340 



Profs. J. J. Thomson and R. Threlfall. [May 6, 



We have made no attempts to ascertain the chemical properties of 

 this modified gas, and there are other points which we should have 

 liked to develop before publishing an account of our experiments, but 

 as one of us is leaving Cambridge for Australia it seemed advisable to 

 publish an account of the experiments we have been able to make 

 together. 



We are indebted to Mr. Robinson for advice on some chemical 

 points, and we cannot conclude without acknowledging how much we 

 owe to the zeal and ability of Mr. Sinclair, the Assistant at the 

 Cavendish Laboratory, who has done much the greater part of the 

 large quantity of glass-blowing required for this investigation. 



II. " Some Experiments on the Production of Ozone." By J. 

 J. Thomson, M.A., F.R.S., Fellow of Trinity College, and 

 Cavendish Professor of Experimental Physics in the Uni- 

 versity of Cambridge, and R. Threlfall, Cams College, 

 Cambridge, and Professor of Experimental Physics in the 

 University of Sydney. Received May 1, 1886. 



The first experiment was made in order to see whether ozone could 

 be formed by placing oxygen in a very strong electric field, the field, 

 however, being just not strong enough to cause sparks to pass through 

 the gas. 



This experiment finally took the following form :— ABC is a box 

 made of flat pieces of glass about iVth of an inch thick, fastened 

 together with paraffin ; into the box two glass tubes, G and H, are 

 inserted, the air entering the box through Gr, and leaving it through 

 H. Against one side of the box a glass bottle, D, with flat sides, is 

 placed and filled with water containing a little sulphuric acid, this 

 serves as one electrode ; the other electrode is a blackened tin plate, 

 E, placed against the opposite side of the box, the distance between 

 the electrodes being an inch and a half. The two electrodes are 

 connected with the terminals of a Holtz machine. By altering the 

 distance between the terminals any difference of potential can be 

 produced between the plates. When the terminals are close together 

 all the sparks pass between them, but when they are pulled far apart 

 the sparks flash across the box, the discharge taking the form of a 

 great number of separate sparks from the inside of one plate to the 

 inside of the opposite one; the appearance of the box when the 

 discharge passes is very pretty, it looks as if several hundred bright 

 silver nails with broad heads were connecting the insides of the box. 



The air entered the box through the tube G, having previously 

 passed through a series of tubes and bottles filled respectively with 



