Monadnock - Ever notice that curious marker on the summit?

[Papa Bear]

Most of us have climbed Monadnock at least once, and some have climbed it many times over the years. It has beautiful views in all 4 seasons, but unfortunately the secret is out and gazillions of others also like to enjoy the summit, sometimes just when you want some solitude.

But this is not about the crowds: if you ever happened to look down at the summit, you probably noticed a disk, aka "The Monadnock Benchmark". This is a USGS disk set in 1931, But just about 1 foot to the northeast of this disk is a curious thing: three drill holes inside a triangle in the rock, with 5 lines radiating from the central drill hole. Sort of like some Mayan symbol or maybe like some of those lines in corn fields caused by space aliens.

This is actually a triangulation station established in 1860 by the US Coast Survey (predecessor to the Coast and Geodetic Survey) as part of the major survey of the east coast done in the mid 19th century. Incidentally, it's the center hole (with holes on each side, one with an iron bolt) that is the station.

Here's a photo showing the drill hole marker and the disk:


(click for larger image)

This shows the disk on the right and the drill-holes-in-triangle-with-5 lines on the left.

I have always been curious as to what was the story on the 5 lines. It's not explained on the data sheet for this mark that is published by the government (Here).

BTW, traditionalists might be interested in knowing that the government has switched almost entirely to GPS based surveys (I know, that's cheating, I think if you don't use a theodolite and heliotrope, you're missing the true experience ). This station was surveyed with GPS recently and now this 1860 marker's location is known to a little over 1 cm accuracy.

But I digress, this is about the 5 radiating lines. I've seen a number of historic survey markers which were drill holes (or sometimes small copper bolts) inside of chiseled triangles, but never one with lines radiating out from the hole like this.

Well, with a little research and a eureka moment, I figured it out. I put a report on the subject on the Benchmark Hunting Forum I belong to here: my thread on Monadnock on the Benchmark Hunting Forum

Read it, and next time you're on Monadnock, look down and you'll see the curious marker and now you'll know why it's the way it is.

So what's with those 2 extra drill holes - you got me!

 

[BobC]

Fascinating bit of research here - nice work!

 

[Roxi]

Way cool, Papa Bear! Thanks for the info. I'll be looking at those lines a little differently next time I'm up there. Thanks for investigating and sharing what you found out.

 

[RoySwkr]

Fun to have good photos so you can find stuff after you get home.

Are you sure you didn't catch that marker on Trask

 

[Jason Berard]

I wonder if Pink Floyd ever climbed Monadnock.....cover art from Dark side of the Moon anyone?

Nice report PB. I love looking at that stuff...is there a good resource for learning about the history of the surveys that would keep someone with a casual interest like me engaged?

 

[Jay H]

Not that I am familiar with old time surveying, but didn't they also anchor poles and markers down with cables and use that for precise locations? Could those lines be anchor points for the cables????

Just a wild guess anyway...

I haven't climbed that peak but will try to remember to check it out when I do...

Jay

 

[Papa Bear]

Not that I am familiar with old time surveying, but didn't they also anchor poles and markers down with cables and use that for precise locations? Could those lines be anchor points for the cables????

Just a wild guess anyway...

I haven't climbed that peak but will try to remember to check it out when I do...

Jay

They did have poles which were used to site from other stations. Sometimes there would be a light on top (easier to do the measuring at night) and sometimes various flags, etc. It's pretty hard to see a small object at long distances. Those lines from Monadnock were between around 50 km (~ 31 miles, to Wachusett) to around 100 km long (~ 62 miles, to Bald Hill). Of course the haze was probably less in the 19th century.

Guy lines were used, and sometimes you can see eye bolts in a triangle around a station.

But the lines around this marker are so short (2-3 inches ?) and so close in, that it's hard to imagine using them for anything other than gross pointers to the other stations. The fact that they align so well is pretty remarkable.

There are lots of holes on that summit, and I woudn't be surprised if all five lines had a corresponding hole. You could probably find some of them if you had someone sight along a line and someone else walk out and try to spot a hole aligned to the line. As it was, the first two reference marks (which were holes with a chiseled square around them and an arrow pointing to the station) are on line to two of the stations. If you go up there you can probably spot these old reference marks (there are 5 of them) plus 3 "modern" reference marks (disks set in the 1930s).

But I would doubt there would be anything pointing to a guy line anchor hole, since those would have no geodetic significance.

This log (Monadnock Log), which I wrote after my July visit, reports and has photos of all the documented marks there (besides the station, there are 10 other documented markers of one sort or another), but there are probably lots of other undocumented stuff, together with an immense amount of graffiti chiseled on the rock.

Here's a diagram of what's there:

Besides being one of the most frequently climbed mountains in the world, it's also one or the most highly benchmarked.

 

[pks4000]

Thanks Papa Bear

New meaning to an old summit thanks for the info

 

[gooly]

I wonder if Pink Floyd ever climbed Monadnock.....cover art from Dark side of the Moon anyone?

that's the first thing i thought when i saw this thread as well...