^ i n t r o d u c t i o n .
P L A T E F. Tbl hmik: which b fo fitted on the axis P P, that it carries the cutter and the
i - piece e c round wi t h it.
G. A Nut that fcrews the handle on Its axis, and Iceeps t h e c a t ter flat to the bell-metal
B B, when carried round by the handle.
oic—Isa bde nearly in fiaft of tb, fiSor of circk, pierccd through that part of the
b c l l - m e t a l which the edge of the cntter traverfes, and continued through the whole
l e n g t h of the ivory cylinder, truly parallel to its axis, and of an exaS equal w.dth
t h r c u i h o u t , till it terminates at the plate c. , , . .
H reprefents tb, ind of a fiec, „f mood of -wbkbßkes are to b, cut, and which ,s put
i n t o the cavity o o o •. int o the angular part of which it is gently prefled b y means of
K K. TOT braj, fcrews, which pafs thro' the ivory into the cavity » » and are made
t o prefs on the wood h by means of
L A key that fits into h o l l o w fquares made in the fcrews K K.
M Afcrew that faf f t s tbri the braß plate C. oppofi t e the middle of the cavity o o o;
a n d bv means of which the wood i is raifed t o the ctuter. This fcrew has for t y threads
t o an inch and its head being divided into twenty-five equal fpaces, .t .s evident that the
m o v i n g one of thcfe divifrons or fpaces wi l l m a k e the fcrew advance, and raife tbe wood h
i u f t o n e t h o t i f a n d t h p a r t o f aninch. . , , ,, .
N An ini,^ that points the divifions on the head of the fcrew (M! . The breadth of
t h i s index, f r o m the one fiducial edge to the other, fubtends a divifion and a hal f on the
h e a d of the f c r ew; b y w h i c h means half divifions as we l l as w h o l e ones m a y be accurately
( b i f t e d , and tbe 2000th, , j o o t h , .000th, y j o t h , &c. parts of an inch truly ell.mated
T o render the e f f e a of this fcrew the more certain, its point is turned round fo as toadl
v e r y near the center, and a piece of ivory (fee F i g . 3.) is careful l y fitted into the cav.ty
0 0 fo as to move freely therei n wi thout any lateral ftake, and to red on the end of the
f c r ew M. This piece of ivory a f t ing equal l y on ever,- part of the under furface of the
w o o d , will raife it towards the cutter with much more «r taint y than tf the fcrew aSed
i m m e d i a t e l y on it. Several f u c h pieces of ivory, of difierent lengths, (as reprefented by
F i . , ) ought to be fined to the inf t rument , fo as readi l y to fu, t the lengt h of any g.ven
p i e c e of wood. One piece, of the full lengt h of Fig. 3. muft have one l-ft'ou^h
fi o m the file, that pieces of oork, agaric, the pi t h of wood and fuch o ther foft fubf t anc c s ,
m a y be cemented on it with feallng w a x ; in which cafe they can be cut .nto flrces of a
d e t e r m i n a t e tbicknefs, as well as wood.
N o w if a piece of wood, whether round or of the (hape reprefented in the inftrument
a t ( i ) , and of whatever fize, be p u t into the cavi t y » . and gent l y preffcd int o the angular
o a t hereof by the fcrews K K, let it b e raifed towa rds the cut ter by means of tbe fcrew .M.
i f the handl e be turned to the right, the edge of tbe cutter will advance on the wood
a n d cut off fuch part as lies above tbe plane in which the edge of the cut ter moves : and
w h e n the upper furface o f the wood is thus rendered flat, llices m a y be cut of any required
t h i c k n e f s , according to the number of divifions that the fcrew M is made to advance.
I f the machine be made wi t h due care, it will readily cut a thoufand flices in an men ,
a n d if tbe edge be good and very wel l fet, flices may be cut that are no tnicker than the
, , o o t b o r even the 2000th part of an inch : but this requires management, much
d e p e n d i n g on the force wi t h which the fcrews K K pinch the wood.
I t is not an eafy mat ter to procure an edge fufficiently fine for the above purpofe; but
w i t h the very befl: pof f ible, thin flices have a tendency to curl up into rolls, fo as to be
u n f i t for the Mi c r o f c o p e , to prevent which, a very flcnder fpring is m a d e to p r f gently
o n that extremity of the flice where the incifion begins, fo as to keep it flat to the cut ter :
w h e n this fpring is fet to its p roper pofition, it is fixed to it hy the fmall finger fcrew
A n d left the aflion of this fpring ftionld deftroy the 11,ce after ,t is wholly cut, and m
p a f f i n g over tbe extremity of the cutter, the piece , . (which turns with the cutter) is
fixed by the nut G into fuch a pofition, that in paffing under the fpnng ,t raifts ,t and