B&M/PAR Milepost Question

I'm not sure if this question properly belongs here, or in the current operations/Pan Am forum, but here goes:

The route followed by today's Freight Main Line jumps between multiple historic rights-of-way that were originally used by multiple B&M predecessors. These include (among others) the Stony Brook Railroad, the Fitchburg Railroad, the Vermont & Massachusetts, the Southern Vermont, the Boston, Hoosac Tunnel, & Western, etc. In most cases, each time the route shifts from one predecessor ROW to another, there's either a short or long mile since the original milepost locations weren't changed, but were simply renumbered based on the new origin point. I've been able to figure out the sources of most of these long/short miles (either a predecessor route change or a line relocation) based on the valuation maps, but there are a few that are a puzzle, and I'm hoping someone with more historic knowledge of the B&M can help fill in the gaps.

Specifically, I'm looking for the reason the distances between (current) MP 364, 365, 366, and 367 are (based on measurements along the tracks) are 7022' (364-365), 3379' (365-366), and 5438' (366-367). While those may average out to 5280', the milepost locations as shown on the valuation maps are definitely not anywhere close to 5280' apart...

Thanks.

There was the Birch Hill Dam mainline relocation in 1940. Royalston.

Where I'm looking is about 10 miles further west, in Orange.

Mebbe this clears up or causes more confusion, but a comparison between ETTs 10 (eff. Nov. 22, 1931) and 36 (eff. Nov. 14, 1941) shows mileages .01 or .02 less in 1941, 64.66 v. 64.65 for Gardner and 70.53 v. 70.51 for Baldwinville as examples. Royalston -- west end of the Birch Hill Dam relocation -- shows as 75.58 v. 75.33, reflecting the shorter routing. The .01 or .02 differences continue west. The difference at Johnsonville is more -- 174.12 v. 173.79, hinting at a relocation from possible Hoosic River or tributary flooding. Given the financial pressures of The Depression and the boiler-plate nature of ETT typesetting, it's strange that differences of .01 or .02 were measured, let alone documented.
As far as Orange, the 1941 mileage is 86.00. If the later mileage of 366.4 in both PAR ETT No. 3 (eff. June 15, 2014) and New England Railfan Timetable Guilford Rail System Timetable #1, {eff. Dec. 1, 2002) gets the -280 treatment, that comes out to 86.4, .4 miles west of the older location and west of the Water Street XNG. Guessing that relocation mighta been made as a convenient recrew/tie-down point for EBs.
The resolutions to these and so many other puzzlements are possibly in the B&MRRHS archives.

Interesting. The Orange depot is shown on the 1915 track chart I have as just east of Water St, at roughly 86.35. It's in the same place (without the depot buildings) on the 1980 track chart as well. 86.30 is shown in the 1911 ETT; 86.02 is listed in 1957. What we don't know is if the "miles from Boston" in the timetable is actual measured distance or if it's based on the number of mileposts (not the same thing, clearly). Most railroads tend not to remeasure and move mileposts, but use short or long miles instead. Clearly the B&M had a different practice, at least for a while.

I don't get the total upshot of the post. Did B&M relocate mileposts to allow for the line relocations? I know personally about the renumbering of mileposts for the Freight Mainline out on the west end and D&H. A good example is at Crescent. On the joint line between Crescent and Mechanicville, both railroads had their own mileposts. There is presently a short mile between MP 477-478. Gilford used the B&M milepost locations and repainted them for the mileage from Mattawamkeag, vs. the old mileage from Boston. At this location, Guilford simply just painted the next physical milepost for the consecutive number. The 477 milepost was a B&M milepost. Their mileages continued out what is now the Rotterdam Branch. The milepost at 478 is from the D&H series, so the location is not actually 5280' from the last milepost, on the former B&M series.

No, the B&M didn't move mileposts (as far as I can tell) when a line relocation happened.

The starting point of the question was the fact that the milepost locations in Orange between MP 364-367 vary considerably from being anything close to 5280' apart (7022' for the first mile, 3379' for the second mile, and 5438' for the third mile). I can't find any evidence on the valuation maps of the line having been moved from where it was originally laid out, and I'm trying to find out if anyone knows the reason for the odd milepost spacing.

I have a question on the topic being discussed. I'm familiar with the "wide track" arrangement of the two predecessor lines between Johnsonville, and the VT state line. I've run over parts of the former wide track, as for as Eagle Bridge. From railfanning trips, as well as satellite views, one line seemed to be more direct, while the other wandered around more between the tow points. Did B&N use long/short miles to have both lines add up to the same mileage, or did on track have an extra milepost? The thought came into my mind after thinking about running on the former CB&Q West Ottumwa Division. There are several wide track locations, but most had the same number of mileposts at the ends. There was one location in Albia, IA where one track went directly through town, but had a really steep hill. The other track had a gentler grade, but was a mile longer. The longer track had a milepost ex. 123A to make up for the extra mile. We used to claim the extra run mile for a few cents of extra pay, if we took the longer track.

The B&M being the B&M, some "flexibility" probably occurred. Two ETTs -- Fitchburg Div. No, 61, eff. Sept. 25, 1927 and system No. 36, eff. Nov. 14, 1943 -- were compared. Besides the Birch Hill Dam and other possible relocations, there was one other significant difference. The older ETT had the mainline as Boston to Rotterdam with Troy as the branch, and the more recent one had Boston to Troy as the main and Johnsonville to Rotterdam as the branch. Dunno, but since the system #10, eff. Nov. 22, 1931, also shows the EB main starting at Troy, this may have been one of the many Hannauer-era changes.
The Fitchburg #61 shows Pownal as 151.43 and Johnsonville as 174.12, a difference of 22.69 miles WB. EB, Johnsonville shows as 35.2 and Pownal as 59.02, a difference of 23.80, the difference of differences being 1.11.
The 1943 ETT shows Pownal as 151.19 and Johnsonville as 173.79, a difference of 22.60 WB. EB, Johnsonville shows as 16.28 and Pownal as 40.25, a difference of 23.93, the difference between the differences now being 1.37.
Mebbe there were ICC regs requiring resurveys. Dunno, but clearly distances for the different alinements wre surveyed and entered into the ETTs, even if the MPs stayed in place.
As always, the answers probably rest in the B&MRRHS archives.

As best as I can tell from looking at track charts (which include chaining distances), the B&M ended up splitting the difference using a combination of long and short miles. Looking at a 1957 track chart, going west from the MA/VT border, the lines are even when they split at North Pownal (MP 154). The westbound main has a 4200' mile (to bring things in sync with the eastbound main) just before reaching Hoosick Jct at MP 165 where the two tracks come together. They're even again up to Eagle Bridge, where the two tracks split again. This time when the tracks come together again at Johnsonville (MP 174) the westbound main has a 5700' long mile to bring things back to even.