FIG. 28.
Various modifications of the foregoing process have from time to time been proposed; among others, that of softening the wood by previous soaking in water, or steaming, seems to be valuable, as by so doing, it is highly probable that a longer fibre could be obtained, the soft wood being more readily torn away by the stones. Some inventors have proposed to replace the sandstone by an artificial stone containing a large quantity of emery.
An improved method of preparing mechanical wood pulp, lately patented by Mr. A. L. Thune, of Christiania, has been communicated to us by Mr. Carl Christensen.
| FIG. 29. | FIG. 30. |
The apparatus employed is shown in Figs. 28, 29, and 30. Fig. 28 illustrates an arrangement of grinding apparatus fixed direct on to a turbine. The stone is fastened on to the shaft S worked by the turbine T. The wood in the form of small blocks is kept in contact with the stone by a number of hydraulic presses P. {108}
A somewhat similar arrangement, but placed horizontally, is shown in front and side elevation in Figs. 29 and 30. The same letters correspond.
FIG. 31.