Sailing and Steam- Vessels. 263 



natural caverns, and which has been successfully applied to 

 the ventilation of mines, will apply with equal force here. We 

 know that the air in a well remains stagnant and pent up ; 

 but, as has been remarked,* if two wells or shafts are sunk 

 at a given distance from each other, and a horizontal passage 

 cut fiom the bottom of one well to the other, so soon as the 

 communication is made, there will be a tendency in the air to 

 descend one shaft and ascend the other, whenever the tempe- 

 rature of the external air varied from that below. Applying 

 the principle to the general ventilation of ships, there is no- 

 thing to prevent the converting of the open spaces between the 

 timbers or ribs, into fresh or foul air flues or conduits. One 

 series of these being arranged to convey down pure air — 

 not to be taken from below, but from above the upper deck — to 

 points of discharge at the floors of the gun and orlop decks, 

 cabin-floors, or wherever requisite, and another series of open- 

 ings, entirely/ separated from the firsts to commence at the 

 beams or ceilings of these respective places, and pass upward 

 above decks as high as convenient, for the escape of the foul or 

 vitiated air. The points of ingress or egress for the air be- 

 tween decks may be in the form of a horizontal slit covered 

 with perforated sheet copper or zinc, to break the force of the 

 current. The points of inlet and outlet for the air above 

 deck might have their effect increased, by having the orifices 

 so arranged, that, while protected from the weather, the for- 

 mer would open to, the latter from, the wind. A portion of 

 the interstices of the timbers similarly arranged, communicat- 

 ing directly with the open air, could be made to circulate fresh 

 air for the timbers of the ship ; but the apertures for the 

 ventilation requisite for crews and passengers, must have no 

 communication with the former, so as to prevent the corrupt 

 gases from the bilge entering the latter. Inconveniences may 

 be experienced practically, in having the air openings as de- 

 scribed, from the difficulty of constructing those on the upper 

 deck so as to keep out the water; but were the principle adopted 

 and carried into practice, the skill and ingenuity of ship-builders 

 would soon overcome any such slight obstacles. Ventilation 



• Letter of John Buddie, Northumberland, 1816. 



