120 



HOROLOGY. 



Escap*- 

 mcntt 



Description 

 of a clock 

 'scapement 

 by Mr Tho- 

 mas Reid. 

 PLATE 

 CCC1. 

 Fig. 1. 



Fig, Z. 



at the centre of motion of the pallets and balls would 

 be regarded by many as objectionable, from the belief 

 that oil is necessary to them. Oil docs not seem to us 

 in the least degree requisite, considering the very small 

 angle of motion which they would have; and we have 

 always thought, for the same reason, that oil was not 

 necessary to the pivots of such detents as were some- 

 times used in the detached 'scapcment. 



We shall now proceed to give a description of a 

 clock 'scapement, on the same principle as that of 

 Mude;e's in his marine time-keepers, which was put 

 to a very capital regulator or astronomical clock, 

 made some years ago by Mr Thomas Reid, for Lord 

 Gray's observatory at Kinfauns Castle. It had a 

 mercurial compensation pendulum, and its time of 

 going without winding up was forty-five days. The 

 great wheel, the second wheel, and the swing wheel 

 pivots, were run on rollers, three being put to each 

 pivot. Rollers were first applied by Sully to the ba- 

 lance pivot of his marine time-keeper, and have since 

 been adopted by Beithoud, Mudge, and others. They 

 have sometimes been used for clock pivots, but in 

 such an injudicious manner, that, in place of relieving 

 the friction of the pivots, they have at last jambed 

 them to such a degree, that the pivot could not at all 

 turn or revolve upon them. 



In Fig. 1. SW is the 'scapement or swing-wheel, 

 whose teeth are cut not unlike those of the wheel for 

 a dead beat, but not near so deep. P, P are the pal- 

 lets, the upper ends of whose arms at f, s are made 

 very thin, so as to form a sort of springs, which must 

 be made very delicate ; for, if they are any way stiff, 

 the force of the swing wheel will not be able to 

 bend them when raising up the pallets. In order 

 that these springs may have a sufficiency of strength, 

 and at the same time be as delicate as possible, they 

 are cut open at the bending parts, as may be seen at 

 Fig. 2. These springs come from a kneed sort of sole, 

 formed from the same piece of steel, by which sole 

 they are screwed on to cocks, which are attached to 

 the back or pillar plate of the clock-frame. The pallet 

 arms must be made very light and stiff, in order that 

 their weight may have the least possible load or bur- 

 den on the springs ; a, a are the arms of the pal- 

 lets, as represented in the front view, Fig. 1. and are 

 fully as broad as is necessary. Their thickness may be 

 made much less than this. An edge view of the pallet 

 arms is seen in Fig. 2. The acting parts of the pallets 

 at P,P, Fig. 1. should be made of such thickness as to al- 

 low room for inserting a piece of ruby, agate, or any fine 

 or hard sort of stone, the thickness of the stone be- 

 ing a very little more than that of the 'scapement 

 or swing wheel. Each of these stone pallets has a 

 sort of nib or detent for the wheel teeth, which is 

 left at the end of the pallet flanches, as may easily 

 be seen at the left hand pallet, Fig. 1. These nibs 

 are made for the locking of the swing wheel teeth, 

 and their use will be more particularly explained af- 

 terwards. On the back of the pallets are screwed to 

 ach a kneed light brass piece c, c, as seen at Fig. 1. 

 On the lower ends of these kneed pieces, the screws 

 d, d are put through, serving the double purpose of 

 adjusting the 'scapement, and setting the pendulum on 

 beat. The upper part of the pendulum-rod is com- 

 posed of a sort of frame, whose steel plates A, A, A, A, 

 Fig. 1. are represented as being contained within the 

 dotted circular lines; the thickness of these ring-sort 

 of plates is seen at A, A, A, A, Fig. 2. This frame has 

 three pillars to keep the plates properly together ; and 



though they are not represented in the drawing, yet 

 any one may readily conceive where their places ought 

 to be, and what should be their length and height. At 

 e, e, Fig. 1. is seen on each side the ends of a thin steel 

 plate, or traverse bar, which goes from plate to plate, 

 and is fixed in the frame. An oblique view of one of 

 them is seen at e, c, Fig. 2. In the steel frame plates, 

 there is a circular opening, as represented by the dot- 

 ted inner circle, Fig. 1. This opening must be of such 

 a diameter as to allow the swing wheel and the cock 

 which supports it to come freely through ; a part of. 

 the cock is seen at /, /, Fig. 2. the sole of which F is 

 screwed to the back 'of the pillar plate of the clock ; 

 the other knee K turns up to receive the pivot of the 

 arbor of the swing wheel, the pivot at the other end of 

 this arbor being supposed to run in the fore plate, or 

 in a cock attached to it, and is the pivot which carries 

 the seconds' hand. This description of the manner by 

 which the swing wheel is supported within the pendu- 

 lum, it is to be hoped will be sufficiently understood, 

 notwithstanding the want of a proper drawing of that 

 part. The swing wheel S W, and part of its pinion arbor 

 g, are seen edgewise at Fig. 2. ; also the arm a of one 

 of the pallets P, and its screw d bearing on the steel 

 bar c, c. At the point of contact between the end of 

 the screw d and the bar e, a small piece of fine stone 

 may be inserted into each bar. This will prevent any 

 wearing or magnetic attraction which might otherwise 

 take place, if the screw was left solely to act on the 

 steel bar ; for the smallest wearing here would in some 

 degree alter the effects of the 'scapement. In Fig. 1. 15 

 represents a part of the bar of the pendulum rod, 

 which is fixed into the lower part of the steel frame; 

 an edge view of this bar is seen at B, Fig. 2. At the 

 upper part of the steel frame is inserted a piece c, c, 

 Fig. Land 2.; in this piece the pendulum spring is 

 fixed, whose top piece goes into a strong brass cock, 

 which is firmly attached to the back of the clock-case, 

 or to a large stone pier ; the end of the projecting part 

 of this cock is seen at DD, Fig. 1, and a side view 

 of this part of it at DD, Fig. 2. The top piece of 

 the pendulum spring has a long and strong steel pin 

 through it, which lies in a notch made across on the 

 upper side and projecting part of the pendulum cock. 

 By this strong pin, the pendulum is suspended. In 

 the side of the pendulum-spring top-piece, is made 

 a large hole, so as to admit freely a strong screw, 

 the head of which is seen at E, Fig. 2. This 

 screw serves to pinch the top-piece and cock firmly 

 together, after the pendulum has been made to take 

 a true vertical position. This strong pin and screw 

 are not represented in the drawing, but the descrip- 

 tion which has been given will, it is presumed, easily 

 supply this want. In the pendulum spring h, h, Figs. 

 1. and 2. may be seen an opening in it, so as to have 

 the appearance of a double spring, as seen at/i, h, Fig. 2. 

 This opening is made to allow the spring parts of the 

 pallets *, * to be brought very near together, and this at 

 the bending part of the pendulum spring, so that it 

 and the bending part of the pallet springs should be 

 as it were in one common centre. A part only of the 

 cocks on which the spring pallets are screwed, is repre- 

 sented by k, k, Fig. 1. ; m, tn are the heads of the 

 screws by which they are fixed to these cocks. It 

 must be observed here, that the spring pallets are so 

 placed, that they should act on the line of suspension 

 and gravitation of the pendulum, which necessarily 

 brings the swing wheel to the place where it is ; no 

 verge, crutch, or fork are required ; the influence of 



Kicapc. 



men is. 



