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But he soon perceived that the effect of the fluorescence was not instantaneous, and that the lapse of time might form a great source of error, and he then had recourse to indirect methods.
At the other end of the spectrum, by the interposition of suitable substances, Professor Stokes lowered the refrangibility, so as to render the non-visual rays visual, and to this change he gave the name of Fluorescence. Here, by the intervention of the platinum, the refrangibility is raised, so as to render the non-visual visual, and to this change I have given the name of Calorescence.
In the latter case the phenomenon is essentially the same as fluorescence, in which the dark rays of the solar spectrum beyond the violet are made visible. But we must now return to the other questions that have been started in relation to phosphorescence in animals. There has been much speculation as to the object of this light, and to the purposes it serves in Nature.
The automatic developing film would record any trace of fluorescence, and a red light would signal this result to the pilot's cabin. Minutes went by as the Sea Hound nosed slowly along through the gray-green gloom, its sister craft flanking it a hundred yards on either side. They were moving only a fathom or so above the bottom. "A blip at eleven o'clock!" the sonarman called out suddenly.
There are substances, however, on which the violet and ultra-violet waves exert a special decomposing power; and, by permitting the invisible spectrum to fall upon surfaces prepared with such substances, we reveal both the existence and the extent of the ultraviolet spectrum. Ultra-violet Rays: Fluorescence.
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