ATMOSPHERIC REFRACTION AT LOW TEMPERATURES. 689 



11, Parry's Experiments oq Sound at Winter Island. 

 (Second Voyage, &c.). 



(p. 237.) Base lines were determined between two stations, and 

 the time between the flash and the report of a six-pounder was 

 taken by pocket chronometers, &c., by each observer. The gun 

 had an elevation of 10°, and Avas directed towards the observers. 

 The results are arranged according to temperatures. 



Therm. 



Mean Velocity 

 of Sound. 



o 



Feet. 



-41-3 



985-9 



-33-3 



1011-2 



-27-2 



1009-2 



-21-0 



1031-0 



- 2-0 



1039-8 



+ 33-3 



1069-9 



From these observations the velocity of sound is seen to increase 

 with an increase of temperature, at the rate of 1'126 feet for 

 1" Fahr. 



On Feb. 9th, with barometer 28 ' 96, and thermometer 25° Fahr., 

 the officer's word of command '' fire " was several times distinctly 

 heard about three-eighths of a second after the report of the gun. 



12. Experiments on the Velocity of Sound at Port Bowen. 

 (Parry's Third Voyage to discover a Northw-est Passao-e.) 



(p. 58.) Lieutenant Foster having occasion to send a man from 

 the Observatory to the opposite shore of the harbour, a measured 

 distance of 6,696 feet, or about one statute mile and two-tenths, in 

 order to fix a meridian mark, had placed a second person half way 

 between, to repeat his directions ; but he found on trial that this 

 precaution was unnecessary, as he could without difficulty keep up 

 a conversation with the man at the distant station. The ther- 

 mometer was at this time 18°, the barometer 30-14 inches, and 

 the wpnther nearly calm, and quite clear and serene. 



(Appendix, p. 86.) The following experiments were made with 

 a six-pounder brass gun placed on the beach at the head of Port 

 Bowen, and fired by signal from the Hecla, the interval elapsed 

 between the flash and report being carefully noted by the beats of 

 a pocket chronomxeter held to the ear of each observer. The 

 initials in the columns of interval are those of Capt. Parry 

 36122. X X 



