Feb. 1907.] 



95 



Timbers. 



than is required to grind a block not so treated ; and the pulp produced is claimed 

 to be softer, stronger, and more desirable since the fibres are not broken up or 

 comminuted, but are more nearly in their natural condition, with their lateral 

 beards or filaments preserved, so that when re-united in the paper sheet special 

 toughness and tenacity are attained. 



In carrying out this method, 1 believe it is usual to immerse the solid wooden 

 blocks in a strong solution of lime, soda-ash, chloride of lime, or equivalent chemical 

 agent, kept boiling hot by the introduction of steam or otherwise, and adapted to 

 soften the blocks in readiness for grinding, and retain the blocks under treatment 

 from ten to twenty four hours, or until the liquid has had time to penetrate all parts 

 of the block, and the lateral adhesion of the fibres is so weakened that they 

 will readily separate by the attrition of the grinding stone without being 

 broken short or reduced to a mere powder ; and as the chemical action is most 

 rapid in the direction of the length of the fibres, it is desirable to cut the block 

 much shorter than is usual, or to form transverse saw-scarfs at intervals between its 

 ends, in order that the solution may readily penetrate from each end to the centre, 

 so as to loosen and toughen the fibres throughout the block. The pressure of steam 

 above the liquid in the tank tends to force the solution into all the pores of the 

 immersed blocks ; then remove the blocks from the tank and subject them to the 

 action of the grinders in the usual way, keeping a constant stream of water upon the 

 stone, and the disintegration will be found to be effected with great rapidity, owing 

 to the preliminary treatment received by the blocks, and also that no washing is 

 required beyond what results from wetting down the stone. The pulp produced is 

 claimed to be of superior quality, and as the blocks have absorbed only so much of 

 the chemicals as is beneficial to the fibre, it is iu condition for the successive steps in 

 the production of various grade of paper of special strength, and for numerous 

 other purposes in the arts. If preferred, however, this fibre may be mixed with hard 

 stock made of other material, such mixture producing paper or board of exceptional 

 toughness. 



voblter's machine for cutting or grinding wood and reducing it to pulp. 



The art of reducing wood to pulp by subjecting the same to the action of a 

 revolving stone is not a new one, machinery for grinding wood while a current of 

 water was applied to the stone having been patented in France by Christian Voelter 

 as early as 1817 (see " Brevets d'Invention vol. X., second series), and in England by 

 A^A. Brooman, of London, in 1853 (see " Repertory of Patented Inventions," for May, 

 1854, p. 410). A large number of inventions for cutting or grinding wood into pulp have 

 been patented ; but the enormous develepment of the paper making industry, and 

 the cheapening of paper during the last fifteen years are largely due to the general 

 ntroduction of the machine for disintegrating blocks of wood and assorting the 

 fibres so obtained into classes according to their different degrees of fineness, invented 

 by Mr. Henry Voelter, of Heidenheim, Wurtemberg, Germany, and for which in- 

 vention he received letters patent on August 10th, 1853, from the United States. 



In all the processes known or used prior to Voelter's invention the wood had 

 been acted upon by the stone in one or two ways, viz., either by causing the surface 

 of the stone to act upon the ends of the fibres, the surface of the stone moving sub 

 stantially in a plane perpendicular to the fibres of the wood ; or, secondly, by acting 

 upon the fibres in such a direction that they were severed diagonally, the surface of 

 the stone moving diagonally across the fibres. The first plan, in fact, made powder 

 of the wood— an obviously unsatisfactory result. The pulp had no practical length, 

 and on trial proved worthless, or nearly so, The second plan was carried out by the 

 use of a stone revolving like an ordinary grind-stone, the wood being applied upon 

 the cylindrical surface thereof, the fibres perpendicular or nearly so, to planes 

 passing through the axis of the stone and the point or locality where the griuding 



