Galilei, Galileo - Mechanics

Galilei, Galileo, Mechanics, 1665

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Specifical Gravity of the Silver, as the Maſs of the Silver hath to
the Maſs of the Gold; that is, as the difference betwixt the
Weight in Water and Weight in Air of the Silver, hath to the
difference betwixt the Weight in Water and Weight in Air of
the Gold.

With this ſame Ballance one may with facility meaſure the
Maſs or Magnitude of any Body, in any manner whatſoever Irre-
gular in manner following, namely:

We will have at hand a Solid Body of a ſubſtance more grave
in Specie than the Water; as for inſtance of Lead; or if it were
of Wood, or other matter more light in Specie than the Water,
it may be made heavier by faſtning unto it Lead, or ſome other
thing that makes it ſink in the Water, and let us take ſome
known Meaſure, and with it meaſure the Irregular Solid; as for
inſtance, the Roman Palm, the Geometrical Foot, or any other
known meaſure, or part of the ſame, as the half Foot, the quar-
ter of a Foot, or any ſuch like part known; then let it be weighed
in the Air, and ſuppoſe that it weigh 10 pounds; let the ſame
Meaſure be weighed in the Air, and ſuppoſe that it weigh 8
pounds: and ſubſtract 8 pounds, the Weight in the Water, from
10 pounds, the Weight in the Air, and there remaineth 2 pounds
for the Weight of a Body of Water equal in Magnitude to the
Meaſure known. Now, if we would meaſure a Statue of Mar-
ble, let it be weighed firſt in the Air, and then in the Water, and
ſubſtract the Weight in the Water from the W eight in the Air, and
the remainder ſhall be the weight of ſo much Water as equalleth
the Statue in Maſs; which being divided by the difference betwixt
the W eight in Water and the W eight in Air of the Meaſure known,
the Quotient will give how many times the Statue containeth the
ſame given Meaſure. As for example; if the Statue in Air weigh
100 pounds, and in the Water 80 pounds, 80 pounds being ſub-
ſtracted from 100 there reſteth 20 pounds for the W eight of ſo
much Water in Maſs as equalleth the Statue. But becauſe the
difference betwixt the W eight in Water, and the W eight in Air
equal in Magnitude to the Meaſure known, was ſuppoſed to be
2 pounds; divide 18 pounds by two pounds, and the Quotient
is 9, for the number of times that the propoſed Statue containeth
the given Meaſure. The ſame Method may be obſerved, if it
were required, to meaſure a Statue, or other Maſs of any kind of
Metal: only it muſt be advertiſed, that all the holes muſt be
ſtopt, that the Water may not enter into the Body of the Statue:
but he that deſireth only the Solid content of the Metal of the
ſaid Statue muſt open the holes, and with Tunnels fill the whole
cavity of the Statue with Water. And if the Statue were of a
Subſtance lighter in Specie than the Water; as, for example, of

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