TOPOGRAPHICAL SUBDIVISIONS. 453 



TOPOGRAPHICAL SUBDIVISIONS RESUME. 



The foregoing details, with regard to the surface slopes, river 

 systems, surface reliefs, prairies, marshes, timber, etc., of central 

 Wisconsin, will serve to render intelligible to the reader a very 

 brief summary of the topographical features of the whole dis- 

 trict. 



First, then, we find on the north, occupying all of Marathon and 

 most of Portage, Wood, and Clark counties, a comparatively elevated 

 region of crystalline rocks, which descends gradually from an 

 altitude of 900 feet on the north, to one of 400 to 500 feet on the 

 south. In general, this section has a gently undulating surface, 

 which is, however, often broken in minor detail by low, abrupt ridges 

 with outcropping tilted rock ledges, and is dotted occasionally with 

 high points of quartzose rocks. The whole area is densely covered 

 with a forest of pine interspersed with marshes, and hardwood ridges, 

 which when cleared yield excellent land. It is traversed from north 

 to south by two large rivers, the Wisconsin on the east, and the 

 Black on the west, which, as also their numerous branches, are 

 rapid streams, broken constantly by chutes and water falls over tilted 

 rock ledges; and is covered everywhere with accummulations of drift 

 material, which are, however, much greater in some places than in 

 others. 



Proceeding now further southward we come next upon the great 

 central sandstone region of the state. This covers all of Jackson, 

 Juneau, Adams, Marquette and Waushara counties, southern Wood, 

 Portage and Clark, northern and western Columbia, and most of 



G ' ' 



Sank. It extends east and west about eighty miles, north and south 

 about one hundred, and really includes several subordinate areas, 

 which are, in some respects, topographically distinct, but all of which 

 have in common the basement rock of sandstone, and, for the most 

 part, the sandy soil. For the greater part of its area, the sandstone 

 district is out of the heavy timber, which, however, invades it in east- 

 ern Waushara, in southern Portage and Wood, and in eastern Jack- 

 son. For the rest of the district, the prevailing growth, except on 

 the high Archaean bluffs of Sank, is of small oaks. 



Of the subordinate areas, we note first on the east a district (1), 

 including Waushara, southern Portage, those portions of Marquette 

 and Green Lake which lie north of the Fox river, and southern 

 Adams, which is everywhere heavily covered with glacial drift, to 

 whose irregular morainic method of deposition is to be attributed a 

 peculiar roughened surface, dotted in places with small lakes that oc- 



