SOLAR ECLIPSE OF MAY 28, 1900. 155 



The important result was that the corona gaxe a positive indication 

 of heat as compared with the moon. 



This heat, though certain, was, however, too slight to be subdivided 

 b}" the dispersion of the prism with the means at hand. 



The negatives taken to depict the outer corona show from three to 

 four solar diameters extension for the longest streamers. The equa- 

 torial "wings" as they recede from the sun are finally lost in an illu- 

 minated sky, without an}^ indication of having actually come to an end. 



No attempt to carefully examine the plates taken for intramercurial 

 planets has yet been possible. It is, however, as has been remarked, 

 doubtful if very faint objects will be found, in consideration of the 

 considerable sky illumination during totality. However, Pleione in 

 the Pleiades (a star of the 6.3 magnitude) is plainly seen on one of the 

 plates and some smaller ones are descernible. 



On the whole, the expedition may be considered as promising to be 

 very satisfactory in its results, and that it was so is largely owing not 

 only to the efficient care of IVIr. Al)bot, but to the many gentlemen 

 who have assisted me with the loan of valuable apparatus, with coun- 

 sel, with voluntary service, and with painstaking observation, to one 

 and all of whom I desire to express my obligations. 



Smithsonian Institution, 



Washington, D. C, Junp 9, 1900. 



giving zero ; on the bright moon, giving phis 55, and on the night sky near the 

 moon, giving minus 30. 



From my study of the visual photometric observations made at Pikes Peak in 1878 

 and at other places, it appears that the average visual brightness of the port ion (if the 

 corona covering the bolometer at Wadesboro was approximately equal to that of the 

 full moon. 



We infer, then, that the full moon being of the average brightness of the observed 

 portion of the inner corona, the bolometric effect of its visual radiation may be sup- 

 posed to be equal to that of the corona, but the observations above recorded show 

 that the total radiations from the moon being 50 plus 30, or 80 bolometric divisions, 

 are 16 times as great as the radiations from the inner corona, being only 5 (i. e., — 13 

 +18) sucli divisions, and hence it may be supposed that the corona lacks that large 

 amount of infrared radiation which is jiroper to the moon's spectrum. 



The moon's spet-trum, however, is that of a heated solid body, and all heated solid 

 bodies, and heated gaseous bodies as well, send to the bolometer large amovmts of 

 infrared radiation. So far, then, we might conclude that the inner corona has not 

 the radiations of a hot solid or gaseous body, but owing to the lack of a contempo- 

 rary measure of the sky radiation just outside the corona, and of a full knowledge 

 of the influences that the atmospheric radiations proper would have on our ability 

 to discriminate this radiation, the above conclusions, though highly probable, are 

 not presented as being absolutely final, and it is hoped to repeat them at the forth- 

 coming eclipse in May, 1901. (S. P. L. ) 



