368 THE FLAN OF THE EARTH AND ITS CAUSES. 



This map is interesting, for these primitive torsion wrinkles must 

 have been formed in the same period as Professor Darwin's primitive 

 tidal wrinkles. It is significant that the lines do not correspond. The 

 chief geographical lines which Darwin claims as his primitive wrinkles 

 are inexplicable on Prinz's theory, and the great lines which Prinz 

 claims to support his wrinkling are opposed to those of Darwin. The 

 geographical primitive lines of the two theories are often contradictory. 



A third theory assigning the geographical distribution to very 

 ancient causes has been proposed by Professor Lap worth. In an 

 address to the geographical section of the British Association in 1892, 

 and in a brilliant lecture on "The face of the earth," delivered to the 

 Royal Geographical Society in 1894, Lapworth attributed the arrange- 

 ment of oceans and continents to an intercrossing series of primitive 

 earth folds. The oceans, according to this theory, occupy ancient basins 

 of depression ; and the continental masses are domes of elevation. 



"The surface of the earth crust at the present day," .says Lapworth, 

 "is most simply regarded as the surface of a continuous sheet which 

 has been warped up by two sets of undulations crossing each other at 

 right angles * * * The one set ranges parallel with the equator, 

 and the other ranges from pole to pole." Professor Lapworth contends 

 that the intersecting of two simultaneous orthogonal sets of undulations 

 explains the forms and dispositions of the continents, the triangular 

 shapes of their extremities, the diagonal trends of their shores, and 

 the course of the linear archipelagoes. In some interesting diagrams 

 he suggests why the intersecting nodal lines which mark the divisions 

 between the areas of elevation and of depression should coincide with 

 the steep slopes that separate the ocean floors and the continental 

 platforms; and why the existing shore lines should so often run 

 diagonally between the meridians and parallels. 



This theory, and that of Sir John Lubbock, which also attributes the 

 continental forms to a double intercrossing series of folds, have the 

 advantage over the astronomical theories of more detailed agreement 

 with geographical facts; but Professor Lapworth has not, so far as I 

 am aware, explained what caused his intersecting folds. His theory is 

 accordingly less complete than the others, as it is rather a statement 

 of facts than an explanation of causes. 



These suggestive theories are open to one objection which seems fatal 

 to their application to the existing geographical plan. We should 

 expect from them that the main geographical structure lines in the 

 northern and southern hemispheres should be either symmetrically 

 arranged or continuous on both sides of the equator. But that the land 

 systems of the two hemispheres are asymmetrical is the most glaring 

 factin geography. It may be urged that the primitive folding, wrinkling, 

 and torsion formed a symmetrical or continuous land system, and that 

 the asymmetrical arrangement is due to later movements. In that case 

 the theories are geographically inadequate, because they give no expla- 

 nation of how the existing geographical asymmetry was developed. 



