a wish to satisfy public curiosity, and render the illustration of their properties clear and comprehensive. CHAPTER IX.-Contains an outline of the comparative performance of the different available species of motive power in the conveyance of goods by Canals and Railroads. Tables have been given, explanatory of the weight of goods which horses can convey, at different rates of speed, upon Canals and upon Rail-roads; and, also, the weight which horses can convey on Canals, and which loco-motive engines can drag upon Rail-roads. The performance of the latter will, also, represent the effect with any other species of mechanical power on Rail-Roads, the energy of which corresponds with that assigned to the locomotive engines. These particulars, therefore, comprehend an outline of the matter contained in the work, which, I trust, will be found generally useful. Many subjects yet require elucidation and enquiry; in particular, Experiments are required to ascertain what part of the friction of carriages arises from the attrition upon the axles, and how much from the rolling of the wheels upon the rails; I intended to have made this the subject of early application to experiment; but, considering the necessity of the speedy appearance of the Work, to meet the public anxiety, I did not conceive it proper to delay the appearance of this work until I could obtain an opportunity of making these Experiments. It will be seen, from the Experiments on the strength of rails, that considera ble deflexion was produced in the malleable iron-rails, when loaded with heavy weights. Considering the difference of opinion, as to their utility, compared with cast-iron, it is a subject of no trifling interest whether this bending tends, in any degree, to affect the resistance of carriages moved along the malleable iron-rails. I had prepared apparatus to determine this point, but have, for the present, been obliged to delay it, for the reasons previously stated. KillingwortH, A PRACTICAL TREATISE ON RAIL-ROADS.. CHAPTER 1. INTERNAL COMMUNICATION. THE Romans, it is probable, were the first who made any regular roads in Great Britain; for the purpose of facilitating the subjection of the inhabitants, and to secure a communication at all times between their armies occupying different quarters of the island; they formed what are now termed " military roads," which consisted of paths stretched across the country, from one place to another, and paved with large stones. These were generally of very considerable lengths, and made to pursue a straight line from station to station, thus affording a hard, durable, and safe road, infinitely superior to the swampy, soft, and marshy paths, indiscriminately formed in all parts of the country, by its early inhabitants. Many of these roads are yet in existence in various places; and, as may be expected, from the purposes for which they were originally intended, they are very uneven and undulating. Their direction being froin one station to another, which were generally placed upon the most elevated parts of the country, for the purpose of watching the motions of the enemy, these roads invariably avoid the more level parts of the country, and stretch from hill to hill. For many centuries after the invasion of the island by the Romans, articles of trade were transported from one place to another, upon the backs of horses, which were called, "Packhorses." Even so late as the middle of the last century, almost the whole land-carriage of Scotland, and of several parts of England, were conveyed on the backs of horses; and we find, at the present day, in most of the mountainous parts of Wales, and in the highlands of Scotland, the whole traffic carried on by the same mode of carriage. The paved and hard roads of the Romans would afford a comparatively good track for horses, but as the inhabitants advanced in civi |