JuLy 16, 1914] 
NATURE 
507 
Proposed International Magnetic and Allied Observa- 
tions during the Total Solar Eclipse of August 21, 
1914 (Civil Date). 
IN response to an appeal for simultaneous magnetic 
and allied observations during the coming total solar 
eclipse, cooperative work will be conducted at stations 
along the belt of totality in various countries and also 
at some outside stations. 
The general scheme of work proposed by the Car- 
negie Department of Terrestrial Magnetism embraces 
the following :— 
(1) Simultaneous magnetic observations of any or 
all of the elements according to the instruments at 
the observer’s disposal, every minute from August 21, 
1914, Itoh. a.m. to 3h. p.m. Greenwich civil mean 
time, or from August 20, 22h., to August 21, 3h. 
Greenwich astronomical mean time. 
To ensure the highest degree of accuracy, the 
observer should begin work early enough to have 
everything in complete readiness in proper time. See 
precautions taken in previous eclipse work as described 
in Terrestrial Magnetism, vol. v., p. 146, and vol. vii., 
16. Past experience has shown it to be essential 
that the same observer make the readings throughout 
the entire interval. 
(2) At magnetic observatories all necessary pre- 
cautions should be taken to ensure that the self- 
recording instruments will be in good operation, not 
only during the proposed interval, but also for 
some time before and after, and _ eye-readings 
should be taken in addition wherever it is 
possible and _ convenient. It is recommended 
that, in general, the magnetograph be run on 
the usual speed throughout the interval, and that, 
if a change in recording speed be made, every pre- 
caution possible be taken to guard against instru- 
mental changes likely to affect the continuity of the 
base line. 
(3) Atmospheric-electric observations should be made 
to the extent possible with the observer’s equipment 
and personnel at his disposal. 
(4) Meteorological observations in accordance with 
the observer’s equipment should be made at convenient 
periods (as short as possible) throughout the interval. 
It is suggested that at least temperatures be read 
every fifth minute (directly after the magnetic reading 
for that minute). 
(5) Observers in the belt of totality are requested to 
take the magnetic reading every thirty seconds during 
the interval, ten minutes before and ten minutes after 
the time of totality, and to read temperatures also 
every thirty seconds, between the magnetic readings. 
It is hoped that full reports will be forwarded as 
soon as possible for publication in Terrestrial Mag- 
netism and Atmospheric Electricity. 
L. A. Bauer. 
Washington, June 23. 
Asymmetric Haloes with X-Radiation. 
A RADIOGRAPH of a lead dise 2-5 mm. thick, raised 
above the plate, does not, as might be expected, appear 
of an even intensity, but gives well within its shadow 
a distinct white ring. The area inside this ring is 
grey, and the annular space outside it dark. Experi- 
ment has shown that its brightness, width, and 
diameter vary with the distances of the disc from the 
_ plate and antikathode. It also changes from a com- 
plete circle to almost a semi-circle, the position and 
dimensions of the absent arc depending upon the 
orientation of the bulb. 
The ring is found to be complete when the X-rays 
are in the plane of the kathode rays and the normal 
of the antikathode, and from 10° to 15° within the , 
NG: (2433, VOL: 93 || 
angle of true reflection, i.e. that at which light sub- 
stituted for kathode rays would be reflected. Diverg- 
ing from this direction the circle becomes increasingly 
incomplete, the break in the curvature being always 
on the side furthest from it. 
Apertures, cubes, cylinders, solid and hollow, 
spheres, etc., of various materials give analogous re- 
sults, the form of the white area depending upon 
the shape of the object. Thus an ebonite cylinde: 
gives this effect in addition to the peripheral bands 
and alternating semicircles described in former letters. 
This phenomenon cannot be attributed to ordinary 
secondary radiation, since the ring is not dispersed by 
strong magnetic fields. Scattering, unless at some 
definite angle, is precluded by the sharpness of out- 
line, and the asymmetry would seem to dispose of 
diffraction and polarisation, since the dark and light 
parts of the ring are opposite, and not at right angles. 
It appears, therefore, that the X-radiation has been 
differentiated into two main types, one of which may 
consist of disparate doublets (magnetic); the polarity 
being distributed radially round a position which coin- 
cides with that of maximum intensity (Kaye). This 
phenomenon bears a close analogy to that of unilateral 
conductivity in crystals. 
W. F. D. CHAMBERS. 
| I. G. Ranxin. 
go Gordon Road, Ealing. 
The Composition of the Atmosphere. 
Mr. A. ParKER (Jour. Chem. Soc., April, 1914) in a 
study of the inflammation of mixtures of methane 
with oxygen and nitrogen, has found that inflamma- 
tion can be brought about more easily in mixtures 
containing nitrogen than in pure oxygen. In fact, 
the mixture which requires for ignition a minimum 
of methane contains only about 23 per cent. of oxygen. 
This unexpected result is traced to the difference in 
the specific heats of oxygen and nitrogen, and not to 
any property of methane. If one may assume that 
combustions at other temperatures behave in a similar 
manner, perhaps all slow combustions can be main- 
tained with a minimum expenditure of energy in a 
mixture of oxygen and nitrogen containing about 23 
per cent. of oxygen. 
The close proximity of this proportion to that of 
atmospheric air is remarkable. Is it possible that 
living matter on the earth’s surface has evolved its 
own atmosphere, as it were, so that the dissipation 
of the energy of metabolism may be a minimum? 
The temporary stimulation of animals by pure oxygen 
is not necessarily contrary to this hypothesis. I should 
be glad to know if the-estimated total amount of 
carbon in organic matter, including coal, is equivalent 
to an amount of oxygen at all comparable with that 
in the atmosphere; or, in other words, if a large 
increase or decrease in the amount of organic matter 
on the earth could alter appreciably the proportion of 
free oxygen in the air. N. P. CAMPBELL. 
Trinity College, Kandy, Ceylon, June 24. 
Elevation of Mouth of Harton Colliery. 
WiLL some reader of Nature kindly inform the 
writer, through this journal, what the elevation above 
sea-level and the location of Harton Colliery are, 
where Sir G. B. Airy made his pendulum observations 
on the force of gravity at the mouth and bottom of 
that mine in 1843, and also if the result of those 
observations is still generally accepted as correct. 
Evan McLennan. 
Corvallis, Ore., U.S.A., June 20. 
