part may, by introducing the outer air, be raised as near to an equilibrium with the temperature at the opposite side of the timber as necessary. And such warmer outer air is commonly to be introduced, as before mentioned, through such last mentioned apertures, the valves whereof are to be taken out for the purpose. But if it be only the lower part of the hold into which the introduction of warmer outer air is required, it will be most convenient to introduce such air through the shaft, and admitting trunks, as also before mentioned. And, in every case of introducing warmer air, it is to be caused to enter the vessel by removing the colder air already in the interior, up through the descending trunk, and out of the vessel, by one or other of the means, in that behalf, before described; and, for this purpose, use such of the apertures, in the descending trunk, for receiving the colder air, as are situated most nearly at the same level with, and not lower than, the part the temperature whereof is to be raised. And when that part of the vessel, the temperature whereof is to be raised, is situated immediately underneath a quarterdeck, poop, or forecastle, or in any other part at a distance from such descending trunk, with another part intervening of a temperature already sufficiently high, make use of a hose, as before described, for more speedily removing the colder air. The operation of removing the colder air, so long as the temperature at the outside remains unchanged, is to be continued till a quantity of the warmer air has been introduced, and passed off, sufficient to raise to the height desired the temperature, not only of the air, but of the other substances contained in the particular part of the vessel, the temperature whereof is to be raised.

When the temperature of any part of the interior, situate below the level of the water line, is lower than that of the water at the outside, at the same level, and the tem

perature of the air at the apertures of the discharging valves for heated air for such part, or at the entrance of the shaft, is at the same time lower than that of the water, but somewhat higher than that of such part of the interior, raise the temperature thereof, so far as it can be raised, by the introduction of the outer air, in the manner before mentioned. But no part of my said invention is directly adapted to still farther raising the temperature, in such case, to a level with that of the water. And I have purposely abstained from endeavouring to invent, and directing, any thing as applicable for that purpose, because the case supposed need not be otherwise than of very rare occurrence, and it may, in almost all circumstances, be guarded against, by taking care not to introduce any considerable quantity of air of a lower temperature than the water at any given depth, down to a depth on a level therewith, and by introducing air, at the hottest time of day, into such parts of the interior, when the vessel is approaching warmer latitudes, or the weather is getting hotter, so as to raise the temperature of the water; and because, under such circumstances, any machinery for the introduction of heat, artificially produced from a fire, into such parts of the interior, would, by its expense, and the room it would take up, compared with the rareness of the occasions on which it would be required to use it, and the benefit it could produce, and by the risk of doing harm therewith, for want of apportioning the quantity of heat with sufficient exactness to the quantity required, be, in my judgment, on the whole, productive of more disadvantage than good.

In such of the directions, which I have above given, as relate more particularly to the precise or exact situations, sizes, or dimensions, of any of the before mentioned alterations in the vessels, or of any of the apparatus and machinery before described, or to the situations and dis

tances at which to place the thermometers from each other, or which relate to the degree of approximation of the temperatures immediately at the opposite sides of the timber, and in all the directions, generally, which relate only to the extent of the application and putting in practice of my said invention, I am to be understood as giving directions with the view to the most perfect and complete application thereof, and to giving it the most extensive and thorough reach of operation, according to the best of my judgment, without meaning, or intending to be understood, that my said invention will be either wholly, or greatly, ineffectual, unless all such directions be literally, and in the fullest extent, complied with; and, on the contrary, the same may, and will, be commonly very effectual, provided a reasonable degree of care and attention be bestowed in following the directions given, notwithstanding the nicety and exactness pointed and aimed at, in the matters just referred to, be not to the fullest extent observed and put in practice.

Having now particularly described and ascertained the nature of my said invention, and in what manner the same is to be performed, I here, for guarding against being construed to claim as new therein, and as comprised within the power, sole privilege, and authority, granted by the said letters patent, any thing which is not new, and cannot lawfully be comprised within the said grant, repeat my declaration made at the commencement of this instrument of specification of my said invention, that the same consists in the making and manufacturing of the before described combination of the before described alterations in the vessels, and of the before described apparatus aud machinery for the purposes before described, and not in the separate manufacture of any of the separate parts thereof. And although I believe several of the separate parts thereof to be new, and to have never heretofore been