502 AUXILIARY FOREST INDUSTRIES. 



done usually by manual labour. In the other kind of 

 machine the wood is cut up into wood-pulp for paper manu- 

 facture. By the former method the wood in cylinders 10 to 25 

 cm. in diameter and varying in length, of aspen, lime or 

 spruce, is barked and cut into pieces about a foot long ; it is 

 then split and all knots bored out of it. Then the pieces are 

 pressed against a rotating stone under a steady flow of water, 

 the coarser fragments are sifted off and separately reduced to 

 pulp, and the fine pulp freed from superfluous water and 

 pressed into its marketable shape. This is white pulp of the 

 same colour as the wood. 



If, before grinding, the wood is steamed at a pressure of 

 2 to 6 atmospheres or boiled, brown pulp is produced, which 

 has longer fibres than white pulp ; after adding glue, clay, 

 etc., it is used for brown paper for packing purposes. The 

 first wood-pulping machines were constructed in Heidenheim 

 by Volter ; they require a considerable flow of water, both 

 for power and for the purposes of manufacture. There are 

 now 700 pulp-factories in Germany, which use annually one 

 million solid cubic meters of word (35,000,000 cubic feet). 



Besides the more important wood-working machines there 

 are a number of others used for special purposes, such as 

 mortising and turning machines, and oscillating augers for 

 boring holes of various dimensions. Among the splitting 

 machines those for reducing the size of firewood billets are 

 employed extensively in large towns. 



B. TREATMENT FOR THE IMPROVEMENT OF 

 WOOD.* 



SECTION I. IMPROVEMENT IN APPEARANCE AND QUALITY. 

 1. Improvement in Tc.Hure. 



The woods of many species, e.g., lime, birch, alder and 

 conifers, are not ornamental, but the method described on 

 p. 501 can be adopted to render them so. 



* II. StiibliMjj. Tcrlmisrlirr l!utp>l>ci' ;iut' dcin (u'lnrtc <lrr I lol/.in.lust rir." 

 Ldp/ig, 11)01. 



