WOOD PULP AND PAPER 31 



4. Adequate power. Most of the pulp mills have hydro-electric 

 power developments in connection with them. 



5. Accessibility to a good fuel supply. 



6. Adequate transportation facilities for both the shipment of the 

 raw material to the mill and the movement by rail or boat of the products 

 to the consuming market. 



THE MANUFACTURE OF MECHANICAL PULP 



In the manufacture of ground wood or mechanical pulp the wood 

 fibers are torn apart by mechanical abrasion, by compressing the billets 

 of wood against a rapidly revolving grindstone. Spruce is better adapted 

 for this process than any other wood. Other species used are pine, bal- 

 sam fir, hemlock, aspen, poplar and a few other woods, but a very large 

 per cent (about 85) of the total amount is made up of spruce. In 1916 

 1,524,386 cords of wood were reduced to pulp by the mechanical process. 



The cheaper grades of paper, chiefly news print, are formed of pulp 

 made by the mechanical process. The intercellular substances of wood 

 fibers, chiefly lignin, resins and tannins, are not removed, as in the chem- 

 ical processes, which dissolve out the undesirable constituents and leave 

 a substance which is largely pure cellulose. In the mechanical process 

 the wood is ground to a fine pulp. 



Preparation of the Wood. 



The raw material if it is brought to the pulp mill in the log form is 

 taken out of the booms and log storage in the river or mill pond and is 

 carried up into the mill by means of a jacker chain which usually leads to 

 a series of live rolls. The logs are then reduced to a uniform length 

 usually 24 in. Very commonly, pulpwood comes to the mill in the form 

 of 24-in. bolts, either in the peeled or rossed condition or with the bark 

 still on the wood. The logs are reduced to the bolt length by means of a 

 slasher made up of a series of circular saws against which the logs are 

 conveyed. In some mills a large, circular, cut-off saw called a " drop- 

 saw " is used. In the latter case the logs are brought into position by 

 means of log rolls and the saw lowered until they are cut off to the 

 proper length. 



One type of six-saw slasher has a capacity of handling 8000 logs up 

 to 14 ft. in length every 10 hours. 



Barking. 



If the bolts or logs come to the mill in the unbarked state they 



