. Machinery and processes of the industrial arts, and apparatus of the exact sciences. mingly constant,is actually extinguished and re-kindled atevery vibration. The proof of this was firstshown by Professor Tyndall, by means ofan optical arrangement extremely simple initself, though very striking in the effects itproduces. The experiment is made in a darkroom. The tube employed is blackened inevery part except on one side just oppositethe point where the gas jet is to be front of the tube at this point is placed aconcave mirror which is capable of beingturned around a vertical axis.
. Machinery and processes of the industrial arts, and apparatus of the exact sciences. mingly constant,is actually extinguished and re-kindled atevery vibration. The proof of this was firstshown by Professor Tyndall, by means ofan optical arrangement extremely simple initself, though very striking in the effects itproduces. The experiment is made in a darkroom. The tube employed is blackened inevery part except on one side just oppositethe point where the gas jet is to be front of the tube at this point is placed aconcave mirror which is capable of beingturned around a vertical axis. A screen isalso adjusted at a distance suitable to re-ceive the image of the flame produced bythe mirror. So long as the tube is silent,as it will usually be when the flame is largerthan the experiment requires, the rapido scil-lation of the mirror around its vertical axisRogerss Revolving- Jet. will preduce upon the screen the appearanceof a continuous band of light; but when, by gradually reducing theflame, the tube is made to sing, this band will be immediately broken Fig. ACOUSTICS SINGING FLAMES. 511 up, and in its place will appear a row of entirely separate and distinctimages of the flame. Professor Eogers has very beautifully varied thisexperiment by dispensing with the mirror, and employing a bent gastube, which is made to revolve rapidly within the singing tube of glassby means of a pulley and band as represented in the figure. The glasstube may be several inches in diameter; but the experiment succeedsperfectly with one of two inches. When the jet is put into rotationwhile the tube is silent, the flame forms a continuous circle; but themoment the tube begins to sing, the circle breaks up into a crown ofminute flames, resembling a string of pearls. Mr. Kcenig presents a pretty variation of this experiment. In everytube there are one or more points where the presence of the flame excitesthe note with greater facility than elsewhere. There are other pointswhere t
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