Ruth said: "What can that be?" I confessed I did not know. It came at regular intervals. When the car ran fast it was quick, when I slowed down it lessened in frequency but not in volume. I stopped and looked under the hood, but could find nothing amiss. So we continued on our way. It seemed to grow worse, and soon the whole car was shaken by the jar. Then I remembered I had never tested the valves to see if they leaked, so I again lifted the hood and dropped a few drops of oil on each of the valves in turn and started the engine up. Yes, that was the trouble, Nos. 2 and 4 were not quite tight. I was much pleased with myself, and when I had tightened them took my place at the wheel, congratulating myself on being such a good mechanic. Indeed, I did not think Ruth overstated the case when she said: "I think you are wonderful." But, alas! the noise and the jar continued, and I began to fear that some serious injury had been sustained. When I opened the hood once more I showed Ruth how to start the engine so that I could test the engine better than when it was at rest. I put my head down so near the cylinder that I nearly burned my ear, and found that there was no noise at all! I then told her to let in the clutch and let the car run on the road slowly. "I said 'slowly'!" I cried, as the motor nearly ran over me. So Ruth tried again. I hopped along by the side of the car as best I could, hearing the distressing noise more plainly than ever, coming, I was now convinced, from the interior of the cylinder. "We have broken a piston-rod," I said in a calm but desperate tone, "and the car will have to be laid up for an indefinite time to replace it." "But how could we break a piston-rod when we have met with no accident that could break anything?" exclaimed Ruth. Like a doctor who has diagnosed a case to his own satisfaction, I could afford to be patient with a layman, so I replied: "Well, you see there is sometimes a flaw in the metal, and the mere expansion and contraction by heat and cold may cause the metal to break without any concussion at all." It was a tiny village in which we had stopped, but all the inhabitants had assembled, and it was surprising to see how many of them there were! "What's the trouble?" said one. "A broken piston-rod," I replied tersely. Indeed, annoying as it was, I felt a certain pride in the gravity of the situation! I was like a man seized with a sudden pain in the night, whose trouble the doctor declares to be "appendicitis"; he is alarmed, but still has the satisfaction of feeling that the family will now know that he did not call them from their beds for a vulgar stomach-ache! I was about to inquire if there was any one in the village who had a horse which could tow us to the nearest garage, when Ruth remarked: "There is one funny thing about it----"