On the Propagation of Sound. 207 
thesense. Independent of this consideration, we might inquire, 
how much the temperature of the particles of air must be raised, 
to cause an increase in the velocity of sound, as obtained from 
theory, amounting to nearly one-fifth of the whole ? 
What we assert constitutes the real error in Newton’s calcula- 
tion is this, that he omits nearly one-third of the elastic power 
of the air, by supposing the whole to be compressed within an 
assumed limit; and that, although the velocity of sound, as esti- 
mated trom the altitude alone, is correct, yet it is evident to us, 
that to compress the whole of the atmosphere within the distance 
of 27541 feet from the earth’s surface, an additional force, 
equal to nearly one-third of the incumbent weight of the atmo- 
sphere, is necessary: therefore the velocity of sound at the sur- 
face of the globe, as deduced from Newton’s theory, must be in- 
creased in the subduplicate ratio of 3004 to 20°05 ; and we 
have before ascertained these two numbers to be 3514 and 2996: 
942°9 x 3514 
2996 
in a second, agreeing with the observations of Cassini exactly. 
By this method we have calculated the velocity of sound under 
the equator, and at the poles; and find it greater by about 53 
feet at the former than at the latter place; and this difference 
will be observed between the fervid air of a summer’s day and 
the chilling atmosphere of December’s reign; and the velocity 
of sound in the latitude of London will be about 1102 feet— 
estimating the increase and decrease to correspond with the va- 
riation of the latitude at the rate of one-sixth of a foot for every 
degree. 
An interesting paper was published by Modeste Perolette*, in 
which he has made it appear extremely probable that the action 
of the solar rays materially affects the propagation of sound, 
From his ingenious experiments I should infer that the velocity 
of sound during the day was greater by about 5 of the whole 
than in the night, or 22 feet in a second. Every philosophical 
observer must have observed the striking difference between the 
notes of a sounding body at midnight and noon ; also the very 
different tone of the globe itself between a dry surface, and when 
the ground is covered with snow, 
I am, &c. . 
‘ RicHARD WINTER. 
To Messrs. Nicholson and Tilloch. 
therefore, 
= 1105-9 feet, the true velocity of sound 
* Nicholson’s Journal, vol. xxv. p. 28. 
XLII. On 
