PHILOSOPHICAL TRANSACTIONS. 
I. The Diurnal Variations of the Wind and Barometric Pressure at Bombay. By 
F. Chambers. Communicated by Charles Chambers, F.B.S., Director of the 
Colaba Observatory , Bombay. 
Received May 27, — Read June 19, 1873. 
1. The object of this paper is to draw attention to a remarkable relation which has been 
found to exist between the diurnal variation of the wind and the double diurnal oscil- 
lation of the barometer at Bombay, and which, it is believed, will be of great interest to 
all meteorologists. 
2. The observations made use of in the discussion are the hourly tabulations from the 
record of a Robinson’s Anemograph from June 1867 to May 1870, the hourly observa- 
tions of the barometer and temperature of the air for the same period, and the corre- 
sponding pressure of vapour (calculated from the readings of the dry- and wet-bulb 
thermometers), and also some particular results of later date which will be introduced 
in the course of the inquiry. A full description of the various instruments and the 
methods of observation and reduction is given in the introduction to the “ Bombay Mag- 
netical and Meteorological Observations, 1865-70 but it may be well briefly to recapi- 
tulate here the method of reducing the anemograph indications, as it is entirely owing 
to its mathematical exactness that the results now brought forward have been obtained, 
and it is therefore deserving of special attention. 
The wind of every hourly interval is resolved into a north or south wind and an east 
or west wind of such velocities, that, if they blew together, the resulting movement and 
direction would be the same as is actually observed. The formulae by which these reso- 
lutions are effected are : — 
Velocity of wind from north or south =m cos («X 22^ degrees) (1) 
Velocity of wind from east or west =m sin («x2 2^ degrees) (2) 
Where m is the movement observed and n the number of the direction-space under 
which the wind of the hourly interval is classed, the circle being divided into sixteen 
spaces, which are numbered consecutively from 0 to 15, and correspond respectively to 
the directions N., N.N.E., N.E., &c. ; hence the quantity calculated from (1) will repre- 
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