January 28, 1904] 
NATURE 
299 
radium compound are derived from several distinct 
atoms, the parent radium atom, and the successive 
products of its disintegration, it is to be expected, as 
Rutherford has pointed out, that the velocity of the 
a particles will vary within certain limits. Becquerel, 
however, states that the « radium rays in his experi- 
ments were deflected as a homogeneous pencil. More- 
over, according to the same authority, they possess the 
remarkable property of being the more difficult to 
deviate for any given strength of field the greater the 
distance of air traversed. Both these observations 
seem contrary to what we should expect, and the latter 
especially is difficult to account for. 
With regard to the ‘ spinthariscope’’ effect of the 
a ray when it impinges on a zinc-blende screen, dis- 
covered by Crookes, it appears probable from the work 
of Becquerel, Tommasina and others that the scintilla- 
tions are not caused, as was at first thought, by the 
direct impact of the individual a particle, but are due 
to cleavages provoked in the crystals of the blende by 
the bombardment, each cleavage, rather than each 
impact, giving rise to a flash of light. 
The spontaneous heat evolution of radium to the 
extent of 100 gram-calories per gram of radium per 
hour, which was established some months ago by 
Curie and Laborde by direct calorimetric experiments, 
although it is the fact about radium which has 
appealed most strongly to the general imagination, 
hardly came as a surprise to those who were aware of 
the other properties of the element. Rutherford and 
McClung in 1901 estimated the energy radiated from 
a gram of uranium oxide as at least 0.03 calorie per 
gram per year, and it was known that this must be 
increased at least a million times for the case of 
radium. In addition, the well known chemical actions 
of the radium rays—the conversion of oxygen into 
ozone, and the decomposition of water into its elements 
—showed that their energy must be very considerable. 
The recent discovery of Rutherford and Barnes that 
more than 7o per cent. of the energy evolved from 
radium is due to the insignificant amount of eman- 
ation and the products of its further change, less than 
30 per cent. being due to the element itself, follows 
as a direct consequence of the disintegration theory. 
It furnishes, it would seem, an almost unanswerable 
argument against the view that the energy evolved 
from radium is derived from an external source of 
unknown nature. 
The view that radio-activity proceeds independently 
of temperature, which was originally arrived at by 
Becquerel by his study of the radiations of uranium, 
and is now generally recognised, was confirmed 
by M. Curie last year by some careful measurements 
of the rate of decay of the penetrating radiation from 
a sealed glass tube containing the radium emanation. 
He showed that the rate of the decay was not 
affected by variations of temperature between 450° C. 
and —1So0° C. Since it is the universal experience, not 
only for variations in temperature, but also for all 
other agents, that the rate of disintegration is con- 
stant and unaffected by molecular forces, it follows 
that the causes at work which produce disintegration 
are at present entirely unknown. It appears certain 
that it cannot be brought about by any agencies with 
which we are familiar. Sir Oliver Lodge has 
suggested that the unstable condition results from the 
incessant radiation of the internal energy of the atom, 
the latter being a necessary consequence of the elec- 
tronic theory of atomic structure. 
The discovery by Sir William Ramsay and the writer 
that radium is continuously producing helium in 
sufficient quantities to be spectroscopically recognised 
marks a new phase in the development of radio- 
activity by bringing the problem within the range of 
NO. 1787, VOL. 69] 
the ordinary methods of chemical investigation. From 
the disintegration theory it followed that the accumula- 
tion, during past ages, of the final products of the 
change of the radio-elements must exist in the natural 
minerals in which these elements are found. The 
existence of helium in the radio-active minerals, and 
its absence from those which do not contain the radio- 
elements, coupled with the fact that this gas forms no 
compounds but exists in the minerals ‘* occluded ” in 
a curious and unexplained way, pointed strongly to 
the view that it had been formed as one of the products 
of the change of one of the radio-elements during past 
ages, and mechanically imprisoned within the mineral. 
This led to the experiments being undertaken. 
The gradual growth of the helium spectrum in 
a sealed tube in which the radium emanation was 
originally condensed by liquid air and all other gases 
removed by the pump, excludes the view that radium 
may form a slowly decomposing compound with 
helium. The amount produced, as theory requires, is 
excessively minute, and its detection with the small 
quantity of radium available was due to the extreme 
delicacy of its spectrum reaction, and to the refined 
methods of gas manipulation developed by Ramsay 
in his investigation of the rare gases of the atmo- 
sphere. The suggestion that has been made that the 
a particle is an atom of helium has not yet been ex- 
perimentally proved. 
These direct confirmations of the theoretical predic- 
tions show that our knowledge of radio-activity has 
passed from a purely descriptive basis. The numerous 
unrelated and inexplicable experimental facts which 
have accumulated during the seven years the property 
has been known have during the past year been co- 
ordinated harmoniously as the effect of a definite and 
consistent cause. Radio-activity, in consequence, 
claims to-day to rank as an independent science. It 
is a property which may be best described as added on. 
It manifests itself without affecting or being affected 
by the ordinary chemical and physical nature of the 
matter in question, and therefore belongs to the domain 
neither of physics nor of chemistry. There is in conse- 
quence reason for considerable satisfaction that the 
theory of atomic disintegration to which radio-activity 
has directly led is also in the nature of an addition to, 
rather than a controversion of, accepted scientific doc- 
trines. Nothing could be further from the truth than 
the idea that it upsets in any way the atomic theory 
of chemistry. On the contrary, as the bearing of the 
conception comes to be more clearly seen, it will prob- 
ably be recognised that it provides the atomic theory 
with a measure of confirmation and new evidence 
which advances it a little further in the direction of 
that direct experimental proof which we are so 
frequently being reminded it is impossible for any 
theory to attain. FREDERICK SODDY. 
OBSERVATIONS OF GLACIERS AND 
AVALANCHES.' 
Boe the pamphlets mentioned below are issued by 
the Commission Francaise des Glaciers. The 
former mainly consists of a study of the glaciers about 
the head-waters of the Arc, a region which, forty 
years ago, had been visited only by a few Alpine 
climbers, who found the official maps far from accu- 
rate above the snow line; following this are notes 
about glaciers of the Grandes Rousses, a snowy ridge 
1 ‘Rapport sur les Observations Glaciaires en Haute-Maurienne, dans 
les Grandes-Rousses et I Oisans, dans l'été de rg02.” Par M. Paul 
Girardin. Revue de Glaciologie. No. 2 Année 1902. Par M. Charles 
Rabot. Pp. r2r; illustrated. (Paris: Typographie Philippe Renouard, 
1903.) 
oreo peervations sur I’Enneigement et sur les Chutes d’Avalanches, 
exécutées par l’Administration des Foréts dans Jes Departements de 
la Savoie. Pp. 15. (Paris? Au siége du Club Alpin Frangais, 1903. 
