Part III.] Raitt : Bamboo as Material for Paper-pulp. 5 
prevented from floating, bamboo floats considerably longer than spruce 
in spite of its greater specific gravity. The greater lightness of spruce 
permits a much larger proportion of its mass to be buoyed up out of 
contact with the water, but the whole of the buoyed portion sinks under 
the surface much sooner than the smaller buoyed portion of the bamboo. 
The capillary air in the latter resists soakage longer and it cannot wholly 
sink until this air has been expelled and its place taken by water. In an 
experiment made with equal quantities of bamboo and spruce chips, 
thrown into open vessels containing equal quantities of NaOH liquor, 
and boiled, the spruce took one hour to wholly sink under the liquor, 
while the bamboo required two and-a-half hours. When forcibly sunk 
and held under the surface by a perforated plate and then boiled, bam¬ 
boo continues to throw up air bubbles for two hours. In a closed 
digester the conditions for getting rid of this air are no better than in an 
open vessel and chips have been found to still hold air after 2J hours’ 
digestion. Therefore, in addition to the mass and colloidal resistance 
common to all materials, we have in bamboo a resisting force peculiar 
to itself, since complete penetration of the tissues by the chemical sol¬ 
vent cannot take place until the whole of this capillary air has been 
ejected. Where means are not adopted to force the whole contents of 
the digester under the liquor,—either by using rotary digesters or 
screens in stationary ones, the last chips to sink will invariably be 
found badly digested, not only because they get two hours less treat¬ 
ment than the bulk of the contents, but because they fall into a liquor 
already weakened by two hours’ previous work,—and even when the 
whole contents are brought under liquor from the start there will be 
some irregularity in result between the outer and inner tissues of the 
chip unless liquor of greater strength is used than would be necessary if 
rapid penetration were secured, so as to ensure it still being of suffi¬ 
cient strength when the interior of the chip is ultimately reached. It 
seems probable that this capillary air is one of the reasons, if not the 
chief cause, of irregular digestion hitherto complained of. 
6. Spruce is almost equally resistant in all directions to mechanical 
disintegration, but being a soft wood and of low sp. gr., it has little mass 
resistance to the soakage and penetration of liquor. Bamboo is a hard 
and heavy material but is strongly resistant to mechanical force in the 
transverse direction only. To a splitting or crushing force acting 
longitudinally, it has scarcely any resistance whatever and it is possible 
by careful dissection to isolate individual filaments or fibre bundles, and 
to follow them up along the nodes and through the internodes for the 
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