206 Use of Wood in Paper-making. 



obliquely off by saws, and in both of these the wood is ground in a 

 mill before being used. 



824. By the chemical process, which is more recent and more 

 costly, but which produces a better result, the wood is first cut into 

 short chips by heavy revolving planes, and then macerated in large 

 and strong boilers, with caustic soda, and under a pressure of 10 or 12 

 atmospheres. By the "Sinclair Process" this is done in upright 

 boilers. By the " Lee Process " it is done in larger boilers, that are 

 horizontal. By the "Fry Process" water alone is used, under a 

 pressure of 5 or 6 atmospheres, and saw-dust is thus made avail- 

 able as a material. The product is a brown pulp, and used for wrap- 

 ping paper only. 



. 825. Wood-pulp is chiefly used for making wrapping and news- 

 paper, wall-papers, and the like. It is sometimes used for envelopes, 

 but as at present made it is scarcely proper for writing-paper, nor 

 for the grades required in finer book- work. But the consumption for 

 these is enormous, and constantly increasing, and these industries 

 are here noticed chiefly aa affording a profitable business in forest 

 culture. 



826. We have elsewhere (p. 90) noticed the strong tendency of 

 poplars to come up as second growth where pines have been cut 

 away, and where the soil has been injured by forest fires, so as to be 

 unprofitable for the cultivation of common field crops. When pro- 

 tected, such poplar groves properly thinned out grow rapidly, and 

 in from ten to fifteen years will be fit to cut for paper-pulp. They 

 will readily reproduce themselves from sprouts, and the cuttings 

 should be so arranged, if possible, that the trees be kept at the same 

 age, and be cut off down to the limit of smallest available size in 

 the same year. 



827. Saw-dust of red-cedar is used in the coarse thick paper 

 placed under carpets, upon the theory that it wiU prevent injuries 

 from moths. 



CHAPTER XXI. 



TANNING MATERIALS. 



828. Supplies of material for tanning leather are derived from 

 the forests, chiefly in the form of bark, or their extracts; but oc- 

 casionally other materials are used, such as valonia, or the acorn- 

 cups of an oak (Qitercus mgUops), growing in Greece and Asia-Minor, 



