' They first endeavoured to ascertain, from
competent persons, the effect of the atmosphere alone in
deteriorating a well-constructed road. The next step was, to
determine the proportion in which the road was injured, by the
effect of the horses' feet compared with that of the wheels. Mr
Macneill, the superintendent, under Mr Telford, of the Holyhead
roads, was examined, and proposed to estimate the relative
injury, from the comparative quantities of iron worn off from the
shoes of the horses, and from the tire of the wheels. From the
data he possessed, respecting the consumption of iron for the
tire of the wheels, and for the shoes of the horses, of one of
the Birmingham day-coaches, he estimated the wear and tear of
roads, arising from the feet of the horses, to be three times as
great as that arising from the wheels. Supposing repairs
amounting to a hundred pounds to be required on a road travelled
over by a fast coach at the rate of ten miles an hour, and the
same amount of injury to occur on another road, used only by
waggons, moving at the rate of three miles an hour, Mr Macneill
divides the injuries in the following proportions:
Injuries arising from; Fast coach; Heavy waggon
Atmospheric changes 20 20
Wheels 20 35.
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