230 Mr. Cavendish on the Manner of 
on the support on which that end of the beam compass rests. 
If proper care, however, is taken in placing the wire perpen- 
dicular, no great nicety is required either in this or in the 
position of d. 
Another thing to be attended to, in making the wire bisect 
two scratches, is to take care that it bisects them in the part 
where they cut the circle ; for as the wire is not perpendicu- 
lar to the circle, except in very small arches, it is plain, that 
if it bisects the scratches at the circle, it will not bisect them 
at a distance from it. 
There are many particulars in which my description of the 
apparatus to be employed will appear incomplete ; but as 
there is nothing in it which seems attended with difficulty, I 
thought it best not to enter further into particulars, than was 
necessary to explain the principle, and to leave the rest to 
any artist who may choose to try it. 
It is difficult to form a proper judgment of the conveniences 
or inconveniences of this method, without experience ; but, as 
far as I can judge, it must have much advantage, both in 
point of accuracy and ease, over that of dividing by the com- 
mon beam compasses ; but it very likely may be thought that 
Mr. Tiioughton’s method, is better than either. Whether it 
is or is not, must be left for determination to experience and 
the judgment of artists. Thus much, however, may be ob- 
served, that this, as well as his, is free from the difficulty 
and inaccuracy of setting the point of a compass exactly in 
the center of a division. It also requires much less apparatus 
than his, and is free from any danger of error, from the 
slipping or irregularity in the motion of a roller ; in which 
respect his method, notwithstanding the precautions used by 
