Radium, and other radio-active substances : polonium, actinium, and thorium. With a consideration of phosphorescent and fluorescent substances, the properties and applications of selenium, and the treatment of disease by the ultra-violet light / by William J. Hammer.

  • Hammer, William Joseph, 1858-1934.
Date:
1903
Catalogue details

Licence: In copyright

Credit: Radium, and other radio-active substances : polonium, actinium, and thorium. With a consideration of phosphorescent and fluorescent substances, the properties and applications of selenium, and the treatment of disease by the ultra-violet light / by William J. Hammer. Source: Wellcome Collection.

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    In Fig. 1, is shown an illustration of the “Pyrophorus Noc- tilucus.” This tropical beetle has been most carefully studied by Prof. S. P. Langley and F. W. Very, and the efficiency of the light given off tested by the Langley bolometer; and they have demonstrated that practically all the energy which its phosphor- escence represents, appears as light; and the light given off by this insect is the most efficient light known, it being produced at about one four-hundredth part of the cost of the energy which is expended in the candle flame*. Sir Oliver Lodge says if the secret of the firefly were known, a boy turning a crank could furnish sufficient energy to light an entire electric circuit. And Prof. Langley says, “There seems to be no reason why we are forbidden to hope that we may yet discover a method (since such a one certainly exists and is in use on the small scale) Fig. 1.—“ Pyrophorus Noctilucus” (life size), the Producer of the Cheapest Form of Light Known. of obtaining an enormously greater result than we now do from our present means of producing light.” Langley believes the light of these insects is due to chemical action, as it is decreased by nitrogen which checks combustion, and is increased by oxygen which increases combustion, and furthermore, the product is apparently carbon dioxide. We also may produce phosphorescence by rubbing crystals together, or by friction of other bodies, or by cleavage, such as fracture of lump sugar in the dark. Among plants, phosphorescence was first recorded by A. Lin- naeus, whose daughter discovered it in the nasturtium. Phosphor- * “On the Cheapest Form of Light,” by S. P. Langley and F. W. Very, No. 1258 Smithsonian Misc. Coll.