1888.] President'' s Address xxxiii 



observations of which were made in Egypt. This was a year when 

 sun-spots were numerous and the appearance of the Corona fully 

 supported the connection with them previously enunciated. No 

 zodiacal streamers Avere seen, and the general aspect was very similar 

 to that of the eclipse in India eleven years earlier. The eclipse of 

 1883 was observable only from a small island in the South Pacific Ocean 

 but a considerable party of astronomers flocked there to see it ; the 

 Corona was similar to that seen in 1882. Some important results 

 were obtained, and one very suggestive one by Tacchini. He saw 

 in the spectrum of the Corona on a feeble continuous background two 

 of the bright hydro-carbon bands which are found in the spectra of 

 comets ; the observation however requires confi.rmation. So far as 

 we can say at present the Corona is certainly not a solar atmosphere 

 inasmuch as its pressure does not increase as the sun's disc is 

 approached ; it may be defined as gaseous matter constantly flowing 

 from and towards the sun or perhaps circulating round it, under the 

 action of a repulsive electrical force and of gravity. It is chiefly 

 composed of hydrogen and the unknown substance giving the green 

 ray 1474, and partly of solid or liquid particles shining with reflected 

 and inherent light, but it must be of inconceivable tenuity since 

 comets are able to pass through it without suffering any alteration 

 of velocity. 



The fact that we have only some four or five minutes a year at 

 the most for the study of these phenomena makes it highly desirable 

 that some means of observing them at any time should be discovered. 

 This has already been done in the case of the prominences, which are 

 now mapped daily, and an attempt has been made with the Corona., 

 From the phot o raphs taken in 1878 Dr. Huggins observed that the 

 light in the spectrum is largely confined to violet rays, and he hoped 

 to find by excluding all but these rays that the glare produced by the 

 atmosphere plus the coronal light might be sufficiently greater than 

 the glare alone to render the shape of the Corona visible. His first 

 experiments were made in 1882 and gave a fair promise of success ;, 

 the impressions on his plates strongly resembled the Corona in general 

 features and in details ; but the haze or dust that was present in the 

 atmosphere after the volcanic explosion in the Sunda Straits in 1883,. 

 August, put an end for a time to work in this direction. Further, 

 experiments were made by Mr. C, Ray Woods on the Riffel and atf 

 the Cape in the following years, but with no better success. The 

 eclipse of 1886 was anxiously looked forward to as a crucial 



D 



