XLII. H. D. WALSH. 
anchorages under ground. A certain measure of success 
attended this plan, but it had some serious defects: Round 
piles vary so much in diameter and straightness that they 
cannot be driven so close as to preserve contact throughout. 
Better results could certainly have been secured by siding 
the piles before driving, but this would have added con- 
siderably to the cost, and the removal of the bark anda 
part of the sap-wood would render the timber much more 
open to attack by marine borers than when driven intact 
with the bark on. 
A wall of sheet piling formed of round logs standing ver- 
tically, though very cheap in construction, cheaper perhaps 
than any other that has ever been devised, has the fatal 
defect of being insanitary and affording a harbour for ver- 
min. It presents a rough appearance, which perhaps would 
not matter so much, but in addition it furnishes an 
impregnable harbour for rats. As rats belong to the class 
of natural scavengers, and evidently consume a great deal 
of refuse that finds its way into every sea-port in spite of 
the vigilance of the authorities, there was not much 
objection to them until the plague broke out, and the 
source of infection was traced to the rats. 
As a good deal of close sheet piling had been done along 
the shores of Darling Harbour, the question arose as to 
how the objection on the score of rat-harbourage could be 
got over. It occurred to me that if the sheet piling could 
be covered with anything that would present a straight 
clean front from the wharf level to low water mark, the 
difficulty would be surmounted. The solution was found 
in the use of ‘‘ Monier Plates’’ hung in close contact all 
along the face of the sheet piling. The experiment was 
tried and found to be thoroughly successful. Up to the 
present time nearly 3,000 lineal feet of sea-walling has 
been treated in this way. The cost of a sea-wall so built 
