ANNIVERSARY ADDRESS OF THE PRESIDENT. IxXXV 



biites to a change in the earth's axis of rotation arising from astro- 

 nomical causes, and describes the results which would follow from 

 such conditions. As to the possibility of a change in the earth's 

 axis of rotation, we had a paper from Sir John Lubbock, in which he 

 first adverts to the revolution of a solid body on its principal axis, 

 and its continuing to do so for ever, unless such solid body be acted 

 upon by some extraneous force. He further observes that on this 

 supposition no change of climate would obtain on any given latitude 

 on the earth's surface except from a change in internal temperature 

 or the heat of the sun. 



He then notices that a change of climate alone is not sufficient to 

 account for geological changes, such as water covering a part of the 

 earth's surface at one time and not at another : and remarks that the 

 moon's attraction and the causes which produce the precession of the 

 equinoxes do not modify these conclusions. 



Sir John Lubbock then states, that "it is unlikely that when 

 the earth was first set spinning, the axis of rotation should exactly 

 coincide with the axis of figure, unless indeed it were all perfectly 

 fluid." He subsequently takes a period not so remote, when the earth, 

 from the different fusibility of its component parts, might have been 

 partly solid in irregular masses and partly fluid, and afterwards a still 

 more advanced state, in which land and water irregularly occurred on 

 its surface, suited to the existence of animal life, always supposing 

 the axis of rotation not to coincide with the axis of figure. If any 

 resistance exists, '* the pole of the axis of rotation would describe a 

 spiral round the axis of figure, until finally it would become, as at 

 present, identical with it." Supposing a displacement of the axis, the 

 movement of the water from one equator to another and the conse- 

 quent changes of climate are pointed out. Glancing at friction on 

 the surface of the earth rendering the invariability of geographical 

 latitude, otherwise existing, not a necessary consequence, at our igno- 

 rance of the earth's structure beneath its crust, and of the history of 

 the changes eifected during the process of cooling, Sir John considers 

 that "the utmost that can be accomplished by mathematics is to 

 explain under what hypothesis a change of the position of the axis of 

 rotation is possible or not." Adverting to the dictum of Laplace, 

 that the changes on the earth's surface and in the relative positions 

 of land and water cannot be accounted for by a change in the posi- 

 tionof the axis of rotation, he observes that in this statement Laplace 

 did not take into consideration either (1) the dislocation of the strata 

 by cooling, or (2) the friction of the surface. Finally, our colleague, 

 after admitting that if at any remote period the earth had been a ho- 

 mogeneous spheroid of any pure metal in a state of fusion, it would 

 in cooling always revolve about the principal axis of rotation, that of 

 figure, considers that there is sufficient evidence of want of homoge- 

 neity on the earth's surface to bring a change of axis of rotation within 

 the limits of possibility. 



It is always gratifying to find mathematicians so far interested in 

 our science as to occupy themselves with the solution of problems, 

 which, when we consider their important bearing, scarcely seem to 



