To these considerations we are naturally led when we envisage the fact that these very labor-saving machines are themselves created by other machines of like principles and scarcely inferior powers, such as we purpose to introduce to our readers, by a series of cuts, with some brief explanation of their uses and principles of action, in this present article. The unparalleled extension of rail-roads in this country, so peculiarly calculated for their creation by its natural configuration and geological structure, has called for a supply of rail-road materials, both raw and manufactured, to a degree almost inconceivable even at the present day; and so great have been the improvements recently introduced into machinery, so enormous the weight of the persons and freight to be transported, and so extraordinary the speed expected, and in fact demanded, by the traveling public, that nothing short of perfection in finish and strength will suffice, whether for marine engines, locomotives, or in fact, any power machines. This will easily be admitted when it is considered that on all the really good and well supported lines of road, in the Eastern states more especially, the rate of travel averages from thirty to fifty miles per hour, at an average cost to each passenger of about one-and-a-half cent per the mile of distance. We of course do not here take into account such miserable effete monopolies as some of our own interior, and some of the Southern roads, or that of the New Jersey Rail-Road and Transportation Company, the rates of which do not exceed fourteen miles to the hour, at a charge of something exceeding three cents per mile--since these are the exceptions to the rule, arising from the mistaken policy of the states through which they pass, in granting them exclusive privileges, enabling them with a minimum of speed, punctuality, civility, cleanliness, safety and comfort, to exact a maximum of fare from all who are so unfortunate as to be compelled to travel by them. These unimproved concerns, retrogressive in the very centre of the most brilliant progression, may, however, count their days as numbered, their unhallowed and enormous gains as arrested. The latter rail-road, never exceeding the average speed of good stage-coach travel, is now so seriously rivaled by heavy omnibuses running on a plank-road, that its locomotives to-day barely draw an average of three empty cars, where six weeks since they drew from eight to ten, filled to discomfort.