INTRODUCTION. 



Some material alterations were made in the interior arrangements, 

 which experience suggested as necessary to the accommodation, health, 

 and comfort of the officers and men. One of the principal of these 

 consisted in applying a thick close lining of cork all round the ships' 

 sides, and on the under part of the upper decks, fore and aft. Shut- 

 ters and plugs of the same material were also fitted to every window, 

 sky-light, and illuminator, so as completely to surround the inhabited 

 parts of the ships, during the winter months, with this substance. 

 Care being thus taken to prevent the rapid escape of the warmth, 

 recourse was also had to the most effectual means of producing and 

 distributing it. With this view, an apparatus was fixed on the orlop 

 deck of each ship, between the sail-room and the main hatchway, on a 

 plan proposed and executed by Mr. Sylvester, for conveying a current 

 of heated air into the several inhabited apartments. It is described 

 by Mr. Sylvester to " consist of a wrought-iron vessel, about twenty- 

 two inches square, placed upon pillars resting on a cast-iron frame 

 upon the beams of the orlop deck. This vessel, or cockle, was four 

 feet high, close at the top, having an opening in front for the ash- 

 pit and feeding-door, and another behind for the discharge of the 

 smoke into a perpendicular iron tube. The fire-place is within this 

 vessel, and the heat is given to its interior surface. On the outside 

 is an iron covering containing tubes, which approach, nearly at right 

 angles, to the surface of the cockle ; these are divided into two por- 

 tions, one below to receive the cold air, which impinges upon the 

 cockle; the other above, for the discharge of the warm air. These 

 two cavities are separated from each other by a second casing about 

 four feet square below, for the cold air, and terminating in two feet 

 square at the upper-deck, where a part of the warm air is dis- 



