310 Scientific Intelligence. [Oct, 



large, and they are distinctly divided into tenths. Each degree of 

 No. 1 occupies a space of '208 inch, and of No. 2 '130 inch. The 

 scratch upon the glass for the freezing point is very visible in both. 

 It is difficult to say for what purpose they were originally made, but 

 evidently for some experiments upon the freezing point of water ; and 

 if they had been expressly constructed to verify the present point, 

 they could not have been better contrived for the purpose. The bulbs 

 of both were plunged into pounded ice, in which they were left for 

 half an hour, and the height of the mercury was carefully taken by 

 two observers with the aid of magnifying glasses. The result of the 

 examination was, that in No. 1 the freezing point upon the scale was 

 0*4 degree too low, and in No. 2, 0*35 degree. There can be httle 

 doubt, I think, that the right cause of the phenomenon has been 

 assigned, viz. the change of form and capacity which the glass under- 

 goes from the pressure of the atmosphere upon the vacuum of the 

 tube." . 



III. Notice in regard to the Tempei'ature of Mines, 

 By Matthew Miller, Esq. MWS. 



The late experiments on the temperature of mines made in Corn- 

 wall, and in other countries, having given rise to various speculations 

 in regard to the distribution of heat in the crust of the earth, all of 

 which appear to me to be unsatisfactory, I now beg leave to offer for 

 consideration of the Society, an explanation, that does not seem liable 

 to the objections that have been opposed to the others. 



In every mine, with the exception of a few, which are level-free, 

 the ventilation is carried on by causing the air at the surface to de- 

 scend, and traverse the works, and then ascend. Now it is evident, 

 that if a portion of air from the surface be carried down to the bottom 

 of the mine, it will be condensed in proportion to the depth of the 

 mine ; and, in consequence of this condensation, will become heated, 

 and the degree of heat will of course be in proportion to the depth of 

 the mine. The air thus heated, traverses the works, and imparts its 

 heat to the strata ; it then ascends, and is succeeded by a fresh por- 

 tion 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 consequence 

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

 given out all their heat, 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 heal given out by air in proportion to its con- 



