The Plan of the Earth and its Causes. — Gregory. 107 
ranges parallel with the equator, and the other ranges from 
pole to pole." Prof. Lapworth contends that the intersecting 
of two simultaneous orthogonal sets of undulations' explains 
FIG. 2. — THE OBLIQUE COURSE OF THE MAIN GEOGRAPHICAL 
LINES, (after PRINZ.) 
the forms and dispositions of the continents, the triangular 
shapes of their extremities, the diagonal trend 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 de- 
pression should coincide with the steep slopes that separate the 
ocean floors and the continental platforms ; and why the exist- 
ing shore lines should so often run diagonally between the me- 
ridians and parallels. 
This theory, and that of Sir John Lubbock, which also at- 
tributes the continental forms to a double intercrossing series 
of folds, have the ad vantage, over the astronomical theories of 
more detailed agreement with geographical facts ; but Prof. 
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. 
