242 Mr Hen wood on the temperature of Mines. 



effects are doubtless variously modified in different places by 

 the nature and thickness of the strata, and the more or less 

 pervious state of the veins ; besides, the workings communicat- 

 ing with the shafts are in some mines much more open and 

 excavated than in others ; and, considering all these circum- 

 stances, we might anticipate that the results of experiments on 

 the temperature of water in stopped mines must be discordant 

 and inconclusive as to the actual heat of the earth itself, how- 

 ever strongly they may corroborate the truth of its existence." 

 In connection with this part of the subject it may be men- 

 tioned, that the stopping of one of the engines at the united 

 mines permitted the accumulation of water in the two deepest 

 galleries, viz. 190 and 200 fathoms deep, which continued for 

 two days. Immediately on its being pumped out, and before 

 the mines had resumed their operations, the temperature of 

 the upper one was 87°.5 and of the lower 88°. The observa- 

 tions being repeated some days after the workmen had recom- 

 menced operations, the temperature was found to have rather 

 diminished than otherwise. The same conclusion, resulting 

 from various views of the subject, seems to put the fact be- 

 yond dispute, although it does not appear that the ratio of in- 

 crease can be so readily determined. Notwithstanding some 

 few insulated facts had been previously noticed by other philo- 

 sophers, it will be seen from the preceding observations that 

 to Mr Fox we are indebted for the first annunciation of the 

 general law, as well as for a great portion of the information 

 which has now so satisfactorily established its accuracy. That 

 the matter was thus correctly viewed on the continent, he had, 

 in February 1820, the satisfaction of learning from an eminent 

 French philosopher, who observes, that *' Baron Humboldt, 

 who had previously noticed similar facts in the mines of Mex- 

 ico, and who then attributed the augmented temperatwe to ac- 

 cidental causes, since the experiments of Mr Fox have been 

 communicated to him, unites in the opinion, that this increase 

 of heat in the interior of the earth is a general fact, and not 

 dependent on local circumstances. He wished that the expe- 

 riments should be multiplied, and that, by keeping them as 

 free as possible from all disturbing influences, the question 

 might be placed beyond doubt.'' The influence of this im- 



