246 DISCUSSION ON 
cross the line wherever there was a slight fall. On the Nyngan 
to Cobar line a very considerable portion was originally made as 
a surface line, but the first rains clearly showed that if left in 
that form, the expense of keeping the line open for traffic would 
be almost equal to remaking, every time there was rain, with a 
more than probable stoppage of the traffic and an element of 
danger as well, it was consequently deemed necessary to make 
the line in accordance with the views just enunciated. In hilly 
country of course no rough estimate of the cost could be given 
that would at all serve any good purpose, it depended first on the 
nature of the country, that is in its physical and geological 
characters, second on the curves and gradients that were to be 
adopted. A light line must necessarily have sharp curves and 
steep gradients, otherwise the only saving in first cost that could 
be made was by reducing the width of the cuttings, and from 
previous experience this small saving could not be recommended. 
The next item of importance was waterways; of whatever kind 
of material they were made they could not be restricted as to 
size, they must be large enough to carry off the heaviest rainfall, 
and the material must depend toa very large extent on the means 
of renewal when required without interfering with the traffic, 
thus in shallow banks timber might be used with safety, but when 
the earth-works were heavy or there were large streams or rivers 
to cross, concrete or steel must be used, and as these latter were 
comparatively everlasting, the question must be considered 
whether the light line was likely to become of sufficient impor- 
tance to require heavy rolling stock. The bridges also should be 
designed either of the required strength or in such manner that 
they could be strengthened when necessary. He assumed that 
trains over light lines would not be run at great speed and in 
daylight as much as possible, so that fencing to a very great extent 
might be dispensed with, and as in the case of the Nyngan to 
Cobar line at the boundaries of property cattle stops which would 
not allow even a rabbit to pass, could be made across the line. 
The design of the permanent way must be guided by the description 
