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cause it was accidentally found to suit the object; he would have aright, therefore, to call on me to produce a short road, and show thatthe results still correspond with my calculation. His intellect mightnot yet be fully satisfied; it would be fair for him to call for anotherexample, in which the trade and travel were both unusually great, inorder to be assured that the method is applicable to works of thatcharacter also ; and, even after finding this result to be confirmatoryof the method, extreme prudence would dictate an additional appli-cation to another road with very small trade.

All this appearing satisfactory, he could not well retain a doubt;but, when men stake their fortunes, and the comfort and indulgenceof their families on the issue, they have a right—they are bound—toexercise great circumspection. Such a party might, therefore, wellcall for an application of the method to an old road —or to one thathas arrived at maturity, at least,—in order to see whether his invest-ment is likely to be permanently good.

If this doubt be also satisfied; if he finds that the application maybe safely made to a road of this description; if, in addition, it is madeto one of this sort with a great trade—next, to one with a small trade—then to one with great travel and no tonnage ; afterward to a longone, and, finally, to a short one; to some roads with light, and toothers with heavy grades—and, if he find that it gives consistent re-sults in all these varied applications—as a reasonable, and as an in-telligent man, he will be compelled to admit, that the method is inaccordance with the law, and that its results are the truth.

It is such testimony that I propose to offer the reader, and I solicithis attention in order that he may judge fairly of my consistency—forconsistency is a test of truth.

The following propositions are what I designate as Laws:—

I. The cost of motive power, with engines of the same class, is pro-portional to the distance which the engines run. The cost per mileis nearly the same on roads of all grades—the difference in expenseon roads with different grades, consists not essentially in variations ofthe cost per mile run, but in variations of the number of miles whichmust be performed to do the same duty.

II. The repairs of the road, with equal trade, are proportional toits length ; that is to say, cseteris paribus, it costs twice as much tokeep up a road 200 miles long, as it does to maintain one in the samecondition, of which the length is 100 miles ; just as it costs twice asmuch to run engines 200,000 miles, as it would to run the same classof engines 100,000 miles.

III. The repairs of cars are proportional to the number of tons con-veyed, and to the distance to which they are conveyed. It costs twiceas much to repair cars which run two millions, as it does those whichrun one million of miles per annum. Again, it costs twice as muchto repair cars which convey 20,000 tons a given distance, as it doesthose which convey 10,000 tons the same distance. The same prin-ciple applies equally to the conveyance of passengers; it applies alsoto accidents, incidentals, and contingencies—for these things increasewith, and are proportional to, the increase of business.