59° 



The National Geographic Magazine 



teresting coincidence it happens that the 

 sun's diameter is about four hundred 

 times as large as the moon's ; so that if 

 these ratios were exact and remained con- 

 stant, there would be a total eclipse when- 

 ever the three bodies were in line with 

 each other; but the moon's orbit being 

 elliptical, it is nearer its primary some- 

 times than at others, and if near it shuts 

 out more of the sun's light from our vis- 

 ions than when far away. A simple illus- 

 tration will make this point clear. If one 

 places a coin say one inch from his eye, 

 and looks toward a bright object four 

 hundred times its size, say 400 inches 

 away, the light will just be shut out of 

 view. If the coin be moved away half 

 an inch, some of the light will be seen 

 around the edge of the coin, but if moved 

 nearer it will be cut out entirely and the 

 shadow of the coin will cover the eye. 

 When the moon moving in its orbit is 

 farthest from the earth in the direction 

 of the sun, the light of the sun will not 

 be completely obscured from us and the 

 moon's shadow will not reach the earth. 

 Such a phase is called an annular eclipse 

 because a bright ring is seen around the 

 black disk of the moon. When the moon 

 is nearest the earth, the light of the sun 

 will be cut off completely and a shadow 

 with a maximum width of about, 160 

 miles will form 'and travel along the 

 earth's surface as the moon moves in its 

 orbit. If it were possible for an observer 

 to be stationed on the moon at this time, 

 he might see the shadow of his own globe 

 depicted as a little dot on the bright side 

 of our earth. 



CHOOSING THE POINT OF OBSERVATION 



At the time of the eclipse last year the 

 moon's shadow traversed a belt of the 

 earth's surface about 120 miles wide, 

 striking the earth first in British America, 

 moving across Labrador into the Atlantic 

 Ocean, across the Atlantic, thence over 

 Spain in a southeasterly direction, the 

 Mediterranean, Algeria', Tunis, and 

 southern Egypt. 



In British America the eclipse began 

 soon after daylight, but the low altitude 



of the sun at this time of the day tended 

 to lessen the value of such observations 

 as should be made ; but, waiving this 

 drawback, the great amount of fog which 

 usually covers the coast of Labrador in 

 summer made it highly probable that the 

 sun would not be seen at all. These con- 

 siderations led me to eliminate the Ameri- 

 can Continent from the problem of eclipse 

 stations. As afterward learned, nearly 

 the whole of eastern North America was 

 dominated by a heavy storm of large 

 extent during the whole day of August 

 30 and no observations were made of the 

 eclipse. Owing to the great importance 

 to science of the eclipse of 1905, astrono- 

 mers and meteorologists for several pre- 

 ceding years carried on an exhaustive 

 study of the physical characteristics of 

 the countries where the eclipse would be 

 total. In general, Spain offered the great- 

 est inducements to astronomers to ob- 

 serve the eclipse, as there it would take 

 place soon after noon, when the sun was 

 high in the heavens, relieving the obser- 

 vations of a great amount of refraction. 

 Practically all the nations of Europe sent 

 parties thither to observe the eclipse. 



Spain has three distinct geographical 

 features, where the meteorological condi- 

 tions are different: First, the lowlands 

 of the east coast of Spain are affected by 

 the general meteorological conditions of 

 the Mediterranean Sea, which were fav- 

 orable for good weather during August. 

 Second, the high plateau country of cen- 

 tral Spain is usually very dry during 

 August, except that frequent thunder- 

 storms occur in the afternoon. As the 

 eclipse would take place between noon 

 and 2 p. m., the probability of the sky 

 being free from clouds was good. Third, 

 the mountainous region of western Spain 

 being a stormy section itself, the storms 

 passing over from the Atlantic Ocean 

 frequently breaking here, the mountains 

 thus acted as a buffer for eastern sections 

 of the country. 



As the maximum duration of totality 

 occurred in Spain and as predictions 

 pointed generally to good weather, it was 

 decided to locate parties there. Moreover, 



