The Microscope in the Paper-Mill. 
255 
6. Microscopical Research in the Paper-Mill. 
In an Appendix to this paper I have given an outline of the 
field in which the microscope may be used in paper-mill work, 
including some suggestions for research work, for it will be found 
that up to the present time only about 20 p.c. of the ground 
covered in this outline has been thoroughly dealt with by micro- 
scopists. 
There are several points, however, which require special notice. 
An important field for research lies in microscopical observa- 
tion of the effects produced by the beating process. The imparting 
of colloidal properties to cellulose pulp by mechanical treatment 
is accompanied by a structural disintegration of the fibre. The 
trend of modern technical opinion on the so-called “ hydration ” of 
cellulose is towards a chemical explanation, but from long-continued 
microscopical observations, with immersion dark-ground illumina- 
tions, combined with other experimental work, I am of the opinion 
that a purely physical explanation is sufficient, and that the minor 
chemical changes are incidental. 
Another field almost untouched is the systematic association 
of variety in fibre structure with the physical characteristics of 
paper made from particular fibres. 
Transparency and opacity to light, natural “ bulk ” and density, 
elasticity and brittleness, etc., etc., are properties associated in 
many cases with particular fibres, but the particular structures 
giving rise to such properties have not been fully and syste- 
matically investigated. 
In this connexion the use of the microtome and the polariscope 
have proved fruitful in my own experience. 
Paper- making technologists all the world over are, and have 
been for over a century, searching for new sources of raw fibrous 
materials. In this subject many more failures than successes 
have been recorded. Undue prominence has too frequently been 
given the “ yield ” of cellulose as determined by chemical means 
without careful description and valuation of the cellulose from 
microscopical examination. Any plant yielding more than 35 p.c. 
cellulose is regarded as promising, provided that questions of 
quantity, transport and treatment are commercially solvent. Three 
of the most promising new fibres which are being experimented 
with at the present day are cotton-hull fibre (unripe cotton), 
bamboo and papyrus. Cotton-hull stock is a most promising 
material, yielding with proper treatment a strong fibre of good 
permanent qualities. Very fine printing-papers have been made 
from both bamboo and papyrus, but both of the latter contain a 
much larger proportion of non-fibrous epidermal and parenchymous 
elements than any other material in common use. The laboratory 
