lenfe. When the three lenfes areufed together, it is heft to turn
them into the cafe, and-look through the hole, as this combined
magnifying power is fo great, that it requires to have a portion
of the light which falls on the lenfes excluded, in order to attain
diftina vifion. Further, the éye is alfo by this means made to
coincide more eafily with the axis o f the glaflès.
D escription of a portable Microscope and T elescope,
F'g- 1» 2, 3, 4, 5, 6, Plate VIII.
The telefcope is one o f thofe which are compofed o f feyeral
Hiding drawers or tubes, for the convenience o f being put in die
pocket ; the.fliding tubes are made of thin brafs, the outfide tube
o f mahogany.
The Aiding tubes are contrived to ftop when drawn out to a
proper length, fo that by applying one hand to the outfide tube,
and the other hand to the end o f the fmallefi tube, the telefcope*
may be at one pull drawn out it’s whole length ; then any o f the
tubes (that next the eye is moft generally ufed) may be puftied in
gradually while you are looking through, till the objeft is rendered
diftinâ to the fight.
T o make the tubes Aide properly, they all pafs through Aiort
fpnngs or tubes; thefe fprings may be unfcrewed from the ends
o f the Aiding tubes by means o f the milled edges which proje#
above the tubes, and the tubes taken from each other i f required,
and the fpring fet clofer if it is too weak.
Fig-
/
M i c r o s c o p i c a l E s sa y s . 119
Fig. 5 reprefents the exterior tube o f the telefcope, which is
to be unfcrewed from the reft, as it does not make any part of
the microfcope; the cover k, which protects the objeft-glafs,.
ferves alfo as a box to contain the Aiders with the obj efts, and a
finall mirror.
Fig. 4 is a view o f this cover when taken off"; unfcrew the top.
part of it, and the mirror, Fig. 6, may be taken ou t; unfcrew the
cover o f the lower part, and yofi will find therein the two circular
Aiders reprefented at Fig. 1 and 2.
Fig. 3 reprefents the three internal tubes o f the telefcope,.
which conftitute the microfcopic part thereof. Draw the tubes
out in the manner that is feen in, Fig. 3 ; then on the infide, but
at the lower end o f the exterior tube, you will find a Aiort tube,,
which ferves as a ftage to hold the objeft and fupport the mirror;
pull this tube partly out, and turn it, fo that a circular hole
which is pierced in it may coincide with a fimilar hole in the exterior
tube. This tube is reprefented as drawn out at Fig. 3, the
mirror, Fig. 4, placed therein at L M , and the tranfparent Aider-
fixed at N Q.
Fig. 1 reprefents the Aider with tranfparent objefis;.
Fig. 2, that with opake. They are made o f ivory, and turn
on a pin at the center; the Ait end o f this pin fits on the edge o f
the tube, which is then to be puftied up, fo that the lower end o f
the exterior tube may bear lightly on the upper fide o f the Aider-
agreeable to the view which is given at Fig. 3. Now pufh down
the fecond tube-till the milled part falls on the milled edge o f the
O' exterioE