A Weather Glass is a small open barometer filled with water; you use water with food coloring, so you can make the water any color you please; open on one end of an otherwise sealed globe. It comes with a long narrow tube to be used to inject the water into the globe after fishing the tube in through the spout. There are other ways to fill it.
The objective is to create a vacuum above the water in the globe. Filled correctly, having accomplished the requisite vacuum, with water level about mid-globe, the Barometric or Atmospheric Pressure exerts force on the water in the spout, moving it up or down.
The conventional Barometer at the upper left, and lower right, are the same, just different days, different photographic techniques, look at the reading on the upper left, very high. The picture I took of the Weather Glass that day is too dark to show, but the water is near the bottom of the spout where it enters the globe.
The two lower conventional Barometers and the Weather Glass photos were taken at the same time. Very low pressure on the conventional Barometers, and correspondingly high water column.
An earlier model of the Weather Glass we had didn’t have the bowl at the top of the spout. Predictably, one day the pressure was so low that some water must have poured out, the base had food coloring on it.
There’s a wall hanging model of the Weather Glass, I think it comes with a wood backing plate. It doesn’t have the collection bowl at the top of the spout like ours does, it’s a little more dramatic. As near as I can tell, it would lose water out of the slender spout, like they all can, but the water drips down the elongated glass, off a glass sphere at the bottom of the Weather Glass, and into a small cup mounted on the wood backing plate. Weather in action.
I like my barometers, but the Weather Glass is on a shelf at the bottom of the stairs. Every trip from the 2nd to 1st floor it’s right in front of me, I see it, and if I see a high water level in the spout, I look at the Barometers and check the weather.
These Weather Glass Barometers are more practical than one would think.