1869.] of August 18, 1868. 51 



hitlierto opinions had been divided as to whether they belonged to 

 the sun, the moon, or were the results of refraction, &c., in our 

 own atmosphere. The highly successful photographs taken by 

 Dr. De la Eue solved this point, and proved conclusively that the 

 prominences belonged to the sun. But these photographs, whilst 

 they solved one point, raised other problems even more perplexing. 

 Assuming that the prominences belonged to the sun, it had been 

 taken for granted that they were of the nature of mountains pro- 

 jecting from the solar disc, but the photograph showed us enormous 

 masses of matter, well defined and sharp in their outline, but of a 

 size and shape perfectly incompatible with sohdity, and hanging 

 suspended several thousand miles above the surface of the sun. 

 Instead of being settled by the 1860 echpse, the problem was in 

 reality only started, and astronomers, chemists, and physicists, have 

 been looking forward eagerly to the opportunities offered last 

 August to advance some steps nearer its solution. 



It seems as if a combination of interesting researches in several 

 branches of science culminated in this one eclipse. Simultaneously 

 with the definite statement of the problem by the photographs, the 

 attention of the scientific world was forcibly directed to a new 

 instrument of physical research — the spectroscope — which was 

 destined to afibrd a complete answer to the main question. The 

 admirable researches of Bunsen and Kirchhofi"* led to the general 

 prosecution of spectroscopic research, and paved the way for the dis- 

 coveries of Kirchhofi", Foucault, Plucker, Miller, Huggins, and others. 

 The researches, especially of the latter philosopher, on the spectra 

 of the stars, nebulae, and comets, showed what a powerful instrument 

 the spectroscope would be in researches on solar physics, and espe- 

 cially in the examination of those rare phenomena only to be seen 

 during a total echpse. 



It was accordingly agreed tacitly that spectrum observations were 

 those likely to bear most fruit, and in most of the expeditions which 

 were sent out this year the spectroscope was intended to play an 

 important part. 



This great eclipse stands alone in the annals of astronomy. In 

 time of duration (nearly seven minutes at the maximum) it exceeds 

 all recorded eclipses, and more than thirty generations of astro- 

 nomers will come and go before an equal length of totality will be 

 witnessed. The eclipse observed in Spain only gave the observers 

 3^ minutes as the longest time in which to concentrate their 

 observations, and it is therefore not surprising that so much anxiety 

 was shown amongst scientific men of all countries to make the most 

 of this grand opportunity. 



No single astronomical event has ever before excited such 



* 'Phil. Mag.; August, 1860. 



E 2 



