68 History of Luminescence 



Among us it happens to many when they use the sweat-chamber that, 

 after they have become rather warm in the chamber and have then 

 entered a cold room, they see flame and hear it crackling when they 

 remove their undergarment, or move it, or strike it after it has been 

 removed. No doubt undergarments absorb the rich fumes and exhala- 

 of bodies, which are easily retained (especially by the many thick clothes 

 used in winter) and are combustible. These fumes, when they have 

 become warm and have been moved into a cold place, since they do not 

 want to be dispersed in the cold air, are rather greatly compressed; and, 

 having been kindled by the motion, burn. For motion brings very many 

 things from potentiality into actuality. Thus the hair of horses in stables 

 sometimes give off a fiery glow when it is scraped with a strigil,^* and 

 the hair of cats, which are warming themselves before a stove or fire, 

 give off a similar glow when they are stroked the wrong way. 



Like many other observers, Gesner incorrectly believed that the eyes 

 of man and other animals emitted light. 



The aurora borealis is described by Gesner in the words of Aris- 

 totle as clefts in the sky, and a great deal of space is devoted to St. 

 Elmo's fire, referred to as " stellae castores," which appeared on the 

 ends of javelins and yard arms of ships. Sometimes this fire took 

 the form of ignis lambens and appeared on the heads of persons. 

 Livy's (Book I, Chap. 39) prodigy concerning a flame about the 

 head of Servius Tullus and Virgil's gentle and harmless {Aeneid, 

 Book II, 11, 680-684) flame that flickered about the hair of lulus is 

 described, as well as many other instances of silent electric dis- 

 charges, quoted from the Meteorologia of Marcus Frytschius Laba- 

 nius and the De Prodigiis Liber of Julius Obseqiiens.^^ 



Gesner's Commentariolus is a good example of the approach to 

 the subject of luminescence in the sixteenth century. The time was 

 not yet ripe for experiment. This first book on luminescence is a 

 disappointment from the scientific point of view, but it did serve to 

 bring together and direct attention to a number of phenomena 

 which were later to receive careful attention. It is unfortunate that 

 there was so much repetition of the statements of others, and so 

 little original observation. ' 



Nevertheless, it is fitting that the " German Pliny," as Cuvier 

 called Gesner, should have turned his attention to luminescent phe- 

 nomena, among his varied and universal interests. Born in Zurich, 

 son of a poor furrier, he studied medicine in Basel and then traveled 

 widely in Europe, but finally settled in his native town, becoming 



^* A Roman instrument for scraping the skin after a bath. 



^5 Obsequens was a Roman writer about whom little is known. He recorded all 

 the wonderful occurrences from the founding of Rome to the time of Augustus. See 

 Chapter I. 



