128 
POPULAR SCIENCE REVIEW. 
QUARTERLY RETROSPECT. 
A S we glance cursorily over the scientific events of the last few months, 
we cannot help being struck by the growing influence exercised by 
man over the powers of the universe — an influence whereby these forces are 
daily rendered more and more subservient to his purposes. 
The subject by which our attention is especially arrested, is that of 
Astronomical Photography. 
Not only does the glorious orb of day, by means of the warmth and light 
which it imparts, serve to sustain our vitality and that of the numerous tribes 
of plants and animals that surround us ; not alone do its rays illumine all 
Nature , but they have been impressed into the service of Art, and are now 
employed as pencils to delineate and register the phenomena and changes to 
which the solar orb itself is subject. 
At the recent meeting of the British Association for the Advancement of 
Science, Mr. Warren De la Rue made the following communication to the 
members : — 
“ I have obtained some sun-pictures, of very considerable promise, on the 
extremely large scale of the sun’s diameter ecpial three feet. These pictures 
have only been very recently procured, and I submit them to the section because 
I believe that an interest is felt in the progress of celestial photography, and 
that our members prefer to take part in the experiments, as it were, by 
watching their progress, rather than to wait until the most favourable results 
have been brought about. I may state, the mechanical and chemical difficulties 
have been surmounted, and the only outstanding one is the form of the 
secondary magnifier. When this has been worked out, perfect sun pictures, 
three feet in diameter, will be obtainable with a telescope of one-foot aperture 
in less than the twentieth of a second of tune. These pictures, when taken 
under suitable circumstances, may be grouped so as to produce stereoscopic 
pictures, which must throw considerable light on the nature of the spots.” 
But the enterprising artist of the heavens is not contented with the portraits 
that our sun furnishes of itself : the suns of other systems, with their attendant 
planets, must shed their lustre on his sensitive tablets, and map themselves 
to aid him in his studies and his speculations. He thus continues — 
“We now know that the luminous prominences which surround the sun, 
for they do belong to him, can be depicted in from twenty to sixty seconds, 
on the scale of the sun’s diameter equal 4 of the object-glass employed. 
That is to say, an object-glass of three inches aperture will give a picture of 
the prominences surrounding a moon four inches in diameter.* The next 
subject I have to call your attention to is the photographic depiction of groups 
of stars, for example, such as form a constellation like Orion — in other words, 
the mapping down the stars by means of photography. I have made several 
experiments in this direction, and have obtained satisfactory results, and I 
believe that, at last, I have hit upon an expedient which will render this 
method of mapping stars easy of accomplishment.” 
Here the astronomer leaves the heavenly bodies for the present ; but now 
the chemist “ takes up the wondrous tale.” Seizing their luminous rays, just 
released by his brother-investigator, he analyses them, and from their pale light 
* This refers to the experiments made by the lecturer 011 the solar eclipse. 
