Hydrostatics.

299

following Instances ; having first pre-mised, (what is found by Experiment)that a Cubic Foot of comtnon Water weighs

very

pofe. This Wire r s is covered with Paper graduatedby equal Divisions, and is about five Inches long.

28. In the Corner of the Table at E is fixed a BrassTube, in which a round Wire h / is so adapted as tomove neither too hard nor too freel by its flat Head I.Upon the lower Part of this moves another Tube Q_which has Friction enough to cause it to remain in anyPosition required ; to this is fixed an Index T, movinghorizontally when the Wire h I is turned about, andtherefore may be easily set to the graduated Wire r s.

29. To the lower End of the Wire r s hangs aWeight L, and to that a Wire f n with a small BrassBall g, about - 4 of an Inch in Diameter. On the otherSide, to the Wire a c hangs a large Glass Bubble R bya Horse-hair. Let us at present suppose the Weight Ltaken away, and the Wire p n suspended from S ; andon the other Side let the Bubble R be taken away, andthe Weight F suspended in its Room at c. ThisWeight P we suppose to be such as will keep in Equi-libria with the several Parts appended to the other Scale,at the fame Time that the middle Point of the Wire

n is in the Surface of the Water in the Vessel N.

30. The Wire p ■« is 'to be of such a Size, that theTength of one Inch shall weigh four Grains. Henceit is evident, since Brass is eight Times heavier thanWater, (fee Art. rb.) that for every Inch the Wiresinks in the Water, it will become half a Grain lighter,and half a Grain heavier for every Inch it rises out ofthe Water: Consequently, by sinking two Inches belowthe middle Point, or rising two Inches above it, theWire will become one Grain lighter or heavier.

31. And therefore, if when the middle Point is atthe Surface of the W a ter in Equilibria , the Index T be'set to the midd'e Point a of the graduated Wire r s,and the Distance on each Side a r and a s containJOQ equal Parts j then, when in weighing Bodies the

Weight