and in the
Newtonian reflector (which has only two specula or mirrors) there is no
refrangibility to be corrected; apart from which, 'correcting
refrangibility' has no more meaning than 'restoring the angle of
incidence.'

'"And," continued Sir John, "why cannot the illuminating microscope, say
the hydro-oxygen, be applied to render distinct, and, if necessary, even
to magnify, the focal object?" Sir David sprung from his chair' [and
well he might, though not] 'in an ecstasy of conviction, and, leaping
half-way to the ceiling, exclaimed, "Thou art the man!" Each philosopher
anticipated the other in presenting the prompt illustration that if the
rays of the hydro-oxygen microscope, passed through a drop of water
containing the larvae of a gnat and other objects invisible to the naked
eye, rendered them not only keenly but firmly magnified to dimensions of
many feet; so could the same artificial light, passed through the
faintest focal object of a telescope, both distinctify (to coin a new
word for an extraordinary occasion) and magnify its feeblest component
members. The only apparent desideratum was a recipient for the focal
image which should transfer it, without refranging it, to the surface on
which it was to be viewed under the revivifying light of the microscopic
reflectors.'

Singularly enough, the idea here mentioned does not appear to many so
absurd as it is in reality. It is known that the image formed by the
large lens of an ordinary telescope or the large mirror of a reflecting
telescope is a real image; not a merely virtual image like that which is
seen in a looking-glass. It can be received on a sheet of paper or other
white surface just as the image of surrounding objects can be thrown
upon the white table of the camera obscura. It is this real image, in
fact, which we look at in using a telescope of any sort, the portion of
such a telescope nearest to the eye being in reality a microscope for
viewing the image formed by the great lens or mirror, as the case may
be. And it does not seem to some altogether absurd to speak of
illuminating this image by transfused light, or of casting by means of
an illuminating microscope a vastly enlarged picture of this image upon
a screen. But of course the image being simply formed by the passage of
rays (which originally came from the object whose image they form)
through a certain small space, to send _other_ rays (coming from some
other luminous object) through the