Wave-lengths of the Lines of the Solar Spectrum. 257 



It is conceivably possible* that a coreless ring-vortex, with 

 irrotational circulation round its hollow, shall be left oscillating 

 in the neighbourhood of the equator of the globe ; provided 

 (|Y 2 — P)/P be not too great. If the material of the globe 



be viscously elastic, the vortex settles to a steady position round 

 the equator, in a shape perfectly symmetrical on the two sides 

 of the equatorial plane; and the whole motion goes on steadily 

 henceforth for ever. 



If (fV 2 — -P)/P exceed a certain limit, I suppose coreless 

 vortices will be successively formed and shed off behind the 

 globe in its motion through the fluid. 



XXIX. On the Relative Wave-lengths of the Lines of the Solar 

 Spectrum. By Prof. Henky A. Rowland f. 



EOP several years past I have been engaged in making a 

 photographic map of the solar spectrum to replace the 

 ordinary engraved maps, and I have now finished the map 

 from the extreme ultra-violet, wave-length 3200, down to 



* If this conceivable possibility be impossible for a globe, it is certainly 

 possible for some cases of prolate figures of revolution. 

 f Communicated by the Author. 



Phil. Mag. S. 5. Vol. 23. No. 142. March 1887. T 



