GREENHOUSE 



glass. The weight of most of the glass of American 

 manufacture is about 2 ounces greater per foot than 

 the imported, and therefore proportionately stronger. 

 This greater strength is of considerable importance in 

 the additional security which it affords from damage 

 caused by that enemy of the Horists, the hail storm. 

 There is a great difference in the qu.ility of the glass 

 made by different manufacturers in its adaptation to 

 Greenhouse use. This difference is caused chiefly by 



GREENHOUSE 



689 



Heated 



?2. Even-span Houses. 



ith water in east-iron pipes. 



the quality of the material used iu the glass, making it 

 more or less opaque, aud iu the number of small knots, 

 causing lenses, which concentrate the sun's rays md burn 

 the foliage of the plants. This last defect in the glass 

 cannot be wholly guarded against, as the product of a 

 factory does not always run the same, so that any favor- 

 ite brand cannot be fully relied upon in this respect. 

 The lenses which burn will be found in all the dif- 

 ferent grades of glass, firsts, seconds and thirds, with 

 little, if any difference, the grading being done chiefly 

 for other defects, such as affect the value of the glass 

 for window purposes. For these reasons, in selecting 

 the glass for a Greenhouse, it requires experience to 

 decide what make of glass it will be best to purchase. 

 It will be well to purciiase from some one who makes a 

 specialty of furnishing glass for Greenhouses, or call in 

 the aid of some friend who has had experience in build- 

 ing, and can give intelligent advice. 



The second quality of glass is usually selected for the 

 best Greenhouse work. The standard widths are from 

 12 to 16 inches, and lengths vary from 16 to 24 inches. 

 A favorite size is 16 by 24 inches. This is about as large 

 as it is practical to use double thick glass, and makes a 

 roof with comparatively few laps. 



It is not safe to purchase fourth quality of glass or 

 the so-called "Greenhouse glass" frequently offered by 

 window glass dealers, as both of the grades contain the 

 culls and lights only fit to glaze cheap sash for market 

 gardeners, and is of doubtful economy even for this 

 purpose. Rough plate or ribbed glass is not adapted 

 fur a Greenhouse roof. It not only obscures the light, 

 but is so brittle that the breakage is greater than with 

 the double thick sheet-glass. It is also very difficult to 

 set it so as to make a tight roof on account of the un- 

 even lines of the ribbing. Recently a few conservatories 

 have been glazed with thick, polished plate-glass, mak- 

 ing very handsome roofs, but rather expensive. 



To set glass properly in a Greenhouse roof, ii should 

 be bedded in the best putty on wood sash bars and 

 lapped at the joints The bars should be spaced accu- 

 rately, so that the g ass will fit the rabbets with not 

 over one-sixteenth of an inch allowance, and the panes 

 of glass should lap each other not more than from one- 

 eighth to one-quarter of an inch. Zinc shoe nails fasten 

 the glass best, using from 4 to 6 to each pane, accord- 

 ing to the size of the light. No putty shonld be used on 

 the outside of the glass. A comparatively new system 

 of glazing has been adopted by some florists, in which 

 no putty is used, but the glass is placed directly on the 

 rabbets of the bars and the ends of the panes are butted 

 together and held in place by wood caps fastened to 

 the sash bars. This system does not make a tight roof, 

 allowing considerable water to enter the house through 



the joints, nor does it provide any means of escape for 

 the condensed water from the under side of the glass, 

 which is a very serious objection. In ordinary glazing, 

 where each light laps over the one below, the condensed 

 water passes through the joints to the outside, forming 

 a perfect remedy for this trouble. The difference in 

 the cost is very slight, it anything, provided the work 

 is equally well done, as the value of the putty omitted 

 is fully offset by the extra cost of the caps. 



The painting of a 

 Greenhouse roof is a 

 very important part of 

 the work. Owing to the 

 extremes of heat, cold, 

 dryness and moisture to 

 which it is exposed, the 

 conditions are decidedly 

 different from ordinary 

 buildings. Three-coat 

 work is the best. The 

 priming coat on the wood 

 work should be mostly 

 oil, and, as far as possi- 

 ble, the material should 

 be dipped into a tank of 

 paint. Iron and steel 

 framing material shonld 

 be primed with a metallic 

 paint. The priming coat 

 should be applied before 

 the material is e.xposed to the weather. The material 

 of the second aud finishing coats should be pure lin- 

 seed oil and white lead. Experience has shown that 

 this material is the best for this work. The color should 

 be white, or a light tint of any desired shade may be 

 used, but no heavy color should be adopted which 

 requires coloring matter in place of the lead in the 

 mixing. Each coat should be applied thin and well 

 rubbed out. While the appearance may not be quite 

 as fine when the work is first done, the paint will not 

 peel off, and will last longer and form a better protec- 

 tion for the structure than when it is put on in thick 

 coats. It will also form a good base for repainting, and 

 this should be done in asiniilar manner. It is economi- 

 cal to repaint a Greenhouse every two years, and gen- 

 erally one coat will be sufficient. 



Plant Tables. — Stsiges for plants in pots or raised 

 beds for planting out usually cover the entire area of a 

 Greenhouse, except the walks, and their cost constitutes 

 a considerable proportion of the expense. Palms are 

 usually grown in solid beds or in pots or boxes sitting 

 ou the ground. Many vegetables are grown in solid beds 

 near the ground level. Roses and carnations are usu- 

 ally in raised beds. Angle-iron frames supported on 

 adjustable gas pipe legs, with slate or tile bottoms, form 

 the best plant tables (Fig. 99,") I . Wood bottoms, which 

 can be readily renewed, are frequently substituted, sav- 

 ing a part of the first cost. When the table supports are 

 I'F wood care should be taken that they are not fastened 



993. Details of gutter. 



against any part of the framework of the house, unless 

 iron brackets are used so as entirely to separate the 

 woodwork. 



VentUation. — T^o Greenhouse is complete without a 

 good ventilating apparatus. About one-tenth of the roof 

 should be arranged to open or close for ventilation, 

 though this percentage will vary according to the form 

 of house and the purpose for which it is used. It is not 



