His whole form trembled.

He did not stop to think, he knew that if he were going to do anything effectual it must be in those few brief moments.
There are many ways to cripple an auto without damaging it, but Peter knew nothing of autos except that they went by gasoline.
In an emergency he would have slashed a tire even while the machine moved.

Now that he had a little time in which to think he hurried behind the auto and crawling beneath it turned on the outlet of the gas tank.
He knew that the tank was in back and that there must be a pipe leading from it.

He had intended to wrench the thin pipe away, when his groping, trembling fingers stumbled on the outlet cock.

This he turned on with as much terror as if he were setting fire to the universe.
Aghast at his own inspiration and boldness, he stood behind the car, shaking all over, as he heard the precious fuel running away in a steady stream and pattering on the road.