1907.] 



AND MOUNTAIN FORMATION. 



393 



211, 307 and 232, that is to say, during the period when the change in direc- 

 tion of motion has been comparatively rapid, the relief of seismic strain has 

 not only been marked, but it has been localized along the junctions of ^nd 

 blocks and land plains where we should expect to find that the effect of 

 general disturbances was at a maximum. It can hardly be assumed that the 



(£30 



+0.20 ♦ojo 0:00 -CLIO ~<s.zo -0:36 



" Fig. 2. This is similar to Fig. i, but refers to the year 1903, during 

 •ich period the pole displacement was more uniform than that indicated 

 ^ ig. I." 



frequency under consideration is directly connected with change in direction 

 of pole movement ; but it seems not unlikely that both effects may arise from 

 the same redistribution of surface material by ocean currents and meteorolog- 

 ical causes generally." 



This reasoning of Milne asserts that the greatest earthquakes 

 occur when the path of the pole bends most rapidly. In reply to 

 this claim we may remark in the first place that it is very doubtful 

 whether a general law of this kind can be fairly deduced from ex- 

 isting observations, because the path of the pole depends on such 

 minute quantities that the curvatures platted may not be real. In the 

 second place, if the assumed law were admitted, the meaning of 

 it would still be open to interpretation, and several of these could 

 no doubt be m.ade without involving a contradiction of known laws. 



For the total displacement of the pole from the mean position 

 is nearly always less thari 30 feet, and generally less than 15 feet; 



PROC. AMER. PHIL. SOC, XLVI. 187 AA, PRINTED MARCH 5, I908. 



