ores through the main hatch without trimming, and small coasting craft of all ages, and of various classes, have gone wonderfully safe, but long vessels should either load partly through the fore and after hatches, or trim the ore fore and aft, to equalize the strain. For want of this precaution, some new vessels fall in the waist several inches, when afloat. A proportion of light cargo underneath ore may be found advantageous. The specific gravity of yellow ore is 4160; of red, 5.8 to 6.000; Derbyshire lead ore, 6.565 to 7.786; Coalbrook Dale iron ore, 3.527. 820. At Swansea, ships of 600 tons register, intended for Valparaiso, are prepared with two bilge keelsons each side the main keelson, on which a trunk is fitted for the reception of the ore; the platform is blocked off, say two feet from the ceiling; it runs fore and aft from bulkhead to bulkhead; the sides fall in, say three to four feet in all, when they reach the deck. A ship will not conveniently carry more of this ore than will fill one-third of the cubical contents of her hold. A Swansea firm adds-all vessels regularly engaged in the foreign copper ore trade, have the main keelson raised to the height of about four feet above the skin, on which is laid the platform, which should run as far as possible fore and aft, as many cases have occurred of vessels straining in consequence of the shortness of the platform, and the weight falling too much on one part. The trunk prevents the cargo from pressing against the sides, and generally slopes inwards about three feet. At the top it may be about onethird the breadth of the vessel. Some very narrow vessels dispense altogether with the trunk, and use a platform only; in which case the bilge keelsons are raised considerably higher than the main keelson, so that both sides slope down towards the centre. [In the drawing, the struts at the sides represent the shores against the bulkheads or trunk, which runs in a continuous line fore and aft with longitudinal cleats on the uprights to receive the shores.] 821. An experienced master says he loaded a ship with 500 tons of copper ore at Valparaiso; the ore was first laid level with the keelson, then a number of strong puncheons, 300 to 400 gallons each, purchased from a condemned whaler, were placed on their sides across the same; the ore was filled in upon them, and allowed to fall between. By this mode he avoided the necessity of constructing wings, which, in heavy weather, or in going a long time on one tack, are likely to be broken through. One of the barrels was full of flour, and so evenly was the pressure borne, that after discharging, the barrel was found uninjured. It cannot, however, be concealed that this master incurred some risk, which would have been greatly increased had any of the casks bursted, when the cargo must have run to the wings, and put the ship out of trim. It constantly happens that ships not fitted with platforms or trunks, are compelled to put into intermediate ports leaky. 822. Copper ores from Chili, which exports largely, and from Bolivian ports are always shipped in bulk. Shipments are made all the year round. When loading Peruvian or Bolivian copper ore in trunks, an experienced master recommends that it should be run up in three pyramids towards the fore, main, and after hatchways, keeping (of course) the greatest weight in the centre of the ship. Silver ore hence is packed in canvas bags containing about 50 lbs. each. The barque Cubana, 492 tons register, Capt. ANDREW PEARE, left Caldera, 27th May, 1862, and on the 20th June the mate came out of the cabin and the carpenter from the half-deck, and said the ship was on fire. She had a cargo of copper ore for Swansea, and was entirely consumed. After great privations the crew reached Falkland, where the second mate and one seaman died through cold and exhaustion. Bar copper is sometimes shipped at Coquimbo, and silver ore at Caldera de Copapo. 823. Copper ores from Sydney are generally in bags, which must be kept dry and not placed near the iron hoops of casks of oil or tallow; see the article magnetism. New Zealand ore, which is a combination of sulphurates of iron and copper, is subject to spontaneous combustion, and several serious accidents have thereby occurred. South Australian ore being carbonate and oxide of copper, has not that dangerous property. It is stated that when sulphur is mixed with ore and it becomes wet and heated, contact with light wood or other easily ignitable substances, will produce combustion. At Adelaide, copper ore is shipped in bulk as well as in bags, at a low freight for ballast, to receive wool. Copper ore at the Moonta Mine, Adelaide, is estimated at 21 cwt. to the ton. Adelaide copper ore contains about 25 P cent. of pure copper, and is shipped all the year round it is made up in bags of various quantities, from 1 to 8 cwt.; the bags containing 1 cwt. weigh 1 lbs. Each ton of Adelaide silver-lead ore contains from 50 to 60 cent. of lead and 30 to 50 oz. of silver. It is shipped all the year round, is packed in bags containing each 1 cwt., the bags weighing 14 lbs. to 2 lbs. each. It is also packed in sample boxes 18 inches long, 10 broad, and 10 deep. 824. Pomeran. The brig Mary Elizabeth, Capt. JONES, which belongs to Mr. N. HEWERTSON, Newport, is fitted with a moveable trunk for use when carrying ores. She registers 187 tons, is 101.8 |