WATERY VAPOUR IN THE HEAVENLY BLUE. 113 



as its absorbing medium acts also as an elastic cushion, 

 which is able to carry it along, notwithstanding its 

 enormous bulk and weight (of which no words of ours 

 could convey an adequate idea) as though it were no 

 heavier than a film of spider's web. The winds there- 

 fore supply the place which the " firmament " was 

 supposed to represent in the minds of the ancients. 



The intelligent traveller, when he goes forth from 

 our cloud-laden atmosphere to bask in the glorious 

 sunshine and balmy breezes of a southern climate, may 

 therefore constantly bear this in mind, that though 

 the sky may appear spotless in its exceeding trans- 

 parence and serenity, and is unflecked, it may be, by 

 a single cloud, vast accumulations of water, such as 

 we have here striven, in a very humble way, to give 

 some idea of, are nevertheless perpetually floating 

 overhead, throughout the whole expanse of the heavenly 

 blue: unheard, unseen, unfelt, and even unsuspected, 

 by the dwellers upon the earth beneath. Indeed, it 

 seems probable that the azure blue of the sky itself 

 is simply the effect of the solar rays transmitted to 

 us through these immense masses of aqueous vapour. 

 Water itself, even in its most crystal purity, being o 

 a blue colour (ultra-marine) but this colouring only 

 becoming apparent, when viewed through the medium 

 of masses of considerable volume. 



Now, these enormous volumes of water are being 

 at all times gradually exhaled from the terrestrial 

 surface of the land, as well as from the entire liquid 

 expanse of the ocean, as vapour, so subtle in its 

 nature that in general it passes away in totally in- 

 visible form, so that it is only on rare occasions that 

 the action of this mighty process is revealed to our eyes. 



VOL. I. 8 



