24 



JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 



speed, and type of burr. In all of these instances the differing values 

 can be accounted for by the fact that although the same kind of burr 

 was used, the stones were of different sharpness. 



It has been found difficult to duplicate in one test the surface of 

 stone used in another under the same conditions and obtain the same 

 production with the same power consumption. In fact, the pro- 

 duction factors vary greatly over short periods as a result of the vary- 

 ing attention given by the grinder man. On this account the power 

 and production data in the tables can be applied to commercial plants 

 only approximately. If a grinder is operating under the conditions 

 of any of the commercial tests shown in Tables 5, 6, and 7, however, 

 the data given will closely approximate the actual working conditions. 



TABLE 4. Qualitative and quantitative tests on jack pine Power consumption and 



production. 



1 Unscreened. 



