THE TIDES 177 



of the steel will cause the hoop to spring back into its 

 original shape. Again, you might accomplish this dis- 

 tension of the hoop in other ways, as, by setting a heavy 

 weight upon its rim while it stood in an upright position, 

 or by stretching it with your hands, or by compressing it 

 in a vise. And yet again, if the hoop were very large, or 

 relatively very thin, or composed of some softer material, 

 as lead, its own weight would tend to flatten it. In short, 

 there are more ways than one of deforming a hoop, and 

 there is certainly a better way of accounting for the 

 earth's oblateness than by calling upon the energy of her 

 rotation; for which, both as to its origin and recupera- 

 tion, Newtonians confess their inability to account. They 

 resemble the thriftless wife who could not be made to 

 comprehend why her credit at the bank had run out, when 

 there was the check-book to prove she still had a plenty 

 of blanks in reserve. Drafts on the Bank of Imagination 

 are never returneed N. S. F., and Newtonians have cer- 

 tainly not been chary of availing themselves of its un- 

 limited resources. 



To ascertain just how much energy is required to dis- 

 tend our hoop to any given degree of elongation, all that 

 is necesssary is to hang it on the hook of a balance scale, 

 lend your weight to the hoop until the desired elongation 

 is obtained, and then read the scale. To effect this 

 elongation ~by cranking requires power a steady flow of 

 power or energy exactly equal to the elastic strength of 

 the steel, as previously ascertained on the scale, or, what 

 is the same thing, to the sustaining against gravity of a 

 weight of that same magnitude. It not only required a 

 great expenditure of energy on the part of the earth's 

 momentum to whirl the excess water to the equator in the 

 first instance, but it takes a steady supply of power to 

 keep it there. 



Again. Suppose that the hoop instead of being made 

 of spring-steel were made of some material that would 

 not give while rotating, but continue to retain its original 

 circular shape, what then? Which operation, think you, 

 will require the greater expenditure of power; to rotate 



