166 PROCEEDINGS OP THE AMERICAN ACADEMY, 



following elevation or depression, for as will be shown later the forms in 

 the various stages are quite different, as far at least as into maturity. 

 After maturity is reached in the development of forms of the coast and 

 shore, the distinction between a cycle following uplift and one following 

 depression is not so marked. 



Slow and rapid Movemsnt. — The initial criteria for the ideal case have 

 heen given as if the land were raised at once to a certain height and then 

 stopped, and as if its form were exactly as it had been when developed 

 at a lower level. Such a conception is of course admissible in an ideal 

 scheme, but in the consideration of actual examples the sea will gener- 

 ally be found to have done some work while the movement was in pro- 

 gress. A series of halts may be made in the upward movement, as has 

 been shown in San Clemente (Figure 4). Any speed of uplift may be 

 found in a given locality, and the above criteria must be modified to fit 

 the case under consideration. 



Beffioncd and Continental Uplift. — From the uplift of a limited area 

 we may extend the conception to a whole continent, but we must be 

 careful that the criteria are found throughout the whole of the area in 

 which the uplift is inferred. If a whole continent was uplifted bodily, 

 the new shoreline, the coastal plain, and the elevated former shoreline 

 should be found all round its margin, unless some local reason could be 

 given for the absence of one or more of these criteria in a given locality. 



Continental movements have been inferred from local phenomena, par- 

 ticularly by writers who have discussed the relations between elevation 

 and glaciation, so that the term as found in the literature is used in a 

 very loose way. 



3. Uniform Depression. 



Initial Stage of an Ideal Area. — As in the case of uniform uplift an 

 ideal case will be first considered in the study of the initial forms follow- 

 ing uniform depression. Tiie ideal case is taken of a region of homo- 

 geneous structure, which was developed to early maturity in the previous 

 cycle, and the depression was sufficient to entirely submerge all the forms 

 of the coast and shore developed in the previous cycle. The depression 

 is regarded as having been continuous, though not necessarily rapid. 

 The sea action upon the land during the slow depression was not suf- 

 ficient in such a short space of time to materially change the mature 

 forms of the previous cycle. 



(1) Utteven Bottom. — If a region be submerged for a certain amount 

 beneath the sea, the vertical distance being the same on all sides, the 



