(2.) That in bucket dredges, the actual engine power is roughly seven times that theoretically sufficient to do the work. These results cannot be called conclusive, but they serve to show: (1.) That the frictional losses of power in gold-dredging are very great, probably 600 to 700 per cent, of the power theoretically sufficient to do the lifting work. The difference in the weight of the gravel lifted, while under the water level, has been disregarded and, in estimating the steam power in compound engines, it is assumed that the low-pressure develops the same power as the high-pressure cylinder. The calculations are made in theoretical horsepower, and for easy references are given in tabular form. In calculating the horse-power consumed by suction and by bucket dredges, figures have been taken from the various official reports on the mining industry in New Zealand, dates and pages in each instance being given.
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