he dredged material is discharged into the Scheldt, a
quantity of 5886 cub. yds. has been raised and deposited in a day, the
mean quantity being 4700 cub. yds. When the distance of transportation
is increased to 2-1/2 m., six voyages were made in a day, and the day's
work amounted to 3530 cub. yds.

_Gold Dredgers._--Dredgers for excavating from river beds soil
containing gold are generally fitted with a screen and elevator.

[Illustration: FIG. 2.--Diagram showing Action of Lobnitz Gold Dredger.]

They have been extensively designed and built by Messrs Lobnitz & Co.
(fig. 2) and also by Messrs Hunter & English.

The writer is indebted to the _Proceedings_ of the Institution of
Civil Engineers, and especially to the paper of Mr J. J. Webster
(_Proc. Inst. C.E._ vol. 89), for much valuable information upon the
subject treated. He is also indebted to many manufacturers who have
furnished him with particulars and photographs of dredging plant.
(W. H.*)

Plate I.

[Illustration: FIG. 3.--Barge-loading dredger, "St Austell," constructed
for the British Government by Wm. Simons & Co.]

[Illustration: FIG. 4.--Stern-well hopper-dredger "La Puissante," by Wm.
Simons & Co. Length 275 ft., breadth 47 ft., depth 19 ft.]

[Illustration: FIG. 5.--Dredger constructed for the Lake Copais Co. by
Hunter & English.]

[Illustration: FIG. 6.--Light-draught dredger, with delivery apparatus
working round an arc of 210 deg., by Hunter & English.]

[Illustration: FIG. 7.--Twin-screw sand-pump dredger, "Kate," built for
the East London Harbour Board by Wm. Simons & Co.]

[Illustration: FIG. 8.--Twin-screw hopper-dredger, "Percy Sanderson,"
built for the European Danube Commission by Wm. Simons & Co.]

[Illustration: FIG. 9.--Twin-screw grab-dredger, "Miles K. Burton,"
built for the Mersey Docks and Harbour Board by Wm. Simons & Co.]

[Illustration: FIG. 10.--Hopper-dredger, "David Dale," with buckets of
54 cub. ft. capacity (see fig. 11) built for the North Eastern Railway
Company by Lobnitz & Co.]

Plate II.

[Illustration: FIG. 11.--BUCKETS OF 5 AND 54 CUBIC FEET CAPACITY
COMPARED.

The latter, the largest ever made, were for the hopper-dredger "David
Dale" (Plate I. fig. 10), built by Lobnitz & Co.]

[Illustration: FIG. 12.--MODEL OF ROCK-CUTTING DREDGER, "DEROCHEUSE."

Built for special work on the Suez Canal by Lobnitz & Co. Length 180
ft., breadth 40 ft., depth 12 ft.]

2. MARINE BIOL