RELATIVITY — RUSSELL. 209 



region in the sky, which again would have been observed during 

 eclipses. 



The discrepancy remained very puzzling until Einstein's theory 

 appeared — and this theory predicts not only the fact and the direc- 

 tion of the discrepancy, but its exact amount, bringing observation 

 and calculation into beautiful accordance. 



The similar effects for the other planets are so small that they are 

 at the very limit of measurement, but even so, the Einstein theory 

 appears to fit the facts better than the old theory. 



RESULTS OF RECENT EXPERIMENTS OF ASTRONOMERS. 



This remarkable success deeply impressed astronomers, and set 

 everyone waiting with keen interest the result of the observations 

 made to determine whether rays of light passing near the sun were 

 deflected. 



To settle this question it is necessary to photograph stars in the 

 immediate neighborhood of the sun, and this can be done only at the 

 time of a total eclipse, when the moon completely hides the sun and 

 enables us to observe the stars on a nearly dark sky. 



Fortunately, the eclipse of May, 1919, afforded a very favorable 

 opportunity for such observations. The sun was eclipsed for more 

 than four minutes and was situated at the time in a region of 

 the heavens remarkably full of stars bright enough to be easily 

 photographed. 



In spite of the short interval since the conclusion of the war 

 English astronomers rose to the occasion and sent two expeditions, 

 one to Brazil and the other to an island off the African coast, 

 equipped with photographic instruments of high power and espe- 

 cially suited for the work. By extraordinary good fortune the 

 weather was clear enough at both stations to allow the obtaining of 

 valuable results. 



Every precaution was taken to secure accuracy. For example, 



after the eclipse the telescope was left in place for nearly two months 



so that the same stars might be photographed upon a dark sky, after 



the sun had moved out of the way, to obtain plates showing their 



ordinary positions to use for comparison with the eclipse plates. 



The photographs were brought to England and measured with the 

 greatest care, and the result indicates that the apparent shift of the 



stars due to the deviation of the light is unquestionably present and 



is of very nearly, if not exactly, the amount predicted by Einstein, 



the difference between the observed and calculated amounts being 



hardly greater than the very small error which is still inherent even 



in these precise observations. 



The observers, Professor Eddington of Cambridge and Doctor 



Crommelin of the Greenwich Observatory, are men of the highest 



