404 JOURNAL OF THE PLYMOUTH INSTITUTION. 
Total matter in suspension per 100,000 parts. 
Cattewater (half-flow) . . . 9*802 
(half-ebb). . . . 9-815 
Thames (low-water) . . • 50*000 
„ (high- water) . . . 20*000 
Mississippi . . . 80*000 
The Ganges varies from 20 to 200 parts per 100,000. It 
is stated that the suspended matter discharged annually into 
the sea by this river is equal to forty thousand million cubic feet 
of clay. 
The Cattewater appears to have within it two elements of 
danger — one is the sewer outfall in Deadman's Bay, and the other 
is the reported increase in the deposit in the Laira. If this goes 
on unchecked, the channel will be narrowed, and, with a swifter 
current running on the ebb, the deposit will be carried lower 
down, to the prejudice of the harbour. 
The Cattewater Commissioners should at once have cross 
sections of the harbour taken at certain fixed points, and sound 
them periodically. They would then know exactly what is taking 
place in the bottom of the harbour, and would possess a record of 
the utmost value for reference. 
What certainly appeared to me to be most singular was, up to a 
certain point, the non-discovery in the dredged material of any 
curiosities in the shape of relics of the past. The only objects 
detected up to the point where the mooring-chain crosses the 
harbour were two tobacco-pipes of eighteenth-century shape, and 
a pewter spoon, bearing the effigy of Queen Anne. 
On dredging westward of this, and after removing some of the 
surface -silt, a serious obstruction Avas encountered, necessitating 
the utmost care in the manipulation of the dredger. 
It was discovered, after removal of some of the surface, 
that pieces of timber were sticking up through the silt ; and 
what was at first considered to be the remnants of perhaps 
some foundered barge soon developed into the remains of a large 
ship. 
The position of the wreckage was twenty feet west of the 
Cattewater mooring-chain, and twenty feet south of the line of the 
Cattedown wharves, with the stem pointing towards Cattedowm 
