CHEMICAL SCIENCE. 249 



a relatively diminished quantity of this chemical agent, and experi- 

 ment has proved that, during the three months previous to August, an 

 appreciable quantity of ozone could not be detected by the ordinary 

 methods in the air of London. Certain, then, it is, that, during the 

 prevalence of the cholera, we had an atmosphere of low electrical in- 

 tensity deficient in ozone, an agent which would remove, or alter, 

 pestilential miasma." Ozone is formed generally during the process 

 of combustion, and it is well known that large fires have again and 

 again proved effectual in stopping the plague, and like pestilences. 



INFLUENCE OF THE SOLAR RAY UPON OXYGEN. 



AT the meeting of the Swiss Association for the Advancement of 

 Science, Professor Schonbein communicated the result of experiments 

 recently made by him on the influence exerted by solar light on the 

 chemical action of oxygen. From various causes, he was led to sup- 

 pose that the chemical powers or affinities of oxygen are exalted by 

 light, independently of heat. To test the correctness of that conjec- 

 ture by experiment, he put a number of inorganic oxidizable matters 

 in contact either with pure oxygen or with atmospheric air, both 

 being subjected to the action of direct solar light. He found that 

 either pure or atmospheric oxygen, being isolated, readily unites with 

 sulphurets of lead, arsenic, and antimony, all other circumstances, 

 temperature, &c. remaining the same. Moisture, though accelerat- 

 ing the action, is not required to be present in oxygen, in order to 

 obtain the results mentioned. Hence it comes that bands of paper 

 colored brown or yellow by the sulphurets named are completely 

 bleached when exposed to the combined action of solar light and at- 

 mospheric air. According to Schonbein's experiments, lead paper is 

 by far the most sensitive to sunlight ; then comes sulphuret of arsenic 

 paper, and, last, sulphuret of antimony paper. As regards the lead 

 paper, it is so sensitive that, if it be but slightly colored, it will with- 

 in fifteen minutes be turned white in a strong noon sun of June or 

 July. On account of that sensitiveness the sulphuret of lead paper is 

 a sort of photographic paper, and may be used to produce drawings, 

 &c. Professor Schonbein exhibited to the Association a number of 

 such photographic productions, and also copies of prints which he ob- 

 tained by simply putting those prints upon sheets of sulphuret of lead 

 paper, and exposing the whole for hours to the joint action of direct 

 solar light and atmospheric air. Though diffused light acts sensibly 

 upon the lead paper, its action in the camera is too feeble to produce 

 an appreciable effect. If by some means the sensitiveness of the paper 

 could be much increased, positive images would be obtained. Schon- 

 bein does not, however, lay any stress on his discovery in a photo- 

 graphic point of view, its principle appearing to him infinitely more 

 important than its applicability to photographic purposes. But he 

 is inclined to think that, by means of sulphuret of lead paper, a good 

 chemical photometer might be made. Besides the sulphurets men- 

 tioned, Professor Schonbein has under solar influence oxidized some 

 other matters capable of taking up oxygen ; for instance, he has trans- 



