12 



insects, the creeping glow-worm, the flying glow-worm, the fire-fly, 

 and the great lantern-fly. 



The numerous experiments described in this paper were chiefly 

 made on marine animals, particularly herrings and mackerel, which 

 were exposed either in the air, or in water impregnated with different 

 salts, and of different temperatures, in a dark vault to which the 

 Doctor assigns the name of his laboratory, 



The results obtained in this investigation are described in nine 

 sections, the summary contents of which are as follows : 



1 . The quantity of light emitted by putrescent animal substances 

 does not arise from the greater degree of putrefaction in such sub- 

 stances, as is commonly supposed ; but, on the contrary, they begin 

 to shine some time before any apparent signs of putrefaction take 

 place, and the greater the putrescence, the less is the quantity of light 

 emitted. 



2. Light is a chemical element, or a constituent principle of some 

 bodies, and particularly of marine fishes ; and it may be separated 

 from them by a peculiar process, or be retained, and rendered per- 

 manent for some time. The experiments from whence this inference 

 is derived were made with pieces of herrings and mackerel, and with 

 living tadpoles immersed in solutions of Epsom salt, sea salt, Glauber's 

 salt, and in all which a quantity of light was manifestly imparted to 

 the saline menstruum, which the latter under various circumstances 

 retained for a considerable time. These experiments seem also to 

 evince, that light is not partially but wholly incorporated with every 

 particle of the animal substance ; that it is probably the first elemen- 

 tary principle that escapes after the death of fishes ; and that, as the 

 putrescence was by no means promoted, but rather retarded 'by this 

 emission of light, it is highly probable that no offensive putrefaction 

 ever takes place at sea after the death of such myriads of animals as 

 must needs daily perish in the vast ocean, which hence continue long 

 a wholesome food to the many kinds of fish that feed upon their 

 congeneries. 



3. Some bodies or substances have a power of extinguishing spon- 

 taneous light when it is applied to them. These are water, both 

 pure and impregnated with quick lime, carbonic acid gas, and hepatic 

 gas, fermented liquors, ardent spirits, fixed and volatile alkalies, cer- 

 tain neutral salts, vegetable infusions, pure honey, and the rust of 

 iron, calamine, minium, and manganese dissolved in water. 



4. Other bodies or substances have a power of retaining sponta- 

 neous light for some time when it is applied to them. These sub- 

 stances are most of the solutions mentioned in the second article, 

 which, when impregnated with some of the lucific matter scraped 

 from herrings and mackerel, retain the light for some days, especially 

 if assisted with some agitation of the phial containing them. The 

 appearances here exhibited are described as being both beautiful and 

 surprising, as they enable us to take light from one substance and 

 transfer it to another, so as to render the latter most brilliantly lu- 

 minous ; or in other words to impregnate a liquid with light. 



