402 Transmission of Emanations of Phosphorus through Air, 



grid kept at potential zero, so that escape around the edge 

 would require a passage of 8 to 10 centims. to reach the other 

 plate. This suffices, and the plates may then be placed quite 

 closely together on opposite sides of the barrier. Energetic 

 action is secured at a distance apart of about 1 centim. 



The general result obtained was definitely against any 

 obscure radiation (1 omit the data). The emanation passes 

 with great difficulty and loss in quasi-gaseous form even 

 through very thin porous barriers. It is stopped by impervious 

 media however thin. Oiled tissue-paper cuts off the ions 

 unconditionally. Negative leakages are sometimes observed 

 with such barriers as celluloid, due no doubt to static charges 

 produced by friction. One is also easily misled by conduction. 



13. It was thought that temperature might possibly have 

 some discriminating influence on the charge in relation to its 

 tendency to pass through paper. No effect was detected. 

 Change of the sign of the charge was without appreciable 

 result. 



14. In conclusion, I will briefly advert to a few endeavours 

 to detect ionization in other dust-producers. The method 

 consists in blowing dust-laden air between the plates of the 

 condensers, the current entering the centre of the earthed 

 plate and escaping at the edges. Thus 86,000 cubic centims. 

 of air bubbled through concentrated sulphuric acid in about 

 six minutes, produced an electric leakage equivalent to but 

 c' = '0005, while the leakage of the condenser before the 

 experiment was c'^'0010. Hence the effect is increased 

 insulation to the exclusion of all ionization. The same air 

 current tested in the colour-tube gave an intensely opaque 

 field, showing a condensation producing potency of high 

 order. 



Amnionic polysulphide tested in like manner gave similarly 

 negative results. About 80,000 cubic centims. passed in five 

 minutes through the condenser showed no leakage whatever, 

 whereas the insulation leakage was originally equivalent to 

 ^ = •0006. In this case, however, the current of mixed gases 

 produced only just perceptible darkening of the field of the 

 colour-tube, evidencing therefore but slight tendency to pro- 

 duce condensation. The effect of this reagent on the colour- 

 tube is in general very fleeting. When evaporating from 

 the stopper of a bottle it is very active, but only momentarily, 

 as a rule. If, however, the current of air is replaced by a 

 current of coal-gas (which is itself somewhat " dust "-laden, 

 as appears when the test is made with the colour-tube), the 

 effect is much more persistent. Indeed, if the air of a large 

 room is rendered impure in this way, it reacts on tL6 colour- 



