IIOTHOPSK. 



HOTHOtTSK. 



741 



which the pipe* are level, or nearly 10, presents several advantages over 

 other method* of heating. Troughs can be arranged along the whole 

 length of the pipe, which, when filled with water, will produce a gentle 

 but constant evaporation. Besides the supply from thu source, a Urge 

 quantity of (team may be safely introduced from the boiler, provided 

 the violence of its ingress be a little broken by a perforated sheet of 

 metal, or any similar contrivance. Another source of moisture is sup- 

 plied by the reservoir, which, with moisture from the soil in which the 

 I>lant are grown, and from the wetted floors, ought to keep the atmos- 

 phere of the house sufficiently moist during the night The elasticity, 

 however, of the vapour will be very great, particularly in cold nights 

 when much fire-heat is required ; and in such a state of the weather 

 the condensation from the coldness of the glass will be increased. The 

 atmosphere of the house is not only deprived of its moisture by this 

 process, but a serious loss of heat by radiation from the glass takes 

 place at the same time. This loss of bent and transmutation of 

 moisture resulting from the radiation of the glass, although little 

 attended to, demands the most serious care. It admits of no remedy 

 but the interposition of some medium between the glass and cold sky ; 

 and such substances as are the worst conductors of caloric, and which 

 will also keep the glass dry, are of course the best A woollen net 

 mounted on a roller, with pulleys attached, would have a very bene- 

 ficial effect if closely covered by light wooden shutters or a tarpaulin. 

 And as it has been proved that the rays of the sun are frequently too 

 powerful for hothouse vegetation, the netting would likewise be occa- 

 sionally very useful as a shade; and with this provision the roof cannot 

 be made too transparent, as previously stated. 



It has been shown that iron roofs occasion an obstruction of light to 

 the extent of only one-third of that which takes place when wood is 

 employed. The iron roofs are therefore preferable, although, apart 

 from the greater original expense, there are still some objections to 

 them. Formerly the chief objection was the breakage of glass likely to 

 result from the expansion of the metal ; but the severity of the frost in 

 1838 has proved that this objection was groundless, for very little 

 breakage occurred in the iron roofs compared with what took place in 

 wooden ones ; and it may be fairly asserted that none whatever was 

 broken from contraction of the metal ; nor can any breakage take place 

 from its expansion if the glazing is performed in summer, or the glass 

 cut so as to fit in with ease, or the panes made one-thousandth part of 

 an inch less than the bed between the rebates of the bare in which 

 they are placed. The principal remaining objection is that of the 

 rapid abduction of heat Plants never do thrive so well in the 

 proximity of iron as in that of wood, and this is probably owing to 

 the wood being a slower conductor of caloric. Supposing a bar of iron 

 is heated to 100* by the sun's rays, and then syringed with water, it 

 will instantly become very cold, in consequence of evaporation ; and if 

 any plant be in contact with it, or nearly so, the juices will experience 

 a chill. In many instances, therefore, where plants require to be close 

 to the glass, such as in propagating houses and pits, wood is certainly 

 preferable to iron. Again, when a wide and also lofty house is to be 

 glazed, iron is more proper ; for besides the quantity of rays lost by 

 reflection of glass and obstruction from rafters, those that do pass into 

 the interior are so weakened, that when they reach vegetation remote 

 from the glass they do not appear to be effective in performing the 

 requisite functions in a perfect manner; but of course better when the 

 roof is of iron than when wood is employed. 



Various modes of ventilation are in use. One which was considered 

 a great improvement has not been found to be so, namely, the having 

 ventilators in front at the lower angle, and corresponding ones in the 

 back wall near the top inside, communicating with the external air by 

 means of openings in the south side of the parapet. Sometimes this 

 mode appears to have little effect, and the temperature ascends too 

 high, till the movement of a slight breeze outside causes instantly a 

 rush of cold air. Ventilation should be so contrived as to be suffi- 

 ciently effective in preventing excess of heat ; but at the same time it 

 should be perfectly at command, so that it may be employed when 

 requisite in the most limited degree. No method should be finally 

 adopted until it is put to the test by trying whether, under any agi- 

 tation of the external air, a candle will burn steadily inside if placed 

 near the apertures by which the air is admitted. 



In all forcing-houses tanks should be placed for supplying water of a 

 temperature more suitable to the nature of the vegetation than that 

 from a pump out of doors. Nothing can be more injurious than cold 

 water applied to the roots and tops of tropical plants, or others in a 

 forcing state under a high temperature. The rain and dews which 

 supply the plants of warm climate* cannot be much below the mean 

 temperature of the climate ; and if only equal to the minimum, xtill it 

 would be between 20 and SO* above that of spring-water in Britain. 



To these general remarks upon the principles of constructing hot- 

 houses, a few observation* of detail require to be added. Greenhouses 

 and conservatories are commonly included in the appellation of hot- 

 house. The only difference between them is, that fires are seldom 

 used in the greenhouse unless in very severe weather, while the 

 hothouse is constantly kept at a high temperature ; but so far as the 

 building is concerned, they may be considered as the same. A green- 

 house is for keeping and growing the plants of temperate countries ; 

 while a hothouse is used for forcing fruit*, or for growing plants which 

 are indigenous to tropical region*, Hothouses may be classed under 



four different heads, namely, the dry ttovt, the damp stotr, the bark 

 fore, and the forciivj-koutc. 



The dry tioit, as the name implies, is used for the cultivation of 

 plants which do not require much water; such as the .liil'.-n-iit species 

 of Cacti, some Euphorbias, and other Succulents of like habits. The 

 management of such a house is very simple. The temperature during 

 the winter months should never exceed 55* of Fahr. No water should 

 ever be given at that period, unless the plants show signs of suffering 

 from want of it ; indeed very little water should be given at any season, 

 except when the plants are growing. In spring, or early in summer, 

 most of the plants will show an inclination for growth, and then they 

 may be watered about twice a week, but this must be done with great 

 caution, otherwise they are very apt to rot During summer fires may 

 be discontinued, and plenty of air given in fine weather. The plant* 

 will probably get covered with dust and will be unsightly ; in this 

 case they may be syringed, but caution must be used in doing this, 

 especially with melon-shaped Cacti, as the water lodges in their hollow 

 tops, and eventually destroys them, if allowed to remain. 



The damp itore requires treatment of an opposite description. 

 Instead of being kept dry like the last, its atmosphere should be 

 always excessively humid, except in the winter season, when the sky 

 is generally cloudy, and the sun's rays weak. Various methods are 

 adopted to keep the atmosphere in this saturated state. When the 

 house is heated with common smoke flues, the most simple way is to 

 throw water frequently upon them, and also upon the passages and 

 other places, from which it will evaporate, and surround the plants 

 with a moist atmosphere. Sometimes a channel is formed with cement , 

 upon the upper surface of the flue, which keeps the water from running 

 off. This is a very excellent plan, as it may be so made that it will 

 hold a considerable quantity of water, which will be continually evapo- 

 rating, and serve the same purpose as that of a person frequently 

 throwing water upon it When the house is heated with hot-water or 

 steam-pipes, it is a good plan to get small ridges cast upon the sides of 

 the pipes, if they are flat, or, if they ore round, small cisterns made of 

 lead or zinc will answer the purpose, which can be used in the same 

 manner, and will have the same effect as the channel upon the smoke 

 flue. With the exception of a few months in winter, the damp stove 

 must be regularly syringed twice every day. This is indispensable to 

 the health and vigorous growth of the plants, and also necessary in 

 order to keep down insects. The quantity of water which the plants 

 in this house will require depends entirely upon the state of the 

 weather and their own growth; in winter they will need little, as 

 spring advances they may be watered more freely, and in the summer 

 season they will all require to be watered twice and some of them 

 three times a-day ; of course those which are growing vigoroiuJy w ill 

 require the most It is a very bod plan, although one which is too 

 often practised, to water almost at random, giving all the plants almost 

 an equal share, regardless of their different capacities. Some will 

 require a very abundant and constant supply, others will almost live 

 upon the atmospheric moisture that surrounds them. Another tiling 

 to be attended to in the treatment of this stove is the placing of the 

 plants. Most of the kinds grow very freely, and if they have not plenty 

 of room they will very soon get crowded, and instead of growing bushy 

 and handsome, the result will be an unsightly specimen, with a long bare 

 stem and a few leaves upon its top. To prevent this they must be regu- 

 larly looked over, tied up, and kept clear of each other ; elevating some, 

 depressing others, and giving the whole not only enough of room but 

 also a natural appearance. The temperature of this stove, like that of 

 the dry-stove, should not be the same at all seasons ; in winter, when 

 the plants are in a torpid state, 65 or 60 of Fahr. is quite warm 

 enough ; when vegetation begins to take place, as spring advamv-. it 

 may then be gradually raised to 70 ; and during fine weather, in the 

 middle of summer, fires may be discontinued for about three months ; 

 but this must depend entirely upon the weather. The thermometer 

 should never be allowed to sink lower than 60. 



The bark (tore, when it is of large dimensions, consists of a pit in the 

 middle of the house, surrounded by a brick wall, leaving as much room 

 round the sides as will form a passage to walk in. This pit in 

 generally from four to six feet in depth, one-half below and the other 

 half above the level of the floor of the house ; but this depends chiefly 

 upon the height of the roof and the object in view. In smaller houses 

 no space is left for a passage, and the inside is entirely occupied by the 

 pit. The pit is filled with bark (commonly called tan, from its having 

 been used previously by the tanners), and after being allowed to sink a 

 little and ferment, the pots containing the plants are plunged more or 

 less deep as prudence may suggest It is dangerous to plunge the pots 

 too deep at first, before the heat of the bed is fully ascertained, because 

 in that case the roots are very liable to be burned ; the better way in 

 to plunge the pots only about one-third at first, and deeper afterwards. 

 Sometimes leaves are mixed with the tan ; the reason being that they 

 are in some parts of the country more easily procured. When the heat 

 begins to decay, the bed must be turned over and a little fresh tan 

 added ; and whenever a new bed is made, a little of the old tan should 

 always be mixed with the new. This stove is heated independently of 

 the bark, of which the principal use is to warm the roots of the plants. 

 A bark bed is found useful in the cultivation of all those kinds of 

 plants which are grown in the damp stove ; orchidaceous plants, for 

 example, succeed admirably in this way. The treatment of it, > far 



