250 
Transactions of the Society. 
developed in Germany by Herzberg (1888), Behrens (1896), and 
Hanausek (1901), and in Austria by v. Hohnel (1888). 
In this country much of the recent literature on the microscopy 
of paper-fibres has been borrowed from German text-books, but 
the scientific application of the microscope in practical laboratory 
work has been stimulated by a few well-known microscopists, 
among whom we may mention Christie (photo-micrographs) and 
Flatters (preparations), and by the work done in the laboratories 
of technical chemists connected with the paper-making industry ; 
among the latter we find Cross and Bevan, Evans and Wirtz, 
Gemmell, Beadle and Sindall, all of whom have done much for 
paper microscopy by research work, publications and translations, 
and personal tuition. 
2. Routine Work. 
The microscope is generally used in the paper-mill laboratory, 
in the first place, for the identification of various fibres in common 
use, such as linen, cotton, hemp, esparto grass, straw, manila, jute, 
wood, etc. The pulped fibre is mounted temporarily in one of the 
numerous iodine stains, prepared specially for the purpose, and 
examined under a medium power ; a good 16 mm. objective is the 
most useful lens for this work. The fibres are identified by their 
characteristic forms and markings, and the percentage composition 
of mixtures estimated to within 5 p.c. For accuracy in this work 
long experience and constant practice are necessary. It is a 
common experience to find random workers varying as much as 
10 or 15 p.c. in their estimates of percentage composition. The 
differentiation and identification of fibres is used — 
(a) In the analysis of samples sent to the mill, for match- 
ing with orders ; and 
(5) Controlling and checking the work of the practical 
paper-maker in his blending of various fibrous stocks. 
The routine work in the average paper-mill laboratory also 
generally includes — 
(c) The identification of starches (used in sizing) ; 
(ft) The examination of mineral powders (used as fillers), 
such as kaolin, gypsum, talc, etc. ; 
( e ) The identification of foreign matter, and tracing the 
origin of “ dirt ” particles in pulp and paper ; and 
(/) In some mills the beating process and the reduction of 
fibre-length is partly controlled by microscopical 
observation. In mechanical wood-pulp mills the 
grinding is largely controlled by microscopical 
observation or projection by some form of the 
lantern microscope. 
