Jury 9, 1914] 
NATURE 
Ne eee ee 
of the trustworthiness of the method of age-determina- 
tion by means of scales. 
VoL. exxiii. of the Sitzungsberichte of the Vienna 
Academy of Sciences contains a paper presented on: 
March 26 by Dr. J. v. Hann on the daily range of 
meteorological elements at the Panama Canal, based 
on hourly or two-hourly. observations. made at 
several stations. The harmonic analysis of 
the data (pressure, temperature, and humidity) is 
preceded by tables of monthly and yearly means. The 
latter show that the highest mean temperature and 
lowest relative humidity occur in’ March and April, 
and the lowest temperature in November. From May 
to October the humidity is uniformly high, and 
especially so from January to April, while Colon. (on 
the Atlantic coast) is much damper. Rainfall in- 
creases from the Pacific to the Atlantic shore, January 
to March being very dry. The wettest months on the 
Pacific slope are May, October, and November; on 
the Atlantic coast July and October are wettest. With- 
out entering into detail here respecting the results of 
the laborious calculations entailed in computing the 
harmonic constituents, we may note that both the 
whole-day and half-day periods show that an increase 
of 10° C. in temperature corresponds to a decrease of 
about 36 per cent. in the relative humidity. Dr. v. 
Hann remarks that this relation between the two 
elements is exceedingly regular. 
Messrs. ISENTHAL AND Co. have produced an im- 
proved type of electrolytic rectifier. The older forms 
of the aluminium rectifier or ‘“‘valve”’ for converting 
alternating into continuous current were never very 
popular; trouble was experienced due to heating of the 
electrolyte, and the arrangement of the four cells, 
usually of glass, necessary for rectifying both half- 
waves of the alternating current, was not always a 
convenient one. In the new design the electrodes, 
which are in the form of grids protected from action 
of the electrolyte at the surface level of the liquid, are 
placed in a solid seamless steel tank, instead of in 
four separate glass vessels. The trouble due to tem- 
perature rise appears to have been overcome, and the 
whole apparatus is in a compact and workmanlike 
form. 
Tue Board of Trade has now issued a report on the 
new sight tests used in the Mercantile Marine. This 
report covers the period of April 1 to December 31, 
1913. An improved wool test in which the candidate 
has to match five colours, and a lantern test, were 
used. The cases of colour-blindness are divided into 
those definitely rejected by the local examiners and 
those referred for a special examination, the local 
examiner being doubtful. Of the 286 definitely 
rejected in the local examination 148 failed in both 
the lantern and the wool test, and 138 failed in the 
lantern test only; there was no failure with the wool 
test which passed the lantern test. Of the 286, 93 
appealed, 26 being successful. Of 125 referred cases, 
20 were referred on both the lantern and wools, 1o1 
on the lantern only, three on the wools only, and one 
on form vision as well. Of this number there were 
thirty failures; three of these were referred on both 
NO. 2332, VOL. 93] 
| vibration galvanometers. 
the lantern and wool test, twenty-six on the lantern 
only, and one on form vision as well. Those referred 
on the wool test alone were passed. 
In the April number of Le Radium, which has just 
reached us, Dr. C. Ramsauer, of the Radiographic 
Institute of the University of Heidelberg, describes a 
simple method of determining the amounts of radium, 
thorium, and actinium present in materials, even when 
the amounts are very small. The method consists in 
heating the materials to 1150° C, for four minutes, so 
as to drive out the radio-active emanations accumu- 
lated in the material, condensing it on a cold surface, 
and then studying the decay of activity of the material 
condensed. By a comparison of the decay curve with 
the decay curves obtained in the same way from the 
three radio-active substances separately, he finds he 
can deduce the quantities of the three present in the 
material tested with an accuracy of about 20 per cent. 
A test of the Kreuznach waters by this method led to 
a result in agreement with that previously obtained 
by the more accurate method of Becker which, how- 
ever, determines the radium content only. 
THE June number of the Proceedings of the Physical 
Society of London contains several papers of excep- 
tional interest. In the first instance, there is the 
Guthrie lecture by Prof. R. W. Wood, on his recent 
work on resonance spectra, which he hopes will do 
something towards unlocking the secret of molecular 
radiation. This lecture, which is the first given, is 
' very suitably introduced by a historical note from Prof. 
G. C. Foster relating to Prof. Guthrie, to whom the 
Physical Society owes its foundation. A second paper, 
by Dr. J. G. Gray, describes a number of new gyro- 
static devices for manoeuvring and stabilising a variety 
of moving bodies from torpedoes to airships. This 
paper is well illustrated. Mr. W. R. Bower shows 
that the problem of the rainbow may be treated by 
geometrical methods with great advantage, and Mr. 
S. Butterworth describes a zero method of testing 
In two papers on radio- 
active problems, Messrs. T. Barratt and A. B. Wood 
| furnish grounds for the belief that thorium-C. consists 
of two substances, one giving the o and the other the 
B radiation, and Messrs. H. P. Walmsley ‘and  W. 
Makower show that the path of an a particle projected 
along a photographic plate is visible on development, 
and may be used to study the scattering of the par- 
ticles by matter. Shits 
A PAPER dealing with the design of floats for hydro- 
aeroplanes has been issued from the recently reopened 
Langley Aerodynamical Laboratory, and relates to 
experiments carried out on models in the naval tank 
at Washington. The results confirm those obtained 
elsewhere, and show that the float requiring least 
power for leaving the water is one with a V-shaped 
bow. Such a bow sends up a remarkable sheet of 
| water which must be turned down again by the 
shoulder of the float if the best results are to be 
obtained. All the experiments were carried out with 
floats having a single step, and it is stated that the 
| step should be well ventilated; air was allowed access 
