262 Suggestions for the better Ventilation of 



air about the timbers, and another the exclusion of air.* In a 

 communication to the Royal Society of London in 1820, by 

 Sir Robert Seppings, F.R.S., when giving suggestions for a 

 "new principle of construction of ships for the mercantile navy, 

 'he alludes to the ventilators of Dr Hales, and the utility of ge- 

 neral ventilation, but attaches importance to the exclusion of 

 atmospheric air for the preservation of the frame- work, though 

 he was not inattentive to the value of admitting air to the in- 

 terior of ships. Another view is taken of this subject in the 

 able treatise on ship-building in the Encyclopaedia Britan- 

 nica, where the suggestion is made that the preservation of 

 the timbers might be assisted by adopting the openings be- 

 tween the timbers themselves for the purpose of circulating 

 air about them ; and it is stated that, in the year 1827, the 

 author had proposed this plan to the Admiralty. This opinion 

 strengthens the view I entertain of the practicability of com- 

 bining in a very simple way the general ventilation of the ship, 

 with due attention to the ventilation of the frame-work. 



The defect at present in airing the frame, where the inter- 

 stices of timbers are made use of, arises from the difficulty of 

 obtaining a current or circulation, from the inlet for the air 

 being placed between decks, and no outlet being provided. 

 But were it so contrived as to allow at all times a free current 

 of external air by points of ingress and egress, the effect would 

 be very different. It seems often overlooked, but there is no 

 point more important to be attended to in spontaneous ventila- 

 tion than that where openings are provided for the escape of im- 

 pure air, others must also be provided for the supply of fresh 

 air, and vice versa. It must not be forgotten that air, like 

 other fluids, can only fill a given space, or, as one of the earliest 

 writers remarks, " that unless openings are properly adapted 

 to suffer air to pass freely through, the external air proves a 

 stopper to the internal, and only mixes with the next in con- 

 tact." The same law which regulates the effect of currents in 



* Captain Symmonds, Surveyor-General of Dock Yards, has, in a man of war 

 now ready for launching at Woolwich^ carried the timbers solid about as high as 

 the lower gun ports. Mr Lang, who is naval architect for the Prince Albert, 

 120 guns, now building, I am informed, does not intend carrying up the solid 

 frame nearly so high. 



