rd ‘ c be 
ay . aig * 
raed ee er ee 
ight lines were also found in the spot spectrum, and be- 
en C and D some very peculiar shadings terminated 
arply at the less refrangible limit by a hard dark line, 
but fading out gradually in the other direction at a dis- 
tance of three or four of Kirchhoff’s scale divisions. The 
interpretation of such markings is not quite clear, but 
would rather seem to point to such a reduction of tem- 
erature over the spot-nucleus as permits the formation of 
iseous compounds by elements elsewhere dissociated, 
ince these shaded spectra are quite probably charac- 
teristic of non-elementary substances, a view fortified by 
Schuster’s recent beautiful investigations upon the 
‘spectrum of nitrogen. 
_ Many more or less remarkable solar eruptions were ob- 
served, though none on quite so magnificent a scale as 
‘some before recorded. On several occasions velocities of 
from 150 to 200 miles per second in the ejected matter 
were observed by means of the displacement and distor- 
tion of the hydrogen lines, and on one occasion a velocity 
of nearly 250 miles was attained. One of the finest erup- 
tions was visible on the surface of the sun itself in the im- 
mediate neighbourhood of a large spot. 
A careful comparison of some of these observations 
with the corresponding magnetic records at Greenwich 
and Stonyhurst, for copies of which records I am in- 
_ debted to the courtesy of Sir G. B. Airy and Rev. S. J. 
Perry, goes far to show that, although probably the 
greatest magnetic disturbances are due to terrestrial causes, 
or at least are only indirectly results of solar or cosmical 
influences, yet, on the other hand, every solar paroxysm 
does have a distinct, direct, and immediate effect upon 
‘the magnetic elements. Thus on August 3 such solar 
‘paroxysms were noted at 8.45, 10.30, and 11.55, also on 
August 5 from 6.20 to 7.30 A.M. (Sherman time), and the 
last was the only outburst during the day. 
Now the annexed figure (Fig. 1), from a photographic 
copy of the vertical force curve for these days at Green- 
wich, shows marked and characteristic disturbances at 
points indicated, which, allowing for the longitude, 
yrrespond to the very instants when the solar dis- 
turbances were noted. Further comparisons of such 
phenomena will be necessary to establish the conclusion 
ith absolute certainty ; but in the meantime it seems 
altogether probable that every solar disturbance receives 
an immediate response from the earth, and that the 
‘magnetic impulse travels with, sensibly, the velocity of light. 
I must not close without alluding to certain obser- 
vations that enable us to distinguish, to some extent, 
between the substances ejected from the sun, and those 
constituting the atmosphere into which the irruption 
takes place, Certain lines during these outbursts were dis- 
torted and displaced, while others near them, equally 
conspicuous, were wholly unaffected. 
Thus on August 3 and 5, the former class included the 
lines of hydrogen, D,, the lines of sodium, magnesium, 
and many of those of iron; in the latter were K534, 
1474, 1505, 1515, 1528, 1867, 2007 (1870 and 200 were in- 
tensely disturbed), 2581, and probably the two Hs; I 
Say probably, because the observation of these lines was 
too difficult to permit absolute certainty, still I feel very 
confident that they were unaffected. The barium lines 
‘also seldom seemed to participate in any disturbance. 
The obvious moral of our summer’s work seems to me 
this, that no time ought to be lost in occupying points of 
uch advantage with the most powerful instruments : the 
great telescopes now building should be put in a position 
to profit by such atmospheric conditions ‘as will secure 
heir utmost efficiency, for while it is of little consequence 
to science whether ordinary glasses are placed where 
their power will be increased by 25 per cent., it may make 
a difference of years and decades in her advance if the 
new artillery opens its attack upon the heavens from the 
mountain-tops instead of from the plains, 
- Dartmouth College, Noy. 25 GC. A. Youna 
“NATURE 
siti Be ee Mae Poe eon Jatin, Sete “We err, op ee ee ee pre o> OY. R 
fe * > . * ; “ t. B - Pa o 
109 
THE TRANSIT OF VENUS 
AS the meeting of the Astronomical Society on 
November 8, a sketch was given of Lord Lindsay’s 
preparations for the forthcoming transit of Venus. Lord 
Lindsay has selected the island of Mauritius as his station, 
on account of its highly favourable meteorological condi- 
tions. He intends, if possible, to combine the following 
methods of observation :—1. Observations of the internal 
contacts to be worked out on the plans of Halley and 
Delisle. 2. Observations of the first external contact at 
the chromosphere, to be made with the spectroscope. 3. 
Photographic pictures. 4. Heliometric measures. For 
the longitude it is at present intended to use the transits 
of the moon with an altazimuth made by Simms. As it 
is expected that the Germans will also have a station on 
the Mauritius, Lord Lindsay will connect his station with 
theirs by triangulation. The transit instrument is by 
Cooke, and has four inches aperture, The chronograph, 
which can be kept in motion for four hours, has four 
barrels, each of which can be worked separately, thus 
avoiding all confusion. The photographic method to be 
used is that of Prof. Winlock, who suggests a telescope of 
40 feet focal length, placed horizontally, and a heliostat 
to reflect the sun’s image along it. The lens is to be an 
achromatic one. It is intended to have two planes to the 
heliostat, one mounted on a polar axis, and another to send 
the rays down the tube. Lord Lindsay has ordered a 
Foucault siderostat with 16-inch mirrors, and has obtained 
a 13-inch unsilvered mirror to fit the telescope to be taken 
out. He intends to use a heliometer, though it is not much 
in favour in this country, Messrs. Respald, of Hamburgh, 
having undertaken to make one for him with all the im- 
provements used in the Oxford instrument, as well as in 
some others. The Germans intend to send one to Ker- 
guelen Land, and the Russians will use it at Lake Baikal 
and the mouth of the Amoor. Lord Lindsay’s will include 
the motion of the halves of the object-glass in curved 
slides, so that the images will remain in focus; unlimited 
rotation of the tube in the cradle ; the measurement of the 
position angle at the eye end, and measures of the micro- 
meter read there also. Some new points are ;—the gradua- 
tion of the slides of the object-glass side by side, so as to 
be read by the same microscope ; an arrangement to shut 
off light from half the object-glass, so as to equalise the 
light of the images ; and the introduction of a thermometer 
at the end of the tube. Lord Lindsay proposes to eliminate 
errors of division as affected by temperature, by placing 
the instrument on one of the collimating piles of his transit 
circle at home, and heating the room by gas to different 
temperatures. It is hoped that, by taking a large number 
of measures, and by taking the most careful precautions, 
the original error of observation may be reduced to less 
than o”°5, and thus make the result one of extreme accu- 
racy. 
Lord Lindsay will be glad to receive the advice and 
assistance of astronomers accustomed to use the helio- 
meter. Mr. D. Gill will accompany Lord Lindsay, the two 
Gividing the work of observing between them. 
THE “ CHALLENGER” 
Oe Friday last, Dec. 6, several members of the council 
and “the Circumnavigating Committee” of the 
Royal Society, by invitation of the Lords of the Admiralty, 
inspected at Sheerness H.M. ship Cha/lenger, which 
sailed on Saturday on her three or four years’ scientific 
circumnavigating expedition. The Government have all 
along consulted the Royal Society as to the fitting out of 
this expedition, and have liberally carried out every 
suggestion made by the Circumnavigation Committee. 
The visitors to Sheerness on Friday included many dis- 
tinguished men of science, among them being Sir William 
