OcToBER 12, 1899] 
DEAT Role 
587 
complicated collection of units themselves similar. Sir Norman 
Lockyer said that if we accept the view that elements of smallest 
atomic weights should appear first in the spectrum of a hot star, 
we must assume the existence of forms of calcium, magnesium, 
iron and copper having atomic weights which are submultiples 
of those assigned to them in ordinary chemistry. Further, the 
division of the spectra of certain elements into series of lines by 
Rydberg, Runge and Paschen, and others indicates that the 
atoms of these elements are complexes ; we shave, therefore, no 
reason to suppose that the so-called ‘‘ atoms” are not dissociable 
at high temperatures. Prof. Oliver Lodge thought the investi- 
gations of Prof. Thomson might turn out to be the discovery of 
an electric inertia, and lead to a theory of mass. Several 
speakers expressed their pleasure in receiving the members of 
the French Association. 
In the very short time remaining after the discussion on the 
previous paper, Prof. Oliver Lodge gave a short account of the 
controversy respecting the seat of Volta’s contact force. 
On Monday the Section was subdivided for papers on mathe- 
matics and meteorology respectively. In the latter department, 
oyer which Sir George Stokes presided, a formal report was 
presented by the committee on solar radiation. Dr. van 
Rijckevorsel read a paper in which he traced an intimate con- 
mection between the activity of sun-spots and the temperature. 
The committee on seismology presented a voluminous report 
on their work, from which it appears that twenty-three stations 
are now equipped with recording seismographs, and registers 
have been received from ten of these. Notes on these registers 
occupy a considerable portion of the report; the rest of the 
report is abstracted from articles which have already appeared 
in NATURE (February 16 and March 1, 1899). Mr. T. F. 
Claxton communicated the preliminary results of a year’s work 
with the seismograph at Mauritius. The diurnal waves are of 
greater amplitude than at any other observing station, and there 
is a well-marked bi-diurnal effect possibly connected ‘with baro- 
metric pressure. Rapid and large changes of the vertical have 
occurred on several occasions, in addition to a constant gradual 
change. Air tremors have given trouble at night. The earth- 
quake effects have been of disappointingly small amplitude, and 
it is suggested that the ocean may act as a damper to earth- 
quake shocks. 
Mr. A. L. Rotch gave an interesting account of the progress 
achieved during the past year at Blue Hill, Massachusetts, in 
the exploration of the air with kites. The Hargrave kite with 
curved surfaces has been found more satisfactory than any other 
form, and the meteorograph records temperature, humidity, 
height and wind. Temperature is found to decrease at first 
with elevation, and afterwards to increase again. The heights 
attained were on the average greater than in previous years. 
he author mentioned that the United States Government has 
arranged for daily simultaneous observations at two heights in 
the case of a number of stations, the kite being used for the 
high-level observations. The results are not quite satisfactory, 
because kites could not be sent up on some days ; it is suggested 
‘that on such occasions a captive balloon be employed. Prof. 
Thomson hoped that the variation of atmospheric electric poten- 
tial would be investigated by means of kites. Prof. G. H. 
Darwin regretted that on account of the non-existence of a 
‘Government meteorological observatory, this country is very 
backward in the adoption of recent methods of meteorological 
research. Ina subsequent paper Mr. Rotch gave an account of 
the first crossing the Channel by a balloon, by Dr. Jeffries and M. 
Blanchard in January 1785. The former was a Harvard graduate 
in medicine, who settled in London, and the latter a French pro- 
fessional aéronaut. The expedition was of a scientific character. 
A description of the hydro-aérograph, an apparatus invented 
by Mr. F. Napier Denison for registering small fluctuations of 
level of the American lakes and simultaneous small changes 
of air-pressure, was read by Mr. W. N. Shaw. The ap- 
paratus is designed to study more minutely an observed effect of 
barometric changes on the surfaces of the great American lakes. 
The Ben Nevis committee presented the usual summary of 
their records, and stated that the conclusions arrived at last 
year with reference to the effects of approaching cyclones and 
anti-cyclones on the two observatories are supported by the 
examination of later records. The committee on meteoro- 
logical photography reported having obtained photographs of 
some rare forms of cloud and some studies of lightning 
flashes; the structure of thunderclouds appears to resemble 
‘two parallel discs of cloud, with lightning flashes passing be- 
‘tween them or from one face to the other of either cloud. 
NO. 1563, VOL. 60] 
On Tuesday, Prof. Threlfall described a portable gravity 
balance, designed by Prof. Pollock and himself, for the 
measurement of small differences in the intensity of gravity 
from place to place. It consists of a light wire attached near 
one end to the centre of a horizontally stretched and twisted 
quartz fibre, the moment of the weight of the wire just 
balancing the torsional moment of the fibre. The wire is 
only just in stable equilibrium, and the torsion of the fibre 
is noted when the wire is adjusted to coincide with the axis 
of a microscope carried on the frame of the apparatus. The 
instrument can now be relied upon to rT part in 500,000, but 
the accuracy of single readings is greater than this. It has 
been severely tested by much travelling on the Australian coast. 
The committee on electric standards reported that Profs. 
Ayrton and J. V. Jones have now completed the plans and 
specifications for the ampere balance to be used in constructing 
an ampere standard. The committee will consider the pro- 
posals of Prof. Callendar for the construction of a standard 
platinum thermometer in terms of which all other platinum 
thermometers can be compared. The report contains the results 
of a determination of the coefficient of expansion of. porcelain, 
by Mr. T. G. Bedford, which was undertaken in order to com- 
pare the scales of temperature and platinum thermometers of air. 
Prof. Callendar opened a discussion on platinum thermo- 
metry, in which he advocated the adoption of the variation of 
resistance of platinum as a basis for a practical scale of temper- 
ature. _He suggested the construction of a standard thermo- 
meter from a particular sample of platinum wire, and the use of 
a parabolic difference formula for the determination of temper- 
ature by its means. The difference-coefficient may be obtained 
by using as a secondary fixed point the boiling point of sulphur 
(444°53° C. at normal pressure). Dr. J. A. Harker described 
the method used, and Dr. Chappuis the results obtained, in a 
comparison of platinum and nitrogen thermometers at the 
International Bureau of Weights and Measures at Sévres. The 
results agree fairly well with those of Callendar and Griffiths in 
the comparison of the air and platinum thermometers. In the 
discussion Mr, E. H. Griffiths advocated the use of the platinum 
thermometer on the ground that only three readings are 
necessary in order to standardise any instrument. Prof. Carey 
Foster was of opinion that the electrical method would furnish 
a good intermediate standard ; for absolute values, however, the 
gas thermometer must be used, because there is no theory of 
the variation of electrical resistance with temperature and only 
an empirical knowledge of it. Prof. Burstall described experi- 
ments supporting the proposals of Prof. Callendar, Principal 
Glazebrook thought that, before taking platinum as a 
standard, experiments should be undertaken to ascertain 
whether it is superior to other metals, for instance gold. 
Dr. Chree said that some platinum thermometers purchased 
by the Kew Observatory had exhibited curious tricks, and 
were far from satisfactory, because the reasons for departure 
from accuracy were numerous and not always discoverable. In 
the case of mercury thermometers the zero certainly alters, but 
the change has a known cause, and can be allowed for. Prof. 
Threlfall remarked that for rapid and accurate work the 
platinum thermometer alone could be used ; the enormous heat- 
capacity of a mercury thermometer rendering it quite unservice- 
able. Mr. W. N. Shaw thought the thermo-electric couple 
methods, upon which the Germans are concentrating their 
attention, ought to be compared with the platinum thermometer 
before deciding upon a standard. In reply, Prof. Callendar said 
that methods based on the use of a thermo-electric couple are not 
sensitive at low temperatures. 
On Wednesday, Dr. L. A. Bauer described the arrangements 
made by the United States Coast and Geodetic Survey for the 
proposed magnetic survey of the United States and Alaska, and 
expressed a hope that the Canadian Government would consider 
the possibility of a simultaneous survey of Canada. Dr. Bauer 
also described the results of a magnetic survey of Maryland. 
Dr. E. P. Lewis, in a paper on the spectral sensitiveness of 
mercury vapour in an atmosphere of hydrogen, described the 
appearance and intensity of the spectrum of a mixture of 
hydrogen and vapour of mercury in varying proportions. Mr. J. 
Gifford, who has measured the angles of prisms of quartz and 
calcite, and the corresponding minimum deviations for the mean 
of the sodium lines, at various temperatures, gave an account of 
the variation of refractive index with temperature in these cases. 
The proceedings of the Section closed with votes of thanks 
to the president and secretaries, proposed by Prof. Poreyte and 
seconded by Prof. Reinold. 
