tom forming a diamond are all of
equal length. Nails or pins at A and B
fasten the instrument to the table, B
being so fixed that the distance from
A to B is the same as from B to C.
Then the pencil at D (if all is accu-
rately made and adjusted) will draw
the straight line shown.
[For other linkages that do the job,
see A. B. Kempe, How to Draw a
Straight Line (1877), reprinted by
Chelsea, 1953.--M. G.]
- DRAWING AN ELLIPSE
Answers 305DDraw the two lines CD and EF at right angles (CD being equal to the re-
quired length, 12 inches, and EF to the required breadth, 8 inches), intersect-EC~~~--------+---~~--~--~DFing midway. Find the points A and B, so that AF and FB each equals half the
length CD, that is 6 inches, and place your pins at A and B, making the length
of your loop of string equal to ABF A. Say the distance CA = x. Then, when