Ill 
for ascertaining the velocity of sound. 
that for each degree of the thermometer 1 ,2 feet may be al- 
lowed in the velocity of sound for a second ; for each degree 
of the hygrometer 1 ,4 ; and for one-tenth of an inch of the 
barometer* 9,2 feet. Then taking these numbers as the basis 
of the comparison, we find the mean difference of the velocity 
between a calm, and in a moderate breeze of wind, to be 
nearly 10 feet in a second. And by comparing other results 
together, a difference of about 21J feet in a second, or 1275 
in a minute is found between, the wind being in the direction 
of the motion of sound, or opposed to it. 
Before I conclude these introductory observations, and ex- 
planations of the experiments, it may be proper to refer 
more particularly to Table XI., containing the mean motion 
of sound for each month of the year, by the experiments 
with the Mount gun, according to the state of the atmo- 
sphere indicated by the different instruments ; and to the 
prevailing monsoons, which may be considered to be the 
same, during the same months, every year ; full information 
respecting which is given in the former Tables. On examin- 
ing this Table, it is rather curious to observe how regularly 
the mean velocity proceeds to a maximum about the middle 
of the year, and afterwards retraces its steps ; giving us a 
velocity in one case 1164 feet in a second, and in the other 
of only 1099 feet. This regularity would, no doubt, be still 
greater with the mean of the observations of several years. 
* The rise and fall of the barometer is very limited in this country, as will be 
seen by an examination of the Tables. A sudden fall of 0,3 inch indicates a gale 
of wind. 
J. Goldingham. 
Madras, -$\st May, 1822. 
