What is this?

[Lamplighter]

The end goal is to determine the board feet of lumber in a given plot of land.
The timber cruiser stands at the center of a plot of trees,

The prism (wedge) gauge is probably easier to understand.
It basically is used to count the trees inside and outside a certain distance.

By looking thru the prism, and rotating 360 degrees,
the cruiser counts the number of trees inside (pic 2)
and outside (pic 3).
By measuring the diameter of the trees inside the plot,
the timber inventory (total number of board ft of the plot) can be calculated.
This "sample" from the center of the plot can represent a much larger area.

The width-steps of the other gauge (pic 1) select
for trees of a maximum given diameter.
The chain is used to fix the distance from the gauge to the eye.

Both of Glatt's tools above and the old gauge here show that our
forefathers were not dummies.