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time in The British Journal of Photography, and in 
August and September of the following year further details 
of Mr. De la Rue’s method of working were given in the 
same Journal. The processes and machinery employed are 
so minutely described that it is unnecessary here to say more 
than that Mr. De la Rue commenced his experiments about 
the end of 1852, and that he used a reflecting telescope of 
his own manufacture of thirteen inches aperture and ten feet 
focal length, which gives a negative of the moon averaging 
about lp^th of an inch in diameter. The photographs were 
at first taken at the side of the tube after the image had been 
twice reflected. This was afterwards altered so as to allow 
the image to pass direct to the collodion plate, but the ad- 
vantage gained by this method was not so satisfactory as was 
expected. In taking pictures at the side of the tube, a small 
camera box was fixed in the place of the eyepiece, and at the 
back a small compound microscope was attached, so that the 
edge of a broad wire was always kept in contact with one of 
the craters on the moon’s surface, the image being seen 
through the collodion film at the same time with the wire in 
the focus of the microscope. This ingenious contrivance in 
the absence of a driving clock was found to be very effectual, 
and some very sharp and beautiful negatives were thus ob- 
tained. Mr. De la Rue afterwards applied a clockwork 
motion to the telescope, and his negatives taken with the 
same instrument are as yet the best ever obtained in this 
country. 
The advantage of the reflecting over the refracting telescope 
is very great, owing to the coincidence of the visual and actinic 
foci, but it will presently appear that the refractor can be 
made to equal if not excel the work of the reflector. 
Mr. De la Rue's paper (as published in the report of the 
British Association,) contains some extremely interesting 
particulars as to the mode of obtaining stereoscopic pictures 
of the moon, and diagrams are given showing the effects of 
