I was a little interested by the fact that the two construction teams at this facility were still working here at this time of year. We're now in early fall, and usually by now, the reservoir would be drained, so they'd be working there again. However, after investigating the matter, I found that the new aqueduct is actually about three-quarters done, and that has resulted in not only a larger amount of water reaching the reservoir in spring, but a larger amount of water year round, meaning the reservoir is also draining slower. They expect that around winter time, it will be fully drained, and they can go expand and do maintenance on it.

Honestly, as long as we have a good source of stone, at this point we don't really need the reservoir to be expanded much more. It can already hold a significant amount of water, and helps smooth out the city's water supply significantly. The only time we might need to be concerned is if we experienced multiple strong hurricanes in a single season, over a short enough period of time that we couldn't safely drain it. If that happens, we'll probably be dealing with bigger issues, like mudslides or rockslides destroying the dam.

I also haven't done a checkup on the tunnel in quite a while, so I figured it'd be a good idea to do so. What I found was that the scouting tunnel had reached the midpoint almost two years ago, and they'd started work from the other side now. The expanded tunnel portion is getting close to reaching the midpoint as well. From what I can gather, the fort on the far side of the island, along with some of the buildings and inns over there, are being used as a staging area for digging the tunnel from that side, though I'm not sure what they're doing with the stone they're excavating over there. I'd hope that they're stockpiling it, so there will be an excess for construction of buildings on that side of the island once we're done.

I also found out that the dwarf who had access to their version of tectonic sense was among those who left the island last year, meaning we haven't had any scouting capabilities for new ore deposits for a while now. So, realistically, I should probably do that myself, as most of our ore refining and smelting is complete at this point. There is still some lead refining to make silver left to do, since that relies on cupels that we make from recycled fish bones, but other than that, our ores have all been turned into ingots.

----------------------------------------

I took a total of fifteen days checking the new portions of the tunnel for any anomalies in the stone with tectonic sense. The far side tunnel's construction is actually going much slower than the near side, since they don't have a medium sized mana crystal underground to assist them. However, they should soon be deep enough to install one, and since the widened tunnel on the other side is nearly complete, we'll probably just move the crystal from one side to the other.

The large part of my time was actually spent recharging mana on the far side of the island. I did notice one point of interest near the end of the near side tunnel at the center of the mountain, but it was nearly thirty-five feet diagonally down meaning we'd need to dedicate quite a bit of resources to reach it, and for all I can tell, it just seems to be a layer change, meaning spending that time could result in basically no returns. I'd rather wait until the tunnel is fully complete before dedicating anyone to that task. If, however, we end up low on metal in the near future, then it's at least something we could pursue.

One interesting aspect of the tunnel, and one I'm glad I prepared for, is the amount of water draining out of it. It's actually quite a lot. The partial tunnel is miles long, and quite a bit of it has slow dripping water. Over that total length, it comes out to quite a decent sized stream. I have some ideas for long term plans for the tunnel as a whole, which involve digging a sewer line under the tunnel and a rest area in the center of the mountain where travelers can stop.

A case of theft: this story is not rightfully on Amazon; if you spot it, report the violation.

With the pace that the tunnel is being built, I think the main tunnel will be finished at around the same time that the area within our main city's wall is starting to become filled enough that we would consider building another circle of walls. Instead, it might be good to adjust our primary construction focus to the far side of the island at that point, to distribute out population to make defense and overall use of our island easier.

We're also reaching a point of industrialization that it would probably be worth establishing a material science lab to start determining the real quality of certain construction materials over others. If, for instance, acid washed lightstone ends up being very easy to make and structurally stronger than the regular stone we've been working with, then we could, in theory, build taller buildings, increasing our population density, which would keep more of our land available for other projects.

----------------------------------------

After going on that brief vacation, I went back to the research base to start designing the cryogenics facility. The largest of the heat driven stirling engines can drive six of the large cryocoolers by my estimates. If I were to use hydrogen as the internal medium for the large stirling engine, it could probably drive even more of them. I'd actually prefer if we could use the Joule-Thomson effect to produce a continuous stream of liquid air, but we lack a lot of the necessary resources to make various components of the quality needed to exploit the effect.

So instead, I want to make a lot of the large cryocoolers in a hallway, where they can reject their heat to the atmosphere outside the hallway. That way, the efficiency of each individual cooler should increase as well, since the ambient temperature should drop within the cryogenics facility due to all the cooling. In fact, I wouldn't be surprised if operators in the facility end up needing protective leather to handle things in the facility.

One large cryocooler is capable of producing a bit over 100 gallons of liquid air in a year. Of that, there is about 1 gallon of liquid argon. Doing some quick mental math, if I want to have a giant mana crystal capable of surviving any mana storms in 10 years time, then we'd need around 25 large cryocoolers producing liquid air.

It's actually completely doable to make that. If I account for maintenance times, I think I should up the number to around 30 cryocoolers. That would mean we'd need five large stirling engines as the main power source for this building. That means we'd also be producing about ten gallons of cryogenic air a day, which still isn't anywhere near enough to do a continuous distillation, meaning we'll still be doing batch distillation. If we're doing batch distillation, we'll also need to make plenty of cryogenic storage tanks for handling all this fluid.

Some of it will be useful as part of extracting fluorite from the existing deposit, but we'll still have an excess of liquid nitrogen after that. The inert nature of nitrogen could be useful for a bunch of processes. As an inert gas, it could be used for storing other reactive chemicals we might make. If we end up being able to attempt the haber process, then we could also end up making ammonia, given we have a hydrogen source as well. There is also the option of using it for cooling in locations where building a cryogenic cooler isn't feasible, or only a small amount of cooling is necessary for a brief amount of time.

There will need to be a lot of other peripheral devices as well. First, I'll want fans to drive air over the hot ends of the cryocoolers and the cold ends of the power producing stirling engines. I also will need additional cryocoolers for storage tanks and a batch distillation tower. Realistically, we probably want more than one batch distillation tower, with a smaller one for processing the Argon. We'll also need a smaller system of desiccant and freezers to remove most of the water and some of the CO2 from the air before it enters the facility for condensing.

Overall, similar to the hydrogen facility, I think having a lot of the tanks underground will be a good idea. In the event of a failure, there is less risk to the environment. Though unlike with the hydrogen, we'll actually need a way to remove the liquid from the bottom, rather than only needing to pull it out from the top.