134 Natural History of the Ocean, fyc. 



1. Absorbed solar light. Wilson of Edinburgh made 

 many experiments to ascertain if this was true. He found 

 that water retained this property when it had been covered 

 with oil, or when drawn from a great depth. Surface water 

 exposed to the sun's rays retained it. The electronometer 

 did not aiFect it. 



Many substances on land absorb light, and travellers irj 

 warm climates are often benefitted by the emission of it. 



Gregg mentions a man who could read in the dark — and 

 another who couid do the same after drinking wine. 



2. Marine animals. Dr. Forster, Oct. 29. 1772, off the 

 Cape of Good Hope, near the shore in a storm, observed 

 every wave to present a luminous crest; and that there 

 was a phosphoric line on the sides of the ship where the 

 waves broke He also saw large luminous bodies moving 

 in the water, and found that they were fishes ; and that 

 when near each other, the small ones swam from the larger. 

 On examining a bucket of water, the luminous particles sub- 

 sided ; but the same property was manifested on agitation. 

 Those particles were animals, globular, gelatinous, brown- 

 ish, and transparent. On the coast of Malabar they are very 

 brilliant. There are several species of animals engaged in 

 this phenomenon : but chiefly two — the Medusa and Acti- 

 nia. The former are microscopic, and abundant in warm 

 climates — the latter occasionally exhibit a remarkably strong 

 phosphorescence. Sir Jos. Banks mentions a Crustacea 

 wiiich emitted light equal in quantity and lustre to that of 

 the glow worm. 



3. Electric luminousness is seen in the wake of ships, 

 like stars and globules : sometimes extending over a great 

 part of the ocean. In the Indian seas, it forebodes a change 

 of weather. 



4. Decayed animal and vegetable substances frequently 

 become phosphorescent; and produce on agitation, the 

 most brilliant light. It is useless to specify, where so ma- 

 ny possess this property.* 



* Since finishing: this paper, I have seen in the Edinburg;h Philos. Journal 

 a notice of a paper on the " Luminosity on the sea," by Dr. MacCulloch, 

 published in the Quarterly Journal of Science and Arts: — and of another 

 paper on the same subject by Dr. Murray, in the 3<\ Vol of the Trans, of 

 the Wernerian Society ; which I believe have not yet reached this coun- 

 try — at least I have not had an opportunity of seeing them. 



