Excavating and hoisting earth, with figures of an egg-shaped mirror
The waste of throwing earth by shovel, a hoisting instrument matched against carts, and Latin notes on a mirror.
The small upper sheet (915a) carries three figures with Latin captions on mirrors: an egg-shaped mirror, a form taken from the middle of a section, and a lettered diagram (d a - e - g z b). The large lower sheet (915b) is devoted to excavation: one passage argues that throwing earth upward by shovel wastes about a quarter of the labour, time and cost, since a quarter of the material falls back and returning the tool and reloading takes four times as long as the throw. A second passage compares hoisting instruments with carts, which he found inconvenient on inclines, cites his treatise 'on local motion and on force and weight,' and concludes that no animal can raise more than its own body weight in equal time, for which he has devised a figured instrument; a bucket lifted by a pulley is sketched alongside.
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Why throwing earth upward by shovel wastes a quarter of the work
The workers, the labour, the time and the expense lose a quarter part in this method, since roughly a quarter of the material universally falls back from the tool that throws the earth up. Adding the time to bring the tool back and to prepare the person to take up new earth, with two or three thrusts of the shovel, the return takes without doubt four times as long as the throw itself; so the operation is of little worth, though it is the simplest that can be done.
A hoisting instrument matched against carts
Many instruments compared with carts for such excavations have, in equal time, been beaten by them; but on close study he found carts inconvenient, since on the inclines they must climb they gain much heaviness while their mover loses power. He concludes that no animal can, in equal time and endurance, raise more weight than that of its own body, and for this he has devised the figured instrument, a bucket raised by a pulley being sketched beside the text.
Latin figures of an egg-shaped mirror and a section
Three small figures on the upper sheet are captioned in Latin: the first a mirror shaped like an egg (speculum ... figura ovi), the second a form taken from the middle of the section, and the third a lettered diagram carrying the labels d a - e - g z b.
Force and weight on an incline, confirmed by experience
On the slopes carts must climb they acquire much heaviness while their mover loses power, a matter he says is shown in his treatise 'on local motion and on force and weight.' He insists that whatever he proposes as best will always be confirmed by experience rather than by reasoning alone.