ORES OF LEAD. 147 



ably for their extent. They occur in limestone, in the States 

 of Missouri, Illinois, Iowa, and Wisconsin ; argillaceous 

 iron ore, pyrite, calamine and smithsonite ("dry bone" of 

 the miners), blende ("black-jack"), carbonate of lead or 

 cerussite, and barite or heavy spar, are the most common 

 associated minerals ; and less abundantly occur chalcopy- 

 rite and malachite, ores of copper ; also occasionally the 

 lead ores, anglesite and pyromorphite ; and in the Mine La 

 Motte region, black cobalt, and linnagite an ore of nickel. 



Lead ore was first noticed in Missouri in 1700 and 1701. 

 In 1720 the mines were rediscovered by Francis Renault and 

 M. La Motte ; and the La Motte bears still the name of the 

 latter. Afterward the country passed into the hands of 

 Spaniards, and during that period, in 1763, a valuable mine 

 was opened by Francis Burton, since called Mine a Burton. 



The lead region of Wisconsin, according to Dr. D. D. 

 Owen, comprises 62 townships in Wisconsin, 8 in Iowa, and 

 10 in Illinois, being 87 miles from east to west, and 54 miles 

 from north to south. The ore, as in Missouri, is abundant, 

 and throughout the region there is scarcely a square mile 

 in which traces of lead may not be found. The principal 

 indications in the eyes of miners, as stated by Mr. Owen, 

 are the following : fragments of calcite in the soil, unless 

 very abundant, which then indicate that the vein is wholly 

 calcareous or nearly so ; the red color of the soil on the sur- 

 face, arising from the ferruginous clay in which the lead is 

 often imbedded; fragments of lead ("gravel mineral"), 

 along with the crumbling magnesian limestone, and den- 

 dritic specks distributed over the rock ; also, a depression of 

 the country, or an elevation, in a straight line ; or " sink- 

 holes ; " or a peculiarity of vegetation in a linear direction. 

 The ore, according to Whitney, occupies chambers or open- 

 ings in the limestone instead of true veins, and in this 

 respect it is like that of Derbyshire and Northern England. 



The mines of Wisconsin and Illinois are in Lower Silurian 

 limestone of the Trenton period, called the Galena lime- 

 stone ; those of Southeastern Missouri, situated chiefly in 

 Franklin, Jefferson, Washington, St. Francois, St. Gene- 

 vieve, and Madison counties, are in the " Third Magnesian 

 limestone ; " also Lower Silurian, but, of the Calciferous or 

 Potsdam period ; those of Southwestern Missouri, situated 

 mostly in Newtown, Jasper, Lawrence, Green and Dade 

 counties, and in the western part of McDonald, Barry, 



