312 VHILOSOPHICAL TRANSACTIONS. [aNNO 17/4. 



derably exhausted ; or the waters have deviated from their former course, and are 

 now only partially distributed over this stratum. 



XVII. Remarh on the Aurora Borealis. By Mr. Winn. p. 128. 



I believe the observation is new, that the aurora borealis is constantly suc- 

 ceeded by hard southerly, or south-west winds, attended with hazy weather and 

 small rain. I think I am warranted from experience to say constantly ; for in 

 23 instances that have occurred since I first made the observation, it has invariably 

 obtained. 



The gale generally commences between 24 and 30 hours after the first appear- 

 ance of the aurora. More time and observation will probably discover whether 

 the strength of the succeeding gale is proportionate to the splendor and vivacity 

 of the aurora, and the distance of time between them. I only suspect that the 

 more brilliant and active the first is, the sooner will the latter occur, be more 

 violent, but of shorter duration, than when the light is languid and dull. 



Xnil. Experiments concerning the Different Efficacy of Pointed and Blunted 

 Rods, in Securing Buildings against the Stroke of Lightning. By W. Hen- 

 ley, F.R.S. p. 133. 



From an accident which lately happened to the chapel in Tottenham-court 

 road, where a poor man was killed, the gentlemen who have the care of that 

 building were desirous of erecting a proper conductor to prevent such accidents 

 in future; which was done accordingly under Mr. H.'s direction, except 3 points 

 at the top, to which he rather inclined to prefer a single one. On this occasion, 

 he was willing to obtain the best information he could, on the question, whether 

 the preference be due to points or knobs, for the termination of conductors; for 

 which purpose he made the following experiments. 



Exp. 1 . He placed 2 of Mr. Canton's electrometers, a and b, pi. 10, fig. 2, insu- 

 lated, on stands of sealing-wax, about^7 inches asunder, and as many from the end 

 of a prime conductor, which was 1 Benches long, and 14- inch in diameter; and had 

 a ball at each end, 1\ inches diameter; the diameter of the electrical globe being 

 9 inches. On the top of the box a, was placed a wire, projecting 3 inches from 

 the end of it, and terminated by a ball -|- inch in diameter. On the top of the 

 box B, was placed a sharp-pointed wire, projecting also 3 inches from its end. 

 The knob and point were now exactly at the same distance, namely, 7 inches 

 from the end of the conductor. Then, giving the winch 5 or 6 turns, the light 

 cork balls, hanging from the box a, were repelled to the distance of 1 inch from 

 each other; but those hanging from the box b, separated full 2 inches. Then 

 touching the prime conductor with a finger, the balls at a closed, while those at 



