482 History of Luminescence 



johann sebastian albrecht 



In the meantime observations on luminous wood were progress- 

 ing. Johann Sebastian Albrecht (1695-1774) , a professor at the gym- 

 nasium of Gotha, published a work in Latin in the Acta Physica 

 Medica of the Academia Caesaraea Leopoldina for 1740, " De Ligno 

 non Putrido in Tenebris Lucente," in which he emphasized the 

 fact that luminous wood need not be rotten, and might still con- 

 tain half its original moisture. The logs he observed were of fir, 

 felled by a wind storm, and stored in his cellar. On entering the 

 storeroom, Albrecht was dumbfounded by the light and exhibited 

 some samples to a great crowd of his students, who were much 

 impressed. " When they returned to their houses, they illuminated 

 the streets here and there with fragments of still shining bark." 



Albrecht had evidently read a good deal on the subject of lumi- 

 nescence, for he referred to Pliny, Bartholin, Boyle, Reaumur, and 

 in fact to all the well-known writers on the subject, as an introduc- 

 tion to his paper. His findings regarding the luminous wood and 

 his conclusions were presented as follows: 



1. The light was greatest in the bark and wood where the bark had 

 only recently come off. 



2. Not only the place which the bark had covered but also the other 

 sides, though to a lesser degree, were illuminated. 



3. When such wood was dried out, it lost this quality of shining in 

 the dark. 



4. In one way or another it regained it, though to a much lesser degree, 

 when stored in the cellar, thus acquiring again the former proportion of 

 wet and dry. 



5. However, once the logs were dried out still more, though they were 

 again subject to moisture in the cellar, the light would never come back. 



Therefore it is evident that not exclusively decay but only certain 

 characteristics of the wood are necessary for this phenomenon, such that 

 an ethereal substance, freed from its shackles and fetters, pressed and put 

 in motion by the outer encircling air and having suffered friction in its 

 transit through narrow pores, affects our visual sense with what we 

 describe by the name of light. But every single experiment and phe- 

 nomenon in shining bodies proves that the primary and decisive cause 

 [of light] is this friction of air rushing and pressing in. . . . 



In support of the above statement, Albrecht cited Boyle's experi- 

 ment with shining wood, which does not light in a vacuum but does 

 when the air is let in and rushes over it, as well as Reaumur's work 

 with the " dails " (Pholas dactylus) which luminesce when rubbed, 

 and the many cases of light from friction, especially the mercurial 



