134 GRAHAM'S ESCAPEMENT. 



Construction ^^^^^^ ^"^ ^"^ ^^^^ ^^ *h^t proportion; thus, suppose flie 



of the wheel number intended to scape over was* 9, double of which is 



and pallets for 13^ to which add one, makes 19 ; then work it thus : 



Graham 9 dead -r^ 



beat. I^ 60 gives 360 what will 19 



19 



6,0)684,0 



1 14 which is the exact space 

 taken up by nine teeth and a half, half of which is 57 ; 

 then on the circle already drawn set off on each side the 

 line A B, from an exact line of chords, 57 degrees ; from 

 which points draw lines to the centre of the circle, then 

 on these points where they intersect the circle, erect per- 

 pendiculars, and prolong them till they intersect in the 

 line A, and this intersection is the centre of motion for 

 the pallets, from which centre draw the arch C C, 

 through the circle where it is intersected by the lines 

 from the centre, or those points where the 57 degrees 

 fall; the arch thus drawn is the receiving and leaving 

 pads of the pallets, the inclination, or inclined plane of the 

 pallets to form an angle of 60 degrees with the lines 

 drawn from the centre of the wheel to its circumference; 

 thus, from the point (as a centre) where the arch C C 

 that forms the pallets intersect the circle, draw half a 

 circle D of any size ; then for the receiving pallet E, set 

 off from the point/ an arch of 60 degrees, which will 

 fall on the circle at g^ then from that point, and the in- 

 tersection of the arch C C with the circle B, draw a line, 

 which gives the inclination of the pallet E ; and for the 

 leaving pallet G, make a similar circle, and from the 

 point h set off 60 degrees, which will fall on the circle at 

 trt, and draw a similar line as before, which gives the in« 

 clination of the pallet G. 



Investigation 



