228 Royal Society. 



periinents made during some very peculiar summer weather were 

 influenced by a want of temperature-equilibrium between the various 

 parts of the apparatus, the result appearing to be that the gas- 

 effect for the ebonite disk was abnormally large. 



49. Our conclusion from the evidence before us is, that the resi- 

 dual effect is a surface-effect more deeply seated than the gas-effect, 

 but distributed outwards from the centre to the circumference, very 

 much in the same manner as the gas-effect. The residual effect 

 likewise appears able to penetrate a chamois-leather blind without 

 any perceptible diminution. We regard these conclusions as pre- 

 liminary, and shall endeavour in our future experiments to procure 

 additional evidence of these properties of the residual effect, as well 

 as to obtain new facts regarding it. In the mean time, as the sub- 

 ject is one of interest, and has been already too long delayed, we 

 have not hesitated to bring these results before the notice of the 

 Royal Society. 



In concluding we would desire to express our thanks to Mr. P. 

 Kingdon for his assistance to us in many of these experiments. 



June 19. — William Spottiswoode, M.A., Treasurer and Vice- 

 President, in the Chair. 



The following communication was read : — 



" The Diurnal Variations of the Wind and Barometric Pressure 

 at Bombay." By P. Chambers. 



The object of this paper is to bring to notice a remarkable 

 relation that has been found to exist between the diurnal variations 

 of the wind and the barometer at Bombay. 



The observations made use of are the records of a Kobinson's 

 anemograph during the first three years of its performance, viz. 

 from June 1867 to May 1870, and the corresponding hourly ob- 

 servations of the barometer and the dry- and wet-bulb thermometer 

 made at the Government Observatory, Bombay. 



The mean results for each hour of the day during the whole 

 period and the mean diurnal variations of each element are tabu- 

 lated and graphically represented by figures. The diurnal variation 

 of the wind is then investigated, the most influential part of which 

 is attributed to the land- and sea-breezes which blow from E.S.E. 

 and W.N.W., and are shown to follow mainly the same law of 

 progression as the temperature of the air, thus affording confirma- 

 tory evidence of the truth of Halley's theory of the trade-winds as 

 applied to land- and sea-breezes. 



Some peculiarities of the curve representing the land- and sea- 

 breezes are then pointed out, and these, the writer concludes, are due 

 to the superposition of another distinct variation having two maxima 

 and two minima in the twenty-four hours, like the barometer va- 

 riation ; and he supports his views by a reference to the variation 

 of the east components of the wind in the months of July and 

 August, when the land- and sea-breezes have almost disappeared. 

 This is found to exhibit a decided double period. The north com- 

 ponents of the land- and sea-breezes are then approximately elimi- 

 nated from the north components of the whole variation, and the 



