612 
NATURE 
[APRIL 28, 1904 
It seems preferable to say that the regions where 
calcium exists correspond to those regions where 
hydrogen is absent than to say that the bright calcium 
flocculi resemble in form the dark hydrogen flocculi. 
To show the confusion to which such a form of 
description as the last mentioned can lead one, a good 
instance is given on Plate viii., Figs. 3 and 4, of Prof. 
Hale’s publication. There are shown two illustrations 
of the same region of the sun, one taken with the 
calcium line (K,), and the other with the hydrogen 
line (H8). On each of these there is a peculiarly 
shaped dark patch, evidently the same region on the 
solar disc, and the photographs show that in this 
region neither calcium nor hydrogen is present. 
According to Prof. Hale’s notation, this patch should 
be called both a ‘‘ dark calcium ”’ and ‘‘ dark hydrogen 
flocculus*’! As a matter of fact, the marking might 
be due to quite another substance altogether, and 
although it appears dark when analysed with either 
Fic. 6.—Two photographs of the same region of the solar disc 
taken on the same day, showing that where the bright 
calcium flocculi are present (upper photograph), the bright 
hydrogen flocculi (lower photograph) are absent. 
the calcium or hydrogen lines, it might appear as a 
“bright flocculus ’’ if a line in the spectrum of the 
substance of which it is composed were used. Thus 
if at the particular levels at which the photographs 
were secured we knew that helium had been present 
in this region, then it would have been shown on the 
photograph as a dark patch if the calcium and 
hydrogen lines had been employed, and as a bright 
one if any of the helium lines had been isolated by the 
secondary slit. 
Enough, perhaps, has been said to indicate that 
what is meant by the “‘ dark hydrogen or calcium ”’ 
flocculi is not quite clear. 
The fact brought out by the beautiful series of photo- 
graphs of Prof. Hale, that when the bright calcium 
NO. 1800, VOL. 69] 
flocculi are absent the bright hydrogen flocculi are | 
present, raises a number of important points in solar 
physics which the spectroheliograph alone at the 
present time can attempt to solve. 
Calcium and hydrogen are not, however, the only 
substances which exist in the solar atmosphere. How 
are the other materials distributed? The compara- 
tive thinness of the lines of these other substances in 
the solar spectrum makes it more difficult to analyse 
their distribution over the solar surface, but neverthe- 
less possibly many of the strongest lines may yet be 
analysed. 
It will thus be seen that the new spectroheliograph 
in the hands of Prof. Hale and his co-worker, Mr. 
Ellerman, has opened up a new field of research which 
apparently has no limit. The facts that the sun is 
continually changing in activity and that the sky in 
any particular place is not always clear point out that 
for the study of the distribution of any particular 
element on the disc, one spectroheliograph at one 
station is not sufficient. Just as in the case of sun- 
spots, three stations, widely separated, are required 
to produce a nearly daily record, so with this new 
instrument the same number of stations would be 
required for the study of one element. For the com- 
plete study of several elements, it will be seen, 
numerous instruments will have to be employed if every 
advantage is to be taken immediately to begin to gather 
the necessary material. 
So important is it that this new instrument for 
solar research should be employed to tell us of 
the changes that are taking place in the sun from day 
to day and from year to year, that no time should 
be lost in constructing a sufficient number of them, 
in distributing them where the raw material, sunlight, 
can be most often procured, and in organising a 
homogeneous plan of campaign. 
When it is considered that a study of the solar 
changes is vital for the clear understanding of the 
numerous terrestrial variations which are so closely 
associated with our everyday life, the necessity of such 
a programme is obvious. 
Just as in the case of the charting of the heavens, so 
this work should be of an international character, for 
every country would be able to reap equally the benefits 
which such an organisation would bring. 
The Rumford spectroheliograph of the Yerkes 
Observatory having thus shown the exceptional value 
of this new method of solar research in the hands of 
Prof. Hale and Mr. Ellerman, future workers will 
find their task very much lightened by a study of this 
magnificent and epoch-making contribution to solar 
physics. It is satisfactory to note that for this work 
in particular among other valuable contributions to 
astronomy by the same author, the Royal Astronomical 
Society has this year awarded Prof. Hale its gold 
medal. WitiraM J. S. Lockyer. 
COMMEMORATION DAY AT THE 
UNIVERSITY OF GLASGOW. 
@* Tuesday, April 19, many of us were thinking 
of the Kelvin jubilee, which attracted the fore- 
most scientific men of Europe here in 1896. It is only 
a fortnight since the body of graduates unanimously 
elected Lord Kelvin to be our academic chief. In 
tgo1 the university celebrated the ninth jubilee of her 
own foundation. On April 19 she inaugurated an 
annual commemoration day. : 
The ceremony opened with a short religious service. 
After it Sir William Ramsay, who began his great 
career as a chemist here, discoursed on Joseph Black— 
the most famous chemist who has been connected with 
