PRESIDENTIAL ADDRESS. 17 
earthworks and waterways may be reduced by an average 
of £8,000 per mile. We will assume that the line is 20 
miles long, and that one quarter of it consists of sharp 
curves, that these curves are check railed, and that in spite 
of this the rails have to be renewed every four years, which 
with properly designed engines, I might say in parenthesis, 
is making the case worse than it really is. The extra 
checking of the curves might possibly cost £500 per mile, 
and a quarter of the length being thus laid, the average on 
the whole length will be £125 per mile, that is to say, the 
average saving of cost of earthworks and waterways on the 
whole line will be £8,000 per mile less £125, that is to say, 
£7,875 per mile, or for 20 miles £157,500, the interest on 
which at 47>.= £6,300 per annum, which is the annual sav- 
jug due to cheaper construction. Against this we have 
permanent way rails 5 miles to be renewed every four 
years, say £5,000 = £1,000 per annum. Thus the net 
saving is £5,300 per annum, which sum would be vastly in 
excess of what is required to cover the cost of turning up 
and renewing locomotive tyres, etc. 
Wear of rails is more or less proportioned to resistance 
to traction, but is increased in places by brake action. 
Observations show that it is not proportioned to curvature, 
as the sharper curves wear more in proportion than flatter 
ones, that is at least on main lines. It is largely a question 
of wheel base, and given a certain wheel base there must be 
a limit to the curvature round which a vehicle will travel. 
As sharper curves are used it is clear that resistance must 
increase out of all proportion, when nearing the limit. 
Probably when not near the limit, resistance and wear may 
be approximately proportional to curvature. Wellington 
has investigated the subject at great length, but it cannot 
be doubted that in a country like this, where the conditions 
do not correspond with those in the United States of 
America and where other types of locomotives are used, 
B—May 6, 1908. 
