HEATING BY HOT-WATER PIPES. 



185 



on them, for holding water for creating 

 moisture ; and, with care, these have 

 answered the purpose: but they have 

 invariably been attached to the upper 

 pipes, whereas they ought to have been 

 placed on the lower ones. The return- 

 pipes, under ordinary circumstances, are 

 seldom under 90° or 100°— a temperature 

 quite sufficient, if partially covered with 

 water, to raise a much more congenial 

 steam than could be got from the upper 

 ones, which are often much too hot for 

 this purpose. Indeed, a very judicious 

 plan is to place a wooden or brick-and- 

 cement trough under them, and keep it 

 supplied with water, when required, from 

 the cistern over the boiler. Hollow tiles 

 have been used for the tops of flues for 

 the purpose of generating steam, to make 

 up for the humidity abstracted from the 

 atmosphere of the house by the absorbing 

 properties of flues. These have the effect 

 of scalding the tender foliage when water 

 is put on them while much heated; and 

 when applied at a low temperature, the 

 water is absorbed by the material to such 

 an extent as greatly to impede the draught 

 by creating dampness in the flue. The 

 nearest approximation to the natural 

 climate in the tropics must be that pro- 

 duced by the fermentation of vegetable 

 and animal substances. " In hot moist 

 regions in the tropics," says Mr Solly, in 

 " Rural Chemistry," " plants grow with 

 far more rapidity, and vegetation is more 

 vigorous than in temperate regions. In 

 tropical countries, decay proceeds far 

 more rapidly than it does in our own 

 country. Carbonic acid and ammonia, 

 the food of plants, are produced in greater 

 quantity than here; whilst, from the greater 

 power of the sun, plants are able to assi- 

 milate more of those substances than 

 they can in colder countries." The great 

 desideratum at present, now that we 

 have a command of both heat and mois- 

 ture, is to find means of supplying those 

 indispensable gases by impregnating the 

 atmosphere of our plant-structures with 

 them. 



Wherever artificial heat is employed, 

 it has a tendency to dry up the humidity 

 of the atmosphere of the space heated : no 

 matter whether the apparatus be hot 

 water, hot air, or brick flues — all have a 

 similar tendency, although not in exactly 

 the same degree. Artificial means must, 



VOL. I. 



therefore, be used to counteract this ten- 

 dency. The following excellent remarks 

 upon this subject are by Mr J. Rogers, 

 in "Horticultural Society's Transactions :" 

 — "Closely connected with the subject of 

 heating, is the providing an adequate 

 degree of moisture in the atmosphere 

 heated ; indeed, it is upon this, above 

 everything else, that the perfection or 

 imperfection of an artificial climate de- 

 pends; and it is by no means one of the 

 least advantages of hot-water pipes, that 

 they do not, like smoke flues, dry the 

 atmosphere by absorbing its moisture. 

 But this negative advantage falls far 

 short of what is necessary. The air of all 

 buildings artificially 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. 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 expe- 

 dient : the greater part of the moisture so 

 bestowed sinks into the earth, and very 

 little, indeed, finds its way to the atmos- 

 phere 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 loosing 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," Mr Rogers thinks, "of producing a 

 moist atmosphere, is by considerable sup- 

 plies of water above the level of the pipes, 

 which supplies 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 1 foot in width by 5 

 or 6 inches in depth, and they should ex- 

 tend 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 orchid houses, 



2 A 



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