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French Revolutionary calendar

(Encyclopedia)French Revolutionary calendar, the official calendar of France, Nov. 24, 1793–Dec. 31, 1805. Its introduction was decreed by the Convention on Oct. 5, 1793, but it was computed from Sept. 22, 1792, ...

Gram's stain

(Encyclopedia)Gram's stain, laboratory staining technique that distinguishes between two groups of bacteria by the identification of differences in the structure of their cell walls. The Gram stain, named after its...

frost

(Encyclopedia)frost or hoarfrost, ice formed by the condensation of atmospheric water vapor on a surface when the temperature of the surface is below 32℉ (0℃). In the formation of frost, a gas (water vapor) is ...

diatom

(Encyclopedia)diatom dīˈətŏmˌ, –tōmˌ [key], unicellular organism of the kingdom Protista, characterized by a silica shell of often intricate and beautiful sculpturing. Most diatoms exist singly, although s...

marble

(Encyclopedia)marble, metamorphic rock composed wholly or in large part of calcite or dolomite crystals, the crystalline texture being the result of metamorphism of limestone by heat and pressure. The term marble i...

gnu

(Encyclopedia)gnu wĭlˈdəbēstˌ [key], large African antelope, genus Connochaetes. Its heavy head and humped shoulders resemble those of a buffalo, while the compact hindquarters are like those of a horse. The g...

gonadotropic hormone

(Encyclopedia)gonadotropic hormone gōˌnădətrŏpˈĭk [key] or gonadotropin, any one of three glycoprotein (see protein) hormones released by either the anterior pituitary gland or the placenta (the organ in whi...

hygrometer

(Encyclopedia)hygrometer hīgrŏmˈətər [key], instrument used to measure the moisture content of a gas, as in determining the relative humidity of air. The temperature at which dew or frost forms is a measure of...

feathers

(Encyclopedia)CE5 Structure of a bird feather feathers, outgrowths of the skin, constituting the plumage of birds. Feathers grow only along certain definite tracts (pterylae), which vary in different groups of ...

rattlesnake

(Encyclopedia)rattlesnake, poisonous New World snake of the pit viper family, distinguished by a rattle at the end of the tail. The head is triangular, being widened at the base. The rattle is a series of dried, ho...