As objefts muft be brought very near the glaffes when the
greateft magnifiers are ufed, be particularly careful not to fcratch
them, by rubbing the Aider againft them as you move it in or
out. A few turns o f the fcrew C C will eafily prevent this mif-
chief, by giving it room enough.
Description op a S crole for fixing W ilson’s Pocket
Microscope, and reflecting L ight to it by a
M irror.
A B C , Fig. 2, is a brafs fcrole, which, for the better conve-
niency o f carriage, is fo ordered as to take into three parts, and
put into the drawer upon which it ftands, with it’s refiedting mirror
and Wilfon’s pocket microfcope.
The top part o f the fcrole is taken off at B, by unfcrewing half
a turn of the fcrew; then lift it up, and it comes out o f the
focket. The lower part unfcrews at C, and the bafe unfcrews
at E.
The mirror lifts out at F, which, with the fcrole, lie in one
partition of the box.
T o apply this fcrole to ufe, fix the body of the microfcope to
the top thereof by the fcrew A, as in Fig. 2, by ferewing it in
the fame hole as the ivory handle.
The brafs of ivory Aider being fixed as before defcribed, and
the microfcope placed in a perpendicular pofition, move the reflecting
glafs D in fuch a manner as to caff the light o f the Iky,
4 the
the fun, or a candle, directly upwards through the microfcope ;
by which means it is made to anfwer moll o f the ends o f a double
reflecting microfcope.
It is alfo rendered, more ufeful for viewing opake objects by
ferewing the arm O R , Fig. 1, into the body o f the microfcope at
G ; then ferewing into" the round hole R that magnifier which you
think will beft l'uit your objeft, and putting the concave fpeculum
S, on to theoutfide o f the ring R, you will find in the body o f the
microfcope, between the wood or brafs F, and the end o f the
male fcrew C C, a fmall hole u, through which Aides the long
wire T , which has a point at one end and forceps at the other,
that may be ufed occafionally, as your objeft requires: when you
have fixed this, and your object on it, turn the arm R, which is
performed by two motions, till the magnifier is brought over the
object; it may be then adjufted to the true focus, by turning the
male fcrew C C in the fame manner as before defcribed. It muft
alfo be turned exaftly over the fpeculum, by twilling the upper
part of the fcrole to one fide, till your object and the twofpecu-
lums are in one line, as wilLbe found by trial; and then fix it by
the fcrew B, at which time the upper furface of the object will be
fo exceedingly enlightened by the light reflected upward from
the mirror to the concave fpeculum, as to be feen as clear and
diftinft as any tranfparent one.
Description of a small Microscope for opake O bjects,
Fig. 3 and 4, Plate II. B.
A, Fig. 4, is a fixed arm, through which paffes a fcrew B,
the other end whereof is faftened to the moveable arm C.
O 2 D is