242 University Geological Survey of Kansas. 
platform generally stands from 8 to 14 even up to 30 feet 
above the ground, upon which is built the derrick proper, in 
a similar manner to that employed in the first method of 
building derricks. Plates XXIX and XXXIV. 
In most cases two cross timbers are fastened to the top 
frame about a foot apart, to which, by various methods of 
attachment, is fastened the sheave. Occasionally the sheave 
is fastened to a single timber, which can be moved back and 
forth on the two supporting timbers so that the bucket may 
be made to occupy the center or any point in the shaft that 
is desired. 
A tramway is built from one side of the platform, extend- 
ing far enough away so that no rock from the dump pile will 
roll back into the shaft mouth. After the mine has been de- 
veloped, the same tramway may be employed as a roadway 
to the separating screen, in hand jigging, or to the mill. 
Figure 37 shows a typical form of. derrick, with steam hoist 
and parallel bars, screen or grizzlies for separating the mine 
run dirt preceding hand jigging. The tramway, A, screen, 
B, and derrick base, C, together with the top, D, are shown 
in the cut. 
The object of this style of head frame is twofold, namely, 
to facilitate the handling of wastes and to elevate the landing 
platform to such a height that ore can be transferred by tram- 
way directly to the floor of the crusher room. 
As the hoist is usually placed upon the landing platform, it 
stands well within the base of the derrick proper, and as all 
of the four posts of the derrick are given an equal batter, the 
sheave being within the geometrical center of the top frame, 
supported by the posts, an exceptionally strong and stable 
frame results, and is admirably adapted to the work in hand. 
When the shafts are feeders to mills the derricks are built 
as part of the mill building, if close enough; in any case, the 
derrick platform must be as high as the crusher room floor. 
In many instances, the platform supporting timbers are from 
twenty to thirty feet long, and if the shaft is at a distance 
from the mill, the tramway connecting the two will of neces- 
sity be of the same height or higher than the crusher room 
floor. Plate XXXIV. 
