22 Journal of the Mitchell Society [September 



of its crust, producing the movements of subsidence, elevation, and 

 sudden jarring, which take ]ilace along the border-line between land 

 and sea. Indeed, there is an everlasting see-saw between the land and 

 sea taking place along the shoreline, and this profoundly affects all 

 harbors. This is especially noticeable on both sides of the North- 

 Pacific, and the changes on our Pacific coast — especially in Alaska — • 

 and in Japan, in a single generation, have been so marked as to force 

 us to believe that the uniformitarians have overaccentuated the slow 

 movement, through all time, of the forces now in operation. The 

 modern geologist is forced to recognize that there have been changes — 

 sometimes gradual and sometimes sudden — in the intensity and mode 

 of action of existing forces. And these changes seem more and 

 more marked as wider areas of the earth's crust have come under 

 the scrutiny of the geologist, during the century that has not yet 

 elapsed since Sir Charles Lyell made his epoch-marking generaliza- 

 tion; but that does not mean that the geologist of today is in any 

 sense swinging to the conclusions of the catastrophist. These forces 

 bringing about elevation and subsidence are covered by the term 

 diastrojjhism. 



Vulcanism is another of the igneous agencies for the application 

 of terrestrial energy, whose work as a harbor-maker, of little im- 

 portance in the past, is destined to play an important part in the 

 immediate future. Since our own nation has learned that the way 

 to national power is over the waves, and our hope is that the con- 

 quests of the future will be of a commercial sort, harbors of refuge 

 and naval harbors are now seen in a new light, as aids to commerce 

 without which the commercial harbor can never grow into a great 

 port. Harborage of such a sort is afforded in numerous instances 

 where the rim of a volcanic crater has broken down in one or more 

 places, and the whole submerged to such an extent that the central 

 cavity forms excellent harborage, often of great strategic importance. 

 Harbors of this kind are known in nearly all seas; but they have 

 hitherto been dismissed with the statement that they have no other 

 than a scientific interest, if indeed they are mentioned at all in any 

 discussion of the subject. Fortunately, our own country owns sev- 

 eral such harbors in different parts of the Pacific. These and coral- 

 reef harbors, which are to be considered in some detail, afford excel- 

 lent naval harbors and coaling stations, not only in the Pacific and 



