Jennings : A Botanical Survey of Presque Isle. 295 



the ages of various topographic structures, as well as of tracing their 

 origin and development. 



According to Moseley's classification the peninsula of Cedar Point 

 consists of three portions : the bar, the dune-section, and the ridge- 

 section. The dune or middle section represents a higher portion of 

 the former mainland, now covered by sand, which reached farther out 

 into the lake and formed a continuous coast-line with the mainland 

 farther to the southeast. With the differential tilting of the lake 

 basin, however, most of this portion of the mainland was inundated, 

 leaving the dune-section more or less completely an island. A sand- 

 bar soon connected this section with the mainland again to the south- 

 east, thus constituting " the bar." This bar has been gradually shifted 

 back over and upon the marsh behind it, as, especially, during the 

 high water of 1858-1862. 



This bar was evidently formed mainly by a swirl from the main lake 

 current passing the islands, the rotation being from left to right and 

 thus sweeping the beach-debris from the mainland at the mouth of 

 the Huron River towards the dune-section. Eventually the sand accu- 

 mulated sufficiently to begin the formation of a sand-spit at the 

 northern extremity of the dune-section, the accumulating sand being 

 heaped into long narrow ridges or bars by the exceptional action of 

 high surf during great northeast storms, especially in periods of high 

 water in the lake. The further growth of the ridges was due to the 

 accumulation and retention of drifting sand by the vegetation growing 

 upon them or along their sides. 



The ridge-section of Cedar Point is about half a mile wide and in 

 its middle portion are eight distinct ridges separated by long narrow 

 depressions. These ridges are very similar indeed to those of Presque 

 Isle. The latter, however, are considerably larger and wider, although 

 scarcely higher. 



The ridges of Cedar Point have been designated by Moseley by the 

 numbers, i to 8, from the oldest to the most recent. Ridge No. 8 is 

 about four feet in height above Lake Erie, and its vegetation consists 

 of partially buried. cottonwoods together with a few willows. The 

 cottonwoods showed five rings of annual growth and the ridge is sup- 

 posed to have been thrown up about 1897 or 1898. The jetty at the 

 end of the peninsula, begun in 1896, probably offered an obstruction, 

 and resulted in the accumulation of the sand forming this ridge. 

 Cottonwoods under such conditions as obtain at Cedar Point or at 



