measured by the fixed index 29, 30, which has a Nonius giving hundredth
parts of a degree at its extremity 30.
The whole particulars of the different parts of the above described
machine are represented in Plate VIII. as follow.
Fig. 2. Is the flat chain invented by Mr Vaucanson, and employed for
suspending the scale or bason P, Fig. 1; but, as this lengthens or
shortens according as it is more or less loaded, it would not have
answered for suspending the jar A, Fig. 1.
Fig. 5. Is the chain i k m, which in Fig. 1. sustains the jar A. This
is entirely formed of plates of polished iron interlaced into each
other, and held together by iron pins. This chain does not lengthen in
any sensible degree, by any weight it is capable of supporting.
Fig. 6. The trivet, or three branched stirrup, by which the jar A is
hung to the balance, with the screw by which it is fixed in an
accurately vertical position.
Fig. 3. The iron rod 26, 27, which is fixed perpendicular to the center
of the beam, with its box 28.
Fig. 7. & 8. The friction-wheels, with the plates of rock-cristal Z, as
points of contact by which the friction of the axis of the lever of the
balance is avoided.
Fig. 4. The piece of metal which supports the axis of the
friction-wheels.
Fig. 9. The middle of the lever or beam, with the axis upon which it
moves.
Fig. 10. The thermometer for determining the temperature of the air or
gas contained in the jar.
When this gazometer is to be used, the cistern or external vessel, LMNO,
Pl. VIII. Fig. 1. is to be filled with water to a determinate height,
which should be the same in all experiments. The level of the water
should be taken when the beam of the balance stands horizontal; this
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