ADDRESS SECTION A, B.A. 1876. 267 



with equal depression in the other two quarters, 

 amounting at greatest to 10 centimetres, and 

 graduating regularly from the points of maximum 

 elevation to the points of maximum depression in 

 the middles of the four quarters, would shift the 

 earth's axis of maximum moment of inertia 

 through i" on the north side towards the meridian 

 of 90 W. longitude, and on the south side towards 

 the meridian of 90 E. longitude. If such a 

 change were to take place suddenly, the earth's 

 instantaneous axis would experience a sudden 

 shifting of but T5 ^/ (which we may neglect), and 

 then, relatively to the earth, would commence 

 travelling, in a period of 306 days, round the 

 fresh axis of maximum moment of inertia. The 

 sea would be set into vibration, one ocean up 

 and another down through a few centimetres, like 

 water in a bath set aswing. The period of these 

 vibrations would be from 12 to 24 hours, or at 

 most a day or two ; their subsidence would prob- 

 ably be so rapid that after at most a few months 

 they would become insensible. Then a regular 

 3o6-days period tide of 1 1 centimetres from 



