74 Transactions of the 



Having made some fartlier observations upon the methods 

 employed by different insects in order to escape from the 

 pupa, and thus enter upon the final, and, apparently, the 

 happiest stage of their existence, Mr. Greene concluded his 

 paper, and upon resuming his seat was much applauded. 



P. E. Ogle read the following paper on 



OZONE. 



In 1785, Yan Marum, at Haarlem, while making some 

 experiments upon the newly-discovered element — oxygen, 

 first noticed and called attention to the peculiar odour 

 attending an electric discharge through this gas, and the 

 action of oxygen possessing this odour upon mercury, namely, 

 that of tarnishing it. Its nature he did not indicate, nor 

 did he advance any theory respecting its formation, but con- 

 tented himself with ascribing it to the natural odour of the 

 ' electric matter.' 



In 1840, M. Schonbein, of Basel, who was also the 

 inventor of gun cotton, first commenced his series of re- 

 searches which ultimately revealed to chemists the probable 

 constitution of this principle, which is one of the most 

 remarkable discoveries of late years, and has attracted much 

 attention. At first he imagined it to be a simple electro- 

 negative substance, analogous to, and in the same class as 

 chlorine, bromine, and iodine, its analogy to chlorine being 

 most striking : (i.) it is poisonous ; (ii.) it bleaches ; (iii.) it 

 removes noxious miasma and sulphuretted hydrogen; (iv.) its 

 C;dour is something alike when concentrated, and exercises 

 an irritating action upon the resj)iratory organs. In his 

 second paper on the subject, he threw out some hints that it 

 might be a constituent of nitrogen ; subsequently, he con- 

 sidered it CO be a compound of oxygen and hydrogen, analo- 

 gous to peroxide of hydrogen (HjOj), which is a syrupy, 

 transparent, colourless fluid, resembling water. It is a 

 powerful bleaching and oxidising agent, owing to the ease 

 with which it parts with half of its oxygen, and may be 

 prepared by acting upon baric dioxide (BaOa) with hydrofluo- 

 silicic acid (2HF.SiF4). Baumert, Williamson, and other 

 chemists advanced the theoiy that the ' ozone ' produced in 

 electrolytic oxygen was teroxide of hydrogen (HgOj), while 

 that produced by electric discharge consisted of peroxide of 

 hydrogen (H2O2). These opinions were generally received 

 in the chemical world, until MM. Marignac and de la Rive 

 conceived the idea that ozone might in no respect differ 

 from oxygen in composition. This suggestion was examined 



