172 KANSAS UNIVERSITY QUARTERLY. 
ence than any other consideration in determining the outline used. 
Consequently, as a rule, any one irregular curve is suitable for 
only a limited use. So that a draftsman must have a number of 
these with him, and often must try his whole assortment several 
times before being able to fit a comparatively simple curve. The 
exasperating nature of this task is only appreciated by those who 
have had some bit of curve on an important drawing to put in with 
great accuracy. 
The Universal Drawing Curve. 
The very great desirability of having one instrument which can 
be used easily for all plottings within reasonable limits of size sug- 
gested the design of the Universal Drawing Curve, which is the 
same instrument, some of the mathematical possibilities of which 
have been noticed. Fig. 14 shows a photograph of six sizes of the 
instrument as now made, reduced about one-fourth size. Any de- 
sired size may be made, possessing the same characteristics, by 
simply varying the constant in the plotting of the spiral. 
Continued use for a long time under a very great variety of con- 
ditions shows the instrument to be truly a Universal Curve. It 
possesses such a wide range of curvature, varying, as it does, from 
nearly a straight line down to a very short and almost circular 
curve, including all degrees of curvature ever needed, that with one 
of these instruments it is a simple matter to fit any kind of plotting 
within a reasonable limits as to size, to allow for which the instru- 
ment is made in this series of sizes. To do this it is only necessary 
to turn the instrument on the drawing till the curve of the spiral 
coincides with three or more points of the plotting, draw a line 
through these points, and then turn the instrument a little farther 
until a small portion of the line already drawn and several more 
points are fitted. In this way the line is quickly prolonged with- 
out the usual exasperating work of picking up and turning over a 
whole assortment of curves in order to fit a small bit of curvature 
at a time. 
Either of the medium sizes, c—=100, c=120 or c=135 is admira- 
bly adapted to average work. The size c=60 is for exceptionally 
small work, and c=180 and c=225 for very large work. Use 
shows that any one of these instruments will replace a whole as- 
sortment of the old curves and enable a draftsman to do his work 
quicker and better. 
