132 ANNUAL RECOKD OF SCIENCE AND INDUSTRY. 



powers of various substances to reflect and to transmit sono- 

 rous vibrations." The above measures are also made by 

 means of Konig's vibrating flames. The following w^ill con- 

 vey a general idea of the method : Two of Helmholtz's res- 

 onators, vibrating to the note given by the two bodies, are 

 placed near the bodies the relative intensities of whose sounds 

 we would estimate. To each of these resonators is attached 

 a gum tube ; these tubes lead to a forked tube of metal, at 

 the confluence of whose branches is placed one of Konig's 

 membranes with its gas jet. One of these gum tubes has a 

 piece cut out of it equal in length to a half-wave of the note 

 given by the two bodies, and this piece is replaced by an 

 equal length of telescoping tube made of one tube of glass 

 slidins: inside of another. Both bodies are sounded. The 

 vibrations proceeding from them impinge on the open mouths 

 of the resonators, and the impulses of the vibrating air in 

 these resonators are sent through the gum tubes to the mem- 

 brane. Now" by drawing out or pushing in the telescope 

 tube, vibrations in opposite directions are caused to reach 

 the membrane, and then, if the intensities of these vibrations 

 are equal, the membrane must necessarily remain at rest, and 

 the flame, viewed in the revolving mirror, will appear as a 

 band of light with a smooth unrufiied top border. The dis- 

 tances of the resonators from the sources of sound are now 

 measured, and the ratio of the squares of the distances will 

 o-ive the relative intensities of the two sounds. 



After Professor Mayer had succeeded in measuring the in- 

 tensities of the vibrations of the air at certain distances from 

 the sounding bodies, he measured the powers of various sub- 

 stances to transmit, absorb, and to reflect sonorous vibra- 

 tions. To accomplish this, he placed one of the sounding 

 bodies in the focus of a parabolic reflector, and brought the 

 two resonators at such distances from their sounding bodies 

 that the intensities of the pulses traversing their respective 

 tubes were equal. Pie then placed in front of, but not too 

 near, the mouth of the resonator, in front of the reflector, the 

 plane surface of the substance whose transmitting and re- 

 flecting powers he Avould determine. Serrations fiow ap- 

 peared in the flame, because part of the force of the pulses 

 which previously sounded the resonator are now reflected 

 from the interposed substfince. The resonator which has not 



