CrRANE.| Prospecting, Mining and Milling Machinery. 241 
In both forms of elevators, the belt is tightened by a lever 
arrangement connected with the bearings of the lower pulley 
in the upper part of the boot. 
The box in which the elevated material is thrown, and 
which conducts it to the launder through which it is dis- 
charged, should project into the elevator about six inches. 
This is to make sure that all of the elevated material is caught 
and conducted to the proper point. 
The buckets are made of sheet iron, cut to pattern, formed 
and riveted as shown in figure 43. The finished buckets are 
fastened to the main elevator belt by means of small flat- 
headed bolts, between which and the elevator belt is inserted 
another piece of rubber belting, which takes up the wear 
that would result if the buckets came in direct contact 
with it. 
DERRICKS OR HEAD FRAMES. 
The primary object of a derrick is to furnish a support 
for the sheave over which the hoisting cable or rope passes. 
It also, when covered, furnishes protection from the weather 
to the operators. 
Formerly the derrick was made of single lengths of timber, 
forming a truncated quadrangular pyramid, with the lower 
base twelve feet, and the upper base from four to six feet 
square. A framework was placed at the top and bottom to 
maintain the shape of the derrick. The corner timbers were 
then braced by boards nailed diagonally across on the four 
sides. The platform was the ground, with an occasional 
rough plank landing place about the shaft mouth. The 
track had to be raised constantly as the dump increased in 
height. This was the old method of erecting derricks. 
A new departure in derrick building was inaugurated in 
1885 by Mr. Huff. The new form of derrick suggested and 
adopted by Mr. Huff does not differ essentially from the for- 
mer plan except in one particular—. e., in height and posi- 
tion of platform. 
Posts are set in an upright position at the corners of a 
square or rectangular space enclosing the shaft mouth, upon 
which is built a platform, all being securely braced. The 
