ere Seta eee 
Original Letters of Dr. Franklin. 357 
right angle at H_ will necessarily describe the semi-circle, 
_and the point m will describe the curve of signs. In this 
way a circle is described by a square. 
ence by means of a Square Rule, without slits or pins, 
may an angle be trisected. Suppose EG (figure 4,) with a 
perpendicular part at H to be such a rule, the legs HE and 
HF being made of sufficient length. On the outward face 
of the rule EG mark the angular point formed by the out- 
ward face of the perpendicular part; and on the same 
face mark any distance from the angular point, (as Hm,) 
which is to be the radius of the semi-circle. With this in- 
strument in the hand, supposing the angle ACB (figure 3) 
to be the angle to be trisected and the semi-circle drawn, of 
which Hm is equal to the radius,—bring the point m to the 
side AC, and move it up or down on the said side of the an- 
gle until the faces of the square touch, at the same time, the 
extremities of the diameter, E and F. hen mark on the 
plane the angular point H, which will necessarily be in the 
circumference, and knowing which the angle may be trisect- 
d. proof is the same, as has been given in reference 
to figure 3. 
The rule may be formed of an entire piece of wood or 
metal, as figure 9. Let Hm in this rule be the radius of the 
semi-circle in figure 3. In any given angle, as ACB, there 
is but one position of the square rule, in which its point m 
shall touch the side AC, and the faces of the square, 
and HR, shail at the same time touch the extremities of the 
diameter, E and F ; and this position gives the point H in 
the semi-circle. And thus of any other angle. 
MISCELLANEOUS. 
acl 
Arr. XXI.— Original Letters of Dr. Franxury and others, 
addressed to the late Rev. Jared Eliot of Killingworth, 
Con. 
Remarks by the Editor. 
_ The late Rev. Mr. Eliot was highly distinguished (for the 
period in which he lived) by a knowledge of natural sci- 
ence, and by the successful application which he made of its 
Vou. IV...,.No. 2. “= 20 
