GROUND-WOOD PULP. 47 
tion of certain grades of paper. The yield per hundred cubic feet is 
_ very high, approximately 2,950 pounds, or 550 pounds more than 
that from an equal amount of spruce. On the basis of a rough cord, 
however, this difference would be materially reduced, since white 
birch logs have a thick bark and are often crooked. 
Black gum (Nyssa sylvatica) yields a fiber that in many ways 
resembles that obtained from white birch. It is extremely short, 
' but forms a tougher sheet than coniferous fibers of the same length. 
if ' 
iy 
Considerable power must be expended to produce laps that can be 
Fig. 35.—Western yellow pine (Pinus ponderosa). 
taken off the wet machine satisfactorily. The pulp is not promising 
from a news-print standpoint, but could be used as a filler or mixed 
with pulp of a better grade. In color it is very white, ranking high 
mm this respect among the woods tested. Steaming the wood prior to 
_ grinding gives a stronger pulp, but not to the extent observed in the 
_ case of birch similarly treated. The yield of pulp from black gum is 
_ approximately 2,600 pounds per hundred cubic feet of solid rossed 
wood. 
