﻿420 K. H. Shellbach on Acoustic Repulsion and Attraction . 



sounded, into two almost straight currents which diverged from 

 one another at an angle of about 30°, and which lay in a ver- 

 tical plane perpendicular to the plane of the box's mouth. When 

 the velocity is greater, the influence of the sonorous vibrations 

 is still very perceptible, but the gas-stream does not appear so 

 perfectly divided ; but when the sal-ammoniac rises very slowly, 

 there is produced either only a very weak repulsion, or else the 

 effect of the sonorous pulsations is not to be distinctly de- 

 tected at all. If hydrogen, coal-gas, or carbonic acid instead of 

 atmospheric air, be led into the ammonia, the appearance is not 

 essentially modified. 



If the sal-ammoniac be made to pass through a heated glass 

 bulb before it rises, no effect of the heating is seen at first. If 

 the bulb be heated too strongly, the air-current becomes invi- 

 sible on account of the sublimation of the sal-ammoniac. 



In order to be able to examine the effect of heat, I led a cur- 

 rent of atmospheric air over fuming nitric acid and allowed the 

 gas to issue from a tube, upon the horizontal limb of which a 

 bulb had been blown. The rising stream of nitrous acid, like 

 that of sal-ammoniac, was also split into two parts, which were, 

 however, not so distinctly separated as in the latter case. On 

 heating the glass bulb, the effect of the sound- vibrations was no 

 longer distinctly exhibited. All these phenomena could be re- 

 cognized in the immediate neighbourhood of the sounding-box, 

 and also when the gas-stream rose at a distance of one or two 

 decimetres, or even further from it. 



Besides the above-mentioned fork I also made use of a second 

 one, which gave 1024 single vibrations per second, and could be 

 screwed on to a resonance-box. A glass tube, 64 centims. long 

 (that is, about as long as a sonorous wave produced by the fork), 

 was fastened horizontally. If now the tuning-fork was set in 

 vibration at one end of the tube, a light glass bulb (Glaskugel) 

 or a disk was strongly attracted at the other end, and a candle- 

 flame as distinctly repelled. . 



All these experiments, however, succeeded much better when 

 the larger fork was used, which made 512 vibrations per second. 



These and the previously mentioned phenomena were also 

 produced, although to a less degree, when the tuning-fork was 

 set in vibration by means of a second fork in unison with it. 

 The actions were still visible when the distance between the 

 forks was 1 metre. 



The disks and light spheres with which the experiments were 

 performed were fastened to the end of a brass needle about 2 

 decimetres in length, provided in the middle with an agate cap, 

 and moveable like a magnetic needle around a vertical axis. If 

 the needle be too long and the disks very light, the apparatus 



