Popular Science Monthly 



883 



date in question, and such information 

 always plays an important part in the 

 selection of sites for eclipse observations. 

 Generally speaking the chances of favor- 

 able weather are best along a line from 

 eastern Oregon through Idaho and Colo- 

 rado, and this will be a favorite part of 

 the track for the further reason that the 

 sun will be higher in the sky at the time 

 of the eclipse than farther east. 



The world over there are about 70 

 total eclipses of the sun in the course of a 

 century, but at any one place on the 

 globe there is, on an average, only one in 

 about 360 years. In the whole present 

 territory of the United States (outlying 

 possessions not included) there were only 

 eight total solar eclipses during the nine- 

 teenth century, and there will be the 

 same number during the present century: 

 viz, in 1918, 1923, 1925, 1945, 1954, 

 1979, 1984 and 1994. 



A Case Where the Moon Obscures 

 the Sun 



The fundamental facts relating to a 

 solar eclipse are quite simple. The 

 moon, in her monthly revolution around 

 the earth, occasionally passes between 

 us and the sun. The moon has no light 

 of her ow^n, and when she shines it is 

 by reflected sunlight. In a solar eclipse 

 her unilluminated side is turned toward 

 us, so that we see her as a black disk, 

 intervening in front of the sun. The 

 reporters who write up scientific events 

 for the newspapers often refer to this 

 disk as "the shadow," through confusion 



The principal heavenly bodies, which will be visible near the 

 sun [during the eclipse. Although many astronomers have 

 given up the hope that any planet or planets moving within 

 the orbit of Mercury, the planet nearest the sun, will ever be 

 found, the search will be continued during the coming eclipse 



with eclipses of the moon, in which the 

 darkening is due to the shadow of the 

 earth. What we see is not a shadow, but 

 the moon itself. The sun's diameter is 

 about 400 times as great as the moon's, 

 and the sun's average distance from the 

 earth is about 390 times that of the moon. 

 The attached diagram, which is correctly 

 drawn to scale, shows the long, tapering 

 shadow cast by the moon as she revolves 

 through space, and shows why there is 

 only a small area of the earth's surface 

 from w'hich, at any one time, the sun is 

 completely hidden by the moon. Owing 

 to variations in the distance of the moon 

 and the length of her shadow, there are 

 some eclipses in which the latter does 

 not reach all the way to the earth. Under 

 these circumstances an observer directly 

 in the line passing through the sun and 

 moon sees, at the time of eclipse, a circle 

 of sunlight extending all around the lunar 

 disk, and the eclipse is said to be "an- 

 nular." 



The Moon's Shadow a Fast Traveler 



The shadow cone on June 8 will first touch 

 the earth at sunrise in the Pacific Ocean, 

 not' far south of Japan. Thence it will 

 sweep eastward, entering the United 

 States in southwestern Washington at 

 2:55 P.M., Pacific Standard Time. It 

 will then be traveling at a speed of 33 

 miles a minute. Striking southeast, it 

 will cross, the Mississippi River at 

 5:37 P. M., Central Time, reach the 

 coast of Florida at 6:42 p. m., Eastern 

 Time, and leave the earth after reach- 

 ing the vicinity of 

 the Bahamas at sunset. 

 The actual time re- 

 quired for the journey 

 across the United States 

 (from 2:55 P. M., Pacific 

 Time, to 6:42 P.M., 

 Eastern Time) will be 

 47 minutes. "Day- 

 light saving" necessi- 

 tates the adding of an 

 hour to these times. • 



The coming eclipse 

 will be observed by par- 

 ties from all the leading 

 observatories of Amer- 

 ica. But for the un- 

 happy state of public 

 affairs abroad, we should 



