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FOOTNOTES:
[1] A Lecture delivered at the Academy of Music, Philadelphia, under the auspices of the Franklin Institute, September 29, 1884.
[2] Alluding to a moving diagram of wave motion of sound produced by a working slide for lantern projection.
[3] Showing two moving diagrams, simultaneously, on the screen, depicting a wave motion of light, the other a sound vibration.
[4] Exhibiting a large drawing, or chart, representing a red and a violet wave of light.
[5] Since my lecture I have heard from Prof. Langley that he has measured the refrangibility by a rock salt prism, and inferred the wave length of heat rays from a "Leslie cube" (a metal vessel of hot water radiating from a blackened side). The greatest wave length he has thus found is one one-thousandth of a centimeter, which is seventeen times that of sodium light. The corresponding period is about thirty million million to the second.—W.T.
[6] Exhibiting a large bowl of clear jelly with a small red wooden ball embedded in the surface near the center.