Teacher's Leaflet. 740 



Lesson VI. 



sedimentation. 



Purpose. — To observe how and where and why the brook drops its 

 load. 



Experiment. — Take a glass fruit jar nearly full of water from the 

 brook, add gravel and small stones from the bed of the brook, sand from 

 its borders and mud from its quiet pools. Have it brought into the 

 schoolroom aifd shake it thoroughly. Then place in the window and 

 ask the pupils to observe the following things : 



(a) Does the mud begin to settle while the water is in motion, that 

 is, while it is being shaken? 



(b) As soon as it is quiet does the settling process begin? 



(c) Which settles first, the pebbles, the sand or the mud? Which 

 settles on top, that is, settles last? 



(d) As long as the water is in the least roily it means that the soil 

 in it has not all settled, and if disturbed even a little it becomes roily 

 again, which means that as soon as the water is in motion it takes up its 

 load. 



Observations. — (i). Where is the current swiftest, in the middle or 

 at the side of a stream? 



(2). What is the difference in the bottom of the brook between the 

 place below the swift current and the sides? That is, if you were 

 wading in the brook, where would it be more comfortable for your feet, 

 at the sides or in the swiftest part of the current, and why? 



(3). Does the brook have a more stony bed where it flows down a 

 hillside than when flowing through a level place? 



(4). Place a dam across your brook at a place where the bottom is 

 stony and note how soon it will have a soft muddy bottom. 



(5). Find a still pool in your brook that has not a soft, muddy bottom 

 if you can. 



(6). Does the brook flow more swiftly in the steep places and narrow 

 places or in the wide portions and dams. 



(7). Do you think if water flowing swiftly and carrying a load of 

 mud were to come to a wider or more level place, like a pool or dam, 

 that it would drop some of its load? 



(8). If the water flows less swiftly along the edges of the stream 

 than in the middle, would this make the bottom below here softer and 

 more comfortable to the feet than where the current is swiftest? If 

 so, why? 



