40 LOWER PENINSULA. 



Another boring was made four years ago close to the bed of 

 Thunder Bay River. It commenced in rock beds which are at least 

 lOO feet lower than the strata composing Partridge Point. The 

 boring commenced in limestones, which continued, without much 

 interruption by other beds, to a depth of 400 feet below the sur- 

 face, when blue shales were struck, and a powerful stream of min- 

 eral water rose to the top, carrying with it many well-preserved 

 fossils of the shale beds. The fossils were : Cyathophyllum 

 Houghtoni, Cyathoph. Hallii, various species of Favosites, Clado- 

 pora, and numerous Biyozoa, Crinoid stems, Atrypa reticularis, 

 Spirigera concentrica, Spirifer mucronatus, Cyrtina Hamiltonensis, 

 etc. The thickness of the shale was found to be 80 feet. Below 

 it, limestones of variable hardness and color were penetrated to 

 the depth of 600 feet from the surface, and from there to 1025 

 feet, light-colored, partly dolomitic limestones were found. At this 

 depth a bed of solid rock-salt was struck, after which the boring 

 was discontinued. The upper 480 feet of this drill-hole are posi- 

 tively made up by strata of the Hamilton group, which, with ad- 

 dition of the 100 feet of higher strata, would give 580 feet for the 

 thickness of the Hamilton group, and in all probability a part of 

 the limestones below the shales also belong to that group. The 

 lower light-colored limestones represent the Helderberg group, 

 and their dolomitic strata may be equivalent with the lower 

 beds of Mackinac Island, and with the subjacent Onondaga group. 

 The deposit of rock-salt is at all events identical with the rock-salt 

 deposits of Goderich in Canada, and with the Onondaga salt deposits 

 of New York State. The salt brine of Saginaw valley belongs to an 

 entirely different and much higher horizon, to the Waverly forma- 

 tion. After the boring was finished, pumps were set in the tubed 

 hole, and a concentrated brine was lifted to the surface, which, 

 after pumping for a while, became weaker and weaker, until at last 

 a very weak brine only came up. If the pumping was interrupted 

 for some hours and commenced again, a strong brine could be 

 obtained for a while, when the weaker grades would reappear. 

 This discouraged the owners of the well, so that nothing more was 

 done. I told them the reasons for this, explaining to them that 

 the salt being in solid condition, had to dissolve first in the water 

 which runs upon it from above, and required time to become satu- 

 rated, so that after the strong solution, the quantity of which could 



