50 THE IRON ORE DISTRICT OF EAST TEXAS. 



ceived by a cone conducting them into the collecting room. The whole is 

 placed in a square oven, the fire gas of which enters the drying apparatus 

 above described and passes through the coal from plate to plate through an 

 opening below, on its way to the chimney These ovens are profitably used 

 only in the drying of lignites poor in bitumen, requiring a high temperature. 



An apparatus in which the drying of the brown coal is effected with super- 

 heated steam is of similar construction and possesses the same system of 

 scrapers to move the coal over the plates. It differs, however, from the 

 former in its double walled plates resting on four hollow columns, of which 

 two serve to conduct the steam between the double walls of the plates, and 

 the others constitute canals through which it passes on its way to the chim- 

 ney. A mantle of sheet iron enclosing the oven keeps the working room 

 free of dust. This drying apparatus can be used with advantage for almost 

 all varieties of brown coal except those requiring a high temperature. 



An oven used with great advantage in some instances consists of a large 

 revolving drum, placed in an oblique position and containing a number of 

 tubes. The axis is hollow and conical towards the center and its mantle per- 

 forated. The steam from the engine enters its upper part, passes through 

 the apertures into the interior of the drum, and after passing around the 

 tubes escapes through the lower opening in the axis. A cone is placed' 

 above the higher part of the drum from which the coal enters the tubes and 

 gradually slides, pushed by the revolutions and oblique position of the ap- 

 paratus, towards the lower front, falling into the collecting room. 



Finally, a system frequently used consists of a peculiar arrangement of 

 sheet iron of an interrupted form, over which the coal slowly slides down. 

 The hot air used with this method is warmed by the escaping steam of the 

 engine and forced through the coal, entering the apparatus below and es- 

 caping above into the chimney. Sometimes these ovens are also supplied 

 with a system of tubes through which steam passes, aiding the drying pro- 

 cess. The above short review shows clearly that the main difficulty in the 

 European, and especially German, briquette manufacture 'is the drying of 

 the lignites, and notwithstanding the numerous and costly experiments which 

 had to be conducted to overcome this obstacle, this industry has flourished 

 and has enriched the people engaged in it. 



PRESSING THE BRIQUETTES. 



The pressing of the briquettes, though a simple process, has to be con- 

 ducted in accordance with the quality of the lignites, a coal of larger grain 

 requiring less pressure than one of dusty consistency. The briquette ma- 

 chines resemble the well known pressed brick machines of this country. As 

 mentioned before, the Exter press, with about eighty revolutions (eighty 



