166 GEOLOGY OF OHIO. 



The systems of drying, excluding open-air racks, may be classified as 

 follows : 



1st. Dry floors. 



2d.' Sewerpipe floors. 



3d. Compartment dryers. 



4th. Progressive dryers. 



Dry floors are the oldest means of drying used in the regular daily 

 production of a considerable quantity of bricks. The dry floor system 

 has grown up with the fire brick business in which it is almost univers- 

 ally used. 



The dry floor system uses a large fire proof floor, heated by a sys- 

 tem of flues underneath. The fires are maintained in fireplaces at one 

 side of the floor, and the heated products of combustion pass through 

 the flues, keeping the floor above hot, and unite in a draft stack, at the 

 opposite side of the floor. The bricks are put down in the floor on their 

 edge, or end, and sometimes are hacked up in open piles two or four or 

 six deep: usually, however, the floor is expected to hold the day's run and 

 must be emptied and filled once a day. The longer the floor is made, the 

 cooler the products of combustion will become, and the greater number 

 of bricks can be dried with the same quantity of coal. Dry floors are 

 naturally of all sizes according to the manufacturer's requirements: the 

 best ones are often made one hundred and fifty or one hundred and sixty 

 feet from fireplace to stack. Two hundred feet would not be too long to 

 get the best economy in the use of fuel. The roof over the dry floor 

 ought to be provided with ventilation, to allow of air currents through 

 the room. If other stories are added above the dry floor, the amount of 

 drying which can be done with the same fuel can be greatly increased, 

 as the heat arising from the floor is enough to give very good drying 

 power above. The material is placed on the floor by hand, and is taken 

 off again by hand. Sometimes it is necessary to move the bricks on 

 edge or alter their position during the drying which calls for another 

 handling. 



The cost of this system of drying is variable: where slack coal is ac- 

 cessible for little or nothing, it is a cheap plan. Where coal has to be 

 delivered by rail, it is not cheap. The moisture in this method is liter- 

 ally evaporated or driven out by heat. The effect of air currents assists 

 somewhat, but the air is given no adequate chance to do any work. 



There are objections to the use of this plan. The unequal heat of 

 the two ends of. the floors causes the brick to dry under different condi- 

 tions and to very different extent, in the same time. When a brick is 

 put down moist from the machine on a floor heated about 212°, the rapid 

 and unequal drying cannot help but do harm to the structure of the brick. 

 There is often a loss by bricks cracking and falling in two from this 

 cause, but the greatest damage comes from bricks whose structure is 

 weakened but not broken, and whose failure after being burnt and trans- 

 ported away for use causes more loss. 



