ADDRESS. XCV 



by change of angular position, it is equally applicable to stars at all distances, 

 provided they arc bright enough to render the obsei'vations possible. It is 

 conceivable that the results of these observations may one day lead to a de- 

 termination of the motion of the solar system in space, which is more trust- 

 worthy than that which has been deduced from changes of position, as being 

 founded on a broader induction, and not confined to conclusions derived fi-om 

 the stars in our neighbourhood. Should even the solar system and the nearer 

 stars be drifting along, as Sir John Herschel suggests, with an approximately 

 common motion, like motes in a sunbeam, it is conceivable that the circum- 

 stance might thus be capable of detection. To what wide speculations are we 

 led as to the possible i^rogress of our knowledge when we put together what 

 has been accomplished in difterent branches of science ! 



I turn now to another recent application of spectral analysis. The pheno- 

 menon of a total solar eclipse is described by those who have seen it as one of 

 the most imposing that can be witnessed. The rarity of its occurrence and 

 the shortness of its duration afford, however, opportunity for only a hasty 

 study of the phenomena which may then present themselves. Among these, 

 one of the most remarkable, seen indeed before, but first brought prominently 

 into notice by the observers who watched the eclipse of July 7, 1842, consists 

 in a series of mountain-like or cloud-like luminous objects seen outside the 

 dark disk of the moon. These have been seen in subsequent total eclipses, 

 and more specially studied, by means of photogi-aphy, by Mr. Warren De La 

 Tluc in the eclipse of June 18, 1860. The result of the various observations, 

 and especially the study, which could be made at leisure, of the photographs 

 obtained by Mr. De La Eue, proved conclusively that these appendages belong 

 to the sun, not to the moon. The photographs proved further their light to 

 be remarkable for actinic power. Since that time the method of spectral 

 analysis has been elaborated ; and it seemed likely that additional informa- 

 tion bearing on the nature of these objects might be obtained by the applica- 

 tion of the sjjectroscope. Accordingly various expeditions were equipped for 

 the pitrpose of obsemug the total solar ecHpse which was to happen on 

 August 17, 1868. In o\ir own country an equatorially mounted telescope 

 provided witli a spectroscope was procured for the purpose by the Eoyal 

 Society, which was entrusted to Lieut, (now Captain) Herschel, who was going 

 out to India, one of the countries crossed by the line of tlie central sha- 

 dow. Another expedition was organized by the Royal Astronomical Society, 

 under the auspices of Major Teunant, who was foremost in pressing on the 

 attention of scientific men the importance of avaihug themselves of the 

 opportunity. 



Shortly before the conclusion of the Meeting of the Association at Norwich 

 last year, the first results of the observations were made knov\ni to the Meet- 

 ing through the agency of the electric telegraph. In a telegram sent by 

 M. Jansseu to the President of the Eoyal Society, it was announced that the 

 spectrum of the prominences was very remarkable, showing bright lines, 

 while that of the corona showed none. Brief as the message necessarily was, 

 one point was settled. The prominences could not be clouds in the strict 

 sense of the term, shining either by virtue of their own heat, or by light 

 reflected from below. They must consist of incandescent matter in the 

 gaseous form. It appeared from the more detailed accounts received by 

 post from the various observers, and put together at leisure, that except in 

 the immediate neighbourhood of the sun the light of the prominences con- 

 sisted mainly of three bright lines, of which two coincided, or nearly so, 

 with C and P, and the intermediate one nearly, but, as subsequent researches 



