GEOLOGICAL AND NATURAL HISTORY SURVEYS. 161 



brine springs in Michigan and Ohio, led him to advance the opinion 

 that in this State, as well as Ohio, success might follow the " sinking 

 of shafts through the rock strata " in the vicinity of the salines. He 

 adds : 



I do not hesitate to give it as my ouiulon, drawn from a careful examination 

 of the subject, that points may be selected where these operations may bo con- 

 ducted with the strongest prospects of eventual success. 



The general geology of the Lower Peninsula is treated in the first 

 report, under the following subdivisions : 



1. The Upper Sandstone of the Peninsula: He here embraces the 

 sandstones exposed in the counties of Hillsdale, Jackson, Calhoun, 

 Kalamazoo, Livingston, Ingham, Eaton, Barrj', Shiawassee, Clin- 

 ton, and the eastern part of Ionia. A large number of outcrops are 

 eniunerated. It is evident now that the localities mentioned belong 

 to three different ages. 



2. Gray limestone: This he regards "without doubt, identical 

 with the mountain limestone of European geologists." Numerous 

 outcrops are described, but these embrace localities of the Corniferous 

 limestone, the lower Carboniferous limestone on the Charity Islands, 

 and coal measure limestones in Shiawassee and Midland counties. 



3. Lower Sandstone or graywacke group: Here are included the 

 sandstones of Point aux Barques and the red sandstone of Lake Su- 

 perior, which he thinlvs " may be referred to the lov/er portion of 

 this group." 



4. Coal, the existence of which is distinctly announced. 



5. Gypsum: This, he pays, is apparently of considerable extent in 

 Kent County. 



6. Clay. 



7. Sand. 



8. Marl. 



9. Bog iron ore, 



10. Mineral springs: Several highly sulphurated springs occur in 

 Monroe, " and the waters being also charged with carbonate of lime, 

 give rise to considerably elevated mounds of calcareous tufa." Ho 

 mentions the remarkable spring in a marsh in the town of Havre, 

 Monroe County, which has a circumference of 150 feet and a depth 

 of 35 feet. He alludes to the great physical difficulties encountered, 

 the sparseness of the population, and consequent lack of local infor- 

 mation; and SQjs that the appropriation has not been enough "to 

 cover even the traveling expenses of those engaged in these arduous 

 duties." 



The geological corps consi.=;ted of Douglass Houghton, geologist; 

 Abram Sager, principal assistant in charge of botanical and zoo- 



