THE GEOLOGIST. 



We figure a shell from the white chalk, one valve of an oyster 

 with another smaller one attached to the internal surface. The 

 first oyster must have lived and died, its animal substance must 

 have been decomposed, or have been eaten out by the scavengers of 

 the deep, ere the second could have attached itself to the inner surface 

 of its valve, and this smaller one must have lived and grown from 

 its almost microscopic state of fiy to the size of the second oyster 

 probably of two years' growth — for the oysters of the chalk are small 

 and thin. Suppose this ; then it must have taken more than two 

 years before the slowly-falling sediments of the Cretaceous Sea had 

 accumulated to the extent of a few stout sheets of paper. Now 

 the ordinary aggregate thickness of the three associated chalks, 

 upper and lower white, and grey, is not much less than a thou- 

 sand feet, and all this mass was formed at no greater maximum rate. 

 The fossil shells and fish we find imbedded in its strata, of course 

 lived and died in its waters — they were living-beings in those 

 remote days. So self-evident does this fact seem, — although it was 

 once stoutly discussed — that I have not dwelt upon it, nor shall I, 

 as any doubts on this point will be swept away in the natural 

 progress of our remarks. And yet the chalk is itself but a 

 portion of the Cretaceous group or system of rocks, and that 

 system but one amongst many systems formed at no quicker rate. 



(To be continued J 



FOREIGN CORRESPONDENCE. 



By Dr. T. L. Phipson, of Paris, 



Late Mortality amongst distinguished Geologists — Action of Water on 

 Plutonic Hocks — Artificial Production of Minerals ; A ragonite formed 

 in Steam Engines ; Bubies and Sapphires — Oscillation of the North 

 and South Coasts of France — The Sand of the Desert of Sahara — 

 The Coryphodon — Neidy discovered Foot-prints of Extinct Animals — 

 Researches on the Flora of the Tertiary Formations. 



Before entering upon the regular correspondence with which we 

 hope to entertain our readers each successive month, by making 

 known to them every new and important geological fact as it comes 



