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Be v. S. Haughton on Physical Geology. [June 20, 



My paper, of 20th December, consisted of two parts : — 1st. A dis- 

 cussion of the rate at which a "wabble " of the earth's axis of rotation, 

 caused by a want of coincidence between the axis of figure and the 

 axis of rotation, would be destroyed by the friction of the ocean 

 against its bed. 2nd. Speculative inferences from the solution of this 

 problem, as to the duration of geological periods, depending on hypo- 

 thetical geological assumptions as to the method in which Europasia 

 was manufactured. 



These assumptions were three in number, and none of them very 

 probable, viz. : — 



(a.) An instantaneous formation of the continent ; 



(&.) Its formation by means of 69 equal convulsions, with an interval 

 of time between each, sufficient to reduce the radius of the wabble 

 from one mile to five feet ; 



(c.) Its formation, by a number of small shocks, each displacing the 

 axis of figure by such an amount that tidal friction would be able to 

 render the axes of figure and rotation again coincident in the period 

 of a single wabble. 



In discussing the two latter hypotheses, I naturally timed my shocks 

 so as to produce the maximum wabble. For this assumption I have, of 

 course, no authority ; and I readily admit that any conclusions drawn 

 from the earth's wabble can have no more value than the probability 

 of the hypothesis we may make as to the method of formation of 

 Europasia. 



In general, let AOB, fig. 1, be a portion of the path described by 

 the axis of the figure, let AO be the displacement produced by any 

 single shock, arid let APBQ be the circle described by the axis of 

 rotation in the first wabble after the occurrence of the shock. 









\ 



. 









— 



If the next shock which moves the axis of figure from O to B 

 occurs when the axis of rotation is at A, the wabble will be doubled, 

 and have the radius AB ; but if the second shock be so timed as to 



