114 History of Luminescence 



III: Is animal light generated by putrefaction? 



IV: Does animal light come from transparency? 



V: Whether from the blue sky? 



VI: Do animal sparks came from the rubbing of bodies? 



VII: Are our humors the causa efficiens? 



VIII: Does our light come from fire? 



IX: Do animals shine from water? 



X: Does animal light come from whiteness? 



Under each problem, Bartholin gave some prevailing views and 

 usually refuted them by introducing his own conception of light 

 as a fifth element pervading all things and called into being under 

 special conditions. Much of the discussion is meaningless from our 

 present point of view. 



The type of argument used by Bartholin can best be understood 

 from his discussion of problem IX, the origin of animal light from 

 water. He first recalled that moisture is characteristic of animals, 

 for example sweat, or the aqueous humor of the eyes; then cited 

 the general belief that little luminous worms come from dew.^^ 

 " Some think that in the meat at Montpellier, dew, conceived by 

 putrefaction brought forth splendor." He then went on to say that 



Observation teaches that light inheres in water. Flames, the companions 

 and offspring of light often broke out on the sea. Some think the salt ^^ 

 in the sea to be responsible . . . but also rivers, lakes and fountains 

 shine ^^ and salt has also the quality of extinguishing fire. Others sup- 

 pose fattiness of the water to be the cause. Closer to the truth are those 

 who see the origin of fire of the sea in some fiery exhalations and 

 vapors. 



Bartholin's own observations are expressed as follows: 



The light resides not only in the foam but in the water itself, as I have 

 often observed in the upper and lower sea. For the floods stirred by 

 the circular motion of the oars show a very clear splendor, which in 

 bright daylight becomes white. Yes, even without any motion I have 

 extracted from the sea glittering seaweed and, by throwing in some 

 linen [which becomes] tinged with splendor, I have communicated light 

 to neighboring things, emulating the stars. 



The qtiestion as to whether the sea and water in general shine 

 because of smoothness (laevitas) as Aristotle postulated, was con- 



*^ Note that Hesychius made this statement, as quoted by MufFet in Chapter III. 



^* Probably an early recognition that phosphorescence is not observed in fresh-water 

 seas or lakes. Descartes attributed the " burning of the sea " to friction between salt 

 molecules (see Chap. XV of this book) . 



36 Perhaps a reference to reflection of light. 



