gS ELEMENTS OF yIPPLlED MICROSCOPY. 



1 7 19, who derived his idea from a study of the way in 

 which wasps construct their nests from this material. 



The first step in paper-making is the treatment of the 

 raw stock with some chemical in order to break it up, to 

 dissolve the cementing gums, and to separate the cellulose, 

 which is always the principal constituent of paper, in as 

 pure a form as possible. The crude material is generally 

 boiled with strong alkali under pressure, and then washed 

 in a- tank from which the waste water is removed by a 

 revolving drum. Wood paper is also made by an acid 

 process, the stock being treated with the bisulphites of 

 lime and magnesia; and mechanical wood-pulp for a 

 low grade of paper is prepared by simple attrition against 

 stone surfaces without chemical action. 



After treatment in the boilers and washers, the paper- 

 stock is bleached, and at this stage is known as "half- 

 stuff." It is next passed through the beaters, in which a 

 wheel bearing knives breaks it up into a fine fibrous 

 condition. Sizing, loading, coloring, and other auxiliary 

 processes are accomplished in the beaters. Finally, the 

 fully prepared pulp passes to the paper-machines, where 

 it is spread in a thin sheet of running water over a 

 moving endless belt of wire cloth. The fibrous material 

 deposited in a fine and even layer passes on through 

 felted rollers, which press out the last of the water and 

 compact its texture. 



2. The Raw Materials of Paper. — Obviously paper 

 might be made from any material which can be ground 

 up to a fine fibrous pulp; and such bizarre substances 

 as seaweeds, shavings, sawdust, com-husks, cabbage- 



