Give an instance of limestone formation from such solutions.
How do rivers furnish sediment for the stratified rocks?
What determines the position of rapids in rivers?
What is the effect of waterfalls on the abrading action of rivers?
What is the peculiarity of rock at Niagara which has prevented the fall from becoming a succession of rapids?
What other circumstance increases the abrading action of rivers?
What is the principal source of the sediment which is transported by rivers?
What is the annual amount of sediment furnished by the Kennebec? The Merrimac? The Mississippi? The Ganges?
What is the general tendency of these abrading forces?