CENTRIFUGAL PUMP DREDGING IN N.S.W. _ CXXV. 
Mr. ALLAN said that in this class of work, it was customary, 
he understood, with most authorities on dredging to give the rate 
per ton exclusive of interest and depreciation of machinery, an 
item which would of course make some slight difference in the 
results, therefore to enable a comparison of cost to be made with 
_ other works of a similar character, it is necessary to know the 
basis on which the author’s table was prepared. Another point 
of considerable importance and one upon which the author might 
give the results of his long experience, is the percentage of ‘‘solid 
stuff” passing through the pumps, with different lengths of shore 
Pipe lines, and the power required to lift same at different depths, 
whilst full particulars as to the method of measurement and as to 
the number of cubic feet to the ton taken by the author in com- 
piling the table accompanying the paper, would add to the useful- 
ness of a very valuable and interesting record of centrifugal pump 
dredging in this Colony. 
The Cuairman drew attention to the dredging at the entrance 
of the Mersey River, referred to in his annual address, in which 
the cost was given at only 0-89d. per ton, representing about $ 
cubic yards of solid material passing through the pump. 
Mr. Haycrorr said, that as regards the use of leather for 
flexible joints, in America 13” rubber is generally used for this 
purpose, and it was scarcely necessary to point out that this 
makes the best joint obtainable. With regard to the use of two 
Spuds, the Americans use one spud, and he thought that one spud 
with a fixed suction end would be preferable. These were the 
only two points in the paper in his opinion that called for discus- 
sion, 
Mr. Hoveuton said, that although the paper contained a vast 
amount of information, still there was an absence of any informa- 
tion as to the horse power required to do the work, comparing 
the very long delivery pipes on the hoppers of the dredges. He 
would like to know from Mr. Portus, the relative difference in 
the power required when dredging at different depths. It was 
Stated that the ““Neptune’s” indicated horse power was 300, and 
