CONSTRUCTION OF GARDEN WALLS. 



89 



is one of their principal merits. Slate would 

 be an excellent material for this purpose, 

 and, we believe, the only one that could be 

 advantageously employed, as it is both a 

 good absorber and reflector of heat. 

 Wood would be objectionable, on account 

 of its being a positive non-conductor of 

 heat, unless it was painted black, and 

 coated with asphalte ; and metal would ab- 

 sorb and reflect heat during the heat of the 

 day, but would also absorb cold during the 

 cold at night, thus rendering the extremes 

 of day and night temperature much greater 

 than they are under present circumstances. 



These walls, as at present projected, are 

 intended to range from north to south, 

 and, without the intervention of an opaque 

 reflecting body, will afford to the trees 

 light and solar heat from the time the 

 sun's rays strike them in the morning 

 until they diverge from them in the after- 

 noon — the astragals and sash frames break- 

 ing the full force of the rays at noon: 

 they thus possessing one of the chief 

 merits of ridge-and-furrow roofs. 



With an opaque body in the centre of 

 the wall, the trees would be circumstanced 

 exactly like trees upon an east and west 

 exposure, protected by a glass screen in 

 front — the former deriving advantage only 

 from the morning, and the latter from 

 the afternoon sun. On a southern expo- 

 sure, with a heat-absorbing and reflecting 

 body between, such as slate, the southern 

 side only would derive much benefit from 

 the sun — the north nothing but protection 

 from rain and cold, with a very limited 

 supply of heat. But on the other hand, 

 instead of constructing these walls with 

 a double glass surface, were they con- 

 structed with a single surface of that 

 material, and that used on the south side 

 only, great advantages would be gained 

 by extending in length a single surface 

 instead of a double one. A glass wall 

 upon the principle shown by fig. 107, 

 having hot-water pipes placed along the 

 bottom, is in our opinion the very perfec- 

 tion of the principle; for with that ap- 

 pliance to insure a due temperature, the 

 walls running even from north to south, 

 peaches and grapes might be ripened to 

 full maturity, air and light being so 

 abundantly supplied; and it is probable 

 that on these the success depends more 

 than on heat, whatever amount of it may 

 have been obtained with a deficiency 



VOL. I. 



of both or either. Glass walls construc- 

 ted on Mr E wing's principle must afford 

 a much greater amount of these ele- 

 ments than fruit-houses as at present 

 constructed. As to the accumulation of 

 solar heat, we cannot see how this can be 

 calculated upon, because the rays of heat, 

 having passed through the glass on one 

 side, will escape by passing through the 

 other, leaving the trees within in a tem- 

 perature little above what they would 

 have if placed against a south wall. But 

 we have in the hollow glass walls full 

 security from atmospheric injuries, the 

 trees being protected from frost, snow, 

 and rain — and, what in our opinion is 

 of ^ast importance, enjoying a complete 

 security against those evaporating and 

 blighting winds of spring, which in our 

 climate are even worse than frost itself. 

 The trees being enclosed, admits of their 

 being fumigated or sulphurated, which 

 cannot be effected with a shadow of ad- 

 vantage in the case of trees on open walls. 

 Under both the modifications of opening, 

 ample means are presented for carrying on 

 the necessary operations of pruning, dis- 

 budding, thinning, and gathering the fruit. 

 The covering in at the top is of vast impor- 

 tance, as the trees will be kept dry, which, in 

 certain conditions of the atmosphere, will 

 be equal to several degrees of temperature. 



The simplicity of the construction is 

 very perfect, substantial, and cheap. 

 Could we see how, without lessening the 

 transparency, the solar heat could be ar- 

 rested from passing directly through, we 

 would without hesitation prefer them, 

 for general and late crops of peaches and 

 grapes, to most ordinary fruit-houses. 

 For the securing and hastening the 

 ripening of apricots, plums, cherries, the 

 finest Flemish pears, and the best French 

 and American apples, and for the conser- 

 vation of exotic plants, we think them in- 

 valuable. For early forcing, we would have 

 our doubts, even with hot-water pipes ; for, 

 although the internal space to be heated 

 is small, the loss of heat in consequence 

 of so large a surface of glass, without any 

 absorbent body in connection with it, 

 must be great. 



Nevertheless, with all the objections we 

 have stated, we hail the invention as 

 one that will be found to possess many im- 

 portant advantages over brick and stone 

 walls. The respectability of the inventor, 



M 



