probably 

 to represent palEeontologically the Cambridge Green sand. Fourth, 

 on the Water Supply of Cambridge, which is derived from three 

 sources: 1. Old river gravels; 2. From springs at the base of the 

 Lower Chalk ; 3. From artesian wells driven through the Gault into 

 the Neocomian Sands from 100 ft. to 150 ft. deep. Fifth, on the 

 Building Stones, etc., employed in Cambridge — the white bricks 

 froni the Gault ; red bricks of St. John's College from London Clay 

 of Suffolk ; Magnesian Limestone, the lower part of King's College 

 Chapel ; Inferior Oolite from Aislaby, near Whitby, great room of 

 University Library and Woodwardian Museum ; Lincolnshire Lime- 

 stone, King's College Chapel, New Courts of St. John's and Trinity, 

 etc. : Bath Oolite, University Press and Observatory ; Portland 

 Oolite, Senate House, fagade of University Library, Fitzwilliam 



