Mirror Optics, Geometry, and Hydraulic Devices
Convex and concave mirrors, area-preserving figure transformations, Hero's fountain and covered water tanks.
Two mounted sheets combine geometry, optics and mechanical devices. The upper sheet poses figure-transformation problems — reshaping a table three braccia by one into four by three-quarters, and enlarging or reducing a square or circle by an equal amount — and, within a large triangle, states that a convex mirror can show nothing at full size while a concave mirror can only enlarge, up to the pyramid of rays it forms; an arithmetical sum accompanies them. The lower sheet is crowded with pneumatic and hydraulic apparatus, including a Hero's fountain labelled with lead, air, water and valves, an air-test instrument (anemometer), and covered vats together with a float-in-bucket mechanism.
On this page
Convex and concave mirrors (81, b)
Within the large triangle Leonardo notes that a convex mirror cannot show any object at its true size, only a smaller image at the little part that touches it, whereas a concave mirror can only show a thing enlarged, up to the pyramid of rays composed by it.
Reshaping a table while keeping its area
A method to make a table three braccia long and one wide become four long and three-quarters wide — an area-preserving transformation of the rectangle.
Enlarging or reducing a square or circle equally
A companion note gives the way to make a square or a circle grow and shrink by the same amount.
Hero's fountain
A Hero's fountain is drawn and labelled with its working parts — lead, air, water and valves (animelle) — the sealed vessels driving a jet by means of trapped air pressure.
Air-test instrument (anemometer)
A small instrument at the left is captioned as a 'test of air', apparently a device for gauging wind or air.
Covered water tanks
Beside a vat labelled water–water, a note directs that the covers be made over the top; a related float-in-bucket device is to be covered along with everything else.