In San Diego, there was great rivalry between the Army and the Navy. Witmer and Ellyson used to get up by sunrise and go over to the island and take out the old machine we used for teaching, which was nicknamed "Lizzy." They did this secretly because there was only one machine and they did not want the Army to smash it and so keep them down on the ground. After making their practice, they would go home and come back later, pretending that it was their first appearance. When the officers began their schooling they fell steadily into my way of looking at the problem, and not one of them spared himself bruised hands or grimy clothing. For the first ten days I did not offer them a chance even to give the motor its full power while they were in the aviator's seat. After they had worked around the aeroplane long enough, however, and were familiar with all its details, they were allowed to make "runs" over the half mile course, straight-away. That is, they took their seats in the machine in turn, the propeller was started, and the machine propelled along the ground on its wheels, like an automobile, without being able to rise. To prevent the machine rising while one of the men was in it, the throttle of the engine was so arranged that it only got half power, which was not sufficient to give it lifting power, but enough to drive it along on the ground at twenty or twenty-five miles an hour. This "grass cutting," as the boys soon dubbed it, gave them the opportunity to become used to the speed and the "feel" of the machine. It also taught them to steer a straight course by using the rudder and the front control, and to practise balance by the use of the ailerons. After a few days of these runs the throttle was given full vent, allowing full speed on the wheels, but the propeller was changed to one without the usual pitch. Thus, while the engine would drive the aeroplane at full speed on its wheels, this propeller did not have enough thrust to lift it from the ground. In this way the military pupils got the advantage of the speed, acquired balance, and adjusted their control to suit it, without the danger of getting up in the air too soon. A little later, when they had thoroughly accustomed themselves to these conditions, still another propeller was put on. This one had just sufficient pitch to lift the aeroplane from the ground, when well handled, and it would make "jumps" of from twenty to fifty feet at a height of a few inches or, perhaps, a few feet.