98 
Of course, in England and in France, celestial photography was 
successfully carried on concurrently with similar work in America, 
and it would be difficult to assign a sharp line of demarcation which 
would place any one of these countries far in advance of the others 
in the keen but noble efforts to enlarge the boundaries of knowledge 
by the application of the newly-discovered powers of photography. 
Warren De la Rue, in England, in 1853, produced excellent photo- 
graphs of the moon, and, in 1858, instituted the method of photo- 
graphing sun spots, which was effected continuously until 1872. In 
France, Foucault and Fizeau also photographed the sun, in 1845 ; 
and in America, Rutherford, in 1864, made an important step in 
advance by the construction of a telescope with an objective of 
eleven and a half inches aperture, corrected, not for visual observa- 
tion, but exclusively for photographic work. This was improved, in 
the year 1885, by the brothers Henry, of Paris, who constructed a 
photo-telescope of thirteen inches aperture, and with it succeeded 
in photographing stars of the sixteenth magnitude, in May, of that 
year ; and it so happened that I also had a reflecting telescope made, 
having an aperture of twenty inches, with which I commenced, in 
May, 1885, to chart the stars in the Northern hemisphere of the sky 
on a scale about double that adopted by Argelander. But Dr. Gill, 
the Director of the Cape Observatory, and the late Admiral 
Mouchez, Director of the Paris Observatory, proposed and admir- 
ably carried into execution a scheme of charting the stars by photo- 
graphic instruments of identical aperture, focal length and chro- 
matic corrections as those adopted in the Paris instrument made by 
the Henrys. ‘There are now eighteen of those telescopes in obser- 
vatories, situated in different parts of the world, regularly engaged 
in taking photographs of the sky, so as to produce a great chart of 
all the stars down to the fourteenth magnitude. Therefore, the 
charting which I had commenced is superseded by a more efficient 
method, and my twenty-inch reflector, practically, is turned to use 
in photographing nebule and clusters of stars, an employment for 
which it is better adapted than the thirteen-inch photo-refractors 
used in the charting. 
The merits of the reflector in photographing faint stars and faint 
nebulosity was pointed out by Dr. Common, in England, in the 
year 1883, and my experience since fully confirms his. I must not 
here attempt even a cursory description of the great work done dur- 
ing recent years in the photographing of solar, stellar and nebular 
