TOPOGRAPHY. . 661 



region, not included in the prairie area, and whicli is mostly timbered 

 land. The original area of prairie appears, from the government 

 surveys, to have been somewhat greater. At the present time, the 

 original forests of large timber have been mostly cut down, except 

 about the Wisconsin river bluffs, such timber as is now found, being 

 a second growth, of black, white and burr, oaks, maple, hickory, poplar 

 and elm, the trees being of small size, seldom more than a foot in di- 

 ameter. 



Mounds. The nearest approach to mountains in the Lead region 

 are the Platte Mounds in La Fayette county; the Blue Mounds in 

 Dane and Iowa counties, and the Sinsinawa Mound in Grant coun- 

 ty. The former are three in number, about a mile apart, the mid- 

 dle one being very small in comparison with the other two. The 

 east and west mounds are about the same elevation, and are capped 

 with a very hard Niagara limestone to which they doubtless owe 

 their preservation, in the general denudation of the surrounding 

 country. The ground slopes away from them so gently, and blends 

 so gradually with the surrounding high land, that it is impossible to 

 define exactly where the mound proper begins. 



Fig. 3. 



Sketch op the Platte Mounds. 

 1 Niagara limestone; 3 Cincinnati group. 



The Blue Mounds are two in number; one being in Iowa county, 

 and the other in Dane. The' top of the west mound (which is the 

 higher of the two) consists of over a hundred feet of very hard flinty 

 rock, somewhat resembling quartzite ; below this is the Niagara lime- 

 stone. This cap of quartz rock seems to have been removed from the 

 east mound; the top of which is aflat table land under cultivation. 

 These mounds are very conspicuous, and can be seen from any mod- 

 erately high land in the Lead region. 



The Sinsinawa Mound is also a very conspicuous object, in the 

 southern part of Grant county, near the village of Fairplay. It is 

 composed, for the most part, of the Cincinnati group, capped with a 

 small amount of Niagara limestone. 



Sinks. Yery remarkable features in the vicinity of the Blue 

 Mounds are the numerous sink holes found near their base, and fre- 

 quently quite high up on their sides. These sinks are iisually in 

 groups of three or four, and invariably in nearly an east and west 



