DISCOVERY Bf MEANS OF NEW EXPERIMENTS. 539 



Coulomb made a large number of experiments for the 

 purpose of discovering the existence of universal mag- 

 netism, and found that all the substances he tried were 

 affected by a magnet. By means of suitable experiments, 

 Gumming and Dr. Clarke, in 1821, discovered that atmo- 

 spheric electricity was capable of producing magnetism. 

 About the year 1825, Christie found, by actual trial, that 

 heat diminishes magnetism. In the year 1827, Savary, 

 by means of experiment, discovered that non-magnetic 

 screens, placed between an insulated copper wire helix and 

 an iron bar in its axis, decreased the magnetising effect of 

 a discharge of frictional electricity passed through the 

 wire. 



Boyle, about the year 1670, discovered, by suitable 

 experiments, that acids turned extract of litmus red, and 

 that litmus therefore was a test for acids. By means of 

 appropriate experiments, Mayow, about the same time, 

 discovered what he called 'fire-air' (i.e. oxygen), not only 

 in the air, but in saltpetre and in acids. He burned some 

 camphor in a vessel of air, and found the bulk of air 

 diminished ; and confining a mouse in a vessel of air, he 

 obtained a similar effect. He discovered that a fire con- 

 sumes the same kind of gas in the air as an animal does. 

 He also concluded that the ' fire-air ' unites with the blood 

 in the lungs of animals during breathing, and produces 

 heat of the blood. Boerhaave (born in 1668) was Pro- 

 fessor of Medicine at the University of Leyden in 1701, 

 and may be considered the founder of organic chemistry. 

 He dried different plants, and distilled them, and thus 

 discovered various essential oils ; he calcined the residue, 

 and obtained the mineral ingredients. By analysing the 

 soils in which they had grown, he found the source of those 

 mineral substances, and made similar experiments and 

 discoveries with regard to the liquids of animals. Dr. 



