Curiosities of Science. 155 



fore, in a certain ratio to the diameter of the drops ; hence 

 thunder and other showers in which the drops are large pour 

 down faster than a drizzling rain. A drop of the 25th part of 

 an inch, in falling through the air, would, when it had arrived 

 at its uniform velocity, only acquire a celerity of 1 1^ feet per 

 second ; while one of of an inch would equal a velocity of 

 33 feet. Leslie. 



RAINLESS DISTRICTS. 



In several parts of the world there is no rain at all. In the 

 Old World there are two districts of this kind : the desert of 

 Sahara in Africa, and in Asia part of Arabia, Syria, and Per- 

 sia; the other district lies between north latitude 30 and 50, 

 and between 75 and 118 of east longitude, including Thibet, 

 Gobiar Shama, and Mongolia. In the New World the rain- 

 less districts are of much less magnitude, occupying two narrow 

 strips on the shores of Peru and Bolivia, and on the coast of 

 Mexico and Guatemala, with a small district between Trinidad 

 and Panama on the coast of Venezuela. 



ALL THE RAIN IN THE WORLD. 



The Pacific Ocean and the Indian Ocean may be considered 

 as one sheet of water covering an area quite equal in extent to 

 one half of that embraced by the whole surface of the earth ; 

 and the total annual fall of rain on the earth's surface is 186,240 

 cubic imperial miles. Not less than three-fourths of the vapour 

 which makes this rain comes from this waste of waters ; but, 

 supposing that only half of this quantity, that is 93,120 cubic 

 miles of rain, falls upon this sea, and that that much at least 

 is taken up from it again as vapour, this would give 255 cubic 

 miles as the quantity of water which is daily lifted up and 

 poured back again into this expanse. It is taken up at one 

 place, and rained down at another; and in this process, there- 

 fore, we have agencies for multitudes of partial and conflicting 

 currents, all, in their set strength, apparently as uncertain as 

 the winds. 



The better to appreciate the operation of such agencies in 

 producing currents in the sea, imagine a district of 255 square 

 miles to be set apart in the midst of the Pacific Ocean as the 

 scene of operations for one day ; then conceive a machine cap- 

 able of pumping up in the twenty-four hours all the water to 

 the depth of one n'ile in this district. The machine must not 

 only pump up and bear off this immense quantity of water, but 

 it must dischnrgp it again into the sea on the same day, but 

 at some other place. 



All i he great rivers of America, Europe, and Asia are lifted 



