536 



Prof. E. Villari on 



formed of a thin leaf of aluminium. Two tubes, o and t y 

 served, with the aid of a constant- pressure bellows, to drive 

 a current of air across the vessel V. A large sheet of lead d 

 soldered to the vessel hindered the radiations from escaping j 



Fisr.l. 



and for the same purpose the tube t was formed with an 

 elbow. The air which had been rendered active by the X- 

 rays in the vessel V passed out through tubes joined on at t 

 and was directed against one of my electroscopes, having a 

 single gold leaf, protected by a metallic box connected to the 

 earth. The gold leaf, by means of two slits cut in the walls 

 of the box and closed by a metallic gauze, was illuminated by 

 a glow-lamp and observed by means of a telescope having a 

 divided-scale micrometer. 



. Air made active by X-rays, in the vessel V, in passing 

 through a long tube, coiled in many turns, loses much more 

 of its discharging power than it does in passing through the 

 same tube if straight. The experiments were executed with 

 tubes of copper, lead, glass, and caoutchouc. The material 

 of the tubes does not influence the phenomena. 



The air which has been made active with X-rays loses a 

 great part of its discharging properties, by streaming upon 

 pencils, or rather bundles, of many long and flexible wires of 

 brass contained in surrounding tubes of glass or metal. 



A flexible tube of copper 3 metres or more in length and 

 1 centimetre in diameter, coiled in 8 or 10 turns, and well 

 insulated with paraffin and with a stem of glass, charges 

 itself to a positive potential of about 30 volts when it is 

 traversed by active air *. It is necessary to insulate the 



* To avoid repetition the term " active " air is here used for air which 

 has "been rendered active by being- exposed to X-rays. The term used by 

 Prof. Villari is " aria ixata." [Tbansl.] 



