66 BULLETIN 343, U. S. DEPAETMENT OP AGRICULTURE. 



on three pockets, due to the need of filling and frequent binding of 

 the wood in the cells, the total power is used about 88 per cent of 

 the time. In other words, only 88 per cent of the power is being 

 used continuously. When two pockets on the same three-pocket 

 grinder are used to consume the total power and the third is kept 

 for surplus, as previously outlined, all of the power is in use approxi- 

 mately 93 to 95 per cent of the time. Here a saving can be made 

 and the efficiency increased withoat the installation or use of any 

 additional apparatus, simply by means of increasing the pressure 

 on the grinder cylinders, since this would be necessary if all of the 

 power were applied to two instead of the three pockets on that 

 piece of apparatus. Of course, this does not have as great bearing 

 on the increasing of efficiency when grinders are motor driven; but 

 in case of the direct connection to turbines it will be seen that it is 

 of great consequence. 



When grinders are motor driven, the most efficient utilization of 

 the power can be accomplished by the installation of a grinder-cylinder 

 pressure-regulating valve controlled electrically from the bus bars, 

 the idea being to increase the pressure when for any reason the power 

 consumption falls off. 



Not only does the increasing of pressure on the cylinders result in 

 the lowering of the horsepower consumption per ton, but there is at 

 higher pressures an increase in the quantity of pulp which can be 

 secured from a cord of wood, and this is another vital factor in the 

 study of the efficiency of production of mechanical pulp. In any case 

 it seems desirable to study carefully the grinding conditions, the speed 

 of the pulp stone, the pressure employed, and the character and grit 

 of the stone in use, since it is to these factors that practically all losses 

 and gains can be traced. The manipulation of the grinder and its 

 feeding and operation by the grinderman are also of prime importance, 

 since without careful watching the binding of the wood in the pockets 

 or some like difficulty may result in reduction of the production from 

 the grinder and also in the lowering on quality of the resultant product. 

 Even with careful watching there are times while the grinder is appar- 

 ently running satisfactorily when hardly three-fourths of the total 

 power available for its use is being consumed, due to the binding of 

 the wood in the pockets. 



FUTURE SUPPLIES FOR THE GROUND- WOOD INDUSTRY. 



Of the woods tested, Alpine fir, Engelmann spruce, lowland fir, 

 lodgepole pine, balsam fir, white fir, amabilis fir, noble fir, Sitka 

 spruce, western hemlock, and eastern hemlock all give promise of 

 being suitable for the production of news-print papers. Color is here 

 the chief consideration. An acceptable news-print paper can not be 

 made from such a dark-colored pulp as that of tamarack. Yet this 

 does not bar tamarack as a raw material for the ground-wood indus- 

 try; it will give a thoroughly satisfactory grade of yellow manila. 



