THE PANAMA CANAL.

New Zealand Herald, Volume LII, Issue 15931, 31 May 1915, Page 4

THE PANAMA CANAL.

*», OVERCOMING SLIDES. DIFFICULTIES OF ENGINEERS. Thk Panama Canal is open "for the passage of ships not drawing more than 24ft of water for only three or four hours every afternoon, says an American paper. For vessels' drawing 26ft, 27ft, and 30ft it I is open about one afternoon a week for j three or four hours. , That the canal is not completely closed, 1 making the Exposition at San Francisco in celebration of it a grim joke, is due *o the fact that the dredging division in the Culebra Cut works 24 hours a day, Sundays included. | When General Goethals expects to have the canal channel, so cleared within the next ten days that it will be open for ships drawing not more than 27ft of water at least five hours a, day, it is equally truo that the slides would completely close the canal within two or three days if the dredging division stopped work for two days in succession.

Unsatisfactory as these conditions are j there is reason to hope that by the time I the . great fair . closes the canal will be really an unobstructed open waterway. The dredging ileet, which conquered the Cueuracha slide nearly a year • ago, and which lias been holding back, tho present and larger slide, will soon be reinforced by another dredger as powerful as each of the two most powerful tnat have kept the canal open. It wih require about tho entire remainder of the exposition's lifetime for the entire dredging fleet with its expected reinforcement to take out all the earth and rock that' will inevitably either precipitately tumble down , the , sides of the' banks in the section of 1 the Culebra Cut that is causing the trouble, or more slowly but just as iuevitably push into the wafer channel. At present the dredging division is digging this earth and rock out at' the'. fate of 70,000 tons every twenty-four hours. ' The new dredge will ; dig out another 20,000 ''tons every day.

The banks of the Culebra Cut from I which all this material ' has been sliding, instead of being steep,. will be so sloping that ■if any moro material comes down it will move so slowly as not to caiiao any possible danger to* the canal channel. All Trouble in Short Section. Annoying as,have been the slides that have so far kept the canal from being a completed waterway they liavo all occurred within a section' of the canal, less than one mile long. The canal is" forty-seven miles long, and these slides ■ never would have occurred if the banks of the canal in this short section could have been made less steep before the date for the opening. The Cucuracha slide, which came down a bank far steeper than the slide that is now causing tho trouble, was conquered nearly a year ago. When entirely clear tho canal all through the nine miles of the narrow part called the Culebra Cut is 45ft deep and at the bottom 300 ft wide. At any place in the cut where a section of the bank comes into the canal and reduces either this depth or this width dredges are at once put to work. To make sure that they have not left some ridge of rock or hard dirt to endanger a passing ship, General Goethals uses two, four or six little rowboats. ,

A Simple Test. As soon as it is believed the big dredges have cleared the channel at any point where there has been a slide they are moved away and these little rowboats appear. In each there are two or three West Indian labourers at the oars. In one boat of each group there is 011 American , expert, who watches intently the surface of tho water. The negro in the stern sits on ,a board six or eight inches wide and two or three feet longer than the width of the boat. Under the boat, hanging by wires attached to the end of this board, is a piece of galvanised iron pipe, six or eight feet long and an inch or two in diameter. Tile weight of this pipe makes it hang directly under tho boat and the wires holding it are carefully adjusted to keep it, six or eight inches above "what the dredge men believe is the bottom of the canal where they | have been digging. Automatic Tell-tale. If the dredges have left a ridge of dirt or rock one of these' pipes (or sweeps" as they are called) will strike and stop the boat. The expert knows within a miiiuto just about the nature, dimensions, and position of the obstruction. He signals to his otlier boats that his boat is going to the bank and that they .are to continue and work until further orders. With a field telephone he telephones his facts to W. G. Comber, the division engineer in charge of fill dredging operations, and he decides whether it is necessary for a dredge to go out and remove it. If a dredge is sent the "sweepers" go over the spot again after it leaves. When it appears the young engineers who have charge of this "sweeping" work, in addition to many other duties, are able to be sure their little rowboats move over and therefore test every square foot of the place in the canal where thero might be any chance of a rock on the bottom. As soon as the'engineers in charge 'of this work report that all is clear, Mr. Comber notifies Captain Rodman, of the navy, superintendent of canal transportation, who gives the necessary orders, and ships start to pass. When Mr. Comber thinks it time to sweep the channel once more for suspected upheavals from the bottom, lie so informs Captain Rodman, who suspends ship transit again.

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