The Seventeenth Century 131 



although the light of the full moon, even when concentrated by a 

 large reflecting glass was unable to excite it. 



However, despite his interest in light, and despite his many- 

 sided ability— anatomist, microscopist, physicist, chemist, mechanical 

 genius, and architect— Hooke made no comprehensive study of lumi- 

 nescence, although he saw and commented on every conceivable 

 variety. 



Fermentation and Luminescence 



It will be observed that the word " fermentation " is frequently 

 used by Hooke in connection with organic luminescences. Other 

 writers, also, relied on the word in attempting to explain obscure 

 processes. From the Latin, " fervere," to boil, the designation has 

 indicated any kind of commotion resulting in chemical change or in 

 solution. There was usually bubble formation, either carbon di- 

 oxide bubbles from the activity of yeast or vapor bubbles on heat- 

 ing a liquid. Chaucer spoke of " fermentacioun," and alchemists 

 have used the word, together with putrefaction ^^ and digestion, to 

 indicate almost any kind of chemical change accompanied with 

 motion. The philosopher's stone was visualized as setting up a 

 fermentation in common metals by which they were transformed 

 into gold or silver, thus purifying and elevating them. 



The remark of Gregory Ripley (died 1490) , the English alchemist 

 and poet, in A Compound of Alchymie (1471) that, " Trew Fer- 

 mentacyon few Workers do understand," was particularly applicable 

 in the seventeenth century. Not only Hooke, but Thomas Willis 

 (1621-1675) in De Fermentatione (1659) considered fermentation 

 a vibration or commotion of the particles of the fermentable sub- 

 stance ^® and Neremiah Grew (1628-1711) in the Ariatomy of Plants 

 (1682) declared " The general cause of the growth of a . . . seed is 

 Fermentation." These quotations will serve to indicate the im- 

 portance which has been attached to the word. 



Fermentation was included in textbooks of chemistry and physics, 

 and indeed whole volumes were devoted to the subject. The De 

 Fermentatione of Thomas Willis (1659) was done into English by 

 S. P. Esq under the title A Medico-Philosophical Discourse of Fer- 

 mentation, or the Intestine Motion of Particles in every Body, and 



"Aristotle in De generatione animalium (Oxford edition, ed. by W. D. Ross, 762a) 

 wrote: " All those which do not bud off or ' spawn ' are spontaneously generated. 

 Now all things formed in this way, whether in earth or water, manifestly come into 

 being in connection with putrefaction and an admixture of rain-water. . . . Nothing 

 comes into being by putrefying but by concocting; putrefaction and the thing putre- 

 fied is only a residue of what is concocted." 



^* Justus Liebig's views in 1839 were similar. 



