EVOLUTION OF THE EARTH'S FEATURES. 747 



and oceanic basins have influenced the general direction of the action 

 of lateral pressure, the cleavage structure, or the existence of direc- 

 tions of weakest cohesion, appears to have in part controlled the 

 courses of fractures and uplifts, somewhat as the warp and woof in a 

 piece of cloth fix the courses of rents, while the direction of the force 

 applied determines the positions and extent of the rents. Force ex- 

 erted at right angles to the lines of structure, and equal along the 

 line, would produce a straight series of rents or uplifts (Figs. 11, 12, 

 p. 19). If not equal along a given line, the series of rents made, 

 taken together, might be oblique or else curving (Figs. 13, 14, 15). 

 If the tension were oblique to the structure-courses, the series of rents 

 would be an oblique series, and, as above, either straight or curved. 

 Hence, curves are necessarily in the system. 



We observe now that the North Atlantic follows one of the cleav- 

 age-courses, and the Pacific another (page 85). North America is 

 bounded by the two, and hence its triangular form. The coincidence 

 between the trend of the Pacific (northwest and southeast), the mean 

 trend of the Pacific islands (p. 33), and the axis of the coral-island 

 subsidence (p. 583), shows that the ocean in its movements has been 

 one great area of oscillation. The central curving range, five thousand 

 five hundred miles long, lies on the southern side of the axis of this 

 great approximately-elliptical area. 



The double or triple system of curves around Australia, from New 

 Hebrides, or perhaps northern New Zealand, to New Guinea and 

 Timor, are such as might arise from pressure acting against that stable 

 continental area of Australia ; for they are concentric with it ; and 

 the branch of the central Pacific chain, leading off westward through 

 the Carolines, has been shown, on page 34, to conform to this Aus- 

 tralian system. The rising curve from Java, through Sumatra, sug- 

 gests that here pressure acts from the direction of the Indian Ocean 

 as well as the Pacific ; and this is further confirmed by the fact that 

 the deep-water channel, separating the Australian seas from the Asi- 

 atic, passes just north of New Guinea and Celebes, and south of Java. 



The East Indian Archipelago lies between the North Pacific and 

 the Indian Ocean ; and the two, along with the reacting stable conti- 

 nental areas, have together modelled out the group. The West Indian 

 Archipelago has a similar position between the North Atlantic and 

 the South Pacific, and hence the resemblances to the East Indian, 

 pointed out on pages 35, 36. 



The curves along eastern Asia, in the islands and continental moun- 

 tain-ranges (page 35), seem to show that the pressure from the direc- 

 tion of the Pacific, which produced the curves, was unequal along dif- 

 ferent parallel lines. The courses and positions of the groups of 



