The condenser of Mr. _Hall_ consists of a great number of narrow tubes immersed in a cistern of cold water: the steam as it passes from the cylinder, after having worked the piston, enters these tubes, and is immediately condensed by their cold surfaces. It flows in the form of water from their remote extremities, and is drawn off by the air-pump, and conducted in the usual way to a cistern from which the boiler is fed. In the marine engines constructed under Mr. _Hall_'s patents, the tubes of the condenser being in an upright or vertical position, the steam flows from the cylinder into the upper part of the condenser, which is a low flat chamber, in the bottom of which is inserted the upper extremities of the tubes, through which the steam passes downwards, and as it passes is condensed. It flows thence into a similar chamber below, from whence it is drawn off by the air-pump. It is evident that at sea an unlimited supply of cold water may be obtained to keep the condensing cistern cold, so that a perfect condensation may always be effected by these tubes, if they be made sufficiently small. The water formed by the condensed steam will be pure distilled water; and if the boiler be originally filled with water which does not hold in solution any earthy or other matter which might be deposited or encrusted, it may be worked for any length of time without injury. The small quantity of waste from leakage is supplied in Mr. Hall's engine by a simple apparatus in which a sufficient quantity of sea water may be distilled. The following are the advantages, as stated by Mr. Hall, to be gained by his condenser:-- 1. A saving of fuel, amounting in some cases to so much as a third of the ordinary consumption. 2. The preservation of the boilers from the destruction produced in common engines by the corrosive action of sea or other impure water, and by encrustations of earthy matter. 3. The saving of the time spent in cleaning the boilers. 4. A considerable increase of power, owing to the cleanness of the boilers; the absence of injected water to be pumped out of a vacuum; the greater perfection of the vacuum; the better preservation of the piston and valves of the air-pump; and (by another contrivance of his) the more perfect lubrication of the parts of the engine. 5. The water in the boiler being constantly maintained at the same height by self-acting arrangement. 6. The size of a boiler exerting a given power, being much smaller than the common kind, owing to its more perfect action.