412 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



direct result of investigations in the Dubuque lead region. So far 

 as we know the conception originated with Henry Schoolcraft, a 

 naturalist of singularly wide accomplishments, who was the nar- 

 rator and mineralogist of the Cass expedition to the sources of the 

 Mississippi river in 1820. 



On the return journey of the Cass exploring party Schoolcraft 

 left his companions when Prairie du Chien was reached and made 

 a side trip to the Iowa mineral district. Of this he gave the best 

 detailed description up to that time and for a generation thereafter. 

 This traveler had previously investigated the lead mines of south- 

 east Missouri and had published full accounts of them and of the 

 methods of mining and treating the ores. 



As an outcome of his Iowa visit Schoolcraft conceived the no- 

 tion that the Iowa and Missouri mineral belts were genetically re- 

 lated. He fancied that the lead-bearing strata of the two widely 

 separated localities were stratigraphically identical.^ In this opinion 

 he was doubtless largely influenced by Nuttall's parallelism of the 

 Iowa rocks with the English lead-bearing rocks of Derbyshire. The 

 fact that he designated the formation the Metalliferous Limestone 

 is significant. In after years both Keating and Featherstonough fell 

 into the same error by calling the Iowa lead rocks the Magnesian 

 Formation and the Galeniferous Limestone, in commemoration of 

 the fact that in England the same names were used for the lead- 

 bearing formations above the Mountain Limestone, which were re- 

 garded as Permian in age. The statement was repeated as fact for 

 many years afterwards. 



Schoolcraft's idea was from time to time elaborated, until its 

 necessary consequences had to be finally supported by the assump- 

 tion that the ore bodies were primarily deposited under the influence 

 of favorable local currents on the floor of the ancient ocean. In 

 some form or other this curious notion quite generally prevailed for 

 more than half a century. Even at the present day it is in some 

 quarters seriously upheld. 



With certain severe limitations Schoolcraft's theory is still one 

 of the most useful geological tenets in mining. 



GEOGRAPHIC DELINEATION OF IOWA 



So soon as Congress, in 1838, made provision for erecting a new 

 territory under the name of Iowa the engineering corps of the 

 United States army sent out a party to prepare a detailed map of 



•Narrative Journal of Travels etc., to Sources of Mississippi River, Caas 

 Exped., 414 pp., Albany, 1821. 



