SCHOOL COURSES. 



47 



III. Earthy or Mineral Constituents : 



(a) An inquiry as to the origin and some changes under- 

 gone : 



Experimental study of Denudation : 



Enumerate first the commoner agents forming soil 

 Rain, Frost, Eunning Water, Wind, Vegetation, Animals. 



Explanation of mode of action of these. 



Examine the extent of weathering on old buildings and 

 tombstones, the dates of which are known. 



Note crumbling of stone walls and growth of moss and 

 lichen on these. 



Note also the farmer's operations, Ploughing, etc., 

 seeking the assistance of Nature in the work of further 

 disintegration. 



Fig. 3. River-Loops in an Alluvial Valley. The dots mark points 

 of deposition. 



An Illustration : The Work of Running Water : 



Some things to be done and observed are : Examine 

 streams swollen after rain, take samples in a glass vessel, 

 note the muddy condition, set aside and j-ecord the time 

 taken for the water to become (relatively) clear. Note 

 the different layers of sediment, and their times of settling. 



Estimate the rate of flow of the stream. This may be 

 done roughly by timing floating objects in, say, the middle 

 of the stream, covering a distance measured from the 

 bank. By this means discover how far the different layers 



