THE ARCILEAN ROCKS. 523 



rence of similar porphyry with the quartzites of the Baraboo 

 ranges, throws all the areas, without question, into the same category 

 as those qnartzites. We have thus a great quartzite series, including, 

 also, quartz-porphyries, and associated with these pinkish, close-tex- 

 tured, (intrusive?) granite. Such an association is not a new one. 



Percival l in alluding very briefly to some of the porphyry and 

 granite areas, the rocks of which, however, he calls by other and in- 

 correct names, intimates that the granite patches (his syenite) form a 

 belt altogether to the westward of the others. This conclusion is not 

 borne out by the facts. The Moundville porphyry lies on a line, as 

 indicated by the 1ST. 32 E. strike, altogether west of the Montello and 

 Marion granites, which are thus, evidently, but portions of the same 

 series. 



The entire width of the granite and porphyry belt, at right angles 

 to the trend, is not less than twenty-five miles, the Mackford area ly- 

 ing on the extreme 'east, that of Montello on the extreme west. The 

 length from the Marcellon area on the south, in a N. 32 E. direction, 

 is 30 miles. Regarding the belt as continuous, as it undoubtedly is, 

 with the Baraboo ranges, it is evident that it must make a great bend 

 northeastward, in the region about Portage. A glance at Plate 

 XVIII of this volume, will suffice to show that, towards their eastern 

 ends, the quartzite ranges are already on the turn. 



The parallelism of the belt thus made out with the edge of the 

 main Archaean area to the northward, is striking, and strongly sug- 

 gests that we have here part of a once continuous band of Huronian 

 surrounding the old northern core, after the manner of the later Silu- 

 rian formations. 



THE NECEDAH QUARTZITE. 



Dotting the great sand plain of the Wisconsin in Juneau and Adams counties, are 

 numerous bold castellated outliers of the Potsdam sandstone, rising abruptly from the 

 plain, and constituting very marked features of the scenery. From the same plain, and 

 only about three miles west from one of the greatest of the sandstone bluffs Petenwell 

 Peak rises the quartzite hill at the foot of which the village of Necedah is built. The 

 rounded contour of this hill serves to mark it at once as different in nature from the 

 sandstone bluffs of the adjoining region. 



The main Necedah bluff lies on the N. W. qr. of Sec. 25, T. 18, R. 3 E., the town 

 line crossing over its eastern end; it is about half a mile in length, with its greatest ex- 

 tension east and west, and is highest, and at the same time most bold and rocky, on its 

 eastern end, which rises 170 feet above the street below, and about 510 feet above Lake 

 Michigan. A short distance southeast of the main bluff, on the N. W. qr. of the S. W. 

 qr. of Sec. 19, T. 18, R. 4 E., is a small, craggy hill, 75 feet high, of the same rock as 

 that composing the main hill, the intervening low ground being underlaid by horizontal 

 sandstone. 



.! Annual Report of Geological Survey of Wisconsin for 1855, p. 105. 



