FORM. 



obviously assume a form departing from that of an exact sphere. 

 The parts near the eqiiator would extend themselves to a greater 

 distance from the axis, those more remote from the equator to a 

 less distance, and so on, until, at the pole, the matter would not 

 he at all affected by the rotation. This would be the case if the 

 globe were formed of matter in a liquid or even in a semi-liquid 

 or soft state, or if its materials were elastic. 



The form it would take would be one resembling an orange or a 

 turnip. Thus, if N s, fig. 3, be its axis, the equatorial diameter, 

 q q, will be stretched out to the increased length, Q Q, while the 

 parts between q q and the poles will be less and less extended the 

 nearer they are to the poles, 3 



The globe would therefore be 

 changed from the form N q s q. 

 of a true sphere, to the form 

 M" Q, s Q, of a flattened globe, 

 called in geometry an OBLATE 

 SPHEROID. 



31. The elliptic form would 

 depart more and more from a 

 true circle as the motion of 

 rotation is more rapid, so that 



between the time of rotation and the degree of ellipticity there is a 

 fixed relation, such that when the time of rotation is given, the 

 oval form, or what is the same, the proportion of the equatorial 

 to the polar diameter, can be computed. 



32. It is certain, then, that if the earth were composed of fluid, 

 soft or elastic matter, it could not continue to retain the form of a 

 globe, but would become a spheroid, having that degree of ellip- 

 ticity which would correspond to a motion of rotation, at the rate 

 of one revolution per day, and it is shown by calculation that this 

 ellipticity would be such that the equatorial diameter would be 

 greater than the polar diameter by one three-hundredth part. 



33. But the earth, in its present state, is not composed of such 

 yielding materials, and it becomes a question, what, in that case, 

 must be the effect of the diurnal rotation on the distribution of land 

 and water, if the earth were an exact globe. 



34. The solid parts of the earth would resist by their cohesion the 

 tendency of the rotation, to cause them to be accumulated and 

 heaped up around the equator ; but this would not be the case 

 with the waters composing the seas and oceans. These, by reason 

 of their freedom and mobility would yield to the centrifugal force, 

 and would heap themselves up around the equator, flowing in that 

 direction from the polar regions of either hemisphere, so that the 

 necessary consequences of the earth having a form exactly 



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