same small space, is not to improve,
but, so far as any effect is produced at all, to impair, the
distinctness of the image. In fact, if these illuminating rays reached
the eye, they would seriously impair the distinctness of the image.
Their effect may be compared exactly with the effect of rays of light
cast upon the image in a camera obscura; and, to see what the effect of
such rays would be, we need only consider why it is that the camera _is_
made 'obscura,' or dark. The effect of the transfusion of light through
a telescopic image may be easily tried by any one who cares to make the
experiment. He has only to do away with the tube of his telescope
(substituting two or three straight rods to hold the glass in its
place), and then in the blaze of a strong sun to direct the telescope on
some object lying nearly towards the sun. Or if he prefer artificial
light for the experiment, then at night let him direct the telescope so
prepared upon the moon, while a strong electric light is directed upon
the place where the focal image is formed (close in front of the eye).
The experiment will not suggest very sanguine hopes of good result from
the transfusion of artificial light. Yet, to my own knowledge, not a few
who were perfectly well aware that the lunar hoax was not based on
facts, have gravely reasoned that the principle suggested might be
sound, and, in fact, that they could see no reason why astronomers
should not try it, even though it had been first suggested as a joke.

To return, however, to the narrative. 'The co-operative philosophers,
having hit upon their method, determined to test it practically. They
decided that a medium of the purest plate-glass (which it is said they
obtained, by consent, be it observed, from the shop-window of M.
Desanges, the jeweller to his ex-majesty Charles X., in High Street) was
the most eligible they could discover. It answered perfectly with a
telescope which magnified a hundred times, and a microscope of about
thrice that power.' Thus fortified by experiment, and 'fully sanctioned
by the high optical authority of Sir David Brewster, Sir John laid his
plan before the Royal Society, and particularly directed to it the
attention of his Royal Highness the Duke of Sussex, the ever munificent
patron of science and the arts. It was immediately and enthusiastically
approved by the committee chosen to investigate it, and the chairman,
who was the Royal President' (this continual referenc