suggested that in such a lens the same object might be attained
with greater ease by grinding an equatorial groove about a thick
or globular lens and filling the groove with an opaque cement.
This arrangement found much favor, and came subsequently to be
known as a Coddington lens, though Mr. Coddington laid no claim
to being its inventor.

Sir John Herschel, another of the very great physicists of the
time, also gave attention to the problem of improving the
microscope, and in 1821 he introduced what was called an
aplanatic combination of lenses, in which, as the name implies,
the spherical aberration was largely done away with. It was
thought that the use of this Herschel aplanatic combination as an
eyepiece, combined with the Wollaston doublet for the objective,
came as near perfection as the compound microscope was likely
soon to come. But in reality the instrument thus constructed,
though doubtless superior to any predecessor, was so defective
that for practical purposes the simple microscope, such as the
doublet or the Coddington, was preferable to the more complicated
one.

Many opticians, indeed, quite despaired of ever being able to
make a satisfactory refracting compound microscope, and some of
them had taken up anew Sir Isaac Newton's suggestion in reference
to a reflecting microscope. In particular, Professor Giovanni
Battista Amici, a very famous mathematician and practical
optician of Modena, succeeded in constructing a reflecting
microscope which was said to be superior to any compound
microscope of the time, though the events of the ensuing years
were destined to rob it of all but historical value. For there