Thermoluminescence 367 



in luminescence, a spectacle which must have aroused considerable 

 interest. The mineral was shown to Duke Frederick Johann of 

 Braunschweig and was brought to the attention of the Royal Society 

 and the French Academy. G. B. von Leibnitz (1710) in his paper 

 on the discovery of phosphors referred to it as the thermophosphorus. 



Henry Oldenburg, Secretary of the Royal Society and publisher 

 of its Philosophical Transactions made a statement (1676) concern- 

 ing the new phosphor in 1676: " An account of four sorts of fac- 

 titious " Shining Substances communicated to the Publisher from 

 very good hands, both in Printed Papers and in Letters not printed." 

 In addition to the " Factitious Paste " of Dr. Baldwin, the Bononian 

 Stone, and the Phosphorus Fulgurans (i. e., the element phos- 

 phorus) , there was the thermal phosphorus, which was called by 

 the Germans, " Phosphorus Smaragdinus, said to be of this nature 

 that it collects its light not so much from the Sun-beams, or the 

 illuminated air, as from the Fire it self; Seeing that if some of it 

 be laid upon a Silver or Copper-plate, under which are put some 

 live coals or a lighted taper, it will presently Shine. ..." 



In the dissertation on phosphors of George Kaspar Kirchmaier 

 (1635-1700) , De Phosphoris et Natura Lucis nee non de Igne (1680) 

 the material is referred to as a green stone powdered and mixed with 

 water which when heated will glow in the dark without smoke or 

 smell. 



Nathaniel Grew, in classifying the gems of the collection belong- 

 ing to Gresham College, described in his Museum Regalis (1681), 

 mentioned 



A Clear and Green Stone, (a kind of Smaragdus) which being heated 

 red hot, shineth in the Dark for a considerable time, sc about l/16th 

 of an Hour ... I tried the experiment myself also. And at the same 

 time observ'd That as it grew hot in the fire its Green colour was changed 

 into a Sky-blew; ^ which it likewise retained so long as it continu'd to 

 shine: But after that, recover'd its native green again. 



The material was also described by R. Southwell in 1698 under 

 the name of Phosphorus metallorum: 



Take Lapis Smaragadi Mineralis (such as is found in the mines of 

 Saxony) and beat it into a very fine Powder. If you strew this very fine 

 on any Metal, and in any Figure, and set the Plate on any hot Coals, in 

 a short time you will perceive in the Dark, a Light to Shine, which will 

 (saith my Author) last as long as you continue the hot Coals, and if you 

 beat out the Fire, it may do again for once or twice, but then the Vertue 

 will fade. 



Factitious means artificial, i. e., prepared. 

 '' The blue thermoluminescence of the green colored stone. 



