TRANSPORT. 313 



ton, bringing the freight to £60 12s. would be 

 necessary. 



The present charge per ton from Chinde to Tan- 

 ganyika is, I believe, £143 per ton, of which, prob- 

 ably, fully £100 is allotted to the Stevenson Eoad. 

 The margin, therefore, between £60 and £100 is 

 sufficient for a railway.* 



It may therefore be assumed that providing 500 

 tons can be carried either method would at present 



* It is a nice mathematical problem to see exactly where 

 the railway prevails over the bullock waggon. It is obvious 

 that — - 



1. The total freight by rail must be less than that by 

 waggon. 



The total freight consists of charge for interest on capital 

 (c b and c r ) and charge for working expenses both per ton (w b 

 and w r ) in each case. 



2. The charge for interest on capital per ton multiplied by 

 the number of tons (n) must equal the total interest (i b and i r ) 

 on the capital in each case. 



.-. c b + w b = c r + w r (w b and w r constants) 

 nc b = i b (a constant) 

 nc r = i r (a constant) 



In the example above : — 



c b + £9 = c r + £3 

 nc b = £2,420 

 nc r = £28,800 



From which it follows that the number of tons is 4,396, which 

 would require a charge of £6 lis., or total freight of £9 lis. by 

 rail, and a charge of lis. per ton with the same freight by 

 waggon. In practice it should be built long before this point 

 as the lower freight rapidly increases the amount of tons 

 carried. 



