1895.] 



President's Address, 



119 



the spectrum of any terrestrial substance spectroscopically examined 

 up to that time, attributed it to a substance in the sun's atmosphere, 

 ■which he called helium. Thus, a substance, discovered thirty 

 years ago in the sun's atmosphere, and accordingly named from the 

 rjnn, has been found in a terrestrial mineral by Ramsay, in his quest 

 after argon. Having got helium into his laboratory, he found its 

 density to be less than 3*9 (ultimately reduced to 2), and, therefore, 

 less than one-fifth (about one-tenth) of that of argon. He sent a 

 specimen to Olszewski, who found* that the treatment by which he 

 had succeeded in liquefying hydrogen — namely, compressing with a 

 pressure of 140 atmospheres, cooling to the temperature of liquid 

 air boiling at low pressure, and then expanding suddenly, showed 

 no signs of liquefying helium. 



Considering the uncertainty as to the density of the gas in 

 which helium was identified and the multiplicity of spectra found 

 for it by various experimenters, Lockyer, who experimented on some 

 eighty minerals and found the yellow line of helium in sixteen of 

 them, thinks it niost probable that it is not a single gas that is 

 extracted either from cleveite or the other minerals, but a mixture of 

 gases of which helium is one ; and this view was supported by Runge 

 and Paschen in their admirable spectroscopic analysis of argon and 

 helium, communicated to the British Associationf at its recent meet- 

 ing at Ipswich. It seems too early to feel sure that the helium 

 found by Ramsay in the gas from cleveite, if perfectly purified of 

 nitrogen and other known gases, is a single gas, or is a mixture or 

 combination of several. Before another anniversary meeting of the 

 Royal Society, it is probable that we shall have certain knowledge, 

 without any doubt as to this question. Meantime, at our present 

 anniversary, we may be satisfied to feel that if there are several new 

 gases, of which one, at least, has density less than a quarter of that of 

 oxygen, the discovery will be several times as interesting as if the 

 helium now discovered proves to be only one gas, 



Copley Medal. 

 Dr. Karl Weierstrass, For. Mem. R. 8. 



"Dr. Karl Weierstrass is distinguished for his investigations in pure 

 mathematics, extending over a period of fifty years. He is one of 

 the great pure mathematicians of the century. 



Among his researches, dealing with many branches of the science 

 in which his work is of significant effect, may be specially men- 

 tioned : — 



(i.) His investigations in pure algebra, particularly in relation to 

 * ' Nature,' October 3, 1895. 



f ' British Association Keport,' Section A, September 18, 1895. 



