o 



O LOWER PENINSULA. 



same horizon. Of deep artesian borings, several have been 

 made within the city limits of Monroe to a depth of from 150 

 to 300 feet, and the boring records of some have been noted 

 down. Such notes are very useful for comparison of strata, if we 

 were only beforehand informed of the geological structure of a 

 locality, in its details ; but to learn these details by the results of 

 borings alone is very unsatisfactory. 



As an illustration, I give one of the records of a drill hole 

 sunk in the Court-House Square of Monroe to a depth of 140 feet. 

 It reads : 



Clay and sand 6 feet. 



Gray limestone 3 " 



Blue limestone 6 inches. 



Dark gray limestone 3 feet. 



Blue limestone \\ " 



Gray limestone 14 " 



Blue limestone 2 " 



Gray limestone 39 " 



Blue limestone 5 *' 



Gray limestone 2 " 



Blue limestone 32 " 



Blue shale 39 " 



We see here a number of limestone beds, varying in color 

 and compactness, amounting to over 100 feet in depth, and 

 below, a deposit of calcareous shales, which could perhaps be taken 

 as representing a part of the Onondaga formation ; but the inform- 

 ation we receive by this record is insufificient to enable us to 

 form a clear idea of the special qualities of the rock beds, 

 or to distinguish positively certain horizons. From another bor- 

 ing made in the same place, I received, through the kindness of 

 Judge Christiancy, specimens of the rock brought up by the pump, 

 by which I can see that, to a depth of 300 feet below the surface, 

 limestone beds are almost exclusively following each other in con- 

 tinued superposition ; but these limestones, of a dolomitic character, 

 sometimes light-colored, sometimes dark, partly laminated, or 

 other specimens of a cellulose structure, full of irregular cavities, 

 clothed with spar crystals, or pieces pervaded with acicular spar 

 crystals, are all without prominent peculiarity by which one can tell 



