Intelligence and Miscellaneous Articles. 11 



Fownes's experiments, made more than half a century later, are not 

 for one moment to be compared as to accuracy with the earlier 

 experiments of Gilpin." Dr. Stevenson's tables give the sp. gr. to 

 four decimal places at 60° F. (water at 60° F. = 1), the percentage 

 of alcohol by weight and by volume, and the percentage of proof 

 spirit. The little book must in future be at the right hand of all 

 analysts who have to do with spirit determinations. 



XI. Intelligence and Miscellaneous Articles. 



ON THE VELOCITY OF THE PROPAGATION OF SOUND. 

 BY IOC. J. YIOLLE AND TH. YAUTIER. 



TX a previous communication the authors described the methods 

 -*- by which they were enabled to follow for several minutes the 

 propagation of a wave in the interior of a cylindrical pipe 07 m. in 

 diameter. The following are the principal results of this research. 



The experiments with the pistol are summed up in the following 

 table, which gives for different charges the time taken by the front 

 of the wave to travel once, twice, . . . a times the path 2L. 



Cha <*es of Duration of the course 2L. 



the pistol. *~Z — + 7 7 s 



z x . r 2 . r 3 . r 4 . 



£TT. S 3 S S 



3 37-257 37-334 37-384 37*420 



2 -262 -343 -392 



1 -279 -350 -408 



It follows undoubtedly from these numbers that the velocity of 

 the propagation of the wave diminishes with the intensity. 

 \Ye shall put therefore 



*=A-Bv%-; 



A and B being two constants to be determined, and p^- the mean 

 pressure during the Jth course, which pressure is given by our 

 manometric measurements. 



Taking A = 37 s, 460 and B = # 69, the pressures being measured 

 in millimetres of water, we have : — 



Charges of Duration calculated . 



the pistol. "T + + "7^ 



*r r 2- S- z v 



3 37-244 37-335 37-388 37*418 



2 -262 -346 -344 



1 -280 -356 -400 



A representing the duration of the course 2L for an infinitely 



2L . 



small condensation, — r- is the velocity of propagation of an infi- 

 nitely small wave under the conditions of the experiment. 



From this we easily deduce the limiting velocity to zero, and in 

 dry air in the intei or of the pipe in question, and therefore 



