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this calculation, the amount of friction, &c.

may be accurately ascertained.

Undershot water wheel.....

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Hydraulic Ram. (This machine

will make from 20 to 100 strokes per minute.)

Large machine at Chremnitz, (each stroke occupying about three minutes.)

Power

Effect

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But the water-mill, which is the usual machine employed, even in its most improved form, is far from being beneficial either to the agriculturist or the manufacturer. The former is injured by the laws which prohibit the draining of mill-streams for the purposes of irrigation, by which much improvement is kept back that would otherwise take place; while the health of the latter, in the immediate neighbourhood of manufacturing districts, is much injured by the stagnant condition of the water which is thus unnecessarily dammed up.

Wind, which we may consider as the next substitute for animal power, appears to have been first employed to give motion to machinery in the beginning of the sixth century.

The use of this species of mechanic force, is however principally limited to the grinding of corn, the pressing of seed, and other simple manipulations; the great irregularity of this element precluding its application to those processes which require a continued motion.

A windmill with four sails, measuring seventy feet from the extremity of one sail, to that of the opposite one, each being six feet and an half in width, is capable of raising 926 pounds, two hundred and thirty-two feet in a minute; and of working on an average eight hours per day. This is equivalent to the work of thirty-four meu; twenty-five square feet of canvas performing the average work of a day labourer. A mill of this magnitude seldom requires the attention of more than two men ; and it will thus be seen, that making allowance for its irregularity, wind possesses a decided superiority over every species of animal labour.

To shew, however, the great advantage the Steam Engine, even in its rudest state, possesses over mere pneumatic or hydraulic machinery, we will now examine its effective force when employed in the working of pumps.

It has been already stated, that

the Machine of Marly, formerly considered the most powerful engine in the world, when first erected lost seven-eighths of its power from friction, and other causes; while the overshot water-wheel which can act only in favourable situations, produces nearly eight-tenths of the force employed. Now it is stated by Dr. Desaguliers, that the atmospheric engine working at Griff-mine, nearly a century back, produced full twothirds of effective force for the power employed; and this too at a comparatively moderate expense. We find, farther, that an hundred weight of coals burned in an engine on the old construction, would raise at least twenty thousand cubic feet of water twentyfour feet high; an engine with a twenty-fourinch cylinder doing the work of seventy-four horses. From this it will be seen that a bushel of coals is equal to two horses, and that every inch of the cylinder performs nearly the work of a man.

An engine upon Captain Savery's plan, constructed by Mr. Keir, has been found to raise nearly three millions of pounds of water one foot high with a single bushel of coals; while the best engine on Newcomen's principle will raise ten millions, and Mr. Watt's

engine upwards of thirty millions of pounds, the same height. If we add to the advantage gained by the employment of so cheap a prime mover, the vast concentration of force thus brought into immediate action, its value may easily be appreciated.

One of the largest engines yet constructed, is now in action at the United Mine in Cornwall, it raises eighty thousand pounds. one hundred feet in height per minute: and to effect this enormous labour, it only requires about thirty pounds of coal for the same pe riod of time.

To the mining interests this valuable present of Science to the Arts has been peculiarly acceptable; as a large portion of our now most productive mineral districts must have long ere this been abandoned, had not the Steam Engine been employed as an active auxiliary in those stupendous works. In draining of fens and marsh lands this machine is in the highest degree valuable; and in England, particularly, it might be rendered still more generally useful. In practice it has been ascertained that an engine of six-horse power, will drain more than eight thousand acres, raising the water six feet in height;

while the cost of erection for an engine for this species of work, including the pumps, will not exceed seven hundred pounds. This is more than ten windmills can perform, at an annual expenditure of several hundred pounds; while, in the former case, the outgoings will not exceed one hundred and fifty pounds per annum.

To the mariner, also, the Steam Engine offers advantages of a no less important and novel nature than those we have already described. By its use he is enabled to traverse the waters, both against wind and tide, with nearly as much certainty, and, as the machinery is now constructed, with much less danger, than by the most eligible road conveyance.

In proof of the speed of these vessels, it may be sufficient to state that the passage from or to London and Margate, which is more than eighty miles, by water, is often performed in the short space of six or seven hours! It too frequently, however, happens that the faults of any new invention are unjustly magnified, while its real advantages are seldom duly appreciated; and this axiom has been fully verified, in the clamour so unjustly raised against the application of the Steam

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