SECT. i. OZONE. 7 



its magnetism increases with, cold and decreases with 

 heat; hence its intensity varies with night and day, 

 winter and summer, but its magnetic property vanishes 

 when it enters into composition. 



Oxygen is perfectly quiescent and passive as a gas in 

 the atmosphere, and as a constituent of water and solid 

 bodies, yet that inactivity conceals the most intense 

 energy, which only requires to be called into action. 

 Thus combustion of extreme intensity takes place 

 when ignited sulphur is put into a vessel containing 

 oxygen gas ; the metal potassium is instantly inflamed 

 by it on touching water ; some of its combinations with 

 chlorine are highly explosive, and phosphorus burns in 

 it with dazzling splendour. Thus a stupendous amount 

 of energy is latent in oxygen under the most tranquil 

 appearance. 



M. Schonbein of Basle discovered that oxygen exists 

 in another state, which has neither the extreme quies- 

 cence on the one hand, nor the intense violence on the 

 other, of its ordinary form ; and to express that inter- 

 mediate condition, in which its activity is less in 

 amount and different in quality, it has been called by 

 another name, viz. ozone, from the following peculiarity. 



It had long been observed that there is a peculiar 

 smell when an electric machine is in activity, and when 

 objects are struck by lightning ; that smell Professor 

 Schonbein ascertained to arise from the change of 

 oxygen into ozone, and actually produced ozone by 

 passing electric sparks through that gas. Ozone differs 

 from oxygen in having a strong smell and powerful 

 bleaching property; it purifies tainted air, changes 

 vegetable colours, and stains starch prepared by iodide 

 of potassium blue, which thus becomes a test of its pre- 

 sence ; yet it certainly is oxygen in an allotropic or changed 

 state, for it readily oxidizes or rusts silver and other 

 metals, and when ozonized gas is sent through a red- 



