Draining harbours by caissons; a rotating profile-template
Emptying ports with caissons, canal outlets to the sea, and the sagoma on its swivel
This page joins two of Leonardo's late technical concerns. One set of notes and figures treats the draining of harbours by means of caissons (casse) emptied of water and soil in sequence, and shows several ways of discharging canals into the sea. The rest develops a 'sagoma' (profile template) mounted on a rotating swivel (circunvolubile a), giving its dimensions in braccia and insisting that the pyramid's angle b never shift from its point, so that the reflections converge along the mathematical axis through the two poles of the rotation. A framework (incastellatura) to carry the template is also noted.
On this page
Draining a harbour with caissons worked in turn
Leonardo works with a set of caissons (casse): when one has been emptied of water and soil, the water of the second is poured into the one already emptied. Once a caisson is dry, its piles are pulled and the same timber is reused to build the next box in the sequence.
Three ways of discharging canals into the sea
A short heading and figure show 'various ways of discharging water into the sea'. A marginal caution adds that the wood of the template should be well pitched so that it does not bend.
Profile template (sagoma) on its rotating swivel
The figure of the sagoma is laid out with points b m c - a - p - n - q, standing 1 and 1/2 braccia high, and the reader is sent to leaf 44 to see how the swivel a is pivoted. The essential requirement of the rotary motion is that the angle b of the pyramid a b never shift from its point under any curved motion.
Convergence of the template's reflections
Along the front of the mathematical line that passes through the two centres of the two poles of the rotary motion, Leonardo places the convergence (concorso) of the reflections (refressi) of the template. The rotating profile is thus tied to where the reflected rays meet.