METALS AND THEIR ORES. 45 
the middlings, a mixture of the other two kinds, which is made to go 
through the machine a second time. Without technical description, this 
apparatus may be styled a trough about 4 by 2 feet, placed over a bellows 
blowing 300 to 500 times a minute, according to circumstances. The air 
is forced through a perforated metallic plate, and the box is at the same 
time skaken. By these means the pulverized ore is separated into the 
three kinds of powder mentioned, according to relative weight, and grad- 
ually slides to the lower part of the boxes, the separation being facili- 
tated by a slight inclination and the presence of diagonal partitions of 
metal strips. An attendant watches the delivery of the product into 
boxes, properly separating the three kinds with the assistance of mova- 
ble partitions. One person can easily attend to the three machines 
employed in the mill, and perhaps as many as five. It is his business 
also to remove the boxes receiving the finished products as often as 
necessary, put the ore into the barrels provided for it, the refuse into its 
place, and the middlings back into hoppers. Meanwhile, another person 
in the basement watches the wet jig, where large sieves filled with the 
coarser rock are jigged underneath water, and the heavier parts sink to 
the bottom. In a short time the worthless material is thrown away, the 
heaviest put upon a steam-heated table and dried, preliminary to package 
in barrels for transportation, and the middlings saved for another wash- 
ing. I have examined the tailings left from both kinds of jigs, and 
observe that scarcely any ore escapes. Both processes separate the ore 
very carefully, and the waste is only slight. One grade of the ore re- 
mains,—the dust or slums. At present this is preserved for experi- 
ment, as the best method of saving the copper ore in it has not been 
perfected. Tossing in water is recommended, and will perhaps be the 
most convenient method of separation. It seems to me that a wet chem- 
ical process might be used to good advantage, such as will be described 
presently. 
I have been greatly pleased with the results obtained practically by 
this mill, and think that the processes employed will enable our mining 
companies to utilize their poorer ores to better advantage than before, 
I understand that the Chubb patent embodies peculiarities not existing 
in any other separator, and is better adapted than any other machine for 
this class of ore. It has been in use many months in Lyman, and has 
