2 Proceedings of the Royal Irish Academy. 



through meicury and through alcohol has been investigated. Many different 

 types of ions were discovered. This present work was undertaken to see if 

 any of these groups were formed in the case of ionisation by phosphorus. It 

 was hoped that light might be thrown on the nature of these groups by the 

 examination of ionisation produced in a way entirely different from bubbling. 

 AVe did not propose to investigate the exact mechanism of the production of 

 the ionisation ; our object was meiely to examine the ionisation when produced. 

 Accordinglj' no observations were taken on the phosphorescence, the produc- 

 tion of ozone, or on the various chemical changes whicli accompany the 

 oxidation of phosphorus. 



A cylindrical tube designed to measuie mobilities, similar to that described 

 in the previous papers, was used. A small flat piece of phosphorus was scraped 

 free from oxide under water, dried with blotting-paper, and placed in a narrow 

 glass tube. A current of air was drawn along this tube, through the mobility 

 tube and into a gasometer. The quantity of air passing through the mobility 

 tube per second could be deduced from the rate of motion of the gasometer. 

 The time between the formation of the ions at the phosphorus and the 

 measurement of their mobilities was varied by interposing different lengtlis 

 of tubing between the phosphorus tube and the mobility tube. This time- 

 interval was also varied by changing the rate of the gasometer. A tube 

 containing a plug of cotton-wool was connected to the phosphorus tube so 

 that the room air was filtered before passing over the phosphorus. 



The currents to the inner insulated terminal of the mobility tube for 

 different voltages on the outer tube were measured by means of an electro- 

 meter. Current voltage curves were plotted, and it was seen that they were 

 formed of a number of straight lines. This indicated that different types 

 of ions were present; each type gave rise to a corner on the curve. The 

 mobilities of the various types were calculated by taking the voltages 

 corresponding to the cornei-s as saturation voltages and applying the formula 

 as described in the previous papers. The current-voltage curves were similar 

 to those obtained when air was bubbled through mercury and through alcohol. 

 Examples of these curves were given in the paper on the ionisation due to 

 mercury; accordingly, none are given here. No difference between the 

 positive and the negative electrification either as regards quantity or quality 

 was noticed during this work ; accordingly, no distinction of sign has been 

 made ; the observations of positive ions and of negative ions are practically 

 equal in number. Each group of ions was obtained with both positive and 

 negative electrification. 



