316 A. Be Quinby on the Spiral of Archimedes. 
. On the subject of the injury which each engine is capable 
of producing, in case an explosion takes plaee, the committee 
are amply prepared to decide. 
. Respectfully, "he 
A. B, QUINBY. 
New-York, June 28, 1824. 
Arr XV.—On the Spiral of Archimedes ; by A. B. Quinny. 
Pror. Srtuman, “ 
R Sir, 
Tur subject of describing the spiral of Archimedes, by 
eans of an. instrument, was proposed at a meeting of the 
Mathematical Club in June 1822. A few days after the 
problem was given, I invented the instrument which the 
drawing you will receive with this letter represents. 
At the time the subject was suggested, the Club were not 
aware that an instrument for describing this curve had been 
among them the spiral of Archimedes. 
* 
Reference to the Plate. 
The upper drawing, Fig. 1, Plate V. represents a horizon- 
tal view of the instrument, standing on a table. The lower 
drawing represents a vertical view of the instrument, in the 
same positions The part cc’ is a cylinder, about which the 
thread this wound. ‘This cylinder is held permanent by the 
scew Sw, which passes through its centre. “The braces bd’ 
(of which there are four) enter, by small shoulders, into the» 
bars AL and DG, and support, at their upper extremity, the ~ 
inner ring rr’. ‘This ring, and the braces and cylinder, al- 
ways remain at rest.. The outer ring RR’, which carries the 
bars BB’, rests upon a shoulder of the inner one 77’, and 
may be made to revolve to the right, or the left, at pleasure. 
A section of these. two rings is seen at the point». The part 
