384 Mr. F. Chambers on Barometric Pressure, fyc. [June 19, 



V. "On the Mathematical Expression of Observations of Com- 



plex Periodical Phenomena, and on Planetary Influence on 

 the Earth's Magnetism." By Charles Chambers, F.R.S., 

 and F. Chambers. Received May 26, 1873. 



(Abstract.) 



The authors propose in this paper to determine, by Bessel's method, a 

 mathematical expression for a periodical phenomenon from observations 

 which are affected by one or more other periodical phenomena, and to 

 find criteria for judging of the extent to which the expression is affected 

 by these other phenomena : to find also the true period from observations 

 of a single periodical phenomenon of which the period is only approxi- 

 mately known ; or, having found an expression for a period of known 

 approximation to the truth, to find from it the expression for the true 

 period. In the course of these inquiries, certain ambiguities which affect 

 similarly Bessel's expression for a single periodic phenomenon and the 

 results here arrived at are remarked upon ; and, finally, the results are 

 applied to determine the nature of periodic planetary phenomena in a 

 particular case. 



VI. " The Diurnal Variations of the Wind and Barometric Pressure 

 at Bombay." By F. Chambers. Communicated by Charles 

 Chambers, F.R.S., Director of the Colaba Observatory, 

 Bombay. Received May 26, 1873. 



(Abstract.) 



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 Robinson's anemo- 

 graph during the first three years of its performance, viz. from June 

 1867 to May 1870, and the corresponding hourly observations of the 

 barometer and the dry- and wet-bulb thermometer made at the Govern- 

 ment Observatory, Bombay. 



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

 and the mean diurnal variations of each element are tabulated and gra- 

 phically 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 confirmatory 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 super- 



