Crane.| Prospecting, Mining and Milling Machinery. 231 
building, and receives practically all of the waste product of 
the mill. 
THE Jig Room.—The jig room is the main room of the mill 
and contains practically all of the concentrating machinery. 
Figure 52. It is usually built so that its longer dimension 
is east and west. The room is generally 24x54 or 64 feet on 
the ground and 9 feet to the rafters, while the roof is com- 
paratively low. The framework is made of heavy timbers, 
put together in the usual manner that low and strong build- 
ings are constructed. 
The foundations are always made very strong, and consist 
either of stone columns or boxes of concrete. 
Hardwood floors of 2x10 or 12 inch oak plank are the rule. 
The rafters are usually formed into trusses which are made 
of 8x8 inch pine timber, and are placed from eight to ten feet 
apart. These trussed rafters hold the line shaft for the mill 
machinery and are purposely made very strong, as the strain 
upon them is severe. Roof timbers are placed and the roofing 
put on in the usual way. 
Doors are placed at both ends of the jig room, besides which 
there are doors leading into the other rooms of the mill. Win- 
dows are located so as to give the largest amount of light pos- 
sible. ‘They are usually placed quite high up on the sides of 
the building, in order to be above the machinery. 
Stairs lead from the floor of the jig to the crusher room, 
and steps and walks are arranged so as to give access to the 
highest as well as lowest parts of the mill and around the 
various machines. 
ENGINE AND BoiLtER Rooms.—These rooms, usually adja- 
cent to the jig room, are, as arule, built on the south side of 
the mill building proper. They usually occupy an addition 
or ell to the main building, placed as indicated above. This 
portion of the building is usually divided into two parts, the 
larger of which is the engine, the smaller the boiler room and 
coal bunkers or bins. In the engine room are located the en- 
gine, boiler, pump, heater, air compressor, and dynamo, pro- 
vided all these machines are employed in the mill and mine. 
