194 PROCEEDINGS OF THE SOCIETY OF 



occasion tliat Father Secclii also was occupied in the study of stellar spectra 

 compared with the solar spectrum; fourthl}-, M. Gautier presented lastly to the 

 society a plate oi' Father Secchi, representing the different appcij-ances of the 

 nucleus of the comet of 1862, differences which, as M. Wartmann, sr., has 

 pointed out, might result, at least in part, from the circumstance that the 

 observations took place at diff"erent hours. 



Professor I'lantamour announces that he has collated the series of observa- 

 tions made for twenty years on the latitude of the observatory of Geneva. 

 That latitude would be 46° 11' 5S".75, with a mean error of some hundredths 

 of a second. 



Mvtcorolog)/ and terrestrial jjJnjsics establishing a natural bond between 

 astronomy and jihysics properly so called, we shall first direct our attention to 

 several communications which wc owe to Professor Plantamour. Besides the 

 annual meteorological summary for Geneva and Saint-Bernard, published, as 

 usual, in the archives of the physical and natural sciences of the " Bibliolheque 

 Univcrselle,'" ]\I. Plantamour has communicated to the society an interesting 

 memoir relative to observations made at Geneva, for thirty-five years, on the 

 force and direction of the winds. lie has found that in winter the number of 

 northeast and that of southwest winds balance each others the northeast pre- 

 domiuates in spring and in autumn, the southwest in summer. The general 

 resultant is a little west of north, which proceeds from the fact that the mean 

 direction of northeast winds more nearly approximates to north than does the 

 mean direction of southwest Avinds to south. The above results are somewhat 

 mortified if the origin of the winds be taken into account and if local are dis- 

 tinguished from general winds. The former depend chiefly on the vicinity of 

 the lake and the variation of temperature in the twenty -four hours, giving rise 

 to a regular breeze morning and evening, analogous to breezes of the land and 

 sea. The memoir of 31. Plantamour has been lately published in his extensive 

 work on the climate of Geneva. (See page 1^, ct sequent.) 



The same savant read to the society a memoir on the diurnal variations of 

 the atmos[)heric pressure, a- memoir likewise published in the work just men- 

 tioned. After having passed in review and combated as insufficient the theories 

 proposed by MM. Krail and Dove, M. Plantamour concludes in favor of that 

 proposed by M. Lanion, according to which the phenomenon of the diurnal 

 variation Avould depend on two distinct influences, one resulting from the tem- 

 perature properly so called, the other from a kind of electric attraction, whose 

 nature is as yet completely unknown, but owing pjrobably to the action of the 

 sun. M. Plantamour founds his preference for this theory over the preceding 

 on the consideration that it furnishes the means of explaining the double diurnal 

 oscillation -which is obsei-ved in the barometer, while the influence of the tem- 

 perature, it would appear, ought to produce but a single one. The author 

 presents, in support of his opinion, a comparative table of the diurnal variation 

 of the temperature and of the barometer for Geneva and Saint-Bernard. 



To complete bur analysis of what relates to terrestrial physics and meteor- 

 ology, I have still to notice two communications, one from Professor de la Rive, 

 relative to an aurora ])orealis observed in the month of December, in Avhich the 

 rotation of the arch from east to west was perfectly evident, and another from 

 ]\I. Louis Soret, who has presented to the Society an apparatus constructed 

 according to his directions in the workshop of M. Schwerdt, an apparatus de- 

 signed for the measurement of heights by a determination of the temperature of 

 the ebullition of water. In the construction of this instrument, the chief object 

 of M. Soret has been to attain a perfect precision in thermometrical indications, 

 a condition which has heretofore been wanting. He has succeeded, on the one 

 hand, by surrounding the ball of the thermometer with two envelopes of vapor 

 instead of one, in abating the variations of temperature proceeding from with- 

 out ; and, on the other hand, he prevents the effect of an ebullition often too 



