Dr. Andrews and Mr. P. G, Tait on Oxone. 435 



has been\ experimentally ascertained. The author considers that 

 this confirms the opinion he ventured to offer in his previous 

 paper; for if the pulsations or vibrations of an electrical discharge are 

 greatest in the bright bands and least in the obscure, this system of 

 interference or of pulsations would also account for the entire absence 

 of stratifications when the air or gas is not sufficiently rarefied, as 

 well as when the vacuum becomes nearly perfect, while the gradual 

 change of narrow to cloud-like stratifications is thus satisfactorily 

 explained. 



In an additional note to his Paper, the author describes some 

 further experiments, particularly one of moving the vacuum-tube to 

 and fro in a rapid manner, or rotating it in a plane, while the dis- 

 charges are made, either singly or continuously : in the latter case the 

 stratified discharges are separated, giving the appearance of an illumi- 

 nated fan or wheel ; in the former, only a single discharge is per- 

 ceptible, taking place in whatever direction the tube may at the 

 instant be placed. The author considers this experiment as con- 

 firmatory of his former opinion, that the stratifications are entirely 

 due to a single disrnj)tion of the primary circuit, 



January 20. — Sir Benjamin C.Brodie, Bart., President, in the Chair. 



The following communications were read : — 



" Second Note on Ozone." By Thomas Andrews, M.D., F.R.S., 

 and P. G. Tait, M.A., F.C.P.S. 



Since the publication of their " Note on the Density of Ozone" 

 (Philosophical Magazine for Feb. 1858, p. 14C), the authors have 

 been occupied with an extended investigation into the nature and 

 properties of that body. The inquiry having proved more protracted 

 than they anticipated, they have thought it proper to send to the 

 Royal Society a brief notice of some of the more important facts 

 which they have already observed, reserving a description of the 

 methods employed, and of the details of the experiments, for a 

 future communication. 



The commonly received statement, that the whole of a given 

 volume of dry oxygen gas contained alone in an hermetically sealed 

 tube can be converted into ozone by the passage of electrical sparks, 

 is erroneous. In repeated trials, with tubes of every form and size, 

 the authors found that not more than yJ^j P^'"'^ ^^ *^^^? pxygen 

 could thus be changed into ozone. A greater effect was, it is true, 

 produced by the silent discharge between fine platina i)oints ; but 

 this also had its limit. In order to carry on the process, it is neces- 

 sary to introduce into the apparatus some substance, such as a 

 solution of iodide of potassium, which has the property of taking 

 up, in the form of oxygen, the ozone as it is produced. After many 

 trials, an apparatus was contrived in the form of a double U, having 

 a solution of iodide of ))otassium in one end, and a column of frag- 

 ments of fused chloride of calcium interposed between this solution 

 and the part of the tube where the electrical discharge was passed. 

 The chloride of calcium allowed the ozone to pass, but arrested the 

 vapour of water ; so that, while the discharge always took place iu 

 2G3 



