August 1, 1878. ] JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 81 
WEEKLY CALENDAR. 
Day , Day Average * Cloek 
oe of AUGUST 1—7, 1878. ers Sun Sun | Moon | Moon | Moon’s ock | Day 
Month' Week GUS pel LS ey ean Rises. | Sets. | Rises. | Sets ‘Age. before = we 
Day. |Night.)Mean.} h. m.| h. m.| h. m.| h. m.: Days. | m. s. 
SI Abie 76.1 | 50.9 | 63.5 4 25 | 7 47| 7 49] 8 39 3 6 6 | 213 
9 FR 70.6 | 52.0 | 64.0 4 27 7 45 9! 16. 8 54 4 6 2 | 214 
3 Ss Southampton and. Otley Shows. 74.9 | 50.9 | 62.9 4 28 7 441/10 43 9 10 5 5 57 | 215 
4 | SUN | 7 SUNDAY AFTER TRINITY. 75.7 | 51.3 | 63.5 4 30| 7 40} 0210] 9 28 6 5 52 | 216 
5 M Bank Holiday. f J 74.0 51.4 | 62.7 4 31 7 38 1 37 9 50 y 5 47 | 217 
6 TU Royal Horticultural Society—Fruit and Floral Com- | 72.9 | 51.1 | 62.0 A383 i oY Sy pelea LONG 23: 8 5 40 | 218 
vf WwW { mittees at 11 A.M. | 74.4 50.8 | 62.6 4 34 7 36 SUL S17, 9 5 34 | 219 
From observations taken near London during forty-three years, the average day temperature of the week is 74.19; and its night temperature 
51.2°. 
THE VENTILATION OF GLASS HOUSES. 
e 55S the ventilation of our glass houses capable 
4 of modification ? This is a question that has 
(24 exercised my mind for some time, and the 
conclusion at which I have arrived is de- 
cidedly that it is. 
3 a considerable importance, for the cost of 
ose ventilators and apparatus for opening and 
BS ou shutting them forms a serious item in the total 
cost of such buildings. 
Nothing tends more to prove the general prevalence 
of a vague indistinct apprehension of the philosophy 
of ventilation than the various ways in which open- 
ings are made in the sides and roofs of buildings for the 
admission of air. One builder has a system of ridge venti- 
lation consisting of a fixed elevated glazed ridge with flaps 
to open and shut; another has a ridge which can be raised 
and lowered at will; another has flaps along the roof ; 
then there are flaps opening across the roof ; sliding sashes, 
shutters in backs, walls, and openings in the ends of roofs, 
with various other contrivances which I need not enumerate ; 
nor need I dwell upon the form of side ventilators, which 
range from wooden shutters up to costly contrivances for 
heating the air as it enters the house. } 
That plants growing under glass require fresh air all will 
admit, but very diverse opinions exist as to the manner in 
which it should be given them, and it is this of which I 
complain. A matter of such importance ought not to rest 
upon mere opinion, but should be reduced to simplicity by 
the test of cause and effect’; for it is undoubtedly subject 
to the influence of natural laws, and we have only to find 
out what these are in order to arrive at a clear understand- 
ing of what is necessary to be done and how to doit. Let 
us do so. Open the ventilators along the top of a glass 
house, and the interior air, buoyant from warmth, rushes forth 
and is replaced by the fresh air frem without, which may 
instantly be felt as it flows in, spreads to every part of the 
bottom of the building, becomes warm, rises, and escapes. 
We thus have perfect circulation, for the simple reason 
that heated air becomes so buoyant that it rises and the 
vacuum is instantly filled with the cold air which it dis- 
places, proving the truth of the axiom that ‘heat is 
motion,” and affording a capital illustration of the cause 
of wind for youthful students of natural philosophy. 
This buoyancy of heated air enables us also to impart 
motion to the atmosphere of glass houses without opening 
a single ventilator, for by making warm the heating 
apparatus we cause the adjacent air to ascend to the glass 
roof, where it becomes chilled and falls downwards again, 
setting the whole volume of air in motion, so that during 
the prevalence of a cold cutting north-easter our tender 
exotics may be made to enjoy the benefit of warm air 
currents without the slightest exposure to the baneful 
effects of biting frost-laden draughts. To set this fact 
as Clearly as possible before the readers I will tell how 
it first of all arrested my attention. I sat writing on an 
autumnal evening at a table close by a window wide and 
high, so high that it ran from near the floor to the ceiling 
No. 905—VOL. XXXV., NEW SERIES: 
The matter is one of 
of the room, which was unusually lofty. The evening 
grew so cold as darkness crept on that a fire was lit in a 
| grate immediately opposite the window; the door of the 
room was shut, and in a few minutes I became sensible 
of a cold current of air rushing downward upon my head, 
-and which was so violent as to soon set me sneezing. I 
removed to the centre of the room and thus avoided the 
direct draught, which a little thought showed me arcse 
from the air near the fire being warmed and made buoyant. 
It ascended to and along the ceiling, became cooled by 
contact with the upper part of the window, and instantly 
rushed downwards like an actual draught. 
We thus find that by the agency of heat we impart 
motion to the air, and that by opening sashes at the highest 
part of a glass house we get rid of all vitiated air and 
afford the plants the benefit of a perfect circulation of 
fresh air. Such being the case, of what practical value 
are side or front ventilators? Surely in applying them to 
every form of glass house as has hitherto been done we 
have been wrong ; and I submit that it is time this repe- 
tition of a costly blunder should cease. Let us only take 
care to make a large opening from end to end of the top 
of a range, whether it be for the culture of fruit or flowers, 
and the remainder of the building may remain intact. I 
say a large opening advisedly, because I have had repeated 
proof of the evils arising from the narrow openings now so 
prevalent. 
It is unlikely that such a step out of the beaten track 
made hard by time and custom will pass unchallenged ; I 
may therefore add that this is no mere theoretical idea, but 
is a sound and sure deduction from practical experience 
which I commend to the attention of every gardener whose 
undoubted duty and interest it is to reduce the cost of such 
buildings by every means in his power. Horticultural 
builders also will not be slow to introduce an improvement 
that is so much calculated to cheapen, and therefore to 
extend, the building of glass houses—Epwp. Luckuurst. 
NORTH WALLS. 
QueEsTIons are often asked of the Editors concerning 
what will do on north walls, and in our country rambles we 
so often see them unsightly and little used that I think it 
may be good to consider separately what may be done with 
them. First we will take the strictly useful part of the 
question, and look over the catalogue of fruits; then the 
more ornamental may follow ; but it is impossible to keep 
the two entirely separate, for nothing can be more orna- 
mental than fruit trees well stocked with bloom or fruit, 
and nothing can be more useful in such an establishment 
as I have to cater for than a wall covered with flowers fit 
for house decoration. More fruits will flourish in a northern 
aspect than is generally imagined, and in the southern parts 
of the kingdom some of them are better grown in such a 
position than they would be on a south wall. 
The Morello Cherry, of course, stands first on the list, 
but May Duke and most of the early Cherries will do 
exceedingly well. Of Morellos, however, there never seem 
to be too many, and they always fetch a good price. A 
No. 1557,—VOL. LX., OLD SERIES. 
