Mathematical and scientific ways of dividing things into sections.
Probably filmed at Pathe studios, London.
M/S of man examining empty shell of sausage roll, we see sections of mine, lighthouse, gun, carburettor, piston of motor and steam engine. A microtome cuts small sections and a woman looks under a microscope at mud from the Thames. Various shots of diagrams explaining how sections are cut mathematically and how curves and reflection direct light rays. Various diagrams show the different sections running through the earth.