CENTRIFUGAL PUMP DREDGING IN N.S.W. CXVII. 
diameter is keyed, with steel knives at its circumference looking 
both up and down. The bottom of the suction pipe is hooded, 
extending over the cutter. When the machinery is put in 
motion, the material broken up by the knives is swept up by the 
action of the pump through the suction pipe and forced shoreward 
in the discharge pipes, which are fitted with ball and socket joints 
and carried on pontoons. On shore the discharge pipe is fitted 
with a breeches piece and valves, and two pipe lines are after- 
wards used so that one may be pumped through while pipes are 
added to the other. The shore pipes are telescope ended, and 
can be quickly placed to ensure a level reclamation. The over- 
flow water, after passing over an extended settling area, returns 
to the harbour. Much ingenuity has been displayed by the 
patentee in arranging by belts, gear, shafting and clutches, the 
various appliances for lifting and lowering the suction pipe and 
cutter, and for giving reciprocating movement to the platform. 
So effective is the cutting mechanism, that a Von Schmidt dredge 
can cut its way into a bank 3’ above high water just as readily 
as it can deal with stiff clay or even soft rock at a depth of from 
12 to 20’, 
_The system of mooring the “ Groper” for work is that gener- 
ally adopted in America, viz.: by two long spuds passing through 
wells and lifted and lowered by steam power from masts placed 
alongside. I have already referred to the difficulty in carrying 
Out in the past in Sydney Harbour a comprehensive scheme of 
reclamation at a reasonable cost, owing to the areas suitable for 
reclaiming being too far distant from the channels to be deepened, 
and schemes were thought of for pumping the silt out of the 
punt hoppers ; but the difficulty was overcome by dumping the 
dredgings, in the punts filled by the ladder dredges, alongside a 
suction dredge, and thus performing the work of deepening at 
One part of the harbour and reclaiming at another by two 
machines instead of one. The Dutch type of pump being un- 
Suited for pumping on shore the Sydney Harbour clay, thus 
dumped, the “Groper” was built at a cost of over £20,000, 
