174 



and expresses surprise that so much discussion should have taken 

 place on so simple a case ; he sees no difference between many Me- 

 talliferous Lodes and Faults. 



The subject of Organic Remains is next investigated, and the Modi- 

 fication produced by various physical causes on the distribution of Life, 

 particularly Animal Life in the sea. Diagrams are given to show that 

 Shells, contemporaneously enveloped by rocks now^ forming, would 

 probably not be of the same Species, even under the same parallels of 

 latitude ; but that the Species would be determined in some measure 

 by the relative depth of the water at different places, on the influx of 

 rivers, and other causes. Attention is particularly called to the man- 

 ner in which Organic Remains may be entombed in a series of deposits 

 along a gradually rising coast. 



Under the head of Mineralization of Organic Remains, the Author 

 shows that these bodies are not merely changed in character but in 

 reality. One substance being substituted for another, a cast for an 

 original, the Change varies in these bodies in proportion to their re- 

 spective Solubility. Carbonate of lime being more soluble than phos- 

 phate, shells change much more rapidly than bones. Silica in shells 

 follows the same law as in agates, entering their cavities by infiltra- 

 tion. 



The Author now gives a general Sketch of the various Rocks that 

 are known to us; he remarks that the Primary differ chemically from 

 the Secondary, and endeavours to account for the phsenomena con- 

 nected with animal and vegetable life, as exhibited in the several for- 

 mations, upon the theory of a gradual Loss of Heat by Radiation. Upon 

 this theory he would explain the Scanty Supply of Limestone in the 

 earliest Rocks. The effect of great heat would be to expel from water 

 the carbonic acid necessary to hold the carbonate of lime in solutions ; 

 and consequently Calcareous matter could not be deposited from 

 heated water. He observes also that the Conditions for an uniform 

 distribution of animal and vegetable life, would be more uniform in a 

 thermal than in our actual Seas, and, therefore, if the Ocean had be- 

 come gradually cooler, we should expect to find, as we do, genera and 

 species more diversified. 



The terms. Eocene, Miocene and Pliocene, are objected to, as pre- 

 judging an important question. Unless equal conditions obtained at 

 equal times in all places, the Miocene rocks of one country may be 

 of the same date as the Pliocene of another. The Author closes his 

 remarks on Erratic Blocks by observing, that, like the great contor- 

 tions and dislocations of strata, they teach us, while we duly appre- 

 ciate the continued and more tranquil effects which are daily before 

 our eyes, that we must not dismiss from our consideration Forces ot 

 greater Intensity 5 still bearing in mind, that however great these 

 last-mentioned forces may be when measured by the ideas commonly 

 entertained on such subjects, they are still insignificant when consi- 

 dered with reference to the entire spheroid on the surface of which 

 they act. 



Gentlemen, I have now brought to a close the account, which, in 



