322 THE UTILISATION OF WOODLAND PRODUCE. 



the cellulose vat is then washed out by running water through 

 it before men can go down to shovel out the pulp. The raw 

 cellulose is next placed in water-troughs slightly inclined and 

 kept constantly shaken slightly from side to side, then led off 

 with flowing water over a long succession of troughs to free the 

 pulp from impurities ; but before being thus strained it is, 

 whenever necessary, bleached with chlorine to the extent 

 required, any unnecessary bleaching being avoided, as it lessens 

 the strength and elasticity of the felty fibre. In its passage 

 down the water-troughs, the fibres become finer and more 

 equally distributed in the water, until at last they are fairly equally 

 deposited in one broad sheet upon a roller of felt which leads 

 them off to revolving drums, where they are pressed to free 

 them from water, then carried between heated rollers which 

 further dry and compress the pulp now formed into paper, and 

 wind it into rolls. There is but little loss in weight by this 

 process ; but softwoods like Willow and Poplar and Conifers 

 like Spruce and Silver Fir are easiest and cheapest to treat, and 

 are therefore preferred. One ton of dry wood gives about 6 

 cwt. of cellulose (30 per cent) by the alkali process, and 10 cwt. 

 (50 per cent) by the acid process, and the value of the cellulose 

 is about 7, 10s. per ton. 



To enable a small cellulose-mill to be worked profitably, at 

 least 80 cubic fathoms or about 12,000 cubic ft. of wood are 

 needed weekly, equal to 4000 fathoms or 600,000 cubic ft. per 

 annum. This equals the yield from about 120 to 150 acres of 

 40- to 50-year-old Spruce, yielding from 4000 to 5000 cubic ft. 

 per acre according to the quality of the soil and of the crop, so 

 that probably about 6000 acres of well-managed Spruce-woods 

 would be needed to supply even a small cellulose-factory. But 

 thinnings of 4 in. to 6 in. top diameter and 6 in. to 8 in. bottom 

 diameter are very suitable for pulping ; and wherever there are 

 very much larger woodlands, thinnings from them could well be 

 thus utilised. 



