in various Substances. 



The result of these experiments, I confess, surprised 

 me not a little; but the discovery of truth being the 

 sole object of my inquiries (having no favourite theory 

 to defend) it brings no disappointment along with it, 

 under whatever unexpected shape it may appear. I 

 hope that further experiments may lead to the dis- 

 covery of the cause why there is so little difference in 

 the conducting powers of air of such very different de- 

 grees of rarity, while there is so great a difference in 

 the conducting powers of air, and of the Torricellian 

 vacuum. At present I shall not venture any conjec- 

 tures upon the subject; but in the mean time I dare 

 to assert that the experiments I have made may be de- 

 pended on. 



The time of my stay at Manheim being expired (hav- 

 ing had the honour to attend thither his most Serene 

 Highness the Elector Palatine, reigning Duke of Ba- 

 varia, in his late journey) I was prevented from pursu- 



