Digging Ditches: Spade-Work, Earth Weights and Gangs
Technique of throwing earth, weights of soils per square braccio, and rotation of diggers
This densely written sheet studies the excavation of ditches: how a digger should first draw the spade a little backward so that the earth, made to travel a longer path, is thrown forward with greater 'impetus', and how oxen and gangs of men may be ordered so as not to deceive their overseers. The left half tabulates the weight per square braccio of many kinds of earth, sand and gravel — wet, dry, packed and loose — together with salt and river water, noting the differences. Numerous lettered diagrams (a b c, d e f, g h i, K l m ...) show work-teams rotating along the ditch, while marginal calculations reckon barrow-loads and man-days ('as much as 100 men do here in a day, one man does in 100 days'). Much of the text runs along cut and mutilated margins.
On this page
Impetus of the thrown spadeful
Because the shovel makes a longer path, the earth goes with greater impetus: once the earth is loosened, the digger must first pull the spade a little backward and then throw it forward, and that backward draw makes it travel a longer way forward, which is what gives the impetus.
Weights of earth, sand and gravel per square braccio
The left half lists the weight per square braccio of damp earth mixed with fine gravel (loose vs. packed), dry and wet mixtures, common earth, salt water (595 lb), fresh river water, and dry sea and river sand (878 and 850 lb), noting the differences between wet and dry states.
Rotation of digging teams along the ditch
With n m as the width of a ditch, three men c b a with spades throw earth to men t S r; the timing is arranged so all load and empty their spades together, so that every 2 turns three spadefuls reach the bank and the men cannot deceive their overseers.
Uneven digging to be avoided; the man-day ratio
Leonardo warns that the manner of digging in which the depth of the ditches does not increase equally is to be avoided, and states the ratio of labour: as much as 100 men do here in a day, one man does in 100 days.