206 PROCEEDINGS OF THE 



The former are the fibres of wood crushed and broken into ptdp. 

 It is used only for the commonest papers ; fibres are short, 

 broken and coarse, parts of the medullary rays are frequently 

 seen. Chemical wood pulp is made by boiling the wood under 

 pressure in caustic soda, calcium bisulphite, or sodium sulphate. 

 Strong brown papers are made by the last method in the Scandi- 

 navian mills, the length of the fibre being retained by slow cooking 

 and careful disintegration. The fibres are larger, cleaner and 

 less broken than in mechanical wood pulp. 



Esparto Grass. — Brittle and soft papers, known as grass 

 papers, are made from this. The fibres are short, smooth and 

 round, with a central canal and pointed ends. Cellular hairs 

 from the leaf surface are always present, as, although useless, 

 they cannot be filtered out ; they serve, however, the purpose 

 of diagnosing the presence of esparto. 



Straio Fibres, used only in coarse wrapping-papers, are shorter 

 and thicker than esparto and more brittle. They show bands and 

 creasing and characteristic cellular hairs. 



Jute Fibres have an irregular canal, nodes and parallel longi- 

 tudinal striae. 



Manilla Fibre, from hemp, is a long fibre, and one of the 

 strongest used in paper-making. The walls are thin and the 

 canal wide ; no nodes are observable. It is used for making 

 strong paper when a good colour is not essential. 



In addition to the above vegetable fibres, animal fibres are often 

 found. Silk fibre is long and smooth, and does not hold together 

 well. Wool fibres are often used in filter-papers and other similar 

 soft-sized paper. They are easily recognised by their markings. 

 Sketches of the various, fibres were made on the blackboard. In 

 examining fibres 1/4-in. or 1/5-in. objectives are used, and fre- 

 quently polarised light. For permanent mounts glycerine jelly is 

 suitable. The materials used in loading the paper may often be 

 recognised. China clay as small oval particles, calcium sulphate 

 as irregular crystals, mostly prisms and needles, barium sulphate 

 as diamond and wedge-shaped crystals, and starch granules may 

 be easily recognised. 



In answer to the many questions that were asked by the 

 members after the paper had been read, Mr. Wycherley said that 

 the refuse from sugar canes was used in Indian and Chinese paper 

 mills like bamboo. Thin, tough papers, such as India paper, 



