In working auriferous river-beds, dredges have been used with considerable success in certain parts of New Zealand and on the Pacific slope in America.
The dredges used in California are almost exclusively of the endless-chain bucket or steam-shovel pattern.
Some dredges have a capacity under favourable conditions of over 2000 cub.
In South Island the river-beds of Otago province have been successfully worked by means of dredges, and good returns secured.
Limestone is abundant, and the city has various manufactures, including lime, foundry and machine-shop products, agricultural implements, planing-mill products, engines, steam shovels, dredges, pianos and silks.