Jot e tas 
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2 J ANUARY 6, 1923] 
NATURE 
29 

is only about one-sixteenth of the price of the Indian 
screen hitherto used. Much valuable data on the 
vee wind currents have been recently published 
and other upper air data are ready for publication. 
Considerable demand is being made for upper air 
results over India and the report regrets the inability 
to do all that is required for want of funds. In the 
British Isles the staff of workers has been immensely 
increased and without doubt considerable increase 
of the staff in India will have to be faced, although 
it will mean added expense. A 08 showing the 
growth in activity and cost for the last 15 years is 
given at the end of the report. For want of funds 
much useful work has en discontinued. The 
stations over India from which detailed observations 
are received now number 281, and these have to be 
supplied with instruments and inspected periodically. 
ce) ations are secured from vessels by wireless, 
as well as from the ordinary logs, over the neighbour- 
ing seas. Seismological observations are recorded 
at several stations and the data are supplied to the 
British Association. For rainfall over India, there 
are now 2928 stations from which observations are 
received, 
THe NEw Fiicut Compass.—The United States 
Air Service has set itself the task of putting the 
navigation of the air on as trustworthy a basis as 
that of water, and as part of its programme has asked 
the Bureau of Standards to investigate the possibilities 
of the earth inductor type of compass. As a result, 
a form of instrument has been devised which has 
proved more satisfactory than any previously in use in 
the Air Service. A memoir describing the instrument 
was presented in 1921 to the American Philosophical 
Society by Messrs. P. R. Heyl and L. J. Briggs, and 
was awarded the Magellanic premium. It is now 
i in part 1 of volume 41 of the Proceedings 
the Society. An armature driven about a vertical 
axis by a cup propeller has four carbon brushes set 
at right angles to each other in contact with its 
commutator, and capable of being set so that when 
the aeroplane is flying in a fixed direction, one pair 
of brushes gives a maximum and the other pair zero 
electromotive force. The two pairs of brushes are 
_ connected to four equally spaced points of a closed 
electric circuit and a pointer galvanometer connected 
to two points opposite each other on the circuit. The 
diameter for which the galvanometer gives zero 
= is determined by the course of the aero- 
plane. 
BurninG HEAvy FuEt-ort.—Some of the technical 
difficulties encountered in burning heavy fuel-oil in 
Diesel engines and other types of heavy-oil engines 
were discussed by Mr. Harold Moore in a paper read 
by him at the North-East Coast Institution of 
Engineers and Shipbuilders, “Newcastle, early in 
December. Ignition trouble, difficulties in burning 
oil after ignition has taken place, and the problems 
raised by the presence of small quantities of im- 
purities, were the main factors dealt with as affecting 
the utilisation of heavy fuel. With regard to ignition 
trouble, a great deal depends on the range of ignition 
temperatures Bea 3 with varying types of oil-fuel ; 
in Diesel and cold-starting engines, ignition takes 
place when the heat of compression exceeds the 
spontaneous ignition temperature of the oil, and it is 
customary to adjust the compression so as to ensure 
regular ignition of whatever class of fuel is burnt. 
The utilisation of various petroleum and coal-tar oils 
necessitates repeated adjustments being made, and 
these, under changing conditions of low and high load 
running, atmosphere, etc., have to be considered 
carefully both theoretically and practically. Pilot 
NO. 2775, VOL. r11 | 
ignition gears, which to a large extent overcome initial 
difficulties of firing, are now installed on most Diesel 
and cold-starting engines. After ignition has taken 
place, the smooth burning of the oil depends primarily 
on its complete combustion before the exhaust valve 
opens, and on the rate of burning and influence of the 
various substances in the fuel. Such substances 
include the bituminous bodies present in petroleum, 
hard and soft asphaltum, waxes, and in the case of 
coal-tar oils (more often employed on the continent 
than in this ae naphthalene and anthracine. 
Finally the effects of water, sand, and iron rust, the 
commonest impurities in oil-fuel, constitute not un- 
important factors to be reckoned with. Such 
impurities are best removed by the employment of 
high-speed centrifuges. 
MAGNETIC OBSERVATIONS AT Batavia. — Volume 
40 of the Observations made at the Royal Magnetical 
and Meteorological Observatory at Batavia contains 
the observations of the year 1917. The preface, 
however, brings the history of the observatory 
down to February 1922. From it we learn of the 
retirement of the well-known director, Dr. W. van 
Bemmelen, who has been succeeded by Dr. Braak. 
In addition to the usual meteorological tables, the 
publication contains some special results of interest, 
including the results of a 7-year comparison of 
ordinary thermometers in the thermometer shed and 
ventilated Assmann thermometers outside. The dif- 
ferences are substantial. The magnetic results are 
very complete, two magnetographs being in constant 
operation. The tables of hourly values refer to three 
rectangular components of force, the horizontal com- 
ponents being in and perpendicular to the astronomical 
meridian, which is there nearly coincident with the 
magnetic. An interesting chart shows the departures 
of the three rectangular components from their mean 
yearly values. These departures are calculated for 
th., 7 h., 13 h., and 19 h. G.M.T. of every day, the 
value assigned to each hour being a mean from 24 
hours centering at that hour. The great predomin- 
ance of disturbance in the north-south component is 
effectively shown. 
PHOTOGRAPHIC SENSITISERS AND DESENSITISERS.— 
Prof. Rudolfo Namias describes some of his remark- 
able experiences with these reagents in ‘‘ The Process 
Year-Book,”’ vol. xxv., 1923. He agrees with Dr. 
Luppo Cramer that pinaflavol, the most recently 
introduced colour sensitiser, is unique in its property 
of sensitising for the well-known gap in the greenish- 
blue, and that it and pinacyanol give a “‘ very high 
increase of general sensitiveness.’’ He finds that 
pinacyanol may be used in a solution fifty times 
diluted as compared with the concentration generally 
advised (finally equal to one part of solid in five 
millions) and that the spectrographic tests show 
that this enormous dilution makes no difference in 
its effect. He has discovered that desensitisers are 
more important than they were at first thought to 
be. By getting rid of the sensitiveness of the plate 
they avoid the formation of the development fog 
always produced when development is continued to 
bring out the weak detail which, however, is generally 
buried by it. By making this detail available we 
get a practical increase of sensitiveness, though the 
advantage is restricted, so far as is known, to the 
use of safranine, and of hydroquinone and alkaline 
bromide in the developer. The increase of general 
sensitiveness and the elimination of development 
fog enable one to use slow plates with their much 
finer grain, and so, without the practical sacrifice of 
sensitiveness, to get a considerable gain in resolving 
power. 
