114 PHILOSOPHICAL TRANSACTIONS. [ANNO 1781. 



dry tow on fire at the distance of 5 yards from the muzzle of the barrel. He 

 repeatedly discharged large wads of tow and paper, thoroughly soaked in the 

 most inflammable fluids, such as alkohol, setherial spirit of turpentine, balsam 

 of sulphur, &c. : but. none of them were ever set on fire by the explosion. 

 Sometimes he discharged 3 or 4 spoonfuls of the inflammable fluid, by interpos- 

 ing a very thin wad of cork over the powder, and another over the fluid ; but 

 still with no better success. The fluid was projected against the wall as before, 

 and left a mark where it hit ; but it never could be made to take fire ; so he 

 gave up the attempt. If it had succeeded, probably it would have turned out 

 one of the most important discoveries in the art of war that have been made 

 since the invention of gunpowder. 



XFI. A Luminous appearance in (he Heavens. Bi/ T. Cavallo, F.R.S. p. 32Q 

 At about half past Q, March 27, 1781, a white light began to be seen in the 

 sky, which became gradually more and more dense till 10 o'clock, at which time 

 it formed a complete luminous arch from east to west. At that time it appeared 

 to be an arch of about 7 or 8 degrees in breadth, extended nearly from east to 

 west. Its western part quite reached the horizon ; but the eastern part of the 

 arch seemed to begin at about 50° or 60° above the horizon. It did not pass 

 through the zenith, but at about 8° or 10° southward of it, and it was nearly 

 perpendicular to the horizon. 



The whiteness of this arch was much denser than that of any aurora borealis, 

 though it did not cast so much light on terrestrial objects. Towards the middle 

 it was so dense, that the stars over which it passed were eclipsed ; but the sides 

 of this luminous arch were more faint and transparent. At about f past 10 it 

 began to lose its brightness, and then vanished gradually, so that at 1 1 o'clock 

 none of it could be perceived. As soon as any part of this arch lost its dense 

 whiteness, the stars appeared through it quite distinct ; so that it could not be a 

 cloud. The light also seemed to vanish without change of place ; for it did not 

 appear to be dispersed through the sky, or to be driven in any direction. This 

 extraordinary appearance seemed quite distinct from the aurora borealis, for the 

 following reasons; viz. because it eclipsed the stars over which it passed; be- 

 cause its light, or rather its white appearance, was stationary and not lambent ; 

 and because its direction was from east to west. The atmosphere was in other 

 respects very serene, the stars shining very bright, and no cloud appearing. The 

 northern light was exceedingly faint, and very low about the northern point of 

 the horizon. The wind was nearly north-east, and it could be just felt in the 

 streets. 



