The Oregon Pony was the first steam locomotive in Oregon and was used on portage railroads in the Columbia River Gorge. It is now preserved on display in Cascade Locks. I don't know of any articles on it. It is a geared locomotive. The pistons link to a shaft under the end of the boiler with a toothed gear on it. That gear turns a gear on the axle under the boiler, turning the wheels. The other set of wheels is turned by the siderods. There are a few closeup pictures of the running gear at
http://www.brian894x4.com/Steamlocomotives.html. I don't know what the inside of the boiler looks like, but based on rivet locations and with the exhaust being above the firebox, which would seem to be necessary due to the location of the cylinders, there's probably a draft stop between the firebox and exhaust, forming a small smokebox, and two sets of tubes, and the hot air has to travel the length of the boiler twice, once in each direction.
