136 



mercurial one. The most striking result of the comparison between 

 the two, is the very near coincidence of the elasticity of the aqueous 

 vapour, as deduced from the experiments, with its amount, as deter- 

 mined from calculation, in a range of temperature from 58° to 74°. 

 But a gradually increasing difference was at length perceptible, show- 

 ing that gaseous matter had by some means insinuated itself into 

 the tube. When this became no longer doubtful, the boiler was 

 opened, and it was found that a portion of the liquid oil had escaped; 

 and that the remainder had become covered with large flakes of a 

 mucilaginous substance, by means of which it is probable that a 

 communication had been established between the air and the water. 

 The water had, however, retained its purity, and no indication was 

 afforded of the metal having been anywhere acted upon. The au- 

 thor recommends that if these researches are prosecuted, the water 

 should be covered with a stratum of oil of four or five inches in depth, 

 which he has reason to think will form an effectual barrier to all 

 atmospheric influence. 



11. " Hourly Observations on the Barometer, with experimental 

 investigations into the phenomena of its periodical oscillation," by 

 James Hudson, Assistant SecretaryandLibrarian to theRoyal Society. 

 Communicated by J. W. Lubbock, Esq. M. A., V.P. and Treas. U.S. 



Mr. Lubbock having found, from his examination of the meteoro- 

 logical observations made daily at the Royal Society, that they af- 

 forded no satisfactory result as to the daily variation of the barometer 

 in consequence of the too great length of the intervals between the 

 times of observation, the author undertook the task of making a 

 series of hourly observations for a period sufficiently extensive to 

 furnish preliminary data for explaining the anomalies of the baro- 

 metrical oscillations. The present paper contains these hourly ob- 

 servations, amounting to about 3000 in number, and made in the 

 months of April, May, June, and July, 1831, and in those of Janu- 

 ary and February of 1832. The standard barometer of the Society 

 has been observed for about 16 or 18 hours during the day, through 

 a period of 75 days ; and also at every hour, through the whole 

 twenty-four hours, for 30 days: the water barometer every hour, 

 day and night, for 15 days; and the mountain barometer also every 

 hour, day and night, for the same period. The relative levels of the 

 surfaces of the fluids in the cisterns of each of these barometers, 

 were accurately determined by Mr. Bevan. The most striking re- 

 sults afforded by these observations are exhibited by means of linear 

 representations in four drawings which accompany the paper. The 

 respective variations from each general mean, being referred, ac- 

 cording to a given scale, to the mean line, and their points of di- 

 stance from it, at each successive hour, being connected together by 

 straight lines, the barometrical and thermometrical changes being 

 each referred to the same scale, exhibits the striking connexion that 

 exists between them. The comparison of the simultaneous move- 

 ments of the three barometers shows the general accordance of their 

 mean variations ; and the precession in time, by about an hour, 

 of the mean motions of the water barometer over those of the stand- 



