OCTOBER. 
293 
hedges for side walls, the houses were also increased in size, being 
built wider and loftier than the original ones. This step was 
adopted on sound practical deductions, for as the internal area of 
any building increases in comparison with its exterior or cooling 
surface, in proportion as it is built wider and higher, it follows 
that, when once filled with warm air, it would be longer in cooling 
in proportion to its size than in a narrow house; hence, by taking 
advantage of the sunny afternoons which usually precede frosty 
nights in the spring, you may collect a body of air in these houses 
sufficiently heated to maintain a temperature something higher 
than the freezing point through the night, even when it is several 
degrees lower than freezing externally,—a most important point 
in the erection of true Orchard Houses, as we term those where 
artificial heating is not applied, and should not be lost sight of by 
parties contemplating their erection. In confirmation of this fact, 
the houses now being erected by Mr. Rivers are still larger than 
those previously described; so that there has been a successive 
increase in their size from the commencement to the present time. 
I speak from recollection only, but I should say his last new houses 
are twenty-four feet wide (just twice the width of those first 
built), and of corresponding height, and something like 100 feet 
in length,—noble structures, and built on sound principles. We 
noticed that these houses, which are five feet high at least from 
the ground to the roof plate, are glazed down to the floor, the 
centre division being formed into large glazed squares or shutters 
running the length of the building, for ventilation. Glass all 
round gives an imposing appearance, and probably these may be 
intended for show houses; but on the score of economy the lower 
half of the sides might have been Louvre boarding, for which we 
have seen nothing better, or which more economically answers the 
purpose of ventilation and protection. These houses, 100 feet 
long by 24 wide, we were told, could be constructed for 150/. each. 
We shall, however, go into this subject more fully hereafter. 
Ventilation .—A strong discussion is now going on in respect to 
the proper ventilation of Orchard Houses. We observe that Mr. 
Pearson, of Chilwell, considers that ventilation at the apex of the 
roof is indispensable. Now, if such is the case, it would materially 
interfere with the cost and details of construction, which on Mr. 
Rivers’ plan is very simple. The roof being a complete fixture, ven¬ 
tilation being given only at the sides and ends, which, in the case of 
houses like those at Sawbrigeworth, are 100 feet long, would seem 
to most gardeners a long way apart; we must therefore look at this 
question more closely, for there cannot be a question but that in a 
span-roofed house the heated air will rise to the highest part of the 
interior, and that in such houses the air will increase in rarety 
and temperature from the floor to the angle of the roof. Mr. 
Rivers maintains that his mode of ventilation is amply sufficient 
to correct this to an extent that would render it no longer un¬ 
favourable to vegetation, or the production of red spider, which 
invariably attack vegetation exposed to an overheated atmosphere. 
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