VITRUVIUS. 
may bequal, it is there to be boundand comneded vich cord to the lowver tochlea; and both 
patsoftherope o fastened, hat neiherthe rigkt northeleft part mayescape. Then the endsof 
therope are caried to the outward fide of the ligher trochlea (ch and thrown round the under 
pullers (): returning then to the bottom, they are pafsed round the pulleys of thelover 
trochlea () on the inner fide, and thence caried on the right and left to the top of the 
uoper pulles e) of the ligher trochlea; and, being throvn over from the outer ide, are re- 
fered to the aris on the right and lest of the tympanum, where they are securely hred. 
Then winding another rope round the tympanum, it is continued to the capstan (N), which 
by its motion turning the tympanum and axis, the ropes that are fastened to the axis are by 
these means extended; and thus the weight (0) is gently, and without danger, elevated. But 
if a larger tympanum be placed either in the middle or at one end, without having a capstan, 
the work may be more expeditiously performed, by the walking of men therein. 
(1*) The use of this ruler is not explained by Vitru¬ 
vius; but it probably is to support the upper trochlea 
at a little distance from the beam, so as to admit the 
pulleys to revolve easily, and also to give room for the 
CHAPTER 
Of another Kind of Tractorial Machine. 
HERE is another kind of machine, ingenious enough, and expeditious in 
use ; but it cannot be trusted in the work, except to those who are skilful. It is a beam (4) 
that is erected and held by retinacula (I) four different ways: below the retinacula two 
chelons (E) are fixed ; a trochlea (C) is bound with ropes upon the chelons; under the 
trochlea is put a ruler (D) about two feet long, six digits broad, and four thick. The trochleas 
have three rows of pulleys in breadth; so that three drawing ropes are bound to the top of 
the machine: these are carried to the lower trochlea (L), and thrown over its upper pulleys 
from the inner side; then referred to the higher trochlea (C), and thrown round its under pul- 
leys from the outer to the inner side, when they descend to the lower (trochlea); and passing 
drawing ropes to pass between the trochlea and the beam. 
(2*) It appears by the description that the trochleas of 
this machine have three rows of pulleys in height, as well 
as three in breadth.