The JfunK-scong Islands. — I'aylor. 29 
vated mass of Silurian limestone, in many respects like Mack- 
inac, only it is not so high and is not now an island. On the 
hill back of St. Ignace near the public school building we 
found a large bed of beach gravel at an altitude of about 75 
feet above the lake. About a mile out of town there is a great 
curved beach ridge which extends around the edge of a flat 
tract forming a parapet in the shape of a horseshoe. The 
apex of the curve points toward the north over low ground 
and the road crosses the ridge twice and also the enclosed 
hollow only a little back of the point. One can seldom find 
as perfect a beach ridge as this, showing so clearly by its 
shape and place the nature of its origin. The southward ex- 
tension of the ridge on the two sides could not be seen beyond 
80 or 40 rods on account of the timber. The west ridge ap- 
peared to extend south-southeast in a straight line. The al- 
titude of this beach above the lake is about 115 feet. Its 
formation undoubtedly took place substantially in the follow- 
ing way. In the rising stage of the water the flat- topped 
area was covered by the waves with gravel derived from ad- 
jacent limestone clitfs which rise to a higher level. Then the 
whole was submerged and remained for a time as a gravelly 
shoal. Finally as the water fell awa}^ again the waves re- 
newed their action, and when they began to break along the 
outer edge they heaped up the shifting gravel into a ridge at 
that place. 
After crossing a swampy tract the road comes out upon the 
shore of lake Michigan and continues to the northwest close 
to the lake. For about six miles it follows a great bank of 
beach gravel and pebbles which lies against the base of a 
high limestone clitf. At several places this cliff is vertical 
for 50 to 80 feet and there are several picturesque outlying 
remnants like the "Sugar loaf" on Mackinac island. The up- 
per limit of the littoral bank where best developed is about 
45 feet above the lake, but the talus of the cliiT rests upon it 
and obscures it in many places. Its composition, like the 
other beaches of this vicinity, is almost entirely of rounded 
pebbles of the local limestone. The quantity of beach mate- 
rial here is very great. The width of thfe bank varies from 
about 300 to 600 or 800 feet. The surface generally shows a 
