KEY AND INDEX 



Comet. See "The Progress of Modern Astronomy," Vol. Ill, 

 p. 19; in particular p. 38. 



Compound Engine. A steam engine in which the steam, after 

 acting on a piston in one cylinder, escapes, not into the air, but 

 into another cylinder, where it acts on a second piston. A third 

 and fourth cylinder may be added (triple and quadruple expan- 

 sion). The compound engine was invented by Hornblower in 

 1784. See "Compound Engines," Vol. VI, p. 117. 



Conservation of Energy. See "Energy." 



Cordite. A compound having great explosive energy. It is 

 composed of 58 parts of nitroglycerine, 37 parts of guncotton, and 

 5 parts vaseline. It was patented by Sir F. A. Abel and Professor 

 (now Sir James) Dewar, of England. 



Cosmology. The system of the universe or cosmos, as 

 variously interpreted by successive generations of astronomers 

 and philosophers. The cosmological system of the Egyptians 

 and Babylonians were fantastic; those of the later Greeks and 

 Romans (see Ptolemy) conceived the earth as the central body; 

 the true (helio-centric) theory dates from Copernicus. For 

 the cosmological system of the Egyptians, see "Ideas of Cos- 

 mology," Vol. I, p. 41. For that of the Babylonians, see "Baby- 

 lonian Astronomy," Vol. I, p. 61. For the true theory, see "The 

 New Cosmology," Vol. II, p. 52. 



Cotton Fabrics. Fabrics made of threads spun from fibers of 

 the seed-pod of the cotton plant. Cotton fabrics of great 

 delicacy of texture have been made in India from the earliest 

 times. A revolution in the cotton spinning and weaving indus- 

 tries was brought about, toward the close of the eighteenth 

 century, through the inventions of Hargreaves, Arkwright, 

 Crompton, the Kays, Cartwright, and Jacquard. See "An In- 

 dustrial Revolution," Vol. IX, p. 6; and "The Manufacture of 

 Textiles," Vol. IX, p. 38. 



Cotton-gin. An apparatus for separating the seeds from the 

 cotton fiber, invented in 1793 by Eli Whitney; it effected a 

 virtual revolution in the cotton-raising industry. See "Eli 

 Whitney and the Cotton-gin," Vol. IX, p. 8. 



Crane. An apparatus (otherwise known as a derrick) for 

 hoisting heavy bodies with the aid of ropes and pulleys, actuated 

 sometimes by hand, sometimes by horse power, or steam, or 

 electricity. In its primitive form it has been used from the 

 earliest historical period. See "Archimedes of Syracuse and the 



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