a small demonstration
the ha‑ha
Morning, {{name}}. This is the manor's south lawn, looking out across the park. Somewhere between you and the sheep is a ha‑ha — a sunken ditch faced with a stone wall on the pasture side, whose purpose is to keep the livestock out without spoiling the view. Slide the walker to move toward it, or pick a different garden below — each one dug its ditch to a different depth.
Arrow keys nudge the walker when the slider is focused. From about twenty metres out there is nothing to see; from about three metres out, quite a lot, all at once.
four gardens
The dimensions above are Stowe's. No two estates dug their ditch to the same depth — the wall only has to clear whatever is grazing on the far side. Pick a garden to re-dig the scene to its own numbers.
side profile — the same scene, in section
guess the lip
The steward's own test: we'll walk out to somewhere between four and a hundred metres and hide the reading. Guess the distance to the near lip, in metres, and see how trained your eye already is.
the plaque
A ha‑ha is a boundary that is not, from the manor's side, a boundary. Charles Bridgeman began cutting them into the grounds of Stowe from about 1719, on the instruction of Viscount Cobham and to a plan that included his younger colleague William Kent. The point was to keep the deer and sheep off the ornamental lawns without interrupting the eye's passage from the drawing-room window out to the parkland. A wall would have interrupted it. A hedge would have interrupted it. A dry ditch, sunk into the ground with a stone retaining wall on the far side and a gentle slope on the near side, does not interrupt it — because from any distance greater than a walking pace or two, the wall shows on the retina as a horizontal band a fraction of a degree tall, which the visual cortex accepts as a slight tonal seam between lawn and pasture and does not further interrogate.
The word is said, by Horace Walpole in his Essay on Modern Gardening of 1780, to have entered English as the exclamation of surprise made by a person nearly walking into one. Walpole has been challenged on this by every subsequent etymologist and has never been quite dislodged.
This toy shows the mechanism at Stowe, {{name}}. From sixty metres out, the ha‑ha is a strip of stone about a pixel tall. From ten, it is a visible band. From three, the illusion is finished: you are standing at the top of a masonry wall, and behind you is the manor, and in front of you is the sheep, and there is a moment there of the small honest surprise the word is named after.
— C