20 TRANSACTIONS OF THE [oCT. 14, 



ranged, and a reverse process would set in. It is interesting to 

 observe that in the case of a mountain system like the Appa- 

 lachians (hesperoclinal), — so conspicuously formed through long 

 periods by a lateral pressure from the southeast, — the struc- 

 ture is precisely such as would result from a repeated or long- 

 continued reduction in the eastward velocity of the earth^s 

 rotation. These points are referred to, partly to show how 

 complicated may be the actions and interactions of forces in- 

 volved, and partly as indicating a method by which it may be 

 possible to determine whether the earth's axial motion has been 

 gaining or losing in rate through the geological ages. 



(III.) Of course, as already noted, the differences of velocity 

 vary greatly according to distance from the equator, — the velo- 

 cities themselves having the ratio nearly of the cosines of the 

 latitude-angles. It follows, therefore, that any such action as 

 that here suggested, depending upon the differential velocities, 

 must vary correspondingly, both in direction and amount. The 

 effects should be greater, and the courses more east-and-west, 

 as we pass from the equator poleward. The fact that the earli- 

 est areas of elevation are so largely found in the higher northern 

 latitudes, is of interest, and perhaps of importance, in this view. 

 According to the theory, it is in the high latitudes of both hemi- 

 spheres that the action should be most observable; and as we 

 pass from the poles toward the equator, it should be more ob- 

 scured, complicated, or replaced by later and secondary processes. 

 The far southern regions are of course practically inaccessible 

 under their mantle of sea and ice, and only the northern areas 

 are at all open to study. 



(IV.) If the careful and extended collection and comparison 

 of facts should be found to establish the views of this paper, 

 another important question may thereby be helped toward a 

 solution. I refer to the permanence of direction of the earth's 

 axis, whether by this is meant its absolute direction in space or 

 its relative direction to the surface of the globe. Any disturb- 

 ance or variation, especially of the latter, must result in great 

 disarrangement of the horizontal strains, and express itself in 

 new systems of stress and displacement, which would indicate 

 both its direction and its amount. 



I have been able here only to touch upon this extensive sub- 

 ject, and to suggest some of the results that may flow from its 

 fuller prosecution. The theory is presented, however, though 

 in brief and imperfect form, as a matter for reflection, observa- 

 tion, and inquiry. 



The paper was illustrated with diagrams of faults, crevasses, 

 and diagonal trends on the globe. 



