Introduction. 
257 
account contains a review of previous literature upon the sub¬ 
ject together with the results of a brief examination of the dis¬ 
trict. The two areas recognized by Dr. Percival were here 
described as one. The rock was designated a quartzite, in 
places a metamorphic conglomerate with seams of talco- 
silicious schist. The layers were thought to incline to the N. 
N. E. at a high angle, but this and the strike were not satis¬ 
factorily made out. The adjacent sandstone was referred to the 
Potsdam as is the case with the Baraboo outcrops, but the for¬ 
mation was for the first time correctly referred with its com¬ 
panion range at Baraboo to the Huronian age. 
The first detailed description of the area is found in the 
second volume of the reports upon the Wisconsin G-eological 
Survey.* In the chapter describing the Archaean formations of 
the region, Dr. Chamberlin mentions three separate groups of out¬ 
crops and notes in each the principal ledges. He determined 
also their true relations to the adjacent sandstone, shales and 
conglomerates and the underlying Lower Magnesian and over- 
lying Trenton limestone. The dip and strike of several of the 
outcrops were noted, but no attempt was made to correlate these 
observations. The occurence of glacial striae on several 
of the ledge areas was noted, and in the chapter on the 
quaternary formations their importance as points of origin of 
extensive bowlder trains was made prominent.! In two subse¬ 
quent articles on the glacial geology of the region, published in 
the reports of the U. S. Geological Survey, President Chamber¬ 
lin has briefly referred to these outcrops and indicated their 
bowlder trains. In Dr. Irving’s chapter in the Wisconsin re¬ 
port already referred to,f this area is briefly described and 
mapped with the other isolated outcrops of the region, the whole 
series being grouped with an outlying Huronian belt peripheral 
to the Archaean area. In this author’s subsequent reports upon 
the crystalline rocks of the lake Superior region these relations 
are several times brought out. 
The peculiar dynamic action to which these quartzites have 
*Geology of Wisconsin, Vol. II, p. 252. 
tlbid, p. 202. 
JIbid, p. 501. 
