5 86 
Notes. 
bucket attached to the fibre. The attachment was effected by gluing 
the end of the fibre to a fine wire-handle on the bucket. 
To quote an example of one of these observations: the bucket 
suspended from a fibre, as described, was slowly filled with water. 
When the increasing weight parted the fibre, the bucket together with 
the water weighed 7-817 grs. Microscopic measurement showed that 
the greater diameter of the fibre was 0-0192 mm., and the lesser 
0-0078 mm. As the fibres are roughly rectangular in section, the 
area of cross-section equalled 0-00015 sq. mm. inclusive of the lumen 
of the cell, which, however, is very small. 
From this it follows that the breaking stress was not less than 
52,000 grs. per sq. mm. 
Another experiment gave the weight of bucket and water sufficient 
to break another fibre as 8-500 grs. But in this case the cross-section 
of the fibre was 0-0137 mm. x 0-0168 mm. It follows that the break- 
ing stress was greater than 37,000 grs. per sq. mm. 
It is evident from the nature of the method that these figures only 
fix a minor limit to the tenacity of cellulose. The breaking stress 
of cellulose must be as great or greater than 52,000 grs. per sq. mm. 
For it is impossible to determine the cross-section exactly at the point 
of fracture, and it has been my practice to estimate the section at the 
narrowest place above the fracture ; but of course this is not the 
smallest cross-section, supposing the fibre to be homogeneous. It 
seems indeed that the figures are much below the true breaking stress, 
and that fracture occurs at a point in the fibre weakened by some 
flaw. This may be demonstrated by taking one of the parts of 
a fibre, which originally parted under a stress, say, of 3 grs., and 
testing it in the same manner as before. It will then be found to 
support a greater weight: probably of 10 grs. or even 12 grs. One 
fibre, -017 x -018 mm., broke on the first trial at 8-500 grs., second at 
12-552, third at 16-267, and fourth at 18-200 grs. The final result 
gives a tenacity of 60,000 grs. per sq. mm. 
Hence we may safely assume that the tenacity of cellulose is greater 
than 50,000 grs. per sq. mm., which is about equivalent to thirty tons 
per square inch, and also about the same as the tenacity of Aluminium 
bronze \ 
The tenacity given for Red Pine 2 is 9,100 grs. per sq. mm.; but 
1 Numerical Tables and Constants, S. Lnpton. Macmillan, 1896, p. 17. 
2 Loc. cit. 
