27o MODERN PAPER-MAKING

at keeping the stock as uniformly dispersed as possible; secondly, in preventing,
as far as possible, eddy or other local disturbances from arising, and lastly,
the stock must be projected on to the wire at a speed which gives the most
desirable sheet formation and sheet properties generally. The optimum speed
of projection is of course intimately bound up with the wire speed. Normally
it is found that the best practice is for the stock to be projected at a rate which
is 5 to 10 per cent slower than the speed of the wire. Flow boxes must, of

FIG. 116.—SECTION THROUGH A TYPICAL FLOW Box AND SLICE FOR A HIGH-SPEED NEWS MACHINE
course, have no dead spots where slime and dirt can accumulate; a clean design,
in this respect, is consistent with the need for producing a uniform rate of
stock-flow to the slice.
The so-called projection slices (see Fig. 115) are used almost without exception
in high-speed news machines, although there are one or two other kinds of
slice working on different principles, and these may one day modify newsprint
slice technique. There is, for instance, the Millspaugh arrangement, in which
the stock contacts directly with a suction-operated forming cylinder. This
arrangement, incidentally, has the advantage of dispensing with the conventional
wire part of a paper machine* Another interesting development is the pressure
slice in use in one or two mills in the ILS.A. In this arrangement the wire
itself forms the base of a kind of swan-necked breast box. The stock impinges
on the wire and is to some extent forced down against it, giving an immediate
initial mat of fibres on the wire. The quantity of stock available for build-