THE MINING AND QUARRY INDUSTRY I909 43 



also been introduced recently in some of the Onondaga quarries. 

 The main adit entries which serve for haulage are driven from 5 

 to 8 feet high and from 6 to 10 feet wide. The larger dimensions 

 refer to the mines near Jamesville where the gypsum is excavated 

 in large rooms and removed by 2-horse wagons that are loaded 

 directly at the quarry face. When the beds are only 5 feet or so 

 thick the rock is hauled out on mine cars attached to a cable. 

 The size of the rooms ranges up to 30 feet square. The overly- 

 ing limestone makes a firm roof and little artificial support in the 

 way of timbering or packing is required. 



The mines at Akron. Oakfield and Garbutt are entered by vertical 

 shafts from 50 to 70 feet deep or by adits. The underground work- 

 ings follow the pillar and room system but are more regularly planned 

 than those of the adit mines. The mines are often electrically 

 lighted, ventilated by forced draft and when necessary are 

 drained by pumps which raise the water from a sump at the shaft 

 bottom. Gas, electricity and steam are used for power purposes, 

 the former being supplied from the natural gas belt of Erie co. 

 Electric locomotives are in use for underground haulage, but in 

 most mines the cars are pushed by hand or drawn by mules. The 

 gypsum is drilled for blasting by either auger or percussion drills. 

 For hoisting from the shafts, a bucket elevator is employed at one 

 mine, while at the others single and balanced platform hoists are 

 generally used. Most of the mines are connected with the milling 

 plants by narrow gage railways. 



Manufacture of gypsum plasters. A part of the gypsum from 

 the mines and quarries is shipped in lump form to land plaster 

 mills and portland cement works. The latter are also supplied with 

 crushed gypsum which is shipped in bags. A small part is ground 

 into land plaster by the mining companies. The remainder of the 

 product, which represents the larger quantity, is converted into cal- 

 cined plaster in plants run in connection with the mines. 



The calcined plasters made by the mining companies belong to 

 the half hydrate class, their basis being plaster of paris. No anhy- 

 drous plasters like Keene's cement or German flooring plasters are 

 manufactured from the local gypsum. The preparation of plaster 

 of paris requires the two operations of grinding and calcination. 



Grinding is accomplished in several stages and if the kettle 

 process of calcination i> used the stages follow consecutively until 

 the material is reduced to a fine powder. The coarse crushing is 

 effected by jaw or gyratory crushers. From these the gypsum 

 passes into a " cracker " which resembles a coffee mill and reduces 

 the lumps to about pea ^ize. After this treatment the gypsum is 

 ready for charging into rotary cylinders, but for the kettle process 

 it is next run through a fine grinder of which there are many kind^ 

 in use. Buhrstones, the Sturtevant emery wheel, the Williams dis- 

 integrator, the Stedman disintegrator and roller mills all find appli- 

 cation for gypsum grinding. 



