362 De la Rue and Celestial Photography. [July, 
graphy was promised in 1857 by Professor Bond, who applied 
the process in measuring the distance and angle of position of 
double stars, and also in determining their magnitude. He suc- 
ceeded in obtaining pictures of fixed stars down to the 6—-7th mag- 
nitude, and everything gave promise of a fruitful future, when death 
put a stop to his labours. 
In the same year (1857) Mr. Warren De la Rue was successful 
in applying a driving motion to his telescope, which answered every 
purpose desired ; and since that time he has unremittingly followed 
up the subject of Celestial Photography whenever his occupations and 
the state of the atmosphere permitted it. 
The Academy of Sciences of Paris has lately recognized Mr. 
De la Rue’s labours, by the high distinction of the Lalande prize of 
Astronomy. From the address which was delivered on the occasion 
of its presentation, many of the following notices have been derived. 
As the facts thus detailed have all been subjected to the most search- 
ing examination, they stand beyond suspicion, and furnish the most 
reliable record which it is possible to give of the progress which has 
been made in an inquiry involving the use of the most perfect astro- 
nomical instruments, the most delicate physical appliances, and the 
most sensitive chemical preparations, directed by a zealous and 
thoughtful mind. It has been by means of an equatorial reflecting 
telescope of thirteen inches aperture, designed by himself and con- 
structed in his own workshop, that Mr. Warren De la Rue has 
attained that degree of perfection in Astronomical Photography 
which has earned for him the gold medal of the Astronomical 
Society and the Royal medal of the Royal Society. 
His splendid photographic delineations of our satellite, with 
which the scientific world is familiar, owe their excellence, first, to 
the perfection to which the optical part of the telescope was brought 
by machinery of his own contrivance ; and, secondly, to the remark- 
able performance of his clockwork-driving apparatus, which not 
only works smoothly and equably, but is capable of rapid and easy 
adjustment to the ever-varying velocity of the moon. Mr. De la 
Rue’s chemical training has, moreover, enabled him to secure that 
nice balance of affinities in his photographic preparations, which has 
materially reduced the time required to impress the image on the 
sensitive tablet, and consequently to diminish the bad effects of dis- 
turbance of the image, resulting from the unsteadiness of our atmo- 
sphere. By these means, pictures of the moon have been repeatedly 
taken by him in the focus of his reflecting telescope, so perfect as to 
bear considerable amplification—for example, to thirty-eight inches in 
diameter. These images admit of measurement with the microscope, 
so exact as to furnish excellent data for investigations in relation to 
a supposed physical libration of the moon. These pictures are also 
now being used as the foundation of the large map of the moon, 
