492 Coal Washing. [Oct., 



Attempts have also been made to dispense with the necessity for 

 stirring the coal whilst being washed, by placing a series of projec- 

 tions across the bottom of the trough, which, acting as submerged 

 weirs, were intended to give the water an undulatory motion; 

 this, however, is not sufficient for the purpose, and experience has 

 shown that a more sudden and violent action of the water is 

 necessary in order to effectually separate the coal from its impurities. 

 The objections to this form of coal- washing machine are that, whilst 

 it requires a larger supply of water for the purpose, the coal is not 

 so thoroughly washed as in other machines ; and tbat whilst the 

 result is still only comparatively purified, a large amount of coal is 

 probably wasted, by passing away with the other matters down the 

 outlet valve before referred to. 



The most generally adopted plan of coal-washing machine at 

 present in use is that shown in the Plate accompanying this 

 article. It is a modification of a French machine, the invention of 

 one M. Berard, and somewhat of the form of that first introduced 

 into this country by Mr. Morrison. The illustration represents 

 not only the washing machine itself, but the steam engine and other 

 auxiliaries employed in connection with it. In this machine the 

 coal, after passing between crushing rollers, is conveyed by means of 

 a " Jacob's ladder " into a hopper, or shoot, down which it falls into 

 small rectangular troughs, at the head of each of which a current 

 of water enters which carries the coal away, and deposits it on a 

 wire, or perforated copper sieve. Beneath this sieve is a hopper- 

 formed chamber filled with water in communication with the bottom 

 of a cylinder in which a piston works at the rate of about 100 

 strokes per minute. The motion of this piston agitates the water 

 in the " bash," causing it alternately to rise and fall on the sieve. 

 The coal on the sieve is thus kept in a constant state of motion, 

 being lifted up by the water as the piston descends, and falhng 

 again with its upward stroke. By this constant elevation and 

 resetthng, the heavier particles, which constitute the impurities in 

 the coal, fall to the bottom and form the lowest stratum on the 

 sieve; whilst the pure coal, after the space above the sieve is once 

 full, is carried over the lip of the machine with tlic escaping water, 

 and falls down a shoot into a truck placed there for the purpose of 

 receiving it. As soon as any shale, or other impurity, is seen to 

 pass over with the coal, or when the space over the sieve becomes 

 filled with foreign matter (which may be readily ascertained by the 

 attendant taking a small quantity out to examine it), the valve at 

 A, Fig. 2, is raised by means of a screw, or weighted lever, and 

 the accumulated impurities are allowed to ])ass into the lower part b, 

 from which they are subsequently removed by means of the valve c 

 at the bottom of the machine. The pistf)n wt)rks in i\\e chamber d. 

 It should have a stroke of not more than from 2 to 2^ inches, and 



