117. What is said of the Magdeburg hemispheres? Give the experiment with mercury. Explain the operation of the boy's sucker.
118. Give the statements about sucker-like arrangements in animals. State the experiment of the bladder and weight. Give the experiment with the India-rubber bag.
119. State the experiment with the egg. Explain the operation of the hydrostatic balloon.
120. Explain the operation of the Cartesian image. What is said of the presence of air in various substances?
121. What is said of the elasticity of air? Describe and explain the condenser.
122. Describe and explain the gasometer. Show how the air-gun operates. Explain the pop-gun.
123. Explain the operation of gunpowder. Explain that of steam. What is said of retardation by condensed air in gunnery?
124. Describe and explain what is represented in Fig. 113. Explain the collection of gases in the pneumatic trough.
125. Explain the experiment represented in Fig. 115. What is said of tapping a barrel? What causes the gurgling sound when a liquid is poured from a bottle? How high a column of water will the pressure of the atmosphere sustain? How do you find from this the pressure of the air on every square inch of surface? How high a column of mercury will the atmosphere sustain?