Thanks for the photograph. That locomotive is quite small even by 1870's 3 foot gauge standards. Do you know what type of rail the road was originally laid with? That little engine could've run on iron rails in the 25 pound per yard range, or steel rails even lighter, although that doesn't necessarily mean the rails were so light--only that they could have been. Certainly the rails pictured are not large.
National (aka Dawson & Bailey) did not survive the economic malaise of the 1870's. It was history by the end of the decade. Bad time to try to start a company.