At one angle on glass, tan θB = n, the reflected beam is fully s-polarized and the p-component goes into the glass. Brewster published that in 1815, the same decade as the Kaleidoscope.
Photographers still use it: a polarizer on the lens can kill glare off water or a window because that glare is already polarized. On this bench the analyzer eats the p-reflection and leaves the s. Tilt the glass and the null walks.