- Mar 30, 2011
I'm not sure.This one (their statement of the origin of track gauge comes from the width of a horse's butt) comes up often with variations. Think wagon wheels set on 5 feet centers with 4 inch wide iron treads. That leaves you 4 feet 8 inches. Put a vertical flange on the inside of the wheel Make the rails an additional 1/2 inch further apart so that you have a little play, and guess what! You get 4 feet 8 1/2 inches. I suspect this to be the most likely origin.
George Stephenson built the Stockton & Darlington to this gauge because this was the gauge he was accustomed to from the colliery where he had previously been employed and where he first experimented with building locomotives. At the time every colliery had its own gauge. Had Stephenson been employed elsewhere he would probably have adopted whatever gauge they had there. Trevithick for example built to a narrower gauge for much the same reason. If you want to dig into the reason any particular gauge was used in any place, there is typically no record, and in all likelihood the initial decision was taken on the fly by whatever local blacksmith had been asked to install the first tracks and supply the first coal cars. Subsequent generations just copied that.
There have been horse- drawn colliery and quarry lines that used gauges significantly narrower than 4'8 1/2". This wasn't a problem for the horses. Today we have a concept of a horse that is a thoroughbred and large and heavy animal with a fiery temprament and that will gallop at high speeds and effortlessly jump over hedges. Back in the day the cavalry may have had such horses and a couple of rich folks may have used them for hunting and racing. The animals that went into the mines were often more ponies and mules and small mangy horses as well as various indeterminate cross-breeds that could be bought and maintained on a low budget. There were mining operations that used what they called horses on gauges as small as 2 foot.
Anyway, it's not the width of a horse's butt that is in any way relevant for the track gauge, but the distance between its hoof prints, which is typically a fair bit smaller than the width of the butt.