Also 7 lech, 7–9 letch, 9 leech. [app. f. LEACH v.2 (though recorded much earlier than the vb. in the cognate sense); in senses 1–3 prob. short for attributive combs. (LETCH sb.1, ditch or pool, is etymologically identical.)]
1. A perforated vessel or trough used for making lye from wood ashes by pouring water over them. Obs. exc. dial.
1673. Ray, Journ. Low C. (1738), I. 172. This powder they mingle with a little slaked lime … which they put into letches or troughs, and pouring water upon them make the lixivium. Ibid. (1674–91), S. & E. C. Words, 104. A Letch or Lech.
1840. Spurdens, Suppl. to Forby, Leach.
1894. Harper’s Mag., April, 810/2. Her elbow struck the leach and knocked it into the soap-kettle.
2. Tanning. (See quot. 1886.)
1777. Macbride, in Phil. Trans., LXVIII. 114. The ooze is made by macerating the bark in common water, in a particular set of holes or pits, which … are termed letches.
1852. Morfit, Tanning & Currying (1853), 22. The application of heat to bark in leaches.
1875. Knight, Dict. Mech., s.v., In the bark-leach, the bark is contained between two perforated horizontal partitions in the leach.
1886. W. A. Harris, Techn. Dict. Fire Insur., Leaches, in tanneries, are the pits in which the tan-liquors are mixed, as distinguished from the tan-pits, in which the hides are steeped.
3. Salt-making. (See quot.)
1886. Cheshire Gloss., Leach, salt-making term; the brine (fully saturated) which drains from the salt, or is left in the pan when the salt is drawn out. Formerly called ‘leach-brine.’
4. a. The action of ‘leaching.’ b. (See quot.)
1828–32. Webster, Leach, a quantity of wood ashes, through which water passes, and thus imbibes the alkali.
5. attrib.: † leach-brine = sense 3; leach-hole (see quot. and cf. sense 4 of the vb.); leach-tank, a tank for leaching metallic ores; † leach-trough (see quot.).
1669. Phil. Trans., IV. 1065. *Leach-brine, which is such Brine, as runs from their salt, when ’tis taken up before it hardens.
c. 1682. J. Collins, Salt & Fishery, 56. Cheshire Salt-Workers call the Liquor that drops from their Salt, being put into Wicker-baskets, Leach Brine.
1857. Thoreau, Maine W., xvi. (1863), 313. A *‘leach hole’ through which the pond leaked out.
1877. Raymond, Statist. Mines & Mining, 403. From this line of wooden tubing the bath is to be conducted to each *leach-tank by an India-rubber tube.
1686. Plot, Staffordsh., 94. Through these being set in the *Leach-troughs the salt drains it self dry in 3 hours time.
