48 WALKS AND TALKS. 



disappeared, under the encroachments of the growing marsh. 

 These are geological changes, and the geologist's eye looks 

 about for the causes. It is not a far-fetched solution to see in 

 the hillside wash a source of silt, which annually diminishes 

 the depth of water to a certain extent. And it requires but 

 ordinary sagacity to notice each decaying crop of grasses, 

 sedges, and rushes as the source of the dark peaty deposit 

 which displaces the last water, when other causes have pro- 

 duced the requisite shallowuess. We have caught the marsh- 

 making business in the midst of its accomplishment. Short 

 as our lives are, each life falls within the geologic age in which 

 vast results are actually working out. All these marshes have 

 been lakes. If we dig in them we find the bleached relics of 

 the very shells which held animated tenants of the vanished 

 lakelet. Thus, gathering sediments add sheet after sheet to 

 the deposits which are filling the larger as well as the smaller 

 bodies of water which rest on the earth's surface. 



All great rivers are enormous mud-carriers. The Nile, the 

 Amazons, the Ganges, the Hoaug Ho, the Mississippi, are 

 great vehicles for the transport of earthy substances from the 

 higher to the lower levels. Like the Tiber, their waters are 

 all "yellow." The Chinese have surpassed all other nations 

 in making a proper name of the generic description of muddy 

 rivers. What a potion is a glass of Mississippi water, placed, 

 by the side of one's plate in the cabin of the steamer! In 

 thirty minutes it holds a deposit of impalpable sediment, which 

 is simply mud. Think of the entire breadth and depth of 

 this mighty stream charged with earthy materials to such an 

 extent. What must be the total amount of matter carried 

 down to the Gulf annually ? The engineers of the United 

 States have attempted to answer this question. They say that 

 if the annual discharge of mud were brought together and 

 dried, it would form a block a mile square and two hundred 

 and seventy-eight feet high. Imagine that block lying on the 

 surface of some level township. Then think another block 

 on the top the result of another year's transport. Recall the 

 fact that the Mississippi has been at this business at least five 



