188G,] NEW YORK ACADEMY OF SCIENCES. 247 



wliich has greatly interfered with all such operations. It is now 

 fast clearing away, and I for one am somewhat sanguine that a 

 much greater success will be readied next winter at the Cape, 

 and perhaps even in England during the coming summer. 



Jast about the same time that tluggins was photographing in 

 England, Professor Wright was experimenting in New Haven in 

 a different way: isolating the blue and ultra-violet rays by the 

 nse of colored media, stopping out the sun's disc and receiving 

 the image of the coronal regions on a fluorescent screen. He 

 also had obtained what he believed, and still believes, to be a 

 real image of the corona, wlien the aerial haze intervened to put 

 an end to all such operations; for of course it is evident that 

 whether one operates by this method or by photography, success 

 is possible only under conditions of unusual atmospheric trans- 

 parency and purity. 



I suppose at present the predominant feeling among astrono- 

 mers is that the case is hopeless, and that Huggins and Wright 

 are mistaken. It may be so. But my own impression is that 

 they are probably correct; although, of course, the matter is still 

 in doubt. 



Inferior Planets. 



Leaving now the sun, and passing to the planetary system, 

 we come first to the subject of intra-Mercurial planets. 



The general opinion among astronomers (in which I fully con- 

 cur) is that the question has been now fairly decided in the 

 negative, i. e., it is practically certain that within the orbit of 

 Mercury there is no planet of a diameter as large as five hundred 

 miles, probably not one hundred. If such a one existed, it 

 could not have failed to be discovered by the wide-angled photo- 

 graphs taken at the eclipses of 1882 and 1883, to say nothing of 

 the visual observations. Of course, it is well known that at the 

 eclipse of 1878 Professor Watson supposed he had discovered 

 two such bodies, and his extensive experience and his high 

 authority led, for a time, to a pretty general acceptance of his 

 conclusion. I notice that Dr. Ball, even very lately, in his 

 " Study of the Heavens," is still disposed to credit the discovery. 

 But Dr. Peters, by a masterly discussion of the circumstances 

 of the observations themselves, and a comparison with the star 

 maps, has shown that it is almost certain that Watson really 

 saw only the two stars Theta and Zeta Cancri. In the same 

 paper also, Peters examined all the observations of small, dark 

 spots crossing the sun's disc which, up to that date (1879), had 

 been made by Leverrier and others the ground for their belief in 

 "Vulcan;" and he shows that they really afford no sufficient 

 ground for the conclusion. As to Mr. Swift's supposed obeerva- 



