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mining

(Encyclopedia)mining, extraction of solid mineral resources from the earth. These resources include ores, which contain commercially valuable amounts of metals, such as iron and aluminum; precious stones, such as d...

promethium

(Encyclopedia)promethium prōmēˈthēəm [key], artificially produced radioactive chemical element; symbol Pm; at. no. 61; mass no. of most stable isotope 145; m.p. 1,042℃; b.p. 3,000℃ (estimated); sp. gr. unk...

Civilis

(Encyclopedia)Civilis (Julius Civilis) sĭvīˈlĭs [key], fl. a.d. 70, Batavian chief who chose the unsettled period at the fall of Nero to raise a revolt in Germany, which quickly spread to Gaul (a.d. 69–70). I...

color index

(Encyclopedia)color index, in astronomy, difference in an object's brightness as recorded between any two well-defined bands of the electromagnetic spectrum by using optical filters of different colors. If blue and...

Dyson, Sir Frank Watson

(Encyclopedia)Dyson, Sir Frank Watson dīˈsən [key], 1868–1939, English astronomer, b. Ashby-de-la-Zouch, grad. Cambridge. He was astronomer royal of Scotland (1905–10) and of England (from 1910). As director...

mezzotint

(Encyclopedia)mezzotint mĕtˈsətĭnt, mĕdˈzə–, mĕzˈə– [key] [Ital.,=halftint], method of copper or steel engraving in tone. A Dutch officer, Ludwig von Siegen, is given credit for the invention of mezzo...

Mott, Sir Nevill

(Encyclopedia)Mott, Sir Nevill, 1905–96, British physicist. A professor at the Univ. of Bristol (1933–54) and the Univ. of Cambridge (1954–71), Mott won the Nobel Prize in Physics in 1977 for a lifetime of re...

optical activity

(Encyclopedia)optical activity, the ability of asymmetric compounds to rotate the orientation of planar polarized light. Such compounds and their mirror images are know as enantiomers, or optical isomers. Although ...

Nemours, Louis Charles Philippe Raphaël d'Orléans, duc de

(Encyclopedia)Nemours, Louis Charles Philippe Raphaël d'Orléans, duc de lwē shärl fēlēpˈ räfäĕlˈ dôrlāäNˈ dük də nəmo͞orˈ [key], 1814–96, French prince; second son of King Louis Philippe. In 1...

photoengraving

(Encyclopedia)photoengraving, photomechanical process in the graphic arts, used principally for reproducing illustrations. The subject is photographed, and the image is recorded on a sensitized metal plate, which i...