The balance law and a water-driven mirror polisher
Weights on balance arms and oblique cords; a machine to grind steel mirrors
The mechanical notes give the law of the balance — weights that sustain one another are in inverse proportion to the arms of their balance — and analyse cords of different obliquity converging on a centre of gravity, working out that the less oblique cord d b feels a third less load than e r. At the foot of the sheet a detailed drawing shows an instrument, driven by running water, for flattening and then polishing flat mirrors of steel or other material. Balance-beam and cord diagrams hung with weights fill the rest of the page.
On this page
The law of the balance arms
Weights that sustain one another on a balance stand in the same proportion as the opposite arms of that balance. This is the inverse-proportion law of the lever, stated in the terms of counterpoised weights.
The less oblique cord feels more load
Among cords of different obliquity all meeting at the centre of a suspended weight, the least oblique feels the greatest load. Cord d b is less oblique than e r in the same measure that e r is more loaded: d b feels only 2 of the four pounds in the middle while e r feels 6, so e r carries a third more.
Water-driven machine to polish steel mirrors
A boxed mechanism of grinding wheels and gears is drawn as an instrument for flattening and then polishing flat mirrors, moved by the help of running water. The device automates the abrasive smoothing of a mirror surface.
Flat mirrors of steel
The instrument is meant to flatten and polish flat mirrors made of steel or of another composition, producing the true plane surface a reflecting mirror requires. A flawless flat face is what allows an undistorted reflection.