COMMON THINGS CLOCKS AND WATCHES. 



hand is fixed must make sixty revolutions, while that upon which 

 the minute hand is fixed makes one. This would, therefore, be 

 accomplished if the two wheels worked one in the other, the one 

 haying ten teeth and the other six hundred. But it is not 

 necessary or convenient that the two wheels should thus be 

 immediately in connection. Two or more wheels or pinions may 

 be interposed between them, so that their relative velocities of 

 rotation may result from the combined relations of the numbers 

 of teeth or leaves in all the intermediate wheels and pinions. 



26. A wheel working in a pinion is represented in fig. 8. When 

 a very slow motion of rotation is to be converted into one many 

 times faster, or vice versa, this expedient is usually adopted. 



A wheel and pinion are often fixed upon the same axis at 

 more or less distance asunder. The pinion in this case may 

 drive or be driven by a smaller wheel at a distance from the first, 

 which is often convenient in clockwork and other machinery. 



Thus, in fig. 17, the wheel c drives the pinion d which is fixed 

 upon the axle of D, and drives it. The wheel D drives the pinion 

 e, which drives the wheel E on the same axle^and the wheel E 

 drives the pinion/, which drives the wheel 

 F, and so on. In this way combinations 

 of wheels and pinions may be arranged 

 so as to modify in any desired manner the 

 rate of rotation, and to transfer the rota- 

 tion from axle to axle according to any 

 proposed conditions. 



27. In all these cases the axles round 

 which the motion of rotation is produced 

 are parallel one to another. In many cases, as well in clockwork 

 as in other machinery, it is required to produce a motion of 



Fig. 10. 



Fig. 8. 



rotation round an axis at right angles to that upon which the 

 motion already obtained is produced. 



This is very simply and beautifully effected by either of two 

 expedients, one of which is called BEVELLED, and the other CKOWN 

 wheels. 

 20 



