2' 



84: GEOLOGY OF EASTERN WISCONSIN. 



of the superior face of the formation is shown to be still a prominent fact. The last 

 mentioned point is 120 mHes from that at which this feature was first desciibcd, show- 

 ing that this is not a local or exceptional character, but one that attaches to the forma- 

 tion throughout this portion of the state, and to some extent, at least, beyond. 



As the formation passes across the Menomonee river into Michigan, it affords us a 

 parting ghmpse at the Grand Rapids. The section is closely similar to that at Oconto 

 Falls, and wiU not be here repeated. A full description is given by Dr^ Rominger m his 

 report on the Paleozoic Rocks of the Upper Peninsula of Michigan, p. 72. , 



Economic Considerations. — Many portions of this formation fur- 

 nish stone well suited for heavy masonry, as locks, piers, founda- 

 tions, etc. Its heavy beds, somewhat siliclous character, and free- 

 dom from shaly matter, render it enduring, while it is wrought with- 

 out difficulty. Other portions are adapted to ordinary construction, 

 and exceptional jjortions are fitted for cutting. 



The rock is burned at numerous points for quicklime, and when a 

 ■judicious selection is made, which is not always the case, M'ith good 

 results. The mass of the formation is not adapted to this purpose, but 

 some parts are exceptionally pure dolomites, and properly burned, pro- 

 duce a most excellent lime. Selection becomes a matter of much im- 

 portance, and as it is equally so with other formations, and other por- 

 tions of the state, the volume on the general geology of the state will 

 contain specific information and directions that will assist in choosing 

 a suitable stone. 



Some of the less pure portions produce a lime tliat forms a slightly 

 hydraulic mortar, suitable for general construction, but whose infe- 

 rior whiteness reduces its value for finishing purposes. In some cases, 

 where the rock is burned at a low heat, the hydraulic property be- 

 comes sufficient!}' marked to be very serviceable in many cases where 

 common quicklime will not answer, and where the more expensive 

 cement is too costly. I am informed by Hon. "Wm. Starr, of Eipon, 

 that formerly, lime of this class from the Lower Magnesian limestone 

 at that place was used for cisterns with success, and that in removing 

 the foundations of a mill that had stood many years exposed to water, 

 the mortar made from this lime was found in excellent condition. 



An analysis of the rock which constitutes a portion of one of the 

 mounds previously described, taken from the JST. W. \ of the N. E. \ 

 of Sec. 20, Ripon, gave the following result: 



Carbonate of hrae 51.68 



Carbonate of magnesia 40.93 



Sesquioxide of iron 0.60 



Alumina 3.09 



Silica 8.16 



Water 0.70 



100.16 



