MR. E. J. STONE ON THE VELOCITY OF SOUND. 
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Mr. Kirby near the gun and Mr. Mann at the Observatory. The computed difference 
was 1 S T77 ; but the observed difference, with the same observers and with the same 
tapping-pieces as those used in the principal experiments, was l s, 265 : this was the 
result from twelve accordant observations. The difference 0 S, 09 has been applied to all 
the observed results. 
This correction depends more upon want of sensibility in picking up and recognizing- 
faint sounds, than upon mere habit of making contacts. When the observers were 
reversed and Mr. Kirby stationed at the Observatory and Mr. Mann near the gun, the 
observed difference appeared still too large, but in this case by 0 s- 20. It is clear that 
such personal equations are not eliminated by an interchange of observers nor by return 
signals. 
The equations of condition appear in Table II. The times given are those observed 
corrected for the motion of the air, the second and third terms of the effects of tempe- 
rature above 32°, and for personal equations. In these equations 
14808-5 feet 
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y = -y-, V= velocity of sound at 32°. 
The solution of these equations gives 
Y= 1090-6 feet per second, 
« =0-0019. 
Regnault’s value of « is 0-0020. 
The agreement between the value of a deduced from these experiments and Regnault’s 
value is so close that the difference between these values would scarcely be appreciable 
within the limits of variation of temperature in our experiments. The whole of the 
results have been given equal weights. It has not appeared necessary to attempt any 
discrimination between the results in the present paper. There appears, indeed, but 
little difference between the residuals as dependent upon the corrections for the motion 
of air. I have grouped the residuals into two classes according to the dampness of the 
air ; but there appears no difference in the velocity, as dependent upon dampness, appre- 
ciable within the limits of these experiments, either when referred to tension or humidity. 
The mean residual for each group nearly vanishes. The whole of the measurements of 
the distances involved have been made by Mr. Mann. The observations of the regular 
series from February 27 have been made by Mr. Kirby at the Cape-Town end, near the 
gun, and by Mr. Mann at the Observatory. The arrangements for the experiments, 
galvanic and otherwise, the determination of the personal equations, and the discussion 
of the results have been made by myself. 
b 
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