MOTIVE POWER 183 



thing like a proper speed. For mills with rolls 12" x 16", 12 horse- 

 power for each mill is not too much to allow, especially if one 

 takes into account the invariable loss of power in gearing and 

 belting. Then, also, one must take into account the class of 

 rubber which is being manufactured. If one puts into the mills 

 old scrap or similar tough old rubber it immediately acts like a 

 brake on the mills, which demand several horse-power additional 

 to perform their task. For many reasons a good margin of horse- 

 power is strictly necessary. 



Of all motive powers, the cheapest, the simplest and the 

 best is a water-driven turbine, when an ample supply of water 

 power is always available. There are large factories driven by 

 such power both in Java and Sumatra. The cost of the tur- 

 bines is exceedingly low, and the chief outlay is usually incurred 

 in constructing the channel to convey the water from the river 

 to the turbine. No attendance is needed and the cost per h.p. 

 per hour is practically nil. Provided there is a sufficient supply 

 of water, all that is necessary is to secure a good fall from the 

 water-channel on to the turbine in order to develop a high 

 horse-power. The smaller the flow of water the greater must 

 be the descent of the water. The ordinary old-fashioned 

 water-wheels give a very low horse-power as compared with 

 turbines, as in their case only the weight of the water in the 

 buckets is transformed into power and not the velocity of 

 descent. 



