TEANSPOET BY SEA AND LAND 901 



but can never be satisfactory until vessels are specially 

 built for animal transport. If this last condition were 

 carried out the entire planning of hatchways and structural 

 arrangements would be subservient to admitting air below ; 

 whereas in the general construction of a ship, the air open- 

 ings are reduced to the smallest possible number as inter- 

 fering with deck space, and, further, where air can find its 

 way water can. 



Ventilation is also complicated by the number of decks 

 employed for carrying animals, it is easier to ventilate two 

 decks than three. No system of ship ventilation is satis- 

 factory which depends entirely upon driving a certain 

 amount of air into a space ; there must always be means 

 for extracting air. The ordinary bell mouthed ventilator is 

 intended to serve both these purposes ; turned towards the 

 wind it is an inlet, turned away from the wind it is an 

 outlet. In practice as well as theory they have this effect, 

 but the number provided though sufficient for ventilating 

 the ordinary cargo deck of a ship, is insufficient when that 

 deck is converted into an animal transport. More venti- 

 lators mean increased deck space ; if they are aligned on 

 each other they cannot all work as inlets when the wind is 

 dead ahead as one covers the other, so that they require 

 to be placed at various parts of the deck in order to be able 

 to catch the wind, and this means interference with naviga- 

 tion. There are difficulties attached to introducing more 

 ventilators, so that it is usual to supplement the usual 

 trumpet mouthed structure by windsails which pass through 

 hatchways to the various decks. 



Windsails are excellent arrangements ; they should have 

 a big square head, and an internal diameter of two feet ; 

 below they should rest on the deck, and be carried forward 

 some little distance from the hatchway to prevent the fresh 

 air escaping by this channel before mixing with the air of 

 the deck. As a matter of fact this is what generally 

 occurs. 



Windsails must not cover each other ; as they approach 

 the bridge and the stern they require to be progressively 



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