174 D r - Hulme's Experiments and Observations 



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 



