TRANSACTIONS OF THE SECTIONS. 5 



been found capable of performing tlie same good service towards the compound 

 instrument consisting ot the telescope and its attached spectroscope, which it had 

 previously been known to perform towards the telescope alone. 



It is of no less importance to secure a permanent record of spectral peculiarities 

 than it is to secure a permanent record ot telescopic appearances. 



This application of photography to spectrum observations was first commenced 

 on a sufficient scale by Mr. Rutherford, of New York, and already promises to be 

 one of the most valuable aids in solar inquiry. 



In connexion with the spectroscope I ought here to mention the names of 

 Respighi and Secchi, who have done much in the examination of the solar surface 

 from day to day. It is of great importance to the advancement of our knowledge, 

 that two such competent observers are stationed in a country where the climate is 

 so favom'able to continued observation. 



The examination of the sun's surface by the spectroscope suggests many interest- 

 ing questions connected with other branches of science. One of these has already 

 been alluded to. 



I may mention two others put by Mr. Lockyer, premising, however, that at 

 pi-esent we are hardly in a position to reply to them. 



It has been asked whether the very high temperatures of the sim and of some of 

 the stars may not be sirfficientto produce the disassociation of those molecular struc- 

 tures which cannot be disassociated by any terrestrial means ; in other words, the 

 question has been raised, whether our so-called elements are really elementary 

 bodies. 



A third question is of geological interest. It has been asked whether a study of 

 the solar atmosphere may not throw some light upon the pecidiar constitution of 

 the upper strata of the earth's surface, which are known to be of less density than 

 the avei-age interior of our planet. 



If we have learned to be independent of total eclipses as far as the lower portions 

 of the solar atmosphere are concerned, it must be confessed that as yet the upper 

 portions — the outworks of the sun — can only be successfully approached on these 

 rare and precious occasions. Thanks to the various Government expeditions 

 despatched by Great Britain, by the United States, and by several Continental 

 nations — thanks, also, to the exertions of Lord Ijindsay and other astronomers — we 

 are in the possession of definite information regarding the solar corona. 



In the first place, we are now absolutely certain that a large part of this ap- 

 pendage unmistakably belongs to our luminary ; and in the next place, we know 

 that it consists, in part at least, of au ignited gas giving a peculiar spectrum, 

 which we have not yet been able to identity with tliat of any known element. 



The temptation is great to associate this spectrum with the presence of something 

 lighter than hydrogen, of the nature of which we are yet totally ignorant. 



A peculiar physical structure of the corona has likewise been suspected. On the 

 whole, we may say that this is the least known, while it is perhaps the most 

 interesting, region of solar research ; most assuredly it is well worthy of fm-ther 

 investigation. 



If we now turn our attention to matters nearer home, we find that there is a 

 difficulty in grasping the facts of terrestrial meteorology no less formidable than 

 that which assails us when we investigate solar outbreaks. The latter perplex us 

 because the sun is so far away, and because also his conditions are so different from 

 those witli which we are here familiar ; while, on the other hand, the former pei'plex 

 us because we are so intimately mixed up with them in our daily lives and actions — 

 because, in fact, the scale is so large and we are so near. The result has been that 

 until quite recentlj' our meteorological operations have been conducted by a band 

 of isolated volunteers, individually capable and skilful, but from their very isolation 

 incapable of combining together with advantage to prosecute a scientific campaign. 

 Of late, however, we have begim to perceive tliat if we are to make any advance in 

 this very interestmg and practical subject, a difierent method must be pursued, and 

 we have already reaped the first fruits of a more enlightened policy ; already 

 we have gained some knowledge of the constitution and habits of our atmo- 

 sphere. 



The researches of Wells and Tyndall have thrown much light on the cause of 



