They now started the engine, Tom climbed in, and they were off, running over the soft ground at increasing speed.  Then the airplane struck a pool of water, five or six inches deep, which almost pulled them up. It also held them back so that when the machine emerged it was going very little faster than at the beginning.  The next patch of ground was a little longer, but they had not risen when they struck it at a rate of about twenty-five miles an hour.