PHYSICS. 247 



the difl'ereut forks were tested by means of Schei bier's tonometer, tlie 

 beats with the standard fork being carefully counted. Great variations 

 were observed, the lowest pitch for A being 374 vibrations at L'llospice 

 Comtesse, Lille, and the highest 5G7 vibrations, the usual cliurch 

 pitch in Xorth Germany in 1019, called chamber pitch by Pra^torious. — 

 {Nature, xxi, 550, 1880.) 



Kayser, under Helmholtz's direction, has made a series of experiments 

 to test the question whether the intensity of a sound has any inilueuce 

 upon its velocity of propagation. He used a tube giving a continuous 

 note, each vibrating section of which passes through the same i)hase 

 after each semi-vibration. Hence two sections passing a determinate 

 phase at the same instant are distant from each other by a multi])le of 

 half a wave length. To render visible the vibration of a gaseous section 

 of the tube, a small tongue was cut in a very thin plate of mica, which 

 was cemented by one of its extremities to a copper ring sliding within 

 the tube. This mica plate reproduced the phases of air vibration at the 

 point where it was placed. A sliding wire controlled the length of the 

 tongue so as to bring it into unisoij with the sound of the tube. View- 

 ing a luminous point on the tongue through a vibration microscope, a 

 Lissajous figure is formed by a combination of the two rectangular 

 vibrations. Very minute changes of phase in the tongue produce marked 

 changes in the figure. By displacing the mica along the tube until a 

 given figure is reproduced, the distance moved is obviously half a wave 

 length. If the mica tongue be fixed at the open extremity of the tube, 

 and a movable piston be made to close the other one, the same figure is 

 observed on the lamina whenever the i)iston is displaced by half a wave 

 length. A constant sound was obtained in the tube by means of an 

 electrically vibrated fork in front of a resonator. By varying the 

 amplitude of oscillation, the intensity of the sound could be varied. 

 On comparison with a divided scale, the amplitude of the mica vibra- 

 tions was found to be i^roportional to the oscillations of the air column. 

 As a result, the author does not find any difference in the velocity of a 

 sound when its intensity is made to vary. Eegnault's results, being ob- 

 tained with waves of explosion very different in their character, do not 

 hold good for musical sounds. — {Ann. Pliys. Chem., II, vi, 405, 1870.) 



Jacques has experimented to ascertain the velocity of propagation of 

 very loud sounds produced by the firing of a six-pound brass field-piece 

 at the Watertown Arsenal, Massachusetts. A series of membranes was 

 erected at distances varying from 10 to 110 feet from the mouth of the 

 cannon, and in the rear of it. Each membrane consisted of a hoop 9 

 inches in diameter, over which a sheet of thin rubber was stretched. At 

 the center, on the side toward the cannon, a small brass shelf was 

 fastened, on which rested one end of a delicate steel spring, the other 

 end being held by a separate support. These metallic parts formed 

 portions of a continuous metallic circuit, including all the screens, and 

 terminating in the primary coil of an inductorium. The Schultz chrono- 



