Taylor — Highest Shore Line on Mackinac Island. 211 



it is three times this width. In some places two or more 

 ridges run together and form one, as is often observed else- 

 where. On the short range four heavy ridges are clearly seen 

 with possibly a fifth less distinctly formed. In two of the 

 wider troughs, which are five to six feet deep between the 

 main ridges, there are apparently several other little ridges, 

 one to two feet in height. A road which runs parallel to the 

 range and close to its west side cuts the top of each ridge and 

 shows its composition to be a characteristic beach formation. 

 The 205 foot beach is not only the highest one of the series 

 here described, but also the highest on the island. If this 

 ridge be followed through its full extent around the higher 

 ground, it will be found to surround a small tract on three 

 sides. On the remaining side, which is a long, straight line of 

 limestone cliffs facing towards the northeast, all the beach 

 ridges, except the lowest or 170 foot ridge, are wanting. This 

 beach is situated at a considerable distance from the cliff, and 

 the ground between is a broad, level plain with an altitude of 

 170 to 175 feet. On this plain a heavy talus of fragments and 

 angular limestone bowlders lies against the base of the cliff. 

 While the waves were forming the 205 foot beach around the 

 other sides of the circumscribed tract, they were beating against 

 this northeast cliff and the water on the plain at its base was 

 30 to 35 feet deep. 



The little island of ancient times, thus defined, was about 

 three-fourths of a mile long and less than half as wide, with its 

 longer axis running about northwest and southeast. Its north 

 end was a sharp promontory formed by the long cliff facing 

 northeast, as just described, and another shorter one facing 

 almost directly west. At the base of the latter the 205 foot 

 beach is well developed, but it is very narrow and the ground 

 drops off rapidly westward to the 170 foot plain. The highest 

 point of the ancient island is at its southern end which forms 

 a rounded promontory and rises to a little less than 100 feet 

 above the 205 foot beach. This point is now crowned by the 

 earthworks of old Fort Holmes, built in 1812, and the descent 

 to the 170 foot plain on the east, and to the 205 foot beach on 

 the south is a steep slope of drift. On its west side, and about 

 a cpiarter of a mile south of its north point, the surface of the 

 island descends gradually to the 205 foot level. The upper 

 beach is here wide and flat and encloses a considerable tract of 

 low ground behind it. 



All of my measurements of altitude were made with an 

 aneroid barometer and are subject to the inaccuracy of that 

 instrument. But the 170 and 205 foot beach levels represent 

 in each case the mean of more than a dozen independent ob- 

 servations taken under favorable conditions and are therefore 



