In this form of lever the power is applied between the fulcrum and the weight to be raised.
The power is represented by the wing, the fulcrum by the air, and the weight by the body of the flying animal.
It consists of a steelyard mounted on a fulcrum; one arm carries at its extremity a heavy bob and pointer, the latter moving along a scale affixed to the stand and serving to indicate when the beam is in its standard position.
Although the third order of lever is particularly inefficient when the fulcrum is rigid and immobile, it possesses singular advantages when these conditions are reversed, that is, when the fulcrum, as happens with the air, is elastic and yielding.
4) a point in the steady mass b is used as the fulcrum for the short arm of a light-writing index.