584 PHILOSOPHICAL TRANSACTIONS. [aNN0 1742. 



equable motion, and leaving behind it a narrow streak of light, whiter than the 

 globe itself, throughout its whole course. Towards the end it appeared less 

 than at the beginning of its motion ; and within 3 or at most 4 seconds, it 

 suddenly vanished. Its apparent velocity was nearly equal to half the medium 

 velocity of those usual meteors commonly called falling or shooting stars. 



The narrow luminous streak remained very distinct after the globe was gone; 

 and gave a fair opportunity for taking the elevation of this phenomenon above the 

 horizon, at the beginning and end of its motion, &c. which was found to be 20°. 

 This luminous tract, or path, seemed a right line, not quite parallel, but a little 

 inclined to the plane of the horizon, viz. highest towards the east. It was at 

 first very narrow, and pointed at each extremity ; but soon grew broader, and 

 within 20 minutes after the appearance, it was exactly like a long bright 

 rare cloud, discontinued in two places, above 3 times its first breadth, and a 

 little more inclined to, and elevated above the horizon, than it was immediately 

 after the motion of the globe. 



Some Conjectures concerning Electricity, and the Rise of f^apours. By J. T. 

 Desaguliers, LL. D., F. R. S. N° 464, p. 140. 



It is proper first to mention, by way of preliminary, that Mons. Du Faye's 

 assertion, of 2 sorts of electricity, is found to be true by observations and ex- 

 periments, viz. that bodies endowed with the vitreous electricity repel each 

 other, and attract those that have the resinous electricity : on the contrary, 

 those that are endowed with the resinous electricity repel each other, but attract 

 those that have the vitreous electricity. 



Dr. D. supposes particles of pure air to be electric bodies always in a state of 

 electricity, and that of the vitreous kind. 1st, Because particles of air repel 

 each other without touching, as has been deduced from experiments and ob- 

 servations. 



2dly, Because, when the air is dry, the glass tube rubbed, or only warmed, 

 throws out its effluvia, which the air drives back to the tube, whence they dart 

 out anew, and so move backwards and forwards with a vibratory motion, which 

 continues their electricity. 



adly. Because the feather made electric by the tube, and darted from it, 

 keeps its electricity a long time in dry air ; whereas, when the air is moist, the 

 moist particles, which are non-electric, being attracted by the feather, soon 

 make it lose this electricity, which also happens even to the tube in a little time. 



Hence it will be easy to account for a famous experiment of the late Mr. 

 Hauksbee, which is this — Having pumped out all the air from a glass globe, he 

 caused it to turn on its axis very swiftly, by means of a rope with a wheel and 



