Geometrical Devices for Masonry Work
Bib. Nat. ms. fr. 19093, fol. 40
This is a rather atypical page from Villard's manuscript, although it is one of the more interesting ones for construction history or the history of technology. It has a number of different sketches each boxed off in its own little cell with a brief note explaining it:
Top
Cutting a regular pendant
Determining the diameter of a round object by placing it in a corner
Gauging a right angle and cutting a "tierce-point arch" keystone
Making a keystone for a "fifth-point arch"
Archimedes Spiral
Middle
Joining a four-cornered pillar
Cutting a voussoir "by eschelons"
Laying out the pattern for a church spire
Bottom
Cutting voussoirs for hanging arches
Setting up two equal-height pillars without plumb line or level
Measuring the height of a tower with a 45 degree triangle (this illustration
includes the little fellow on the bottom and the tower at the far right)
The fact that the descriptions are added in around the sketches shows that they were added later, and this has suggested to some commentators that the manuscript was intended for teaching purposes. Some sketches are quite clear to the casual observer: the second one from the left in the top row simply shows how to measure the diameter of a column drum by rolling it into a corner; the bottom left one shows how to cut the voussoirs of an arch so that the center pillar can be removed, leaving the arch and capital suspended in mid-air.
Other drawings, however, are rather obscure. The top left illustration has a caption below which reads "How to make regular pendants: place upside down." Villard appears to be making a note to himself to remember how to lay out a pendant (i.e. one of the stones in an arch - presumably the keystone): take a skew paralellogram (although not necessarily a regular one) and flip it over, and realign the base (here drawn as the top). In this way, you generate a symmetrical block. Other drawings on the page are just as opaque to the modern reader.
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