MCHENRY AND LAKE COUNTIES, 131 



In the northeastern part of Lake county, along the bluffs north of Wauke- 

 gan, the Devonian beds of Wisconsin appear to have contributed largely to the 

 debris of the Drift ; in a collection of fossils, all more or less worn but mostly 

 recognizable, which had been picked out of the gravel beds of this region by 

 Mr. J. W. Milner, a very enterprising and zealous resident collector, I noticed 

 a very large proportion of Devonian species, apparently of the age of the Ham- 

 ilton group. 



In McHenry county, we find this formation presenting much the same gen- 

 eral characters as further to the eastward. In the vicinity of the Fox river 

 the same kind of gravel ridges are met with as those which have been described 

 as occurring in the western part of Lake county. In the central and western 

 portions of the county, the mass of the Drift appears to consist of clay and hard- 

 pan, with occasional boulders. We have, however, in this county, accounts of 

 logs of wood and other vegetable remains being found at various depths in these 

 deposits, a feature which appears to be wanting, or extremely uncommon in 

 Lake county. One such instance of the finding of a cedar (?) log seven inches 

 in diameter, at the depth of forty-two feet below the surface, is reported, on 

 the land of Mr. Thos. Dufifield, near the eastern line of section 13, township 

 44, range 6. Other instances are reported in various parts, at depths varying 

 from fifteen to fifty feet or more. Such of these tree trunks, etc., as are found 

 within fifteen or twenty feet of the surface may, perhaps, belong to a later 

 period than that of the mass of the Drift, but those which are met with at 

 depths of forty or fifty feet, or even more, cannot, it seems to me, be properly 

 so referred. 



Niagara Group. This formation, probably, underlies the whole surface of 

 the district, with the exception of a narrow strip along its western border; its 

 outcrops, however, are limited to two or three localities. For this reason, 

 therefore, its boundaries can be determined only approximately, by lines drawn 

 from localities beyond the limits of the district. The outcrops, judging from 

 the character of the rock, appear, with perhaps one exception, to be confined 

 to the upper or middle portion of the group, and are as follows : 



In the northwest quarter of section 31, township 44 north, range 11 east, on 

 the land of Mr. Thomas Rawson, a ledge of light gray limestone, weathering to 

 a pale yellow or buff color, has been opened to a limited extent. The exposure 

 is not natural, the top of the ledge having been originally covered with earth 

 to the depth of about a foot or eighteen inches, and was only discovered as late 

 as the year 1867. The depth of the excavation is about six feet, the rock 

 showing no signs of stratification whatever, but becoming rather darker in color 

 and more dense in the lower part of the exposure. Although in its upper por- 

 tion the stone seemed to be almost entirely made up of disintegrated organic 

 remains, but few fossils were collected, a few corals and an internal cast of 



