GARDEN STRUCTURES. 



199 



porary coping; whilst in summer they would 

 prevent the foliage from being moistened by 

 dew, the beneficial effects of which cannot be 

 secured by artificial watering. 



Temporary copings are of great utility, espe- 

 cially during the prevalence of late spring frosts. 

 The heat accumulated in the materials of the 

 wall during the day is given off whenever the 

 air is colder than the wall. The cold air coming 

 in contact with the surface of the wall becomes 

 heated, and consequently lighter; it therefore 

 ascends, and the heat is lost, so far as vegeta- 

 tion is concerned. Broad copings obstruct the 

 free ascent of warm air, which then accumulates 

 where it is wanted, at the surface of the wall. 

 We have seen the young shoots of vines cut off 

 by frost as far as they had pushed beyond 9-inch 

 coping-boards, whilst all that were under shelter 

 of the boards were safe. 



To support coping-boards, iron tubes with an 

 internal diameter of about 1 inch, and in length 

 4 inches more than the thickness of the wall, 

 should be used, so that, when inserted across, 

 the ends would project 2 inches beyond the 

 face of the wall. The tube should be secured 

 by having a piece of iron fixed round its middle 

 and built in the wall; a piece of rod-iron with 

 an eye at top would answer the purpose, and 

 if the cold tube were drawn through the eye 

 when red-hot, it would afterwards remain quite 

 tight. There should be a hole drilled through 

 the tube horizontally about 1 inch from the 

 end, so as to admit an iron pin about f inch in 

 diameter. A bracket should be formed with a 

 round prong to fit into the end of the tube, 

 where it can be secured by the iron pin being 

 passed through a hole corresponding with that 

 in the end of the tube, and on the brackets the 

 coping-boards can be fixed, taking care that they 

 fit closely to the wall, to the under side of the 

 permanent coping, or, which is better, to both. 

 If it should be desirable to have the coping- 

 boards hinged, so that they may be folded up 

 in warm weather and let down in cold, the fixed 

 tubes will also afford eligible means of doing so, 

 for a wooden bar can be secured to the tubes so 

 as to fit close to the coping, and to this bar the 

 coping-boards may be attached by hinges. These 

 should be such as will admit of the boards being 

 removed, and the bar left, in case it should be 

 wanted for supporting materials for protecting 

 the fruit from birds and wasps. The tubular 

 fixtures will also afford facilities for extending 

 protecting materials to a greater or less distance 

 from the wall, for this can readily be effected by 

 means of rods pierced with several holes and 



inserted into the tubes, more or less according 

 to the distance at which the netting or other 

 material may be required to hang from the 

 wall. When not otherwise occupied, wooden 

 plugs, with neatly formed heads, should be in- 

 serted into the mouths of the tubes to keep out 

 the wet. 



Flued Walls. — These are seldom if ever built 

 nowadays, and where they exist their use as 

 heated walls has been generally discontinued; 

 but good crops of various kinds of fruit have 

 been produced on them, and in northern .situ- 

 ations they may be employed, not only in case 

 of frosty nights in spring, but also for ripening 

 the wood in autumn. 



II. Glass-houses, Pits, and Frames. 



The fundamental principles of good glass 

 structures for the cultivation of plants are the 

 maximum of light in winter, good ventilation, 

 the command of sufficient artificial heat, and a 

 waterproof roof. 



The Roof. — It is well known that the rays 

 of light, in passing through glass or any other 

 solid transparent medium, lose much of their 

 energy as regards their effect on vegetation. 

 If, after passing through the glass, the rays of 

 light have a considerable space to traverse 

 before they reach the foliage, the latter is in- 

 sufficiently acted upon, even when the glass is 

 very transparent; and when this is not so, 

 either from its original quality, or from not 

 being kept clean, their effect is still further 

 diminished; and as regards the direct solar 

 rays, the intensity of their action depends 

 much on the greater or less obliquity of the 

 angle at which they impinge upon the surface 

 of the glass. All these matters being taken 

 into consideration, it follows that the glass 

 should be as close to the vegetation as circum- 

 stances will permit; that it should be as trans- 

 parent as possible, but more especially so if the 

 plants are not very near it; and that it should 

 be so placed as to form a plane, on which the 

 sun's rays may be perpendicular at that period 

 of the season when their greatest effect is 

 most wanted; as, for example, when fruit that 

 is being forced is undergoing the process of 

 ripening. 



As a general rule, houses intended for early 

 forcing should have the glass more upright than 

 those for later crops; and the angle of elevation 

 should also be increased according to the lati- 

 tude. If for any purpose an angle of 30° is 

 proper in latitude 50°, then in latitude 57° an 

 angle of 37° would be requisite. 



