"Yes, that is a double-acting or reciprocating engine of a more perfect type," her father returned. "Mechanics and engineers went on improving Watt's engine just as he had improved those that had preceded it. It is interesting, too, to notice that after thousands of years scientists have again worked around to the steam turbine described so long ago in the Alexandrian records. This engine, although it does away with many of the moving parts introduced by Newcomen, preserves the essential principles of that early engine combined with Watt's later improvements. To-day we have a number of different kinds of engines, their variety differing with the purpose to which they are applied. Their cost, weight, and the space they require have been reduced and their power increased, and in addition we have made it possible to run them not only by means of coal or wood but by gasoline, oil, or electricity. We have small, light-weight engines for navigation use; mighty engines to propel our great warships and ocean liners; stationary engines for mills and power plants; to say nothing of the wonderful locomotive engines that can draw the heaviest trains over the highest of mountains. The principle of all these engines is, however, the same and for the brain behind them we must thank James Watt." "Was it Watt who invented the locomotive, too?" ventured Doris. Her father shook his head. "The perfecting of the locomotive, my dear, is, as Kipling says, another story." "Tell it to us." "Not now, daughter," protested Mr. Tolman. "I am far too hungry; and more than that I am eager to enjoy this beautiful country and forget railroads and locomotives." "Did you say you were hungry, Henry?" asked Mrs. Tolman. "I am--starved!" her husband said apologetically. "Isn't it absurd to be hungry so early in the day?" "It is nearly noon, Dad!" said Steve, glancing down at the clock in the front of the car. "Noon! Why, I thought it was still the middle of the morning." "No, indeed! While you have been talking we have come many a mile, and the time has slipped past," his wife said. "If all goes well--" The shot from a bursting tire rent the air. "Which evidently it does not," interrupted Mr. Tolman grimly, bringing the car to a stop. "How aggravating! We were almost into Palmer, where I had planned for us to lunch. Now it may be some little time before we can get anything to eat." "Motorist's luck! Motorist's luck, my dear!" cried Mrs. Tolman gaily. "An automobilist must resign himself to taking cheerfully what comes." "That is all very well," grumbled her husband, as he clambered out of the car. "Nevertheless you must admit that this mishap on the heels of the other one is annoying." Stephen also got out and the two bent to examine the punctured tire. "I should not mind so much if I were not so hungry," murmured Mr. Tolman. "How are you, Steve? Fainting away?" The boy laughed. "Well, I could eat something if I had it," he confessed.