236 BIOLOGICAL PROBLEMS 



pre-war days. More straw is being used, and with it 

 blemishes creep in. These a layman might not think 

 important, but the paper-maker does not share that 

 view. When settled conditions return he will produce 

 once more the old high qualities. As a craftsman he 

 could not do otherwise. 



Still, as elsewhere, adventurous spirits are not 

 lacking, and trials of a variety of fibres hitherto un- 

 tried by paper-makers are in progress. Such experi- 

 ments will serve to illustrate the fact that there is no 

 such thing as true substitution. When a raw material 

 is changed the finished product is changed; so too 

 must be the established method of manufacture at 

 nearly every stage. 



We may consider briefly the stages in the process 

 by means of which the web or felt of cellulose termed 

 paper is obtained. 



The raw material let us say a grass has to be 

 collected from its habitat, dried, baled, and trans- 

 ported to the mill. Here, after cleansing, it must be 

 boiled in soda or other suitable chemical agency to 

 remove the non-cellulose, and also to dissolve the 

 matrix which holds the fibres together what bo- 

 tanists call the "middle lamella". The product of 

 boiling has to be washed and bleached, and then 

 follows the elaborate technical process of beating, in 

 which the diluted pulp circulates in a trough between 

 revolving knives or plates, which can be adjusted to 

 effect a variety of ends, having the general object of 

 rendering the ultimate units of the pulp better fitted 

 to play their allotted part. By fraying out the ends 

 of the fibres they will felt the better; if the fibres are 

 too long, they can be cut into shorter segments; or, 

 by crushing, the fibres become more intimately 

 charged with water hydrated so as to give a homo- 

 geneous texture as they join together and dry. 



