GLASS STRUCTUEES AND APPLIANCES. 



49 



No plant in pot or tub should ever be placed on 

 the soil of border, or stone or tile floor, without being- 

 raised on tiles, pebbles, or some other contrivances, to 

 permit of the free egress of water and to prevent the 

 ingress of worms. More plants are crippled and 

 finally killed for lack of these precautions than by 

 any other means. The mere drainage within pots 

 or tubs, however ample, is almost useless unless the 

 water has free egress from it, which it cannot have 

 when flat-bottomed pots are placed on the firm level 

 surface of the soil, or the more impervious one of a 

 stone or tile floor. 



Roofs of Conservatories.— These, it will be 

 already seen, vary as much in form as in size, and 

 that is saying a great deal. So long as they are 

 waterproof, and admit a full amount of light and 

 a sufficiency of air, the matter of form is of less 

 moment than is generally supposed. Most of the 

 almost endless diversity of forms may be brought 

 under, three general heads — ^that of lean-to, span, 

 and cuivilinear-roofed houses. The lean-to is the 

 most generally used, as it may be set up against the 

 waU of the dweUtng-house, offices, or garden, which 

 is mostly found ready to hand. By raising a front 

 wall up two feet or a yard high, parallel with this, 

 and placing a glass sash about the same height on 

 the brick- work, and joining all together with a wall- 

 plate, the front of such houses is formed. A few 

 rafters spanning the distance from front to back 

 form the framework of the ordinary lean-to con- 

 servatory. Of course the distance between the two 

 walls, which may range from four feet to twelve or 

 even more, determines the width of the house, while 

 the disparity of height between the front and back 

 walls measures out its atmospheric area and regu- 

 lates its angle of inclination. Provided the latter is 

 sufficient to shoot ofi the water freely, its exact 



incidence is of less importance than has been gene- 

 rally assumed in most of the text-books. 



Most of these dwell at length on the great import- 

 ance of carefiiUy adjusting the angle of elevation to 

 the latitude of the place, and the consequent direct- 

 ness or obliqueness with which the sun.'s rays will 

 shine on the roof at any given hour of the day. But 

 all this is somewhat complicated, and is more apt to 

 bewilder or perplex than prove of use in guiding 

 aright the mechanic, or amateur or practical gar- 

 dener, in search of the most useful angle for his tiny 

 green-house or more imposing conservatory. 



Best Angle for the Hoof of Conserva- 

 tories. — This will be found to Ke between the ten 

 degrees enclosed within the compass of 35° and 45°, 

 40° being a good mean for most parts of Britain. The 

 angle is meant as measured from a horizontal line 

 at the height of the top of the front wall. The 

 steeper the angle, the greater in general the amount 

 of light which the roof wiU absorb or transmit ; the 

 flatter, the less. Hence conservatories with a southern 

 aspect may have a flatter roof than those facing the 

 west, east, or north. It is a popular error, however, 

 bom and fostered of the days of dear and semi- 

 opaque glass, that conservatory plants wiU not thrive 

 unless the house faces south, or nearly so. Modem 

 glass of good quality is so transparent as hardly to 

 oDstruct any of the sun's rays; and this, with, im- 

 proved methods of construction, enables the cultiva- 

 tor to command a tolerable amount of success in 

 houses of any aspect, imless those due north ; and 

 even in these verj' fine Eems, Mosses, and other 

 foliage plants may be grown in great perfection. 



There are many methods for determining the 

 angle of elevation, but the following table, given by 

 Thompson in the " Gardener's Assistant," and by 

 other authorities, will save all trouble. 



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