16I have explained what I thought most requisite respecting scorpions, catapultæ, balistæ, no less than tortoises and towers, who invented them, and in what manner they ought to be made. It did not seem necessary to write on ladders, cranes, and other things of simpler construction; these the soldiers of themselves easily make. Neither are they useful in all places, nor of the same proportions, inasmuch as the defences and fortifications of different cities are not similar: for machines constructed to assault the bold and impetuous, should be differently contrived to those for attacking the crafty, and still dissimilar, where the parties are timid.
16With regard to scorpiones, catapults, and ballistae, likewise with regard to tortoises and towers, I have set forth, as seemed to me especially appropriate, both by whom they were invented and in what manner they should be constructed. But I have not considered it as necessary to describe ladders, cranes, and other things, the principles of which are simpler, for the soldiers usually construct these by themselves, nor can these very machines be useful in all places nor in the same way, since fortifications differ from each other, and so also the bravery of nations. For siege works against bold and venturesome men should be constructed on one plan, on another against cautious men, and on still another against the cowardly.