R I V 



one string to the other during- the time of observation ; and this by the 

 rule of three may be adapted to any other portion of .time. This opera- 

 tion may often be greatly abridged by noticing the arrival of the float- 

 ing- body opposite to two stations on the shore, especially when it is not 

 convenient to stretch a string across. Where a time piece is not at hand 

 the observer may easily construct a quarter second or other pendulum. 



RIVERS, proportional lengths of, and supposed quantity of ivater dis- 

 charged per annum. ( Ency. Brit. Suppl.) 



EUROPE 



ASIA 



AFRICA 





To deduce the approximate lengths of the rivers in miles from the pro. 

 portiorial lengths we may multiply the latter by 180. To convert the 

 proportional discharge into known measures we may multiply by 1800 



to pbtain the number of cubic feet per second, or by .4 or j^to find the an. 

 nual discharge in cubic miles. 

 249 



