302 



Mr. Muggins on Solar Prominences. 



[Feb. 18, 



was entirely absent, because the fact of its becoming inclosed in crystals 

 depends so much on their nature. At the same time the occurrence of 

 fluid-cavities containing what seems to be merely liquid carbonic acid is 

 scarcely reconcilable with the presence of more than a very little water 

 in either a liquid or gaseous form. We may here say that we do not agree 

 with those authors who maintain that the curved or irregular form of the 

 fluid-cavities is proof of the minerals having been in a soft state, since ana- 

 logous facts are seen in the case of crystals deposited from solution. 



EXPLANATION OF PLATE VII. 



Figs 1. & 2. Fluid-cavities in sapphire ; magnified 20 linear. 



Fig. 3. Fluid-cavity in sapphire, partially divided by plates of sapphire ; mag. 50. 



Fig. 4. Branched fluid-cavity in sapphire ; mag. 50. 



Fig. 5. Crystal of spinel ? inclosed in ruby ; mag. 50. 



Fig. 6. Cavity in aquamarina, with two fluids ; mag. 150. 



Fig. 7. Cavity in ruby spinel ; mag. 100. 



Fig. 8. Fluid-cavity in emerald, with soluble crystals ; mag. 200. 



Fig, 9. Crystal inclosed in diamond, surrounded by a black cross, as seen with pola- 

 rized Hgkt ; mag. 100. 



Fig. 10. Crystal inclosed in diamond, with a crack proceeding from it ; mag. 100. 



Fig. 11. Crystal inclosed in ruby, surrounded by a black cross, seen by polarized light ; 

 mag. 75. 



Figs. 12 & 13. Crystals in ruby spinel, surrounded by various cracks ; mag. 50. 



II. " Note on a Method of viewing the Solar Prominences without 

 an Eclipse/'' By William Huggins, F.R.8. Received February 

 16, 1869. 



Last Saturday, February 13, 1 succeeded in seeing a solar prominence so 

 as to distinguish its form. A spectroscope was used ; a narrow slit was 

 inserted after the train of prisms before the object-glass of the little tele- 

 scope. This slit limited the light entering the telescope to that of the 

 refrangibility of the part of the spectrum immediately about the bright line 

 coincident with C. 



The slit of the spectroscope was then widened sufficiently to admit 

 the form of the prominence to be seen. The spectrum then became so 

 impure that the prominence could not be distinguished. 



A great part of the light of the refrangibilities removed far from that of 

 C was then absorbed by a piece of deep ruby glass. The prominence was 

 then distinctly perceived, something of this form. 



