136 ON THE ACTION OF WATER 



Wind blowing from places where a greater degree of 

 evaporation takes place is one of the most unquestionable 

 precursors of rain. This is the case with winds blowing 

 from the sea ; thus the west wind comes loaded with va- 

 por from the Atlantic Ocean, which it deposits on the 

 continent of Europe. 



Emily. But why does the south wind bring us rain ; 

 we may consider that as coming from the dry heated 

 continent of Africa, for the Mediterranean Sea is too in- 

 significant to impregnate it with vapor ? 



Mrs. B. The climate of Africa being considerably 

 hotter than that of Europe, a greater evaporation takes 

 place there ; the atmosphere dissolves and contains much 

 more water than our colder regions are capable of hold- 

 ing in solution ; the air, therefore, as it advances north- 

 ward, becomes loaded with a precipitation of vapor, which 

 congregates into clouds, and falls to the earth in the form 

 of rain. 



Caroline. That is very curious ; and a north wind, on 

 the contrary, being able to maintain more vapor in solu- 

 tion in our climate, than it did in the colder countries 

 whence it blows, scarcely ever brings us rain. I have 

 heard that swallows flying low, flies stinging, fowls rolling 

 themselves in the dust, and cattle feeding voraciously, 

 are all signs of approaching rain ; pray, are these merely 

 rustic prejudices, or will they admit of an explanation ? 



Mrs. B. Swallows fly low before rain to catch the in- 

 sects, which then come nearer to the earth for shelter ; 

 they may, also, approach the earth in search of worms, 

 which make their appearance above ground in times of 

 rain ; then a species of fly, with an indurated trunk capa- 

 ble of inflicting a wound, frequently makes its appearance 

 on the approach of wet weather ; the fowls may possibly 

 cover themselves with dust in order to preserve them 

 from the wet ; and cattle may, instinctively, lay in a store 

 of food as a provision against the time they must abandon 

 their pasture to seek shelter from the rain ; but I do not 

 pretend to advance these opinions as any thing more than 

 conjecture founded on some appearance of plausibility. 



758. What is one of the surest precursors of rain, and when does it 

 occur'? 759. -What does Mrs. B. say of the rains in England occa- 

 sioned by south winds'? 760. What does Caroline say of a north wind, 

 and what does she say, she has heard mentioned as signs of approaching 

 rain 1 ? 761. What does Mrs. B. say of these signs! 



