If I have it correct,
1. first there was a Genesee Valley canal, which was abandoned by the 1870s and the right of way was used for a RR around 1880. The RR did not exactly follow the canal ROW everywhere however. By 1900 is was part of the PRR
2. In the early 1900's, the Erie built the River Line, opening in 1910, with its big fill on the west side of what is now Route 19. The B&S and PRR had tunnels through the fill
3. In 1922, the PRR tunnel collapsed, and the PRR was re-routed eastwards to pass under the Erie trestle viaduct, just on the west side of 19, right near the west end of the trestle viaduct over the valley (east of the fill region).
If I am right so far, my questions are:
(a) Is the route of the PRR just north of Belfast, going through the fill, the original (~1880) RR route? (This refers to the straightline segment on the map Russ linked.) My guess is yes. Or was it re-routed from something else when the fill was built around 1910?
(b) Is the straightline segment the route of the original canal as well, or did the canal have that bend to the east which the later 1922 PRR re-route followed? I don't have any old canal maps.
Hope those questions make sense.
JS
And one more. Here is a Google streetview looking east from Route 19, at the piers for the old Erie River line trestle:
https://www.google.com/maps/@42.355227, ... 312!8i6656" onclick="window.open(this.href);return false;
So where is (or was) the really tall abutment in Russ's old pictures? Buried in the trees on the west side of Route 19, gone now entirely, or on the other end of the viaduct (east side of the valley), nd perhaps also gone?