' ON RAISING AND REMOVING M'EIGHTS. 205 



cases, if we wish to estimate the force with accuracy, we must add to the 

 radius of the axis half the thickness of the rope, when we compare it with the 

 a,rm of the lever. 



Sometimes the weight of a reservoir or bucket of water is employed for rais- 

 ing another bucket, filled with coals or other mateiials, by means of a rope or 

 chain, coiled round a cylinder or drum, or two drums of different sizes. This 

 machine is called a water whimsey : when the bucket of water has reached the 

 bottom, a valve is opened by striking against a pin, and lets out the water. 

 In a machine of this kind, employed in the Duke of Bridgwater's coal works, 

 the water descends thirty yards, and raises a smaller quantity of coals from a 

 depth of sixty. In such cases, supposing the action to be single, and the 

 stream of water to be unemployed during the descent of the reservoir,a consi- 

 derablepreponderance may be advantageously employed in giving velocity to the 

 weights, provided that the machinery be not liable to injury from their impulse. 



An erect axis or drum, turned by the force of horses walking in a circle, is 

 used for raising coals and other weights, and is called a gin, probably by cor- 

 ruption from engine: the buckets being attached to the opposite ends of a rope 

 which passes round the drum, and which is drawn by means of its adhesion to 

 the drum. One of the buckets descends empty, while the other is drawn up 

 full, and when the motions of the buckets are to be changed, the horses are 

 turned, or the wheels are made to impel the axis in a contrary direction, when 

 any other moving power is employed. 



When a ship's anchor is weighed, the cable itself would be too large to be 

 bent round the capstan ; it is therefore connected with it by means of an end- 

 less rope, called the messenger. As the messenger is coiled round the lower 

 part of the capstan, it quits the upper part; so that its place becomes lower and 

 lower, till at last it has no longer room on the capstan; it is therefore neces- 

 sary to force it up from time to time: this is called surging the messenger; 

 it is commonly done by beating it, and to facilitate the operation, the 

 capstan is made somewhat conical. It has been proposed to employ lifters in 

 different parts of the circumference, which are raised once in each revolution, 

 by passing over an inclined plane, with the interposition of friction wheels ; 

 a patent has been taken out for the invention, and it has already been intro- 



