CXVI. A, B, PORTUS. 
provements in the Von Schmidt type of dredging plant. (Plate 8 
and photograph of “Groper.”) 
The hull, built at the Fitzroy Dock, is of Oregon pine, and is 
115’ long, 50’ beam, and 9’ deep. One end is square, the ee 
semicircular ; the sides are 12” thick, the ends 16”. Two long}- 
tudinal bulkheads, as thick as the sides, extend from bow to 
stern, and these as well as the skin of the vessel are formed by 
fitting long 12” square beams on top of each other until a depth 
of 9’ is obtained, the whole being tied together with 17° drift 
bolts. The engines, fixed on strong hardwood framing, are com — 
pound surface condensing, with cylinders 20” and 38}” and 2 
stroke. Steam of 100 ibs. pressure is supplied by two return 
tube boilers, 10’ 4” long and 9’ internal diameter, with one cor- 
rugated furnace in each 4’ internal diameter, a smaller auxiliary 
boiler, 6’ 7” diameter and 9’ 1” long, is provided for use when 
silt has to be delivered more than half a mile from the dredge. 
The pump, with a shrouded cast iron spinner 7’ 6” diameter, has 
a wrought iron casing, and is driven at specds varying from an 
to 130 revolutions per minute, according to the distance the 
material has to be driven. 
The machinery for cutting the clay or other deposits is carried 
on a strong platform, which traverses on rollers from side to side 
of the dredge at the semicircular end. At the centre of the 
semicircle the suction pipe of the pump ascends, and by the 
intervention of a stuffing box and gland, the outer end of the 
pipe is enabled to move round horizontally with the travelling 
platform, beyond which the suction becomes vertical, and ter- 
minates in a system of telescopic pipes arranged to deal with the 
varying depths at which dredging has to be performed. A long 
vertical shaft is fitted outside of and in line with the telescope 
pipes and, while the latter telescope, the shaft is accommodated 
to different depths by passing through the centre of 4 driving : 
crown wheel, which is operated by a horizontal shaft leading toa 
special pair of engines working at the centre of the platform: 
On the lower end of the vertical shaft a horizontal cutter 8 pel : 
