NATURAL SCIENCE IN SEVENTEENTH CENTURY 259 



the formal introduction of which into chemistry was only made a 

 century later by Lavoisier. Van Helmont also points out that his 

 gas sylveslre is produced by the action of acids on shells, is en- 

 gendered in putrefaction and combustion, and is present in caves, 

 mines, and mineral waters. In these ideas and passages we find an 

 agreeable departure from the mysticism of the alchemists and the 

 wild surmises of Paracelsus. At the same time Van Helmont's 

 ideas in other directions were crude enough, since he is credited with 

 a recipe for the artificial production of mice from " corn and sweet 

 basil." 



FROM PHILOSOPHY TO EXPERIMENTATION. The seventeenth 

 century differs from all before it in the increasing attention paid 

 to experimental science. From the philosophizing of Paracelsus 

 and Gilbert it is agreeable to pass to the experimental work of 

 Harvey, Torricelli and in chemical inquiries to Van Helmont, whose 

 logical successor is Robert Boyle (1627-1691), already mentioned 

 for his work on the resistance, or "spring," of the atmosphere, etc. 

 Among many other ingenious experiments Boyle worked on evapo- 

 ration, in air and in vacua; on boiling and on freezing; and on 

 the effects of exposing animals to the diminished atmospheric pres- 

 sure produced by the air-pump. In this direction he was the 

 first to prove that fishes require air dissolved in the water in 

 which they live. He also studied the rusting of metals a 

 problem then widely discussed and from all his studies con- 

 cludes that there is in the atmosphere some vital substance which 

 plays a principal part in such phenomena as combustion, respira- 

 tion, and fermentation. When this substance has once been con- 

 sumed, flame is instantly extinguished, and yet the air from which 

 it has gone seems nearly intact. He wrote a treatise entitled, Fire 

 and Flame weighed in a Balance, in which he described the increase 

 of weight of metals on calcination. But as he got about the same 

 results whether the crucible was open or shut, he was misled into 

 the belief that the air had little to do with his results, which he 

 attributed rather to the fixation of the "fire" by the porous 

 crucibles. In these and Boyle's other experiments it is plain that 

 we are rapidly moving from alchemical and iatro-chemical stages 



