Geology of the Region about Beloit. 201 



total thickness of the Trenton limestone at one hundred and 

 eleven feet. 



It will thus be seen that the matching of our Beloit quarries is 

 an interesting problem, somewhat complicated, bnt not too diffi- 

 cult ; a class of college students, with a little oversight and direc- 

 tion from the teacher, are able to work it out with interest and 

 satisfaction. We have just about outcrops enough, and very few 

 superfluous; seven of our Bsloit exposures are needed to com- 

 plete the ascending scale. 



Having now matched our exposures and determined the thick- 

 ness of the various subdivisions, we have only to determine the 

 altitude of each in order to learn whether there is any dip or un- 

 dulation in the strata as traced from quarry to quarry ; or whether 

 they are, as shown on the chart, entirely level. The exposures 

 lie mainly on a north and south line in the face of the west bluff 

 of Rock river; moreover, the river, being set back at this point by 

 the dam, affords a level base line ; the altitude of the exposures 

 above the river has been repeatedly taken by the aneroid barome- 

 ter, and the average of these results is believed to be correct 

 within a very few feet. The undulations which are thus detected 

 are shown in the diagram, although of course greatly exaggerated. 

 It will be seen that the four quarries farthest north show a con- 

 siderable and quite regular dip to the south, amounting to eighty 

 feet iu seven eighths of a mile ; from here the strata rise again to 

 the second quarry, beyond which they continue with but a slight 

 and nearly uniform dip to the south. North of Scott's quarry 

 there are two places where the junction of sandstone and lime- 

 stone is shown in the road, from which we learn that the dip is 

 sharp to the ncr.h. In the upper diagram the strata are traced 

 still farther south, and also north through Janesville to Fulton; 

 and although we know nothing as to minor undulations, we see 

 that in general the strata are almost exactly level except where 

 they drop down so abruptly at Beloit, constituting a little anti- 

 clinal elevation and a deeper synclinal depression of eighty feet ; 

 indeed, from Fulton to Rockton, a distance of thirty miles, the 

 fall is only ninety-four feet ; while at Beloit^ as we have seen, the 

 fall is almost as great in less than a mile. Although we know 



