KEY AND INDEX 



first successful aeroplane, that of the Wright Brothers (operated 

 at Kitty Hawk, North Carolina, in December, 1903), had two 

 chief planes, one above the other, and hence is called a biplane. 

 The imitative machines of Farman, Curtiss, and Cody are also 

 biplanes. The apparatus perfected by Bleriot has a single chief 

 plane, and is called a monoplane. The machine used by Hubert 

 Latham is also a monoplane. The prototype of these machines 

 is the original aerodrome of Langley, which was essentially a 

 monoplane inasmuch as its two chief portions were arranged in 

 the same horizontal plane. The box kite may be taken as the 

 prototype of the biplane. See "The Triumph of the Aeroplane," 

 Vol. VII, p. 272. 



Air-pump. A machine by means of which air or other gases 

 may be removed from an enclosed space. It was invented by 

 Otto von Guericke about 1650. See "Mariotte and von Guericke," 

 Vol. II, p. 210. 



Air-thermometer. An instrument for measuring temperature, 

 in which the change of volume of air under a constant pressure 

 is made to indicate changes in temperature. The discovery that 

 a gas expands at a uniform rate under increasing temperatures, 

 and correspondingly contracts as temperatures decrease (con- 

 stant pressure being maintained) was made independently by 

 Boyle and Mariotte in the eighteenth century. See "The Suc- 

 cessors of Galileo in Physical Science," Vol. II, p. 204 and p. 210. 



Albinism. A condition in which there is a congenital absence 

 of pigment in the hair, iris, and skin. It occurs in plants as 

 well as animals, and in all races of men. Individuals so affected 

 are called albinos. See the reference to the collection of spec- 

 imens illustrating albinism (and the opposite state of melanism) 

 in the Natural History Museum at South Kensington, London, 

 Vol. V, p. 10. 



Alchemy. The pseudo-science which sought to find a magic 

 "elixir" or "philosophers stone" that would give its possessor the 

 secret of eternal youth, and would also enable him to transmute 

 silver and perhaps the baser metals into gold. For full treat- 

 ment of the subject, see the chapter "Two Pseudo-Sciences 

 Alchemy and Astrology," Vol. II, p. 124. 



Alcohol. The commercial name for ethyl alcohol, having the 

 chemical formula C 3 H 5 O H. Alcohol results from the fermen- 

 tation of sugars and starches, and is the intoxicating principle 

 of wine and other beverages that were familiar from the earliest 

 times; but the distilled spirit as such seems to have been dis- 



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