AERIAL TRAMWAYS 



225 



at the base of the grade, as shown in Fig. 61. Automatic trips 

 are placed on the main cable at the loading and unloading points. 

 The snubbing hne which passes through a 2-sheave trolley has a 

 ball near the free end which engages a catch in the trolley and 

 serves to hold the load in position, and to trip it at the lower end. 

 Power for returning the trolley to the head of the tram is fur- 

 nished by a drum on a yarding engine at the head of the slope. 

 A cable is fastened near the ends of a log that is to be transported. 

 A hook on the end of the snubbing hne is then caught in a ring 

 midway between the ends of the cable and the log is hoisted into 

 the air. When the ball on the snubbing line strikes the catch 



• Adapted from The Timbermaii. 



Fig. 61. — A Single-cable Aerial Tramway in use in the Pacific Coast 

 Forests. 



in the trolley, the latter is freed from the stop at the head tree 

 and with its load passes down the main cable by gravity, the 

 speed being controlled by the yarding engine. On reaching the 

 lower end of the cable the trolley is automatically tripped and 

 the log lowered onto a skidway along a railroad. Poles 100 feet 

 long, 27 inches in diameter at the butt and i foot in diameter at 

 the top have been handled with ease. The average time re- 

 quired to traverse the distance from the head to the foot of the 

 tramway is one and one-quarter minutes. 



Another type of single-cable tramway has recently been 

 patented. The chief features are a stationary track cable with 

 intermediate supports, a continuous traction cable, a secondary 



