HISTORY OF CHRONOPHOTOGRAPHY. 335 



walls placed on little gas-burners. These "manometric flames" 

 vibrate in unison with the sonorous waves. Their images, dissociated 

 in a revolving mirror, appear with indented mantling - of various forms, 

 according to the sound. But this fugitive phenomenon could not be 

 fixed by photography until M. Marage, who has charge of the acoustic 

 work at the Physiological Station, rendered the flames photogenic by 

 substituting acetylene for ordinary illuminating gas. He has taken 

 the photographs by chronophotography on a ribbon of sensitized paper 

 having a translation of 2 meters per second (100 feet in 0.254 minute). 

 Fig. 40 (PI. VIII), shows the vibrations of the air for the French vow- 

 els i, u, on, t\ <>, a. At the same time as the vibrations of the vowels, 

 those of a special burner acted on by a tuning fork of 45 V. D. are 

 photographed also, so as to determine the pitch. 



Representations of motions in scale pictures conformed to separate 

 photographs. — The impressions by chronophotographs on a moving 

 film, complete as they are, are hard to utilize, on account of the diffi- 

 culty of comparing the separate photographs. In some cases this com- 

 parison can be facilitated by bringing the photographs together. But 

 it would be more satisfactory to be able to arrange them, each in its 

 place, on a single picture to scale. The writer has accomplished this 

 by means of successive projections and counter proofs on the same 

 sheet of paper. 



Let a gymnast throw a weight. (This is chronophotographed on a 

 ribbon.) Let us project the first photograph and carefully counter- 

 prove the form of the body.* 



After this first projection, let us project the second photograph upon 

 the same sheet, and then a third, taking care to preserve the registry 

 exact by fixed points which we have chosen. (That is, the horizontal 

 line and object r will have been sharply drawn on the back of the 

 drawing paper; and in making subsequent projections care is taken to 

 have that line and object fall upon precisely the same places.) We 

 shall thus have obtained a series of counter-proofs representing the 

 successive attitudes of the gymnast. Fig. 41 has been constructed in 

 this way. It affords complete information as to the extent and velocity 

 of each of the motions represented. 



In this case onl} r every third photograph has been drawn, in order 

 to avoid confusion in the picture to scale; but while reducing the nuni- 



n I suppose he means that the perverted negative is projected, or in some way that 

 the projection is perverted, and that the projection is made on a board. This pro- 

 jection must show the fixed object r (at the left of the horizontal line), which, with 

 the horizontal line, is photographed from nature in all the photographs. He attaches, 

 I suppose, to the board a sheet of carbon paper, and over it a sheet of drawing paper, 

 face down. The projection appears on the back of the latter, and he marks with an 

 agate stylus the outlines of the gymnast's body, the horizontal line, and the object r. 

 These outlines are thus drawn correctly on the face of the drawing paper. That is 

 how f understand his description. — Translator. 



