A CENTURY OF GEOLOGY. 



437 



accordance with the known geological history of the earth. If so, 

 then the oceanic hasins have always been oceanic hasins, and the 

 places of the continents have always been substantially the same. 

 This introduces a subject on which there has been much discussion 

 recently — viz. : 



The Permanency of Ocean Basins. — Closely associated with the 

 Lyellian uniformitarianism was the doctrine of extreme instability 

 of earth features, especially the forms and places of sea and land. 

 Crust movements were irregularly oscillating to such a degree that 

 in the course of geologic history sea and land frequently and com- 

 pletely changed places. Abundant evidence of this was supposed 

 to be found in the unconformities so frequent in the stratified 

 series. The tendency of that time was toward a belief in up-and- 

 down movements, back-and-forth changes, without discoverable, 

 law, rather than progressive onward movement. On first thought 

 it might seem that such lawless movement was rather in keeping 

 with catastrophism than uniformitarianism. But not so, for the 

 movements are supposed to be very slow. Again, it might seem 

 on first thought that gradual progressive change — in a word, evo- 

 lution — would be peculiarly in accord with uniformitarian ideas. 

 But again not so, because this doctrine was, above all, a revulsion 

 from the idea of supernatural purpose or design or goal contained 

 in catastrophism. Uniformitarianism strongly inclined toward 

 purposelessness, because of its supposed identity with naturalism. 

 Thus for a long time, and still with many geologists, the tendency 

 is toward a belief in irregular movements without discoverable 

 law, toward instability of even the greatest features of the earth — 

 viz., sea basins and continental arches. Geology for them is a 

 chronicle, not a life history. 



The contrary movement of thought may be said to have com- 

 menced with Dana. Dana studied the earth as a unit, as in some 

 sense an organism developing by forces within itself. The history 

 of the earth is a life history moving progressively toward its com- 

 pletion. The forces originating oceanic basins and continental 

 arches still continue to deepen the former and enlarge the latter. 

 From this point of view, oceanic basins and continental arches must 

 have always been substantially in the same places. Oscillations 

 there have been at all times and in all places, but they affect mainly 

 the outlines of these great features, though sometimes affecting 

 also the interior of continents and mid-sea bottoms, but not suffi- 

 ciently to change greatly their general form, much less to inter- 

 change their places. 



Such is the doctrine of permanency of oceanic basins. It is 

 undoubtedly a true doctrine, but must not be held in the rigid 



