[xoxoxoBruce]

I wonder if that's a passenger compartment, or the cab of the engine?

Ah, it's a camel engine.

The Camelback was a design of steam locomotive developed in the late 19th century that could burn low-quality anthracite coal. Anthracite burns slowly with very little smoke, so railway engineer George Wootten created a large, wide firebox. This firebox was so tall it would block the view from the cab, so Wootten moved the driver's cab to a high position over the center of the boiler. This design of steam locomotive became known as "Camelback," "Center Cab," or "Mother Hubbard." It was very popular on the anthracite lines in the East, as it saved on fuel costs. But there were some problems. The first is that the fireman was more exposed to the elements. The second is that communication between the driver and fireman is more difficult. The third and most serious problem was that if the side rods were to break, they would destroy the cab and kill the driver, earning Camelbacks the nickname "Snappers." For this reason, Camelback engines were banned in 1918. One of them, Baltimore and Ohio 4-6-0 No. 305, is preserved in the B&O Railroad Museum.

Actually, it's a "Camel" locomotive, not a "Camelback". Camels had the cab atop the boiler, whereas Camelbacks straddled the boiler. The Camel was designed by Ross Winans, and the cab was placed atop the boiler to put more weight on the drivers, which helped when going over the Alleghenies. The Camelbacks were designed to accommodate the Wide Wooten Fireboxes, which necessitated putting the cab around the boiler. There is a Camelback at the museum- the CNJ #592. BTW, this might look strange, but it was very very effective.

So it was for inclines, but not the same type as the lenticular mountain climbers.