38 



BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE. 



spruce. All the substitutes, however, with the possible exception 

 of noble fir and amabilis fir, required the use of more power per ton 

 of pulp. Also, while a good grade of spruce 

 pulp can be produced under widely varying 

 conditions of grinding, the best results were 

 generally obtained from the other woods when 

 the stone was somewhat dull, the pressure high, 

 and the speed of grinding rather slow. 



THE FIRS. 



Fig. 24.— Red fir (Abies mag- 

 nified). 



The firs tested were balsam fir {Abies bal- 

 samea), red fir {Abies magnified), white fir {Abies 

 concolor), amabilis fir {Abies amabilis), alpine 

 fir {Abies lasiocarpa), lowland or grand fir 

 {Abies grandis), and noble fir {Abies nobilis). 



A good sheet of pulp can easily be obtained 

 from balsam fir if the wood is in a green state. 



Such pulp is as light in color as, if not lighter than, spruce, and a 



fairly sharp stone can be used in grinding it. Seasoned wood, how- 

 ever, usually shows 



decay and insect at- 

 tack, and it is prac- 

 tically impossible to 



grind it into pulp 



which will not contain 



many shives and be 



somewhat soft. The 



yield from balsam fir 



is about 1,910 pounds 



(bone-dry pulp) per 



hundred cubic feet of 



solid rossed wood, or 



approximately 4 9 



pounds less than the 



yield from an equal 



quantity of white 



spruce. 



Red fir, like balsam, 



is easily ground to a 



pulp satisfactory for 



news-print purposes. 



It required, however, 



more power per ton of pulp, due possibly to the fact that the wood 



used in the experiments was of such a large diameter that it had to 



Fig. 25. — White fir (Abies concolor). 



