SHEPHERD] PHYSICAL AXD CHEMICAL 331 



balance without the pans ; neither is it neeessary for the pans to 

 be of equal weight, nor do the suspending threads need to be of the 

 same length. It is necessary, however, for the arms and the at- 

 tached pans to balance each other. 



Weights mav be made from zinc, tin. sheet lead or heavy 

 cardboard. A rectangular piece of either could be weighed on a 

 druggist's or grocer's balance, and then cut into desirable sizes ; or 

 weights may be made by putting dry, fairly coarse sand, or small 

 shot into little bags, the bags and contents constituting the 

 weights. 



These balances are not as sensitive as those to be found in 

 high school and other laboratories, and neither are the weights 

 as accurate. The children can make balances and weights, how- 

 ever, of sufficient accuracy to satisfy their needs, but this state- 

 ment does not mean that they should put together a makeshift 

 affair in which they have no confidence. On the contrary, they 

 should make the best balance of which they are capable, and this 

 best is good enough. 



Xeedless to say. there should be some motive other than the 

 construction of the balance, if one wishes the best effort of which 

 the children are capable. That is to say, even before the balances 

 have been planned the children should have some use to which 

 they wish to put them. For instance, it is easy to conceive in con- 

 nection with physiplog}' that children might be interested in de- 

 termining approximately the amount of water in food stuffs, for 

 example, in apples, carrots, turnips or potatoes. The firmness 

 with which such motive holds the children, together with the 

 pleasure they get from making things, will determine very largely 

 lx)th the value of the work and the general appearance of the 

 balances. 



In addition to the work with the balances in connection with 

 the water in food stuffs, the children would be interested in and 

 profit by other studies with the lever. Already they will have 

 found that equal weights operating at equal distances from the 

 fulcrum counter-balance each other. For example, the bodv that 

 weighs one ounce is balanced by a weight of one ounce. The 

 balance is one application of the law. ''the weight x weight arm 

 equals the power x power arm." 



A further study of the same law may be made by the chil- 

 dren through experimentation, with but a slight modification of 

 their balances. As a result of such experimentation the children 

 would be able to understand much in the mechanical world which 

 they do not understand; moreover, therebv thev will be enabled 



