with slender and close-set posts, rather than thick and widely-spaced ones, with a plank placed above and below, so that the posts, giving way at the ground, may not fail to hold. And when the excavation is finished and propped up, let the space between the props be filled with flammable materials, such as brushwood, split dry wood, pine torches, and whatever other things of this sort are suitable for burning; and thus let it be set on fire. If any place is lacking, let it be lit with fire-throwers; 217 and let it have also dry wood shavings scattered about, smeared with wet pitch or oil; and thus when the underpinnings are burned away, the wall will collapse. And the appearance of the structure is of this kind. Into the upright timbers of these tortoises, let broad-headed nails of 8 fingers in height, that is, spikes wrought of iron, be driven in from above to a depth of 4 fingers; and let them have the remaining four protruding. and the space in between should be smeared and filled up with rich and sticky clay kneaded with pig's or goat's hair, so that it may not be pulled apart nor split. For it will be held firm both by the closeness of the nails and by the breadth of their heads. And let rags or hides be hung on the sides, so that neither hot sand, nor 218 pitch, nor boiled fenugreek, nor oil poured on—which by nature is quickly heated and cools slowly—may drip on those working inside; for like fire they consume the flesh of men. Thus, therefore, the tortoises, being so constructed, will be protected from being burned by the fire-bearing missiles thrown from above and by the kindled flames, and the heated liquids poured on them will not penetrate inside. Likewise, let both wicker shields and wicker-tortoises be covered over their wickerwork with soaked hides of newly-slaughtered oxen, as these are able to resist fire. And let these tortoises be plastered at a distance from stone-throwing engines and catapults, and being fastened together and on wheels, let them be brought up to be joined to the walls. And the diagram is set out below. 219 But some, against stone walls, as is the custom, place wood close up against them from below, so as to set it on fire and break up the stones. But the work is sometimes difficult and dangerous, because water poured from above extinguishes the fire, and the force of the fire becomes weaker sideways, as it is by nature upward-moving and happens to be stronger in its effect upwards; and those working inside will not be able to be under a tortoise due to the rush of the flame; for they will be burned along with it. Therefore, earthenware pots are made, bound together with iron plates on the outer part, and they are filled with fine charcoal; and from the outer face of the plate towards the bottom they are pierced with an opening up to a finger's-width hole, and receive from there a small iron pipe, 220 into which another is inserted having a bellows. And the charcoal, having caught fire and being fanned, produces a burning effect like a flame, which gets under the stone and breaks it up, especially when vinegar or urine or some other of the pungent liquids is poured on. And the diagram is as has been drawn below. Lead-workers use it continuously. If we wish to demolish brick walls quickly, we will make very numerous holes in them with drills, being protected by tortoises smeared from above, or by wicker shields having very safe roofs and being covered over their wickerwork with the hides of newly-slaughtered oxen, on account of both the weights thrown down upon them and the heated liquids poured on. Let the drills be similar to carpenters' tools; for an iron bar is made not less than 5 feet in length, having a finger's width in diameter and a thickness all around of about four fingers, having a similar iron plate nailed to its front end, of 12 fingers in breadth and 8 in height, narrowed in the middle in front in the shape of a gardener's broad spade; and at the other end it receives a wooden, narrow-waisted cylinder from a lathe, turned by a bow-drill, having in the middle of its rear part a head-shaped projection

στυλαρίοις λεπτοῖς μᾶλλον καὶ πυκνοῖς, καὶ μὴ παχέσι καὶ ἀραιοῖς, ἐπάνω καὶ ὑποκάτω σανίδος τιθεμένης, ἵνα μὴ πρὸς τῇ γῇ ὑποχαλῶντα τὰ στυλάρια οὐ βαστάσῃ. Ὅταν δὲ τελειωθῇ τὸ ὄρυγμα καὶ ἐπιστυλωθῇ, ἀναπληρούσθω τὸ κατὰ μέσον τῶν ἐπιστύλων ὑλῶν εὐκαύστων, οἷον φρυγάνων, ξύλων ξηρῶν ἐσχισμένων, δᾴδων καὶ ὅσα τούτων ἕτερα πρὸς ἔκκαυσιν ἐπιτήδεια· καὶ οὕτως ἀναφθήτω. Εἰ δέ τις ἐλλείπει τόπος, πυροβόλοις ὑφαπτέσθω· 217 ἐχέτω δὲ καὶ ξύσματα ξύλων ξηρὰ περιεσπαρμένα σὺν ὑγρᾷ πίσσῃ ἢ ἐλαίῳ ἐπαλιφέντα· καὶ οὕτως ἐκκαέντων τῶν ὑποστυλωμάτων καταπεσεῖται τὸ τεῖχος. Καὶ ἔστιν ἡ ὄψις τοῦ σχήματος τοιαύτη. Τοῖς δὲ τῶν χελωνῶν τούτων παρορθίοις ξύλοις ἧλοι πλατυκέφαλοι ὕψους δακτύλων ˉη, ἤτοι καρφία ἐκ σιδήρου εἰργασμένα ἄνωθεν ἐμπησσέσθωσαν ἄχρι δακτύλων ˉδ· τοὺς δὲ λοιποὺς τέσσαρας ὑπερέχοντας ἐχέτωσαν. τὸν δὲ διὰ μέσου τόπον πηλὸν λιπαρὸν καὶ κολλώδη μετὰ τριχῶν χοιρείων ἢ τραγείων μεμαλαγμένον ἐπιχρίειν καὶ ἀναγεμίζειν, ἴνα μὴ διασπᾶται μηδὲ διασχίζηται. Κρατηθήσεται γὰρ καὶ διὰ τὴν πυκνότητα τῶν ἥλων καὶ διὰ τὸ πλάτος τῶν κεφαλῶν αὐτῶν. Ῥάκη δὲ ἐκ πλαγίων ἢ δέρματα ἐπικρεμάσθωσιν, ἵνα μήτε ἄμμος θερμὴ μήτε 218 πίσσα μήτε τήλη ἀφεψηθεῖσα μήτε ἔλαιον ἐπιχεόμενον, ὡς ταχέως φύσει θερμαινόμενον καὶ ψυχόμενον βραδέως, τοῖς ἔνδον ἐργαζομένοις ἐνστάζῃ· παρομοίως γὰρ πυρὶ τὰς τῶν ἀνθρώπων ἀναλίσκουσι σάρκας. Οὕτως οὖν κατεργαζόμεναι αἱ χελῶναι διαφυλαχθήσονται πρὸς τὸ μὴ καίεσθαι ἐκ τῶν ἐπιβαλλομένων ἄνωθεν πυροφόρων καὶ ἀναπτομένων φλογῶν, μηδὲ διέρχεσθαι ἔνδον τὰ ἐπιχεόμενα τεθερμασμένα ὑγρά. Ὡσαύτως δὲ λαῖσαί τε καὶ γερροχελῶναι ἐπὶ τὰ πλέγματα σκεπέσθωσαν δέρμασι διαβρόχοις βοῶν νεοσφαγῶν ὡς δυναμένοις πυρὶ ἀντιμάχεσθαι. Αὗται δὲ αἱ χελῶναι πόρρωθεν λιθοβόλων ὀργάνων καὶ τοξοβολιστρῶν χριέσθωσαν, συμπεπηγυῖαι δὲ καὶ ὑπότροχοι συμβληθεῖσαι τοῖς τείχεσι προσαγέσθωσαν. Καὶ τὸ σχῆμα ὑπόκειται. 219 Τινὲς δὲ ἐπὶ λιθίνων τειχῶν ξύλα ὡς ἔθος περιτιθέασι προσεγγίζοντα κάτωθεν, ὥστε ἀνάπτεσθαι καὶ θρύπτειν τοὺς λίθους. ∆ύσχρηστον δὲ τὸ ἔργον ἐνίοτε καὶ ἐπισφαλὲς γίνεται, ὅτι καὶ ὕδωρ ἄνωθεν ἐπιχεόμενον σβεννύει τὸ πῦρ, καὶ ἀσθενεστέρα πρὸς πλάγιον ἡ τοῦ πυρὸς φορὰ γίνεται, ὡς φύσει ἀνωφερὴς καὶ πρὸς ἐνέργειαν ἰσχυροτέρα τυγχάνουσα· καὶ οὐ δυνήσονται ἐπὶ τῇ τῆς φλογὸς ὁρμῇ οἱ ἔνδον ἐργαζόμενοι ὑπὸ χελώνην εἶναι· συγκαήσονται γάρ. Γίνονται οὖν κύθρινοι ὀστράκινοι διὰ πετάλλων σιδηρῶν ἐπὶ τοῦ ἔξωθεν μέρους συνδεδεμένοι καὶ γεμίζονται ἀνθράκων λεπτῶν· ἀπὸ δὲ τῆς ἔξωθεν ὄψεως τοῦ πετάλλου πρὸς τὸν πυθμένα τέτρηνται ἀνεῳγότες ἄχρι δακτυλιαίου τρυπήματος καὶ σιδηροῦν αὐλί220 σκον ἐκεῖθεν δεχόμενοι, πρὸς ὃν ἄλλος ἐμβάλλεται ἄσκωμα ἔχων. Πῦρ δὲ λαβόντες οἱ ἄνθρακες καὶ ἐμφυσώμενοι ὁμοίαν φλογὸς ἀπεργάζονται ἔκκαυσιν ὑπεμβαίνουσαν τῷ λίθῳ καὶ θρύπτουσαν, ἢ ὄξους ἢ οὔρου ἤ τινος ἄλλου τῶν δριμέων ἐπιχεομένων. Καὶ ἔστι τὸ σχῆμα οἷον ὑπογέγραπται. Κέχρηνται δὲ αὐτῷ συνεχῶς οἱ μολιβδουργοί. Ἐὰν πλίνθινα τείχη καταβαλεῖν ταχέως θελήσωμεν, πυκνοτάτας ἐπ' αὐτὰ τρήσεις διὰ τρυπάνων ποιήσομεν, ὑπὸ χελωνῶν ἄνωθεν ἐπικεχρισμένων σκεπόμενοι, ἢ λαισῶν ἀσφαλεστάτας στέγας ἐχουσῶν καὶ δέρμασι βοῶν νεοσφαγῶν περὶ τὰ πλέγματα σκεπομένων διά τε τὰ πεμπόμενα κατ' αὐτῶν βάρη καὶ τὰ ἐγχεόμενα τεθερμασμένα ὑγρά. Τὰ δὲ τρύπανα ἔστωσαν τεκτονικοῖς ὀργάνοις παρόμοια· μοχλὸς γὰρ γίνεται σιδηροῦς μῆκος ποδῶν μὴ ἔλασσον ˉε, δακτυλιαίαν τὴν διάμετρον ἔχων καὶ πάχος γυρόθεν ὡσεὶ δακτύλων τεσσάρων, πέταλλον ὁμοίως σιδηροῦν ἐπὶ τὸ ἔμπροσθεν ἄκρον προσηλωμένον ἔχων πλάτους δακτύλων ˉιˉβ καὶ ὕψους ˉη, ἐστενωμένον κατὰ μέσον ἔμπροσθεν ἐν σχήματι κηπουρικοῦ πλατυλισγίου· πρὸς δὲ τὸ ἕτερον ἄκρον ξύλινον ἀπὸ τορλίου μεσόστενον εἰσδέχεται κύλινδρον ὑπὸ ἀρίδος στρεφόμενον, ἔχοντα κατὰ μέσον τοῦ ὀπισθίου μέρους κεφαλοειδῆ παρεξοχὴν