ARCHJEAN FORMATIONS. 253 



Rocky Island, later formations intervene, so that they must be regard- 

 ed as forming three distinct, though closely associated, surface areas. 



The first mentioned outlier of the last group still preserves on its 

 exposed surface the scorings of the drift forces, there being two sets, 

 the one pointing S. 33 "W., and the other S. 55 W. 



From the several outliers there stretch away to the southwestward 

 trains of bowlders of quartzite, which gradually spread out into a fan- 

 like form, the fragments meanwhile becoming more rounded, smaller, 

 and scattered. I have traced them fifty miles distant into Illinois. 

 A figure illustrating these facts has already been given. Their special 

 significance here relates to the question whether other masses of 

 quartzite protrude through the Paleozoic formations in this region. 

 If so, they should indicate their presence by erratics in the drift. 

 Bowlders, in limited numbers, reach about three miles east, and a 

 somewhat greater distance north of the outcrops, but as traced in 

 those directions, no concentration toward a point of origin was ob- 

 served with sufficient definiteness to locate their source. 



The discovery of a train in the town of Waterloo led to more sat- 

 isfactory results. The abundance of angular blocks in the drift led 

 to the conviction that their source was in the immediate neighbor- 

 hood, and, under the guidance of the Rev. Gr. S. Hubbs, the actual 

 outcrop was found. Like the others, it lies at the foot of a ridge on 

 the border of a marsh. The exposure is small, but interesting. 



At one point there is a very fine exhibition of ripple marks running 

 parallel to the dip, thus demonstrating the true 

 tilting with certainty. This was found to be 



E., the strike being K 45 W. 

 The rock of all these outcrops is a hard, 

 OUTLIER, thoroughly metamorphosed red, or gray quartz- 

 Town of Waterloo. j te> Metamorphic conglomerates occur in cer- 

 tain portions: In others there is a foliated material of talcose appear- 

 ance, yet seldom sufficient to give the rock a schistose structure. The 

 gray variety of quartzite predominates, especially in the more westerly 

 outliers, while the red is more abundant in the eastern. 



The relations of these quartzites to the surrounding formations are 

 exceedingly interesting. About eighty rods south of the outlier in 

 Waterloo, the lower layers of the Trenton limestone, reposing upon 

 the St. Peters sandstone, occur at the same level as the quartzite, with 

 no indication of disturbance. The accompanying figure will render 

 the situation clear. 



In the intermediate space are bowlders of conglomerate, the peb- 

 bles of which are of quartzite, precisely similar to that of the out- 



