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gutter we would cover over with slate or galvanised 

 iron closely, and on it have placed a good portion of 

 charcoal in a rough porous state ; over this, or rather 

 up the centre, we would have a pipe run, with small 

 perforations thickly on each side, for turning on clear 

 water, or water charged with ammonia clarified, when 

 requisite, for damping the whole surface of charcoal, 

 tank or gutter, to charge the interior with humidity 

 at any time when required. Over this we would 

 erect a platform on two rows of piers, by carrying 

 across galvanised iron bearers, each end of course to 

 take a bearing also, on both back and front walls, 

 and a cavity left between the top of the tank or gut- 

 ter and the bottom of the platform. This cavity 

 should not be less than from 2 feet to 2 feet 6 inches 

 high ; 3 feet would be all the better ; first, because 

 the air would not be liable so soon to become stag- 

 nant ; secondly, because trap doors or ventilators 

 could be placed to admit persons to clean out the 

 chamber between the platform and surface of the tank, 

 examine the whole, and replenish the charcoal and 

 other requisites readily at any time ; and thirdly, it 

 would be an advantage to have ventilators to admit 

 with care the exterior air into the air chamber for 

 circulation over the whole structure. The bottom 

 or sides of the platform should be constructed with 

 J or 1-inch rods of galvanised iron. We say the sides, 

 because our plan would be to have a cavity left all 



