THE MERCURIAL PHOSPHORUS. 455 



land spread rapidly over the continent. It was termed 

 "phosphorus mirabilis," "phosphorus igneus," and some- 

 times "light magnet" although the last name is often 

 also applied to the Bologna stone. 



The effect of this discovery was to draw especial atten- 

 tion to all substances which appeared to be naturally 

 luminous, and decaying fish, sea-water and glow-worms, 

 sparks produced by abrasion, the heating of metals to red- 

 ness by friction or impact, were all studied as allied effects, 

 because all of them gave light. Boyle made the subject 

 one of special research; and in aid thereof Clayton sent 

 him huge fire-flies from Virginia, and told him about the 

 sparks which flashed from Madam SewalPs petticoats. 



It is curious to observe how frequently the accidental 

 acquirement of a book precedes the making of a train of 

 discoveries. A little tract on barometers, which happened 

 to have in it an account of Picard's observation, fell into 

 the hands of John Bernouilli, who was then professor of 

 mathematics at Groningen. 1 Bernouilli made up his 

 mind that here was a way of producing light naturally, 

 without the aid of any chemical phosphorus at all; but as 

 the word "phosphorus" was then applied to any substance 

 which became luminous without combustion, he called 

 Picard's phenomenon the "mercurial phosphorus," and, 

 in June, 1700, gives the results of his own experiments on 

 the subject in a letter to Varignon, then a member of the 

 French Academy. The ensuing consequences are a warn- 

 ing against hasty deductions, and besides exhibit the wis- 

 dom of the profound remark of Mr. Diedrich Knicker- 

 bocker, that "it is a mortifying circumstance which greatly 

 perplexes many a painstaking philosopher that nature 

 often refuses to second his most profound and elaborate 



1 See Martin and Chambers: The Phil. Histy. and Memoirs of the R. 

 Acad. of Sci., Paris. London, 1742. 



Histoire de 1'Acad. R. des Sci., from 1666 to 1699. Paris, 1733. 



Histoire de 1'Acad. R. des Sci., for years 1700 to 1707. Paris, 1701 to 

 1708. With accompanying memoirs. Bernouilli's letters are here pub- 

 lished in full. 



