[ 385 ] 



were interrupted, not extending the whole length of the tube, 

 neither would they appear when the excited tube was pre- 

 fented to the end, but when to the middle only of the ex- 

 haufled one; and^it was remarkable, that corufcations exadlly 

 refembling the above, in their form, &c. except that they ap- 

 peared when the excited tube touched any part of the other 

 one, and that they were fo faint as to be fcarce vifible in a 

 room made quite dark, firfl began to appear, when the rare- 

 fadlion, as fhewn by the pear-gage, was 4000 : the ftandard- 

 barom"^ above-mentioned being, at the fame time, at 30,1, 

 and the baromrgage at 30,12. When the rarefacSlion was 

 carried beyond this, fo as to raife the mere''' in the baromr- 

 gage, a little higher in feveral trials, and to advance that 

 fhewn by the pear-gage fometimes up to 26000, the appear- 

 ances were the fame, but the gleams of light flill fainter; 

 they were a colourlefs pale white ; the corufcations, which 

 were fcarce vifible, feemed conical pointed, waving or ftreaked, 

 and did not extend the whole length of the tube, exhibiting 

 the moft perfedl refemblance of the thin pale coloured Aurora 

 Borealis. 



In the intermediate degrees of rarefadlion, between 100, and 

 4000 (indicated as above by the gages) the phsenomena were 

 as follows : 



At 300, the prefentatlon of the excited tube 7icar to the 



«xhaufted one, firft occafioned continvied flafhes in it, filling 



Vol. VI. 3 C its 



