xvi Proceedings. {February 22nd, ipo^.. 



raising a platinum plate to a white heat by ' focussing ' on it a 

 stream of cathode-rays inside a Crookes' tube. 



VIII. The mechanical effect of the cathode-rays in driving 

 a windmill was shown to anticipate the not yet discovered 

 mechanical ' perpetuum mobile ' worked by radium rays. 



IX. By means of diagrams in which the radium atom was 

 depicted as a shell charged with four separately and inde- 

 pendently exploding charges the disintegration theory was 

 illustrated. The emanation was represented as the residue of 

 the original atom in which a charge had exploded and blown 

 away fragments in the form of a rays ; etc, 



X. Some radium emanation obtained that morning by 

 pumping off the gases from a closed radium solution was 

 exhibited in a glass tube containing a piece of the mineral 

 willemite (zinc silicate). The latter fluoresced brilliantly a 

 beautiful green under the action of the rays from the emanation 

 inside the tube. The radium from which this effect in the first 

 instance is derived had been left in London. Afterward the 

 same emanation was shown in a tube containing the mineral 

 sparteite which fluoresces a ruddy orange or pink. 



XL The gaseous nature of the emanation of radium was 

 shown by blowing air through a small quantity of a radium 

 solution, which had been closed up for some time, then through a 

 long tube on to the charged silk tassel which was instantaneously 

 discharged. 



XII. The condensation of the emanation at low tem- 

 peratures was shown by blowing the emanation from the tube 

 (Expt. X.) through a glass spiral immersed in liquid air, into a 

 long tube containing a screen of phosphorescent zinc sulphide. 

 The emanation was condensed in the spiral and none passed 

 into the tube beyond. On removing the Hquid air and gently 

 blowing through the spiral into the tube beyond, the emanation 

 was blown out as the spiral warmed up and made the zinc 

 sulphide screen intensely bright. The passage of the light up 

 the tube as the blowing was continued well showed the ordinary 

 gaseous nature of the emanation. 



