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JANUARY 17, 1907 | 
NATURE 
Further experiments are in progress to examine in the 
early stages the growth of radium in actinium, initially 
freed from radio-actinium and all its products. If actinium 
changes directly into radium, the initial growth of the 
radium should be much smaller than that to be obtained 
three months later, when the products are in approximate 
equilibrium. 
The results of my experiments are thus substantially in 
agreement with those of Dr. Boltwood. There is no doubt 
that the immediate parent of radium is present in actinium 
separated from pitchblende, but certain points remain to 
be settled before it is definitely proved that radium is the 
direct lineal descendant of actinium. Since the proof of 
this relationship between actinium and radium involves 
many important theoretical consequences, I think it is 
advisable to await the results of further experiment in 
this direction before basing far-reaching conclusions 
upon it. E. Rutnerrorp. 
McGill University, Montreal, January 3. 
Helium and Argon in Common Rocks, 
THE quantity of radium found in granites and kindred 
rocks (Proc. Roy. Soc., A, vol. Ixxvii., p. 472), about 
10-"? grams per c.c., suggested that the associated helium 
might be present in sufficient quantity for spectroscopic 
detection. This has proved to be the case. Thus 250 
grams of Matopo granite yielded 3 c.c. of nitrogen on 
heating. This nitrogen, on sparking down, gave a residue 
of about 1/1ooth part of its own volume. The residue 
was introduced into a vacuum tube, and showed the 
spectra of argon and helium quite brilliantly, and in about 
equal intensity. Similar results were obtained with syenite 
rocks from Mt. Sorrel in Leicestershire, and from Norway. 
It seems more than probable that these observations 
afford an explanation of the nature of the gases evolved by 
mineral springs. The invariable presence of a notable 
quantity of helium in such gases has always been con- 
sidered remarkable. It would seem that it may be suffici- 
ently explained by the action of hot water in disintegrating 
common rocks and liberating the gases contained. 
It is my intention to examine a large selection of 
common rocks and minerals, and particularly with the view 
of determining whether helium in them is always associ- 
ated with radium, or whether its presence can ever be 
attributed to radio-activity of ordinary materials. 
Ro ee SaRumn. 
Sunnyside, Cambridge, January 13. 
Ionisation and Absorption and Anomalous Dispersion. 
Dr. Stark (Nature, vol. Ixxiii., pp. 78, 389, 533) has 
given a theory, based on his canal-ray experiments, accord- 
ing to which spectrum series are due to positive ions. It 
occurred to me that its applicability to thermal emission 
might be tested by experiments on the ionisation accom- 
panying the anomalous dispersion in sodium vapour. 
Accordingly, together with Mr. Needham, I made some 
preliminary experiments, using a slight modification of 
Prof. Wood’s well-known apparatus (‘‘ Physical Optics,”’ 
p- 340), of which the results seem to be of sufficient interest 
to deserve publication. 
We used a steel tube, 4o cm. long, with an insulated 
iron wire stretched inside and along it about 1 cm. from 
the sodium surface. The poles of a battery were con- 
nected to the wire and tube through a liquid resistance 
and galvanometer (1 division=10-* ampere about); the 
tube was placed between the collimator and grating of a 
spectroscope, and the image of a horizontal fine wire 
stretched across the slit was observed in the first spectrum 
with a micrometer eye-piece. The separation, due to 
anomalous dispersion, of the two halves of the image on 
opposite sides of the absorption band was assumed to be 
a sufficient measure of the anomalous dispersion. 
Curves constructed from observations of anomalous dis- 
persion and current show that every variation of the 
ionisation, due to some irregularity of pressure and 
temperature, is accompanied by a corresponding variation 
in the anomalous dispersion. 
The simplest explanation of the parallelism between the 
NO.N1942, VOL. 75] 
’ 271 
curves is that the D lines of sodium are due to positive 
ions rather than to neutral atoms, in accordance with 
Stark’s theory. G. A. ScnorTt: 
Physical Laboratory, University College of Wales, 
Aberystwyth, December 20, 1906. 
THE MILLAIS BRITISH MAMMALS. 
ITH the appearance of this volume we have the 
pleasure of congratulating the author on the 
completion of a very heavy task. As we have had 
occasion to remark in our notices of the two earlier 
volumes, from the point of view of pictorial illustra- 
tion the work is in the main all that can be desired, 
and there is little doubt that in this respect it will 
long remain absolutely without a rival. Our very 
heartiest congratulations may accordingly be tendered 
to Mr. Millais and his fellow artists on the result of 
their endeavours to illustrate in an adequate and 
exhaustive manner the living and recently extermin- 
ated mammals of the British Isles. In giving as the 
Ma Se RO 
Fic. 1.—Tbe Hare. From ‘‘The Mammals of Great Britain 
and Ireland.” 
frontispiece of the present volume a picture of a 
southern right-whale attacked by a party of gram- 
puses, or killers, it may possibly be objected that the: 
author has introduced a scene which cannot now be 
witnessed in British waters. Since, however, the past 
as well as the present state of the fauna of our islands: 
enters into the purview of the work, there may be 
justification for such an illustration; and even if this 
be not the case, the privileges of artistic license may 
be pleaded as sufficient excuse. Had space been avail- 
able, we should have had much pleasure in repro- 
ducing one of the full-page illustrations which form 
by far the most striking feature of the work. Fail- 
ing this, we have to be content in presenting to our 
readers (by the courtesy of the publishers) three of the 
smaller illustrations as examples of the pictorial merit 
of the work. 
The groups included in the present volume comprise 
the hares and rabbit; the ungulates, of which (if we 
exclude the white park-cattle, which are obviously 
not wild animals) the red deer, the fallow deer, and 
1“ The Mammals of Great Britain and Ireland.’ By J. G. Millais. 
Vol. iii. Pp. xii+384; illustrated. (London: Longmans, Green and Co., 
1906.) Price 6/. 6s. net. 
