TWILIGHT 



TYLER 



to learn them by heart. The decemvirs were 

 elected to perform .their task in 452 B. c. In 

 451 they submitted ten tables of the law, and 

 the following year two others. See ROME, sub- 

 head Written Laws, page 5058. 



TWI' LIGHT, a period between "the dark 

 and the daylight," occurring immediately after 

 the sun has sunk beneath the horizon. At 

 timo the atmosphere is illuminated by a soft, 

 mellow light that gradually fades away into 

 darkness. There is a corresponding period 

 early in the morning, just before the sun rises, 

 \vhich is called dawn. The phenomenon of twi- 

 light is due to refraction and reflection of the 

 r iy, When the sun sinks from sight, 

 the rays, on passing from the ether into the 

 denser atmosphere surrounding the earth, are 

 bent at an angle and continue to reach those 

 regions from which the sun itself cannot be 

 seen. They are made visible to the observer 

 because they are reflected by dust and water 

 vapor present in the upper air. 



The duration of twilight varies greatly in 

 rent parts of the earth. This is due to the 

 same causes which affect the length of day and 

 night. It is widely believed that complete 

 darkness follows immediately on the disappear- 

 ance of the sun in the tropics, but this is not 

 ly true. Even at the equator twilight lasts 



about an hour. It has been found that twi- 

 light lasts from the time the sun sets until it 

 is eighteen degrees below the horizon. At the 

 equator, the path described by the sun across 

 the earth's surface scarcely varies; similarly 

 the length of time it takes the sun to drop 

 eighteen degrees below the horizon does not 

 vary. But as one travels north or south one 

 enters zones where the path of the sun across 

 the earth's surface changes from day to day, 

 and thus it follows that the length of twilight 

 varies. During the Arctic summer there is a 

 period when the sun never drops beneath tin- 

 horizon where summer means perpetual day. 

 Farther south the summer sun never drops as 

 much as eighteen degrees below the horizon, 

 so that twilight bridges the entire period be- 

 tween sunset and sunrise. This is true in Chris- 

 tiania, Norway, where the nights are so light 

 during June and July that the shops arc kept 

 open and people are seen on the streets all 

 night long. In the north of England, during 

 the same months, it is never really dark, and it 

 is often possible to read out-of-doors at ten 

 or eleven o'clock at night. In the prairie prov- 

 inces of Canada summer twilight continues so 

 late that the league baseball games are played 

 after seven o'clock. 

 TWILIGHT SLEEP. See ANESTHETIC. 



Qfl 



THE STORY OF THE TENTH PRESIDENT 



JLvLER, JOHN (1790-1862), an American 

 statesman, tenth President of the Unit. ,1 

 Tyli-r \\.i> Ircted as Vice-Presi'lmt . with Wil- 

 liam II II rrison as President, but tin- lat- 

 i'-ath elevated Tyler to the Presidential 

 Tyler thus was the first man to become 

 President who was not elected to that office. 

 It is a curious fact that this first "accidental 

 President" established precedents which have 

 gree by most of the 

 later Presidents who have attained this ^' 

 a similar manner. Tyler became President by 

 the votes of a party of which he was not at 

 heart a member, and in his course as President 

 he acted not according to the demands of that 



Tyler's Home in Virginia 



party but in obedience to his own 

 i -..l.-ncc made his reelection impos- 



.-ihle. just as it made impossible the rr 



ry succeeding "accidental President 

 the single exception of Roosevelt. Throughout 

 his career tin- independence of thought and 

 action was Tyler's strongest characteristi* II 

 was loyal to principles and ideals; he was loyal 

 to individuals only as they supported his prin- 

 ciples or furthered his ideals. Had he been 

 weaker and more easily influenced, his Prcsi- 

 nuiiht have beta marked by many 



menu. Even under the conditions that 

 existed it is marked by the Webtter-Ashburton 

 Treaty and the annexation of Texas. 



