164 Chapter 11
chimney. The physician in him notes the slight effect of every pulsation of the heart on
the lungs blowing air through a glass tube. In fact, he is writing from his rooms at Cam-
bridge, where (as we have seen) Young blew smoke through various tubes, to the mysti-
fication of his classmates. He now records more detailed experiments in a meticulous table
comparing the varying pressures required to sound various harmonics from organ pipes
( figure 11.1 ).
When Young turns to “ the analogy between light and sound, ” he lists the evidence that
light is a wave, including Newton ’ s rings.^18 Young notes the difficulty and complexity of
Newton ’ s putative “ fits of transmission and reflection ” and adds that the recurrence of the
same color in Newton ’ s rings is “ very nearly similar to the production of the same sound,
by means of a uniform blast, from organ pipes which are different multiples of the same
length. ”^19 For instance, four-foot and eight-foot-long organ pipes under the same pressure
sound the note C an octave apart. Young notes that Euler had already noticed this analogy,
“ although he states the phenomena very inaccurately. ”^20 Though Young himself leaves his
exact analogy somewhat unclear, he considers the recurrence of colors in Newton ’ s rings
to be precisely comparable to the recurrence of pitches produced by organ pipes, a phe-
nomenon he finds incomprehensible to particle theory, which has nothing like a series of
overtones underlying it.^21 Young also draws attention to the “ tone, register, colour, or
timbre ” of the organ and other instruments as a neglected subject that should be studied
by natural philosophy.^22 Thus, when Young compares Newton ’ s rings to an organ, we
realize the full appropriateness of his application of timbre or sound-color to visual color,
for Newton himself had noted the importance of the recurrent pattern of the coloration in
his rings. Young “ hears ” Newton ’ s rings as resembling an organ ’ s cyclical structure of
pitches, overtones, and stops, in which the pressure of the air stream can excite recurrent
harmonic pitches as the pressure exerted on the glass can evoke the recurrent colors of the
rings. Implicitly, Young translates a temporal phenomenon (the frequencies of the organ
pipes) to a spatial one (the varying lens thicknesses producing Newton ’ s rings).
Having established this fundamental analogy between music and light, Young then turns
to a musical phenomenon that will provide a crucial insight into light. His point of depar-
ture is a troubling assertion by Robert Smith, the eminent Cambridge astronomer, in his
Harmonics, or, The Philosophy of Musical Sounds (1749), that “ the vibrations constituting
different sounds should be able to cross each other in all directions, without affecting the
same individual particles of air by their joint forces. ” On the contrary, Young notes,
“ undoubtedly they [the vibrations] cross, without disturbing each other ’ s progress; but this
can be no otherwise effected than by each particle ’ s partaking of both motions. ” As proof,
he instances “ the phenomena of beats ” as discussed by Smith. To explain them, Young
devises a kind of thought experiment, supposing “ what probably never precisely happens,
that the particles of air, in transmitting the pulses [of sound], proceed and return with
uniform motions, ” drawing their motion along the horizontal axis, their displacement along
the vertical ( figure 11.2 ).^23 Young includes a number of different cases in which, “ by