MANUFACTUEES, ETC. 233 



The conifers yield mbre cellulose or pulp than 

 other wood and their fibres are larger than are 

 those of deciduous trees. 



Wood pulp may be either mechanical or 

 chemical. Mechanical wood pulp, as its name 

 implies, is manufactured by mechanical means 

 alone, no chemicals taking part in the proce'ss. 

 It is used for making the cheaper grades of 

 paper only, and although the idea of making 

 paper by mechanical means alone is an old one, 

 it is only by the aid of modern machinery that 

 the idea has been developed. From Messrs. 

 Cross and Bevan's excellent textbook of paper 

 making, which should be consulted by every- 

 one interested in this important manufacture, 

 we quote the following details of the process. 



" The wood is first cut up into blocks, the 

 size of which is determined by the width of the 

 stones used for grinding ; any knots present 

 are cut out with an axe. The stones are made of 

 sandstone, and are covered over three quadrants 

 with an iron casing, the remaining quadrant 

 being exposed. The surfaces of the stones are 

 made rough by the pressure of a steel roll 

 studded with points which is pressed against 

 the stone while revolving. In addition to this, 

 channels about J inch deep are cut into the stone 

 at distances of 2 to 3 inches. They are made 

 in two sets, crossing each other in the centre 



