Page:The fairy tales of science.djvu/372

 These engines, the largest ever constructed with oscillating cylinders, are nevertheless inferior to those devoted to the screw-propeller.

This screw is twenty-four feet in diameter, and weighs thirty-six tons. Its four fans, which were cast separately, and afterwards fitted into a large cast-iron boss, have been aptly compared to the blade-bones of some huge animal of the pre-Adamite world. Besides being pulled along by the paddles, and pushed along by the screw, the Leviathan will also be propelled by the wind when exceptional circumstances render such aid desirable. There are six masts, five of iron and one of wood, and on these masts will, or may be, spread about 6500 square yards of canvass. Under ordinary circumstances the Leviathan will go faster than the wind, and sails will prove an impediment rather than an assistance to the ship's progress. It is not probable, therefore, that they will be much resorted to except for the purpose of steadying or of helping to steer the huge vessel. The steam-power will be truly enormous; it has been stated that, were everything put to work at its fullest, the whole series of engines would work up to 11,500 horse-power. This power would suffice to raise 200,000 gallons of water to the top of the Monument in less than a minute, or to work all the cotton mills of Manchester.

When all the engines are in full work, the great source of power, coal, will be needed to the extent of 250 tons each day. For a voyage to Australia