692 GEOLOGY OF OHIO. 
The details of these processes are all interchangeable, and various 
combinations of these different machines are seen. The older machine 
used for this purpose was the Cornish roller, which may still be seen in 
a dismantled condition around some works. ‘Tempering is always tested 
by the sense of feeling, and the workmen become very skillful in telling 
the degree of moistening necessary. 
The grinding once accomplised, the steps which the plastic, tem- 
pered clay is put through are much the same everywhere. Molding 
is the next operation to be performed. This is done either by hand or 
machine; the latter is only used in three or four places in thesState for 
making fire-brick, and indeed its use for making common brick is not 
much wider. ‘The process of hand-molding is very simple; and does 
not need description. 
The machine molders employed in Ohio are two, the Martin press — 
and the Baker press. They are essentially the same thing, only differ- 
ing in some technical points. The plan of their action is as follows: 
In a vertical box, three feet square, worksa pug mill just such as is used 
in the horizontal trough of the dry pan process; the clay is fed at the 
top; as it reaches the bottom of the chamber, the last arm of the pug 
mill is so shaped and so pitched as to expel a large wad of clay at each 
revolution. This mass is forced forward and downward so that it 
partially fills and wholly covers a mold with five chambers. A vertical 
eccentric from above works a vertical plunger up and down, which 
forces the clay into the mold and packs it tight. Its motion is so timed 
that the pug no sooner pushes the clay over the mold than it is driven 
home by the plunger. Another piston, working from in rear, pushes out 
the mold full of brick to the front and supplies a fresh mold. The full 
mold is stroked off with a flat board, and is carried away to be dried. 
The machines are designed to temper the clay and mold it as well, but 
this treatment is not found practicable in making fire-brick, as the mate- 
rial needs a longer preparation. This preparation consists, in one of 
the works where machines are used, of a dry mill with sereens and a pug 
mill mixer which delivers directly into the press top, making a very 
efficient mixing process. The capacity of these machines is large, vary- 
ing from 20,000 to 25,000 brick a day, as variously estimated, but in no 
case is their capacity put to the test in fire-brick making, as the room 
and other plant needed to justify such an output is nowhere found. 
The men employed on one machine are six—1 man to temper the clay, 
