GULLIVER. — SHORELINE TOPOGRAPHY. 



199 



Tlie lagoon between the three or four individuals of Santa Maria island, Chile, 

 is completely converted into marsh (H. O., 1209). 



Alki point, Washington (C. S., 651 ; G. S., Seattle). This point may never have 

 been separated from the mainland. 



The northern portion of Unalashka island from cape Kalekhta to Constantine 

 bay, Alaska, has been tied by two bars to the main island. The enclosed lagoon 

 is a long narrow one, extending the whole distance between the bars. The map 

 indicates considerable filling on the sides of the lagoon (C. S., 821). 



Massoncello point, Italy, upon the southern end of which Piombino is situated, 

 is an example where the enclosed lagoon has been completely aggraded by a river 

 delta, that of the Cornia Eiver (Ital., 119, 127). 



VI. Vanishing Island (Adolescence). — After an island has become 

 land-tied, it continues to waste away by the action of the sea and subaerial 

 forces, until a stage is reached when the island is gone and nothing but 

 the tombolo which connected it to the mainland remains. This stage 

 must of necessity be a short one, for the unconsolidated tombolo will be 

 rapidly consumed. This feature would be one of late adolescence. 

 Theoretically we should expect to find single, Y, cuspate, and double 

 tombolos remaining after the islands had been 

 consumed. The three examples which appear 

 to be surely in this stage are all cuspate. 

 This form is probably the one which best re- 

 sists the sea, and each of the others is easily 

 converted into the cuspate. 



Cuspate Tomholo: Block island, Figure 17. — The 

 type cusp whose position has been determined by a 

 former island is Sandy point. Block island (C. S., 

 356).* 



At the southern end of Revere beach (C. S., 337; 

 G. S., Boston Bay, Mass.) there is a cuspate projec- 

 tion where a drumlin was formerly tied on and has 

 now been consumed. 



Uvita point on the western coast of Costa Rica 

 (H. O., 1035) is a cuspate foreland whose position is 

 apparently determined by rocky islets off the point. 

 This seems to be a case where the cusp is completely 

 tying the island when the island itself is practically 

 destroyed. 



Figure 17. Vanishing Isl- 

 and ; Diagram of a Cus- 

 pate Tombolo. Similar 

 Stage found in Sand}' 

 Point, Block Island, 

 Rhode Island. 



VII. Straight Coos^ (Maturity). — The mature stage of island-tying is 

 where the islands and their connecting tombolos are completely consumed 



* See Livermore's History of Block Island, 1877, 175. 



