CLAY MANUFACTURES. 691 
axis on which are fixed cutting arms which are arranged spirally, but at 
such a pitch that their action is slow in moving the clay forward. The 
tempering is done by merely adding clay and water, and allowing the 
machine to mix it up to a paste. It is mixed and quite thoroughly 
incorporated by the time it has worked the length of the trough, and it 
is then squeezed out upon the molding table. 
This process is one simply of mixing ; no element of grinding enters 
into it. It is not popular among clay workers, and is only applicable 
to certain kinds of clays ; those best suited are plastic clays, or mixtures 
of plastic clays, or at any rate mixtures involving but little flint and 
caleine. There is no particular district covered by this kind of a mixer, 
but in every district it is in some small use. 
The third method is the theoretically correct one of all in use, but 
it is the most expensive of all as well. The dry mill used is exactly 
like that before described, and is adjusted to deliver the ground clay as 
before into an elevator. This carries it up to the top of the building and 
delivers it upon a screen. ‘This screen is a box about 14 feet long, by 4 
wide, by 7 feet deep; the bottom of this box is made of sheets of per- 
forated sheet-iron, the holes about j,-in. in diameter ; the slant is about 
45°, so that whatever enters the screen is sure to leave it either by 
passing through or by running off at the end. That which escapes from 
the end is carried down by spouts to the dry mill and is re-ground, so that 
charge being introduced runs on until it is all through the sieve. That 
which pusses the sieve is caught by a cloth or board hopper bencath, 
and is conducted to the tempering mill or to the bins for storing. The 
clay which has been screened is beautifully fine and even. The tem- 
pering mill is on the same principle as the wet mill first described, but is 
of a larger diameter ; the wheels are arranged to turn instead of the pan 
frequently ; they are of larger diameter and less thickness than the wet 
pan wheels, and weigh usually 1,800 pounds each. The pan is provided 
with water and a charge is thrown in wet and ground briskly until as 
plastic as can be; by this course of treatment, the qualities of the clay 
are developed to the best possible effect. This process is ia favor in all 
the river works of Jefferson county, and at Mineral Point, and Hayden- 
ville, besides. Along the river, the clays used are as hard and rocky 
as sandstone when they are newly mined ; they are sandy and apparently 
non-plastic, but by this treatment develop into one of the best working 
clays in the State. 
