Extracted from the 5th
edition of Carpenter's The Microscope,
1875:
Messrs. Becks'
First-class Microscope- It was by this Firm that the
Jackson model was first adopted, for which the Author
has already expressed his preference; the support of
the Body along a large proportion of its length, upon
the substantial Limb to which the Stage is securely
attached, giving it a decided advantage in steadiness
over any form of instrument (not exceeding it in
massiveness) in which the Body is attached at its lower
extremity only to an Arm between which and the Stage
there is no fixed connection; whilst the
Rack-and-pinion movement giving the coarse adjustment
can be made to work more easily on this construction,
than where it is requisite that the stem moved by it
should be fitted as tightly as possible. On the other
hand, it must be admitted that the 'fine' adjustment
can be more effectually made by the longer leverage
provided in the Ross model, than by the attachment of
the screw to the lower end of the body, as in the
instrument before us. The Stage of the older form of
this instrument was furnished with the usual traversing
movements, and was made (by an arrangement first
devised by Messrs. Smith and Beck, and since adopted by
other makers) so thin as to allow of extremely oblique
illumination; but although the platform which carries
the object could be made to rotate upon the traversing
apparatus, yet the object was liable to be thrown out
of centre by this rotation. This has been completely
remedied in the newer pattern shown in Plate VII. the
Stage of which has a nearly complete rotation in the
optic axis of the instrument. This rotation is effected
by a milled-head and pinion; which, by a shifting
movement can be thrown out of gear, so as to allow the
Stage to be rotated rapidly by hand, which is often
advantageous. This Stage is furnished with a graduated
circle, to which a Vernier can be attached when desired
for the measurement of angles.