Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667

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1Rope about the Axis of a Crane did not only hold it, that be­
ing drawn by the immenſe force of the weight, which it held, it
ſlipt nor ſhrunk not; but that moreover turning the Crane about,
the ſaid Axis with the ſole touch of the Rope which begirteth it,
did in the after-turnings, draw and raiſe up vaſt ſtones, whilſt the
ſtrength of a little Boy ſufficed to hold and ſtay the other end of
the ſame Cord.
The other is at a plain, but cunning, Inſtrument found
out by a young Kinſman of mine, by which with a Cord he could
let himſelf down from a window without much gauling the palmes
of his hands, as to his great ſmart not long before he had done.

the better underſtanding whereof, rake this Scheame: About ſuch
a Cylinder of Wood as A B, two Inches
thick, and ſix or eight Inches long, he cut a
hollow notch ſpirally, for one turn and a
54[Figure 54]
half and no more, and of wideneſſe fit for
the Cord he would uſe; which he made to
enter through the notch at the end A, and
to come out at the other B, incircling after­
wards the Cylinder in a barrel or ſocket of
Wood, or rather Tin, but divided length­
waies, and made with Claſpes or Hinges to
open and ſhut at pleaſure: and then graſp­
ing and holding the ſaid Barrel or Caſe with
both his hands, the rope being made faſt
above, he hung by his arms; and ſuch was
the compreſſion of the Cord between the
moving Socket and the Cylinder, that at
pleaſure griping his hands cloſer he could
ſtay himſelf without deſcending, and ſlacking his hold a little, he
could let himſelf down as he pleaſed.
An Hand-Pully
or Inſtrument in­
vented by an ama­
rous perſon to let
himſelf down from
any great height
with a Cord with­
out gauling his
SALV. Aningenious invention verily, and for a full explanati­
on of its nature, me-thinks I diſcover, as it were by a ſhadow, the
light of ſome other additional diſcoveries: but I will not at this
time deviate any more from my purpoſe upon this particular: and
the rather in regard you are deſirous to hear my opinion of the
Reſiſtance of other Bodies againſt Fraction, whoſe texture is not

with threads, and fibrous ſtrings, as is that of Ropes, and moſt
kinds of Wood: but the connection of their parts ſeem to de­
pend on other Cauſes; which in my judgment may be reduced to
two heads; one is the much talked-of Repugnance that Nature
hath againſt the admiſſion of Vacuity: for another (this of Va­
cuity not ſufficing) there muſt be introduced ſome glue, viſcous
matter, or Cement, that tenaciouſly connecteth the Corpuſcles of
which the ſaid Body is compacted.
Why ſuch Bodies
reſiſt Fraction that
are not connected
with Fibrous fila­
I will firſt ſpeak of Vacuity, ſhewing by plain experiments,

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