,S44 president's address, 



movements of tlie A'iscous interior, more or less independent of 

 that of the crust 1 



Some of the peculiarities of the distribution of temperatui-e in 

 the Tertiary seem to be more easily explained on the assumption 

 of a geographical shifting of the pole, and as a slow shifting 

 seems to be going on at the present moment, it ma}' be looked 

 upon as helping to solve the difficulty. 



Mr. Marr says in his Address previously referred to that Dr. 

 Neumayr in his work (Ueber Klimatische Zonen wiihrend der 

 Jura und Kreidezeit) has, in the opinion of many geologists,, 

 established the existence of climatic zones in former times. This 

 may be the best way of testing any supposed extensive shifting 

 of the pole, although it is to be observed that up till the late 

 Tertiary actual polar conditions must have been confined to a 

 very few degrees round the pole, and may be, therefore, diffi<'ult 

 to identify. 



With regard to the possible geographical shifting of the axis, 

 it has seemed to me that somewhat extensive changes could have 

 taken place in former times when the earth was less rigid and 

 the interior more closely resembling a fluid, in the following 

 manner. We believe that the rotation of the earth is being slowly 

 but surely retarded by the action of the tides. If the interior 

 were fluid or thinly viscous, the retardation of the crust would 

 not immediately affect the interior, as it would take time to 

 communicate the retardation — that is to say, the interior would 

 always rotate at a slightly greater speed than the crust. Now 

 the solid crust would not be smooth underneath ; if corrugations 

 form exteriorily, through cooling or other causes, the under side 

 would be roughened too. If the fluid or viscous interior were not 

 absolutely homogeneous, and it is not likely ever to have been so, 

 it would contain masses of solid matter, or of matter of at least 

 firmer consistence than the rest. These floating masses on the 

 under side of the crust would come in contact with the ridges, and 

 would tend to produce^ away from the equator — an acceleration 

 at that spot which would cause the rotation of the whole to be 

 modified and the axis shifted. 



