Also dial. boother, bowder. [Shortened f. BOULDER-STONE.]
1. A water-worn rounded stone, varying in size, but properly larger than a pebble, used frequently for paving and building purposes; a cobble.
1617. Markham, Caval., I. 57. Paued with pibble boulder, or some other kind of small stone.
1811. Pinkerton, Petral., I. 265. Brown clay slate, in bowlders, found in the bed of the Alecnundra.
1837. Carlyle, Fr. Rev., I. V. ix. 256. The Bastille … sinks day by day … its ashlars and boulders tumbling down continually.
1871. Tyndall, Fragm. Science (ed. 6), I. vi. 209. Fastened the sail at the top, and loaded it with boulders at the bottom.
2. spec. Geol. A large weather-worn mass or block of stone, frequently carried by natural forces to a greater or less distance from the parent rock, and generally lying on the surface of the ground, or in superficial deposits; an erratic block.
1813. Bakewell, Introd. Geol. (1815), 73. Some of the vertical beds of rock covering the granite contain … boulders.
1830. Lyell, Princ. Geol., I. 369. Enormous rounded boulders … of trachyte and basalt.
1859. Darwin, Orig. Spec., xii. 335. Erratic boulders have … been noticed on the Rocky Mountains.
fig. 1858. Hawthorne, Fr. & It. Jrnls. (1872), I. 14. The first Napoleon … a great boulder in history.
3. transf. A lump or mass of some material; spec. in Mining, a large detached piece of ore found away from the regular lode. Also attrib. in the sense of ‘big, lumpy.’
1861. Sala, Tw. round Clock, 173. Its boulders of whitening, and its turpentine-infected bundles of firewood.
1863. Dana, Man. Geol., 537. Boulders of Native Copper have been found.
1882. Pall Mall Gaz., 31 May, 4/1. The birds will have, not some, but all of the seed; the boulder clods will never cover it.
4. Comb.: boulder-clay, a clayey deposit belonging to the ice-age, and containing boulders, etc.; boulder-drift = boulder-formation; boulder-flat, a tract of country strewed with boulders; boulder-formation, a formation or deposit consisting of mud, clay, etc., in which boulders are embedded; boulder-head, a kind of sea-wall; boulder-paving, paving made of boulders; boulder-period, the geological epoch in which boulder-formations were being produced, the Ice Age or Glacial Period; boulder-walls (see quot.).
1878. Huxley, Physiogr., xvii. 282. An icy sea, from which the *boulder clay and glacial gravels were deposited.
1884. Dawson, in Handbk. Canada, 324. Stratified sands and gravels overlying the boulder-clay.
1876. Page, Adv. Text-bk. Geol., xix. 355. The *boulder-drift is a bold and clearly-defined formation.
1884. J. Colborne, With H. Pasha, 44. The road across this *boulder-flat consisted of numerous pathways running side by side.
1845. Darwin, Voy. Nat., ix. (1873), 180. Fragments of primitive rocks derived from the surrounding *boulder-formation were very numerous. Ibid., viii. 174. The ice-transporting *boulder-period.
1738. Chambers, Cycl., *Boulder-walls, a kind of walls built of round flints or pebbles, laid in a strong mortar.
