694 GEOLOGY OF OHIO. 
bustion is gradual, and after the floor is once hot, gradual heat is the 
kind wanted. Bricks placed on snch a floor dry in 24 hours from the 
tempered, plastic clay, to a state so hard that the hand can make no 
impression on them. When the bricks are about half dry ;they are 
pressed and again dried. The size of the drying floors used is very 
various, and is an index of the capacity of the works. At the works of 
the Scioto Fire Brick Co., at Sciotoville, the fine new floor recently put 
in is just 100 feet square and heated by 24 fireplaces and about 80 flues. 
Several establishments have floors 160x80 and 120x60. Lackjof drying 
floor constitutes one of the greatest obstacles to an increase of capacity 
of a factory. Air-drying is usually done in the second story over the 
ordinary drying floor. If the roof be tight the heat in the second story 
is quite uniform, and is strong enough to do quite rapid work. The 
temperature is often 100° or 120° naturally, and by using a slat work 
floor the capacity is largely increased. The kinds of ware adapted to 
an air-drying are large pieces which the heat of a floor can only attack 
on one side at a time, which is always done at a risk of cracking. 
The drying of machine-made brick is usually an air-drying process, 
but at the ordinary teperatures of the outside air as found under open 
sheds, though sometimes a plant is arranged inside the building. The 
drying of the brick is interrupted about half way through by the pressing. 
All hand-made brick, except the coarsest grades, are pressed. Machine- 
made brick never are. The pressing of the brick is done by a gang of 
workmen either four or five in number. The work of a press-gang is 
the same as the molding-gang, and is about 4,000 brick a day. The 
presses most widely used are those made by F. C. & D. R. Carnell, of 
Philadelphia; the other press in use is that of S. P. Miller & Son, also of 
Philadelphia. ‘They are both the same in principle, though different 
in detail. The pressing of the brick is done in a steel, brass-lined 
chamber with a sliding top, and a bottom which has the freedom to move 
up or down. By a strong application of lever power, the bottom is 
moved up, and the brick smoothed up into a compact, well-shaped body. 
The brand is usually put on the bottom plate of the press, and is thus 
impressed on the bottom of the brick as well. 
The pressure obtainable on such a press is not known to those who 
use them, if it is to those who make them, but it is ample for all pur- 
poses, There is little gain in subjecting a brick to powerful pressure ; it 
possibly increases its infusibility a trifle, but the effect is not perceptible 
