10 Prof. Everett Observations of [Jan. 12, 



January 12, 1865. 



Major-General SABINE, President, in the Chair. 

 The following communications were read : 



I. "Account of Observations of Atmospheric Electricity at King's 

 College, Windsor, Nova Scotia." No. II. By JOSEPH D. 

 EVERETT, M.A., F.R.S.E., Professor of Mathematics in King's 

 College, N.S. Communicated by Professor WILLIAM THOM- 

 SON, F.R.S. Received December 21, 1864. 



My former paper* embraced the six months from October 1862 to March 

 1863. Since the latter date my observations have been continued as before, 

 the water-dropping method being employed until December 1st, since which 

 time burning matches have been used, as in the previous winter. 



The glass fibre of the station electrometer remained unchanged till July 

 31st, when it became loosened from its attachment, and was replaced by a 

 new and much thinner fibre, which has continued in use ever since. From 

 comparisons made with the portable electrometer, in the manner described 

 in my former paper, it appears that the change of fibre has increased the 

 indications in the ratio of 20'2 t.o 3'1. 



The principal observations have, as before, been made three times a day, 

 namely at 8 or 9 A.M., 2 P.M., and 9 or 10 P.M. ; but additional observa- 

 tions have frequently been taken at other hours, especially during the 

 months of May, June, and July, when they were much more numerous 

 than in any month included in the former paper. Each observation has 

 generally contained five air-readings the interval between the readings 

 being a minute, until September 16th, since which date it has been only 

 half a minute. I assume that this change cannot affect the mean result, 

 though it may to some extent influence the observed range. It was adopted 

 for convenience, the new fibre being found to admit of more rapid observa- 

 tion than the old. 



The following is a summary of the results of observations during rain or 

 other downfall, fog, and thunder and lightning the period included being 

 the eleven months from April 1863 to February 1864. 



Rain. With light rain the electricity is generally moderate, sometimes 

 very weak, and sometimes about double the average fair-weather strength. 

 These remarks do not apply to light rain immediately following heavy, the 

 electricity being often as strong during the intervals between heavy rain, 

 and for some time after its conclusion, as during its descent. Very heavy 

 rain is almost invariably accompanied by very strong electricity. 



Snow. Almost always positive, but occasionally a little negative inter- 

 mixed with positive ; and on one solitary occasion (February 1 6th) strong 

 negative sparks were drawn during a heavy fall of snow. On this occasion 

 strong positive electricity was also observed. It is worthy of remark that 

 * Read June 18, 1863, Proceedings, vol. xii. p. 683. 



