NEW MODE OF VENTILATION. 
Ill 
NEW MODE OF VENTILATION. 
The discovery, in England, of a new principle 
of ventilation, the truth of which seems estab- 
lished beyond question, will furnish an impor- 
tant desideratum in greenhouse management. 
It has been ascertained that air, like water, 
can be made to circulate through a syphon, but 
inversely with the latter fluid. That, whereas, 
water will enter a syphon by the shorter arm, 
and discharge itself by the longer, air on the 
contrary, will always enter by the longer arm 
and discharge itself by the shorter. Thus, if a 
stove-pipe elbow be inserted in the chimney, 
with one of its orifices facing the ceiling, a sy- 
phon will be formed of which the chimney will 
be the longer arm. The air will rush into the 
shorter arm of the stove pipe, and discharge 
itself by the longer arm of the chimney, with- 
out the necessity of a fire in the chimney, to 
cause a draught, which is often required where 
there is simply a hole in the chimney for ven- 
tilation. 
One great advantage of this principle, as we 
understand it, is, that there is no inward current 
of cold air from the outside — that the syphon 
can only work in one direction. Thus, when 
there is no chimney, two stove-pipe elbows 
united can be inserted in a sash pane, with the 
shorter elbow in the room. The current of air 
will set strongl} r from the room, and a person 
may sit immediately under the pipe without 
danger from the descent of the cold air upon 
him, which always takes place when a sash is 
lowered. 
This principle is of no slight importance in 
its application to greenhouses. Every gardener 
knows the importance of getting rid of the bad 
air in his houses, and also knows the difficulty 
of doing so without having his plants cut, to use 
a technical term, by the cold air rushing in 
upon them. Now this discovery remedies the 
difficulty at once. All he requires, is a suffi- 
cient number of these stove-pipe elbows intro- 
duced, either into the back wall or roof, with 
means of closing them at pleasure, and he can, 
in the most extreme weather, thoroughly ven- 
tilate the house, without the least injury to his 
plants, from the cold. 
Many of the inventions of the present day 
seem to be less the novel application of old 
principles, than the discovery of entirely new 
principles in natural science. Such is the case 
both with Polmaise heating, and with the pres- 
ent invention, and with the progressive tenden- 
cies of the age — still more important results may 
be anticipated from the exertion of mental 
inquiry in this direction. 
QUALITIES OF LIME. AND ITS COMPARATIVE 
VALUE FOR AGRICULTURAL PURPOSES. 
The questions are frequently asked, which is 
most useful for the field, oyster-shell or mineral 
lime ? Is not magnesian lime always injurious ? 
Is lime or marl the best fertiliser? Numerous 
other and somewhat similar inquiries are con- 
stantlj- made by farmers, most of which would 
be easily resolved by their own minds, did they 
possess a tolerable knowledge of the leading 
principles of lime, marl, magnesia, and their 
application. An entire volume might be appro- 
priately occupied with the consideration of these 
important fertilisers, but we must content our- 
selves with the occupancy of a page or two 
only. 
Lime (carbonate of lime) constitutes almost 
the entire portion of limestone, marble, chalk, 
oyster shells, and others of marine or fresh 
water origin; and marls seldom contain less 
than 20, and frequently as high as 70 or 80 per 
cent, of carbonate of lime. It is a compound 
substance, made up of two 'proximate principles, 
carbonic acid and lime, in the proportions of 
46 acid, and 54 lime. Each of the above con- 
tain two distinct principles termed ultimate, 
because we do not know that they can be de- 
composed or separated. 
Quicklime is the condition in which lime is 
left after burning limestone, chalk, or marl, 
which expels the carbonic acid. It is composed 
of oxygen (a gas) about 28.6, and calcium, 
(a metal,) 71.4, in every 100 parts. Carbonic 
acid is made up of oxygen, about 72. 4, and car- 
bon, 27.6, in every 100 parts. The metal has 
the same peculiarity when exposed to air, as 
potassium, the base of potash, when exposed to 
water. It takes fire and burns with great inten- 
sity until saturated with oxygen, when the 
above proportions are again re-established. So 
much for these compounds, the knowledge of 
which will not be unimportant to the thinking 
agriculturist, in tracing their various changes 
and application. Nor are other characteristics 
less so. 
If quicklime is exposed to the air, it rapidly ab- 
sorbs about one third its weight of vapor; or if 
water is thrown upon it, this instantly combines 
with the lime, until it reaches the point of sat- 
uration. This compound is called the hydrate 
of lime, and is the condition in which freshly- 
applied lime exists in the soil, when spread and 
incorporated with it. After a time, however, it 
gradually combines with carbonic acid, forming 
an imperfect carbonate ; and it is the alternate 
absorption of carbonic acid and other gases, 
and their relinquishment to the demands of 
growing vegetation, which, in the yet unsolved 
mysteries of agricultural chemistry, is deemed 
one of the most beneficial results of the action 
of lime. 
Lime is a direct food to plants, constituting a 
part of the ash of all; but it is found in much 
greater proportions in some than in others. 1,000 
lbs. of dry pea straw, sainfoin, red and white 
clover, each contain from 20 to 30 lbs. of lime, 
while lucern has nearly 50 lbs. Every other 
cultivated plant requires a considerable quantity 
of lime to mature and perfect it. But in addition 
to this, and its aid in bringing the gases (the 
organic portions) to vegetables, it greatly facil- 
itates and disposes those chemical changes in 
the inorganic or earthy parts of soil, which are 
so essential to furnishing the plants with all 
they may require. 
Lime serves the furllier purpose of altering and 
improving the mechanical texture of soils. Its 
greater density and weight induce its settling 
