Lever movement of float changes tilt of mercury switch ( shown as SPST in electric circuit to turn ON water pump or open water valve if water line has pressure.
Lamp is where 5 gallon oil can is soldered air tight to make large float on top of water in cattle stock tank. The float raises up and down with water level.
The "T" of horizontal and vertical SPST is where pivot point of lever moves arm through wall. Wall is vertical line with ground at bottom.
The resistor and two sets of grounds makes a parallel movement as they attach to wall.
Mercury switch is tilted by lower set of grounds to automatically control filling cycle of stock tank.
