Heh. If there’s any chance of 19 feet of rain falling in the comfortable emptying interval for your rain gauge, I don’t think there’s much point building the rain gauge, as the house will be washed away.
I’m going to go with KCB615 on this one. Why else would there be a notch cut out on the roof? Nearly every municipality has code for clearance of the outlet of the chimney, i.e. must be three feet higher than anything within ten feet. Some have code for total chimney height.
It looks like the siding has been cut out. With the eve cut out too, I’m betting they put in a wood stove, and they are building a chimney chase.
And My guess is the same as the raindog. I think it may well be one post for pump jacks. Now I’ve never seen just one used before, maybe the other has been taken away. Or there may be a system I haven’t seen that allows you to use just one.
Or maybe the translucent tube is like the one on the side of coffee urns. It shows the level of the liquid inside–so if the house is ever flooded, nobody will have to open the door to see how deep the water is inside… 
Seriously,vetbridge, you just gotta investigate this one for us…
Call the real estate agency, call the owners, call the county building inspector…maybe even call out the national guard…But don’t leave us stranded! Do it for uncle Cecil …It’s just too wonderful a curiosity to remain ignorant of.
Maybe it’s a float measuring the level of some underground tank. Lord help 'em if it’s for the septic.
OK, I will do whatever is necessary to unravel this mystery.
I dunno. The ruler looks more like a semi-permanent installation (although it’s hard to tell because the picture is indistinct in the important details). The thing is, if you were building a chimney chase, would you really bother with constructing a nineteen foot ruler when a tape measure works so well? And those brackets holding the ruler to the house would make it difficult to construct anything in the ruler’s place.
What about on the far side of the house? To the right of the ruler, there looks to be another protruberance. It could just be a vent pipe, but is there a chance that there’s another ruler on the far side of the house?
Is there a bell at the top and a sledgehammer near the base?
That’s just it. It’s not a ‘ruler’. I think it’s a pump jack pole. The foot markings would only give the operator a general idea how high he is.
Is it the scar where a chimney has been removed? That would explain the notch in the roof.
Mangetout that is the funniest thing I have read in my life!!! 
(or I could be having a really bad day and it made me laugh when I needed it. Works both ways I guess)
As for the OP, I called a friend of mine who does roofs and chimneys. The only thing he could come up with was maybe the guy left his tape measure at home and with the price of gasoline it was just cheaper to build a really big ruler than to drive home.
Can you take a closer picture?
Because if the top of the ruler says “14 kinds of gradation in a fire place diagram” I think we have a winner.
“Pump jack pole”, while vaguely provocative, simply cannot be the answer.
It’s too boring.
They’re planning ahead for the 1,000-year flood level.
I’d say snow.
If it’s a thermometer, please inform them that they have yet to beat the world record proudly held by my home state:
Baker, California has the world’s largest thermometer
134-ft.-tall, a height chosen because of the record high temperature in the US, in Death Valley, 134°Fahrenheit in 1913. 33 tons of steel and almost 5000 lamps went into the construction of this Wonder of the World!
Something’s got to keep the pole vault crossbar in the air, right. One more upright and you’re set!
There is no way this is part of scaffold, or a pump jack. THEY CUT A HOLE IN THE ROOF AND THE SIDING! Looks pretty frickin’ permanent to me. Interesting enough, it looks like they wrapped the fascia around the notch in the roof, yet let the siding be bare in that spot.
You wouldn’t put pumpjack colums up against the house–at least not the ones I’ve seen and used. They usually stand off the house with braces that hold 'em vertical.
The obvious notch, and lack of siding going vertically up tells me that there was at one point a fireplace on the side of the house or they’re building one. That ‘ruler’ thing doesn’t appear to be fastened, does it?
No telling what it is until we get a closer picture.
Tripler
Hey vetbridge, you should dress up like Bill Murray in Caddyshack and sneak up for a better picture.
Yeah, chimney was Bossman’s opinion, too.