CHAP. VIII.
Of the Skrew and its Circles or Worm, and in what Manner great Weights
are either drawn, carried or puſhed along.
are either drawn, carried or puſhed along.
We have already treated of Wheels, Pul
lies and Leavers; we are now to pro
ceed to the Skrew. A Skrew conſiſts of a
Number of Circles like Rings, which take up
on themſelves the Burthen of the Weight. If
theſe Rings were entire, and not broken in
ſuch a Manner, that the End of one of them is
the Beginning of the other; it is certain the
Weight which they ſupport, though it might
be moved about, would neither go upwards nor
downwards, but evenly round upon an equal
Plain according to the Direction of the Rings:
The Weight therefore is forced to ſlide either
upwards or downwards along the Slope of the
Rings, which act herein after the Manner of
the Leaver. Again, if theſe Rings or this Worm
be of a ſmall Circumference, or be cut in too
near to the Center of the Skrew, the Weight
will then be moved by ſhorter Leavers and
with a ſmaller Force. I will not here omit one
Thing which I did not think to have menti
oned in this Place: Namely, that if you could
ſo order it that the Bottom or Keel of any
Weight which you would move might (as far
as could be done by the Art and Skill of the
Workman) be made no broader than a Point,
and be moved in ſuch a Manner upon a firm
and ſolid Plain as not in the leaſt to cut into
it, I would engage you ſhould move Archi
medes's Ship, or effect any thing elſe of this
Nature whatſoever. But of theſe Matters we
ſhall treat in another Place. Each of theſe
Forces in particular, of which we have already
ſpoken, are of great Power for the moving of
any Weight; but when they are all joined to
gether, they are vaſtly ſtronger. In Germany
you every where ſee the Youth ſporting upon
the Ice with a ſort of wooden Pattens with a
very fine thin Bottom of Steel, in which with
a very ſmall Strain they ſlip over the Ice with
ſo much Swiftneſs, that the quickeſt flying
Bird can hardly out-go them. But as all Weights
are either drawn, or puſhed along, or carried,
we may diſtinguiſh them thus: That they are
drawn by Ropes; puſhed along by Leavers;
and carried by Wheels, Rollers and the like:
And how all theſe Powers may be made uſe of
at the ſame Time, is manifeſt. But in all theſe
Methods, there muſt of Neceſſity be ſome one
Thing, which ſtanding firm and immoveable
itſelf, may ſerve to move the Weight in Queſ
tion. If this Weight is to be drawn, there muſt
be ſome greater Weight, to which you may
faſten the Inſtruments you are to employ; and
if no ſuch Weight can be had, fix a ſtrong iron
Stake of the Length of three Cubits, deep in
to the Ground which muſt be rammed down
tight all about it, or well ſtrengthened with
Piles laid croſs-ways: And then faſten the
Ropes of your Pullies or Cranes to the Head
of the Stake which ſtands up out of the Ground.
If the Ground be ſandy, lay long Poles all the
Way for the Weight to ſlide upon, and at the
Head of theſe Poles faſten your Inſtruments to
a good ſtrong Stake. I will take Notice of
one Thing which the Unexperienced will never
allow, till they underſtand the Matter thorough
ly; which is, that along a Plain it is more con
venient to draw two Weights than one; and
this is done in the following Manner: Having
moved the firſt Weight to the End of the
Timbers laid for it to ſlide upon, fix it there
with Wedges in ſuch a Manner that nothing
can ſtir it, and then faſten or tie to it the En
gines, or Inſtruments with which you are to
draw your other Weight; and thus the move
able Weight will be overcome and drawn along
the ſame Plain by the other Weight, which is
no more than equal to it, but only that it is
fixed. If the Weight is to be drawn up on high,
we may very conveniently make uſe of one
ſingle Pole, or rather of the Maſt of a Ship;
but it muſt be very ſtout and ſtrong. This
Maſt we muſt ſet upright, faſtening the Foot
of it to a Stake, or fixing it ſtrong in any other
Manner that you pleaſe. To the upper End of
it we muſt faſten no leſs than three Ropes, one
on the right Side, another on the leſt, and the
other running down directly even with the
Maſt. Then at ſome Diſtance from the Foot
of the Maſt fix your Capſtern and Pullies in
the Ground, and putting this laſt Rope through
the Pullies, let it run through them ſo as to
draw the Head of the Maſt a little downwards,
lies and Leavers; we are now to pro
ceed to the Skrew. A Skrew conſiſts of a
Number of Circles like Rings, which take up
on themſelves the Burthen of the Weight. If
theſe Rings were entire, and not broken in
ſuch a Manner, that the End of one of them is
the Beginning of the other; it is certain the
Weight which they ſupport, though it might
be moved about, would neither go upwards nor
downwards, but evenly round upon an equal
Plain according to the Direction of the Rings:
The Weight therefore is forced to ſlide either
upwards or downwards along the Slope of the
Rings, which act herein after the Manner of
the Leaver. Again, if theſe Rings or this Worm
be of a ſmall Circumference, or be cut in too
near to the Center of the Skrew, the Weight
will then be moved by ſhorter Leavers and
with a ſmaller Force. I will not here omit one
Thing which I did not think to have menti
oned in this Place: Namely, that if you could
ſo order it that the Bottom or Keel of any
Weight which you would move might (as far
as could be done by the Art and Skill of the
Workman) be made no broader than a Point,
and be moved in ſuch a Manner upon a firm
and ſolid Plain as not in the leaſt to cut into
it, I would engage you ſhould move Archi
medes's Ship, or effect any thing elſe of this
Nature whatſoever. But of theſe Matters we
ſhall treat in another Place. Each of theſe
Forces in particular, of which we have already
ſpoken, are of great Power for the moving of
any Weight; but when they are all joined to
gether, they are vaſtly ſtronger. In Germany
you every where ſee the Youth ſporting upon
the Ice with a ſort of wooden Pattens with a
very fine thin Bottom of Steel, in which with
a very ſmall Strain they ſlip over the Ice with
ſo much Swiftneſs, that the quickeſt flying
Bird can hardly out-go them. But as all Weights
are either drawn, or puſhed along, or carried,
we may diſtinguiſh them thus: That they are
drawn by Ropes; puſhed along by Leavers;
and carried by Wheels, Rollers and the like:
And how all theſe Powers may be made uſe of
at the ſame Time, is manifeſt. But in all theſe
Methods, there muſt of Neceſſity be ſome one
Thing, which ſtanding firm and immoveable
itſelf, may ſerve to move the Weight in Queſ
tion. If this Weight is to be drawn, there muſt
be ſome greater Weight, to which you may
faſten the Inſtruments you are to employ; and
if no ſuch Weight can be had, fix a ſtrong iron
Stake of the Length of three Cubits, deep in
to the Ground which muſt be rammed down
tight all about it, or well ſtrengthened with
Piles laid croſs-ways: And then faſten the
Ropes of your Pullies or Cranes to the Head
of the Stake which ſtands up out of the Ground.
If the Ground be ſandy, lay long Poles all the
Way for the Weight to ſlide upon, and at the
Head of theſe Poles faſten your Inſtruments to
a good ſtrong Stake. I will take Notice of
one Thing which the Unexperienced will never
allow, till they underſtand the Matter thorough
ly; which is, that along a Plain it is more con
venient to draw two Weights than one; and
this is done in the following Manner: Having
moved the firſt Weight to the End of the
Timbers laid for it to ſlide upon, fix it there
with Wedges in ſuch a Manner that nothing
can ſtir it, and then faſten or tie to it the En
gines, or Inſtruments with which you are to
draw your other Weight; and thus the move
able Weight will be overcome and drawn along
the ſame Plain by the other Weight, which is
no more than equal to it, but only that it is
fixed. If the Weight is to be drawn up on high,
we may very conveniently make uſe of one
ſingle Pole, or rather of the Maſt of a Ship;
but it muſt be very ſtout and ſtrong. This
Maſt we muſt ſet upright, faſtening the Foot
of it to a Stake, or fixing it ſtrong in any other
Manner that you pleaſe. To the upper End of
it we muſt faſten no leſs than three Ropes, one
on the right Side, another on the leſt, and the
other running down directly even with the
Maſt. Then at ſome Diſtance from the Foot
of the Maſt fix your Capſtern and Pullies in
the Ground, and putting this laſt Rope through
the Pullies, let it run through them ſo as to
draw the Head of the Maſt a little downwards,