302 



THE CENTURY BOOK OF FACTS. 



several stage lines. Since 1895 the construc- 

 tion of automobiles has been carried on with 

 great energy, and many improvements have 

 been made. So far the most satisfactory re- 

 sults have been obtained with the steam, oil, 

 and electric carriages. Tn tire construction 

 the pneumatic tire occupies the first place in 

 public favor, although solid rubber tires are 

 largely employed. The highest speed is ob- 

 tained by use of light oils, preferably gasoline ; 

 steam motors are most successfully used with 

 heavy trucks and vans ; the electric motor has 

 given the best satisfaction when employed on 

 vehicles for city cab and carriage work and 

 short radius runs. 



^Eolian Harp was the invention, it is be- 

 lieved, of Athanasius Kircher, who lived in 

 the seventeenth century, and it is so called 

 from ^Eolus, the god or ruler of the winds. 

 It is a simple musical instrument, the sounds 

 of which are produced by the vibrations of 

 strings moved by wind. It may be composed 

 of a rectangular box made of thin boards, five 

 or six inches deep and about the same width, 

 and of a length sufficient to extend across the 

 window it is to be set at, so that the breeze 

 coming in can sweep over it. At the top of 

 each end of the box a strip of wood is glued, 

 about a half-inch in height ; the strings are 

 then stretched lengthwise across the top of the 

 box, and may be tuned in unison by means of 

 pegs constructed to control their tension, as in 

 the case of a violin. The sounds produced by 

 the rising and falling wind, in passing over 

 the strings-, are of a drowsy and lulling charac- 

 ter, and have been beautifully described by the 

 poet Thomson as supplying the most suitable 

 kind of music for the Castle of Indolence. 



Aerial Navigation. Pilatre des Hosiers 

 made the first balloon ascension at Paris, No- 

 vember 21, 1783. His balloon was inflated 

 with heated air. December 1, 1783, an ascen- 

 sion was made by M. Charles, a professor of 

 Natural Philosophy, at Paris, and at about the 

 same time successful ascensions were also made 

 by Messrs. Rittenhouse and Hopkins, of Phila- 

 delphia, hydrogen gas being used in these in- 

 stances for inflating purposes. The valve at 

 the top of the balloon, and' the hoop attached 

 to the balloon with netting, by which is sus- 

 pended the car, are the inventions of M. 

 Charles. In 1785 a successful passage of the 

 English Channel was made by M. Blanchard, 

 the first professional aeronaut, and an Ameri- 

 can traveler named Dr. Jeffries. The use of 

 ropes for the purpose of steadying balloons was 

 first adopted by M. Gay-Lussac, in 1803. 

 From 1852 to 1884 French, German, and 

 American aeronauts labored with degrees of 

 Success to improve the method of construction 



and to invent a means for the propulsion of 

 balloons, and in the latter year Captains Ren- 

 ard and Krebs produced an air ship which 

 was considered the crowning effort in this 

 line of invention. This ship was a cigar- 

 shaped balloon, carrying a platform, on 

 which the steering and propelling apparatus 

 was placed. The balloon was made of strong 

 silk and covered with a light netting of cords. 

 It was 197 feet long and 39 feet in diameter. 

 To the netting was suspended the platform, 131 

 feet long and 10 feet broad, on the front of 

 which was fixed the propeller, a screw of light, 

 wooden framework and air-tight cloth. The 

 rudder was at the rear of the platform. The 

 propeller was driven by electricity, generated 

 by a dynamo, which was in turn driven by 

 stored electricity. The first ascension of this 

 ship fully satisfied the most sanguine expecta- 

 tions of its builders. It was driven seven 



: miles and back in the space of forty minutes, 

 and obeyed fully every movement of the rudder. 

 During the siege of Paris, in the Franco-Ger- 

 man war of 1870-71 , ballooning was extensively 



| used by the besieged for communication with 

 the outer world, and also by the besiegers for 

 military purposes, and since that date military 

 ballooning has become an important subject of 

 study and experiment by soldiers. 



American Clocks and Watches. 

 The first attempt to manufacture watches or 

 clocks on a large scale in America was made 

 by Eli Terry, a Connecticut Yankee, who in- 

 vented wooden wheels for clocks in 1792. In 

 1837 Chauncey Jerome, of Massachusetts, first 

 applied machinery to the making of metal- 

 wheeled clocks, and as a result drove the 

 wooden-wheeled clocks out of the market. 

 The manufacture of watches by machinery, 

 which has since become such an important 

 business, was begun at Roxbury, Mass., in 

 1850, and was continued there until 1854, when 

 the works were removed to Waltham. 



Archimedes, Principle of. Archi- 

 medes, the most celebrated of ancient mathe- 

 maticians; was born at Syracuse about 287 



j B. C. He is said to have been a kinsman of 

 King Hiero, though he does not seem to have 

 held any public office, but devoted himself en- 



I tirely to science. He is the only one of the 



j ancients who contributed anything satisfactory 

 on the theory of mechanics and on hydrostat- 

 ics. He first established the truth that a 

 body plunged in a fluid loses exactly as much 

 of its weight as is equal to the weight of the 

 fluid displaced by it. This is one of the most 

 important principles in the science of hydro- 

 statics, and is called by his name. It was by 

 this law that he determined how much alloy 

 the goldsmith, whom Hiero had commissioned 



