AUGUST 22, 1912] 
NATURE 
643 
Two. patterns of conveniently mounted lenses have 
been put on the market by the Third Hand Patents, 
Ltd., of 361 and 363, City Road, London, E.C. Each 
consists of a lens mounted on a clip for clasping the 
left thumb, and so leaving the hands free to mani- 
pulate specimens under examination. Lenses of almost 
any power required in a simple magnifier can be pro- 
vided. A high-power lens with German silver fittings 
and universal joint costs 6s., and a low-power lens 
with imitation tortoiseshell rim may be purchased for 
2s. These simple microscopes may be recommended 
to teachers of nature-study for the use of their pupils 
when examining natural objects. 
Tue Journal de Physique for July contains an 
article by MM. Reboul and Grégoire de Bollemont 
on the distintegration of metals at high temperatures, 
in which a theory of the process is suggested which 
seems to cover the known facts satisfactorily. Their 
own experiments were made in an electric furnace 
which could be heated to 1200° C. A thin sheet of 
copper or silver in the form of a cross was attached 
to a sheet of platinum, the two sheets being parallel 
and about a millimetre apart. Without opening the 
furnace, the two could be moved from the cold to the 
hot part of the furnace, remain there a known time, 
and be again brought to the cold part. If certain 
conditions were satisfied, on subsequent examination 
the platinum sheet was found to have on it a thin 
film of copper or silver in the form of a cross. The 
authors ascribe the effect to the direct projection of 
metallic particles from one sheet to the other, owing 
to the explosion of minute pockets of occluded gases 
in the copper or silver sheets near their surfaces. 
They have already suggested an explanation of the 
emission of positive charges of electricity by heated 
metals based on the same theory. 
CoMMENTING on the Charlestown curve derailment 
which occurred on June 21, The Engineer for August 16 
finds itself unable to agree with Colonel Druitt’s con- 
clusion that radial tank engines are unsuitable, and 
quotes the case of the Lancashire and Yorkshire Rail- 
way; which has at present 330 of these locomotives in 
service. The reputation of these locomotives is that 
they are extremely easy on the road, and consequently 
on themselves, the flanges of the wheels keeping 
wonderfully. round after running thousands of miles. 
Our contemporary has no hesitation in accepting 
Colonel Druitt’s recommendations as to speed restric- 
tions, also regarding the difficulty which drivers ex- 
perience in judging speeds when running on good 
roads and down steep gradients. The use of speed 
recorders is suggested in the report, and to this no 
objection can possibly be taken. Seeing the very 
extensive use made of such instruments on the Con- 
tinental railways, it is somewhat surprising that these 
are not more employed in this country. 
Tue last of a series of articles descriptive of the 
Fried. Krupp establishments at Essen appears in 
Engineering for August 16. It is of special interest 
to note the admirable equipment for works tests. 
Each department has its own “private ”’ testing plant 
in order to enable the engineers and metallurgists in 
charge to ascertain at any moment, for their own 
private guidance, the way in which the various pro- 
NO. 2234, VOL. 89] 
| equal in any part of the world. 
cesses are being carried out. Our contemporary states 
that the chemical and physical laboratory has not its 
This is a five-storey 
building covering an area of 39,000 sq. ft. The 
chemical laboratories are most completely equipped for 
the analysis of steel, other metals and alloys, ores, 
gases, water and so forth, for testing oils, gunpowders, 
and all products made and used throughout the estab- 
lishments. The physical research department is admir- 
ably equipped for metallographical research work and 
all classes of physical tests. A number of rooms 
on the lower floor are set apart for manufacturing all 
the different glass bottles, tubes, and connections used 
in the chemical laboratory for analytical purposes, the 
plant containing the necessary compressed-air piping 
and the glass-annealing stoves. 
A very useful little handbook for students who 
wish to use the reading-room at the British Museum 
has been written by Mr. R. A. Peddie, and published 
by Messrs. Grafton and Co., 69 Great Russell Street, 
London, at the price of 1s. net. The book gives full 
| information as to the conditions of admission to the 
reading-room, the various catalogues, and so on. 
OUR ASTRONOMICAL COLUMN. 
Cotour PHoToOGRAPHY OF THE Moon.—Another of 
Prof. Wood’s interesting papers on the photography 
of the lunar surface, using different selected portions 
of the spectrum, appears in No. 1, vol. xxxvi., of 
The Astrophysical Journal. 
With a nickel-coated mirror of 16 in. aperture, 
prepared as described in his previous paper, Prof. 
Wood secured three photographs, one using the visual 
region of the spectrum, one the violet, and the third 
the ultra-violet, and on these the different features of 
the lunar surface show very marked differences of 
brightness. For example, a patch just above the 
crater Aristarchus is as bright as the surrounding 
surface when the ‘‘visual”’ region is employed, comes 
out rather darker on the ‘violet’? image, and is quite 
dark when photographed in the “ultra-violet” light. 
On the other hand, many of the maria come out 
relatively darker in the violet picture, and appear to 
be differentiated inter se by this selective process. 
Prof. Wood makes the interesting suggestion that, 
could pictures be taken over a greater range of 
different wave-lengths, it would become possible to 
take up the subject of lunar petrography. For 
example, a series of experiments led him to the con- 
clusion that the dark patch near Aristarchus is covered 
| by a form of sulphur or some sulphur compound. 
If it were possible to extend the range of the photo- 
graphs to, say, 8x, where the silicates begin to show 
anomalies in reflecting power, one might be able to 
map out, petrographically, the lunar surface. 
A three-colour lantern slide, made by Mr. Ives from 
the three negatives, showed the general surface of 
the moon to be olive-green, but certain spots came 
out with an orange tone, while others were decidedly 
purple. The spot near Aristarchus appeared of a 
deep-blue colour, as was to be expected. 
The subject is obviously one of great importance 
and capable of considerable extension in celestial 
photography, and Prof. Wood’s detailed description 
of his numerous experiments, colour-filters, and photo- 
graphs will be found of immense assistance by others 
who may take up the work. Moreover, he offers to 
render any help he can and to lend his silvered plates 
of uviol glass, which he uses as screens, to any 
observatory ready to use them. 
