75 
the moon’s libration. The most beautiful stereoscopic prints 
of the moon are those by Mr. De la Hue. Mr. Fry also was 
very successful in this branch of celestial photography. 
In this brief history of the subject of celestial photography, 
I have not referred to anything which has been done in 
making photographs of the solar spots, but the matter must 
not be altogether passed over. The first step in this 
direction appears to have been taken in France, in 1845, by 
MM. Fizeau and Foucault, but it is chiefly due to the efforts 
of Mr. De la Hue that so much useful work has been done in 
heliography. In 1860 Mr. De la Hue and his staff of assist- 
ants performed one of the greatest feats yet recorded in this 
branch of the art of photography, having succeeded in 
obtaining several beautiful negatives of the various phenomena 
seen only during total eclipses of the sun, and two negatives 
were obtained during the totality. One question of much 
interest to astronomers was determined by this great experi- 
ment. The red prominences or flames generally seen as 
issuing from the edge of the moon were proved to belong to 
the sun. Photographs of the sun are taken daily when the 
weather is favourable at the Kew Observatory, and also by 
Professor Selwyn, at Ely. With the Kew photoheliograph 
pictures of the sun spots have been made on the scale of 
three feet to the sun’s diameter. Much, however, remains to 
be done. The light of thesun is much in excess of what is 
required to obtain a collodion picture, so that the loss of light 
consequent on the necessary interposition of lenses and the 
distance of the plate from the instrument can be no objection ; 
and for these reasons I have very little doubt that with 
apparatus suitably arranged photographs of spots and groups 
of spots will be obtained of very much larger diameter than 
any yet taken. 
The Quarterly Journal of Science for April, 1864, contains 
the next important paper on celestial photography. It is by 
Dr. Henry Draper, one of the Professors at the New York 
