538 On Air subjected to X-rays. 



moderate breadth, put into tubes of glass or metal traversed 

 by active air, take positive charges if they are long, and 

 negative if they are short. In my researches the positive 

 charges grew with the length of the cartouches, beginning at 

 about 15 centimetres ; and the negative grew with a diminu- 

 tion of the length of the same from about 12 centimetres 

 down to 2 centimetres. 



Ribbons of gauze 2 centimetres wide and of various lengths 

 (from 20 to 60 centimetres), rolled up into a cylinder 2 

 centimetres high, and placed in a tube of glass or brass, took 

 a positive or a negative charge from the active air according 

 as the air was blown more or less gently through the cylinder. 



It is to be noted that the charges received are not always 

 of the same intensity, and to obtain them energetically it is 

 necessary to insulate the tubes perfectly with paraffin, and 

 also always with a glass stem. 



The phenomena indicated above cannot be attributed to 

 chemical actions, but on the contrary seem to be produced by 

 a special rubbing of the active air upon metallic surfaces, as 

 the result of which these assume one of the charges, while the 

 other charge ought to manifest itself in the air. But from 

 my very numerous measurements made upon the discharge 

 of the electrometer produced by active air which has streamed 

 against metallic cartouches connected to the soil, it results : 



(1) that the air had not lost all its discharging virtue, and 



(2) that it had a little of the charge of the cartouches (instead 

 of having a charge of contrary sign to them) which it trans- 

 ported or conducted from them to the electrometer. 



I have shown in another place * that active air by streaming 

 against an electrified body is reduced either to ordinary air 

 or to air charged with the electricity which disappears. 

 Hence it may be supposed that the active air in rubbing upon 

 the metallic surfaces develops the two electricities, one of 

 which manifests itself upon these surfaces, and the other goes 

 to reduce the active air to ordinary air, and therefore does 

 not become manifest. Thus it might be explained also how 

 active air streaming against these metallic surfaces is trans- 

 formed into ordinary air. Therefore this is simply a hypo- 

 thesis relative to phenomena which require further study. 



* Dell' azione dell' elettricita sulla virtu scaricatrice dell' aria ixata. — 

 Rendiconti delV Accademia di Bologna, 1899-1900. 



