Scientific American Supplement, No. 799, April 25, 1891 eBook

This eBook from the Gutenberg Project consists of approximately 110 pages of information about Scientific American Supplement, No. 799, April 25, 1891.

Scientific American Supplement, No. 799, April 25, 1891 eBook

This eBook from the Gutenberg Project consists of approximately 110 pages of information about Scientific American Supplement, No. 799, April 25, 1891.

She was raised off the rocks by the water rising and compressing the air in the two foremost holds, assisted by the buoyancy of the engine room and No. 3 compartments.  At high water the bow was afloat, but she was aground by the stern.  When, however, she was taken in tow by three tugs, she slowly slid down the reef and floated into deep water.  One tug was placed on each bow, and the third was ahead.  In this state she was towed into West Port, a distance of four miles, and there beached on a sheltered stretch of sand.

The casks performed no part in floating the ship off, but were only there in case the great pressure of air should cause the escape of some of it, in which event all the space underneath the lower deck would soon have been occupied with water instead of air.  These casks would then, of course, have served to displace a large amount of this water, and so keep her afloat.  Luckily the deck did not leak, and the barrels were thus not instrumental in the raising.

When beached the hatches were taken off, the casks removed, and a false deck was built about 7 ft. below the lower deck, and about 10 ft. above the keel.  This was used as the bottom of the ship to take her round to Halifax, and was built in the following manner:  A kind of iron platform, about 2 ft. wide, runs along the sides of the holds in the Ulunda for strengthening purposes, braced at intervals of 15 ft. by iron beams across the ship.

On this was built the wooden deck.  Beams for this deck were constructed of three 3 in. planks, and were laid down on the iron platform about 31/2 ft. apart, and firmly wedged into the ship’s side.  On these beams a layer of 3 in. planks was placed in a fore-and-aft direction and nailed down; on this were three layers of felt, and on this again more planks were laid down in the same direction as before.

The whole deck was then carefully calked and the sides made watertight with Portland cement.  This deck only extended to the engine room bulkhead through the two foremost holds.  It was prevented from bursting up by the pressure on the bottom of it, by means of shores, in the same manner as the iron deck had been served before.  Shores were, therefore, connecting the three decks—­the upper deck, lower deck, and wooden deck—­this being done to equalize the pressure on the extempore deck and the two permanent decks, and thus gain additional strength.

No deck was built in either of the after compartments, inasmuch as No. 3 hold was kept clear of water as before by its pump, and in No. 4 the deck was not necessary.  To have built one there, as in the two foremost ones, although it would have given a little more reserve of buoyancy to the ship, would have raised the stern higher than the bows, and so would have increased the upward pressure on the wooden deck, and thus have increased the liability to burst up.  For the same reason, when raising the ship off the rocks, no compressed air was used in the after

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Scientific American Supplement, No. 799, April 25, 1891 from Project Gutenberg. Public domain.