58 



Garden and Forest. 



[January 29, 1890. 



if the sun's rays>strike glass roofs at right angles the greatest 

 economy of light will result. The rools were, therefore, built 

 with such slopes that they would stand as nearly as possible at 

 right angles to the sun's rays in the coldest months of the 

 year. It soon became evident, however, that in the houses 

 of most approved construction the slanting rays of morning 

 and evening must be largely reflected. Hence, there arose 

 various special forms of roofs designed to present some sur- 

 face at right angles to the sun at all hours ok the day. The 

 most popular of these was the curvilinear roof. In its ideal 

 conception it demands a house circular or nearly circular in 

 form. Various fluted roofs were also devised ; the most 

 famous of which was one erected at Chatsworth, by Sir 

 Joseph Paxton. This latter style of roof demanded so much 

 more material that much additional cost was incurred with 

 little gain in the amount of light. The curvilinear roof, in its 

 modified forms, is still popular for conservatories, but it is not 

 adapted to the forcing of vegetables. 



The old-fashioned circular and dome-shaped houses have 

 come to be historical curiosities. They possess a radical 

 defect ; the roof is too high, too far away from the plants. We 

 are now reversing the endeavors of the old gardeners by tak- 

 ing our plants to the light rather than by taking the light to 

 the plants. In other words, we must get our plants near the 

 glass if we demand quick growth. Fifty years ago Loudon 

 was one of the first to perceive the defects in the old houses. 

 " It is found," he says, " that the rays of light, after passing 

 through glass roofs, lose their influence on the plants within 

 in proportion to their distance from the glass. Hence, for 

 general purposes a long, narrow house is the best." Loudon's 

 statement was largely a prophecy, and we are reaping the 

 realization of it. The ideal form of a forcing-house is one 

 which is long, narrow, low, and more or less flat. It is more 

 economical in construction than the old style of house, while 

 the results obtained are incomparably better. Every gar- 

 dener knows that if he would grow good and profitable crops 

 of any low vegetable in a house he must get his plants near to 

 the glass. The low and narrow houses possess other advan- 

 tages over the old-fashioned circular and rectangular struc- 

 tures. Or, to quote Loudon again, "there is another reason 

 in favor of narrow houses where perfection of growth and 

 economy are objects, which is, that a considerable portion of 

 the heat by which the temperature of hot-houses is main- 

 tained, is supplied by the sun." Sun heat is better than arti- 

 ficial heat. The curvilinear form of roof is now combined 

 with the long and narrow form of structure, and this gives a 

 house of peculiar value for growing some ornamentals, 

 because it gives sufficient height for them to grow without 

 greatly increasing the height of the house. For the forcing 

 of kitchen garden vegetables, however, this added height of 

 the curvilinear roof is a positive disadvantage. And all curvi- 

 linear roofs are more expensive than direct roofs. 



Of recent years we have also added greatly to the light in 

 houses by the use of large panes of glass. The glass is also bet- 

 ter than it was formerly. This improvement of glass lies: (1) 

 In greater transparency, due mostly to greater thinness, and (2) 

 In greater regularity in its surfaces. Early in the century 

 panes 3x5 inches were largely used, chiefly because panes of 

 this size could be made very thin and regular. When larger 

 panes beg:an to be used better results were not reached, simply 

 because the surfaces of the glass were so uneven that much 

 light was reflected and refracted. 



The second feature of improvement is found in methods of 

 heating. No subject connected with glass structures has been 

 the occasion of such violent discussions during the last few 

 years as the various methods of heating. The fact that these 

 discussions exist is proof of progress, for agitation always 

 means revolution or improvement. We are emerging from 

 the old hot-water system into better and more economical 

 methods. These later methods are steam heating and im- 

 proved hot-water heating. The old style of cast iron pipes 

 laid exclusively under the benches is being replaced by ordi- 

 nary gas-pipe, whether the heat be applied by hot water or 

 steam. In fact, the methods of piping glass houses are now 

 almost identical in both systems. In either case the heat is 

 carried from the furnace through one main pipe or riser 

 which passes through the house near the top. From this 

 riser as many returns are taken as are necessary, and the steam 

 or water is returned to the boiler underneath the benches. 

 About the only difference in piping for steam and hot water 

 lies in a little more careful grading of the pipes for hot water, 

 and the highest point in the hot water riser is usually at the 

 further end of the house, while the highest point in the steam 

 riser is approximately over the furnace. These systems of 

 heating introduce a new principle into the method of forcing 



plants ; a part of the heat is applied above the plants rather 

 than being entirely applied as bottom heat, as formerly. This 

 of itself presents some advantages. It allows of greater uni- 

 formity in the temperature of the house, in proportion to the 

 extent of heating surface, because it supplies some heat near 

 the glass where the greatest radiation takes place. The piping 

 under the benches is so much in excess of that above them, 

 that good bottom heat is secured. 



The common question now among greenhouse men is, 

 which is better, steam or hot water? A Yankee would reply 

 by asking the question what is meant by hot-water heating ? 

 If the old system of hot-water heating is meant, then I should 

 say unhesitatingly that steam is better. But if the questioner 

 has in mind the more modern and improved methods of hot- 

 water heating, then I should prefer not to answer for all cases. 

 It is undoubtedly true that for small houses the modern hot- 

 water system is the better; and it may be that it is better in all 

 cases. For myself, however, I have preferred steam, and I 

 am using it in my houses. I have no doubt that the ideal sys- 

 tem of heating is going to be a combination of steam and hot 

 water. In other words, the ideal system will use steam when- 

 ever or wherever steam is found to be better, and it will use 

 hot water in the same apparatus whenever hot water is better, 

 as in mild weather. In fact, most of our steam plants can be 

 used almost equally well for hot water. Let us suppose that 

 we have a low pressure steam heater and that our house is 

 piped for ordinary steam heating. When running with steam, 

 we simply keep the water low in the furnace, so that there is 

 room above the water for the storage of steam. If, now, upon 

 any day I wish to heat with hot water, I simply fill my furnace 

 full of water and run my plant as before. The expansion of 

 the water by heat will force it through the pipes as if it were 

 steam. There are but two or three matters of detail which 

 demand attention. Some provision must be made for the ex- 

 pansion of water beyond the capacity of boiler and pipes. 

 This expansion is provided for by simply taking out of the 

 riser or return near the boiler a three-fourths-inch gas-pipe 

 and carrying up this pipe several feet into a tank. The higher 

 the tank above the furnace, the greater will be the pressure 

 upon the hot water and the hotter will the water become. 

 Under a pressure of forty pounds, the water will reach a tem- 

 perature of about 300 degrees, which is a higher temperature 

 than is attained by steam under any ordinary pressure. A 

 stop-cock, preferably a stop and waste, should be inserted in 

 the small gas-pipe near its union with the main, in order to 

 close the circuit when steam is used. If the boiler is supplied 

 from water-works an expansion-tank is not necessary, unless 

 the pressure is very great, for the water may be turned on per- 

 manently and expansion will simply back the water up into 

 the water works system. In using the steam plant for hot- 

 water heating, the safety valve must be fastened down to hold 

 the water in. When steam is used again it is only necessary 

 to draw off most of the water from the boiler and to close the 

 cocks in the expansion-tank. 



Inch gas-pipes are probably the best size to use in heating 

 glass houses, because they present a greater heating surface 

 than any other pipe which can be economically used. That is, 

 small pipes and more of them is a better system thanfew large 

 pipes. A more even and economical distribution can be se- 

 cured by their use. 



In practice it is found that twenty feet is about the maxi- 

 mum profitable width for a forcing-house. If a low house is 

 desired, for forcing Radishes, Lettuce or other low plants, a 

 much narrower house is advisable, unless it can be built upon 

 a slope, where a two-thirds span can be used. Very narrow 

 houses contain so small a body of air that the temperature is 

 more difficult to regulate than in a wider house. The house 

 should be low. The sides range from two to five feet, and the 

 gable stands from seven to twelve feet above the surface in 

 our best modern forcing-houses. The glazing is done upon 

 permanent sash-bars, as more light can be secured by this 

 method than by roofing with sash. The details of construc- 

 tion must be adapted to individual circumstances; but the old 

 bugbear of great expense may be dismissed. I have built two 

 good houses, each twenty by sixty feet, inside measure, at a 

 combined cost of building, including heat, of about $1,500. 

 And these houses are much better than common commercial 

 forcing-houses, which can be built much cheaper than this. 



In conclusion, it may be said that there are six general es- 

 sentials to successful forcing of plants : (1) Bottom heat. (2) 

 Abundance of light. (3) Proximity of plants to glass. (4) 

 Fresh air. We must outgrow the notion that we ventilate 

 simply to cool off the house. The primary object of ventila- 

 tion is to give fresh air, and this should be secured without 

 allowing drafts upon plants or changing the temperature of 



