1 82 HOOKE'S VIBRATORY THEORY. 



" But there is one instance more, which was first shown 

 to the Royal Society by Mr. Clayton, a worthy member 

 thereof, which does make this assertion more evident than 

 all the rest : and that is, that a Diamond being rubbed, 

 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, remains (in the same manner as a glass rubbed, 

 struck, or (by a means which I shall elsewhere mention) 

 heated, yields a sound which lasts as long as the vibrating 

 motion of that sonorous body), several experiments made on 

 which Stone, are since published in a ' Discourse of Colours,' 

 by the truly honourable Mr. Boyle." (Jb. p. 55). " It would 

 be too long, I say, here to insert the discursive progress by 

 which I inquired after the proprieties of the Motion of 

 Light ; and therefore I shall only add the result. 



"And, first, I found it ought to be exceedingly quick, 

 such as those motions of fermentation and putrefaction, 

 whereby, certainly, the parts are exceedingly nimbly and 

 violently moved ; and that, because we find those motions 

 . are able more minutely to shatter and divide the body than 

 the most violent heats or vienstruums we yet know. And 

 that fire is nothing else but such a dissolution of the Burning 

 Body, made by the most universal menstruum of all sul- 

 phurous bodies, namely, the Air, we shall, in another place 

 of this Tractate, endeavour to make probable. And that, 

 in all extremely hot, shining bodies, there is a very quick 

 motion that causes Light, as well as a more robust that 

 causes Heat, may be argued from the celerity wherewith 

 the bodyes are dissolved. 



" Next, it must be a vibrative motion. And for this the 

 newly mention'd Diamond affords us a good argument ; 

 since if the motion of the parts did not return, the Diamond 



