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Abstract

MR. BONNEY's short sketch of the geology of the neighbourhood of Cambridge will be a useful handbook to those students who wish to become practically acquainted with the geological features of the country round their temporary home. It makes no pretensions to be an exhaustive description, and happily is not written in a style suitable for cramming, but simply draws the attention of the careful reader to all the interesting points in connection with the geology of the district, and notices the various contributions to fact or theory made by previous writers, embodying many of Mr. Bonney's own observations. The first deposits described are the Oxford clay of St. Ives and the Elsworth rock, the true position of which latter is discussed; and then follows a notice of the coral reef at Upware, and the Kimmeridge clay at Ely. We have next a discussion of the coprolite and associated beds at Potton and Upware, which Mr. Bonney considers Upper Neocomian, and he thinks most of the fossils derived. After a short notice of the Gault comes a full discussion of the interesting questions connected with the so-called Upper Greensand. An admirable outline of its palæontology is first given, and the origin of its phosphatic nodules is then concluded to be analogous to that of flint, or what is here called concretionary action. With regard to its age, Mr. Bonney follows Mr. Jukes-Browne in considering it homotaxial with the chloritic marl, and a large part of its fossils derived from the Upper Gault. The chalk is dismissed with a very short notice, and an account of the Post Pliocene deposits concludes the sketch. These deposits are described under six divisions, the lowest being the true Boulder Clay. The most interesting of these is the “Fine Gravel of the Plains” which, has yielded so many mammalian remains. Five appendices follow: on Upware sections, the Ely pit, the Hunstanton red rock, the water supply, and building stones of Cambridge. The second of these might well have been omitted, for though it refers to an interesting case of a large chalk boulder, we are now sufficiently familiar with such instances of huge transported rocks to make it waste of time to discuss imaginary systems of impossible faults to account for its presence in some other way.

Cambridgeshire Geology; a Sketch for the use of Students.

T. G.

Bonney

By, Tutor and Lecturer in Natural Science, St. John's College. (Cambridge: Deighton, Bell, and Co., 1875.)