wood either of these a divider will keep 
GRADUATION. 
' work, to send the ‘dial plates’ to the instrument maker 
- to be divided. eS Chapels tah ver 
Im straight line dividing, the operator has frequent 
o¢easion to divide lines to which none of his patterns 
will apply ; but there is an ne ape that he ought 
not to be unacquainted with, which will enable him, to 
a certain extent, to overcome this difficulty. Suppose 
he were required to set off French inches; that he 
knows the ion they bear to English inches, 
' which are ;/and, that he has marked off upon 
the scale to be divided, according to this —— 
e may di- 
the total — of French inches required : hi i 
. vide it from his English inch pattern. In this: case his 
work must be placed at an angle with his pattern. 
The proper inclination is readily found by trial; and 
as the square must run along the pattern, its blade will 
not be at right angles with his work. On this account 
he will have to perform two distinct operations. In 
the first he is to go through his work, only making 
slight notches in the hypothenusal, or inclined line, with 
the dividing knife; in the second, with the square ap- 
plied to the edge of the instrument which is to receive 
the divisions, he must, by seeing and feeling those 
- notches, cut the corresponding perpendicular strokes. 
ne, - , again, that Spanish inches were to be divi« 
Sakon same pattern: These are shorter than 
English inches, and will require but one operation. In: 
this case the square must be applied to the work, and 
the parts taken from the inclined pattern. We might 
here annex the rule for <a es angle of inclination, 
according to the proportion between the pattern and 
work to be divided, but we do not see its use. Those 
who handle the dividing-knife, especially in this de- 
ent of the art, are seldom versed in computation ; 
and as the lines upon the pattern, as well as those upon 
the work to be divided, are often remote from the edge, 
the angular point would seldom be*found upon either, 
_ and would often fall beyond the limits of the room in 
_ which the work is to be performed. We have already 
said, that cutting divisions upon metal is: laborious to 
' the hand ; but in ivory and wood it is not so; for in 
with a dexte- 
rous seamstress, a division for a stitch, for any length of 
time. The common carpenter’s rule is divided in this 
manner, and, small-as is the price of the finished in- 
strument, the dividing bears but a small p: ion to 
it., As a farther proof of the celerity:with which this 
kind of work is performed, it may be mentioned, that 
the writer of this part of our article being once in want 
of a good: piece of boxwood, exactly similar to: that of 
the common Gunter, but without slider or divisions, 
the artist who provided it charged sixpence more than 
he would have done for the finished instrument ; seas 
upon being asked the reason, gave a good one: “ the 
little order had put him out of his:common track.” ' 
When box; or any other kind of wood, is divided 
upon, the bur is first well rubbed off the divisions, and 
then the whole surface brought to a polish with a 
rush; the surface is next burnished by rubbing it 
hard both ways, in the direction of the grain of the 
wood, with a clean piece of old hat, which produces an 
agreeable gloss; and, lastly, to blacken the divisions, a 
mixture of powdered charcoal and linseed oil being laid 
on quickly, rubbed hard and cleared:away, finishes the 
In ivory, the divisions are, in the first place, 
Filed with a composition of black and: hard tal- 
~ low, or, which is rather better; of bees-wax: and olive 
351 
should be taken off with charcoal and water ; but in 
Common ° 
brass, the surface will have a much better appearance Gtaduation, 
if the finishing stroke is given with wet blue-stone, “~~” 
which is a very soft slate, ov the same substance that 
slate pencils are made of. Divided gold and. silver, 
however, look best when they receive their finish from 
the charcoal. The divided surface of all the metals is 
improved in appearance by being rubbed with the 
hand, after a little oil has been applied. No other black~ 
ing is required. 
In» dividing diagonal scales, the beginnings and Division of 
endings of the inclining lines are mark 
off with the diagonal 
dividing-knife from a pattern of equal parts, and after= li" 
wards those lines are traced by means of a straight 
edge, similar to the blade of the square. \ The knife 
being dropped into one of the marks, the ruler is 
brought into coritact with it, and-very nearly up to the 
other mark ; the thumb of the left hand is placed ex- 
actly over the ruler at the former, and the knife being 
dropped into the latter, the ruler is brought into con-~ 
tact with it, being turned under the thumb as on a 
centre. Instead of drawing the diagonal lines by hand, 
some use the bevel; and as by this the whole is done 
at once from the pattern, it would seem to be the more 
methodical way, but it requires a very nice adjust- 
ment to make the bevel agree with the square which 
had been previously used to draw the perpendicular 
lines. But which ever method is used, to do it with 
sufficient exactness is one of the most difficult opera+ 
tions of this department of the art. 
In the sector, and every other instrument, where the 
lines, which bound the length of the dividing strokes, 
are not parallel to the edge, so as to be traced with the 
gauge, the straight-edge and dividing-knife are used : 
The beginning and ending of the lines’ are set off in 
their proper positions by the spring-dividers: a'tool sd 
important in every branch of the art, that'a description 
of it might have sooner claimed a place. ; 
This is a’ kind of com 
steel. 
es formed altogether of fine The spring ° 
It consists of a’ circular bow and two legs, all in dividers, 
one piece, as represented in full dimensions by Fig. 5, PLATE 
Plate CCLXXVIII. 
pered, and, without danger of breaking, allows a motion 
of the points from the distance of about an inch to their 
contact. This is their range for use, but the elasticity 
is not exhausted until the points are separated nearly 
twice as far. At about three-fifths, reckoning from 
the bow, the adjusting screw has its place; It is at 
right angles with the legs when. the distance between 
the points is small, because short lengths are most com- 
monly taken: The screw, throughout its whole length, 
bas a fine deep thread-of about sixty tums to an inch; 
is fastened to one of the'legs’by a pin passing through 
it, and upon which ‘it turns’as on a centre, in order to 
obey the circular spring of the bow ; and the other leg 
is perforated, inorder that, atvevery distance of the 
points, it may pass freely throvigh it: A’ nut, the fe. 
male screw of ‘which is nicely fitted to the former, ‘by — 
its action overcomes the expansive force of. the bow; 
and regulates the distance between the points: But 
this nut does not come in contaét with the leg; there is 
interposed between them a saddle-piece, which exterior 
to the screw is made conical, and this is received by a 
hollow conical: part» in ‘the nut, which it exactly fits: 
The saddle-piece! next the leg is formed into a’ knife- 
edge, or sharp angle, which, resting 
‘the sh 
- bottom of a notch in the-leg, keeps th e former fen 
turning round with the nut, at the same time that it 
allows the angular change,as the distance of the poin 
is varied. . By this contrivance, freedom of action’ of 
the screw is preserved, and the possibility of its change 
The bow is strong and well tem- CCLXXVII 
