The Manuscripts of Leonardo da Vinci, Vol. 2

— Water that descends by one inch original: "once"; a historical unit of measure per mile will have a motion of 1/4 brasse original: "brasse"; a unit of length roughly equal to the reach of a man's arms, about 6 feet for one beat, that is to say, one musical beat. That which descends by 2 inches per mile will descend and have a motion of 1/2 brasse per beat, and likewise that which descends by 4 inches will have a motion of one brasse per beat.

— There can be no voice [sound] where there is no motion or percussion of air; there can be no percussion of air where there is no instrument; there can be no incorporeal incorporeal instrument; since this is the case, a spirit can have neither voice, nor form, nor strength, and if it takes on a body, it will not be able to enter penetrate or enter where the doors are closed — 4 —

— 4 — and if someone were to say that by gathered and tightened [compressed] air, the spirit takes on bodies of diverse forms, and that by this instrument it speaks and moves with force, to this part I say [I reply] that where there are neither nerves nor bones, there can be no force exerted in any movement made by imagined spirits. — Flee the precepts of those speculators whose reasonings are not confirmed by experience¹.

ON MOTION AND PROPORTION

— If you want to know where and in what part of the path the object projected by a violent cause [acts most?], you shall make a mound of fresh earth; with a crossbow you shall shoot an arrow into it from various distances, and where the same arrow sinks in the deepest, there is the distance that produces the most force.

Suppose this case: the arrow, marked for 400 brasses, shoot it first from 25, then from 50. Move back until 400, shooting every 25 [brasses], and thus you will see in what part of the flight the arrow has the most force, whether at 1/3, or 1/4, or 1/5 of the way.

— If you want to see an experiment in proportion, if a stone is thrown by the small bricole a "bricole" is a type of small medieval catapult or traction trebuchet to 20 brasses with a counterweight of ten, see if a counterweight of 20 will throw it twice as far, more or less, and let what you throw be fresh earth wrapped in paper. Let the earth be fresh so that it does not bounce after the impact; let it be wrapped in paper so that it does not stick to the bricole.

— To raise and place a beam through a window with ease.

1. These are citations added by the transcriber/editor referring to historical works on Leonardo da Vinci by Libri, Houssaye, and Govi. Libri, History of Mathematical Sciences in Italy, vol. III, p. 237. Ars. Houssaye, History of L. da V., p. 225. — G. Govi. Essay on the works of L. da V., p. 8, col. 1.