566 Heports and Proceedings — 



divisions of the Cbalk forms the subject of an Appendix by Mr. 

 Etberidge, wbo also describes and figures a number of new species 

 of Mollusca. Tbe " Cambridge Greensand," with its inchided 

 erratics and coprolites, is treated of under tlie heading of Chalk 

 Marl, and some account of the origin of the phosphatic nodules is 

 given. The origin of the flints of the Upper Chalk is also briefly 

 discussed, the authors attempting to account for the occurrence of 

 flints in regular layers, by considering that an "initial plane of 

 segregation " was given at repeated intervals by organic remains 

 strewn over the surface of the chalk mud ; and that the silica, 

 which at first was equally distributed throughout the water by which 

 the unsolidified jDortions of the mass was permeated, accumulated 

 along the same plane of decaying organisms, notwithstanding the 

 mud that was still being thrown down, and by which the forming 

 line of flint was buried. They "assume that the force, whatever it 

 may have been, would act upwards and downwards through some 

 definite thickness of the mud, and that until the sediment had 

 attained a certain height above such line, the silica would continue 

 to segregate along it, in and around its organisms. When that point 

 was reached no more silica would segregate along that particular 

 zone, the organic remains on the then existing floor would in a 

 similar manner serve as the nuclei of a new layer, and another line 

 of flints would be at once commenced." This explanation is sug- 

 gestive, although it leaves much to be said, before the subject can 

 be said to be plain and easily understood. 



The description of the Glacial Drift occupies but a few pages ; it 

 comprises Boulder-clay, Marine Gravels and Loam. In a sub- 

 sequent chapter the authors enter at some length into the question 

 of the physical conditions under which the Glacial and Post-Glacial 

 Drifts were deposited ; and they express their conviction that the 

 Boulder-clay was mainly produced by the action of Coast-ice. 



The various Post-Glacial gravels are described in much detail, and 

 a map is given to show the courses of the Ancient and Modern 

 Eivers in Cambridgeshire. 



The lists of fossils from the various formations and localities are 

 very full. Details of well-sections and borings are given ; and 

 there is also a list of works on the Geology of Cambridgeshire, 

 compiled by Mr. Whitaker, who superintended the field-work and 

 has edited the Memoir. 



I^E:poI^TS j^istx) i=s-ooEEX)iisrca-s. 



Geological Society oe Loistdoi^. 



November 2, 1881. — E. Etberidge, Esq., E.K.S., President, in the 

 Chair. , 



Prof. Hughes called the attention of the Society to the work being 

 done by the Swiss PalcEontographical Society. He pointed out 

 that, the Swiss being a small nation, and their scientific men pro- 

 portionately few in number, it was a very spirited thing of them to 



