22 Anmversary Address by Sir William Huggins. | Nov. 30, 
ducting the operation in high vacua, were tracked out by him to a repulsion 
arising from radiation, which was ultimately ascribed by theory to the action 
of the residual gas. This phenomenon, illustrated by the radiometer, opened 
up a new and fascinating chapter in the dynamical theory of rarefied gases, 
which the genius of Maxwell, O. Reynolds, and others has left still incomplete. 
The improvements in vacua embodied in the Crookes tube led him to a 
detailed and brilliant experimental analysis of the phenomena of the electric 
discharge across exhausted spaces; in this, backed by the authority of Stokes, 
he adduced, long ago, powerful cumulative evidence that the now familiar 
cathode rays, previously described by C. F. Varley, must consist of projected 
streams of some kind of material substance. His simple but minutely careful 
experiments on the progress of the ultimate falling off in the viscosity of 
rarefied gases, from the predicted constant value of Maxwell, at very high 
exhaustions, gave, in Stokes’ hands, an exact account of the trend of this 
theoretically interesting phenomenon, which had already been approached 
in the investigations of Kundt and Warburg, using Maxwell’s original method 
of vibrating discs. 
These examples, not to mention recent work with radium, convey an idea 
of the acute observation, experimental skill, and persistent effort, which have 
enabled Sir William Crookes to enrich physical science in many departments. 
RUMFORD MEDAL. 
The Rumford Medal is awarded to Prof. Ernest Rutherford, F.R.S., on 
account of his researches on the properties of radio-active matter, in particular 
for his capital discovery of the active gaseous emanations emitted by such 
matter, and his detailed investigation of their transformations. The idea of 
radiations producing ionization, of the type originally discovered by Réntgen, 
and the idea of electrified particles, like the cathode rays of vacuum tubes, 
projected from radio-active bodies, had gradually become familiar through the 
work of a succession of recent investigators, when Rutherford’s announcement 
of a very active substance, diffusing like a gas with a definite atomic mass, 
emitted by compounds of thorium, opened up yet another avenue of research 
with reference to these remarkable bodies. The precise interpretation of the 
new phenomena, so promptly perceived by Rutherford, was quickly verified 
for radium and other substances, by various observers, and is now universally 
accepted. The modes of degradation, and the enormous concomitant radio- 
activity, of these emanations, have been investigated mainly by Rutherford 
himself, with results embodied in his treatise on Radio-activity and his recent 
