XVIII
For applications see 122-129. Other examples are nut
crackers (II, a); a finger caught near the
hinge of a shutting door (II,a); the members
of our body, moved by the muscles (II,b).
The see-saw or balancing board, crow-
bar, pens, pencils etc. An application of
the bent-lever we see in the bell-crank.
§ 42. The most important application of the lever is the
Balance (for the different kinds and the conditions which must
be satisfied by a good balance see 123).
Remark. Archimedes (see 167, page 27) finding out the laws of the
lever exclaimed: “Give me a fulcrum and I can lift the earth”. The same
physicist found also the laws of an inclined plane and of the screw. (250
B.C.)
§ 43. 5) Pulley, 129. a.) The fixed pulley (No. 35, page
62) used for giving the power a more convenient direction; a
lever I. a.
b) The movable pulley No. 36. a lever II. a.
c) A combination of fixed and movable pulleys we see in
the Polyspast No. 37-39. By means of this machine we have
a saving of power in the proportion of 1 to the double number
