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? 126. Explain the barometer. Relate the incident given by Dr. Arnot. 127. Why would not a water-barometer answer? What is said of the barometer as a measurer of heights? How is the boiling point influenced by the amount of the air's pressure? Give the experiment with ether. 128. State the experiment with the flask. What would happen to liquids if the atmosphere were removed from the earth? Explain the operation of the syphon by Fig. 117. 129. Explain what is represented by Fig. 118. 130. Explain the uses of the syphon. Explain the operation of the Cup of Tantalus. 131. How are intermitting springs accounted for? Explain the operation of the common pump. 132. Why does the water rise in the pump? How is sucking done? Explain the forcing pump. 133. Explain the fire-engine. CHAPTER X. 134. What is said of the universality of motion? What of attraction as a cause of motion? What of heat? What of chemical agencies? What of life? 135. What is meant by saying that action and reaction are equal? State the illustrations of this truth which are given. Describe Barker's mill. 136. Give the comparisons to the operation of a spring, of firing of a cannon, and the throwing of stones from the crater of a volcano. What is said of the jumping of a man from the ground? 137. What is said of the reaction in the case of a hopping bird? Illustrate the inertia of matter as shown in the communication of motion. Give the illustrations of the fact that time is required to communicate motion to bodies. 138. Give illustrations of inertia as shown in the disposition of motion to continue. 139. Describe and explain the equestrian feat represented in Fig. 127. What is said of skill in jumping from a moving carriage? Relate the case in court which is stated. 140. What is said of the course of bodies thrown into the air? What of a man falling from a mast-head? 141. What is said of the atmosphere as revolving with the earth? What rapid motions are we subjected to when we speak of ourselves as at rest? Why are we insensible to these motions? 142. Follow out in full the comparison of the steamboat. What is the difference between absolute and relative motion? What is said of absolute rest? 143. Illustrate the truth that all the motions which are apparent to the eye are slight differences in the common absolute motions. What are the obstacles to motion? How is the motion of a stone thrown upward destroyed? What causes and what opposes its descent?