Mr. G. F. Rodwell on the Theory of Phlogiston, 13 



curing all diseases, and gives directions for the profitable extrac- 

 tion of gold from flints, did good service to the science. Nicholas 

 Lemery, for the first time in the annals of the science, gave long 

 courses of lectures. As it may be interesting to note the sub- 

 ject matter of chemical lectures delivered towards the end of the 

 seventeenth century, I give below the matter of two of Lemery' s 

 lectures from a course of thirty-four : — 



Lecture 15. 



tc The distillation of Sal Saturni. 



The tincture of Mars, continued. 



The revivification of Mercury. 



The dissolution of Mercury for making corrosive sublimate." 



Lecture 33. 

 " Ninth and last sublimation of the panacea. 



The fixed salt of Carduus Benedictus, ended. 



The distillation of roses. 



Preparation for the distillation of vipers." 



III. Of the supposed nature of fire prior to the rise of the theory 

 of Phlogiston ; specially of Descartes 7 s " materia coelestis," and 

 of Hooke's theory of combustion, 



Epicurus regarded heat as an effluxion of minute spherical 

 particles^ which in virtue of their smallness and of their rapid 

 motion insinuate themselves into the densest substances, and 

 eventually disunite them by the rapidity of their motion. Fire 

 is an intense heat. Cold is an effluxion of angular particles 

 moving less rapidly than the heat-particles. Lucretius held that 

 both the light and heat of the sun are the result of the rapid 

 motion of "primary particles" *. Cardanusf to a certain extent 

 adopted the views of Epicurus : he frequently speaks of " motus 

 ignis " and " motus caloris. ,} Flame is " aer accensus ;" fire is 

 heat " in immensum auctus" and it penetrates everything on ac- 

 count of its rapid motion : — " Ignis enim calidissimus, tenuissi- 

 mus, celerrimi motus, ac qui facile omnia invadat, et momento 

 maneat solum." Robert Fludd, writing in 1617, affirms that 

 heat is not the actual essence of light, " sed quasi ultimus ejus 

 actionis effectus, immediate a materia? motu profluentis"{. 



During the Middle Ages the elemental nature of fire was 

 almost universally admitted, and the two kinds of fire (treated 



* Principio perssepe leveis res, atque minutis 



Corporibus factas, celereis licet esse videre. 

 In quo jam genere est solis lux, et vapor ejus, 

 Propterea quia sunt e primis facta minutis : 

 Quae quasi truduntur, perque aeris intervallum 

 Non dubitant transire, sequenti concita plaga. 



t Born 1501, died 1576. t De Macrocosmi Historia. 



