CLAY MANUFACTURES. 689 
most important step in the process, and consequently the one in which 
the most variations are found. The different methods adopted are: 1st, 
the wet pan process ; 2nd, the dry pan and pug mill; and 3rd, the dry 
pan and wet pan mixer. ‘The use of these different kinds of tempering 
mills is not really restricted to any one kind of clay, though the use of 
each kind is widest in certain districts of comparatively uniform grades 
of clays. 
The wet pan process partially explains itself by its name. The 
clay is introduced into a large circular iron pan, which revolves con- 
tinuously on an upright axis. In the pan, and fixed ona horizontal axis, 
are two very large cast-iron wheels; as the pan revolves, the wheels are 
also turned by the friction between their circumference and the pan 
floor. The axis on which they rest is commonly made of two cast iron 
sections which are made to fork at the bolting ends and inclose the 
vertical axis of the pan. The hole thus made in the horizontal axis is 
at least 2 inches larger in diameter than the upright axis, so that the 
shaking of the machine does not cause friction. ‘The ends of the hori- 
zontal axis are fixed in slots in the timbers at the sides of the mill, so 
that when a charge is newly put in, the wheels have the chance to run 
over large lumps of hard matter, rather than being compelled to crush 
them at the first trial or break. 
These wheels are from 24 inches to 42 inches in diameter, from 8 
inches to 14 inches in width, and weigh from 3,500 pounds upwards; 
the average of the wheels from twelve of the best works in the State is 
4,400 pounds, and the highest weights used are 5,600 pounds. The pan 
itself is cast in one piece; it is'7 feet in diameter, and about 1 foot deep ; 
itis provided with a false floor which can be renewed at any time, so 
that the real pan floor lasts indefinitely. Motion is given to the pan by 
a strong system of gearing ; appropriate guides are used to keep the clay 
under the wheels and keep it well stirred up. Asa charge is dumped 
into the machine, the lumps cause the wheels to jump up and down 
with some vigor, but a few revolutions serve to reduce the clay to a 
finer state, and only a short time elapses until the material forms a 
homogeneous paste. The grinding lasts from 7 to 15 minutes, as the 
wheels vary in size and the clays work easily or not. In this reriod 
the plastic clays are in a state of complete .disorganization and are 
spread as a bond between the coarser particles of flint and calcine. The 
44 G. 
