Ionized Phosjjhorus Emanation in Tubes. 49 



Since rv/2(% — a / ) is about '093, the volume ratio, V/V, should 

 be between 15 and 20. The observed values rarely exceed 2, 

 often falling much below this. The coefficients k are thus 

 too small as compared with the preceding set. 



It is interesting to compare the degree of dilution here with 

 the above cases. The volume of saturated air added rarely 

 exceeded 1 or 2 litres/min. The volume of air traversing the 

 tube and due to the jet is 120 litres/min. The dilution is thus 

 from 50 to over 100. The above cases of dilution with narrow 

 tubes would be given by 



n/n =e- kr *l 2 ' 6SV , 



while in the tube. Otherwise, since w V = wV for a given 

 colour, the chart gives n/n at once. The range of values 

 does not exceed 11 (grey rubber), the other maxima being 

 7 (lead, rubber), 4 (lead, glass), terminating with 1. Hence 

 the orders of dilution in the two experiments are very 

 different. 



The results for the tin tube are naturally much less certain, 

 because the colours become dull after the dust has passed 

 through great lengths (50 feet) of tube, or they flicker, and 

 because v is not easily found. Still the preservative qualities 

 of dilution are undeniable ; and my observations again lead 

 me to disbelieve that diffusion within this wide, eddying current 

 (tested) can be in question. Ignoring it, it seems most pro- 

 bable to adopt recent suggestions (J. J. Thomson, Rutherford, 

 Townsend) that new ions are being continually reproduced 

 from neutral molecules by collisions. From the present 

 experiments with wide tubes, it would then follow that when 

 the ionized air is markedly diluted, the new ions produced 

 are in excess of the old. From this one may argue that their 

 velocity must diminish, for a corresponding excess of energy 

 is being potentialized. Admitting the delicate nature of this 

 speculation*, it is certain, unless I have misunderstood the 

 difficult observations with wide tubes, slow currents, and weak 

 ionization ; k here in all my experiments has never exceeded 

 J, and often fallen below ^j, of the very definite values for 

 small-bore tubes, swift air-currents, and nearly saturated 

 ionization. 



Brown University, 

 Providence, U.S.A. 



* Another way out, possibly, would be the introduction of the above 

 coefficient of decay k'. Observations of a different character, which T will 

 communicate in the next of the present series of papers, seem to justify 

 the position taken in the text. 



Phil. Mag. S. 6. Vol. 2. No. 7. July 1901. E 



