318 Supplement to the Comparative Estimate 



This must be so if our earth was the former sea bed, but if its 

 surface was merely covered by the diluvian waters, for about 

 twelve months, though they might for a time have caused a lower 

 temperature than prevailed in it prior to the deluge, yet it would 

 eventually recover, on drying, its original temperature, but by no 

 means become hotter than before. Thus, to whatever period we 

 refer, we find the climate of Siberia or Yorkshire equally un- 

 adapted, as at the present day, for elephants, hyaenas, #c, to 

 have lived in them, and " that discovery becomes collateral de- 

 monstration, that the animals, whose remains are found in them, 

 did not arrive there in a state of life, but of death, and therefore 

 at the period and by the means which we have been enabled to in- 

 vestigate and assign." 



In the German cave mentioned by Cuvier, scarcely any exuviae 

 of graminivorous animals were found ; their contents consisted 

 chiefly of the bones of bears, mixed with those of the hyaena, wolf, 

 fox, tiger, fyc. The difference between these animal associations 

 and those of the Kirkdale cave, sufficiently indicates them all to 

 have been as fortuitous as those in the Val d'Arno confessedly 

 are ; and although the hypothesis would account for the absence 

 of graminivora, by supposing the bears to have preferred vegetable 

 to animal food, the attempt cannot explain why they are associated 



has been proposed by Mr. Miller. {Trans- Wern. Soc. vol. iv. part 2; and 

 /Irmals of Philosophy, New Series, vol. vi. 



The system of ventilation adopted in mines, causes a current of air to de- 

 scend from the surface, and to traverse the deepest workings, and afterwards 

 to ascend. The air thus sent to the bottom is necessarily condensed in pro- 

 portion to the depth of the mine, and from its diminished capacity for heat, has 

 its temperature proportionately elevated. " The air, thus heated, traverses the 

 works, and imparts its heat to the strata ; it then ascends, and is succeeded by 

 a fresh portion of air from the surface, which in the same way becomes heated, 

 and imparts its heat to the strata, and they, in turn, communicate it all around. 

 Thus in a long course of working in a deep mine, the air at the bottom is heated, 

 and also the rocks to a considerable depth ; and when the working ceases, 

 the mine takes a long time to lose its temperature ; and this is found to be the 

 case, particularly when the mine becomes full of water, the water being found 

 at first of a high temperature, and gradually to lose its heat, which is in con- 

 sequence of the strata imparting theirs to the water, and as soon as they have 

 given out all their beat, the water indicates the mean temperature nearly of 

 the place. 



" The reverse takes place in an old mine when re-worked ; in that case, the 

 temperature rises gradually as the working continues ; and in those mines 

 which are not worked, but in which the ventilation still goes on, I believe it 

 will be found that they do not lose more of their temperature than can be 

 placed to the abstraction of the other causes of heat in working mines, such 

 as that produced by the men and the lights. 



"The exact quantity of heat given out by air in proportion to its conden- 

 sation, it is difficult to ascertain, but every day's experience proves it to be 

 very considerable; and, I believe, this, added to the other obvious sources of 

 beat in mines in a state of working, will be found sufficient to account for their 

 high temperature." 



Wc believe so too. 



