528 History of Luminescence 



the water, like that of the sea. He wrote (pp. 446-447) " I drew 

 the end of a stick through the water, from one side of the pan to 

 the other, and the water appeared luminous behind the stick all 

 the way, but gave light only when it was disturbed. When all the 

 water was stirred, the whole became luminous and appeared like 

 milk; . . ." We now know that this development of luminescence 

 on stirring is merely the admission of more air to the milky sus- 

 pension of luminous bacteria, which have used up all the oxygen 

 in the sea water, but to Canton the milkiness and the agitation 

 necessary for limrinescence exactly resembled the description of 

 Father Bourzes, which Canton quoted. Canton also quoted Sir 

 John Pringle -^ (1750) to the effect that salt hastens putrefaction 

 of tissues. His evidence for the putrefactive origin of sea light did 

 appear convincing. 



Martin (1761) had previously emphasized that salt was essential 

 for the development of the light of dead fishes, but his argument 

 connecting luminescence of the sea was less convincing. While lumi- 

 nous bacteria may make salt water luminesce, they normally never 

 grow in such numbers as to be responsible for the light of the sea. 



COMBINATION OF CAUSES 



There were a number of observers unwilling to attribute the light 

 of the sea to any one cause. Usually the larger flashes of light were 

 known to be of animal origin, and the more diffuse luminescence 

 was considered due to other causes. L. Spallanzani (1784), who 

 investigated so many natural things, gave an opinion on sea light 

 during a 2|^-months stay at Portovenere, near Genoa, in 1783. He 

 observed several small luminous animals in the sea water, including 

 the worms of Vianelli (1749) and Griselini (1750) but not the 

 ostracods of Godeheu de Riville (1754) . He was inclined to believe 

 that the more diffuse light arose from disintegrating parts of ani- 

 mals but did not go as far as Canton in thinking that it came from 

 decaying fish. He saw very few fish luminesce and they were not 

 necessarily the most oily ones. Moreover, sea light did not always 

 appear at the surface, where oil would be found, but often came 

 from considerable depths. Therefore, Spallanzani believed the sea 

 had a characteristic light of its own, in addition to that from obvious 

 living and luminous animals. 



Reinhold Forster -'' (1778) , whose poetical description has already 

 been quoted is a good example of an observer who believed that 



"Pringle, Phil. Trans. 46:480-488, 525-534, 550-558, 1750. 



^^ R. Forster, Observations made during a voyage around the world, 61-68, London, 



1778. 



