244 — ANNUAL REPORT 
This furnace can be readily used for high temperatures. The time 
required to make a burn, including the heating up, is about two hours, 
A hole at the= levels ore thes sitonenplare permits of introducing the 
small amount of paper and wood necessary to start the flame, by heating 
the pan. By removing the pan, bricks and broken pieces, this furnace was 
also used for burning with coke, which, though not as convenient and 
rapid, was accomplished successfully. An opening, closed by a plug, 
beneath the plate, permitted of withdrawing the fine dust and ashes which 
filtered through, while the coal clinkers were removed through the hole 
at the level of the plate. The coke was charged through a door just 
beneath the grating supporting the cement clinker. In firing with coke, 
it was found best to use a good grade of firebrick, since the magnesite 
bricks, even those made of the magnesite-cement mixture, proved to be 
too brittle and friable to withstand the sudden cooling on opening the 
door. The layer of coke must be kept as thick as possible. 
An updraft kiln of the Ohio State University Ceramic Department 
was also used successfully for burning ordinary cement mixtures, a tem- 
perature of cone 12, 1370° C. being attained without difficulty. For the 
usual testing work where contamination with the ash of the fuel is 
not objectionable, the ordinary type of the shaft furnace, similar to an 
assay furnace, without a muffle, the draft being furnished by a stack, is 
quite sufficient. It is simply a rectangular shaft, with a grate and ash-pit 
bottom. Wood is placed on the grate and on top of that a heavy layer of 
coke. Cubes of cement mixture are charged on top of the fuel in a thin 
layer, followed by more coke. In this manner alternate layers of coke and 
cement are arranged. 
Professor Campbell, of the University of Michigan, used, very suc- 
cessfully, a small rotary kiln, consisting of an inclined iron pipe, 8 inches 
in diameter and 32 inches long, which was lined with four sections of a 
hard burnt magnesite pipe, whose inside diameter is 3 inches. The fur- — 
nace is rotated by means of a % horsepower motor and makes one revolu- 
tion in I minute and 25 seconds. It is fired by means of a Hoskins gaso- 
line burner and air is supplied at about 50 pounds to the square inch. On 
measuring the temperature by means of the Chatelier pyrometer, it was 
found to be the highest about 6 inches from the lower end, it being 
-tsoo° C. After the kiln is heated up, the mixture is charged 
and with an inclination of 6° takes 25 to 35 minutes to pass through 
the kiln. During the first hour 1,500 to 1,700 grams are fed; after the 
first hour, 1,000 to 1,200 grams per hour; this means 600 to 700 grams of 
clinkered material per hour. 
For research work, electrical furnaces are extremely useful, allowing 
of quick firings and absolute control of the temperature. Platinum foil 
