72 PHYSICAL GEOGRAPHY OF THE SEA, 
calm. Hoar-frost is nothing but congeaied dew, and owes its 
formation to the same causes. 
When warmer air-currents are cooled by being transported 
into colder regions, or from any other refrigerating cause, a great 
part of their moisture generally condenses into small vesicles, 
but very little heavier than the surrounding atmosphere, 
which then becomes visible under the form of clouds, thosa 
great beautifiers of our changing skies, that frequently trace 
such picturesque, gorgeous, or singular groups and landscapes 
in the aérial regions. The inhabitants of countries where the 
heavens are monotonously serene, may well envy us the charms 
of a phenomenon which in some measure affords us compensa- 
tion for so many disagreeable vicissitudes of the weather. Who 
that has admired at sunset the light clouds so beautifully fringed 
with silver and gold, or glowing with the richest purple, and 
loves to foliow them in all their wonderful and fantastic trans- 
formations, will deny that they are the poesy and life of the skies, 
the awakeners of pleasing fancies and delightful reveries ? 
Thin wreaths of clouds have been observed, by travellers that 
have ascended the most elevated mountains, floating high above 
the peak of Chimborazo or Dhawalagiri, and thus shows us to 
what an amazing altitude the emanations of ocean are carried 
by the ascending air-current. 
Sometimes when light clouds pass into a warmer atmosphere, 
they gradually dissolve and vanish; more frequently the accu- 
mulating moisture, tov heavy to continue floating in the air, or 
condensed by electrical explosions, descends upon the earth in 
rain, which, with few exceptions, visits every part of the globe, 
either in its liquid form or congealed to snow or hail. But the 
quantity of rain which annually falls in different regions is very 
unequal, and strange to say, it is not most considerable in those 
countries whose climate enjoys an unenviable notoriety for its 
clouded atmosphere and the great number of its rainy days. 
In the tropical regions it is generally only about the time of the 
summer solstice that abundant showers of rain fall regularly every 
afternoon, while the rest of the year, the sky is uninterruptedly 
serene; but during the short period of the rainy season, a far 
greater quantity of water is precipitated upon the earth, than 
in the temperate zones. 
While on the island of Guadaloupe, the annual quantity of 
