CLAY MANUFACTURES. 701 
between a large sheet-iron shell and a wooden core. The shell is placed 
in position and the floor covered with clay 4 inches deep and tamped. 
The core is then introduced and adjusted so that 4 inches separate it 
from the walls on all sides. The clay is filled in small amounts ata 
time and tamped gently. When the retort is high enough the core is 
withdrawn by a crane and the mouth of the retort built by hand. The 
shell is then unbolted and removed in two pieces, and the finished 
retort is standing on its end. It is left to dry for several weeks in this 
position and is finally removed to the kiln to be burnt. It is put into 
an ordinary fire-brick kiln, and brick are piled around it to keep it in 
position without sagging. These retorts are cheap compared to the iron 
ones, and where in steady use and never allowed to cool they prove 
very durable. 
GuLaAss Ports. 
The third class of refractory material consists of the large pots in 
which glass is melted and worked. They are made by one large estab- 
lishment devoted to that specialty and by several of the glass-houses 
using them in the large way. 
The establishment referred to above is the Ohio Valley Pot Clay 
Co., of Steubenville, of which Mr. S. Brown is the superintendent. 
The clays used are, Ist, Gros Almerode, near Coblentz, Germany, for 
bond clay; 2nd, Christy clay, from near St. Louis, Mo., used for cal- 
cine and bond; 3rd, Blue Ridge, Missouri, clay, used for bond and 
calcine; 4th, Mineral Point, Ohio, flint clay, used as flint and calcine ; 
5th, old pot shells for calcine. 
The German clay is shipped as ballast in the holds of vessels and 
hence transportation costs but little, much less than the Missouri clays 
in fact. It is an excessively fine-grained and heavy clay, and is very 
plastic, making a better bond than any native clay. It comes in blocks 
9’’x6!’x6’, which have to be pared with a draw-knife, and then broken 
and inspected and all irony spots removed. No pieces larger than a 
walnut are allowed to go into the mixture. The work involved in getting 
the clay ready for use is excessive, and it is the opinion of those at the 
works that it is much overrated. It is an excellent bond clay, it is 
true, but its refractory properties are excelled by the Christy clay of 
Missouri. | 
These Missouri clays come in blocks, either ealcined or raw. They 
