526 History of Luminescence 



luminous particles of the sun, and even the moon, impregnated by 

 water; as is the case in the Lapis Bononiensis, and Baldwin's phos- 

 phorus." On the other hand, Pontoppidan himself was inclined to 

 believe the light was due to " worms," as indicated by the studies at 

 Venice in 1750. 



The idea that the light of the sea came from the sun was ex- 

 pressed by Joseph Mayer (1752-1814) , a professor of natural history 

 at Prague and later at Vienna. Unlike others, Mayer (1786) car- 

 ried out experiments to prove his point. He learned from the inhabi- 

 tants along the Adriatic that there was not much luminescence of 

 the sea after stormy, cloudy days, even when it is calm at night, 

 and he himself noted during a visit to Trieste in 1783 that the sea 

 was especially luminous on agitation after calm days with a bright 

 sun; also that sea water from a depth of nine fathoms where the 

 sunlight was weaker did not luminesce very well. However, if this 

 deep sea water was kept in jars exposed to the sun all day, it lumi- 

 nesced markedly at night. 



At the present time it is easy to explain the above results in terms 

 of the distribution and growth of luminous dinoflagellates, but to 

 Mayer, who could detect no living things with a strong magnifying 

 glass, and in addition found that his sea water could be filtered 

 without losing its ability to luminesce, the absorption of sunlight 

 appeared to be the important factor. He proved that there was no 

 electrical charge in sea water that could affect a sensitive electro- 

 meter at the time the light appeared, but as a zoologist, he could not 

 overlook the many kinds of luminous marine organisms previously 

 described, and finally suggested that the light of the sea might come 

 from several causes, one of which was absorption of sunlight. 



Even as late as 1815, Karl Gottfried von Helvig (1765-1844), a 

 general in the army, thought the ocean to be a light magnet. His 

 evidence for this view was similar to that of Mayer, the observation 

 that near Constantinople, at the entrance to the Black Sea, there was 

 a bight, well shaded by trees. Phosphorescence never occurred in 

 this bight although it was common in open water exposed to the 

 sun. Moreover Helvig had examined ocean water that was phospho- 

 rescent and found no animals present. Hence the light could not 

 be due to animals. 



PHOSPHORUS 



Even in modern times travelers frequently explain the phospho- 

 rescence of the sea by the exclamation, " phosphorus." Among the 

 scientists who believed that sea light is connected with this luminous 

 element, Silberschlag ^* (1770) should be mentioned, and also an 



2* Quoted from C. G. Ehrenberg (1834: 429) . 



