DISCOVERY 



51 



Einstein, but the excess may be due partially or entirely 

 to a refraction effect by the solar corona. 



Astronomers, who are familiar with the errors in- 

 cidental to the measurement of astronomical photo- 

 graphs, accept the evidence as definitely establishing 

 the existence of the deflection ; and their verdict has 

 naturally been accepted by scientists in general. 

 Many attempts have, however, been made to show that 

 the deflection can be attributable to other causes than 

 the sun's gravitation. We have not space to enter 

 into these here, but we may add that, in the opinion of 

 those most competent to judge, these " explanations " 

 are invalid, and for the most part extremely artificial. 

 The present writer believes that the deflection can be 

 attributed only to a direct effect of the sun's gravita- 

 tional field, and that the answer to Newton's query is 

 therefore " Yes." 



Although not the special purpose of the expeditions, 

 it may be mentioned that incidentally some excellent 

 photographs of the solar corona were secured. In the 

 Plate is reproduced one of the photographs taken at 

 Sobral, showing the corona around the obscured disc 

 of the sun. The star images do not show in the repro- 

 duction, being too small to appear. The lower photo 

 shows the large prominence which was on the sun's 

 eastern limb at the time of the eclipse. Its meah 

 height is about 120,000 miles, and its length about 

 380,000 miles. Prominences can, by the use of special 

 apparatus, be observed at times other than eclipses, 

 and this particular one was imder obser^'ation at the 

 Yerkes Observatory for some time prior to the eclipse. 

 Shortly after the eclipse, the prominence broke up, 

 and within a few hours the greater part of it had 

 rapidly ascended to a height of over 400,000 miles. 

 Prominences consist mainly of incandescent hydrogen 

 gas, and are connected with the disturbances occurring 

 within the sun, which are also evidenced by sun-spots. 

 The exact nature of the physical causes underlying 

 their formation is not known. The prominence of 

 May 29, 1919, was much larger than the average, and 

 never before has so large a prominence been photo- 

 graphed during an eclipse. The splendid photographs 

 obtained of it were a welcome by-product of the 

 eclipse expeditions. 



The Cambridge University Press have undertaken to 

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 tory. This work, of which the general plan will be similar 

 to that of the Cambridge Modern and Medieval Histories, 

 will consist of eight volumes, and, beginning with an account 

 of archaeological discovery, will trace the history of Egypt 

 and Babylonia, Assyria and Persia, Greece and Rome, 

 to A.D. 324. 



The various chapters wiU I* written by specialists, and 

 will be illustrated by a series of maps; in the early sections 

 dealing with archceology, illustrations will also be included. 



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CATALYSIS IN THEORY AND PRACTICE 



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INTRODUCTION TO ANTHROPOLOGY 



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