An Explication of the Third PLATE.
Figure 1. Is a Tube full of Water, with Two Holes E, F, for the Water to
run out at, the one F four times as much below the Surface of the Water
A B as the other; (the Vessel to be still kept equally full all along:) to
shew that the Velocity and Quantity of Fluids that run out, are in only a
subduplicate Proportion of the Altitude of the Fluids, or twice so much in
a Fourfold Altitude. Not can it be otherwise: For twice the Quantity
running out, with twice the Velocity, implies the Force or Pressure to be
Fourfold, as the Fourfold Altitude requires; and so for ever.
_Fig. 2._ Is a Pump; where G M is a hollow Cylinder, reaching to the Water
below, with a Valve G, which will be lift up by the ascending Water, and
permit its Entrance into the Body of the Pump; but will not permit its
Return when it is attempting to descend. D is the Sucker, with its hollow
Cylinder, and a like Valve: which Sucker is pulled upward or thrust
downward by the Handle I L K. When it is pulled upward, it leaves the Body
of the Pump a Vacuum: whence the Air's Pressure on the Water's Surface
below raises it up into that Space, and fills it; and when it is thrust
down, the Water, which is stopp'd by the lower Valve from going back, is
forc'd through the Valve in the Sucker D, into the Cistern above; whence
by its own Gravity it runs out at the Canal A C.
_Fig. 3._ Is a Forcing Pump, in the main made like the other, only without
a Cistern; and the Exit is out of the Side through a Hole, with a Valve
opening outward, but shutting inward, in which the Sucker when thrust
downwards forces the Water out sideways with great Violence.
_Fig. 4._ Is _Archimedes_'s Spiral Pump C D, made of only a Cylinder, with
a hollow Spiral Tube wreath'd about it; where the Fluid partly descending,
and partly ascending, all the way, makes its flowing along the more easy,
till upon its Arrival at the Top it runs out at C.
_Fig. 5._ Is the whole Apparatus of the Hydrostatical Balance. The Glass
Bubble G is heavier than all Fluids but Quicksilver, and is to be put into
all those Fluids: The Bulk of Water in ours is 830 Grains _Troy_. If when
pois'd in Water it sink more by any Number of Grains, that Number of
Grains substracted from; if less, added to those 830, do by their
Proportion to 830 give the Specifick Gravity of all such Fluids to Water.
I K is the Glass Bucket, which in Air is in Æquilibrio with the Scale E:
And because when it is let into Water, it will be no longer an Equipoise
to the opposite Scale, but lighter; the Scale R is to be added to the Part
H, by which the Bucket is suspended, and that will restore the Æquilibrium
in Water. By this Solids and Quicksilver are weighed first in Air, and
then in Water: The Difference of which Weights being the Weight of an
equal Bulk of Water, by its Proportion to the first Weight in Air, gives
the Specifick Gravity of the Solid compared with Water: And if that
Difference still divide the Weight in Air, for all sort of Bodies, we may
have a Table of the Specifick Gravities of the Solids; as by dividing 830
by the Sum or Difference of the other Fluids, we may have a like Table of
the Specifick Gravity of Fluids, such an one as here presented the Reader.