SOME RECENT ASTRONOMICAL EVENTS. 161 



But in connection with these observations were others which are of 

 remarkable interest, for it appeared that the brightness of the planet 

 varied extraordinarily. In February, 19Ul, it was found by European 

 astronomers that rapid variations occurred to the amount of two whole 

 stellar magnitudes, which would be equivalent to a variation of 600 

 per cent! More recent observations show that the range of bright- 

 ness diminished so that at the middle of May there was apparently less 

 than a tenth of a magnitude variation. The extraordinary amount of 

 these fluctuations in the brightness of a planet almost baffles explana- 

 tion, and several theories have been tentativeh" proposed, none of 

 which, however, as j^et is established. Among these explanations are 

 that the planet is of unequal reflecting power on difierent portions of 

 its surface: that the variation is due to the inclination of its axis taken 

 in connection with a very eccentric form; or that it is even double, as 

 has been assumed by M. Andre and others, by whom it has been sug- 

 gested that there may be two single bodies alternately eclipsing each 

 other. In any of these explanations it is extremeh' difficult, as has 

 been said, to account reasonably for the very remarkable variations of 

 lu'ightness. The question is complicated by the velocity of light, the 

 varying distance of the sun and the earth, the phase of the planet and 

 the direction of its axis of rotation, all of which, while they make 

 numerical computations arduous, yet may furnish valuable checks on 

 the trustworthiness of any theories which may bo proposed. 



.5. 'the TOTAL SOLAR ECLIPSE OF MAY IS, 1901. 



The total solar eclipse of ^lay 18, 1901, which occurred over a belt 

 extending from the island of Mauritius across the Indian Ocean and 

 through se^"eral of the large islands of the Dutch East Indies was at 

 its maximum over six minutes long, and hence gave rise to many 

 observing expeditions, although the chances for favorable observing 

 weather were regarded as precarious in the.se tropical regions. Most 

 of the observers selected the west coast of the island of Sumatra for 

 their post of observ^ation, though some went to Mauritius, others to an 

 island ofT the east coast of Sumatra, and still a few others, I believe, to 

 Borneo. The nations represented on these expeditions included the 

 Netherlands, the United States, Great Britain, France, Russia, and 

 Japan. The Cnited States seiit the greater number of parties, while 

 the Netherlands, on account of its control of the island of Sumatra, 

 where the observations were conducted, had the most numerous 

 observers and the most extensive programme. 



The United States observers occupied seven stations, all on or near 

 the west coast of Sumatra, excepting the Amherst College expedition, 

 whicli was stationed on a small island east of Sumatra. 



England sent three parties, one stationed on the island of Mauritius, 

 and the other two on or near tiie west coast of Sumatra. 

 SM 1901 11 



