180 



Mr. Galbraith on the Velocity of Sound, 



Now this is very nearly true in the usual state of the atmo- 

 sphere, but in extreme cases of dryness and moisture it must 

 vary a little from this, so that I have not been able to discover 

 the exact quantity of variation. From such comparisons as 

 I have been able to make, it seems, however, in its present 

 state, to be pretty accurate. As I have already, in the volume 

 referred to, shown its agreement with Professor Moll's ex- 

 periments, I shall now compare it with those made by Captains 

 Parry and Foster at Port Bowen ; and as they had no anemo- 

 meter to determine the velocity of the wind, I shall make a 

 probable estimation of its effects, from Smeaton's table in the 

 51st volume of the Philosophical Transactions, as nearly as 

 I can, from the account of the weather given along with the 

 observations, and the angle between the direction of the wind 

 and sound estimated to the nearest point, that being the de- 

 gree of accuracy attainable only from the data, page 86, Ap- 

 pendix to the Third Voyage. 



Experiments made at Port Bowen, in Latitude 73° 14' N. 

 The extent of the measured Base was 12892*89 feet, and the 

 bearings of the Gun S. 71° 48' E. 



1824. 



Bar 

 in 



Inches 



Temp. 



Wind. 



Weather. 



Interval in Seconds be- 

 tween Flash and Report. 



Exp. 

 Velocity 

 per sec. 



Nov.24 

 Dec. 8 

 1825. 

 Jan. 10 

 Feb. 7 

 17 

 21 



Mar. 2 



22 

 June 3 

 4 



29-841 

 29-561 



30-268 

 29-647 

 29-598 

 29*735 



30-398 



30-258 

 30-118 

 30-102 



- 7 C 



- 9 



-37 

 -24-5 

 -18 

 -37-5 



-38-5 



-21-5 

 +33 -5 

 +35 



E.S.E. 

 N.N.E. 



K.S.E. 

 N.E. 



calm 

 calm 



easterly 



wester 1 y 

 easterly 



light 

 squally 



light 

 light 



light 



light 



light 

 strong, 

 squally 



overcast 

 very clear 



clear 



very clear 



overcast 



overcast 



f a little 1 



\ overcast J 



f very clear I 



\ and fine J 



very clear 



> clear 



P. 



12 s - 3525 

 12 -3310 



12 -5889 

 12 -6390 

 12 -3720 

 12 -8167 



12 -6400 



12 .4000 

 11 -7333 

 11 -5889 



F. 



12* -4300 

 12 -5266 



12 -4700 

 12 -6167 

 12 -4400 

 12 -7067 



12 -7800 



12 -7167 

 11 -7440 

 11 -4733 



Mean, 

 12 s -3912 

 12 -4288 



12 -5290 

 12 -6278 

 12 -4060 

 12 -7617 



12 -71C0 



12 -5583 

 11 -7387 

 11 -5311 



1040-49 

 1037-34 



1029-04 

 1020-99 

 1039-25 

 1010-28 



1014-39 



1026-64 

 1098-32 

 1118-10 



Now, by applying the above formula, in which t is the tem- 

 perature by Fahrenheit's thermometer, f the elastic force of 

 aqueous vapour, p the barometric pressure, A the latitude, 

 w the velocity of the wind, and <p the angle between the wind 

 and sound. Above 0° Fahr. I have taken f according to the 

 temperature marked, which cannot cause any great error. 



1824. 



