402 



Mr. F. Chambers on the Variations [Dec. 7j 



points, I would rather refer to an elaborate series of experiments by Mr. 

 Crookes, in which this pump plays a most important part, shortly to be 

 brought before the Eoyal Society. 



Note. — Since writing the above description, while working with 

 McLeod's apparatus it has been found necessary to introduce an air- 

 trap similar to h, fig. 1, between the pinch-cock N and the apparatus, 

 as small bubbles of air were frequently seen creeping up the pipe p. 



II. ^^The Diurnal Variations of the Wind and Barometric Pres- 

 sure.''^ By Fred. Chambers,, Meteorological Reporter for 

 the Bombay Presidency^ and Acting Superintendent of the 

 Colaba Observatory Bombay. Communicated by Charles 

 Chambers^ F.E.S. Beceived November 9^ 1876. 



In a paper which was read before the Boyal Society in 1873, and which 

 was honoured with a place in the ' Philosophical Transactions ' of that 

 year *, I discussed the diurnal variations of the wind and barometric 

 pressure at Bombay, and deduced therefrom the fact that a system of 

 diurnal wind-currents moves synchronally with the diurnal variation of 

 barometric pressure. Beasons were given for believing that that system 

 of diurnal wind-currents is a universal phenomenon ; and on that hy230- 

 thesis I showed how the diurnal variations of the barometer could be ex- 

 plained as a result of those currents. 



I have lately examined closely the " Discussion of the Anemometrical 

 Besults furnished by the self-recording Anemometer at Bermuda," which 

 forms Appendix II. of the ' Quarterly Weather-Eeport of the Meteoro- 

 logical Office, London,' July to September 1872. Those results support 

 the conclusions arrived at in my former paper in such a remarkable man- 

 ner as to justify the readvancement of some of them in a form which 

 will prominently exhibit their relation to the diurnal variation of the 

 barometer. 



The following Table (p. 403) exhibits the mean diurnal variations of the 

 north and east components of the wind, in miles per hour, at Bermuda, for 

 the whole year and for the summer and winter half-years. It is compiled 

 from Table II. of the Appendix to the Quarterly Weather-Eeport already 

 referred to. 



These variations are also represented graphically by figures 1 to 9 

 (p. 404), the variations of the north and east components for each of 

 these periods being exhibited separately by figures 1 to 6, and in a com- 

 bined form by figures 7 to 9. 



Comparing figure 7 with figure 9 (plate xxxiv.) of the ' Transactions ' 

 for 1873, we see that the figures are remarkably similar in form. Both 

 curves exhibit a double right-handed rotation in the twenty-four hours, 

 and all the hours of the day are respectively similarly situated on both 



* Pages 1 to 18. 



