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563 



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gardener usually suspects; for if the 

 sulphurous acid amounts to no more 

 than one cubic foot in ten thousand of 

 the air in a hot-house, it will destroy 

 most of its inhabitants in two days'. 

 To avoid such destruction, for the com- 

 fort of visitors, and above all for the 

 sake of the plants' vigour, air should be 

 admitted as freely as the temperature 

 will permit. The foul warm air can 

 In the above noticed house, the be easily allowed to escape throusih 

 length of pipe five inches in diameter, ventilators in the most elevated parts 

 is 150 feet; and these multiplied by of the roof, and fresh warm atr can be 

 1.363 =:20. 5 cubic feet of steam, and as readily supplied through pipes made 

 as the pipe will condense the steam of to enter near the flooring of the house 

 about one cubic foot and one-third of after passing through hot water, or 

 water per hour, therefore the boiler other source of heat, 

 should be capable of evaporating H I am quite aware that Mr. Knight 

 cubic feet of water per hour, to allow has stated that he paid little attention 

 for unavoidable loss. In the extreme to ventilation, and that plants will be 

 case of the thermometer being at zero, vigorous for a time in VVardian cases; 

 the consumption of coals to keep up but this does not prove that their Creator 

 this evaporation will be 12| pounds per made a mistake when he placed vege- 

 hour. , tables in the open air. 



These calculations are all founded Plants confined in houses or other 

 upon the supposition that the condensed close structures may be made to grow 

 water is returned to the boiler whilst in spite of such continement ; but all 

 hot; but if this cannot be eff'ected, e.\perience proves that other favourable 

 then one-twelfth more fuel will be re- circumstances, such as heat, light, and 

 quired. The boiler for the supply moisture being equal, those plants are 

 either of steam or hot-water, should be most vigorous and healthy which have 



covered with the best available non-con- 

 ductor of heat, and this is either char- 

 coal or sand. 



A case of brickwork, with pulverized 

 charcoal, between this and the boiler, 

 is to be preferred to any other. A 



the most liberal supply of air. 



There have been many modes sug- 

 gested for self-acting ventilators, de- 

 scriptions of which may be found in 

 Loudon's Encyclopadia of Gardening, 

 and the Transactions of the London 



boiler having a surface of seventy feet Horticultural Society; but there are 

 exposed to the air, in a temperature of none that can supersede the gardener's 

 32^, requires an extra bushel of coals personal care, tlirected by the ther- 

 to be consumed per day, to compensate uiometer and experience, 

 for the heat radiated and conducted The practice of all ventilation is 

 from that surface ; and the smaller the founded on the principle that the hot- 

 boiler, the greater is the proportionate test air rises to the highest part of the 

 waste. The surface of the pipes should house, and if there allowed to escape, 

 be painted black, because a surface of colder air will come in below, if al- 

 this colour gives out more heat in a lowed, to supply its place. To pre- 

 given time than any other. — Prin. of vent the hot air escaping too rapidly, 

 Gardening. the ventilators should be fitted wiih 

 Ventilation. — The accumulation of doors or caps, capable of regulating the 

 gaseous matters, such as sulphurous size of the orifice ; and the openings 

 acid and ammonia, and the consumption admitting fresh and colder from with- 

 of carbonic acid, render ventilation out, should have similar regulators, 

 essential to the health of plants in fore- and be made by means of pipes passing 

 inp-pits and hot-houses. They cannot through the bark-bed, tank of hot water, 

 inhale air overloaded with these con- or other source of heat, so that the 

 laminations, without being speedily in- reduction of temperature be not too 

 jured, and the proportions of those rapid. 



gases which rapidly cause disease, or ' Some guide in constructing venti- 



even death, are much less than the lators proportioned to the size of the 



