494 Coal Washing. [Oct., 



Another modification of the above process ought not to be passed 

 by without notice, for, whilst it embodies most of the leading prin- 

 ciples of Berard's machine, it has been so adapted as to produce the 

 greatest possible eflfect with the least practicable amount of water 

 and the smallest expenditure of power. The modifications in this 

 machine — which has been designed by a Mr. Edwards — will bo 

 sufiiciently well understood without an illustration, from the following 

 description : — The coal and water are admitted together through a 

 hopper on to the sieve, and instead of a piston, for keeping the water 

 in the machine in a state of agitation, a float is placed so as to rest 

 upon the surface of the water at a level below that of its height 

 over the sieve. This float is attached to the top of the cistern, and 

 the joint made water-tight by a leather flange, which admits of a 

 certain amount of vertical movement by the float. The motion is 

 given to the float by means of a three-throw cam ; as the cam 

 strikes the float, it is deflected, causing the water on the sieve to 

 rise, in the same way as with the downward stroke of the piston 

 in the machines already described. Indeed the float is in this 

 case a piston working on the water only without any cyhnder to 

 work in. 



Directly the cam releases the float, the head of water forces it 

 back, ready to receive the next stroke. Instead of making the 

 water act as the means of conveying the washed coal from the 

 machine, as in Berard's and most other modifications of that machine, 

 a set of scrapers gradually carry it forward, and finally push it over 

 the delivery end of the machine, and thus less water is required. 

 The speed at which the motion shaft is driven need be but one- 

 third that of Berard's, in order to obtain the same amount of work. 

 One of Edwards's machines, capable of washing about 50 tons of 

 coal per day, requhes so little power to move it, that, were it not 

 for the auxiliary crushing rollers, &c., which are generally indis- 

 pensable with a coal-washing machine, it might be worked by 

 manual power. 



Most coal-washing machines are arranged so that the washed 

 coal falls directly into a truck ready for removal to the cokeing 

 ovens, to the artificial fuel manufactory, or any other destination. 

 The coal thus caught forms, however, only a portion of what passes 

 through the washing machine. It constitutes indeed the greater 

 portion of it, and consists of all the larger pieces of coal, whilst 

 many of tbe smaller particles and almost all the coal dust are 

 carried away by the water as it flows oft'. In order to save this 

 fine coal, which, it is found, contains the smallest amount of im- 

 purities, and is therefore best adapted for the manufacture of coke, 

 it is necessary to form settling tanks through which all the water 

 from the machine is made to pass. So much coal, however, escapes 

 if due care be not taken, that it has m practice been found desii-able 



