294 Annals of the Carnegie Museum. 



prolongation, but ordinarily there occur at irregular intervals conflict- 

 ing currents due to northeast winds which carry the debris southward 

 and tend to form a recurved spit or hook. 



The most powerful agency, however, in the distribution of the 

 beach-debris after it has reached this part of the peninsula is to be 

 found in the surf of great northeast storms, which may pile the sand up 

 in the form of beach-bars or ridges above and beyond the reach of the 

 ordinary surf. In fact, it has been stated by Gilbert:'^ "The habit 

 of the shore, including not only the maximum height of the beach- 

 line and the height of its profile, but the dimensions of the wave-cut 

 terrace and of other wave products, is determined by and adjusted to 

 the great storms." '' 



The ridges and bars built up during the great northeastern storms 

 will, of course, have a general direction parallel to the waves produc- 

 ing them, as will also necessarily be the case with the lagoons between 

 the bars and the shore. As will be shown later, the damp banks 

 of the newly formed lagoon may give rise to long lines of vegetation, 

 along which, especially the woody species, the wind-driven beach- 

 sand will accumulate, and, being held by sand-binding vegetation, 

 will eventually form the great transverse ridges, which are topograph- 

 ically so characteristic a feature of Presque Isle. 



The Historical Development and Probable Age of Presque Isle. 



At the mouth of Sandusky Bay, towards the western end of Lake 

 Erie, there is a peninsula. Cedar Point, the terminal portion of which 

 very closely resembles Presque Isle in its general topography and 

 mode of formation. The vegetation is also in many respects very 

 similar. With respect to the physiographic development of the 

 peninsula of Cedar Point, Professor E. L. Moseley has pointed out *' 

 that the succession of vegetational formations, taken in conjunction 

 with certain historical records, furnishes a means of approximating 



" Gilbert, G. K. /. c, p. 89. 



"^ The carrying power of the currents varies with the sixth power of the ve- 

 locity, and the height of the waves is proportional to the square root of the distance 

 through which they are propagated unimpeded. From this it may be seen that the 

 effects produced upon the loose beach sand of the exposed outer extremity of the pen- 

 insula during the occasional great north or northeast storms may be very great indeed. 



1' Moseley, E. L. " Formation of Sandusky Bay and Cedar Point." I'roc. Ohio 

 State Acad. Science, i,: 179-238. (Thirteenth Ann. Kpt.) 1904. 



