Experiments and observations on the light which is spontaneously emitted, with some degree of permanency, from various bodies. / By Nathaniel Hulme, M.D. F.R.S. and A.S. From the Philosophical Transactions.

  • Hulme, Nathaniel, 1732-1807.
Date:
1800
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Licence: Public Domain Mark

Credit: Experiments and observations on the light which is spontaneously emitted, with some degree of permanency, from various bodies. / By Nathaniel Hulme, M.D. F.R.S. and A.S. From the Philosophical Transactions. Source: Wellcome Collection.

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    one of five drams. In a solution of two drams, in the same quantity of water, the liquid was luminous; but much more so when only one dram of salt was used. Observing the ex¬ tinction of light to take place, as above, in the more saturated solutions, while the diluted solutions were luminous, it occurred to me to endeavour to discover what became of the extinguished light, in the former case, and whether it might not be revived by dilution. For this purpose, I took the solution of seven drams of salt in one ounce of water, in which the lucid matter from a mackerel had been extinguished, and diluted it with six ✓ ounces of cold pump water ; when, to my great astonishment, light in a moment burst out of darkness, and the whole liquid became beautifully luminous ! This revived light remained above 48 hours, that is, as long as other light in general does, which has never been extinguished. Hence, it had lost nothing of its vivid luminous powers by its extinction. Exper. 2. The last experiment was then reversed. A solu¬ tion of one dram of Epsom salt in one ounce of water, was brilliantly illuminated with mackerel light. Then, six drams of the salt were put into this luminous liquid; and, after shaking the phial very well for a little time, to promote the solution of the salt, the light was totally extinguished. But the same light was again recovered, by the addition of six ounces of water. In this manner, the light may be frequently extinguished, and as often revived. In one instance, the same light, by a repe¬ tition of this method, was made to undergo ten extinctions. Exper. 3. A good quantity of herring-light, being mixed with a solution of four drams of common salt in two ounces of water, was immediately extinguished. Then, fourteen ounces of cold pump water were added thereto, and the whole liquid