Wisconsin and Missouri Lead Region. 61 



to reach a vein that will make a show, and attract a purchaser. 

 The fissure is in hraestone, its greatest width about four feet, and 

 has been traced east and west about fifty yards. 



Mine La Motte. — This tract of country is about twenty miles 

 east of the Iron Mountain, and is celebrated as containing some 

 of the oldest and most profitable mines in Missouri. It consists 

 of 24,010 acres of land, over different parts of which lead ore 

 has been raised for more than one hundred years. The rock 

 formation over the most of it is the sandstone and limestone, in 

 horizontal strata. Through these, a rock resembUng granite has 

 forced iis way, and forms ridges and ledges, which make up the 

 remainder of the tract. It is a hard compact rock, composed of 

 quartz and feldspar without mica, and usually of a red color. At 

 its point of contact with the limestone are frequently found hori- 

 zontal seams of ore, both copper and lead, and these are also 

 found in many places where no rock at all is exposed for several 

 feet down. 



The following section shows the position of one of these cop- 

 per ore veins as far as it has yet been followed. 



Fig. 4. 



Tlssiires 



The locality is called the Philadelphia mines. The ore is a 

 carbonate, mixed with what I then took for black oxide of cop- 

 per, and a considerable proportion of ochre. Until the specimens 

 arrive, and I have an opportunity of carefully examining them, 

 1 cannot speak positively of their richness. What I mistook for 

 black oxide of copper in a specimen I preserved from another 

 locality in this tract, I have since found to be an oxide of cobalt 

 and manganese, as will be seen farther on. And I now believe 

 the black earthy mineral that forms a considerable part of the 

 mass of some of the copper ores at the Philadelphia mine, to be 

 the same oxide of cobalt and manganese. The ore is found i[] a 

 bed consisting of clay with layers of slate and ore irregularly 

 mixed. It is under a stratum of limestone which is very near 



