GEOLOGlC.y;. AND NATURAL HISTORY SURVEYS. 181* 



He thinks the coal beds may extend as far north as township 23, 

 on the head waters of the Muskegon and Tittabawassee Kivers. The 

 coal basin, then, is " nearl}' oval in form, whose center very nearly 

 corresponds with the true center of the Peninsula." Mr. Hubbard 

 omits to state the dips of the strata on Lake Huron north of Saginaw 

 Bay, or along any part of Lake Michigan, or on the northern border 

 of the Peninsula. He does not identify the Mackinac and Monroe 

 limestones. In these latest utterances of the early Micliigan geologists 

 respecting the Lovxer Peninsula we find revealed only a partial concep- 

 tion of the complete dish-like arrangement of the entire body of 

 strata. 



In connection with a statement of strata passed in Lj^on's salt 

 well at Grand Rapids, Mr. Hubbard assumes that the Hillsdale 

 County sandstones have here " thinned out," and it is on this ground 

 that he thinks the gj'pseous shales to occupy the position of the 

 "Hudson flags and shales." It is not intelligible why he did not 

 ratlier identify them with the " kidney iron shales.'" Two beds of 

 beautiful gypsum were passed 4 to G feet in thickness. On the re- 

 lation of the brines he says : 



The strongest brine springs nialce tlieir appearance along a line which will be 

 found to correspond with the synclinal axis, or axis of the dip of the rocks com- 

 posing the great peninsula basin — a circumstance which would be looked for 

 from the fact that the ordinary law of gravitation would conduct the strong 

 brines to the lowest levels of the rock strata. (P. 138.) 



The gypseous clays of Grand Rapids constitute the " upper salt 

 rock " and yield a brine, as he states, stronger than that in Ohio, which 

 sustains a profitable manufacture. But the brine obtained in Lyon's 

 well, at a depth below^ 230 feet, " may be supposed to proceed by 

 veins from the ' lower salt rock,' lying at a still greater depth, and 

 from which the strongest and best supplies of brine in our State may 

 be expected." Mr. Hubbard gives no description from w-hich we can 

 identfy his "lower salt rock." We now know^ tliat a "lower salt 

 rock" (the Salina formation) actuall}' exists; and there are people 

 who claim that this was in the eye of the Michigan geologist (gener- 

 ally, however, supposed to be Doctor Houghton), though, so far as 

 evidence goes, Mr, Hubbard was the only one who had attained tliis 

 view. But it does not appear how the brine could rise from it 

 through a fissure to the higher levels, since so few^ fissures were known 

 in the intervening formations; and these were of so argillaceous a 

 character as not to admit of pern^ianent fissu.res; and if the fissures 

 had existed, the brine, as Mr. Hubbard correctly reasoned, would 

 descend instead of ascending. 



With a comprehensive but condensed review of the economic 

 products of the southern portion of the Peninsula, and some far-seeing 



