Phosphorescence 311 



FORTUNIO LICETI 



The most impressive book on the subject, and at the same time 

 with the least scientific approach, was the Litheosphoriis sive De 

 Lapide Bononiensi, of Fortunio Liceti (1577-1657) , published in 

 1640 while professor of philosophy at Bologna." The title page is 

 reproduced as figure 30. In the 55 chapters and 280 pages there is a 

 detailed account of the various names by which the Bolognian stone 

 was known, its discovery, the places where it occurred, and an at- 

 tempt at explanation. The statements are characteristics of much of 

 the scientific thought of the time. No original experiments were 

 performed but many philosophical and absurd questions were dis- 

 cussed, with citations from the Bible, from Aristotle, and from con- 

 temporary writers. The belief was presented that stones in general 

 arose not only in the ground but also from fully developed animals, 

 although not from plants or imperfect animals like oysters or mussels. 



Liceti's language is hard to understand but he apparently believed 

 that the cause of the light was fire, a kind of burning due to the 

 absorption of simlight. He held that exposure to the sun " impreg- 

 nated " the phosphor with light and that it took some time before 

 the luminescence was " born," an idea probably based on the light- 

 adaption of his eyes. On going into a dark room from sunlight, the 

 phosphorescence could not at first be seen but only as the eyes grow 

 dark-adapted would the slow birth of the luminescence become 

 visible. Impregnation and birth was compared to reproduction 

 among humans and the glow was believed to have the property of 

 repelling all unclean things and bringing pure parts to the surface. 



Liceti went so far in his enthusiasm as to declare that the faint 

 light of the new moon's disk was due to a phosphorescence like that 

 of the Bolognian stone and was not, as Galileo believed, a reflection 

 of sunlight from the earth to the moon. Liceti's statement (Chap. 

 50) led to correspondence ^^ between Prince Leopoldo de Medici 

 (1617-1675) , a founder of the Accademia del Cimento in 1657, and 

 Galileo in 1640, and between Galileo and Liceti in 1640-1641, in 

 which Galileo rather forcibly adhered to his own explanation. These 

 letters were the last that Galileo, already blind, wrote. He died in 

 1642. His corrected reply to Count Leopoldo, fifty pages in length, 



^" The Bolognian stone and a number of other luminescences were mentioned by 

 Liceti in his De lucernis antiquorurn reconditis, etc., Book IV, Chap. 7, Utini (1653) . 

 There is nothing in De luminis natura et efjicientia, 244 pp., Utini, 1640, or in De 

 lucidis in sublimiyigenuarum exercitationum, 120 pp., Patavii, 1641. 



^^ See C. G. Venturi, Memorie e lettere inedite finora o disperse di Galileo Galilei, 

 Part II, Articolo VI, p. 293, Modena, 1821. An account of the controversy will be 

 found in The private life of Galileo (London, 1870) , by Sister M. Celeste. 



