21.(Pg. [59]) Give a familiar example of the use of a lever of the first kind.
22.(Pg. [59]) In what instruments are two such levers combined?
23.(Pg. [59]) How may two horses of unequal strength, be advantageously coupled in a carriage?
24.(Pg. [60]) Describe a lever of the second kind. ([Fig. 6. plate 4.])
25.(Pg. [60]) What is represented in [fig. 7. plate 4], and in what proportion does this lever gain power?
26.(Pg. [60]) What is said respecting a door?
27.(Pg. [60]) Describe a lever of the third kind.
28.(Pg. [60]) In what instance do we use this?
29.(Pg. [61]) What remarks are made on its employment in the limbs of animals?
30.(Pg. [61]) What are the conditions of equilibrium in every lever?