JuLy 25, 1912] 
NATURE 
546 
may be produced by a moderately. bold sea front—a 
condition which is utilised commonly in the coastal 
navigation of the North Pacific—moderation of speed 
and careful.soundings give practical security in most 
cases. Prof Barnes, of McGill University, has 
recently demonstrated the - possibility of detect- 
ing the presence of icebergs near a_ ship 
by means of sensitive recording thermometers, 
and has exhibited automatically constructed  dia- 
grams which confirm the trustworthiness of his 
methods. The use of submarine bells in connection 
with lighthouses and lightships, and the fitting of 
microphonic receivers. in Transatlantic passenger 
steamships and warships during the last eight or nine 
years, have also become common; and experience has | 
proved this system to be of great value both for pick- 
ing up lighthouses, lightships, and buoys, and for 
detecting the close approach of ships to one another 
in fog. On the whole, therefore, the openings for the 
additional apparatus suggested by Sir Hiram Maxim 
do not seem -to be numerous or promising, nor is his | 
statement of existing conditions complete. 
matters stand, the officers of steamships have very 
onerous duties to perform, and unless additional 
apparatus is shown to be required in order to gain 
increased safety, it is not probable that shipowners 
or ship captains will favour its introduction, since that 
action would enlarge the labours of officers whose time 
and thought are already fully occupied in meeting 
grave responsibilities. W. H. W. 
RESEARCHES AT THE VIENNA RADIUM 
INSTITUTE. 
‘THE Mitteilungen aus dem Institute fiir Radium- 
forschung, 12-17, deal with a variety of subjects 
of radio-active interest. Dr. Przibram describes a 
method for visualising and projecting on a screen the 
range of a-rays, depending upon the principle that a 
cloud of ammonium chloride fumes in an electric field 
rapidly clears when exposed to arays. The cloud is 
formed between the parallel plates of a condenser, at 
one end of which is the preparation giving oa-rays. 
On applying a field of 200 volts between the plates 
the cloud in the vicinity of the preparation clears, 
leaving a perfectly sharp dividing line marking the 
extreme limit of the range of the e-rays. 
Prof. Meyer and V. F. Hess discuss the heat effect 
of Honigschmid’s standard radium preparations, which | 
they evaluate at 138 calories per hour per gram of 
element, all three types of rays being completely 
absorbed, and numerous other data relating to these 
preparations. They include an interesting effect pro- 
duced by one gram of radium after two years on a 
tube of fused quartz, which splintered and became 
quite rough on its inner surface, showing that this 
material is unsuitable for the storing of radium. 
L. Flamm and H. Mache deal with the quantitative 
measurement of the radium emanation in a guard-ring 
plate condenser, with varying distances between the 
plates, and compare the values obtained with those 
calculated by various methods. Przibram also dis- 
cusses the phosphorus content of the charged particles 
of phosphorus clouds. Of interest to the physiological 
chemist is a paper by Knaffl-Lenz and Wiechowski, 
calling in question the action of the radium emanation 
and of air exposed to o-rays in decomposing sodium 
mono-urate into easily soluble substances, and giving | 
the negative results of many experiments. 
Finally, a botanical paper on the sprouting of plants 
under the action of radium is contributed by Molisch, 
and is accompanied by plates. which recall those illus- 
trating the action of fertilisers. Shoots of Syringa 
vulgaris and Aesculus Hippocastanum are depicted 
NO. 2230, VOL. 89] 
As | 
showing those which have been subjected to the action 
of radium rays and of the radium emanation, and 
which, like Aaron’s rod, have sprouted, while those 
not so treated have not. The action of the radium 
must not be overdone, or the plants are killed, and 
it is only of effect if applied during the rest period 
of winter in the end of November or in December. 
In addition to the varieties mentioned three others 
showed . positive and -four others negative results. 
Naturally the radium emanation, applied to the 
plant under a bell-jar, gives better and more pro- 
nounced results than the direct radiation. Base 
EXPERIMENTAL RESEARCH IN 
AERONAUTICS. 
Experiments on Airship Models.—During the past 
year further experiments have been made on the re- 
sistance of airship models, and on the forces and 
moments acting on inclined models of different forms. 
The resistance measurements included some tests of 
special shapes, made at the request of the super- 
intendent of the Royal Aircraft Factory; and an in- 
vestigation to determine the effect of bluntness of tail 
on the relative air flow and on the resistance. From 
visual observations and photographs of the flow past 
models in the small water channel, made with the 
aid of coloured streams, it was noted that the flow 
in the tail region even of an elongated model was 
very slow. It was inferred that truncation or modi- 
fication of the tail within this ‘“‘dead”’ region should 
have little effect on the head resistance. A model was 
accordingly made in which successive sections of the 
‘tail were removable, and it was found, as expected, 
that the effect of the removal of portions of the tail 
within the ‘‘dead”’ region was negligibly small. . In 
the model tested, the full length of tail was about 
twice the maximum diameter, and it was found that 
a length of o’8 of the diameter, from the tip, could 
be removed without appreciable effect on the head 
resistance. It follows, therefore, that within this 
region the tail may be rounded off or otherwise 
modified without loss of speed; a gain in lifting power 
is thereby secured, while the less pointed form pre- 
sents advantages from the constructional point of 
view. 
In addition to the model experiments above de- 
scribed, an interesting series of determinations of the 
head resistance of eight different airship forms was 
carried out at the Royal Aircraft Factory. These 
models were made of goldbeaters’ skin, and were 
about 18 ft. in length, and 3 ft. in diameter. The 
method employed was to tow the models horizontally 
through the air at different velocities, the speed being 
maintained by means of a falling weight. The con- 
clusions arrived at from these experiments were gener- 
ally in accordance with those deduced from the 
measurements made on small models of the same 
forms in the water channel at the National Physical 
Laboratory. From the point of view of total balloon 
resistance alone, a fineness ratio, or ratio of length 
to maximum diameter, of 6} to 1 was found to be 
most efficient; but taking into account the other re- 
sistances in the completed airship, it was concluded 
that it might be desirable to reduce the fineness ratio 
to about 51 to r. 
The difficulties. of obtaining results of high accuracy 
by the method of towing light models of this char- 
acter through the air are very great, but nevertheless 
a comparison of the measurements of head resistance 
thus made on models of 3 ft. diameter, with those 
1 From the Report:of the Advisory Committee for Aéronautics for the 
Year rgrt-r2.. (London: Wyman ard Sons, I td.) [Cd. 6249.] » Price 2d. 
