His next concern was to see to the purity of the ship itself, without which attention all the rest would have profited little. I shall not however detain you with the orders about washing and scraping the decks, as I do not understand that in this kind of cleansing he excelled others; but since our author has laid so great a stress upon _Fire_, as a purifier, I shall endeavour to explain the way of using it, more fully than he has done in his Paper. Some wood, and that not sparingly, being put into a proper stove or grate, is lighted, and carried successively to every part below deck. Wherever fire is, the air nearest to it being heated becomes specifically lighter, and by being lighter rises, and passes through the hatchways into the atmosphere. The vacant space is filled with the cold air around, and that being heated in its turn, in like manner ascends, and is replaced by other air as before. Thus, by continuing the fire for some time, in any of the lower apartments, the foul air is in a good measure driven out, and the fresh admitted. This is not all: I apprehend that the acid steams of the wood, in burning, act here as an antiseptic and correct the corrupted air that remains. An officer of distinguished rank, another of Captain Cook's experienced friends, mentioned to me a common and just observation in the fleet, which was, that all the old twenty-gun ships were remarkably less sickly than those of the same size of a modern construction. This, he said, was a circumstance he could not otherwise account for, than, by the former having their _galley_* in the fore-part of the _orlop_**, the chimney vented so ill, that it was sure to fill every part with smoke whenever the wind was a-stern. This was a nuisance for the time, but, as he thought, abundantly compensated by the extraordinary good health of the several crews. Possibly those fire-places were also beneficial, by drying and ventilating the lower decks, more when they were below, than they can do now that they are placed under the fore-castle upon the upper deck. [* Their fire-place or kitchen.] [** The deck immediately above the hold.]