120 



THE BALANCE. 





not coincide, for in that case the equilibrium would 

 become unstable. 



The heavier the beam, the greater is the work done 

 in raising its centre of gravity; and the greater, there- 

 fore, the weight required for producing a given deflec- 

 tion. The beam must, therefore, be as light as possible. 

 At the same time it is obviously necessary that the 

 beam should be stiff enough to support the weights 

 without bending, and since hollow pieces are stronger 

 in proportion to their weight than solid pieces, in the 

 best balances the beam consists of an open frame of 

 brass or steel. 



If two beams have equal weights and equal distances 

 between their centres of gravity and points of suspension, 

 but are of unequal length, as in fig. 88, A and B, the 



FIG. 88. 



same work is required in both in order to produce a 

 deflection through a given angle, say of 20. But this 

 work will be done by a smaller weight at the end of the 



