164 Tlie American Geologist. March, 1900 
nation of the thickness of the shale at the mound is known 
to ha\'e been made, but it is fully one hundred feet thick 
and all above the countr)' level of the ridge. 
Next above the shales comes the Niagara limestone at- 
taining a considerable thickness here, about two hundred 
seventy-five feet.* The lower part is a limestone similar to 
the Niagara in other localities in this region, f while the up- 
per part is a rock much resembling an iron-stained quartzyte. 
These divisions do not correspond with those found at Ra- 
cine, Wisconsin. ;|; The divisions of the Niagara are not 
very permanent. This hard layer caps the mound with 
something like one hundred twenty-five feet of flint}- rock, 
and to its presence as well as to the location of the mound 
on the watershed is due the preservation of the lower strata 
and consequenth' the very existence of the mound. Its 
total hight is seventeen hundred tvvent}-five feet above sea 
level. § 
To this la)'er is due also in part the form of the hill. The 
top is a tlat area almost as smooth as a floor of some one 
hundred by one hundred fifty rods extent covered by blue 
grass and white clover pasture. Hazel brush and young 
oaks of six to ten )'ears growth abound. The slopes below 
this plane are very abrupt, rocky and forest clad to the base 
of the quartzyte. The mound is nearly circular at its sum- 
mit, but as the descent is made the form becomes more and 
more elongated east and west, along the length of the ridge 
until at an elevation of fourteen hundred feet, it is so ex- 
tended as to include the East mound. At the base of the 
quartzyte issue a number of springs, some quite small be- 
coming dry in continued drouth; but one on the northeast 
side, a veritable living fountain, sends its cool waters tumb- 
ling down the rocky slope. It will thus be seen that much 
of the water falling on the summit, percolates through the 
rocks to these springs. At least three-fourths passes out in 
this way. 
*Wis. Geol. Surv. Atlas & Sections. 
tWis. Geol. Surv. 
111. Geol. Surv. V. 5, p. 33. 
tWis. Geol. Surv. V. 2, p. 335. 
Wis. Geol. Surv. V. i, p. 181. 
§Wis. Geol. Surv. Vol. 4, p. 747. 
!|Wis. Geol. Surv. Vol. 2, p. 658. 
