I happened to find an old postcard at an 'antiques' store, with this photo of a unique locomotive.
This was a one-of-a-kind loco purpose-built specifically for service on the short steep grade. It was successful enough to be used for 30 years. Ironically, construction of a lower-grade line was started in 1852, but never completed.
I'm wondering if anyone can offer additional technical information about this unusual locomotive. The rigid wheelbase is unusually long, but apparently the incline was fairly straight. Why the big space between the third and fourth sets of drivers? I'm wondering if there was some provision for the last two axles to rotate, as was done on certain early European locos built for mountain service.
The following website has some interesting info: