The Seventeenth Century 129 



faction; and that is now generally granted by all, to be caused by the 

 motion of the parts of putrifying bodies. That the Bononian stone shines 

 no longer than it is either warmed by the Sun-beams, or by the flame 

 of a Fire or of a Candle, is the general report of those that write of it, 

 and of others that have seen it. And that heat argues a motion of the 

 internal parts, is (as I said before) generally granted. 



But there is one Instance more, which was first shewn to the Royal 

 Society by Mr. Clayton a worthy Member thereof, which does make this 

 Assertion more evident then all the rest: And that is. That a Diamond 

 being ruh'd, Struck, or heated in the dark. Shines for a pretty while after, 

 so long as that motion, which is imparted by any of those Agents, re- 

 mains. . . . That the shining of sea-water proceeds from the same cause, 

 may be argued from this, That it shines not till either it be beaten 

 against a Rock, or be some other wayes broken or agitated by Storms, 

 or Oars, or other percussing bodies. And that the Animal Energy es or 

 Spirituous agil parts are very active in Cats eyes when they shine, seems 

 evident enough, because their eyes never shine but when they look very 

 intently either to find their prey, or being hunted in a dark room, when 

 they seek after their adversary, or to find a way to escape. And the like 

 may be said of the shining Bellies of Gloworms, since 'tis evident they 

 can at pleasure either increase or extinguish that Radiation. 



It seems probable that Hooke regarded the vibration of hot 

 incandescent bodies as self-evident and consequently devoted his 

 argument to proving that light without heat was also the result of 

 vibratory motions. His continued interest in luminescence can be 

 inferred from a number of quotations. 



In a letter to Boyle, August 15, 1665,^^ concerning various mat- 

 ters, Hooke ends by saying, " I made last night also a pretty odd 

 discovery of a new kind of shining animals, whose blood, or juices, 

 did shine more bright than the tail of a glow-worm, when the candle 

 was put out." It is possible that this new animal was a luminous 

 centipede but no further reference was made to it. 



In The Posthumous Works of Robert Hooke, M. D., S. R. S., by 

 Richard Waller, published in 1705, Hooke expressed his ideas on 

 the light of fish (p. 48) : 



Fish when fresh or newly dead shine not or afford no Light, when they 

 begin a little to taint and ferment as 'twere, they begin to shine or glare, 

 but as they grow more putrid and rot, so again the Light decreases and 

 at last goes quite out. So that it seems for the production of Light in 

 such a Body there is requisite a determinate Degree of Fermentation or 

 Corruption. 



^^ From R. T. Gunther, Early science in Oxford. The life and work of Robert 

 Hooke, 6: 250, 1930. 



