404 J. D. Whelpley on treatment of Gold and other metals. 
channel 75 feet long, 6 feet wide, from 20 to 30 feet high. This 
was filled with vapor of water and sulphurous acid from the 
furnace pools, which made a fine rain; carrying down any 
minute ore-dust which might escape the action of the dash 
wheel, also condensing large quantities of sulphuric acid from 
the sulphurets. 
The gold ores most free from sulphurets are easily worked. 
When the sulphur is in excess, the supply of air and moisture — 
must be proportionately large. ; 
In regard to fuel, the finer the ore-dust before burning, the 
more economical the process. 
In pleces where wood alone is accessible for fuel, the fire-boxes 
should be from 20 to 80 inches deep, below the fire-bridges; 8 
inches for coal. : 
Crushing machinery.—For crushing gold ores previous to fine 
grinding, any ordinary crushing machinery may be employed 
that will reduce them to pea- or gravel-size, as they must not be 
larger than this before entering the pulverizer. : 
e crushing mill used by us is a patented invention of my 
own. It consists of a very heavy and solid bar of wrought iron, 
revolving in the bottom of a cast iron tub as close as possible to 
the sides and bottom of the tub. : 
This bar carries at either extremity a hardened steel or chilled 
iron plate, with a cutting edge welded to a soft iron back to pre 
vent rupture. ; 
The sides of the tub are pierced with holes from an inch to 
half an inch in diameter, forming a coarse sieve, . 
Two of these bars may be used crossed, working four cutters, 
held together by a cast iron center piece of great strength an 
solidity, through which an upright shaft passes, furnished with 
a step anda pulley. The speed of these cutters is a little more 
than 10,000 feet a minute. The broken pieces of quartz ave 
thrown out of the holes in the side of the tub at the rate of /iv? 
tons an hour. 
Pulverizing machinery—The pulverizing of the crushed oe 
performed by flat plates of thin iron faced with chilled-iron, ® 
tached to radiating arms; somewhat like the paddles of a steam 
boat wheel. These revolve inside of a east iron dram, as clos 
as possible to the sides and very near its circumference. A hort 
zontal shaft passes through the centre of the drum. is 
The material, gravel size, is poured in on one side at the a% 
by an automatic hopper, which measures the quantity. fan 
_A powerful draft of air, foreed through the machine by ‘ as 
ower forming an essential part of the apparatus, draws pp te 
dust through a hole on the opposite centre of the drum, Wi" 
‘ also passes, 
