much greater pretensions, costing three
guineas and a-half, which is more frequently
than not employed (mostly for transparent
objects) with a force below its utmost pressure
of steam. I keep in reserve a several
horsepower of amplification for extraordinary
occasions. Both these microscopes are from
Amadio, of Throgmorton Street, and are
excellent of their kind, the more expensive
one especially. Thus, for a sum which has
not ruined me, and for which I can proudly
show the stamped receipts, I am master of a
higher magnifying power than Leeuwenhoek
had at his command; notwithstanding which
I have considerable doubts whether I shall
ever rival his scientific eminence. You will
understand that nothing herein premised is
contrary to the possibility that I have safe in
my closet a hundred-guinea microscope, for
Sundays and holidays, unless you are thinking
of presenting me with one, to aid my
studies; in which case, I beg to withdraw
the observation. But never forget that the
excellence and value of a microscope do not
consist in the greatness of its magnifying
power. So far from that, if the instrument
be muddle-headed and cloudy, the stronger it
is the worse it is; and that instrument is
the most efficient which renders the details of
an object perceptible with the lowest
power. Distinctness of definition—by which
is meant the power of rendering all the
minute lineaments clearly seen— is a quality
of greater importance than mere magnifying
power. Indeed without this quality, mere
magnifying power ceases to have any value;
since the object appears merely as a huge,
misty phantom, like Ossian's cloudy heroes.
It is more satisfactory to gaze upon a tight
little yacht in bright, clear sunshine, than to
be able to say you have seen the hazy
outline of a vast line-of-battle-ship, looming
indistinctly through a dense fog.

Leeuwenhoek's plan of having a multiplicity
of instruments is a good one, for many
reasons. Only to mention two; first, the
saving of the time required to screw on,
and unscrew, object-glasses. Secondly, the
feebler instrument will act as the finder for
the stronger. It will play the jackal to the
lion, and often inform you whether there is
anything worth looking at. In justice, be it
added, that, in this country, Mr. Ross, and also
Messrs. Powell and Lealand, enjoy a celebrity
as microscope-makers, which they would not
have attained if they had not deserved it;
while, in Paris, M. Nachet's name is in every
microscopist's mouth. There is an old-
fashioned, little, simple, pocket microscope
for transparent objects only—Wilson's, who
flourished about seventeen hundred—which
is a great favourite with many a peripatetic
Paul Pry, and which is so convenient
and entertaining as to be worth purchasing
—good and cheap—when it falls in your way
in its antique mounting.

The more powerful and refined the instrument,
the more difficult is its management,
and the greater are the skill and tact required
to make it of any service to its owner. The
apparent increase of size given to an object is
usually spoken of in diameters, or the linear
measure across it in any direction. Thus,
fancy a circle magnified to another which has
a hundred times its original diameter, and
you have an increase of some considerable
importance. A moon shining in the heavens
with a diameter a hundred times that of our
own monthly moon, or fifty degrees across,
instead of half a degree, would be enough to
make every sane man a lunatic and convert
simple lunatics into raving madmen. Supposing
it were possible to construct a microscope
that should magnify, say a bull-dog, only sixty
diameters, and that there were eyes capable
of using such a microscope—what a
monstrous bull-dog the image would be! Dr.
Lardner coolly discourses of "the superior
class of instruments, where magnifying
power is pushed to so extreme a limit as
fifteen hundred or two thousand." Of course
first-class microscopes such as these, demand
the most masterly skill from the optician,
and are affected by infinitesimally small
derangements. Mr. Quekett gives drawings of
Naviculæ magnified twelve hundred and two
thousand diameters respectively; only making
you wish for a good microscope to bear upon
these, the magnified drawings.

Again, for your comfort, dear reader with
limited means like myself, one of the first
microscopists living, M. le Dr. Ch. Robin,
tells you that the magnifying power of the
microscope can reach as far as a thousand or
eleven hundred real diameters; that faulty
modes of mensuration have been the only
cause of making people believe they had
obtained more considerable amplifying powers.
It ought, moreover, to be known, he says,
that when once eight hundred diameters are
passed, object-glasses and eye-glasses which
magnify further, fail to show the slightest
novelty; not that the light is absolutely too
feeble, or the colours of the object too diffuse,
but simply because nothing additional is
perceived beyond what was seen at seven or eight
hundred diameters. It very rarely, or never
happens, that there is any need to go beyond
six hundred diameters for pathological observations;
which in general require the highest
magnifying powers. Bear in mind, also, what
Leeuwenhoek did with a hundred and sixty
diameters as his extreme power. Look at a
cheese-mite with a power of thirty only, and
you will be astonished if you have never so
seen one before. Students, whose aims at
starting are not quite extraordinary, will
learn more than they can anticipate in their
wildest dreams, if they have at hand the
means of magnifying an object two hundred
and fifty diameters, at the outside. Nevertheless,
it is good for them to be able to get
at a more powerful instrument from time to
time.