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caused by washing is most clearly shown by the following table:

The cost of such washing, including interest, superintendence, etc., was from five to six cents per ton of washed coal at Wolfsbank and Brückenberg.

There are a variety of forms of apparatus in use for washing the coal, and each has its special claim for excellence, or its application to a particular character of work, one of the largest plants of this kind being that of the briquette factory of Couillet, in Belgium, which has a capacity of 1000 tons in ten hours.

The drying of the washed coal is usually done by means of centrifugal machines, which make 300 revolutions per minute, and have a capacity of three tons per hour. At other localities the drying is carried on in drying towers.

The separation and cleaning of coal in the dry way is also in successful operation at several localities, and while the cost of installation of the plant is somewhat greater than in the washing apparatus, the cost of cleaning is about 20 per cent les. There seems to be some advantage in it, since the coal is worked with dry air and the cost of drying after washing is saved entirely.

BRIQUETTES WITH BOND.

The greater quantity of briquettes which are made with bond are manufactured from the slack of coal with the addition of coal tar pitch. The earthy brown coal of Germany is not well adapted for the manufacture of briquettes of this kind, and while the pitch coal and glance coal of Austria are well suited for the purpose, the demand for the coal, small as well as large, is so great that up to the present time there have been few plants erected. Where they have been, however, they are in successful