r, in stating the following plan by Mr Abernethy, who candidly acknowledges that it is built upon the principles which we, together with the learned editor of Chambers's Cyclopædia, have borrowed from Dr Hailes. This plan consists merely in caulking two tubes to descend from above the deck to the bottom of a vessel, or as low as ventilation is required; and which should communicate by smaller pipes (open at their extremities) with those places designed to be ventilated. There should be a contrivance for stopping these communicating pipes, so that ventilation may be occasionally prevented from taking place, or confined to any particular part of the vessel.

One of the principal air tubes should descend as near to the stern of the vessel as convenient, and the other as near to the stem.

Through that tube which is in the head, the foul air is to be extracted; and through that which is in the stern, the fresh air is to descend to the different decks and other apartments of the vessel.

The extraction of the air is easily effected in the following manner: Let a transverse tube be fitted to that which descends in the head of the vessel; it may be sunk within the level of the deck, so as to cause no inequality of surface. Let it be continued till it comes beneath neath the fire-place, then ascend in a perpendicular direction through the fire, and open a little above it; or it may be made to communicate with the chimney. It would be more convenient if the fire was near the place where the tube rises through the deck; but the experiment must equally succeed, if the tube be made to descend again till it is beneath the common fire-place.

The effect that will result from this contrivance is obvious; when the tube which passes through the fire is heated, the air will ascend with a force proportionate to its levity, and the ascending column can only be supplied from below, consequently it must come from all those parts of the ship with which the main tube communicates.

When the ports are open, the quantity of air thus exhausted from the ship will be supplied from all quarters; but if they were all shut, and the hatchways and other openings completely closed, the renewal of fresh air is made certain by means of the tube which descends in the stern. The main air tube, where it rises above the deck in the stern, should have an horizontal one fitted to it, which might be made to traverse, so that it could be turned to windward; it might also expand at its extremity like the mouth of a trumpet; and thus perfectly fresh air must enter, and the force of the gale would tend to impel it into the vessel.

When that part of the tube which passes through the fire is red hot, the draught which would be thus occasioned might perhaps be too great, and the open pipes which communicate with the decks might emit and imbibe the fresh air in so direct a stream, that it might be injurious to those persons within the current.

Mr Abermuthy therefore thinks it would be better if those smaller pipes which lead from the main tubes were made to run along the decks, and communicate with them by numerous orifices. Two pipes opening into the main exhausting tube might be extended along the tops of the deck, in the angle formed between the sides and the ceiling; and thus the air would be extracted equally from all parts, and in a manner not likely to occasion injurious currents. Some division of the stream of air which enters from the stern might also be made, if it were thought necessary.

Thus a very complete, and in no way injurious, ventilation may be obtained: the air in the vessel would be perfectly changed when the fire was strong, without expense or trouble; and a gradual and salubrious alteration of it might at all times be made, by a very little additional quantity of fuel. The air tubes should consist of separate joints, so that occasionally they might be taken to pieces; and to prevent their being injured or put out of order by rough usage, the copper pipes should be made of considerable strength, placed against the sides of the vessel, and even incased in wood.

In the Letters and Papers of the Bath Society, &c., we have the following description of a ventilator for preserving corn on ship board, by Thomas South, Esq.

Fig. 1. is a cylindrical air-vessel, or forcing pump, of lead, tin, or other cheap metal; its internal diameter being ten inches, and its length three feet; having a crutch-handled piston to work with, and an iron nozzle, viz. a hollow inverted cone, two feet long, to condense the air, and increase its power in its passage downwards. This cylinder should be riveted or screwed, by means of an iron collar or straps, to the deck it passes through, both above and below, as at a a; and should be farther secured by some holdfast near b, to keep it steady in working.

Fig. 2. is a bottom of wood, four inches and a half thick, with a projecting rim at its base, for the metal cylinder to rest on when cemented and screwed to the wood. The centre of this bottom is excavated, for the reception of the crown of the nozzle. In the same figure the nozzle is represented with its crown like a bowl dish, to condense the air gradually, without resistance, in its advance to the more contracted base of the inverted cone, i.e. the top or entrance of the nozzle. About two-thirds down this nozzle may be fixed a male screw, as c c, for the purpose hereafter mentioned.

N.B. The forcing-pump should be casted in wood, to protect it from outward bruises, which would prevent the working of the piston, and ruin its effects. The leather round the embolus should be greased when used.

Fig. 3. is a crutch-handle, fastened to the embolus A by its iron legs B, B. A is a cylinder of wood, cased with leather, so as to fit well, but glide smoothly, in the metal cylinder; having an opening as large as its strength will permit, for the free access of atmospheric air. C is a valve well leathered on its top, and yielding downwards to the pressure of the air when the piston is raised up. D is a cross bar of iron, to confine the valve, so that it may close instantly on the return of the piston downwards.

Fig. 4. is a tin pipe or tube, of less than four inches diameter, and of such length as, when fixed to the base of the cylinder, fig. 1, shall admit the nozzle d, fig. 2, to within half an inch of the valve E, at the bottom of the wooden cylinder F, in fig. 4; which valve E will then yield to the pressure of air contained in its passage through the nozzle, and deliver it into the pipes below. This valve must be well leathered on its upper surface, and fastened with an hinge of leather to the cylinder it is meant to close: affixed to its bottom is the spindle G, passing through a spiral spring H, which, being compressed on the descent of the valve, will, by its elasticity, cause it to rise again, close the aperture above, and retain the air delivered beneath it. On connecting this cylinder with the upper end of the nozzle, at c c, fig. 2, we must carefully prevent any lapse of air that way, by a bandage of oakum incased with wax, on which to screw the cylinder, like the joints of a flute, air-tight. I is a bar of iron, having a rising in its centre, wide enough for the spindle to play through, but at the same time sufficiently contracted to prevent the passage of the spiral spring.

Fig. 5. is an assemblage of tin pipes, of any lengths, shaped suitably and conveniently to their situation in the ship, to the form of which, when shut into one another, they must be adapted; observing only, that the neck be straight for a length sufficient to admit the lower end of the cylinder, fig. 4, as high as the letter F, or higher.

Fig. 6. To the middle pipe, which runs along the bottom, should be fixed a perpendicular one, fully perforated, to convey the air more readily into the centre of the heap; and this may have a conical top, as represented in the Plate, perforated with a smaller punch to prevent the air from escaping too hastily. In large cargoes, two or three of these perpendiculars may be necessary; and each should be well secured by an iron bar, screwed down to prevent their being injured by the shifting of the cargo in stormy weather or a rolling sea. The top of the conical cap of these pipes may reach two-thirds up the cargo.

Fig. 7, is a valve of the same construction as that represented in fig. 4, but inclosed in a tube of brass, having a female screw at f, adapted to the male screw e, on the nozzle fig. 2, and may then be inserted into the head of the pipe fig. 5. This will add to the expense; but in a large apparatus it is to be preferred, as a more certain security from lapse of air, than the junction of the tube fig. 4, to the neck ee in fig. 2.

N.B. ee is a neck of wood, making a part of the bottom fig. 2, wherein to secure the tube fig. 4, when applied to the nozzle. The joints of the pipes, when put together for use, should be made air-tight, by means of bees wax or some stronger cement, till they reach the bottom of the vessel, when there is no farther need of this precaution. The horizontal pipes should run by the side of the keelson the whole length of the hold. The tin plates of which K is made, should be punched in holes, like the rote of a watering pot, in two or three lines only at m, and then formed into a tube, with the rough edge outwards. L may have four or five lines of the like perforations. M, and the rest, should gradually increase in their number as they advance towards the middle of the hold, and continue fully perforated to the last pipe which should be closed at its end to prevent the ingress of the corn. It is the centre of the cargo which most requires ventilating, yet air should pervade the whole. Like the trade-winds, it will direct its course to the part most heated, and, having effected its salutary purpose there, will diffuse itself to refresh the mass.

Where the hatches are close-caulked, to prevent the influx of water, vent-holes may be bored in convenient parts of the deck, to be hunged up, and opened occasionally, from whence the state of the corn may be known by the effluvia which ascend when the ventilator is working.

The power of the ventilator is determined by the square of its diameter multiplied into the length of the stroke, and that again by the number of strokes in any given time.

The air-ventil or forcing pump, with the rest of the apparatus here described, is adapted to a vessel of 120 tons burden; but by lengthening the air-ventil, extending its diameter to 14 inches, and adding 10 inches more to the length of the stroke, a power may be obtained of ventilating a cargo of 400 tons within the hour. If this machine be properly wrought for one hour every day, or even every two days, beginning the operations immediately when the corn is put on board, the cargo may be preserved from taint or injury of every kind during the longest voyage.a duchy of Germany, in the circle of Lower Saxony. It is bounded on the east and south by that of Lunenburg; on the west, by the Weser and the duchy of Bremen; and on the north, by the duchies of Bremen and Lunenburg; extending both in length and breadth about 28 miles. It consists chiefly of heaths and high dry lands; but there are good marshes on the rivers Weser and Aller. In 1712, the Danes wrestled this duchy from Sweden, and, in 1715, ceded it to the king of Great Britain, as elector of Hanover; Verdigris, which cession, in 1718, was confirmed by the Swedes. The inhabitants are Lutherans.