VENTILATION. 



285 



simple mechanical contrivance, all these 

 boxes may be opened or shut at once, or 

 less or more, as is desired. 



Upon the same principle as the last, 

 but on a much larger scale, we have 

 applied a mode of front ventilation to a 

 range of vineries 100 feet in length, with 

 a view to obviate opening the front 

 sashes, as well as treading on the border 

 during the operation. These vineries 

 are on the lean-to principle ; but, as will 

 readily be imagined, the same mode of 

 ventilating may be applied to span- 

 roofed houses also. The stone plinth 

 upon which the front rests is supported 

 upon 10-inch brick piers, one being 

 placed under each rafter — that is, about 

 3 feet 8 inches centre from centre. 

 Along the front of these piers an area, 

 opening 9 inches broad in the clear, is 

 carried along the whole length, but 

 divided into spaces of 18 inches in length, 

 one-half of which are as deep as the 

 bottom of the return hot-water pipe 

 within, which is 23 inches, and the other 

 half are only 9 inches — that is, level with 

 the top pipe, also within. On top of this 

 area is fixed down an open framework of 

 cast-iron, having in it openings 2 feet 

 long by 9 inches in width. The margin 

 of this frame is 3 inches broad, with 

 cross bars between the openings an inch 

 and a half broad, placed at every 10 feet, 

 the whole frame being 1 inch in thick- 

 ness. Over this metallic frame are placed 

 movable covers or plates, also of cast- 

 iron, and flanged at the edges. These are 

 connected together along the top by means 

 of a malleable-iron rod, three-eighths of 

 an inch in diameter, extending the whole 

 length, and connected at the end of the 

 range, close to the wall, with a wheel. 

 This wheel is fixed on a shaft placed 

 across the frame. In the middle of this 

 shaft is also placed a pinion 4 inches in 

 diameter, which hooks into a rack cast 

 on the back of the first cover. This 

 wheel is acted upon by a lever, which, 

 when depressed, has the power of draw- 

 ing every alternate cover on the top of 

 the one next to it, to any extent not 

 exceeding its own length. By elevating 

 the same lever, the lids or covers are 

 pushed back to their original place. 

 This is for winter and spring ventilation. 

 For summer ventilation, the covers which 

 we have stated as fixed are attached to 



the metallic rod, by running it through 

 eyes cast on all the covers, by which 

 means these fixed ones are capable of 

 being moved as well as the others. It 

 should be remarked that all the alternate 

 covers are their own thickness above the 

 others. It will readily be understood, 

 that, for winter ventilation, none of the 

 covers are required to be withdrawn to 

 their whole extent — 3 or 4 inches being 

 the average of the opening. We state 

 this, because it may seem to some that, 

 from the construction of the apparatus, 

 as much air would be admitted by one 

 set when opened to their full extent — 

 namely, 18 inches — as by both sets when 

 opened to their half extent — namely, 

 9 inches each. This would not be the 

 case, however ; for more air will be ad- 

 mitted by two openings of 9 inches square 

 during summer, than would be through 

 one of double the size, as the velocity of 

 its passage inwards will be increased, 

 although the individual openings be 

 smaller, because they are increased in 

 number, and also on account of the 

 greater difference in temperature between 

 the internal and external air. Indeed, 

 the openings can never almost, during 

 winter, be used to their full extent. 

 Besides, by increasing the number of 

 openings, the distribution of the air is 

 more completely accomplished. Another 

 reason for using only the alternate open- 

 ings during winter is, that as more fire- 

 heat is then employed, there is the 

 greater necessity for throwing in fresh 

 supplies of air to the interior atmosphere ; 

 and as these alternate openings, by which 

 air is thrown in, are also the deepest, 

 they take with them a certain amount of 

 humidity from the water under the lower 

 pipe, and carry it into the upper parts 

 of the house. By this mode of ventilat- 

 ing, all treading on the border is obviated ; 

 and even should it be necessary to pass 

 along the front of the houses, the cast- 

 iron plate forms a clean footpath. The 

 same mode might be applied at the front 

 of the border next to the walk, and the 

 air carried through the border in drains, 

 and admitted into the house. It may 

 be found advantageous to bring down 

 cold air from the roof, on a somewhat 

 similar principle, in tubes, so that it may 

 fall perpendicularly on the hot-water 

 pipes or flues, or even be made to fall 



