What is Long Ton?

Legal Definition
Long ton, also known as the imperial ton or displacement ton is the name for the unit called the "ton" in the avoirdupois or Imperial system of measurements standardised in the thirteenth century that is used in the United Kingdom and several other British Commonwealth of Nations countries alongside the mass-based metric ton invented in 1799.
-- Wikipedia
Legal Definition
A measure of weight equivalent to 20 hundred-weight of 112 pounds each, or 2,240 pounds, as distinguished from the "short" ton of 2,000 pounds. See Rev. St. U. S. ยง 2951 (U. S. Co.mp. St. 1907, p. 1941). But see Jones v. Giles, 10 Exch. 119, as to an English custom of reckoning a ton of iron "long weight" as 2,400 pounds.
-- Black's Law Dictionary