Rust
2 of the 6 encyclopedias on this shelf carry an entry for Rust. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
in metallurgy, a rough spot on the surface of a metal. Iron rust is typical. It is a reddish or orange-yellow stain due to a combination of the metal and oxygen derived from moist air. Rusting has been called a slow combustion or burning. In botany rust is a decayed spot due to the growth of a small plant--a parasitic fungus--that eats away the plant on which it lives. Rusted oats, for example, are oats whose stalks have been badly eaten by microscopic plants whose colonies have lodged in spots on the leaves and stems of the oats. Rusts spread by means of dust-like spores and are of many kinds, one or more for each of a large number of fruits and field crops and vegetables. They usually grow unnoticed until they are ready to cast off spores when they break out in brown blotches or spots. Crowded plants and moist weather are likely to develop rusty grain. See Fungus
Collier's New Encyclopedia (1921)
the yellowish coat of peroxide which forms on the surface of iron exposed to moist atmosphere. To prevent the rusting of iron utensils, oil, paint, varnish, plumbago, grease, or any substance which will protect the metal from the moist air, may be employed. In all ordinary circumstances iron decomposes water, abstracts the oxygen, and combines with it, thus forming rust. In botany, a disease of plants, which shows itself on the stems and leaves of many plants, and on the ears of grasses, both of the cereal grasses and of many pasture and forage grasses, in brown, yellow, or orange colored spots, and after destroying the epidermis of the plant assumes the form of a powder which soils the fingers when touched.
What Has Changed in the Last Century
Collier's 1921 description of rust as a "yellowish coat of peroxide" formed when "iron decomposes water" was close but not quite right: rust is hydrated iron(III) oxide, and it is now understood as an electrochemical process, with anodic and cathodic areas on the metal surface, worked out in detail by Ulick Evans and others from the 1920s. The remedies listed — oil, paint, varnish, plumbago, grease — have been joined by galvanising, sacrificial-anode and impressed-current cathodic protection, and above all by stainless steel, which Harry Brearley had patented in Sheffield only a few years before Collier's wrote. On the botanical side, both accounts correctly identify rusts as parasitic fungi spread by dust-like spores; what has changed is the fight against them. The barberry, the alternate host of wheat stem rust, was the target of a US eradication campaign begun in 1918, and Norman Borlaug's rust-resistant wheats of the 1940s onward transformed world harvests — though the aggressive Ug99 strain identified in Uganda in 1998 showed the problem is far from closed.
Written for this edition, 2026.