“It works tolerably well at high speeds; at low speeds it is useless; and then again there is a very rapid fluctuation, and the instrument is of only approximate precision.”
“Not it!” said I to encourage him.
“There is one exception,” he continued, “to this principle, and that is a speedometer which depends upon the introduction of resistance into a current generated by a small magneto. The faster the magneto turns the stronger the current generated, and the change is indicated upon a dial.”
“Yes,” said I sadly, “as in the former case so in this; the change of speed is indicated upon a dial.” And I sighed.
“But this method also,” he went on tenaciously, “has its defects.”
“You may lay to that,” I interrupted.
“It has the defect that at high speeds its readings are not quite correct, and at very low speeds still less so. Moreover, it is said that it slightly deteriorates with the passage of time.”
“Now that,” I broke in emphatically, “is a defect I have discovered in——”
But he put up his hand to stop me. “It slightly deteriorates, I say, with the passage of time.” He paused a moment impressively. “No one has hitherto discovered any system which will accurately record the speed of a vehicle or of any rotary movement and register it at the lowest as at the highest speeds.” He paused again for a still longer period in order to give still greater emphasis to what he had to say. He concluded in a new note of sober triumph: “I have solved the problem!”
I thought this was the end of him, and I got up and beamed a congratulation at him and asked if he would drink anything, but he only said, “Please sit down again and I will explain.”