THE LIQUID STATE 6S
although less accurately, by makiug use of Mohr's or Wettphal'i balance. This instrument is shown in fig. 10. The part of the beam to the right is graduated and carries at its extremity a link from which a thermometer- sinker is suspended. When the sinker is attached the balance is in equilibrium. If now the sinker be immersed in distilled water at 15°C, the equilibrium is, of course, disturbed, and to re-establish the equilibrium it is necessary to hang a
��weight on to the link equal to the weight of the water displaced by the sinker. This weight is the unit weight of the system.
A series of weights in the form of riders of the respec- tive values 10, 0*1, 0*01, may be placed on the graduated part of the beam.
Suppose the sinker to be immersed in a liquid denser than water, then the following arrangement of the riders (for example) would be necessary : (1) the weight 1, sus- pended on the link — value = 1-000 ; and (2) other weights distributed at different points of the beam :
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