GULLIVER. — SHORELINE TOPOGRAPHY. 173 



ceived, and largely filled in with examples, beginning with the area 

 uniformly uplifted and ending with a highly complicated mountainous 

 region. This interesting subject falls outside the province of this 

 paper. 



PART IL SEQUENTIAL FORMS. 



5. Sea Attack and Transportation. 



Differential Abrasion. — Varying hardness of rock is an important 

 factor in subaerial degradation, and it must also have considerable to do 

 with the attack of the sea upon coasts. The two ways of formation of 

 plains discordant with the rock structure have been contrasted thus : " A 

 subaerial baselevel plain is gradually completed by the action of ordinary 

 forces on all parts of its surface," while " a submarine platform is essen- 

 tially completed strip by strip, once for all, as far as it goes." * Pro- 

 fessor Shaler has recently called the monadnocks, the residual masses of 

 harder rock rising above the New England upland, " the most enduring 

 evidences of marine action." f 



Without entering into the discussion whether the New England 

 monadnocks were formed by subaerial or submarine denudation, it is the 

 purpose of the writer to use tliese contrasting interpretations of the same 

 phenomenon as an introduction to the discussion of the effect of relatively 

 hard and soft rock upon marine denudation. Waves will attack softer 

 rock more rapidly than its more resistant neighbor. A promontory of 

 hard rock may thus be formed where the less resistant rock on either 

 side has been eroded by the sea. The ocean, however, tends to convert 

 irregular to straight or gently swinging coasts. 



If the land therefore remains at the same level there will come a time 

 when the increased cutting upon the exposed promontory will equal the 

 lessened wearing of the softer material in the re-entrants on either side. 

 After such equilibrium is reached the shoreline will march inward, practi- 

 cally strip by strip. If, on the other hand, there is a gradual sinking of 

 the land, decided inequalities of surface due to differential marine erosion 

 may be covered by the offshore deposits. This has been pointed out 

 both by Professor Shaler and by Professor Davis in the papers quoted 

 above. 



Monadnocks versus Marine Remnants. — A distinction should be sought 



* Messrs. Davis and Wood, Proc. B. Soc. Nat. Hist., 1889, XXIV. 375. 

 t Bull. G. S. A., 1895, VI. 149. 



