appear, was nevertheless perfectly correct. The mere act of throwing a heavy body in any direction would have sufficed to set his own body traveling in the opposite direction. Of course the speed at which he would move would depend upon the weight of the body thrown, or rather upon its mass, since bodies in the car no longer possessed weight.
In other words, supposing some emergency to arise which would render it absolutely necessary for our hero to reach the side of the car, he could do this by resorting to the heroic expedient of cutting off his own arm and hurling it away from him with all his strength. A singular expedient, truly, but a most effective one; for, assuming his arm to be one tenth as heavy as the rest of his body, he would move in one direction with one tenth of the speed at which his arm was thrown in the opposite direction.
"It's some comfort," thought William, as he meditated over this curious plan, "to know that I could, if I wanted, reach the side of the car; but at present I hardly think it worth while to sacrifice one of my arms for no real advantage. If ever I get out of this fix alive, I want both my arms to come out with me. If only my jack-knife
