TOTAL ECLIPSES OF THE SUN. 



251 



which, judging bj- llie results obtained by several observers during the eclipses 

 of 1870, 1878, and 1898, was at least equal to that of the full moon, it is diffi- 

 cult to understand how the light of the corona can be due largely to reflection 

 of rays from the sun, or even to the incandescence of dust particles, for from 

 sources of these kinds, which emit a great preponderance of invisible infra-red 

 rays, the bolometer would have given large positive deflections. . . The im- 

 portant result of a comparison of the radiations of the inner corona, the full 

 moon, and the daylight sky somewhat remote from the sun is that while the 

 three are roughly of equal visual brightness, the corona is effectively a cool and 

 far from intense source, while the moon and sky are effectively warm and many 

 fold richer in radiation. Hence it would appear plausible that the corona 

 merely sends out visible rays and that its light is not associated with the great 

 preponderance of long wave-length rays proper to tlie radiation from bodies at 

 a high temperature. If this be so the coronal radiation might be compared 

 with that from the positive electrical discharge in vacuum tubes, in which, as 

 researches of K. Angstrom and R. W. Wood, have shown, there is neither an 

 infra-red spectrum nor a high temperature. 



Fig. 9. South Polar Stkeameks. Eclipse of 1900. PiiuTotiRAPHED with a Telescope 

 OF 135 FEET Focal Length by Mr. Smillie, of the Smithsonian Eclip.se Party. 



These conclusions are of so great importance that it is very de- 

 sirable that the observations upon which they depend, should be 

 repeated at other eclipses. It is, therefore, very unfortunate that Mr. 

 Abbott at the recent eclipse at Sumatra was prevented by clouds from 

 carrying out the observations wliicli he had traveled so far to obtain. 

 Other observers, however, were no more fortunate. Professor E. E. 

 Barnard was provided with a telescope of 611^ feet focus, and with 

 plates forty inches square, but was prevented by clouds from obtain- 

 ing results of much value. This was the fate, also, of many other 

 observers from different countries, who had taken stations in different 

 parts of Sumatra. Results of value were obtained, however, by the 

 party from the Massachusetts Institute of Technology, whose photo- 

 graphs of the corona are unsurpassed. At the Island of Mauritius, 

 also, the English astronomers obtained valuable results. As a whole 



