Ttt 



HOROLOGY. 



HOBOLOOT. 



c*ues the barrel to revolve in a contrary direction to that in which it 

 moved whilst winding up, and thereby gives motion to the fusee, and 

 with it the fusee-wheel and the rest of the train. Fi-j. 14 represents 

 the barrel and fusee, with the chain attached. Fig. 15 shows the 

 balanoe-wheel, balance, and verge, with thejiair-spring attached to it. 



: .11, 



I 



Fig. 15. 



Uttails of Vertical Watch. 



We shall now notice the better kinds of watches, the peculiarities of 

 which mainly depend on the escapement. 



The Duplex Eicaptmenl is shown infy. 16. A A is the scape- wheel, 



Duplex Etcaprmcnt. 



1, 2, 3, being the teeth of repose, and a, b, c the teeth of impulse, 

 woich are triangular, and stand perpeudicukir to the plane or surface 



the wheel C D, the impulse pallet, fixed u)x>n the arbor of the 

 balance, and standing just above the surface of the wheel A A, receives 

 ill motion from the teeth a, b, r, &c. After the tooth a has passed 

 the pallet c D, the tooth 6 comes in contact with a small roller made 

 of ruby, and placed on the lower |u-t of the axis of the balance, where 

 it remains till the balance is brought back by the balance-spring to 

 such a position, that the notch, shown by the dotted line in the ruby 

 roller, will allow the tooth 1 to enter it, and thereby pass the balance- 

 arbor, or escape, which it does by the wheel A A being constantly urged 

 in the direction from 8 to 1. As soon as tooth 1 escapes from the 

 notch, tooth 6 gives a fresh impulse to the pallet c D, and the act of 

 escapement in thus repeated ; the wheel moving forward one whole 

 tooth, and the balance making two vibrations for each impulse given 

 by the upright teeth. 



Another effective variety, the I: err tteaptmeM, is shown in Jig. 17. 

 The lever / is placed on the pallets in .1 ]wition at right angle** to that 

 in which it is usually placed in a watch, by which means wo think the 

 principle will be more apparent to the general reader. A A is the nape- 

 wheel moving in the direction of the arrow ; b d the pallets, whom centre 

 of motion is e. To the pallets is pinned the lever I. in which is the 

 gunrd-pin e, pointing upward* from the lever I ; the roller / is fixed on 

 the axis of the bilaoce, and stands just above the lever /, having a piece 

 cut off from its circumference to allow the guard-pin e to pom and repass 

 the roller, which it does when the escape taken place, o is a ruby pin fixed 

 in the roller, and pointing downwards through the notch in the end of 



the lever /. When the balance is quiescent, the pin a is hi the notch in 

 the end of the 1< vcr 1. an 1 the guard-pin e in the position shown in the 

 figure, where the tooth 1 acts on the pallet 6, which causes the balance 

 to vibrate. The guard-pin t proceeds a short distance to the right of 

 its present position, and th lever is prevented from returning by the 



Fif. 11. 



' 



Lever EseapemcaU 



guard-phi t coming in contact with the circular edge of the roller. 

 When an impulse is given by a tooth to the other pallet d, the lever 

 / impels the ruby pin o to the left hand, where precisely the same 

 effects take place with regard to the guard-pin r, Ac., as have been 

 already described. If the pallets 6 and d were of the form shown by 

 the dotted lines (which are supposed to be circular arcs concentric 

 to the centre of motion e of the pallets), it is evident it would be a 

 perfect dead beat, like the clock escapement previously described; 

 but in order, after the escape has token place, that the guard-pin 

 e may be retained at a small distance from the roller, that part of 

 each pallet on which the tooth rests when it falls on the pallet is 

 taken off, as shown in the figure ; and as the faces of the wheel-teeth 

 are considerably undercut, the wheel advances a small distance, after 

 having fallen on that part of either of the pallets which is within 

 the dotted line. This further advance of the wheel draws the 

 down towards the centre of the wheel, and thereby keeps the guard-pin 

 e at a slight distance from the edge of the roller/. As soon a* the 

 balance has performed so much of the returning vibration as to bring 

 the ruby pin o into the notch in the lever, the momentum of the 

 balance, acting through the medium of the ruby pin o upon the lever, 

 moves it a short distance, and thereby lifts the pallet outwards from 

 the centre of the wheel and unlocks it. During this unlocking the 

 wheel retrogrades (before it can get upon the face of the pallet to give 

 a ficsh impulse) just as much as it had previously advanced after 

 falling on the pallet By this retrograde motion the tooth gains the 

 inclined plane or face of the pallet, and gives a new impulse ; and the 

 .-auir process is repeated by another tooth on the opposite pallet, pp 

 arc two pins, called banking-pins, against which the lever / presses 

 when locked, and which prevent the guard-pin t from being drawn 

 too far away from the edge of the roller /, when the locking takes 

 place. 



In jiy. IS ia shows a Kariamlal acapemetl. ABO represent* tiw 



IlorisunUl hjcipcnwut. 



balance ou its axis, which is a hollow cylinder c, cut away in its ciremii- 

 ference. The teeth of the escape-wheel form a series of inclined 

 planes, which stand on stem* perpendicular to the plane of the wheel ; 

 he inclined part forming the extreme edge or acting-face of the tooth. 

 These planes coming in contact alternately with the two edges of that 



