GRIMSLEY. | Technology of Gypsum. 101 
ing arms with disks fastened to them, in order to keep the mate- 
rial from burning on the bottom. These arms are fastened to a 
four-inch vertical shaft which is driven by a five-foot horizontal 
crown wheel, set in motion by a one-foot vertical pinion wheel 
attached to the power shaft. It takes from ten to twenty-five 
horse power to run this stirrer, and sometimes, if plaster is run 
too rapidly into the kettle, the resistance is sufficient to break 
the teeth or cogs from the pinion wheel. The stirrer makes 
about fifteen revolutions per minute. 
The kettle has two or four flues passing through, as shown in 
Figures 19 and 20. The heat comes up under the kettle as 
shown in lower part of Figure 19 and passes through the air 
space at side and then through the flues out into the air space on 
the other side and out through the chimney. 
ie 7 
St OSC SAS Sess SESSEEOSNION NS ORDA ae CAEL ARAN Oa doe CURR AOA SOREN ODDO CODCOD NNN” 
Fie. 20. Gypsum Calecining Kettle (outside). 
