3 ? 2 (58) 



in. And whether the actual sky be capable of this amount 

 of condensation or not, I entertain no doubt that a sky 

 quite as vast as ours, and as good in appearance, could 

 be formed from a quantity of matter which might be 

 held in the hollow of the hand. 



Small in mass, the vastness in point of number of the 

 particles of our sky may be inferred from the continuity 

 of its light. It is not in broken patches nor at scattered 

 points that the heavenly azure is revealed. To the ob- 

 server on the summit of Mont Blanc the blue is as uni- 

 form and coherent as if it formed the surface of the most 

 close-grained solid. A marble dome would not exhibit 

 a stricter continuity. And Mr. Glaisher will inform you 

 that if our hypothetical shell were lifted to twice the 

 hight of Mont Blanc above the earth's surface, we 

 should still have the azure overhead. Everywhere 

 through the atmosphere those sky particles are strewn. 

 They fill the Alpine valleys, spreading like a delicate 

 gauze in front of the slopes of pine. They sometimes 

 so swathe the peaks with light as to abolish their defini- 

 tion. This year I have seen the Weisshorn thus dis- 

 solved in opalescent air. 



By proper instruments the glare thrown from the sky 

 particles against the retina may be quenched, and then 

 the mountain which it obliterated starts into sudden 

 definition. Its extinction in front of a dark mountain 

 resembles exactly the withdrawal of a veil. It is the 

 light then taking possession of the eye, and not the 

 particles acting as opaque bodies, that interfere with the 

 definition. 



By day this light quenches the stars ; even by moon- 

 light it is able to exclude from vision all stars between 

 the fifth and the eleventh magnitude. It may be likened 



