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.  The romance of Richard Coeur de Lion tells how in the King’s Fleet an entire ship was taken up by one such machine with its gear:—­

  “Another schyp was laden yet
  With an engyne hyghte Robinet,
  (It was Richardys o mangonel)
  And all the takyl that thereto fel.”

Twenty-four machines, captured from the Saracens by St. Lewis in his first partial success on the Nile, afforded material for stockading his whole camp.  A great machine which cumbered the Tower of St. Paul at Orleans, and was dismantled previous to the celebrated defence against the English, furnished 26 cart-loads of timber. (Abulf.  Ann.  Muslem, V. 95-97; Weber, II. 56; Michel’s Joinville, App. p. 278; Jollois, H. du Siege d Orleans, 1833, p. 12.)

The number of such engines employed was sometimes very great.  We have seen that St. Lewis captured 24 at once, and these had been employed in the field.  Villehardouin says that the fleet which went from Venice to the attack of Constantinople carried more than 300 perriers and mangonels, besides quantities of other engines required for a siege (ch. xxxviii).  At the siege of Acre in 1291, just referred to, the Saracens, according to Makrizi, set 92 engines in battery against the city, whilst Abulfaraj says 300, and a Frank account, of great and small, 666.  The larger ones are said to have shot stones of “a kantar and even more.” (Makrizi, III. 125; Reinaud, Chroniques Arabes, etc., p. 570; De Excidio Urbis Acconis, in Marlene and Durand, V. 769.)