The Eighteenth Century 167 



puscular material body. Heat and fire were also usually regarded 

 as corporeal bodies, although not necessarily the same, and heat 

 came to be spoken of quite generally as a material fluid, " caloric." 

 The times were definitely materialistic in conception. There was 

 the electric fluid, the magnetic fluid, and the phosphoric principle. 

 The change of view, light as a wave and heat as a mode of motion 

 and a form of energy, was to come at the beginning of the nineteenth 

 century with the work of Thomas Young and Count Rumford, 

 respectively. 



Space does not permit a detailed survey of the views presented in 

 various textbooks, but a few selected quotations from the best-known 

 authors will serve to present the thinking of the day. In chemistry, 

 the importance of Lemery's Traite of the previous century cannot 

 be overemphasized. Its influence in later editions lasted well into 

 the eighteenth century, particularly in medicine. The 1756 edition 

 contains 35 pages on phosphorus and on the Bononian and Bal- 

 deweinian phosphors. 



HERMANN BOERHAAVE 



After Lemery, one of the best known textbooks was Elementa 

 Chemiae, Paris (1724), by the famous Dutch physician, Hermann 

 Boerhaave (1668-1738), professor of chemistry at the University of 

 Leyden. It was translated in 1735 by Timothy Dallowe and in 1727 

 as A New Method of Chemistry by Peter Shaw and E. Chambers of 

 Encyclopedia fame. Shaw was the English physician who edited 

 Bacon's Works. A section (pp. 353-357) of the second (1741) edi- 

 tion (by P. Shaw alone) was entitled, " Of producing true Fire in 

 a cold body, by the sole access of the Air." It dealt with what are 

 called phosphori and also included pyrophori. Boerhaave described 

 Krafft's phosphorus made from animal juices by distillation, and 

 the Homberg pyrophore, made from charcoal of plant parts or ani- 

 mal excrement and alum. Both ignite when exposed to air. 



The emphasis in the book is very definitely on the nature of fire, 

 regarded as an infinite ninnber of little corporeal bodies. In a foot- 

 note it is pointed out that no body " attracts [fire] by any peculiar 

 virtue " except possibly the Bononian and Baldwinian stones, which 

 seem " peculiarly disposed to imbibe and retain fire," i. e., they 

 are a " magnet with respect to fire . . . , having imbibed a stock of 

 fire, and lodged it in their spongeous substance, to be dispensed 

 again by degrees." On the other hand the phosphori from human 

 urine " retain it [fire] so well in their unctuous substance, that it 

 shall keep there in water for 20 years," to " exhale in lucid fumes " 

 when exposed to the air. Boerhaave also wrote: 



