valuable glass ruined by the proceedings of a workman who had been told
to attach three pieces of brass round the cell of the double lens. What
he had done remained unknown, but ever after a wretched glare of light
surrounded all objects of any brilliancy.

One word about the inversion of objects by the astronomical telescope.
It is singular that any difficulty should be felt about so simple a
matter, yet I have seen in the writings of more than one distinguished
astronomer, wholly incorrect views as to the nature of the inversion.
One tells us that to obtain the correct presentation from a picture
taken with a telescope, the view should be inverted, held up to the
light, and looked at from the back of the paper. Another tells us to
invert the picture and hold it opposite a looking-glass. Neither method
is correct. The simple correction wanted is to hold the picture upside
down--the same change which brings the top to the bottom brings the
right to the left, _i.e._, fully corrects the inversion.

In the case, however, of a picture taken by an Herschelian reflector,
the inversion not being complete, a different method must be adopted. In
fact, either of the above-named processes, incorrect for the ordinary
astronomical, would be correct for the Herschelian Telescope. The latter
inverts but does not reverse right and left; therefore after inverting
our picture we must interchange right and left because they have been
reversed by the inversion. This is effected either by looking at the
picture from behind, or by holding it up to a mirror.

[Illustration: PLATE II.]