TAPPING-KNIVES AND UTENSILS 181 



which are very large, and where ground is left fallow for a 

 number of years after cultivation. There the convenience of 

 having a railway system which can be laid down or lifted up 

 by a few coolies is much appreciated. 



The mono-rail system consists of a single rail along which 

 light cars are run. The cars are balanced by coolies running 

 alongside, and guard wheels on which they may rest prevent 

 them from overturning. The first cost for the rails is some- 

 what cheaper, but is somewhat discounted by the necessity for 

 special cars, and, unless loads are very light, by the difficulty 

 in balancing. The system, however, is in use in many lands 

 and must be found to have advantages. 



In hilly country, or where there are rivers or ravines 

 to be crossed, wire-rope carriers are very useful, simple to 

 work, and by no means high in cost. These are employed 

 for a great variety of purposes in nearly every country in 

 the world. For the conveyance of latex from hillsides to fac- 

 tories there is nothing equally as good. Working expenses 

 are practically nil. 



