C Lloyd Morgan — Phymgraphy. 245 



tlie sea a mass of solid matter equal to that borne down by tlie 

 Ganges in the four months of flood season." All the matter 

 carried down in this way is built up, layer upon layer, into a yast 

 delta deposit, or strewn over the bed of the ocean. Of such layers 

 much of the crust of the earth, the sand and clay at the top of the 

 cliff behind us for example, is composed. 



But besides the matter carried down by rivers in suspension, a 

 vast amount is carried down in solution. Take the Thames for 

 example. For every grain transported mechanically, more than 

 20 grains are carried down chemically. Every gallon contains some 

 20 grains of lime salts, and about two grains of common table salt, 

 or Chloride of Sodium. These also are carried out into the sea, in 

 which the Chloride of Sodium, along with certain other salts, 

 accumulates on the evaporation of the water, and thus forms the 

 brine of the ocean, while the Carbonate of Calcium is separated by 

 living creatures and built up into some sort of pure limestone. Of 

 such limestones also much of the crust of the earth, the chalk of the 

 cliff behind us for example, is composed. 



We have thus seen what the streamlet is doing. It is aiding the 

 rivers of the world to carve out valleys, and it is carrying seawards the 

 fine mud and sand which result from its own work and that of rain, 

 to contribute to the framework of a future continent. And how 

 comes it here ? Directly or indirectly from rainfall. Whether its 

 source be a spring, or the collected waters from a sloping hill-side, it 

 •matters not. Without rainfall, such as is now pouring from the 

 distant storm-cloud, the streamlet could have had no existence. 



Another question therefore suggests itself : What is this rainfall 

 doing, and how comes it here ? If we walk along the shore for a 

 little distance, we may perhaps see (if there is beneath the cliffs any 

 clayey material containing flat stones) small pillars of earth, each 

 capped by one of these flat stones. These are little monuments of 

 rain action. Eain falls upon the surface and runs off towards lower 

 levels ; as it runs, however, it carries with it a little of the fine 

 clayey material. Thus it lowers the surface. But where there is a 

 flat stone, the surface is protected from the softening action of rain- 

 drops, just as a house is protected by its roof. The soil beneath the 

 stone is not carried away, and the miniature earth pillar stands out as 

 a monument. In Switzerland there are, in several places, earth 

 pillars 50 or 60 feet high, which have been formed in this way. 



But it is not only where there are earth pillars that the rain is 

 exercising a denuding action upon the land. If we go out into the 

 fields on any rainy day, we may watch how the soil is literally 

 flowing downwards to the sea. Few fields are perfectly flat, and 

 the rain which falls upon the surface tends to drain off at the lowest 

 possible level. But if we examine the water which is thus on" its 

 way down the field, we shall at once see that it is not clear, that it 

 carries with it some of the soil. Much of the rain, of course, sinks 

 into the ground. But before it does so it is nearly sure to trickle a 

 foot or two over the surface. Even if it only runs a few inches, it 

 must bear with it some of the soil for this distance, and there leave 



