132 Dr. GreGcory on the 
Mortars were firing from the battery, and I took a station 3900 
feet south of it. I observed the intervals between the flash and the 
report in six successive rounds: they were 3".5, 3.5, 3”.48, 3.52, 
3.5, 3.5, respectively ; the mean being 3".5. 
3900 _ 7800 
3.5 
These are all the experiments in reference to the velocity of 
sound, as transmitted through the atmosphere, which I have yet 
been able to make. Their chief results may be brought into one 
view as below. 
=11142 feet, velocity of sound, therm. 64°. 
Feet 
Velocity of sound, Fahr. therm. 27° ....... 1094.2 
- ditto BS ate cere 10992 
—— ditto SOs ists 1102 
ditto AB he ste c's 11072 
—————_— ditto 50 aeeeecmemeneas 1109+ 
ditto GO. ce: 1112 
: 0 11142 
—. ditto it ae eee 11116 
: 1116 
— ditto Ca Soe Hie 
Of these results, some have been obtained in the day-time, others 
in the night; some when the sound has been transmitted over the 
surface of the earth, others when it has been transmitted over 
the surface of water; some are the result of direct sound, others 
of both direct and reflected sound; some from the report of can- 
nons, others of musquets, others from the sound of bells. 
Were these the only experiments on the subject that had ever 
been made, I should not regard them sufficiently extensive to justify 
me in deducing from them even an approximative rule. But as 
they have been made with great care, I may at least venture to 
present a rule, which, while it includes with only slight discrepancies 
