ASTRONOMY AND METEOROLOGY. 31 D 



from this that the corona is self-luminous, since polarization is 

 produced only by specular, and not by diffuse, reflection. 



The spectrum of the corona was observed in the following 

 manner: A common chemical spectroscope was used ; but instead 

 of attaching it to a telescope, it was merely pointed in the proper 

 direction a short time before totality. As its field of view was 

 7 or 8 degrees in diameter, the sun remained in it for a consider- 

 able time, and the spectrum obtained was that'due to the corona, 

 protuberances, and sky near the sun. On lool^ing through the in- 

 strument during totality, a continuous spectrum was seen free from 

 dark lines, but containing two or three bright ones, — one near E, 

 and a second near C. At the time, I supposed that these were due 

 to the protuberances ; but Professor Young, with a large spectro- 

 scope of 5 prisms, found a line near E which remained visible 

 even when the image of the protuberance was moved o& the slit, 

 and therefore inferred that it was due to the corona. He also 

 found the continuous spectrum free from dark lines, and that 

 one, perhaps three, of the bright lines coincide with those of the 

 aurora borealis. These results would lead to the belief that the 

 corona is self-luminous, the bright lines rendering its gaseous 

 nature probable. If it is a j^art of the sun, even the remoter por- 

 tions are one hundred times as near as the earth, and would receive 

 ten thousand times as much heat, which would be sufficient to 

 raise any known substance to incandescence. 



Other observations, however, point to quite a different conclu- 

 sion. A thermometer with blackened bulb was exposed to the 

 sun's rays, and the temperature recorded every 5 minutes. I 

 found that it began to rise some time before contact, descending 

 again as soon as the moon's limb became visible. It did not reach 

 its former temperature until about a quarter of an hour after the 

 eclipse began, or until a seventh of the sun's disc was obscured. 

 The approach of the moon, therefore, appeared to cause an in- 

 crease in the sun's heat. The amount of the change was only 

 about 1.3° C, the total difference between this thermometer and 

 one in the shade being about 18° C, or in the ratio of 1 to 14. 

 This fraction is but one-half of that given above, owing, perhaps, 

 to the diminution of heat on the borders of the sun. During 

 totality, the difference between the two thermometers was almost 

 nothing. In examining the photographs taken by the party, it 

 was noticed that, while the light diminished near the edsfe of the 

 sun, the moon's limb was very distinct, and that there was a 

 marked increase in the light of the parts nearest it. It was sug- 

 gested that this might be a subjective effect; but an examination 

 of the photographs is sufficient to convince any one that the ap- 

 pearance is a real one. The glass positives especially show that 

 this effect extends over a large part of the sun's disc. The expo- 

 sure was rendered instantaneous by passing a diaphragm with a 

 slit in it in front of the camera, the rapidity of motion being regu- 

 lated by a series of springs. Any irregularity in the motion 

 would cause variations in shade in the photographs ; but these 

 would form bands parallel to the slit, while the shade mentioned 

 above was not parallel to it, and was curved so as U) follow the 



