1901 - 2 .] On an Instrument for Trisecting any Angle. 
i 
On an Instrument for Trisecting any Angle. By 
Jas. N. Miller. Communicated by Professor Chrystal. 
(Read November 4, 1901. Issued separately February 12, 1902.) 
The instrument is delineated in the accompanying drawing. It 
consists of two thin and flat pieces, A I F D and B H 0, of metal or 
other material. Those pieces are closely connected together by a 
cylindrical pin inserted perpendicularly to their flat surfaces through 
a cylindrical hole at C in each of them, which it fits, and round 
which they can turn. 
The piece A I F D has also a small cylindrical hole through it 
at A. The centres of the holes at A and C, and also the point D, 
are all in the same straight line A C D. The point B, the centre 
at C, and the border E 0 of the piece B H 0, are all in the same 
straight line B C E O. 
The line AC connecting the centres at A and C is bisected at 
I. The border I O of the arm I E is straight, and is perpendicular 
to the line A C. Therefore, A O is equal to C O, and A O C is an 
isosceles triangle. The point B is at the same distance from the 
centre at C as that centre is from the centre at A; in other 
