156 nature's /liMracles. 



caused by the water, through the force of 

 gravity, seeking the lowest level, and avoid- 

 ing obstructions, which they can flow around 

 more easily than remove. 



Great rivers often change their courses, espe- 

 cially where they flow through a region of 

 made earth, such as is the case with the lower 

 Mississippi River, and in other great rivers of 

 the world. The loose earth is continually 

 shifted by the current, and where the current 

 is not very strong it will often hold the water 

 back to such an extent of accumulated weight 

 that the flood will break over at some weak 

 point on its banks and make a new course for 

 itself. 



One of the great rivers of China the 

 Hwangho often causes dire destruction to 

 life and property owing to change in its bed 

 from time to time. It is estimated that be- 

 tween the years of 1851-66 this river caused 

 the loss of from 30,000,000 to 40,000,000 lives 

 through drowning and famine by the destruc- 

 tion of crops. 



Floods in rivers are occasioned from vari- 

 ous causes. Of course the primary cause is 

 the same in all cases, that is, from precipita- 

 tion of moisture in the form of rain or snow. 

 Some rivers are so related to the area of rain- 

 fall and to the permeability of the soil that 

 there is but little variation in the amount of 

 discharge throughout the year. The great 



