Velocity of Sound. 411 



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. 



Feet. 



Velocity of sound, Fahr. therm. 27° lOQ^ 



ditto 33 1099£ 



ditto 35 1102 



ditto 45 1107* 



ditto 59 1109| 



ditto 60 1112 



dilto 6 * {me 1 



ditto 66 |}}}!j 



Of these results, some have been obtained in the day-time, 

 others in the night ; some when the sound has been trans- 

 mitted 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 cannons, 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 exten- 

 sive to justify me in deducing from them even an approxima- 

 tive 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 all the preceding results, is 

 simple enough to be easily recollected by practical men ; and 

 may, perhaps, be employed in our own climate. It is this : 



At the temperature of freezing 33°, the velocity of sound is 

 1100 feet per second. 



For lower temperatures deduct 1 half & foot 

 Jbor higher temperatures add. J 

 From the 11001 for e d e of difference f rom 33 o 

 to the 1100 J J ° 



on Fahr. therm. ; the result will show the velocity of sound, 

 very nearly, at all such temperatures. 



Thus, at the temperature of 50°, the velocity of sound is, 



1100 x £(50—33) = 1108£ feet. 

 At temperature 60°, it is 1100 + £(60— 33)= .11 1S£ feet; 

 agreeing with the experimental result quite within the limits 



of a practical rule. : 



The theorem 333-44. met. */ 1 +00375 1, before cited, gives 

 nearly 1091 feet for the velocity at the freezing point .; and 

 1111 feet for the temperature 10° centigrade, or 5Q° Fahren- 

 heit: thus occasioning a greater augmentation to the velocity 



3 F 2 in 



