At Parma, 27 September 1514: Air, Falling Bodies, Perspective
A dated page mixing the air that clothes moving bodies, the descent of weights, and the loss of edges
Leonardo dates this page 'At Parma, at the Campana, on 27 September 1514,' then runs through four short topics. Two concern the air: he holds that the air clothing a body moves along with it, as the dust raised by a galloping horse shows, yet the air never quite matches the speed of its mover, since the dust soon whirls back and spends its impetus. Between them he notes that among rigid heavy bodies of equal weight the ratio of their speeds in falling equals the ratio of their thicknesses, and opens a section on how the true edges of opaque bodies, already invisible at short range, vanish still more at a distance.
On this page
The air moves with the body it clothes
The air that clothes bodies will move together with those bodies; experience shows this when a horse runs along dusty paths, drawing the dust along in its course.
But the air never keeps pace with its mover
The air will never be of a velocity equal to that of its mover, as the motions of the said dust show: following the horse's course, in the briefest span of motion it turns back with a whirling, eddying motion and there consumes its impetus.
Speed of descent follows thickness
On the descent of heavy bodies: among rigid (non-bending) heavy bodies of equal weight, the proportion of velocity to velocity in their descents will be as the proportion of their uniform thicknesses.
Edges of opaque bodies lost at distance
If the true edges of opaque bodies are invisible at any least distance, they will be all the more invisible at long distances; and since the true figure of each body is known by its boundaries, when knowledge of the whole fails through distance, knowledge of its parts fails still more.
Dateline at Parma
The page is headed with a note of place and date: at Parma, at the Campana, on the 27th day of September 1514.