"It was maintained by many that the results of the experiments led to the greatest possible mechanical absurdities. For instance, it was maintained that, if friction were constant at all velocities upon a level railway, when once a power was applied to a carriage which exceeded the friction of that carriage by the smallest possible amount, that same small excess of power would be able to convey the carriage along a level railway at all conceivable velocities. When this position was put by those who opposed the conclusions at which my father had arrived, he felt great hesitation in maintaining his own views; for it appeared to him at first sight really to be--as it was put by his opponents--an absurdity. Frequent repetition, however, of the experiments to which I have alluded, left no doubt upon his mind that his conclusion that friction was uniform at all velocities was a fact which must be received as positively established; and he soon afterward boldly maintained that that which was an apparent absurdity was, instead, a necessary consequence. I well remember the ridicule that was thrown upon this view by many of those persons with whom he was associated at the time. Nevertheless, it is undoubted, that, could you practically be always applying a power in excess of the resistance, a constant increase of velocity would of necessity follow without any limit. This is so obvious to most professional men of the present day, and is now so axiomatic, that I only allude to the discussion which took place when these experiments of my father were announced for the purpose of showing how small was the amount of science at that time blended with engineering practice. A few years afterward, an excellent pamphlet was published by Mr. Silvester on this question; he took up the whole subject, and demonstrated in a very simple and beautiful manner the correctness of all the views at which my father had arrived by his course of experiments. "The other resistances to which carriages were exposed were also investigated experimentally by my father. He perceived that these resistances were mainly three--the first being upon the axles of the carriage; the second, which may be called the rolling resistance, being between the circumference of the wheel and the surface of the rail; and the third being the resistance of gravity.