305 
A SimepLtéE MetuHop or HARMONIZING LEYDEN JAR 
DISCHARGES. 
ArtTuur L. Foutny, Head of the Department of Physics, Indiana University. 
Publication No. 41. 
In the photography of sound waves! one of the chief difficulties is to secure 
the proper time interval between the sound producing spark and the illum- 
inating spark which pictures the wave. A spark gap is always apparently 
more or less erratic. When one places two gaps in series, Figure 1, and en- 
SOUND WAVE 
— 
LIGHT SPARK 
ee 
Le 
i © capacity 
4 
we *—— ELECTRIC MACHINE TERMINALS 
THEDRETICAL CROSS-SECTION OF SOUND WAVE, EXPLAINING FORMATION OF WAVE SHADOW GH THE PHOTOGRAPH! 
HEMISPHERICAL ENDS OF WAVE PRODUCE BUT LITTLE EFFECT ON LIGHT PASSING TO PLATE CUTER CYLINDRICA 
PORTION REFRACTS R&YS TOWARD THE CENTER. THUS GIVING AN OUTER DARK RING-D.R..4NO AN INNE® LIGHT BING 
L.R., WHERE REFRACTED AND NON-DEVIATED RAYS ARE SUPERPOSED. 
deavors to adjust the condenser C to make the spark L, occur at a definite 
time after the spark S, he finds that the time interval is far from constant. 
The interval varies, not merely because of variations in the spark gaps them- 
selves, but because of the charge remaining in the capacity C after a spark 
1A New Method of Photographing Sound Waves. Physical Review, Vol. XX XV, 
No. 5, November, 1912. 
5084—20 
