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I N T R O D U C T I O N .
ÍT is propofed to fliew the ConftruiSion of Timber: the Number^ Nature, and Offices
of its fcveraJ parts; and their various arrangements and proportions in the different
kinds : To point out a way of judging from the ílruñure of Trees the ufes which
they will beft ferve in the affairs of life ¡ and of adding fomcthing to their flrength.
The compofition of the whole, the variations in the difpoiition, and the differences
in the proportion of the leveral parts, are, in' many of the fpecies, fo itrange, and in
fome fo very delicatci that to fee them diílinítly requires pieces of fuch an extreme
thinnefs, and magnifying powders at once fo great and fo clear, that it were vaiil
to lead men into an attempt of following the experiments, without firft acquainting
them with the machine by which the pieces were cut; and the Microfcope thro' which
they have been viewed.
The Cutting Engine is an invention of the ingenious Mr. Cummings. The two
or three firil were perfefted under his own hand j and they are now made for general uftí
by Mr. Ramfden,
D E S C R I P T I O N ÁN INSTRUMENT
For cutting Tranfverfe Slices of WOOD, for MICROSCOPICAL OBJECTSI
A A. Plate I. Fig. i. reprefents a cylinder of ivory, three inches and a half long, PLATE
and two inches in diameter j to the one end of which is fitted I.
B B. A plate of bell-metal\ the fcélion of which, with the manner of fitting it to the '
ivory, may be feen in Fig. 2. in which the feveral parts are marked with the fame letters
as in Fig. i.
C. is a plate of brafs, fitted to the other end of the cylinder j through which and the
ivory there pafs two long fcrews, which take into the thick part of the bell-metal B B,
fo as to fix both plates llrongly to the ivory; into which they are alfo indented, fo as
to prevent fuch (haking as might otherwife happen after fwelling or ihrinking.
D D. The Cutter-, whofc edge is a fpiral, and the difference of whofe longeft and fhortell
radii is equal to the thicknefs of the largefl piece of wood that the inftrument would take in.
The loweft fide of this cutter rauil be ground extremely flat and true, in order that all the
parts of its edge may be exañly in the fame plane; and that the middle part of it may be
applied clofely to the flat circular plane left at the center of the plate B B, to preferve it in
the proper diredion when carried round by the handle.
All that part of the bell-metal, which the edge of the cutter traverfes, rs turned folow as
not to touch it, (fee theSe<ftion:) the middle of the cutter is about-^of an inch thick, and
has in it a fquare hole that fits on tlie end of a fleel axis P P, one end of which turns on a
pivot in the Plate C, the other end in the plate B B. This end has a conical fhoulder which
fits into a hole of the fame lliape in the under fide of the plate, as reprefented in the SeiSion.
e £. Apiece of brafsfomewhat in the form of an index, which is alfo put on the axis P P :•
this piece has a round hole in its center fo large as to admit of its being turned irrto any
pofition with regard to the cutEcf; and in order to keep it concentric thereto there is left
on it a circular projedHon, which fits into a cavity made in the lower fide of the handle^
where it fits on the axis. (See the Seition.)
B F. Thi