Intelligence and Miscellaneous Articles. 221 



and the temperatures read off from thermometers placed at each 

 membrane. 



The experiment was many times repeated with the membranes 

 interchanged, with different velocities and parts of the chronograph - 

 cylinder, and with other precautions, to prevent possible errors, 

 but always with the same result. It was found that immediately 

 in the rear of the cannon the velocity of sound was less than at a 

 distance, but that going further and further from the cannon the 

 velocity of sound rose to a maximum considerably above the ordinary 

 velocity, and then fell gradually to about the velocity usually received. 



In order to determine whether the first low velocities were due, 

 as was supposed, to the retarding influence of the bodily motion of 

 the air around the cannon, it was pointed at right angles to its 

 first position, when it was found that the maximum velocity came 

 nearer to the cannon. Had the cannon been turned in the direc- 

 tion of the line of membranes, the retardation would probably have 

 become an acceleration. The experiment was, however, of course 

 impracticable. That this apparent retardation was not due to the 

 difference in time of action of the membranes (due to a variation 

 of the force of the wave) is evident both from the very slight force 

 required in either case, and from the fact that the variation noticed 

 is in the wrong direction. 



The charge of powder was considerably varied ; and the heaviest 

 charges, of course, caused the greatest deviation from the ordinary 

 velocity. 



The successive series of experiments, owing to differences in the 

 charge and in the loading, gave different values of the velocity at 

 any one place; but the facts above stated always remained the 

 same. 



Accordingly each series represents the condition of things better 

 than the mean of several, and I have here given a table of three 

 of the best series. 



The first column represents the distance from the mouth of the 

 cannon, the second the values of the corresponding velocities in 

 the rear of the cannon when the charge was one and a half pounds, 

 the third when the charge was reduced to half a pound, and the 

 last when the cannon was pointed at right angles to the line of 

 membranes, 



Velocities reduced to 0° C. 



Rear of cannon. Side of cannon. 



Interval. 1£ lb. £ lb. 



10- 30 feet. 1076 feet. 



30- 50 „ 1187 „ 1032 1067 



50- 70 „ 1240 „ 1091 1162 



70- 90 „ 1267 „ 1120 1201 



90-110 „ 1262 „ 1114 1188 



The conclusions that we may draw from these experiments 

 are: — 1. That the velocity of sound is a function of its intensity. 

 2. That experiments upon the velocity of sound in which a cannon 

 is used contain an error, probably due to the bodily motion of the 



Phil. Mag. S. 5. Vol. 7. No. 42. March 1879. S 



