Samuel Smiles, The Life of George Stephenson and of his Son Robert Stephenson
“ I mean to say, that if it would bear the weight at four miles an hour, it would bear it at twelve." "Taking it at four miles an hour, do you mean to say that it would not require a stronger railway to carry the same weight twelve miles an hour?" "I will give an answer to that. I dare say every person has been over ice when skating, or seen persons go over, and they know that it would bear them better at a greater velocity than it would if they went slower; when they go quick, the weight in a measure ceases." "Is not than upon the hypothesis that the railroad is perfect?" ”
