216 GENEVA SOCIETY OF PHYSICS AND NATURAL niSTORY. 



pentodes of Professor Dove) in order the better to detect the variations 

 of the elements which had furnished the monthly mean temperatures, 

 and to ascertain whether the meteorological tlieory by virtue of which 

 M. Ch. Sainte-Claire Deville admitted the more or less regular return of 

 anomalous cold spells at certain periods of the year, had or had not any 

 foundation in fiict. The plotted means of these pentades (or tive-day 

 periods) naturally gives a more nndulatory line than the regular theo- 

 retical curve of the monthly means, and if there existed anomalous causes 

 at certain fixed epochs, we should find the duration proper to each of 

 those epochs traced in a manner altogether more decided in proportion 

 as the observations are extended over a greater number of years. Now, 

 M. Plantamour found that the very reverse was the case, and the curve 

 of the mean temperatures of the pentades of the fifty years approaches 

 more nearly the regular theoretic curve than that which had been cal- 

 culated for the first forty years only. The annual mean for the last fifty 

 years is 9^.345 0. (480.821 F.). The warmest year of the series, 1834, 

 had a mean temperature of 10^,99 0. (510.78 F.); the coldest, 1851, one 

 of 70.80 C. (400.13 F.). The period from 182G to 1834 contains seven 

 warm and two cold years; that from 1835 to 1860 gives twenty-two cold 

 -and only four warm years ; and in the last fifteen years there have been 

 thirteen warm and two cold. But there is no regularity in these varia- 

 tions, which, contrary to the ideas of certain meteorologists, afford 

 nothing which substantiates any coincidence between them and the 

 periods of eleven years which have been observed for the epochs of the 

 minima and maxima of the solar spots. 



Professor Gautier read a second account of the meteorological observa- 

 tions made at Labrador, at five different stations, by the Moravian mis- 

 sionaries. That of Hoffenthal gives the mean temperature of five years, 

 from 1869 to 1873, at — 3o.03 C. (260.55 F.), vrhile the annual mean tem- 

 perature of Edinburgh is + 80.4 C. (46.47 F.). The winter and spring 

 are very cold, while the summer and autumn are relatively mild. The 

 mean diurnal variation, which is 4o,45 0. (80.OI F.), attains at times to 

 220 C. (390.6 F.). The extreme temperatures observed at the station of 

 Roma were, on the 3d of February, 1873, — 350 C. (—310 i^^.)^ and August 

 21, 4- 240 C. (750.2 F.). The greatest number of auroras observed there 

 occurs in the months of January and February. 



Professor Colladon read to us a work, which will be published in our 

 memoirs, upon the great hail-storms, one of which devastated the canton 

 of Geneva on the 7th and 8th of July of the past year, and the other 

 Savoy and Bas-Valois, twelve hours afterward, and which coincided 

 with violent storms between Lucerne and Zurich, and with another in 

 Ardeche. The storms moved at a velocity of 50 kilometres (31 miles) per 

 hour and the height of the hail-cloud was determined to be 2,000 metres 

 (6,600 feet). M. Colladon recognized four different types of hail-stones. 



The same member communicated an article upon the effect of a thun- 

 der-bolt on the trunks of two Lombardy poplars of different dimensions 



