254 REPORT OF NATIONAL MUSEUM, 1884. 



at tlie Loue Elm Works. Joplin, Mo. It is the production of a pig lead 

 and a white lead direct from the ore in two operations. It is a process 

 that is only applied here and is not very well known. This collection in- 

 cludes the ore, the fuels, and fluxes, with a largo series of the flue dusts, 

 the pig-lead and slag obtained in the first operation; the flue dust 

 after it has been ignited ; a large series of white flue dusts obtained 

 in the second operation ; and a material known as white lead, which is 

 used extensively as a paint, but which diflers completely from the white 

 lead obtained by corroding pig-lead. This material is mainly a sulphate 

 of lead, containing, however, a considerable amount of zinc, which comes 

 from zinc minerals found associated with the galena in the ore, while 

 the white lead obtained by corroding pig-lead is a basic carbonate of 

 lead. 



Illustrations of the application of lead are somewhat numerous in the 

 Centennial collections, but there is an opportunity to make several im- 

 portant additions. The only one, however, that was secured last sum- 

 mer was an interesting collection showing the manufacture of white 

 lead by the corrosion process. This collection includes the metallic lead 

 arranged in crucible for corrosion, acetic acid used, the bark with which 

 the pile of crucibles is covered and upon fermentation furnishes the 

 necessary carbonic acid, the white lead obtained in the crucibles, the fin- 

 ished white lead, and the white lead ground in oil. To these are added 

 specimens of litharge, red lead, and orange mineral. 



Copper. — Illustrations of the free copper ores from Lake Superior 

 contained in the Centennial material, although quite full and extensive, 

 were not at all systematic, and Messrs. Kirby and Zukoski being in the 

 Lake Superior region when they commenced collecting, it was thought 

 best to have them commence by making some systematic collections 

 there. The copper occurs at Lake Superior in three distinct forms : 



First, the so-called mass mines, which are characterized by the occur- 

 rence of large masses of free copper, amounting in some cases to many 

 tons of metal in a single mass. Besides these large masses these mines 

 also carry considerable disseminated free copper. 



Second, the amygdaloid mines, which are characterized by the occur- 

 rence of the free copper in amygdules, bunches, strings, and sheets, from 

 the size of a pin-j)oint up to a few hundred pounds in weight (with rarely 

 a large mass) disseminated in a soft amygdaloid trap-rock. The aver- 

 age percentage of copper in tlie ores from these mines varies from three- 

 quarters of 1 per cent, to 2 per cent. 



Third, the conglomerate mines, which are characterized by the occur- 

 rence of the free copper mostly in strings in a hard conglomerate of fer- 

 ruginous quartz pebbles. The average percentage of copper in the ores 

 from these mines varies from 4 per cent, to 6 per cent. 



To illustrate the occurrence of mass copper Mr. Zukoski made a col- 

 lection at the Central Mine. This collection includes sections of the 

 formations beginning with the hanging wall and following through 



