424 
mining and ordinary machinery points of view, are not 
fitted to examine and overhaul electrical plant. The ques- 
cc ” 
tion arises as to what constitutes a ‘‘ competent person 
within the meaning of the Mines Act (Rule 11), and the 
sooner this is made quite clear and insisted upon the better 
it will be for all concerned in electrical mining work. In 
the present case, the engineer of the colliery and the ‘‘ over- 
man ”’ were entrusted with the machinery in question, and 
the evidence proves clearly that they were only expected 
to see that outside and surface connections were all right, 
and also to open up switch boxes, but any internal faults 
and so on were not considered to be within their re- 
Colliery managers must be made to realise 
that technically trained men should be employed to under- 
take electrical work in the colliery, and until they do so 
accidents are bound to occur—the only wonder being that 
they are not more frequent. 
sponsibility. 
Pror. R. W. Woop has sent us a description of a 
series of interesting experiments he has made in the 
direction of the optical intensification of paintings. Onc 
of the difficulties an artist has to contend with in depicting 
scenes in which great contrasts of luminosity occur is the 
narrow range of luminosity obtainable on canvas with 
pigments. Aubert states that the whitest paper is but 
fifty-seven times as luminous as the blackest, and_ this 
probably represents about the range obtainable in paint- 
ings. The problem is, therefore, how to produce a strong 
illumination on all high lights of the picture and a feeble 
illumination on all the shadows. Prof. Wood has obtained 
good results by taking a photograph of the painting on 
an orthochromatic plate, preferably a red sensitive plate 
with a suitable ray filter. A lantern-slide is then made 
from the negative, and the picture projected in a dark 
room, not on a white screen, but on the original paint- 
ing. Any desired effect can be secured by local reduction 
or intensification of the negative or lantern-slide. If the 
negative itself is projected the painting a most 
curious effect is obtained. The contrast is lessened, and 
if the negative is a dense one the contrast may be almost 
destroyed, making the painting appear a flat wash of 
chocolate. In taking the negative, care must be taken to 
have the painting vertical and the camera lens directly 
in front of the centre of the picture. If after looking for 
a few minutes at a painting illuminated in the way de- 
scribed the lantern-slide is removed and a uniform 
illumination allowed to fall on the picture, it appears as 
if it had not been dusted for ten years; the sunlight 
leaves it, and everything looks flat. Prof. Wood finds 
that the effects are very different according to whether the 
negative is taken on an ordinary or an orthochromatic 
plate, especially if there is much blue in the painting. He 
thinks, too, that if the values are correct in the original 
painting, they will hold under the graded illumination pro- 
duced by the lantern-slide; if they are not right, the errors 
will be glaringly magnified. 
upon 
No. 95 of the Communications from the Physical Labor- 
atory of the University of Leyden contains an account of 
a series of investigations on the measurement of very low 
temperatures carried out under the superintendence of 
Dr. Kamerlingh Onnes, the director of the laboratory. 
Mr. C. A. Crommelin has compared the readings obtained 
by a thermoelement of constantin-steel with those given 
by the hydrogen thermometer. Mr. J. Clay has measured 
the coefficient of expansion of Jena glass and of platinum 
between -+16° C. and —182° G., and compared the 
platinum resistance thermometer with the hydrogen and 
NO. 1948, VOL. 75] 
NATURE 
[ FEBkuUARY 28, 1907 
the gold resistance thermometer, whilst M. C. Braak has 
made a detailed investigation of the hydrogen thermometer 
as a means of measuring low temperatures. 
Tue transformation, which was first observed by Lalle- 
mand in 1870, of orthorhombic sulphur, dissolved in carbon 
disulphide, into a less soluble amorphous variety under 
the influence of light, forms the subject of a paper by 
Mr. G. A. Rankin in the Journal of Physical Chemistry 
(vol. xi., No. 1). The transformation is brought about 
by the violet and ultra-violet rays, and is reversible, the 
conversion of the amorphous form into the orthorhombic 
crystalline variety taking place when it is kept in dark- 
The presence of ammonia or hydrogen sulphide 
accelerates the latter change and tends to prevent pre- 
cipitation from a carbon disulphide solution even in bright 
sunlight. Conditions of equilibrium depending on the 
intensity of the light can be established between the two 
forms of present in solution at a constant 
temperature. 
ness. 
sulphur 
A sEcOND edition of Mr. Mervyn O’Gorman’s ‘* Motor 
Pocket Book ”’ has been published by Messrs. A. Constable 
and Co., Ltd. The book has been revised and enlarged, 
and its price is 7s. 6d. net. 
Tue writer of the article on the ‘“‘ Treatment of Cancer ”” 
in Nature of December 20, 1906, writes to say that he 
was in error in believing that the injections of the pan- 
creatic enzymes have to be made in the neighbourhood of 
the growth (January 10, p. 247). He understands that 
this is not the case, so an objection he raised to the trypsin 
treatment is removed. 
OUR ASTRONOMICAL COLUMN. 
ASTRONOMICAL OCCURRENCES IN MARCH: 
March 1. 11th. 42m. Minimum of Algol (8 Persei). 
s, 14h. Mercury at greatest elongation, 18° 9’ E. 
4. 8h. 31m. Minimum of Algol (8 Persei). 
6. 22h. 26m. Conjunction of Mars with the moon, 
Mars 3° 13'S. 
12. Venus. Illuminated portion of disc =0°639. 
16. 3h. Conjunction of Vesta with the moon, Vesta, 
OnjreNe 
21. 6h. Sun enters Aries, Spring commences. 
» 7h. 16m. to 8h, 30m. Moon occults x! Onionis, 
(mag. 4°7). 
s> 12h, 30m. to 13h. 25m. 
mag. 4°8). : : 
y, 16h. 38m. Conjunction of Jupiter with the moon, 
Jupiter 2° 32’ N. p 
24. 10h. 14m. Minimum of Algol (8 Persei). 
27. 7h. 3m. Minimum of Algol (8 Pevsei). 
A New Form or Ca@tostat TELEScorpE.—One of the 
chief difficulties encountered in the work of the Mount 
Wilson Solar Observatory has been the deformation and 
poor definition of the sun’s image, caused by the distortion 
of the mirrors and by the unsteadiness of the heated 
atmosphere through which the horizontally projected 
beams have to pass when reflected from the ccelostat to) 
the spectroheliograph or spectrograph. 
Prof. Hale now proposes to obviate some of the difficul- 
ties by having the whole instrument vertical, and in No. 1, 
vol. xxv. (January), of the Astrophysical Journal he de- 
scribes and illustrates the form of the proposed instru- 
ment. The ccelostat mirror (diameter 17 inches) is to be 
mounted on a steel tower some 60 feet high in such a 
manner that it can be moved to follow the sun without? 
disturbing its adjustments. A second mirror, elliptical in 
form, will again reflect the beam on to a 12-inch object- 
glass (So feet focal length) mounted directly below it, and 
Moon occults x* Orionis, 
