348 RECORD OF SCIENCE FOR 1886. 



however, is observable eveu at 50 kilometers distance. Although its 

 energy is superior to that of the greater uumber of musical sounds per- 

 ceivable by the ear, yet absolutely nothing is heard. Substituting a 

 recording tambour for the ear, with a chronoraetric fork for comparison, 

 the air-pressure curves for multiple lengths of the tube were obtained, 

 and from these exact measurements were made. The time required for 

 the wave front to pass once, twice, thrice through twice the length of 

 the tube was measured on the Kegnault chronograph with the lever- 

 tambour and with an extremely sensitive membrane having an electric 

 contact. The first j)assage through the tube required 37.259 seconds 

 by the tambour and 37.251 by the membrane ; the second required 

 37.337 and 37.334, respectively, and the third 37.383 and 37.384 seconds. 

 Hence it would seem that the velocity of propagation diminishes with 

 the intensity. (C. R., January, 1886, cii, 103.) 



^N'eyreueuf has continued his researches upon the velocity of sound 

 in gases and has extended his experiments to vapors. The apparatus 

 used was a modified form of that described in the last report, con- 

 sisting of a reed and draw tube. The mean of twenty-four accordant 

 determinations in the case of steam gave a wave-length of 40.63'="' with 

 a mean error of 0.18, the value obtained for air in the same apparatus 

 and at the same temperature, 100°, being 28.5'="'. In the experiments 

 with alcohol and ether, three reeds were used, the wave-length ratios 

 in air and alcohol being forthe three 1.239, 1.219, and 1.217, respectively, 

 while the wave-length in air is to that in ether as 1.71 and 1.706 to 1, 

 respectively. Assuming as the ratio of the specific heat of air at con- 

 stant pressure to that at constant volume the value 1.41, the author 

 calculates this ratio for steam and for the vapors of alcohol and of 

 ether and obtains the values 1.321 for the vapor of water, 1.14 for that 

 of alcohol, and 1.093 for ether vapor. Ann. Chim. Phys., December, 1886, 

 VI, IX, 535-553.) 



Tomlinson has pointed out the fact that Wertheitn's statement that 

 the velocity of sound in iron and steel is increased by a rise of temper- 

 ature not exceeding 100°, is erroneous. While it is true that the lon- 

 gitudinal elasticity of iron, as determined by the static method, will be 

 found greater at 100° than at 0°, provided we begin with the lower 

 temi)erature first and the wire has uot, after the original annealing, been 

 previously raised to 100° ; yet thisapparenttemporary increase of elas- 

 ticity is a really permanent one; and if the wire be repeatedly heated 

 to 100° and afterwards cooled, subsequent tests will always show a less 

 elasticity at the higher temperature than the lower, if suflicient rest 

 after cooling be allowed. When however we come to such molecular 

 displacements as are involved in the passage of sound through a wire, 

 even the apparent increase of elasticity above mentioned vanishes. 

 He had been able to prove that when an iron or a steel wire is thrown 

 into longitudinal vibrations, so as to produce a musical note, the pitch 

 of this note becomes lower as the temperature is raised, even when the 



