Single-piece arch between two blocks; water and bank erosion
A body forced into an arch pushes to spring back straight; deeper water scours its bed harder.
In red chalk the top of the sheet shows an arch of a single piece springing between two rectangular blocks. The accompanying note reasons that a continuous body forced into an arch pushes along the line by which it seeks to spring back straight. The same block turns to water, observing that deeper water presses harder on its bed and that a bed or bank meeting the current more squarely is worn away faster. A faint stretch of river is sketched lower on the page.
On this page
Single-piece arch thrusting to return straight
The drawing shows an arch of one continuous piece set between two blocks. The note argues that a continuous quantity forcibly bent into an arch pushes along the line by which it 'desires to return' to the straight, an early statement of arch thrust.
Water depth, bed pressure and bank erosion
The second half of the note observes that where the water is higher it weighs more on the bed and raises its course further. The part of the bed or bank set at more nearly right angles to the straight course of the water is the more damaged by the running stream.
Stretch of river
A faint curving stretch of river is sketched in the lower part of the sheet, captioned only as such in the bundle.