The glass balls has reminded me about the barometer and the box for it have been delivered, so it's basically just making the last stuff by myself and hanging it up, and we might as well take a small break from building other things. The box is just a 100cm long box, about 8cm wide and deep, and without a lid as the open top will be against the wall once hanging. At one end, the 'bottom' of the last 18cm is missing and when hanged, the bottom becomes the front, and that is where the scale at the top will be. I score, cut and smooth a pane of glass so it can be lowered into the slots to protect everything, and attach mounts at the top and bottom. The glass tube inside will have plenty of mercury in it, so it needs to be stable, durable and hard for the curious to mess with.

The glass tube have already been finished and cut, and a slightly thicker to be the bottom container have also been finished, so it's mostly to shape and make mounts and brackets in wood and brass to hold everything in place without putting too much pressure on the glass and the idea is to have some soft fabric wrapped around the glass at the attachment points. Then I add the wood plate that will be the back of the display area with the scale. Jane have decorated the paper for the back, and I glue it on. The paper have a rising millimeter scale from 680 mm to 810 mm to read the mercury level against and I've included classic texts going from 'very dry', followed by 'fair', then 'unstable', 'rain or wind' and finally 'stormy'. Since I started thinking about making a mercury barometer, I've switch my smart watch to show mmhg scale to learn what to expect, i.e. millimeters of mercury. I had not expected Jane to find a picture in one of my tablets folders, showing a classic weather station with several dials. She must have been spending a lot of time looking though that.

The useful thing when it comes to a barometer is not what pressure there is now, but changes in atmospheric pressure over time and the rate of change. So I take one of my longer threaded brass rods and screw on and solder a fancy top to make it easy for fingers to rotate the rod. I drill a hole in the end of the box that will be the top, so the rod go parallel about 2 cm to the right of the glass tube. A small piece of wood is attached to the other end to stabilize the rod and a hole is made so that the threaded rod can be pinned in place and not be pulled up. A simple small brass arrow is made which is given a threaded hole and it cannot rotate since it will slide on the glass tubes sides. The whole idea is that you screw the top until the brass arrow has climbed up or down until and is pointing at the level of mercury in the tube. Then after a few hours you can see if the mercury has moved up or down. The difference and how quickly it happened gives an indication of where the weather is heading. My smart watch's default storm warning occurs at 3 mmhg fall in 3 hours, and many times I've received three or even four warnings in half a day. I kind of wish I had a smart watch like this while out hiking in my previous life, as that would have been nice to have. Not that it would have done a huge difference in some situations as I just had to keep on walking to get to a hut, better shelter location or my car.

Iselin has of course been involved in the entire construction, but she isn't the only one, and generally words spread fast in the household when I'm working on certain projects and Jane tend to give hints when she know, but I've told it will be a way to predict weather changes and prove that the atmosphere has weight. Everything is mounted and very carefully the glass tube have been filled with mercury. The hole box is angled upside down, and very carefully I fill the primary tube with mercury, and install it in the box with the secondary tube on top, and I plug that. The box isn't heavy, but cumbersome, and Iselin gladly help me carry it upside down to the great hall.

I ask everyone gathered to predict what will happen when I turn everything so the long tube full of mercury is turned the other side up. The answers are everything from overflow, just filling the lower tube because there is enough room, or it won't fall out at all as it's stuck in the tube. It's kind of depressing that Jane doesn't know the answer - even after looking at that damn picture - but I should have guessed it. I've already written down my answer which is that it will flow out but level out at around 730-760mm high mercury column as I am unsure of today's air pressure and exactly how much room there will be in the outer tube. I've tried to check that my smart watch seems to be correct by standing at waters edge in the harbour when it was a clear day, but this is also something like 25-30 meters above sea level.

My answer is correct and there are very surprised faces on most people.This is also a good lesson in physics. Not least what is in the empty space above the mercury at the end of the tube. They understand that nothing could get in there, but the problem is that there isn't anything they can see either. And if I lean the barometer it fills completely up, proving there isn't air there. Vacuum is a new concept. Finally I add a tiny bit more mercury so the level match my smart watch and reality.

After we've hung up the barometer by the inside thermometer and the slate board for the temperatures of the outside thermometer, I explain what the barometer does and how it should be taken care of, and task the guards with adjusting the arrow every morning, noon and evening and keeping an eye on whether it starts to rise or fall halfway between those times and how much. Basically the arrow will be adjusted every 6 hours, and checked every three hours or so.

It feels like it's time to make a wind and rain gauge as well so this mansion have a 'complete' weather station to start collecting data. In the future I will set up weather stations on all my larger properties, and hopefully have someone who can collect all the data there, and those places that have radio will send updates, but otherwise just store and compile and create books for all the data. I would really want to have a weather station in many directions around these islands, but those places need radios too, and to the west there is Skagerrak and the North sea. In the future, hopefully I can get wealthy people to collect weather data and give it to the Academy so that it can be stored for the future. I believe that what's happened in European Midgård history. Meteorology, just like botany, has historically been cutting edge science. Admittedly it still is, just in another way.

A rain gauge is easy. Just a suitable glass container with a wider upper funnel to catch more rain and a scale on the side. I can use glass to make it easier to read without pouring the rain water into something else, but the funnel does not have to be glass and will be brass. I can build that and a mount for it in an hour or so. It is also easy to make a weather vane for wind direction, and the best location on the mansion is probably the south tip of the pavilion roof. It's the freest and highest place, where it can still be easily read by just looking out the window.

I should start making a proper weather book to collect and store data, and I get several volunteers, but the guards are here and many, and someone of the guards or staff will always be available even as we go on trips etc, so I ask the guards to write down both the data and how the days weather have been every evening. I don't care who does it, but it should be very readable by everyone and data will be marked in columns for 0600, 1200, 1800 and 0000 if someone is awake, as well as a small field for notes, so it's easier to interpret and follow day by day. I'll arrange it in the next few days so that weather data can begin to be collected before new year.

I should honestly start writing dates and such from Academy year 1 and count up. I won't force that year count to be used by others, but it can provide a consistent account that others yearly counts can be used against, regardless of who is king, etc. Honestly, there should be other calendars in use already in other parts of the world, but this have a decent chance to eventually become the de facto way to count years here in the north.