entering under and turning back upon the so-called socket-plate or a kind of headpiece, with a rule lying on the ground which brings 221 it forward and always follows the place being drilled. And for the same operation, the cylinder with the drill will be revolved, being moved by hands, if it receives small bars into its middle like the spokes of a well-winch, extended in the form of a cross, which some from their shape call little stars. And the drillings made in the wall must be made sideways and upwards, so as to be higher toward the inner part, in order that the material scraped out from the brick by the drills may easily fall downwards and the metal plate fastened to the end of the lever may be well supported for the operation, being propped up by the rule lying obliquely on the ground and braced against it. And the upward perforation made by the drills does not cause only a subsidence of the wall, 222 but also one inclined toward an outward fall. And suddenly a great collapse occurs around the wall. And the manner of the leaning is as follows. Let the wall be drilled equally on the same straight line, with the holes being distant from one another a foot and a quarter, that is, 20 fingers, or a span and two palms; for the span is 12 fingers, and the palm is four. And one must begin to make the drillings from above the ground at about three feet, just as we have said before in the case of stone walls, so that the material coming down from the holes may fall upon the space left below. But when the face of the wall has been drilled in order, the holes are filled up 223 from the outer face towards the inside, not for the whole thickness but for only a foot, with dry, split pieces of wood, not squared so as to fit closely together sideways, but somewhat rounded like stakes, having a thickness at the base of not more than three fingers, and being more narrowed toward the top in order to support the wall during the time of the operation. And, if possible, let the stakes be pine-torches; but if not, dry woods smeared with pitch or with powdered sulphur with wet pitch or anointed with oil; and the stakes are made round, so that they may have gaps between one another, where the fire, entering under and turning back, may be kindled, and not be choked by the density and extinguished. But when all the holes have been filled to a depth of a foot, as has been said, let the remaining intervening spaces be drilled again in the middle on the same straight line, in order, equally with the former ones. And let the outermost holes be angled to each side, so that the perforation of the latter ones may enter into the former, and let these also be filled with shavings, that is, wood-chips or sawdust, of dry and easily flammable brushwood or splinters, upon which the fire, taking hold, makes a rapid combustion. Therefore, the stakes are purposely not of equal surface over their whole height, but are larger below, so as to be able to hold the fire and to be rekindled when wind blows into it. But if there should be a calm at the time or place of the operation, let reeds, 224 hollowed through their whole length inside, such as fowlers have, be brought to bear, being blown into with bronze nozzles; for they are moved to whatever place one wishes and kindle the fire, having a small iron pipe in front of the fire. And the diagram is below. When the perforation by means of underpinning and burning out has been completed, and the wall is firmly seated without leaning and is motionless upon the solid contrivance of the brick structure, it is necessary to use the ram. For even if the blow of the ram against the brick becomes feeble and weak, rather making a pit because of the porous and soft nature than shaking and breaking it because of the hard and resistant nature as in the case of stones, nevertheless, on account of the operation previously performed below, the wall, having been weakened at its base, will not be able to withstand the continuous batterings of the rams, but, being struck by force, will suffer perforation and admit the leaning. 225 And the joints and connections of the rams joined lengthwise, and the

ὑπεμβαίνουσαν καὶ ἀναστρεφομένην ἐπὶ τὴν ὀνομαζομένην πυελίδα ἤτοι ἐπικεφαλίδα τινὰ οὖσαν, κανόνος τῇ γῇ ἐπικειμένου τοῦ προσ221 άγοντος αὐτὴν καὶ ἐπακολουθοῦντος ἀεὶ τῷ τρυπωμένῳ τόπῳ. Περιστραφήσεται δὲ πρὸς τὴν αὐτὴν ἐργασίαν καὶ διὰ χειρῶν κινούμενος ὁ κύλινδρος σὺν τῷ τρυπάνῳ, ἐὰν κανόνια πρὸς τὸ μέσον εἰσδέξηται ὡς φρεατίας ἠλακάτης σταυροειδῶς διεκβληθέντα, ἅ τινες ἐκ τοῦ σχήματος ἀστερίσκους καλοῦσιν. Τὰς δὲ γινομένας ἐπὶ τῷ τείχει τρυπήσεις πλαγίας τε καὶ ἀνωφερεῖς δεῖ ποιεῖσθαι ὡς πρὸς τὸ ἐνδότερον μέρος ὑψηλοτέρας, ὅπως τὰ ἐκ τῆς πλίνθου ὑπὸ τῶν τρυπάνων περιξεόμενα εὐκατάφορα γίνηται καὶ τὸ ἐπ' ἄκρον τοῦ μοχλοῦ προσηλωθὲν πέταλλον καλῶς πρὸς τὴν ἐργασίαν ἀναβαστάζηται στηριζόμενον ὑπὸ τοῦ τῇ γῇ πλαγίου ἐπικειμένου κανόνος καὶ πρὸς αὐτῇ ἀντιστηριζομένου. Ἡ δὲ ἐκ τῶν τρυπάνων γινομένη ἀνωφερὴς σύντρησις οὐ ποιεῖ συγκάθεσιν μόνην τοῦ τεί222 χους, ἀλλὰ καὶ παρεγκεκλιμένην ἐπὶ τὴν ἔξω καταφοράν. Καὶ γίνεται ἀθρόως πολὺ περὶ τὸ τεῖχος τὸ σύμπτωμα. Καὶ ἔστι τὸ τῆς κλίσεως σχῆμα τοιοῦτον. Τρυπάσθω δὲ ἐξ ἴσου τὸ τεῖχος ἐπὶ τῆς αὐτῆς εὐθείας, ἀπεχομένων ἀπ' ἀλλήλων τῶν τρυπημάτων πόδα καὶ τέταρτον, τουτέστι δακτύλους ˉκ, ἤτοι σπιθαμὴν καὶ δύο παλαιστάς· ἔστι γὰρ ἡ σπιθαμὴ δακτύλων ˉιˉβ, ἡ δὲ παλαιστὴ τεσσάρων. Τὰς δὲ τρυπήσεις ἀπὸ τὴς γῆς ἄνωθεν ἀπαρχομένους δεῖ ποιεῖσθαι ὡς ἀπὸ ποδῶν τριῶν, καθάπερ καὶ ἐπὶ τῶν λιθίνων προειρήκαμεν τειχῶν, ἵνα ἡ ἐκ τῶν τρημάτων κατερχομένη ὕλη ἐπὶ τὸν ἐαθέντα κάτωθεν πίπτῃ τόπον. Ὅταν δὲ τρυπηθῇ κατὰ τάξιν μέτωπα τοῦ τείχους, ἀναγεμί223 ζονται τὰ τρήματα ἐκ τῆς ἔξωθεν ὄψεως ἐπὶ τὰ ἔνδον, οὐ πρὸς ὅλον τὸ πάχος ἀλλὰ ἐπὶ πόδα μόνον, ξύλοις ξηροῖς ἐσχισμένοις, μὴ τετραγώνοις ὥστε κατὰ πλάτος ἐφαρμόζειν ἀλλήλοις, ἀλλὰ παραστρογγύλοις ὡς πασσάλοις, πάχος ἔχουσι πρὸς τὴν βάσιν δακτύλων μὴ πλέον τριῶν, πρὸς δὲ τῇ κορυφῇ μᾶλλον ἐστενωμένοις πρὸς τὸ βαστάζειν τὸ τεῖχος κατὰ τὸν τῆς ἐργασίας καιρόν. Καὶ, εἰ ἐνδέχεται, δᾷδες οἱ πάσσαλοι ἔστωσαν· εἰ δὲ μή, ξύλα ξηρὰ πεπισσωμένα ἢ θείῳ τετριμμένῳ σὺν ὑγρᾷ πίσσῃ ἢ ἐλαίῳ ἐπαλιφέντα· στρογγύλοι δὲ γίνονται οἱ πάσσαλοι, ἵνα μεταξὺ πρὸς ἀλλήλους διαλείμματα ἔχωσιν, ἔνθα τὸ πῦρ ὑπεμβαῖνον καὶ ἀναστρεφόμενον ἐνάπτηται, καὶ μὴ τῇ πυκνότητι συμπνιγόμενον σβεννύηται. Ὅταν δὲ γεμισθῶσι πάντα τὰ τρήματα ποδὸς ἄχρι κατὰ βάθος, ὡς εἴρηται, πάλιν ἐπὶ τῆς αὐτῆς εὐθείας τρυπάσθωσαν κατὰ μέσον τὰ καταλειφθέντα διάχωρα κατὰ τάξιν ἐξ ἴσου πρὸς τὰ πρότερα. Τὰ δὲ ἔσχατα τρήματα πλαγιαζέσθωσαν ἐφ' ἑκάτερον μέρος, ἵνα ἐπὶ τὰ πρότερα ἡ τῶν ὑστέρων ἐπεισέρχηται σύντρησις, καὶ γεγεμίσθωσαν καὶ αὐτὰ ξυσμάτων ἤτοι πελεκημάτων ἢ ῥυκανισμάτων ξηρῶν καὶ εὐκαύστων φρυγάνων ἢ σχιδάκων, καθ' ὧν τὸ πῦρ ἐπιδρασσόμενον ταχεῖαν τὴν ἔκκαυσιν ποιεῖται. Ἐξεπίτηδες οὖν οἱ πάσσαλοι οὐκ ἔχουσιν ἴσην τὴν ἐπιφάνειαν κατὰ τὸ ὅλον ὕψος, ἀλλὰ μέζονές εἰσι κάτωθεν, ὥστε κρατεῖν δύνασθαι τὸ πῦρ καὶ ἀνέμου ἐμπνέοντος ἐπανάπτεσθαι. Εἰ δὲ νηνεμία κατὰ τὸν τῆς ἐργασίας καιρὸν ἢ τόπον εἴη, συμβαλλέσθω224 σαν κάλαμοι τετρυπημένοι δι' ὅλου ἔσωθεν, οἵους οἱ ἰξευταὶ ἔχουσιν, ἀσκώμασι χαλκικοῖς ἐμφυσώμενοι· πρὸς ὃν γὰρ ἄν τις ἐθέλῃ μεταφέρονται τόπον καὶ ἀνάπτουσι τὸ πῦρ, σιδηροῦν αὐλίσκον ἔμπροσθεν τοῦ πυρὸς ἔχοντες. Καὶ τὸ σχῆμα ὑπόκειται. Τῆς συντρήσεως ἐπὶ τῇ ὑποστυλώσει καὶ ἐκκαύσει τελεσθείσης καὶ τοῦ τείχους ἀκλινῶς ἠδρασμένου καὶ ἀτρεμοῦντος ἐπὶ τῷ συμπάχῳ τῆς πλινθίνης οἰκοδομῆς τεχνουργήματι, κριομαχεῖν ἀνάγκη. Εἰ γὰρ καὶ ἔκλυτος καὶ ἀνίσχυρος ἡ τοῦ κριοῦ πρὸς τὴν πλίνθον γίνεται πληγή, λακκίζουσα μᾶλλον διὰ τὸ χαῦνον καὶ μαλακὸν ἢ σείουσα καὶ ῥηγνύουσα διὰ τὸ σκληρὸν καὶ ἀντίτυπον ὡς ἐπὶ λίθων, ἀλλ' οὖν διὰ τῆς προγεγονυίας κάτωθεν ἐργασίας ἀτονῆσαν πρὸς τῇ βάσει τὸ τεῖχος οὐ δυνήσεται ἀντέχειν πρὸς τὰς συνεχεῖς τῶν κριῶν κερατίσεις, ἀλλὰ τῇ βίᾳ πληττόμενον συντρήσει τὴν κλίσιν εἰσδέξεται. 225 Τὰς δὲ συμβολὰς καὶ συνδέσεις τῶν κατὰ μῆκος συμβεβλημένων κριῶν, τάς τε