Load-bearing of columns, and a mirror for making fire
Joining columns to carry more weight, composite pillars, a burning mirror, and a one-sided load.
Leonardo examines how much weight columns carry: two touching columns, each good for 5,000 pounds, together bear only 10,000, and he tabulates composite pillars a, b, c, d rated at 5,000, 12,000, 20,000, and 40,000 pounds, with their plans drawn below. A separate note treats a concave mirror for fire: the more times the tip of the solar pyramid divides into its base, the hotter it burns. He ends by warning that a pillar loaded on one side only will not last, bending toward the load like a stack of game pieces that acts as a balance.
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Two joined columns bear only their combined load
If two columns each able to support five thousand pounds are set together so that they just touch, they will support no more than ten thousand pounds. The drawing shows the two round columns under a weight labeled 10,000, with a plan of the two touching bases below.
Composite pillars and their rated loads
A row of four composite pillars a, b, c, d is drawn with rated loads of 5,000, 12,000, 20,000, and 40,000 pounds, each with its plan below (a single square, two concentric squares, two adjacent squares, and a quartered square).
A concave mirror that makes fire
A concave mirror concentrates the solar rays onto a spherical object, which bursts into flame. As many times as the tip of the solar pyramid, cut at any part, enters into its base, so many times hotter will it be than that base.
A pillar loaded on one side bends and fails
A pillar loaded on only one side will not last long, bearing less weight the farther the load lies from the perpendicular b. A stack of game pieces loaded on one side bends toward the load and behaves like a balance, the greater weight prevailing over the lesser.