318 FRUIT CULTURE: 



Yincennes, and from the day of visiting them I have had no 

 doubt whatever that it will prove a great gain in our fruit 

 growing. The building of houses by its means is simple 

 and as easy as could be desired, although none but the 

 roughest labourers are employed; that of walls may be 

 effected even with greater ease. The Paris houses were built 

 with very rough gravel dug up on the spot. The same 

 or any like material may be used for like purposes, as 

 may burnt clay, stony rubbish of any kind, or even such 

 material as clinkers, abundant and hitherto useless in many 

 districts. I need not and cannot here go into the plan, but 

 it consists in little more than mixing a small portion of 

 cement and sand with the rougher material, and throwing 

 the mass between boards firmly adjusted to the size of wall 

 required. The mass hardens in twenty-four hours or so, 

 then the boards are elevated, another layer of concrete 

 thrown in, and so the work goes on. It will be clearly 

 seen that nothing can be better suited for garden purposes. 

 In addition to this mode, I know no reason why walls of 

 adhesive earth on a brick or stone foundation should not be 

 used with us as well as on the Continent. I have seen 

 many of these garden walls and houses perfectly sound and 

 strong many years after their erection, and looking no worse, 

 indeed better, than ordinary brick walls. 



No matter of what material the wall be made, it will be 

 desirable to whiten its surface and keep it white. Black 

 and dark coloured surfaces absorb heat in the daytime, and 

 give it out again during the night in the form of radiant 

 heat ; from which facts we might draw the conclusion that 

 walls for training fruit trees against should be black, or at 

 any rate of a dark colour. Direct experiment was, however, 

 necessary to settle this question, and M. Vuitry, who em- 

 ploys his leisure in arboriculture, has communicated the 

 results of his experiments in this direction to M. du Breuil, 

 which leave no doubt as to the proper colour to be chosen 

 for walls against which fruit trees are to be trained. He 

 has proved — 1st. That a thermometer hung during the day 

 with its face turned towards a white wall, at a distance from 

 it equal to that of a fruit tree trained against it — i.e., about 



