THE SKY 145 



ness requisite to produce this color, were broken into bits 

 and scattered in the air, Newton inferred that the tiny 

 fragments would display the blue color. Tantamount to 

 this, he considered, was the action of minute water-parti- 

 cles in the incipient stage of their condensation from aque- 

 ous vapor. Such particles suspended in our atmosphere 

 ought, he supposed, to generate the serenest skies. New- 

 ton does not appear to have bestowed much thought upon 

 this subject; for to produce the particular blue which he 

 regarded as sky-blue, thin plates with parallel surfaces 

 would be required. The notion that cloud-particles are 

 hollow spheres, or vesicles, is prevalent on the Continent, 

 but it never made any way among the scientific men of 

 England. De Saussure thought that he had actually seen 

 the cloud- vesicles, and Faraday, as I learned from himself, 

 believed that he had once confirmed the observation of the 

 illustrious Alpine traveller. During my long acquaintance 

 with the atmosphere of the Alps I have often sought for 

 these aqueous bladders, but have never been able to find 

 them. Clausius once published a profound essay on the 

 colors of the sky. The assumption of small water drops, 

 he proved, would lead to optical consequences entirely 

 at variance with facts. For a time, therefore, he closed 

 with the idea of vesicles, and endeavored to deduce from 

 them the blue of the firmament and the morning and 

 evening red. 



It is not, however, necessary to invoke the blue of the 

 first order to explain the color of the sky; nor is it neces- 

 sary to impose upon condensing vapor the difficult, if not 

 impossible, task of forming bladders, when it passes into 

 the liquid condition. Let us examine the subject. Eau~ 



de- Cologne is prepared by dissolving aromatic gums or res- 



SCIENCE V 7 



