the Depth of the Mines in the Hartz. 405 
ingly applied to by him, becaufehehad a Barometer made 
of a Angle bent tube upon the principle of mine. During 
my journey Mr. erxleben was fo good as to obferve this 
Barometer very frequently ; and it is from his obferva- 
tions that the heights of fome of the places of the Hartz, 
which I lhall mention, have been determined. 
At my return, I placed my Barometer near that of 
Mr. erxleben ; and, when they were expofed to the fame 
temperature,, there was found no difference between- 
them. 4 
This example, joined to all thofe with which my own 
experience has furnifhed me for a long time paft, makes 
me more and more folicitous that the lovers of natural 
philofophy would fix the fcale of their Barometers with 
citterns (very convenient ones no doubt for common ufe) 
by comparing them with a Barometer made in the form 
of 
tube recourbe, fur la pri-ncipe du mien. M. erxleben eut la bonte d’obferver 
tres frequemment ce Barometre pendant mon voyage; et c’eft d’apres fes obfer- 
vations, que j’ai determine les hauteurs de quelques endroits du Hartz dontje 
ferai mention. 
A mon retour j’apportai mon Barometre aupres de celui M. erxleben; et 
quand ils furent reduits a la meme temperature, il ne fe trouva entr’eux aucune- 
difFerence. . 
Cet exemple fe joignant a tous ceux que mes propres experiences nFontfourni 
depuis long terns, me fait dehrer toujours davantage que les Pnyficiens veuil- 
lent bien fixer l’echelle de leurs Barometres a refervoir (tres commodes fans doute 
pour l’ufage ordinaire) en les comparant a un Barometre fait en forme de fiphon ; 
3 ct 
