A SPECTROMETER FOR ELECTROMAGNETIC 
RADIATION.^ 
A. D. Cole 
At various times for some years the author has carried on experi- 
mental studies of electric radiation, measuring the amounts 
reflected, transmitted, absorbed, refracted and diffracted under 
diff'erent conditions.^ For these purposes the separate pieces of 
apparatus were brought into suitable relation to one another by 
temporary mountings, somewhat deficient in accuracy and in con- 
venience. Such makeshift arrangements have been common with 
most workers in this field. This is perhaps due to the influence 
of the classic pioneer work of Hertz^ in 1888. In his case such 
arrangements were necessary because the long wave-lengths he 
used required apparatus of large size, which was, therefore, heavy 
and inconvenient. So its different parts were mounted and moved 
as separate units. Righi,^ however in the early nineties showed 
how it is possible to obtain strong electrical radiation whose wave- 
length does not exceed a few centimeters, so that it then became 
possible to use apparatus of much more convenient dimensions. 
There was a three-fold reason for the design of the apparatus 
about to be described. The first was the need of a more compact 
and easily adjustable mounting for the various pieces of apparatus 
used in continuing a research on diffraction phenomena, upon 
which a preliminary report was presented at the New York meet- 
ing of the A.A.A.S. The second reason was the desire to have a 
compact arrangement by means of which advanced students could 
repeat the experiments of Hertz, Righi, Boltzmann and others. 
^ Read before A.A.A.S., Section B. and the American Physical Society, Decem- 
ber 31, 1908. 
^ A. D. Cole, Wied. Ann.., vol. 57, p. 290, ’96 — Phys. Rev., 4, p. 50 ’96- Elec. 
World, September, "96. Phys. Rev., 7, p. 225; ibid., 20, p. 268, ’05 ibid., 23, 
p. 238, ’06. 
® H. Hertz, Wied Ann., 36, p. 769, or Phil. Mag., 5, 27, p. 369. 
^ A. Righi, Rend. Lincei. 1893. p. 333. 
