260 SPARKS FROM A GEOLOGIST'S HAMMER. 



and citizens of Grand Rapids, still remembering how near 

 to the verge of success Mr. Lyon had reached, seriously 

 agitated the resumption of explorations. Through the 

 personal exertions of Dr. George A. Lathrop, of East Sag- 

 inaw, and James Scribner, Esq., and others, of Grand Rap- 

 ids, a law was passed, which was approved February 15, 

 1859, offering a premium of ten cents a bushel for all 

 salt made from brine obtained by boring within the state, 

 and exemption from taxation of all property employed in 

 the manufactui-e, the bounty to be paid when not less 

 than 5,000 bushels should have been manufactured. On 

 the same date an act was approved for the completion of 

 the geological survey of the state; and on the 9th of 

 March the present writer was commissioned by Gov. Mo- 

 ses Wisner to conduct the survey. As soon as the season 

 permitted he began an examination of the outcropping 

 rocks in southern Michigan. His principal work this sea- 

 son extended from the Detroit River across the southern 

 portion of the state, and north to Newaygo county. These 

 observations, together with those reported by an assistant 

 from Genesee and Saginaw counties, and some less syste- 

 matic original studies in Shiawassee, Genesee and Saginaw, 

 furnished the data on which it was concluded that the 

 formations of the peninsula presented the arrangement of 

 a nest of wooden dishes. The most important determina- 

 tion was the identification of an additional group of rocks, 

 not hitherto noted in the state or elsewhere in the United 

 States. This was intercalated between the limestone, then 

 first ascertained to be the great Carboniferous Limestone 

 of the United States, and the ferruginous sandstones 

 which outcrop extensively in the southern counties. It 

 was designated provisionally at that time the " Gypseous 



