Full text: Vitruvius: The architecture of M. Vitruvius Pollio

their capitules are made holes, thipugh which cords of hair (that of women chiefly), er of 
sinews, are drawn, and whose magnitudes âte adjusted by the laws of gravity to the weight 
of the stone that the balista is intended to discharge; as those of the catapultae are to the 
length of the dart. However, that those who are unacquainted with arithmetic or geometry 
may be prepared, and not be occupied by study, in the time of the dangers of war, 1 fhall 
here reveal what I have acquired by my own experience, as well as what I have learnt from 
authors; and as the rules of these things are founded on the weights and measures of the 
Greeks, I shall transcribe them so that they may also agree with our weights. 
(15) The capitule AIHB, Fig. XCVIII. of the balista 
was formed similarly to that of the catapulta, excepting 
that the two hemitones AFHC and DIEB were disposed 
farther apart, leaving a wider interval CE between the two 
meloste GG, which in the balista were called antista. The 
purpose of this engine, which was to throw large stones, 
required so large an interval: Heron says it should be 
a little less than double the length of the arms RS. 
The scutulae or peritretae AF and DI, which in the 
catapulta extended in one piece over both hemitones, 
were in the balista separate, and extended over one 
hemitone only. The lower peritretae H C and EB were 
also disjoined in the same manner; so that the two hemi¬ 
tones were not connected by their peritretae, but by two 
other pieces of timber KL and MN; one of which 
KL extended over the two upper peritretae, and the other 
MNunder the two lower peritretae; being secured to the 
same by tenons. The parastæe O were made like those 
of the catapulta, but had a curvilinear protuberance P at 
the back part, opposite the circular cavity Q in which 
the arm lag, in order to strengthen it. The antiste C had 
also a curved protuberance toward R, called hypopterna, 
on the side toward the root of the arm, against which the 
said root R, called ptena, rested. The grain of the wood 
in the parastae and antistae was perpendicular; and tenons 
from the top and bottom of both entered the peritretae, to 
secure them thereto. All the angles and joints of the whole 
capitule were fortified with iron plates. 
The peritreta in this engine was made of a rhomboidal 
figure, in order to permit the arms to diverge the more. 
Heron describes it thus:—In a rectangular parallelogram 
a be d. Fig. XCIX. whose breadth is half its length, a dia- 
gonal line a e is dravn; parallel to which is davn Be; 
da is continued to e; then ae be shews the figure of the 
peritreta: the ends ae and be being swelled in a curve, 
to frengthen it. Again, drawing ee, the intersection / 
of that line, wich the line a b, fhews the middle of the 
peritreta, where the hole of the tonus is bored. 
K 
B0 0 
Philo gives another rule for determining the obliquity 
or rhomboidal figure of the peritreta:—He says, divide 
a semicircle into eleven parts, and from the fourth divilion 
draw a line to the center; which line shews the obliquity 
required. Vitruvius differs from both: he says the 
oblique formation should be a sixth part of the length, 
and a fourth of the breadth. 
The capitule of the balista being finished, the other 
members, answering to the syrinx, diostra, &c. of the 
catapulta, were added, as follows: To the timber MN, 
Fig. XCVIII. under the lower peritreta, was connected an 
horizontal frame of timber work ABC, Fig. C.; it consisted 
of several pieces of timber DD D, disposed at equal 
distances the whole length of the capitule, projecting for- 
wards, and being connected at their projecting ends by a 
transverse timber AB. This frame was called meysa, and 
by the Greeks trapeza; upon it was laid the covering of 
boards EEcalled tabula, whose upper surface was level with 
the bottom of the lower peritreta. Upon the tabula was 
placed the climas, or, as Vitruvius calls it, climaciclos, FGG, 
which was a horizontal frame of timber, similar to a 
ladder, whence it took its name; being composed of 
two longitudinal pieces GG and FK, connected by several 
transversal pieces HH, at proper distances. The breadth 
of the climax (according to Heron) was equal to the inter. 
val between the antistae; and the lengta nineteen holes 
according to Philo, although but thirteen according to 
Vitruvius. This climax answered to the syrinx of the 
catapulta, and lay upon the tabula, so as to project over 
each fide of the same. Upon the two parallel longi- 
tudinal pieces of the climax were laid two others, called 
ale. II and KK, of equal length and breadth; between 
which, and over the transverse pieces  H of the climas, 
was the diostra LLL, being equal in length to the 
climax. The climax was firmly fastened on the mensa, 
and secured by the anterides or braces MM, extending 
from the ends of the alae to the upper peritreta. 
The Cheira, Schasteria, &c. O P were fixed upon the
	        
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