Eddies of Water and Air, and a Tangent-Angle Construction
With a roof-truss sketch; notes on cloud formation and a geometric proof
Two fragments are mounted together. The upper sheet (118a) carries a sketch of a triangular gabled roof frame and small spiral and coil sketches beside a dense block of text on the surfaces of water, air and fire and on the eddies (retrosi) that form in them, including a note on how clouds grow and diminish. The lower sheet (118b) bears a geometric diagram of a circle with sighting lines and a lettered construction for making one angle equal to another by drawing a tangent, together with its proof.
On this page
Eddies in water, some full of air, some of water
Of the eddies of water, some are full of air at the center and some full of water: those that begin at the surface are full of air, those beginning within the water are full of water and more lasting, because water within water does not weigh as water over air does. Hence eddies of water surrounding air have weight and die at once.
The surface of air compared to water and fire; clouds
If the surface of the air is bounded by fire as water is by air and earth by water, and if that surface receives waves and eddies like water, then the thinner the air is than water, the more numerous the revolutions of its eddies. He adds a heading on the clouds that grow or diminish through the air and its cause.
Making angle e c p equal to angle f c L by a tangent
The angle e c p must equal the angle f c L. Set points e and f, draw lines to the center g, extend e f and the indefinite line b q until they meet at d; from d draw the straight line d a tangent to the circle, and from it the perpendicular c g to the center; where it meets the circle is the angle of contingency. If g f were made equal to g e, the point c would lie at n.
Roof-truss framing sketch
At the top of the upper fragment is a sketch of a triangular gabled roof frame with rafters and ties, the sheet being catalogued among studies of the framing and covering of a roof.