I'm working on my literature test. Can anyone help me to understand one of his expression?
That is an excerpt from Thoreau work "Life without principle"
Most men would feel insulted, if it were proposed to employ them in throwing stones over a wall, and then in throwing them back, merely that they might earn their wages. But many are no more worthily employed now. For instance: just after sunrise, one summer morning, I noticed one of my neighbors walking beside his team, which was slowly drawing a heavy hewn stone swung under the axle, surrounded by an atmosphere of industry,--his day's work begun,--his brow commenced to sweat,--a reproach to all sluggards and idlers,--pausing abreast the shoulders of his oxen, and half turning round with a flourish of his merciful whip, while they gained their length on him.
What did he mean by "they gained their length on him" ?