Shaler.] 110 [February 1, 



On the Causes which have led to the Production op Cape 

 Hatteras. By Prop. N. S. Shaler. 



It is an almost self-evident proposition that the geological structure 

 of a coast line is the key to its character; that the subterranean fea- 

 tures have determined its outward contours. It is equally clear that 

 the changes now going on along any coast must depend to a great 

 extent upon the geological" character of the materials along that 

 coast. These considerations make it seem necessary to study the 

 geological disposition of the materials along any shore, as the condi- 

 tion on which we may hope to attain to a true understanding of the 

 causes which have determined its form. In endeavoring to arrange 

 a plan for the examination of the geological history of the shore line 

 of the United States, it is at once obvious that the first thing to be 

 done is to interpret the history of the most conspicuous features of 

 the shore, in order to obtain the basis for the detail work. Inspec- 

 tion of the map of the eastern coast of North America shows the 

 existence of a number of great indentations and projections. It is 

 obvious that these must depend upon some great geological facts 

 which require interpretation. I propose to discuss here the causes 

 which have led to the production of one of the most important irreg- 

 ularities, the great salient angle of our southern shore known as Cape 

 Hatteras. The geological facts already in our possession have 

 failed to account for the existence of this projection. The general 

 character of the shore at that point, and of the low lands which lie 

 between the sea and the base of the Alleghany mountains, is such as 

 to make it seem at first sight unlikely that the shoulder which the 

 continent forms at this point is to be referred to disturbances of the 

 underlying rocks. The region, for nearly one hundred miles to the 

 west of Cape Hatteras, is nearly level, and seems to be a northward 

 prolongation of the great southern plain which extends from Texas 

 to Virginia ; a singularly monotonous surface, with little indication of 

 disturbance away from the immediate contact with the borders of 

 the Alleghany chain. Along the whole stretch of coast from near 

 the mouth of the Rio Grande we find the shore line everywhere bor- 

 dered by this plain, and throughout its whole extent presenting no 

 features which require us to call in the aid of geological dislocations 

 to explain, saving the projections at the mouth of the Mississippi 

 and the peninsula of Florida. The shore, from Matagorda Bay to 

 near Hatteras, forms an almost uniformly curved line. The consider- 



