I 1 4 VISIBLE EVAPORATION. 



Nevertheless there are times when evaporation 

 assumes palpable shape. Upon a winter's day in our 

 own country, for instance, when a bright sun streams 

 out after a night of severe frost, people walking in 

 their gardens, or near soil that has been recently 

 turned, may often see steam, rising in smoke-like 

 wreaths fr*om the surface of the ground. Occasionally 

 to such an extent does this become visible, that it 

 looks as if it was actually on fire. Go over, and put 

 your hand into the steam, and the humid warmth, 

 given off by the earth, can frequently be clearly felt! 



Now, what is this but evaporation in visible form? 

 such as is at all times going on around us, though 

 we cannot see it. So again, when crossing the equa- 

 torial calms, in a ship at sea, when a shower of cold 

 rain has recently fallen, the surface of the ocean may 

 be seen to smoke, in an exactly similar way. We 

 have seen this phenomenon very beautifully exhibited 

 off the African coast, in the gulf of Guinea, during 

 the great heats which prevail there. 



The cause of this remarkable spectacle, in both the 

 cases we have cited, is identical ; namely, the invisible 

 vapour, at the moment that it is given off and first 

 mixes with the atmosphere, becomes partially condensed 

 by cold, and so at once assumes a visible form: in the 

 first case, through contact with the frosty air, the 

 immediate surface of the soil having been warmed by 

 the bright sunshine ; and in the second, by the chilling 

 effect of the cold rain falling upon the heated surface 

 of the glassy sea. 



Such in brief is an outline of Nature's great design 

 of the water-bearing winds and the uplifting of aqueous 

 vapour to create the rains; grand and majestic, both 



