nt image of the carbon points, the
light of the image is decomposed, and a complete spectrum is obtained.
The invisible rays of the electric light, remoulded by the atoms of
the platinum, shine thus visibly forth; ultra-red rays being converted
into red, orange, yellow, green, blue, indigo, violet, and ultraviolet
ones. Could we, moreover, raise the original source of rays to a
sufficiently high temperature, we might not only obtain from the dark
rays of such a source a single incandescent image, but from the dark
rays of this image we might obtain a second one, from the dark rays of
the second a third, and so on--a series of complete images and spectra
being thus extracted from the invisible emission of the primitive
source. [Footnote: On investigating the calorescence produced by rays
transmitted through glasses of various colours, it was found that in
the case of certain specimens of blue glass, the platinum foil glowed
with a pink or purplish light. The effect was not subjective, and
considerations of obvious interest are suggested by it. Different
kinds of black glass differ notably as to their power of transmitting
radiant heat. When thin, some descriptions tint the sun with a
greenish hue: others make it appear a glowing red without any trace of
green. The latter are far more diathermic than the former. In fact,
carbon when perfectly dissolved and incorporated with a good white
glass, is highly transparent to the calorific rays, and by employing
it as an absorbent the phenomena of 'calorescence' may be obtained,
though in a less striking form than with the iodine. The black glass
chosen for thermometers, and intended to absorb completely the solar
heat, may entirely fail in this object, if the glass in which the
carbon is incorporated be colourless. To render the bulb of a
thermometer a perfect absorbent, the glass ought in the first instance
to be green. Soon after the discovery of fluorescence the late Dr.
William Allen Miller pointed to the lime-light as an illustration of
exalted refrangibility. Direct experiments have since entirely
confirmed the view expressed at page 210 of his work on 'Chemistry,'
published in 1855.]

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9. Deadness of the Optic Nerve to the Calorific Rays.

The layer of iodine used in the foregoing experiments intercepted the
rays of the noonday sun. No trace of light from the electric lamp was
visible in the darkest room, even when a white screen was pl