OZONE. 



THE singular gas termed ozone has attracted a large amount 

 of attention from chemists and meteorologists. The vague 

 ideas which were formed as to its nature when as yet it had 

 been but newly discovered, have given place gradually to 

 more definite views ; and though we cannot be said to have 

 thoroughly mastered all the difficulties which this strange 

 element presents, yet we know already much that is interest- 

 ing and instructive. 



Let us briefly consider the history of ozone. 



Nine years after Priestley had discovered oxygen, Van 

 Marum, the electrician, noticed that when electric sparks 

 are taken through that gas, a peculiar odour is evolved. 

 Most people know this odour, since it is always to be 

 recognized in the neighbourhood of an electrical machine 

 in action. In reality, it indicates the presence of ozone in 

 the air. But for more than half a century after Van Marum 

 had noticed it, it was supposed to be the " smell of elec- 

 tricity." 



In 1840, Schonbein began to inquire into the cause of 

 this peculiar odour. He presently found that it is due to 

 some change in the oxygen ; and that it can be produced 

 in many ways. Of these, the simplest, and, in some respects, 

 the most interesting, is the following : " Take sticks of 

 common phosphorus, scrape them until they have a metallic 

 lustre, place them in this condition under a large bell-jar, 

 and half-cover them with water. The air in the bell-jar is 



