Canal-boat in a vaulted gallery, with a stepped well
Red-chalk study of a covered waterway served by air-vents, and ripples on sand
In red chalk Leonardo sketches a 'naviglio in galleria' — a boat or canal running through a vaulted gallery — served by air-vents (spiraculi), together with a stepped well (pozzo a gradoni). A line of mirror-writing beneath states that the hollows of the ripples visible on sand lie at equal angles to the current. The faint chalk drawing shows an arched structure with a stepped, tapering core, and further untranscribed jottings appear at the top of the sheet.
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Canal-boat in a gallery, served by air-vents
The sheet is headed as a 'naviglio in galleria', a boat or waterway carried through a covered gallery, provided with air-vents (spiraculi) to admit air. Leonardo notes only the vents beside the vaulted structure drawn in red chalk.
Stepped well (pozzo a gradoni)
A stepped, tapering structure is drawn in red chalk and named a stepped well. Its concentric rings of steps descend toward the base of the sheet.
Ripples on sand align with the current
Leonardo observes that all the hollows of the undulations visible upon the sand stand at equal angles to the motion of the water. The remark ties the pattern of ripples to the direction of the current.