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By A. T. Metcalfe, F.G.S. 



F the numerous agencies which modify the surface of 

 the globe, probably the most universal, unceasing, and 

 remarkable in its effects is Water. To it, in its varied 

 forms of action, are largely due not only vast changes in the 

 distribution of sea and land, but also minor diversities of hill, 

 valley, and plain. Our estimate, however, of the magnitude of 

 its operations will be altogether inadequate if regulated by what 

 we witness in our own country. Changes take place, indeed, in 

 Britain, but only the more observant can perceive their extent and 

 importance. Every shower of rain that falls tends to loosen the 

 cohesion of rocks and soils on which it falls : raindrops coalesce to 

 form rills that carry with them loose particles of sand and mud 

 which lie in their paths; rills give their burdens of sediment to 

 the runnels, the runnels to the brooks, the brooks to the rivers, 

 and the rivers to the ocean. Observe the muddy state of a river 

 after heavy rain ; obtain a gallon of the water and allow it to 

 settle. The quantity of sediment will be found to be consider- 

 able. Could this quantity be multiplied by the number of such 

 gallons rolled down by all the rivers in the country in a year, and 

 then again in a century, one would arrive at some faint idea of the 

 vast amount of solid matter worn from the land by water and 

 deposited in the sea. 



It is to regions nearer the equator, however, that we must look 



