36 



hot poker. If the hot poker be applied to one side of the cloth, 

 and blotting paper be applied to the other, the grease, in its hurry 

 to get away from the poker, is driven into the paper. 



The curious phenomenon of "capillary attraction" was 

 also dealt with by the lecturer as one of the eftects of surface 

 tension. When the ends of fine tubes are immersed in liquid, 

 the contractile force of the surface film pulls the water up the 

 tubes, he said, to a height inversely proportional to the diameter 

 of the tube. Soap bubbles, ripples on a liquid surface, the effect 

 of electricity on the " skins " of liquids, and finally the minute 

 thickness of these " skins " were among the other matters which 

 Dr. Draper spoke about. It appeared that the thickness of the 

 subject of his paper was no greater than between 1 — 100,000th 

 and one millionth part of an inch. " Somewhere about here," 

 he concluded, "we reach the limits of physical divisibility, and 

 also of my remarks." 



WEDNESDAY, APKIL 26th, 1899. 



Hiintgm Hags as an Attr tn ^rimtiftr 

 inbestrgatinn, 



BY 



Mr. E. PAYNE, M.A. 



R. PAYNE first gave a short description of the discovery of 

 the X-rays by Professor Rontgen at Wiirzburg in Novem- 

 ber, 1895, reminding the audience that the subject had already 

 been treated at a previous meeting of the Society soon after the 

 discovery. 



He pointed out that there were two methods of using the 

 rays in scientific investigations: 1, by the aid of the phenomenon 

 of fluorescence ; 2, by the use of the photographic plate. 



Different substances become fluorescent when the X-rays 

 fell upon them, one of the best for practical use being platino- 

 cyanide of barium, fine crystals of which were spread upon a 



