The Seventeenth Century 107 



cences well known in his day. Like Kircher, Schott engaged in a 

 great deal of theological speculation, which detracted from the value 

 of his work. 



Lignum Nephriticum and Fluorescence of Solutions 



A particularly interesting observation of Kircher recorded in his 

 book on light (1846) , had to do with the extract of " Lignum 

 nephriticum," so called because it was recommended for kidney 

 complaints by Nicolas Monardes (1493-1588) in 1565, and Fran- 

 cisco Hernandes (sixteenth century) in 1577. The phenomenon is 

 one of the most important in the history of luminescence. An aque- 

 ous infusion of this wood exhibited different colors, which depended, 

 according to Kircher, on the light intensity in which the extract 

 was observed. His exact words will be found in Chapter XI on 

 Fluorescence, but the statement is not correct, as was later pointed 

 out by Newton, Boyle, and others. The color depended on whether 

 the solution was observed by transmitted light, when it was yellow, 

 or by reflected light, when it was blue. Actually the blue light is a 

 type of light emission which has come to be called fluorescence, 

 exhibited by many substances in solution. Kircher appears to have 

 been the first to emphasize the peculiar optical properties of a fluo- 

 rescent liquid, and has frequently been called the discoverer of 

 fluorescence. 



Thomas Bartholin 



The outstanding book of luminescence of the seventeenth cen- 

 tury, the second special treatise on the subject, and one from which 

 many later writers copied, was De Luce Anitnalium of Thomas 

 Bartholin (1616-1680) . Bartholin was a Danish physician, born in 

 Copenhagen, the son of Caspar Bartholin (1585-1629) , a professor 

 of medicine at the University of Copenhagen. The family was a 

 distinguished one. A brother, Erasmus Bartholin (1625-1698) , pro- 

 fessor of mathematics at the University of Copenhagen, discovered 

 the double refraction of Iceland spar in 1669. 



Thomas started traveling when twenty years old, studying at 

 Leyden, Pavia, Naples, Montpellier, and Basel, later returning to 

 Copenhagen to become professor of anatomy at the University. He 

 corresponded with most of the savants of his time. Although best 

 known for his work on anatomy, especially the lacteals and the 

 lymphatic system, we may guess that his extended travels brought 

 him in contact with various luminous phenomena. 



The first edition of De Luce Animalium was published in 1647 



