SUBJECT MATTER AND METHODS 169 



given number of rows, of a given number of units in a 

 row." 



The relation of the volumes of the pyramid, prism, cone, 

 and cylinder to one another is shown by experimenting 

 with tin measures. The pupils see by experiments that the 

 cylinder and prism hold respectively three times as much 

 water as do the cone and the pyramid. Hence the rule for 

 finding their volumes. The volume of the sphere, from a 

 model divided into pyramids, is seen to be the aggregation 

 of the volumes of a number of pyramids. The relation of 

 the great circle to the surface of a sphere is shown by wrap- 

 ping the flat and the convex surfaces of a hemisphere with 

 a string. The pupils see that twice as much string is re- 

 quired in the latter as in the former case; hence, the rule. 

 It is found by experiment with a string that the circum- 

 ference of a circle is about 3^ times the diameter. It is 

 convenient to have the class learn the formulas: D X 

 3.1416 = C; and D 2 X .7854 = ^. 



Considerable attention is given to drawing to scale plans 

 of rooms, yards, and gardens, then finding the areas. A 

 great deal of time is required for this kind of work, as much 

 as a week having been spent on our school yard alone. 



