NATURAL PHILOSOPHY. 181 



steam-engine, had been beard thii-ty miles. He went to Provi- 

 dence to hear it ; and other experiments were tried with trumpets 

 and whistles. Sound was sent with the wind, against the wind, 

 and at riglit angles with it. Strange to sa}^ it was heard farthest 

 at right angles. Prof. Plenry would have been almost afraid to 

 report this last conclusion, but that he afterwards found it had 

 been observed in 1813. These instruments were blown with a 

 definite amount of power and a definite amount of air. The 

 problem was to get most sound with least expenditure of power 

 and air. A trumpet blown by a Roper engine was finally adopted. 

 It seemed 2^i"obable now that sound was not a mere transfer of 

 vibrations. The body remains at rest, the waves pass by, but a 

 positive effect of some kind seems to be produced. Prof. Henry 

 tried further experiments as to the relative intensity and exten- 

 sion of sound. He strained a delicate test-paper over the mouth- 

 piece of a horn, which received the vibrations at the broad end, 

 and on this he scattered fine sand. It became a test of extreme 

 delicacy. A change of distance as small as a single inch fre- 

 quently indicated that vibration had wholly ceased. What be- 

 comes of the old theory of the i)ropagation of waves of motion or 

 sound if this experiment be conclusive ? Prof. Frazer asked if 

 any experiment had been tried on the comparative worth of 

 sounds of a different pitch. A steam-whistle not having been 

 heard in Holland, another was addetl, the pitch being two octaves 

 and a half apart. No Holland ear could bear the sound ! Prof. 

 Henry replied that the steam-gong was constructed in reference 

 to that. The best effect was ijroduced by differences of one-fifth 

 and one-tenth. The thickness of the metal seemed to make no 

 difference. Each whistle was only a resounding cavity. 



NEW ACOUSTICAL APPARATUS. 



M. Koenig has recently issued a catalogue of acoustic appara- 

 tus, in which are figured and described many new instruments 

 that will be highly prized by the lovers of experimental science. 



In the first place may be noticed — 



Bicss'' Telqihone. — This is an apparatus for the transmission of 

 sound by means of electricity. A light jilatinum point rests upon 

 a stretched membrane, which, when vibrating, causes the platinum 

 nipple to make and break contact with an adjacent metal band, 

 through which the intermittent current is transmitted to the dis- 

 tant station. There it passes round a bar of soft iron, which, 

 being rapidly magnetized and demagnetized, emits a continuous 

 sound. Thus, a person speaking in Edinburgh can, Avithout any 

 other effort, produce a sound in London. 



SeebecJvS Syren. — This instrument consists of nine circular 

 metal plates, jjierced with holes sj'stematically arranged. By 

 means of powerful clockwork, the disks can be turned, while 

 their velocity of rotation, which can be varied at pleasure, is 

 recorded in tlie usual manner. The current of air from a bellows 

 is distributed at will, with greater or less intensity, through twelve 

 pipes, which can be fixed in any position before the turning disk. 

 16 



