The Artist's Assistant, In the Study and Practice of Mechanical Sciences: Calculated for the Improvement of Genius. Illustrated with Copper-Plates — Birmingham, [ca. 1785]

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B, fweep the arch c c ; and with the fame diftance.
fetting one foot in A, fweep the arch d d; and thefe
arches will interfeft each other in the points gh;
which joined by a perpendicular, will interfect. A B
in the middle point i,

5 • Upon the end K of a given line, A B, to raife a per'
pcndicular. See Jig. VI.

Place one foot of the compaffes in A, and ex-
tend them to any point c without the given line ;
then fct one foot of them in c and turn the circle
cl e and A, and through d c draw the diameter dee,
meeting the circle in e : join A e, and that right
line is the perpendicular required.

6. To turn the circle through any three given points not in a
right line. See Jig. \ II.

Fix three points at any diftance you think proper,
as at A B and C, and join them by the right lines
AB and B C ; then by fig. V. bifeft the line AB
with the line d e ; which, done bile ft the line B C
with the line f e ; and from the center e, where
thefe lines meet, extend your compalfes to A. and
deicribe the circle A B C G.

7. To draw an oval. Set Jig- V III.

Draw a ?iven line A B. which divide into four
equal parts ; fct one foot of the compaffes at C. and
Irom that center defcribe a circle ce ;. with the fame
extent of compaffes place one foot in the center D,
and turn the circle ff; then with one foot flill in

D, extend
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