THE TKEES OF AMERICA. 49 



Experiment third. The result of a series of experiments with the ther- 

 mometer is as one to seven, nearly ; that is, the temperature of the room being 

 above eighty degrees, the mercury rose from thirty-two to eighty degrees in one 

 seventh of the time when an artificial current of air was kept up by means of 

 a fan, which of course could be of but little force, as when the instrument, 

 placed in the same position as in the first case, was allowed to remain undis- 

 turbed. As a further illustration of the rapidity with which thawing is pro- 

 duced by the unobstructed blowing of a warm wind, a gentleman informs us 

 he has found, by actual experiment, that ice will waste more in one or two 

 hours under this condition than during a whole day of sunshine when it is 

 entirely sheltered from the wind. From this we may perceive how freshets 

 may be produced by the action of the wind, and also the only means we have 

 in our power to guard against their production. And it is satisfactory to 

 remember that the Creator has placed it within the ability of every one to aid 

 in this, as the humblest individual can plant a tree. 



The causes which produce freshets, as also the freshets themselves, produce 

 droughts. The unobstructed blowing of the wind, especially if it be warm and 

 dry, is, as is well known, the most rapid possible method of producing evap- 

 oration, and is, perhaps, the main cause of drought. During the blowing of 

 the simoon of Africa, evaporation goes on so fast at the surface of the body 

 as to dry the skin, and cause it to crack. The throat becomes inflamed, the 

 respiration is accelerated, and extreme thirst and fever are the results. The 

 water contained in the skins, which are the water casks of travellers, evap- 

 orates, and leaves them a prey to the most terrible sufierings. A traveller at 

 Palermo speaks of his first experience of the sirocco — the hot wind of the 

 Mediterranean : " The first blast of it on my face felt like the burning steam 

 from the mouth of an oven. On another side of the house, not exposed to the 

 wind, I found the heat much more supportable. Such are the drying effects of 

 this wind, that the leaves of the trees become so parched that they can be 

 rubbed into dust. Even household furniture cracks, and in many instances 

 flies to pieces." From the above statement it will . be seen how the mere bar- 

 rier of a building produced a sensible modification of the wind. 



