4 
covered by the earth’s shadow had no effect on the plate after 
an exposure of 1 5 seconds, although distinctly visible in the 
telescope. It was noticed that the southern limb of the 
moon showed the copper-coloured tint often seen during 
total lunar eclipses, and to this cause may be attributed the 
non-actinic effect on the sensitized plate. An exposure of 
about one or two tenths of a second gave the fully illuminated 
surface of the moon perfectly, but the parts covered by the 
penumbra were not defined, while an exposure of three 
seconds gave the outline of the earth's shadow with great 
distinctness, and an exposure of two seconds brought out 
some of the detail within the penumbra. Some of the 
negatives were obtained almost instantaneously. 
The telescope with which these pictures of the moon were 
taken is an equatorial of 5 inches aperture and 6 feet focal 
length, driven by clockwork. This telescope gives the image 
of the moon about xiths of an inch in diameter, but by 
using a Barlow’s lens this size is increased to 1 J inch, and 
with this addition the eighteenth negative of the series was 
obtained in two seconds. 
Dr. Joule, F.R.S., exhibited and explained the construc- 
tion of a camera which he had contrived for outdoor work 
without a tent. 
In this camera the operation was carried on by the succes- 
sive introduction of the sensitizing and developing baths, the 
mode of the application of the baths being similar to that 
already described by the author. By a special arrangement 
the holders of the plate are preserved from contact with the 
developing solution. 
