QUEKETT MICROSCOPICAL CLUB. 205 



absorbent papers the pulp is now run on to the paper-making 

 machine, but in the case of writing papers sizing is necessary. 

 This may be done by adding resin and alum to the pulp in the 

 beaters, giving engine-sized paper, or the paper when made may 

 be passed through a vat of size. After leaving the beaters the 

 pulp is strained, and then passed into the paper-making machine, 

 which consists of a travelling wire web that oscillates horizontally, 

 so shaking the fibres in two directions. During this process some 

 of the water is removed by suction, and the paper is dried by being 

 passed over the couch rollers, and finally over the drying cylinders 

 with the dry felts. Whatever material is used in making paper 

 the principle is the same. 



When a microscopical examination is to be made of a sample of 

 paper it is disintegrated by boiling in weak caustic potash solution, 

 washed and teased out with needles in a watchglass of water. A 

 small quantity of this fibrous matter is put on a slip in a drop of 

 water and covered with a cover-glass ; it is then examined to 

 identify the fibres and roughly to estimate their percentage. The 

 fibres present in paper are : Linen and cotton in high-class papers, 

 wood fibres from wood pulp, either mechanical or chemical, 

 esparto grass, straw, jute, hemp, wool, and, in papers made in the 

 East, bamboo, silk and many other materials. Mr. Wycherley 

 then described the appearance under the microscope of the 

 various fibres. 



Linen. — Long, rounded, or irregularly hexagonal fibres. Natural 

 ends pointed, but probably frayed during treatment. This is 

 known as lamination, and if excessive indicates undue breaking 

 of the fibres, probably in the beaters, leading to weakness 

 of the paper, although the material may be of the best quality. 

 A canal runs regularly from end to end. The bending of the 

 fibres during manufacture causes creasing. The nodes, which 

 are like bamboo nodes, are usually burst, forming slight hooks, 

 which bind the fibres together and strengthen the paper. 



Cotton. — Distinguished from similar fibres in wood pulp by 

 the use of the polariscope, when the bordered pits of the latter 

 are clearly shown up. Fresh fibres are round, but they become 

 flattened and invariably twisted. A canal and longitudinal 

 striation can be traced. Nodes such as are present in linen 

 fibres are absent. 



Wood Fibres result from mechanical or chemical wood pulp. 



