Bowles, Carington [Editor]: All Draughtsmen's Assistant, Or, Drawing Made Easy: Wherein The Principles Of That Art Are Rendered Familiar In Ten Instructive Lessons ... Explain'd by a great Variety of Examples from the most approved Designs, on Copper-plates, neatly engraved: With a suitable Introduction on the Utility of this Noble Art ; And Observations on Design, as well in regard to Theory as Practise (London, [ca. 1777])

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3- To draw a Line parallel to, or equidiftant from, another given Line E. F,
See Fig. IV. Plate IV.

Extend the CompaP.es to the Diftance of the Parallel required, then with one Foot
in any Point of the Line given, as in G, fweep the Circle H. I. Again, without
altering the CompafTes, fet one Foot in another Point, as in K. and defcribe the Circle
L. M. then rule the Line T. C. touching the outward Parts of the two Circles,
and you will then have the Parallel to the Line given.

4. To bifect or divide a given Line, CD. into two equal Parts. See Fig. V. Plate IV.

Having taken with your CompafTes any Diftance greater than half the given Line,,
proceed with one Foot of them in C. to defcribe the Arch E. E. and without altering
the Diftance, fetting one Foot in D, fweep the Arch F. F. and thefe Arches wilL
interfeci: each other in the Points 1. K. which joined by a Perpendicular will crofs

C. D. in the middle Point L.

5. Having three given Points not in a right Line, how to turn a Circle through
them. See Fig. VI. Plate IV.

Three Points being fixed as at D. E. and F. proceed to join them by the right
Lines D. E. and E. F. then by Fig. V. bifecT the Line D. E. with the Line G. H.
which being done, divide the Line E. F. with the Line I. K. and from the Middle
K. where thefe Lines center, extend your CompafTes to D. and fweep the Arcb

D. E. F. P.

6. A fure Way of drawing an Oval. See Fig. VII. PlateTV.

Divide the given Line G. H. into four equal Parts ; one Foot of the CompafTe3
being fet in I. defcribe a Circle E. E. Without altering the Extent of the CompafTes^
from K fweep the Circle F. F. then extend the CompafTes, one Foot in K, and fweep>
the Arch L. L. With the fame Extent fet one Foot in I. and turn the Arch M. M.
the Interfeci ions muft be united by a Perpendicular from N. to O. then proceed, with
one Foot of the CompafTes in N. to defcribe the Arch P. P. and with the fame Extent
of Compafies fet one Foot in O. and turn the Arch T. T.

7. Another certain Method. See Fig. VIII. Plate IV.

Rule a given Line A. L. then place one Foot of the CompafTes in C. and defcribe
the Circle F. F. then with the fame Extent of Compafies on the Line A. L. in the
fuppofed Point O. defcribe the Circle. P. P. and through the Points Q. Q; where the
two Circles interfeci:, rule the Perpendicular K. T. then, having one Foot of the
CompafTes fet in K, extend the other fo as to fweep the Arch B. B. to the lower Ex-
tremities of the Circles ; then, without altering the CompafTes* fet one Foot in T,.
and turn the Arch U. U. to join the upper Extremities.

By the preceding Examples it is evident that an Oval of any Form or Size may be
conftruc~ted at Pleafure, only obfeFving always to fet the CompafTes at an equal Dif-
tance from the given Line A. L, on the Perpendicular K. T.

Prafiical