THE POSITION OF THE EARTH^S AXIS. 117 



weight will be most increased is the Pacific Ocean ; that is 

 to say, the area of greatest removal is antipodal to the area 

 of increase, which is in the warm region, where we know the 

 growth is the most rapid — in fact, is just the coral-area, 

 where the researches of Darwin and Dana have acquainted 

 every one with the steady growth of the coral reefs in the 

 area, which is, or was recently, subsiding. The special con- 

 ditions of this area are rendering it the one in which the 

 greatest weight is the most readily added. If we divide 

 the earth into a land- and water-hemisphere, with England 

 as a centre, the gain of the weight of the water-hemisphere 

 is about 4300 million tons. 



It must be self-evident to any one that a sufficient weight 

 added (locally) between the equator and the poles can alter 

 the position of the earth. This is as evident as that a 

 weight will draw down the pan of a balance ; and the 

 question remains. How much is sufficient to do this in an 

 appreciable way ? 



Newton, in his ' Principia' *, says : — Let there be added 

 anywhere between the pole and the equator a heap of new 

 matter like a momitain, and this, by its perpetual endea- 

 vour to recede from the centre of its motion, will disturb 

 the motion of the globe, and cause its poles to wander 

 about its superficies, describing circles about themselves 

 and their opposite points. 



The amount of change that can be effected depends upon 

 the proportion of added matter (localized to one spot for 

 calculation) to the mass of the equatorial bulge ; and this 

 we find clearly put forward in a paper by Sir G. B. Airy f 

 to refute the theory that a change could have been caused 

 by the elevation of mountain-masses, showing how great 

 they must have been, as a weight one thousandth part of 



* Newton's ' Principia,' translated by Motte, 1848, New York. 

 t ' Athen^uin,' Sept. 22, i860. 



