368 De la Rue and Celestial Photography. [ July, 
moon may have an atmosphere of great density, but of very small 
extent, and that the so-called seas might be covered with vege- 
tation.” * 
In 1853, Professor John Phillips indeed noticed this difference 
between the visual and the actinic brightness of portions of the 
lunar surface. 
The application of photography to the planets by Mr. Warren 
De la Rue and others confirms this fact. For example, the occulta- 
tion of Jupiter by the moon on November 8th, 1856, afforded an 
excellent opportunity for comparing the relative brightness of our 
satellite and that planet. On that occasion, Jupiter appeared of a 
pale greenish tinge, not brighter than the crater Plato, and accord- 
ing to Mr. De la Rue’s estimate, of about one-third the general 
brilliancy of the moon; but the actmic power was subsequently 
found to be equal to fully four-sixths or five-sixths of that of the 
moon. “Saturn,” says the same observer, “ required twelve times 
as long as Jupiter to produce a photograph of equal intensity, on an 
occasion specially favourable to making the experiment; yet I 
obtained a picture of Saturn together with that of the moon in 
fifteen seconds on May the 8th of the present year (1859), just as 
the planet emerged from behind the moon’s disc. The picture 
of the planet, although faint, is sufficiently distinct to bear en- 
larging.” 
Jupiter, Mars, and Saturn, together with several of the fixed 
stars, have been photographed; but the promise afforded by these 
chemical pictures is not of that high character which belongs to 
those of our satellite. Studyimg the large picture of the moon, 
hanging in the Royal Society’s room, which has been produced by the 
aid of photography, we cannot but feel that we have a wonderfully 
minute representation of the lunar surface before us. We see, and 
we can measure the heights of her mountains and the depths of 
her valleys. Her coasts and cliffs, against which we cannot but think 
an ocean has at one time beaten its waters, are readily determined. 
We cannot mistake the craters of eruption, and we are puzzled with 
such as we must call craters of upheaval, vast swellings, the result 
of some mighty power which was yet insufficient to burst the stony 
bubble. Precipices so vast that darkness reigns in the profound 
depths over which they rise, and glens which appear indeed resigned 
to all the influences which superstition crowds into such weird 
gloom are there. Can we not trace glacial moraines? But to what 
are we to refer the mysterious streaks of light which flow from some 
of the lunar mountains? We cannot but hope, seemg how much 
has been done, that we shall have continuous photographic records 
of the moon’s surface. We may then expect to have a more exact 
knowledge of that lovely orb which belongs especially to our Earth, 
* “Transactions of British Association, 1859,’ p. 145. 
, t Ibid., 1853.‘ Transactions of Sections,’ p. 16, 
