The first steam dredge of the bucket type was launched on the Clutha in 1881. Such dredges differ from current-wheelers only in being provided with engine and boiler in place of the undershot wheel. The use of steam machinery, of course, increases the initial cost, adds to the working and maintenance expenses, and necessitates the employment of skilled mechanics. But these disadvantages are, in most cases, largely outweighed by the greater output and the wider utility of such dredges. They can be used in places where there is insufficient current for a wheel dredge; and they are able, when the river is too high for midstream operations, to work along the banks, or run up into the eddies and backwaters, where a minimum amount of silt is being deposited. Hence with the introduction of steam, stoppages have been of shorter duration, and work has proceeded more regularly.