Fourteenth Communication from Dr. Thornton. 207 



other matters, and consequently subject to the general laws 

 of chemical or mixma; affinity, which places its materiality 

 beyond all doubt. It follows likewise that colourless bodies 

 tor this reason when they come into contact with light can 

 produce no heat, because their attraction for the producing 

 matter of light is less than the attraction of this matter for 

 caloric. 



Since wp are thus naturally induced to consider light as 

 a product or mixture of the producing matter of light and 

 caloric, it will be necessary also to introduce this matter 

 under a characteristic name into the nomenclature of na- 

 tural elements. But the producing matter of light is not 

 of itself luminous ; it assumes this quality in the product 

 of its mixture with caloric, and consequently it must be 

 distinguished by the name of photogen from the Greek 

 words (p'juro; and ysiyoiJ-oLi, which signify to produce light. 



Light, and the matter that produces light, must also be 

 a« different from each other as cause and effect. The pro- 

 ducing matter of light may be a component part of many 

 objects in the world, and be distinguished by different qua- 

 lities. It may also exist in the concrete form, mixed with 

 other bodies ; but it can never exist pure without mixture 

 with other elements, because, as already observed, all ele- 

 ments in nature are in a continual state of mutual reaction, 

 and exercise on each other an incessant power of attraction. 



If the producing matter of light and caloric enter into 

 mixture, the result is light ; consequently caloric is that ele- 

 ment which converts the producing matter of light into 

 moveable or radiant light. 



[To be continued.^ 



XXXVI. Fourteenth Communication from Dr. Thornton 

 relative to Pneumatic Medicine. 



March jo, 1604.. 

 To Mr. Tilloch. No. i, Hinde-street, 



SIB. Manchester-square. 



A FEKL happy when I can relate to the philosophic world 

 cures long: ago accomplished, which show also the perma- 

 nency of ^he benefits received; and the present early case 

 is, I think, a very striking example of the efficacy of the 

 aerial remedy. 



Case of Spasms. 



Mrs. Gillespie, ast. 35, a married lady, for near a twelve- 

 month 



