428 Transactions of the London Horticultural Society. 



glass, and by the continued escape, through open laps or crevices, of saturated 

 or moist air, whose place is supplied by cold and dry air. To imitate nature, 

 it is therefore necessary to provide a constant supply of moisture, equal to 

 the waste by these two causes. The means adopted to supply moisture to the 

 atmosphere is by sprinkling the floor and the plants, and by troughs upon 

 the heating pipes. Sprinkling the floor is a very imperfect and inefficient 

 expedient, the greater part of the moisture so bestowed sinks into the earth, 

 and very little indeed finds its way to the atmosphere of the house ; for the air 

 in contact with the floor of a house is generally nearly saturated, having lost 

 its capacity for moisture by losing its heat, and it is only when it has reached 

 the pipes, and been again heated, that it becomes capable of taking up 

 moisture, and in this thirsty state it generally has to seek its moisture among 

 the plants. 



" The most effectual mode of producing a moist atmosphere is by consider- 

 able surfaces of water above the level of the pipes, which surfaces ought 

 always to exceed by a few degrees the mean temperature of the house. 

 The troughs commonly employed are objectionable only in as far as they are 

 much too small, and becoming quickly empty afford a very temporary supply. 

 To be really efficient, such troughs ought to be at least 1 ft. in width by 5 

 or 6 inches in depth, and they_should extend the whole length of the house, 

 affording something like 1 square foot of water surface for every 15 square 

 feet of glass in the roof. In orchidaceous houses, and those destined to 

 the cultivation of tropical plants, a still greater surface of water is desirable, 

 and for this purpose slate cisterns, fixed immediately over the heating-pipes, 

 as broad as the front shelves, and from 1 ft. to 15 in. deep, may be ad- 

 vantageously employed. Their temperature will always exceed that of the 

 house by a few degrees, and the great surface affords an abundant though 

 gradual supply of moisture : they act also as partial reservoirs of heat, and 

 afford the only efficient means of cultivating the beautiful but much neglected 

 tribe of stove aquatics. The culture of these plants has become almost 

 extinct, solely, I believe, on account of an almost universal failure in 

 managing them, and this failure has entirely resulted from the improper 

 construction and position of the cisterns in which they are grown. In the 

 few houses where cisterns are introduced, they are generally provided more 

 for ornament than use ; the position in which they are placed, and the 

 materials of which they are constructed, forbid their being warmed, and in 

 fact the temperature of the water contained in them is always some degrees 

 below that of the house. Under these circumstances, no tender aquatics will 

 flourish : but if the cisterns be placed above the pipes, as here recommended, 

 and formed of slate, their temperature will always by a few degrees exceed 

 the mean temperature of the house, and, if their situation be light enough, 

 stove aquatics will flourish in them in great perfection. 



" It may be observed that this arrangement meets the necessity of the case 

 with exceeding accuracy, for condensation is greatest, and consequently the 

 atmosphere is most rapidly dried, when external air is coldest, and a great 

 artificial heat is maintained ; and at this very time the increased heat of the 

 pipes increases the evaporation from the cisterns. But, to insure this result, 

 the cisterns employed must be above the level of the heating pipes, and, 

 if possible, directly over them. 



" The foregoing suggestions are intended to convey a few brief and practical 

 hints to those who possess or may be about to erect hot-water apparatus. 

 For more minute details, the work of Mr. C. Hood, above referred to, may 

 be most advantageously consulted. Ample information will there be found 

 on a subject which is far more extensive, and which involves much more of 

 scientific research and calculation, than is generally supposed ; and, to those 

 who may take the trouble to consult it, it will be no longer a matter of 

 surprise that the earlier essays in heating by hot water were frequently 

 unsuccessful." 



(Tb be continued.} 



