Correspondence on Recent Progress in Dredging Machinery.

Abstract

observed that the Paper formed a useful extension of a prcvious Paper 1 by the Author. The types denlt with only included the ladder dredger, suction dredger, and dipper dredger; the grab dredger was not alluded to, though it had been extensively adopted for its special purpose in the Mersey and elsewhere. The vessels described were those built by the Author's firm, except the dippers, and the only variations from 1901 were as to growth in dimensions and capacity, which, although considerable, seemed to Mr. Berridge less than might be expected. The suction dredger had had its sphere of action enormously increased by the addition of the cutter head, and this was the principal point of interest in the Paper. With regard to all these vessels, the terms in which they were described in the Paper were too vague to be of much assistance, and possibly it was expecting too much to hope for more detail. " Engines sufKcient to propel at a speed of about 7 knots" and such generalities did not contribute much more t o the knowledge of the subject by the profession. A single set of observations on the indicated horsepower , velocity, loss of head, quantity delivered and similar data from the " Jinga," " Kalu " or "Pelican" would be of far more service than Tables such as IV and V. With regard to all such craft it was idle to ignore the great progress made by Continental builders in constructing light and yet efficient and powerful craft. British builders seemed to have settled down to a fixed type of solid construction, which was, however, extremely difficult to repair if anything went wrong in out-of-the-way spots such as dredgers often had to go to. Mr. Berridge's experience of these craft was that builders did not pay sufficient attention to the question of facility of replacement and repair. The work performed demanded that such renewals must be frequent to keep the machines working efficiently or even without danger. Changing buckets, links, and pins, W:LS a daily-even (on some classes of work) a n hourly-operation ; yet the main engine was still the only apparatus for backing down the chain, with accompanying risk and lack of control. Caps of bearings and connecting-rods were still to be found, of malleable "Dredging and Modern Dredge Plant." Thus. Inst. of Engineers a n d Shipbuilders ill Scotland, vol. slv, p.