422 



F. P. GULLIVER — CUSPATE FORELANDS. 



Figure \\ —Tombola Cusps. 



Upon the coast of Italy where island-tying in its various stages is beauti- 

 fulh'- shown such a bar is called a tonibolo. For convenience in distin- 

 guishing island-tying bars from those of other kinds, the writer proposes 

 to call ever\^ bar of this kind a tombolo, giving an English plural tombolos. 

 In the early stages of the groAvth of a tombolo a condition occurs similar 



to what is shown in figure 14, where 

 two cuspate points project toward 

 each other, the one from the island 

 and the other from the mainland. 

 Either cusp may occur without the 

 other, according to where transpor- 

 tation first begins. A case like the 

 figure is seen on Aebelo island in 

 Grand Belt strait (Denm.,Bogense). 

 Here the cusp points toward another cusp projecting from a smaller 

 island between Aebelo and the mainland. 



Another example is Spectacle island, in Boston harbor (C. S., 337), 

 where tlie " nose-piece " of the spectacles con- 

 sists of two cusps almost joined. 



From Tuno island (Denm.,Samso) there pro- 

 jects toward Samso island a lanceolate cusp 

 whose position indicates that it was formed by 

 in and out flowing tides or by two currents run- 

 ning: on either side of Tuno island toward the 

 larger land area. 



After an island has become land-tied b}' one 

 tombolo or by two inclosing a lagoon, which in 

 time is converted into marsh, it continues to be 

 consumed by the sea upon its outer side. There 

 will come a time when the island is almost or 

 quite gone (figure 15) and the tonil)olo construc- 

 tion will remain for a short time in a form like that of the cuspate forelands 

 described above. The northern point of Block island (C. S., 356) seems to 

 be of this origin. There is the following tradition of Sandy point. Block 

 island : " On the extremity of the point was anciently a peninsula called 

 the Hummuck. It was an elevation of land on which small trees and 

 bushes grew, and at low tide was reached on foot. The old inhabitants 

 now speak of having gathered wild plums there. It was washed away 

 long ago."* 



An example where the island is not so completely eroded but in which 

 the cuspate form is less typical is Colchester point in lake Champlain 

 (G. S., Plattsburg, N. Y.). 



Figure 15.— island Cusps. 



*S. T. Livermore; History of Block Island, 1877, p. 175. 



