1850-60] ROYAL ASTRONOMICAL SOCIETY 
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planets. Another successful exponent of the new art was Mr. 
Hartnup, of the Liverpool Observatory, who in 1854 obtained 
pictures of the moon said “ to have outstripped all other attempts 
made elsewhere.” He himself was disappointed with his results, 
a disappointment not unnatural when we realise that his confidence 
in the sharpness of image and minuteness of detail in his negatives 
led him to demand that they should stand enlargement from 1-3 
inches to 50 feet, equivalent to 460 diameters. A modern dry 
plate at such an enlargement would show little more than the grain 
of the silver deposit, and it is no small tribute to the excellence of 
these early wet plates that any picture at all remained. 
In 1854 it was decided by the Royal Society that a photo- 
heliograph should be established at Kew for the purpose of making 
a daily record of the state of the solar surface. De la Rue undertook 
the supervision of the design and erection of the instrument, and 
it was put into permanent use in 1858 March, remaining at Kew 
until its transfer to the Royal Observatory, Greenwich, in 1872. 
In that same year (1858) the whole astronomical world was 
thrilled by the appearance of a great comet (Donati’s), which for 
many weeks presented a spectacle of extraordinary beauty and 
interest. Attempts were made to photograph it, but there was 
then no instrument provided with the guiding accessories necessary 
for keeping the image fixed on the plate during a prolonged exposure. 
De la Rue could obtain nothing in sixty seconds, and the only 
recorded photograph is one taken by Mr. Usherwood on Walton 
Common with a stationary camera furnished with a portrait lens 
of short focus. We can only regret that no possessor of an 
equatoreal thought of the device of strapping such a camera on to 
his telescope, which would have given with a short exposure a 
record of this unique celestial object. We must content ourselves 
with noting the fact that Mr. Usherwood’s was the first photograph 
taken of a comet. 
It would not be right to leave this subject of photography 
without some allusion, however brief, to the work which was being 
done at the other side of the Atlantic. Two names are prominent, 
G. P. Bond at Harvard (1851) and L. M. Rutherfurd from 1864. 
In both cases their main object was the same, to develop photo 
graphy as a method of precision for the delineation and recording 
of star positions ; to what splendid development this has attained at 
Harvard is well known to all and need not be described here. 
Concurrently with this advance in celestial photography, a 
great improvement was made in the reflecting telescope by the 
substitution of the silver-on-glass for the speculum metal mirror. 
The previous decade had seen the completion of Lord Rosse’s 
6-foot telescope and its application to the resolution of nebulae, a 
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