The iron chambers, for blowing open the ports, hold from 9 to 11 ounces of powder. They are fixed in such a manner as to prevent their recoil, and to ensure the ports being blown open. The vents are generally corked up, and covered with a piece of barras, till required to be primed. _To fit out a Fire Ship._—The whole breadth of the fire room is to be divided into 9 parts, and troughs laid the whole length of the room. Cross troughs, of communication are laid between them, about 20 in each row, perpendicular to the long troughs. These troughs are usually 4 inches wide, and 4 deep. There are two fire trunks and two fire scuttles on each side, under which the eight fire barrels are to be placed. The reeds and bavins are to be tied down in the troughs. The curtains are to be nailed up to the beams, equally through the fire room. The ship is not to be primed when fitted out, but only when intended to be fired. _To Prime._ _Composition for Priming._ Saltpetre pulverized 22 lbs. 8 oz. Rosin 2 11 Sulphur 18 — Mealed powder 45 — Linseed oil 1 pint. All the reeds and bavins are to be taken up, and a little of the above composition sprinkled in the bottom of the troughs; the reeds, &c. to be then gently tied down again. Quick match of 6 or 8 threads doubled must be laid along on the tops of all the reeds &c. and the priming composition strewed over it, and over all the fire room. The covers of all the fire barrels must be cut open, and made to hang down on the sides of the barrels. Leaders of strong quick match must be laid from the reeds to the barrels and to the chambers; and must be tied down to the vents to insure its not falling off. Strong leaders of quick match; 4 or 5 times doubled, must be laid from the reeds to the sally ports; and the sally ports must be connected by quick match, that the whole may take fire at once. The following method is now adopted of producing an external fire, in addition to the internal fire, before gained by the fire room. Fire boxes filled with the carcass composition, are distributed in the following manner, in a ship of three masts: 1 Suspended from each of the catheads and davits, on each side the bow 4 8 Slung across the bowsprit 8 4 Across each of the outriggers abaft 8 2 From the graplins of each of the lower yardarms 12 1 From the deadeyes on each side of the three round tops 6 1 From the middle of the inside of the main, fore, and mizen shrouds 6 —— 44