Mr Macvicar on a remarkable electrical Cloud. 117 



Art. XVIII. — Notice of a Remarkable Electrical Cloud. By 

 the Reverend John Macvicar, A. M. Lecturer on Natu- 

 ral Philosophy in the University of St Andrews. Commu- 

 nicated by the Author. 



On the evening of the 23d May, about 8 p. m., when I was 

 returning from Strathmore, and had gained an eminence on 

 the Sidlaw range, I rested to admire the contrast in the aspect 

 of the sky over the highlands which bounded the horizon in 

 the region of the sun, and over Fife and the ocean which lay 

 in the opposite quarter. The western and northern sky was 

 very clear and serene, and almost destitute of colour, though 

 the sun was not far from setting. Between that horizon and 

 the zenith there were several small cumuli of their usual indigo 

 tint, with red on their aspects facing the sun. Their number 

 increased towards the region opposite the sun, so that the ca- 

 nopy in that quarter might be said to be covered with cloudy 

 matter, much in the state of cirro-cumuU at that elevation. 

 Beneath this stratum there were nimbi, a slight one over my 

 head, and some very heavy ones passing slowly from the west 

 over the hills of Fife, which form the southern bank of the 

 Tay, and tending towards the north. Where I was, there was 

 no sensible wind, but the cottage smoke was bending from the 

 east. In the nimbus over head (in its rain) a rainbow was de- 

 veloped, and its southern limb, which was formed upon a very 

 dense nimbus over the Tay, was extremely vivid, but the co- 

 lours were very much blended. In this vivid region a secon- 

 dary arch was developed. To the westward of the secondary 

 arch there was a heavy cloud, whose under aspect was strangely 

 illuminated, so that the cloud seemed as if actually formed of 

 rectilineal pencils of aqueous vapour, like the streamers of the 

 aurora inverted ; and what makes me trouble you with this de- 

 scription at all, is the circumstance that these illuminated pen- 

 cils of cloud lengthened and shortened, and changed their form 

 (though not their place) as fast and as distinctly as the stream- 

 ers of a moderately active aurora. They seemed to be direct- 

 ed towards the loftiest hills. The large one represented in 

 Plate II. fig. 9, which represents as dark the portions which 



