THE ESCAPEMENT. 507 



on which depends the success or failure of a campaign would 

 be wholly upset, half an hour too soon or too late meaning 

 failure. 



The Escapement. 



As we are on the subject of the pendulum and Escapement, 

 we will say a few words about the latter piece of mechanism. 

 It is here given on a larger scale than in the previous illustra- 

 tion, so that its action may be more easily understood. 

 Whether in watch or clock, the Escapement is exactly the 

 same in principle. 



First there is the escapement wheel, the circumference of 

 which is furnished with a number of very deep cogs, varying 

 as to the work which they have to do. Then there comes the 

 escapement itself, which swings on its pivot, and is regulated 



LARVA OF BURYIXG-BEETLE. ESCAPEMENT OF WATCH. 



in its oscillations by the pendulum. As it swings backwards 

 and forwards, it is evident that only one tooth of the wheel 

 can " escape/' and only that in one direction. 



"We can reverse a steam-engine, but the man has yet to be 

 found who can reverse a clock, i.e. enable it to continue going 

 in the opposite direction. The only mode would be to enable 

 one set of cogs to flatten themselves, so as to pass the escape- 

 ment, and a second set to start up in exactly the opposite 

 direction. Or perhaps there might be two parallel escapement 

 wheels, capable of being connected or disconnected with the 

 clock at pleasure. As, however, a reverse movement is quite 

 needless, no such invention seems to have been made. 



On the left hand is seen an example of the same principle as 

 chown in Nature. It represents a larva or grub of the Burying- 

 beetle. It has no legs available for locomotion, and yet it can 

 get along with tolerable speed. 



