1 Jury, 1902.] QUEENSLAND AGRICULTURAL JOURNAL. 51 
neither see nor hear it at work. Butitis a fact, and I may further state that this 
same agent would even reduce a rock of iron to powder in time, and, as a proof of 
this, I might refer to what is too commonly seen on many of our farms—that is, a 
bright plough left outin the open field. If left there for two or three days and nights, 
what do we see? The silvery bright work is turned into a red rust. When this rust 
is dry you may brush it eff in dust; this dust is known as oxide of iron, commonly 
ealled iron rust. ‘This, too, is the powerful work of this oxygen gas on the iron of the 
plough. 
: Let us suppose for a moment thatthe proportions of these two gases were reversed, 
and we had only one-fifth of nitrogen and four-fifths of oxygen. We should find that 
the bright plough referred to would be reduced to powder in one night, and the whole 
face of what we call Nature would be changed into a barren wilderness, for no plant 
or animal could possibly live on the earth. oes 
Itis a Nese fact that, if a piece of iron were to be placed in a vessel con- 
taining pure oxygen gas, it would be reduced to oxide of iron ina few seconds; thus 
showing that even a rock of iron could not resist the disintegrating power of this 
oxygen gas. 
We see, then, the gases of the atmosphere have been wisely blended for the 
roduction of the greatest amount of good to both vegetable and animal life with the 
east amount of evil. 
But it may be asked: How does this gas affect the plants and the soil? ‘To this 
I reply that oxygen gas is one of those fluids which carry food to plants through 
their leaves, for it is well known that plants feed largely through their leaves as well 
as through their roots. But this gas not only carries food of an organic nature to the 
plant through its leaves, but it is also a powerful agent, if permitted to enter the soil, 
in providing food of an inorganic nature to be taken in by the roots of plants, for all 
food of an organic nature required by plants is supplied from the atmosphere through 
their leaves, but foods of an inorganic nature are taken in by plants through their 
roots in a liquid state. But if our lands have a hard and weedy surface, and are not 
drained, then I say it is impossible for this or any other gas to penetrate the soil 
and assist the farmer. 
I must now leave this gas for the present, though much more of an interesting 
nature might be said in reference to it; but I must pay some attention to the other 
gases referred to as being components of the atmosphere, and the next I will refer to 
is that known as carbonic acid gas. ‘This gas is a close companion of the last-named 
oxygen, and is present in the air in the very small proportion of about 1 in 2,000 
parts. In itself it is a deadly poison to animal life, and is also the heaviest gas in the 
whole air, and were it not for a very wise law which is always at work in and around 
us, called the law of diffusion, no animal would be able to live close to the earth, 
because this gas, being, as I said, the heaviest and so very poisonous, would always 
be nearest the earth’s surface, and would thus prove fatal to animal life. 
But, while this gas is so injurious to man and other animals, it is one of the most 
invigorating of organic foods for plants in the form of gas. It is also worth 
of note that, while plants are continually absorbing this carbonic acid gas, itis 
continually being ejected from their bodies by the whole animal creation, man included, 
thus keeping up a constant supply for plant food and life. This gas is not only an 
organic plant food when taken in through their leaves in a free state, but is also, like 
its companion oxygen, a powerful agent when permitted to enter the soil, as it enters 
into a combination with other substances and assists in the disintegration of the soil, 
setting at liberty fresh supplies of food to be dissolved in water and taken up by the 
roots of plants. The next component of the atmosphere is ammonia, commonly called 
hartshorn, and is composed of two others—viz., nitrogen and hydrogen in combination— 
and is easily known by its strong pungent smell. Ammonia in its free state is, like 
carbonie acid, a plant food, and is taken in through the leaves of plants. This gas 
also, if permitted, enters the soil andassists in reducing the insoluble portions of the 
~ earth to a soluble condition to be taken up by the roots of plants. I am afraid that 
your patience will not allow me to more than just name the two other components of 
the air—viz., nitric acid and watery vapour. ; 
It is supposed that this nitric acid, which exists in very small quantities, but yet 
in sufficient quantity to supply the crops on our lands with very valuable plant food, 
is formed by the combination of two other gases, and which I have before named— 
oxygen and nitrogen. ‘This combination produces lightning, and the acid thus 
formed is dissolved by rain, and so comes down to our plants. It is this acid that 
gives to our crops such a healthy appearance after thunder showers. I shall now 
very briefly refer to the lastnamed of the components of the atmosphere—watery vapour 
—which is simply water in the form of steam, and is produced by the rays of the sun 
drawing up water from the seas, rivers, and lakes, and, by the law before referred to— 
viz., diffusion of gases —is distributed through the whole atmosphere. This vapour has 
