120 Dr. Grecory on the 
Feet per Second, 
Thus, Mr. Roberts assigns a velocity of......-..-. Pee 1300 
Mir: Bowle mere es alas is ne oe he ee cg 1200 
Mr. Walker, and Duhamel .............-....-. 1338 
Mersenne, in his Treatise de Sonorum Natura, 
(@ausiset Piechibusse- eee eee eee ee 1474 
The Florence Academy .........-.-+-++-e +00: 1148 
Cassini de Thury (Mem. Paris Acad. ann. 1738) 1107 
i.) F073 eR aes io DenGuuepyaoice 6 © Herricks meareuomme HU 27 
Derham. <8 6 hee oe Ie ae A 
HWY Te UV) Sateen ene fr welts ip ou olgtekaiaeee oie 1109 
| ETE 2) Ae RRR ORS Say ice Onan oder De eet eee 1130 
Arago, &c. from experiments in June 1822, give 
337.2 metres, at the temperature of + 10° 
Cente TAde ne eon crea eas eee 1106.32* 
The theoretical formula most generally adopted, especially by 
Continental philosophers, is this :— 
Velocity in horizontal direction = 333.44 met. ,/1+.00375¢; 
the metre being = 3.2809 English feet, and ¢ denoting the mdication 
of the temperature upon the centigrade thermometer. 
T am inclined, however, to think that this can only be regarded 
as an approximative formula; and that we are not yet in a state 
to receive otherwise, than as an approximation, any theorem which 
simply includes the variations of temperature. The air is subject 
to various classes of changes, indicated by the barometer, ther- 
mometer, hygrometer, and anemometer respectively, as well as 
others probably, for the ascertaining of which we have not yet 
any appropriate instrument. If we could select these, one by 
one, ad libitum, and carry experiments first through a moderate 
* This is the last result of which I had heard, previously to the commencement of my 
own experiments. 
OO a Te 
