DOUBLE STARS 151 



moderate speed. Let us now imagine a steady twist l to 

 be applied to it. It will rotate faster and faster, and it 

 will in consequence become more and more flattened. It 

 is, however, now known that this process will not continue 

 indefinitely. A stage will be reached at which the 

 spheroid will have the greatest flattening that is practic- 



Axis of rotation. 



FIG. 6. Critical form of Maclaurin's spheroid 



ally possible. Its euqatorial diameter is now 1-7 times 

 its polar axis, and its form is shown in fig 6. Upon con- 

 tinuing the twist, the form of the mass ceases to be 

 spheroidal. It is true that spheroids with a greater 

 flattening are conceivable as figures of equilibrium, but 

 beyond this point they are in an unstable condition. Like 



1 The term * twist ', in its meaning as adopted in scientific language, is 

 not used accurately here, but it will convey a more definite impression to 

 the general reader than the more scientifically accurate expression. 



