speed, one day would do the work of four. The heaviest commodities, such as corn, potatoes, coals, &c. would bear the expense of carriage for a hundred miles; the expense of living in great towns would be reduced, and the price of raw produce would rise in remote parts of the country. Again," with so great a facility and celerity of communication, the provincial towns of an empire would become so many suburbs of the metropolis, or rather, the effect would be similar to that of collecting the whole inhabitants into one city."-Scotsman Newspaper. Another great source of revenue and of trade, from this improved mode of intercourse, (observes the Quarterly Review) would arise from the conveyance of those fine goods, parcels of value, and all light articles, where speed and certainty are required; and which are now sent, at great expense, by coaches. In this manner the seats of the various finer and lighter manufactures would be brought almost into immediate contact with the great markets for their disposal. A merchant in London, on receiving any particular order, might send either to Nottingham, to Birmingham, or to Sheffield, or even to Manchester or Leeds, and have the goods in his shop the next or following day, at an expense not exceeding 1s. 6d. or 2s. Lastly, the rapid circulation of intelligence. The mails might travel safely at 25 miles an hour, and letters be conveyed between London and Edinburgh, a distance of 400 miles, in 18 hours; so that an event happening in London, would be known in Edinburgh the same day. As an example of the difficulties of internal navigation, before the introduction of steam for that purpose, it may be mentioned that, on the great river Mississippi, which flows at the rate of five or six miles an hour, it was the practice of the boatmen, who brought down the produce of the interior to New Orleans, to break up t with ease, in 15 Why are the locomotive break up their boats, sell the timber, and afterwards return home slowly by land; and a voyage up the river from New Orleans to Pittsburgh, a distance of about two thousand miles, could hardly be accomplished, with the most laborious efforts, within a period of four months. This voyage is now made by steam-boats, with ease, in 15 or 20 days; and at the rate of not less than five miles an hour. Why would steam be advantageous for propelling ploughs and other agricultural implements? Because, independently of the saving of horses and their food, the farmer would never be obliged to work his soil, but when it was in a proper condition for that purpose. Mr. Loudon thinks that to apply steam successfully to agriculture, the engineer ought not to seek for a new implement, but simply for a convenient locomotive power for propelling the implements already in use, modified so as to suit the new impelling power. Why are the locomotive engines so advantageous for the conveyance of passengers? Because they admit a rate of speed that would be en tirely inconsistent with safety, even although it were practicable to attain it with animal power. It would be still imprudent, however, to adopt the utmost rate of thirty miles, because such an unusual rate of velocity, surpassing that of the swiftest horse, would be alarming, if it were not dangerous. At the rate of twenty miles an hour, however, it might be perfectly practicable to travel with the utmost safety and comfort. The economy of the plan may be illustrated as follows:-Between Liverpool and Manchester, we may safely estimate the number of passengers every day at 400 each way, and the average fare to be about seven shillings each; the daily expenditure will amount, in this manner, to about 2801. By the use of steamcoaches, the fares will be reduced to two-shillings and sixpence, and would thus amount only to 100. per day, making a daily saving of 180l., or upwards of 60,000l. per annum. The expense of the Liverpool and Manchester Railway, is now estimated at upwards of 20,000l. for each mile; the whole cost amounting to 820,000l. The rails used on the Liverpool and Manchester road are made of forged iron, in lengths of five yards each, and weigh thirty-five pounds per yard. Every three feet the rails rest on blocks of stone, let into the ground, containing each nearly four cubic feet. Into each block, two holes, six inches deep, and one inch in diameter, are drilled; into these are driven oak plugs, and the cast-iron chains or pedestals, into which the rails are immediately fitted, are firmly spiked down to the plugs, forming a structure of great solidity and strength. The double lines of rails for the carriages, are laid down with mathematical correctness, and consist of four equi-distant rails, four feet eight inches apart, about two inches in breadth, and rising about an inch above the surface. In the formation of the railway, there have been dug out of the different excavations, upwards of three millions of cubic yards of stone, clay, and soil. THE STEAM-ENGINE. Why is heat so important in the production of mechanical agents? Because bodies, whether liquid, solid, or æriform, exert a certain degree of mechanical force, in the process of enlarging their dimensions, on receiving an accession of heat; and any obstacle which opposes this enlargement, sustains an equivalent pressure. This force is frequently used as a mechanical agent, and has this to recommend it, that it may be produced to almost any degree of intensity, without the expenditure any other mechanical force in its production. of It is not requisite to enter theoretically into the production of heat, since the subject has already been popularly illustrated in the present work.* Why is the steam-engine much more intelligible than its name first suggests? Because it is in fact only a pump, in which the fluid is made to impel the piston, instead of being impelled by it, that is to say, in which the fluid acts as the power, instead of being the resistance. It may be described simply as a strong barrel or cylinder, with a closely filled piston in it, which is driven up and down by steam, admitted alternately above and below from a suitable boiler; while the end of the piston-rod, at which the whole force may be considered as concentrated, is connected in any convenient way with the work that is to be performed. The power of the engine is of course proportioned to the size or area of the piston, on which the steam acts with a force, according to the density, of from 15 to 100 or more pounds to each square inch. In some of the Cornish mines, there are cylinders and pistons of more than 90 inches in diameter, on which the pressure of the steam equals the efforts of 600 horses.-Arnott. The steam-engines in England represent the power of 320,000 horses, equal to 1,920,000 men, and being, in fact, managed by only 36,000 men, add consequently to the power of our population, 1,884,000 men. The cost of a steam-engine varies according to its power. The smaller cost nearly 100l., for each horse power, the largest not quite 400l. The consumption of coal is rated at one bushel, or 84 pounds per hour, for an engine of ten-horse power; the quantity is somewhat less in proportion in engines of great power. Why is there a large vibrating beam in the steam-engine? Because, one end being connected with the piston * See Part V., CHEMISTRY.-Heat, p. 21 to 35. rod, is pulled down, while the power of the engine is applied at the other end to any mechanical purpose. Thus, when connected with immense water-pumps, it causes almost a river of water to gush out from the bowels of the earth. Why are the improved paddle-wheels of steam-boats made to enter the water sideways? Because they give the propelling stroke direct, whereas the ordinary wheels press the broad face of their paddles on the surface of the water, and thus increase the resistance. Why are steam-engines of such important use in mining? Because they speedily raise the water which breaks in on the miners. The practical adaptation of the steam-engine to mechanical purposes, is considered by Mr. Davies Gilbert as due to Mr. Newcomen, whose inquiries were introduced into Cornwall very early in the last century, and soon superseded the rude machinery which had, till then, been employed for raising water from mines, by the labour of men and horses. The various applications of steam-power would occupy many pages: if we except its adaptation to the motion of carriages, perhaps few of its effects are more astounding than in the manufacture of iron. Thus, there are factories where this resistless power is seen, with its mechanic claws, seizing masses of iron, and in a few minutes delivering them out again pressed into thin sheets, or cut into bars and ribands, as if the iron had become soft, like clay in the hands of the potter. The annual product of the foundries of Messrs. Crawshay and Co. in Glamorganshire, is 11,000 tons weight of pig-iron, and 12,000 tons of iron in bars. A steam-engine of the power of 50 horses, and a waterwheel of 50 feet diameter, work the cylindrical blow |