82 THE FLORIST. 



But it is not so much entire erections of glass for fruit-growing 

 as the casing or covering of existing walls which we more particu- 

 larly wish to notice, as the latter present advantages which neither 

 glass walls nor orchard-houses confer ; and if the walls are covered 

 with trees at present in a bearing state, the cost of covering such 

 with glass will not be a very expensive affair, while the certainty of 

 a crop of fruit of first-rate quality, taken in connection with the 

 number of years such a protection -will last, are, to me, valid reasons 

 for recommending a plan at once safe^ and, in the long run, eco- 

 nomical. 



One great advantage in favour of covering existing walls, as 

 compared with erections entirely of glass, is the retention of heat for 

 a considerable time after the direct effect of the sun-rays have ceased 

 to act on them, the result of which is, the interior air inclosed be- 

 tween the glass and wall will take a longer time to reach its lowest 

 point than in orchard-houses, which, again, have the advantage of 

 glass walls, in this respect. 



To explain this more fully, I may remind my readers that some 

 substances or materials receive heat, and consequently part with it, 

 more slowly than others ; hence, in comparing the interior of glass 

 cases against a wall of brick, or similar materials, as a medium for 

 fruit-trees with houses built entirely, or mostly of glass, it must be 

 obvious that the brick wall will take up some part of the heat 

 passing through the glass into the house during sunshine, giving it 

 out again whenever the inclosed air becomes cooler than the wall ; 

 whereas, with a house having glass on all sides, a portion of heat 

 entering the house from one side will pass through on the other ; or 

 rather will cool rapidly by coming in contact with glass acted upon 

 by an external air many degrees colder than the air within. Such 

 will always be the case, in a greater or less degree, even when such 

 houses are placed (as they always should be) in the direction of 

 north and south. By a comparison of the temperature of the interior 

 of orchard houses and glass walls with the external air, it does not 

 appear there is much gained in temperature, epeciaUy with glass 

 walls, for reasons explained above ; but dryness is in a great mea- 

 sure secured; and with that a low temperature is comparatively 

 harmless, while the rapid transition from one extreme to the other — 

 a high temperature to an injurious low one, so frequent in our 

 chmate during March and April — is mitigated ; 

 ° in addition to which, the increase of solar heat, 



c ^^^^TT^ J. a. obtained through the medium of glass during 



i-'"^!fJi !C^^" summer, the dryness of which can be adjusted 



\ / according to the stage of the plants' growth, is 



\ X not only favourable for carrying on the fruit to 



^ perfection, but the wood of fruit-trees subjected 



SECTION OF SASH-BAR. ^^ g^^j^ advantasTCOus conditions, is sure to be- 



a, bar, lower part ; b, . ° , , j /• ^^^ 



bead, to be screwed on come Well ripened, hard, and nrm, -vvith nume- 

 f:7:,^^^^e^£^l rous well-developed buds, so as greatly to in- 

 wood and glass, for strips crease the chances of a succeeding crop. 



of India-rubber. 



