Shining Fish, Flesh, and Wood 481 



were most likely to luminesce, later the head, belly, and tail, but 

 only as long as the parts remained moist. 



JOHN CANTON 



The next investigator of shining fish was John Canton (1718- 

 1772) , perhaps better known as a student of electricity and as the 

 inventor of Canton's phosphorus, prepared in 1768 by heating 

 oyster shells and sulphur. Canton (1769) became interested in the 

 " Luminousness of the Sea " and endeavored to prove that this phe- 

 nomenon " arises from Putrefaction of its Animal Substances." Like 

 Martin he observed that when he put sea fish, a whiting or a her- 

 ring, in sea water, the next night the fish was luminous and the 

 luminosity spread throughout the sea water when the material was 

 stirred, in this respect, resembling the light of the sea, which appears 

 on agitation. However, in the case of the fish, the stirring is merely 

 due to solution of more oxygen from the air, an absolute necessity 

 for bacterial luminescence, whereas the agitation of sea water pro- 

 duces light by stimulation of luminous organisms. The resemblance 

 is purely superficial. 



Canton found that no such luminescence developed when the 

 whiting was placed in fresh water overnight, and that fresh-water 

 fish -^ did not become luminous in salt water, with the exception of 

 one carp. He made artificial sea ^vater by adding salt to fresh water 

 and found that herring became linninous in the artificial medium, 

 thus confirming the experiments of Martin (1761) . 



Canton was especially interested in temperature effects on his 

 phosphor, and was apparently the first person to report on the re- 

 versible extinction of the light of luminous bacteria by rise in tem- 

 perature. He observed 



that though the greatest summer heat is well known to promote putre- 

 faction, yet twenty degrees more than that of the human blood seems 

 to hinder it. For putting a small piece of luminous fish into a thin glass 

 ball, I found that water of the heat of 118 degrees would destroy its lumi- 

 nousness in less than half a minute; which, on taking it out of the water, 

 it would begin to recover its light in about ten seconds; but was nevei 

 so bright as before. -^ 



The effect of low temperature on the fish was not tested. 



''^ In 1784 Delius described luminous material on a piece of Rhine salmon which 

 could be rubbed off with the finger, but he had no idea what the phenomenon was 

 due to. 



'"]. Canton, Phil. Trans. 59: 449, 1769. 



