a8o On the Tones produced by an Organ-pipe 



gas, as a heavier fubftance, a lower tone ; and that a mix- 

 ture of thefe two would have given a mean tone between 

 both, Exj>erience, however, fliews that each of thefe two 

 ^xpanfible fluids, as I have already faid, gives a higher tone 

 than atmofpheric air; and that a mixture of them gives a 

 tone higher than either of thefe can give alone, and per- 

 fectly fimllar to the tone of atmofpheric air. The quantity 

 of oxygen gas mixed with the azotic gas might, according 

 to appearance, be at firft about a fourth ; afterwards a third, 

 or fomewhat more ; which however made no confiderable 

 variation in the tone. I am of opinion, therefore, that the 

 imknovvn caufe which occafions a mixture of thefe two fub- 

 ftances to vibrate quicker than each of them taken fingly, 

 may alfo occafion found to be conducted with greater velo- 

 city than it ought, according to common theory, through 

 atmofpheric air, which has the fame component parts as 

 the above mixture. This greater velocity fcems to imply 

 rather a chemical than a merely mechanical mixture of thefe 

 fluid.-:. But this is coiitradiSed, befides other obfcrvations, 

 by one in particular of that acute and diligent philofopher 

 Profelfor Rcmigius Dottier of V^icnna, who fuffered common 

 air to 'iand ai)ove a year untouched in a glafs tube five feet 

 in length and one and a half in diameter, which was well 

 flopped both at top and bottom, and at the end of that time 

 the component parts of the air were in fome meafure fepa- 

 rated from each other according: to their fpecific gravity ; {o 

 that a lighted taper was extinguiflied in the lighter azot 

 found at the top, while another burnt in the heavy oxygen 

 jgas at the bottom with more ftrength than in atmofpheric air. 

 Hydrogen gas gave a far higher tone than atmofpheric 

 air; v..ith that extricated by iron and the fulphuric acid, the J 

 difference -wiis about an octave ; with that by zinc and the m 

 muriatic acid, it was nearly an oftave and a whole tone; by I | 

 ihat from the fleaai of water conducted through a tube of 

 ignited iron, it was fomewhat above an odave and a fmall 



•third. 



