1878.J Mr. G. H. Darwin on Geological Time. 179 



[viz., the equation (1 - u 8 )(l— v s ) - (1— «») 8 =-0is n s + v 8 — @ = 0], and 

 the modular equation as obtained by the elimination from the two 

 quadric equations in fact presents itself in the form 



March 14, 1878. 



Sir JOSEPH HOOKER, K.C.S.I., President, in the Chair. 



The Presents received were laid on the table and thanks ordered for 

 them. 



The following Papers were read : — 



I. "On Professor Hanghton's Estimate of Geological Time." 

 By George H. Darwin, M.A., Fellow of Trinity College, 

 Cambridge. Communicated by J. W. L. GLAISHER, M.A., 

 F.R.S. Received February 19, 1878. 



In a paper recently read before the Royal Society,* Professor 

 Haughton has endeavoured by an ingenious line of argument to give an 

 estimate of the time which may have elapsed in the geological history 

 of the earth. The results attained by him are, if generally accepted, 

 of the very greatest interest to geologists, and on that account his 

 method merits a rigorous examination. The object, therefore, of the 

 present note is to criticise the applicability of his results to the case of. 

 the earth ; and I conceive that my principal criticism is either incor- 

 rect, and will meet its just fate of refutation, or else is destructive of 

 the estimate of geological time. 



Professor Haughton's argument may be summarised as follows : — 

 The impulsive elevation of a continent would produce a sudden dis- 

 placement of the earth's principal axis of greatest moment of inertia. 

 Immediately after the earthquake, the axis of rotation being no 

 longer coincident with the principal axis, will, according to dynamical 

 principles, begin describing a cone round the principal axis, and the 

 complete circle of the cone will be described in about 306 days. Now, 

 the ocean not being rigidly connected with the nucleus, a 306-day tide 

 will be established, which by its friction with the ocean bed will tend 



* "Notes on Physical Geology. No. III. On a New Method of finding 

 Limits to the Duration of certain Geological Periods." " Proc. Roy. Soc," vol. 

 xxvi, pp. 534—546 (December 20, 1877) . 



