Weight.[8] In This Case The Unlucky Engineer Was "Hoist With His Own Petard," For While He Stood Adjusting One Of His Engines, It Went Off, And Shot Him Into The Town.

With reference to such cases the Emperor calculates that a stone of 3000 lbs.

Weight might be shot 77 yards with a counterpoise of 36,000 lbs. weight, and a shaft 65 feet long. The counterpoise, composed of stone shot of 55 lbs. each, might be contained in a cubical case of about 5-1/2 feet to the side. The machine would be preposterous, but there is nothing impossible about it. Indeed in the Album of Villard de Honnecourt, an architect of the 13th century, which was published at Paris in 1858, in the notes accompanying a plan of a trebuchet (from which Professor Willis restored the machine as it is shown in our fig. 19), the artist remarks: "It is a great job to heave down the beam, for the counterpoise is very heavy. For it consists of a chest full of earth which is 2 great toises in length, 8 feet in breadth, and 12 feet in depth"! (p. 203).

Such calculations enable us to understand the enormous quantities of material said to have been used in some of the larger mediaeval machines. Thus Abulfeda speaks of one used at the final capture of Acre, which was entrusted to the troops of Hamath, and which formed a load for 100 carts, of which one was in charge of the historian himself.

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