Reservoir
2 of the 6 encyclopedias on this shelf carry an entry for Reservoir. Both are reproduced below, so you can see where they agree and where they differ.
The Encyclopedia of Founding (1892)
Dams constructed for the purpose of gathering a large quantity of metal are sometimes called reservoirs; as also are runner-basins when constructed of extraordinary dimensions to receive the molten metal from very large pouring-ladles. See DAMS; BASIN; GATHERING-METAL. Resin is a solid, inflammable substance, of vegetable origin, being obtained from various trees by making incisions in their bark and allowing the liquid to exude. This liquid is the essential oil of the plant, and holds the resin in solution. Resins are insoluble in water, but alcohol dissolves them; they are of an inflammable nature, and yield a dense, sooty smoke when burning. Mastic, sandarac, lac, copal, etc., are some of the resins from which varnishes are made, all of which are readily dissolved in such solvents as spirits of wine, oil of turpentine, methylated spirit, and wood naphtha. The evaporation of the spirit, after these varnishes have been applied, leaves a hard layer of the resin on the surface of the object treated. The common resin, or rosin, of commerce is obtained from the various species of pine. Gum-resins are the solidified milky exudations of plants. They consist of resin, essential oils, and a gummy substance peculiar to the plant. The ammoniacum, assafoetida, aloes, myrrh, gamboge, etc., belong to this class; they are all soluble in rectified alcohol, and are valuable as medicinal agents principally. Elastic gums, as caoutchouc or india-rubber and gutta-percha, are valuable in the arts and manufactures; the former consists of a thick milky juice of certain trees growing in tropical countries, and is a mixture of several hydrocarbons with turpentine oil. When pure it is nearly white. It will soften in boiling water, but not dissolve; it is also insoluble in alcohol, but readily dissolves in coal naphtha, rectified oil of turpentine, pure ether, chloroform, or carbonic disulphide. Caoutchouc is rendered more permanently elastic by combining with it certain proportions of sulphur. It is then called vulcanized india-rubber. See GUTTA-PERCHA; INDIA-RUBBER.
Collier's New Encyclopedia (1921)
an artificial basin in which a large quantity of water is stored. A vast system of reservoirs, called "tanks," exists in India, constructed for of irrigation. The reservoirs purposes of Spain are all of masonry; they are circular or polygon the irrigation canals onal in shape, and the interior face of the wall, which is constructed of large ashlars, is vertical. In France, Italy, and particularly in England, the preference is given to earthen dams. See DAM.
What Has Changed in the Last Century
When Collier's wrote this in 1921 the biggest reservoirs were still measured against the earthen dams of England and the masonry basins of Spain; the modern era of concrete megastructures began a decade later with Hoover Dam, whose Lake Mead began filling in 1935 and held some 35 cubic kilometres of Colorado River water. There are now roughly 58,000 large dams worldwide, among them Egypt's Aswan High Dam (1970) and China's Three Gorges (reservoir filled from 2003), the latter displacing well over a million people. The engineering questions have shifted too: reservoirs are now judged on silting up, evaporation losses, greenhouse gases from rotting drowned vegetation, and blocked fish migration, and in the United States ageing dams are increasingly being removed rather than built he Elwha in Washington came down in 2011–14 and the Klamath dams in 2023–24. The 1892 foundry sense, a basin gathering molten metal, has largely dropped out of ordinary use.
Written for this edition, 2026.