"The cumbersome and
inconvenient Double Microscopes of Dr. Hook and Mr.
Marshall, were many Years ago reduced to a manageable
Size, improved in their Structure, supplied with an
easy Way of enlightening Objects by a Speculum
underneath and in many other respects rendered
agreeable to the Curious, by Mr. Culpeper and Mr.
Scarlet. Some farther Alterations were however wanted
to make this Instrument of more general Use, as I
fully experienced in the Year 1743, when examining
daily the Configurations of Saline Substances, the
Legs were continual Impediments to my turning about
the Slips of Glass; and indeed I had found them
frequently so on other Occasions Pulling the Body of
the Instrument up and down was likewise subject to
jerks, which caused a Difficulty in fixing it exactly
at the Focus: there was also no good Contrivance for
viewing opake Objects. Complaining of these
Inconveniencies, Mr. Cuff, the Optician, applyed his
Thoughts to fashion a Microscope in another Manner,
leaving the Stage entirely free and open by taking
away the Legs, applying a fine threaded Screw to
regulate and adjust its Motions, and adding a concave
Speculum forObjects that are opake.
The foregoing
Examinations having been all made by an Instrument
thus improved, I shall give a Plate and Description
of it, (as an Addition to my former Book on the
Microscope) by the Name of Mr. Cuffs new constructed
Double Microscope.
All Parts of this
Instrument are Brass. - The Body A, being firmly
supported in a broad circular Collar at the End of
the Arm a a, which projects from the Top of the
Pillar C, may be taken out or put in at
Pleasure.
A square Box b b,
screwed down to the wooden Pedestal 11 supports the
whole Machine by the Assistance of, the long
flat-square Pillar B, which is fixed within the said
Box.
The moveable Pillar
C, which is shorter than the Pillar B tho' of the
same Shape, by sliding up or down against the broad
flat Side of the said Pillar, raises or lowers the
Body of the Microscope as occasion may require. Both
Pillars stand in the Box b b.
The square Collar D
holds the two Pillars B and C together, and slides up
or down upon them, carrying with it the Body of the
Microscope. The Screw-Button 3 is intended to fix the
Pillar C, when the upper Edge of the Collar D being
set at the same Number as that of the Magnifier
employed, its focal Distance is brought nearly
right.
When the Pillar C
is fastened, the Microscope (by the fine-threaded
adjusting Screw E) may be moved so gently up or down,
without Jerks or Slips that the true Focus may be
found with great Readiness and Exactness.
The horizontal
Plate or Stage F, having in the Middle thereof a
circular Hole 4, directly over which the Body of the
Microscope is suspended, is exceedingly convenient to
place Objects on for Observation, being freed
entirely from the Legs which encumber other Double
Microscopes.
The concave Looking
Glass G, turning on two small Screws in the Arch d
(at the Bottom of which a Pin goes down into the Hole
e in the Pedestal) reflects the Light of a Candle or
the Sky directly upwards on the Object, by moving the
Looking Glass horizontally or vertically.
A double convex
Lens H, turns on two Screws, for transmitting Light
to assist in illuminating opake Objects, when the
long round Wire f is placed in the Spring-Tube g, at
the Corner of the Stage F.
I-- is a hollow
Cylinder whose sides are open, and at whose End a
concave Silver Speculum h, having a round Hole in the
Midst thereof, is screwed. This Cylinder flips over
the Snout i of the Microscope, and when set to the
Figure there marked, and correspondent to the Number
of the Magnifier made use of, the Silver Speculum
reflects Light on the opake Object to be examined;
which Object must either be held in the Spring-Tongs
at one End of the Wire O, placed in the Slit m on the
Stage F; or be put on the Ivory Block P, stuck on the
pointed End of the said Wire. The third or fourth
Magnifiers are fittest to be used with the Silver
Speculum.
K. L. M. N. QQ. R.
S. T. V. W. X. Y. Z. are different Parts of the
Apparatus which I think needless to describe, as all
who are acquainted with Microscopes will know them at
first Sight, and others may inform themselves either
in my former Treatise on these Subjects, or in the
Book which Mr. Cuff gives to those who buy this
Microscope of him."
Views through the
microscope of two specimens between mica disks on
an ivory slider: