. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . able to strip up to a maximumdepth which does not exceed the thick-ness of the layer of ore uncovered. Figs. 232, 233, and 234 show theore docks and the type of vessels usedin transporting the ore. * Down tolate in the fifties the ore product ofLake Superior was handled over amule-tram road to Marquette, and aslate as 1870 a 700-ton ship was anenormous craft, the loading of which re-quired two days and the unloading be-ing seldom accomplished in that time. In 187
. Steel rails; their history, properties, strength and manufacture, with notes on the principles of rolling stock and track design . able to strip up to a maximumdepth which does not exceed the thick-ness of the layer of ore uncovered. Figs. 232, 233, and 234 show theore docks and the type of vessels usedin transporting the ore. * Down tolate in the fifties the ore product ofLake Superior was handled over amule-tram road to Marquette, and aslate as 1870 a 700-ton ship was anenormous craft, the loading of which re-quired two days and the unloading be-ing seldom accomplished in that time. In 1871 the largest ore bargecarried 1050 tons, now the cargoesreach 14,000 tons. 165,000 tons ofore has been loaded into sixteen steam-ships in one day at the docks of theDuluth, Missabe and Northern Rail-way. The loading of the steamer Corey of 10,000 tons capacity atthe Duluth and Iron Range SteelOre Dock, at Two Harbors, Minn.,was accomplished in 39 * The Development of Lake Superior Iron Ores. Bacon. Trans. American Institute of MiningEngineers, Vol. XXVII (1897), p. 341. f Scientific American, December 11, 352 STEEL RAILS The construction of a special type of ship of large tonnage for ore trade,coupled with the invention of unloading machinery of great capacity at the terminal ports, has brought thecost of transportation down toa very low figure. Thus, a tonof ore is now hauled one hun-dred miles by rail from themost distant mines in the LakeSuperior range to a Lake Su-perior port, is loaded into carsor into the stock pile at a LakeErie port at a cost of less than$ per ton. Fig. 235 presents an in-board profile and cross sectionof the Wolvin, a representa-tive of the type of present oresteamers. This vessel is 550feet in length, 56 feet beam and 32 feet deep. The largest single cargo of orecarried by the Wolvin was 11,536 tons, a feat which she performed in 1904.
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