351 



To rendei" the effect visible at a distance, it is of course neces- 

 sary to use a large tube and flame. It is, however, beautifully 

 distinct when the tube is some six feet long, by one and a half 

 inches in diameter, and the flame three quarters of an inch in 

 height. The mechanism employed to give rotation to the jet 

 consists of a grooved wheel connected by a band with a small 

 pulley. Into the latter the supply pipe enters from below by a 

 smooth gas-tight joint, which allows the pulley freely to revolve. 

 The jet pipe secured to the middle of the upper face of the pul- 

 ley tapers to the extremity, and rising to the height of six or 

 eight inches, is elbowed near the top so as to give the flame when 

 revolving an orbit of nearly an inch in diameter. 



When the experiment is in progress, the appearance of the 

 horizontal portion of the jet pipe affords incidentally a very 

 pretty proof of the intermittence of the singing flame. As each 

 successive explosion makes this part strongly visible, it assumes 

 the aspect of a number of hrilliant spokes corresponding to the 

 subdivisions of the crown of flame ; and if to vary this effect we 

 blacken the horizontal part of the pipe, and fasten near its outer 

 end, or where it resumes a vertical dii'cction, a brilliant bead of 

 glass or metal, we are presented with a circle of starry/ points, 

 each of which, by a proper adjustment of the motion, appears to 

 be at rest. 



(5.) The following proof of the intermitting nature of the 

 singing flame, suggested by the effects just described, is at once 

 so simple, and so readily seen at a distance, as perhaps to merit 

 a place among useful lecture-room illustrations. In this experi- 

 ment the jet-pipe bearing the flame is held at rest in the tube, 

 and the required effect is produced by receiving the light on a 

 circular disc of thick pasteboard or of metal, some six inches in 

 diameter, supported near the tube on a horizontal axis around 

 which it may be revolved by the impulse of the hand. The face 

 of the disc next the tube, colored of a dead black with paint or 

 a covering of cloth, should have a narrow strip of white paper 

 fastened upon it in a radial direction, or a small circular bit of 

 the same placed near the edge. If both faces are used alter- 

 nately, we may affix the white bar to one and the dot to the other. 



On bringing the six feet tube down over the flame, and giving 

 rapid motion to the disc, we remark that so long as the flame 



