112 MILITARY SCIENCES. 



elevation, movable towers were erected. Such movable towers were con- 

 structed of carpenters' work, with steps on the inside, and with a platform 

 and battlements, set upon rollers or wheels, and by means of pulleys and 

 windlasses moved on to the point of attack. Frequently these towers, when 

 they were designed to effect the actual scaling of the wall by the troops? 

 were provided with a drawbridge, which was let down as soon as the 

 tower reached the designated spot, and thus a passage was established for 

 the troops from the tower to the wall. 



As to the construction of these movable towers, it did not differ greatly 

 from that of a house with several stories, for they consisted of several rows 

 of uprights, united by horizontal tie-beams, w^hich formed the stories. The 

 whole was made firm and strong, ' and so bound together within, that it 

 could not only sustain its own weight and that of the soldiers, but endure 

 being moved from place to place. We can scarcely conceive how it was 

 possible to move these enormous machines upon so few wheels, for, accord- 

 ing to the testimony of ancient authors, the largest towers had not more 

 than eight and the smaller only four w^heels. The height of the towers was 

 regulated according to the wall which was to be attained ; but there were 

 such towers carried, in pieces, w^ith the baggage of the army, and for which, 

 in case their height was deficient, a mound was thrown up. The smallest 

 towers were 120 feet in height, 34 feet wide, and usually of 10 stories : while 

 the largest were 240 feet high, 47 feet wide, and had 20 stories. To this 

 class belonged the tower of which Demetrius Poliorcetes made use at the siege 

 of Rhodes {pi. S5,Jig. 4), constructed by the Athenian architect Epimachus. 

 This machine rested upon eight wheels on each side and could be moved 

 from within, while a separate body of workmen assisted on the rear side 

 without. The wheels had all of them trendies {antistrepta) , so that the 

 tower could be moved sideways and obliquely. At greater distances from 

 the wall, the towers were moved by means of ropes and pulleys with wind- 

 lasses, as our engraving shows. Every story had openings or windows, 

 out of which beams or stones were shot, but these windows were filled with 

 bags of skin stuffed with wool and only opened to shoot through them. 

 Frequently the towers were provided also with exterior galleries, for bow- 

 men and slingers, and on the ground- floor, or higher, battering-rams were 

 placed to destroy the walls {pi. S5,fig. 5). Invariably these towers tapered 

 off as they went up, and a drawbridge w^as always required to bring the 

 troops who manned them upon the wall, as in Jig. 4. Within the tower was 

 usually a vat for water, in order to flood at once any part which might 

 be set on fire bv the fire-missiles of the foe. Sometimes the towers were 

 not placed upon wheels, but moved by means of rollers, as that which Julius 

 Caesar employed at the siege of Namuronum (Namur). Usually the towers 

 were hung, from top to bottom, with wet hides, as soon as they came 

 within range of the enemy's missiles, or with covers of goats' hair, to 

 preserve them from fire and to deaden the force of blows from the hostile 

 shot. 



Movable towers were used in later times also, and fig. 6 represents such 

 a tower of the twelfth century ; it is surrounded on the summit by a 

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