88 CORRESPONDENCE. 



the demonstration of which exalts and sanctifies the labours of sci- 

 ence in her investigations of the organizations of the living world." 



Under the old Pliocene formation we come immediately to the 

 chalk, which in this neighbourhood has not been penetrated. The 

 fossil remains which I have been enabled to collect, consist of the 

 following, viz. : Snocerami, several species ; Echini, ditto ; Plagi- 

 ostoma, Spinosa, Serpula, Dianchora, Pecien, Terebratula, Ventri- 

 culite, Pentagonaster (one of which I possess, the five sides being 

 complete), with numerous ossiculi, and fishes and reptiles teeth: 

 the fishes teeth belong to the Squalus tribe. In some parts of the 

 plastic clay is occasionally found a thin bed of chalk, deposited be- 

 tween the new and old pliocene formations. Immediately on the 

 bank of the Thames there is a dark-coloured bed of plastic clay, 

 lying over a stratum of six feet thick, containing an immense 

 quantity of vegetable matter, principally the remains of the Yew 

 tree, sufficient to answer the purpose of fuel, if treated after the 

 manner of making peat. The greater number of shells, both in 

 the fresh-water and marine formations of this tertiary series, are so 

 nearly allied to the present genera that we may conclude the ani- 

 mals by which they were formed to have discharged similar func- 

 tions in the economy of Nature, and to have been endowed with 

 the same capacities of enjoyment as the cognate molluscs of living 

 species. 



Those geologists who are not averse to presume that the course of 

 Natui'e has been uniform from the earliest ages, and that causes now 

 in action have produced the former changes of the earth's surface, 

 will consult the ancient strata for instruction in regard to the re- 

 pi-oductive effects of tides and currents. It will be enough for them 

 to perceive that great effects now result from the operation of these 

 agents in the inaccessible depths of lakes and seas ; and they will 

 then search the ancient lacustrine and marine strata for proofs of 

 analogous effects in times past. Thus we have a collection of facts, 

 a series of epochs anterior to the present time, and of which the suc- 

 cessive steps may be ascertained with perfect certainty, although 

 the periods which intervened cannot be determined with an)'- degree 

 of precision. These epochs form so many fixed points, answering 

 as rules for directing our inquiries respecting this ancient chronolo- 

 gy of the earth. 



J. Grantham. 

 Crayford, Kent. 



