RECENT PROGRESS IN PHYSICS. 393 



of electricity. Ozone is first formed by the action of the current, and 

 the ozone then oxidizes the nitrogen. 



' § 99. Illumination of phosphorus produced by ozone. — It is well known 

 that at low tem[)eratures, slow combustion of phosphorus does not take 

 place in air free from ozone, and tnere is therefore no illumination in 

 the dark; this, however, appears as soon as ozone is brought into con- 

 tact with the phosphorus. In a receiver containing ozonized air 

 'phosphorus shines at a very low temperature. 



Schonbein has shown this very beautifully by presenting a stick of 

 phosphorus, at a low temperature, to an electrical brush, which, in 

 accordance with the above, determines the formation of ozone. The 

 manner in which the experiment was made is as follows : (Pog. Ann., 

 Ixviii, 38.) 



A piece of phosphorus an inch long, having a clear surface, was 

 placed on a board in conducting connexion with the earth, and the 

 freeend of a wire, connected with the conductorof an electrical machine, 

 brought within a few lines of the pliosphorus. At a temperature of 

 — 2° the phosphorus by itself did not shine in the dark; but when the 

 machine was put in motion, so that an electrical brush played against 

 the piece of phosphorus, a light flame at once issued from its whole 

 length, and, like the tail of a comet, extended far beyond the piece of 

 phosphorus. If the machine be stopped the illumination of the phos- 

 phorus ceases in a few seconds. 



Schonbein obtained a very beautiful illumination by the following 

 arrangement : A copper wire was coiled around a stick of phosphorus 

 an inch long, so that the end of the wire extended about a line beyond 

 the phosphorus, as shown in fig. 85. The ^'=' ^^' 



other end of the wire is connected with the 

 conductor of an electrical machine. At a 

 temperature below U° the phosphorus did 

 not shine at all in the greatest darkness ; 

 but in turning the electrical machine, so that a strong brush appeared 

 at the end of ihe coil, a luminous cone protruded from the middle of 

 the brush, which attained a length varying from a i'ew inches to some 

 feet, according to circumstances. The longest cone obtained by Schon- 

 bein was 2| feet. With powerful machines such cones should be 

 obtained of still greater length. 



It may be assumed without hesitation that this luminous train is 

 nothing else than the vapor of phosphorus in slow combustion. 



The luminous train vanishes with the electrical brush. 



