Rules · Theory · Proportion
Hold that the beauty of the orders comes from fixed proportions that please by nature, as consonances do in music; where the ancients differ, the differences answer to circumstances such as distance and height.
Blondel wrote this against Claude Perrault (Positive and arbitrary beauty), his colleague at the Academy, who had argued that proportions please only by custom. The dispute ran through the Academy for decades and is the first great argument of modern architectural theory: is beauty in architecture discovered, like a law of nature, or made, like a convention? Blondel’s answer kept the orders at the centre of French teaching; Perrault’s prepared the way for later theories that ground architecture in use and construction instead.
To find how thick the pier of an arch must be, divide the intrados into three equal parts; draw a line from the springing through the first division, and produce it beyond the springing by its own length. A vertical through the end of that line marks the outer face of the pier.
pier ≈ ¼ span (semicircle) · ≈ 0.23 span (equilateral) · less for a lancet
To unify a façade of two or more storeys, run a single order of pilasters or columns through all of them, from the base to the main cornice.
Proportion every step so that twice its height plus its depth equals the length of a natural pace on the level: two feet, or 24 pouces.
2 r + g = 24 pouces ≈ 65 cm (modern practice: 60–66 cm)
Give the flight of steps before a temple an odd number, so that one who starts with the right foot will also set the right foot first on the top.
Make the parterre oblong rather than square, since figures somewhat oblong look better on the ground than square ones; later practice made it as broad as the front of the house and about twice as long.
parterre oblong; later practice: width ≈ house front, length ≈ 2 × width
Proportion the width of an allée to its length: a walk of about 100 toises (some 200 m) should be 5 or 6 toises wide, one of 200 toises 7 or 8, and so on, so that a long walk does not seem to narrow to a slot in the distance.
100 toises long → 5–6 wide · 200 → 7–8 · 300 → 9–10 · 400 → 10–12 (1 toise ≈ 1.95 m)
Cite this page Chris Paton, “Proportion is natural, like harmony”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/blondel-natural-proportion. Text, drawings and models licensed under CC BY-NC 4.0.