ItESISThNCES TO RAILWAY TR.4INS. 41 1 so that the advantage of a gradient of 4 feet per mile, over a gradient of 10 feet per mile (as estimated in 1838), was made to appear 160 per cent. more than the formula would show it to be. The formula, be it observed, appearing to agree with experiment, within the limits of this case.Again: the saving of friction of 1 lb. per ton, supposing, for the sake of argument, that such a saving would be attained by increasing the diameter of the wheels, instead of being a saving of 124 per cent. of the whole resistances on a level, at 40 miles per hour (as it would be, were the resistances constant at allvelocities, and therefore the same at 1 mile per hour as at 10 miles per hour), would in practice be a saving of only 4 per cent. of such resistances, since such resistances (in a train of 80 tons, as assumed by Mr. Brunel) would have increaeed a t 40 miles per hour to 25 lbs. per ton.I n giving these examples, it is wished that it should be understood, that the author does not give any opinion in the present place, as to the relative advantages of different diameters of wheels, or of different gradients or gauges. These arguments, by which particular tmangements were defended, are selected in order to show the appli-..:.ition of the law of increase of resistances with the velocities, to the (*Jestions discussed, merely because they were the best practical examples of the importance of determining the true value of' resistauces to trains at various velocities which occurred to the author.A glance indeed at a few of the applications of this important question of the variations of resistances, will satisfy every engineer, that it is no mere theoretical question, but one which is of the most direct practical bearing. This Paper is illustrated by two sheets of diagrams, I. and 11.Mr. HARDING reiterated the explanation of the diagrams given in the paper, and showed, that the resistance per ton to a passenger train of about 30 tons, at a velocity of 60 miles per hour, would appear to be upwards of 401bs. per ton, instead of 18 Ibs. per ton, as had been stated as the results of other experiments, whose correctness might, he contended, be reasonably questioned.
Mr