HORTICULTURAL SOCIETY OF LONDON. 



149 



house, quantities of pipe beariniz; a different proportion to their 

 respective surfaces of glass ; the difference thus established will 

 be maintained for all temperatures, unless accidental circum- 

 stances of exposure to wind, or imperfect glazing, should cause 

 a variation, and the general heat cf all may be regulated by at- 

 tention to one fire. 



In conclusion Mr. Rogers adverted to the great importance of 

 regulating with precision the amount of moisture in the atmo- 

 sphere of a house for plants it is upon this above every thing 

 else, that the perfection or imperfection of an artificial climate 

 consists, and it is by no means one of the least advantages of 

 hot water pipes, that they do not, like brick tiues, dry the atmo- 

 sphere by absorbing its moisture. The air of all buildings arti- 

 ficially heated, is dried by condensation upon the 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. 

 Sprinkling the floor is a very imperfect and inefficient means of 

 replacing the moisture thus lost, the greater part of the water so 

 bestowed sinks into the earth, and very little 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. 



The most effectual mode of producing a moist atmosphere is 

 by considerable 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 em- 

 ployed 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 

 one foot in width by 5 or 6 inches in depth, and they should ex- 

 tend the whole length of the house, affording something like one 

 square foot of water surface for every 15 square feet of glass in 

 the roof. In Orchidaceous houses, and those destined to the culti- 

 vation of tropical plants, a still greater surface of water is de- 

 sirable, and for this purpose slate cisterns, fixed immediately over 

 the heating pipes, as broad as the front shelves, and from one 

 foot to 15 inches deep, may be advantageously employed. Their 

 temperature will always exceed that of the house by a few de- 

 grees, 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 on account of 

 an almost universal failure in manairino; thein, and this failure 

 has entirely resulted from the improper construction and position 

 of the cisterns in which they are grown. In the few houses 



