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I N T R O D U C T I O N . 5
relieves the flice at the very inftant that the cutter has wholly done its office: and thus the
llices are made to fall into fpirits of wine, in which they arepreferved for ufe.
In feme woods the pith ilirinks fo very faft, that it is extremely difficult to keep it entire,
in ilices that are thinner than 750 to an inch: to remove which imperfeftion, an ihftrument,
of the nature above defcribed, was made to Ihift its own fcrew at every revolution of the
handle, fo that very little time was left for the pith to ilirink; as a hundred flices could
eafily be cut in a minute, and the pith was as entire as the wood. This inftrumenthad an
index, which beingfetto.the numbers 500,750, iooo,madeitcutfo many ilices toan inch.
It performed extremely well, but was judged lefs fit fo\ general ufe than that which has
already been defcribed, it being more complex, and liable to diforder, as well as more
difficult to manage.
The compofition of the Mi c r o s c ope (which was made, by direition of the Noble Perfon
who is pleafed to be the Patron of this Work, and its Author; by Mr. Adams, in
Fleet-Street, Mathematical-Inftrument-Maker to His Majefly) will be underftood by the
annexed figure. Plate II.
A D E S C R I P T I O N
OF THE V a r i abl e Microscope.
A B C , the body of the Microfcope, contains two eye glafles at A, a third near B, and PLATE
a fourth in the conical part B and C. The end C fliews alfo one of the magnifiers fcrewed
thereto.
Hence the body of this Microfcope exceeds thofe hitherto made, which have only
three glafles; by encreafing the field of view, and the light; as well as affording an
occafional opportunity of increafing the magnifying power of each particular objedl glafs:
which is performed by pulling up the part A E, and the outward tube A B : the firft
feparates at A, the other at B.
Another advantage attending this inftrument is, that any two of the magnifiers maybe ufed
at the fame time; in this manner: fcrew the button b to the part c of the button <2, and then
fcrew both together into the body at C ; the magnifier therereprefented being firft removed.
There are feven of thefe magnifiers j two of which are fliewn at a and b: alfo fix filver
ipecula, each having a magnifier adapted to the focus of its concavity ; one of which is
reprefented at e-, thefe are to be fcrewed occafionally to the body at C. Every one of the
ieven buttons, a b, may alio be ufed with any one of iheie fpecula, by fcrewingthelowerpart
of the fruftrum of a.cone, which is figured at d, upon the prominent fcrew on the filver
fpeculum at c, and then fcrewing the part c of any button b into its upper end, and all
together into the body at C.
Note, The glafles are marked 1 ,2,3, ^^^^ ^^^^ number ^s the greatefl: magnifier.
The body of the Microfcope A B C is fupported by an arm F, into which it may be put
or taken out occafionally, and may be faftened by the.fcrew f . This arm is fixed to the
bar G G, which may be raifed. or depreflTed by turning the large ivory head I, (the fcrew
at H being firft difcharged.) G G Hides clofc to the upper part of the long bar K L, which
laft is firmly fixed at N and N to the tooth-wheel N O N ; this wheel is fupported by
four fcroles, whofe extremities are connefled to an horizontal circular plate n, which gives
an horizontal motion to the wheel, the bar K L, and every other part of the Microfcope
which is connefted thereto; the whole being fupported upon the pillar 'M by the three
feet P P P.
The annexed figure of the Microfcope is delineated from its perpendicular pofition, being
that which affords the befl: reprefcntation of its feveral parts; but there will be no difficulty
to conceive, that on turning the key S the pinion that works in the teeth of the wheel
N O N