TECHNICAL INDEX AND GLOSSARY 



Etching. A process of engraving, in which the artist scratches 

 the waxed surface of the metallic plate with a pointed instru- 

 ment, the mechanical process being completed by the action of 

 acids, which "bite" the plate only in places thus exposed. See 

 -Etching," Vol. VIII, p. 195. 



Ether. The hypothetical substance filling all space, "pene- 

 trating between the molecules of matter as air between the 

 leaves of trees." One theory of matter supposes all material 

 substances to be composed of vortex rings of ether. Undula- 

 tions in the ethereal medium are supposed to constitute the 

 manifestations which our senses interpret as light and radiant 

 heat. For the investigation of the early workers, such as 

 Young and Clerk-Maxwell, to the most recent, see "The Ether 

 and Ponderable Matter," Vol. Ill, p. 283. 



Evolution, The Theory of Organic. The doctrine which 

 teaches that higher organic forms have developed sequentially 

 from lower ones, through various channels, all of which lead 

 back to a primordial form of proto-plasmic being. See Darwin, 

 Erasmus Darwin, Lamarck, Haeckel, and "Theories of Organic 

 Evolution," Vol. IV, p. 140. 



Faraday Tubes. Lines of magnetic force, as observed by 

 Faraday, and theoretically explained by him. These "tubes" 

 radiate in all directions into space, in loops of all sizes, which 

 connect the poles of a magnet. They have been invoked to 

 explain many phenomena of nature, including "action at a dis- 

 tance." See "Modern Views," Vol. VI, p. 153. 



Fire-damp. Name given by miners to the explosive or in- 

 flammable gases that sometimes develop in mines, in contradis- 

 tinction to the non-explosive carbonic acid gas, which they term 

 "choke damp." See "Carbon Dioxide Gas," of the present index. 



Fossil Beds. Strata containing large numbers of fossils; 

 usually from remains originally deposited in an ancient lake 

 bed. Some of the most important fossil beds are found in the 

 Rocky Mountain region. See "The New Science of Paleon- 

 tology," Vol. Ill, p. 74. 



Fossil Horse. Remains of this animal, as found in the fossil 

 beds of western America, had peculiar interest, as they gave 

 tangible evidence of the truth of the evolution of hypothesis. 

 See "The New Science of Paleontology," Vol. Ill, p. 105. 



Fossil Man. Remains of prehistoric man, study of which has 

 demonstrated the great antiquity of the human race. Finds of 



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