the Depth of the Mines in the Hartz. 413 
kinds in the mines muft in' feme meafure affeft the com- 
mon laws of the air’s elafticity in different degrees of 
heat, if not its abfolute elafticity. On re fteflingy however, 
on this lingular conformity of the air in mines with the 
external air, I foon found the caufe of it in the extreme 
care taken to procure a circulation of external air in the 
mines, in order to prevent the pernicious effects of the 
exhalations: fo that the fame means, which really pre- 
serve the health of the miners in their fubterraneous 
abodes, give the air which circulates in them, and more 
efpecially that of the pits in which are the principal 
currents, the properties of the external air as to baro- 
metrical meafurements. Doubtlefs this is the caufe of 
that interefting phenomenon, as fatisfadlory for the fe- 
curity it gives to the lives of the miners, as for the ap- 
plication of the laws of aerometry: this was again con- 
firmed by obfervations I made fome days after in other 
mines, 
yqui fe repandent dans les mines, devoient y alterer les loix communes de l’elafti- 
cite de Fair en differens degres de chaleur; et peut-etre fon elafiicite abfoluec 
Mais en reflechiflant enfnite fur cette linguliere conformite de Fair des mines., 
avec Fair exterieur, j’en apper^us la caufe dans le foin extreme qu’on prend d'y 
faire circuler Fair exterieur, pour empecher les mauvais effets des exhalaifons 0 
Ainu les memes moyens qui confervent reellement la fante des mineurs dans 
leurs demeures fouterraines, donnent a Fair qui y circule, et furtout dans les 
puits, ou font les principaux courants, les proprietes de Fair exterieur dans les 
mefures barometriques. C’eft la fans doute la caufe de cet interelfant pheno- 
> inene, aulli tranquillifant fur le fort des mineurs, que fur Fapplication des regle-s 
d’aerometrie, Ce qui fe confirme encore par d’autres obfefvations que je fis 
\ .quelques 
