302 Mr. B. Stewart on the Red Protubwances which are 



can hardly yet be said to be completely effected. The step which 

 I claim to have taken in this direction in the discovery of a third 

 hydrodynamical equation, and the results which have been 

 obtained by the combination of this equation with the other 

 two, deserve, I think, the attention of mathematicians. If any 

 objections should be made to either the principles or the reasoning 

 which I have advanced, I shall be ready to take them into con- 

 sideration j if any explanations should be asked for, I hope to be 

 able to give them. The subject is one that cannot possibly be 

 ignored if progress in theoretical physics be of any moment. 

 The importance in that respect of the foregoing hydrodynamical 

 theory of vibrations is evinced by the facility with which it at 

 once accounts for the more obvious phenomena of light. This 

 application of it I reserve for another communication, the present 

 one having already extended to a great length. 

 Cambridge, September 13, 1862. 



XL. On the Nature of those Red Protuberances which are seen 

 on the Sun's Limb during a Total Eclipse. By B. Stewart, 

 M.A., F.R.S. 



To the Editors of the Philosophical Magazine and Journal, 



Gentlemen, 



WILL you permit me to make a few observations on those 

 very remarkable protuberances which are seen to sur- 

 round the sun's disk during the time of his total eclipse ? and if 

 I am tempted to indulge in speculation, the rare occurrence of 

 the phenomenon, and the interest attaching to it, may perhaps 

 be viewed as an apology. 



These strange and startling appearances have now been ob- 

 served at least three times. The first of these occasions was 

 during the total eclipse of the 7th of July, 1842, when their 

 existence was revealed by the late Mr. Baily and the Astronomer 

 Royal. The account of these philosophers was sufficient to 

 rouse the attention of astronomers ; so that during the next total 

 eclipse, which happened on July 28th, 1851, there was assem- 

 bled a large body of skilful and accurate observers well qualified 

 to make the most of the few but precious minutes of darkness 

 allotted them, in order if possible to elucidate the nature of these 

 striking appearances. 



From the observations of Mr. Airy and others, it was rendered 

 very probable that the red protuberances really belonged to the 

 sun, while, from their vast magnitude, the idea of their being 

 solar mountains was at once discarded. 



It seemed rather to be the impression among those assembled 

 on this occasion, that they were connected in some way with 



