406 



F. P. GULLIVER — CUSPATE FORELANDS. 



/ 



probably changing, and tlie down-current curve is reall}^ made up of two 

 curves, and the up-current curve offsets the down-current one in each 

 case. Typical examples of overlap occur as follows : Perdido bay, Florida 

 (C. S., 187); Corpus Christi pass, Texas (C. S., 210); Townsends and 

 Corsons inlets (New Jersey atlas, 17), and Fire Island inlet, Long island 

 (C. S., 119). 



The overlap is an intermediate form between the offset and the deflected 

 stream. A graded series of examples might be given from simple offset 

 through various coml)inations of overlap to a case of 

 stream deflection without any offset. 



Along coasts which are formed of unconsolidated 

 materials it is frequently observed that rivers, brooks, 

 or tidal channels aim toward the sea for a certain dis- 

 tance and then turn and run along nearlv parallel to 

 the shoreline and finally em})ty to the right or the left 

 of the point which would have been their direct course 

 to the sea. The river's intention to reacli the sea as 

 quickly as possible is evidently not carried out where 

 such deflection is seen. Some disturbing force has 

 come in. There seems little doubt that this force is the 

 current alongshore which has turned the outlet of the 

 stream. Such has been the explanation of many 

 authors.* Figure 3 shows the relation of current to 

 deflection of streams. 



The materials of which the foreland is constructed come from the main- 

 land and the bottom on the up-current side, while on the down-current 

 side they must be carried inshore from the point of the cusp or else built 

 up from the bottom. This carrying back of sands from the point toward 

 the mainland would frequently cause a hooked spit to form on the end 

 of the cusp ; therefore in this class cf cusps a hook may be exjiected. 

 Off the tip of the cusp irregular shifting shoals should occur, from which 

 projections, like underwater spits, might be expected to extend in the 

 direction in which the current flows along the edge of the shoal. Since 

 these currents on either side of the cuspate foreland would be out of gear 

 with each other, there would be set up between them small whirls of 

 water which would tend to change the form of the shoals frequently. 



TYPE. 



With this deductive scheme in mind, let us turn to the maps of these 

 capes (C. S., 11, 142, 145, 146, 147, 149, 150, 420, 421, 424, 425) and see 



Figure T^.—Slreatn 

 Deflections. 



* De la Beche: Geol. Notes, 1830, vol. il, p. 11, pi. 1, figure 3; Reclus: La Terre, 1870, vol. i, p. 147; 

 Sir A. Geikie : Text-book, 3d ed., p. 399. 



