; written as that in the present number, they should 
_ prove of considerable value to those who need an intro 
} 
SEPTEMBER 28, 1916] 
duction to the subject. 
From the ‘reports of the behaviour of the recording 
instruments at a number of magnetic observatories in 
different parts of the world during the solar eclipse 
of August 21, 1914, Dr. Bauer and Mr. Fisk, of the 
Department of Terrestrial Magnetism, Washington, 
have drawn some preliminary conclusions as to the 
_ effects of eclipses on solar terrestrial magnetism, which 
will be found in the June number of Terrestrial Mag- 
netism and Atmospheric Electricity. At stations. from 
which the eclipse was visible it appears to have 
changed slightly the daily march of the declination 
needle. At four British and Danish stations for 
which curves of the daily change of declination are 
given the normal motion of the needle to the west 
was arrested, and in some cases reversed, a short 
time before totality of the eclipse. Outside the region 
of visibility of the eclipse na magnetic effects were 
observed. These results appear to justifv more ex- 
tensive preparations for observing the effects of the 
solar eclipse due June 8, 1918. 
Messrs. Kopak, Limirep, have issued a new and 
much improved edition of their ‘Wratten Light 
Filters"’ (1s.), in which they describe some ninety 
colour screens. Of those previously catalogued eleven 
are omitted and twenty-nine new filters are introduced, 
the latter including a series of nine made to equalise 
the tints of various artificial lights for facilitating 
photometric work. The transmissions of nearly all 
the filters are given in very clearly expressed curves, 
a vast improvement on the reproductions of spectro- 
graphs taken with a graduating wedge in front of 
the slit, as given in the previous editions. For those 
who need more exact data the actual readings ob- 
tained by the use of the spectrophotometer are given 
in copious tables, and will prove of great value. 
“The Photography of Coloured Objects,’’ another of 
Messrs. Kodak’s publications, has been revised, and 
now includes “ Orthochromatice Filters,’ which was 
until now published separately. For the benefit of any 
who do not know this volume, we may say that it gives 
a clear and accurate account of the principles involved, 
and points out objects of many kinds that are really 
“coloured,” though they do not appear to be. 
OUR ASTRONOMICAL COLUMN. 
Encke’s Comet.—Prof. Strémgren_ reports that 
Encke’s comet was observed by Dr. Max Wolf on 
September 22. At gh. 41-5m., K6nigstuhl mean time, 
its position was R.A. 22h. 28m. 39s., declination 
7° 8 5"S. The magnitude of the comet was 16:5. 
Tue Nesura Hu. 78 Leonis.—It is interesting 
to note that Mrs. Isaac Roberts is continuing her 
detailed studies of nebulz photographed at Crow- 
borough by the late Dr. Isaac Roberts. The subject 
of a recent paper (Monthly Notices R.A.S., vol. Ixxvi., 
p. 647) is the nebula Hu. 78 Leonis (N.G.C. 3367), 
photographed in 1902. The nebula extends for about 
2/ from north to south, and 2:5’ in the direction at 
right angles, and is described as a left-hand spiral 
with a bright stellar nucleus. The nucleus is encircled 
twice by the spiral arm, which shows numerous con- 
densations. With the aid of the Roberts ‘ panto- 
graver,’’ measures were made of many of the bright 
nebulous knots, and of nineteen stars which appear 
in the neighbourhood of the nebula. All the measured 
objects are clearly indicated in a key chart, and the 
tabulated data will doubtless be of considerable value 
in subsequent investigations of relative motions within 
the nebula. } 
NO. 2448, VoL. 98] 
NATURE 
77 
PnHoroGraPus or Mars.—In the September number 
of the Observatory an account of a minute examina- 
tion of photographs of Mars taken at Flagstaff by Dr. 
Lowell and his co-workers is given by G. H. Hamilton? 
The photographs were studied without reference to 
maps of the planet, and details common to three or 
more of the images, of which there were sometimes 
as many as four dozen on a single plate, were inserted 
in sketches. Subsequent comparisons in all cases 
showed a very close agreement with the accepted maps 
in the observatory. One of the sketches, from photo- 
graphs taken on March 15 of the present year, is 
reproduced, and shows an abundance of detail, includ- 
ing numerous canals. Mr. Hamilton is of opinion that 
the linear character of the canals, as represented by 
Dr. Lowell, is completely confirmed by the photo- 
graphs. By the use of a finely divided transparent 
scale, it was found possible to obtain satisfactory 
measurements of the positions of the principal mark- 
ings, due allowance being made for halation. 
SPECTRUM OF THE NesBuLA H rv. 39 ARGUs.—An account 
of the spectrum of Hiv. 39 Argds (N.G.C. 2438) has 
been given by Dr. Max Wolf (Sits. Heidelberg Akad. d. 
Wiss., March, 1916). The spectrum was photographed 
at the Konigstuhl Observatory, Heidelberg, on Febru- 
ary 20, with an exposure of five hours. The nebula 
is very faint, and direct photographs show it to be of 
annular form with an eccentrically situated stellar 
nucleus; the eastern side of the ring is the brighter, 
and the nucleus lies nearer the western edge. The 
spectrum is almost identical with that of the ring 
nebula in Lyra, but much fainter. In order of bright- 
ness the lines are A 373,387,434 (Hy), 469, 501, and 
397; there is possibly also a faint line at 352. As in 
the Lyra nebula, a distribution of the different gases 
in layers is indicated by the varying distances to which 
the lines extend. The line 373 reaches furthest out- 
wards, but has a marked minimum in the interior of 
the ring. The lines 387 and 434 reach further towards 
the centre; and, in striking contrast with the other 
lines, 469 (i.e. 4686, of ‘‘proto-helium”’) is brightest 
within the ring, and extends only a small distance 
from the nucleus. 
THE UNITED STATES NATIONAL 
RESEARCH COUNCIL. 
Vo account of the inauguration and organisation of 
the National Research Council of the United States 
was published in our issue of August 3 last (vol. xcvii., 
p- 465), and the article pointed out that from the 
cordial interest shown by all who had learnt of the 
work in its early stages, it was evident that so soon 
as a widespread request for co-operation could be 
extended it would meet with general acceptance. A 
preliminary report of the Organising Committee to 
the president of the U.S. National Academy of 
Sciences, published in the August issue of its Proceed- 
ings, shows that this expectation has been justified, 
and some of the first instances of co-operation are 
given. Prof. G. E. Hale, chairman of the committee, 
has also sent to the New York Times an account of what 
is being done in the United States to mobilise science 
for industrial progress and military efficiency, and 
we reprint his letter below. It will be seen that 
the president of the Throop College ‘of Tech- 
nology in Pasadena, California, an institution which 
gives special attention to research, hearing of the plans 
of the Research Council, offered the assistance and 
co-operation of the recently endowed research labora- 
tory of chemistry, and secured at once an additional 
endowment of 20,0001. for scientific research. In 
somewhat similar circumstances a gift of t100,000!. 
