Willie was a fine rosy-faced boy of our southern colony. Though not
eight years of age, he was as healthy and merry a lad as ever climbed
up a Gum tree, picked up manna, or rode in a bullock dray.
His father had once occupied a good position in Old England; but
the uncertainties and losses of business, and the constant struggle
to uphold a respectable appearance with decreasing means, became so
burdensome to his mind, that his spirits failed, and his energies sunk.
His attention was directed to Australia, the land of mutton and corn,
the home of health and plenty. Gathering up the wreck of the past, he
left the country of taxation and paupers, and established himself on a
small farm in Port Phillip.
The young hero of our story had been a year or two in the colony. It
so happened he had a piece of land of his own, in which he proudly
exhibited some rising cabbages, a few peas, and a flower or two. His
father had given him a rose tree, which was the reigning beauty of the
bed. It was upon the occasion of his parent’s visit to the garden, that
the following dialogue took place:--
Look, father, and see how my rose tree has grown.
Indeed it has, Willie. Can you tell me what has made it grow?
The sun and the rain, I suppose.
Do you remember, when we got tired of the old slab hut, and set about
building this brick cottage, that you noticed it getting higher and
higher every day!
Yes, that was because more bricks and wood were used.
Then, if your tree increases in size, there surely must be something
added on continually: do you think the sun and rain do this?
Well, I never thought about it, father; but I should like to know why
it does grow.
Can you tell me, Willie, what a plum pudding is made of?
Yes, that I can. There is the flour, the suet, the raisins, and the
cold water. All these are mixed together.
Then let us see of what our rose tree is made.
I don’t think it so easy to tell that as to reckon up the articles in a
pudding.
Never mind, we will try. First, there is the stalk, or woody part.
When you put a piece of stick in the fire, what becomes of it?
Oh, it smokes and blazes, and then nothing is left but some ashes.
What is it which burns away?
That I cannot tell.
It is the gaseous part which burns in a flame, like what you have seen
come out of coal. But what do you call woody matter that will not blaze?
Charcoal, father. Then I understand now that wood is nothing but
charcoal and the gases. What are these gases?
The gas which blazes so readily, my dear, is hydrogen: and it has
a very strong smell too. The air we breathe is a mixture of two
gases--oxygen and nitrogen. It is only the oxygen that we take into our
lungs.
Well, that is curious.
I shall puzzle you more, Willie, when I tell you that water is nothing
but a mixture of oxygen gas and hydrogen gas.
It certainly is funny that water, which puts out flame, should be
partly composed of the burning gas.
You must also know, my lad, that hydrogen would not burn without
oxygen. You blow air into a fire to give food for flame.
But however could the plants get hold of the gases, father?
Did it never strike you why God formed leaves?
It never did, except that I thought he did it to make the trees look
pretty.
That is quite true, Willie. The good God loves beauty, and he has
surrounded us with beauty of all kinds. But he made things for use as
well as to be looked at. The leaves absorb or suck in gases from air
and water.
Then I suppose the veins like that we see in leaves conduct these gases
away into the plant.
Quite right, my boy. Where now shall we get the charcoal, or carbon, as
the learned men call it?
That I cannot find out at all.
You told me, Willie, that smoke came out of burning wood. What becomes
of it?
When I was a very little boy, I thought it went up to form clouds; but
now I know part of it turns into soot in the chimney, and that looks
like our charcoal or carbon.
It really is. As to that which comes out of the chimney, it passes
upward, and gets gradually mixed with the air. The little particles of
carbon join the oxygen, and become a sort of gas called carbonic acid
gas, which is absorbed into the plant.
How wonderful that the solid part of a tree should once have been
floating about in the air!
Do you think the leaves of a plant to be the same as the stem?
Yes, I do; for when they are thrown in a fire, they smoke, blaze, and
leave an ash like the wood does.
Just so. You know the smoke to be carbon passing into the air; but we
must examine the ash a little more carefully. If you take some ash from
the fireplace, and put it into hot water, the solid part will of course
fall to the bottom.
Will no part mix with the water?
There will be something; for if we pour off the water, and allow it to
evaporate in a dish, there will be found to be a sediment left, and
that is potash or pearl ash.
I have heard of people in the bush doing that when they could not get
soap, for they said that the potash got the dirt out of clothes.
It is a great pity that we in these colonies burn away so much wood in
waste when clearing land, Willie, without thinking of making potash out
of the ashes, for it fetches a good price.
Then there is potash in the plant. Has any thing else been found in the
ash beside that and carbon?
Yes, my lad. Sulphur or brimstone, lime, soda, flint, ammonia,
phosphorus, magnesia, and iron, are contained in trees.
But how could all these things get there?
Why, if we cannot find them in the air to be absorbed by the leaves,
they must be in the soil or ground. Now, it so happens that those
substances are to be found in different quantities in different places.
How do they get into the plant, father?
Simply by the little rootlets absorbing small particles of them, mixed
with moisture.
But do all plants require the same amount of lime, potash, soda, and
the others?
No, my dear. There are not two sorts of trees that feed upon the same
materials in exactly the same proportions.
Is that the reason, then, why some land is so much better fitted to
grow one plant than another?
The reason is, because the one soil has more of the right sort of food
in it.
Now I see that if I wanted to grow a good crop of any thing, I must
give it plenty of the food it likes best.
Yes, but not too much. For like as too much nice rich food is bad for
children, so it is with vegetables: ground may be too rich, as well as
too poor.
I have heard people say that it is not wise to grow the same thing in
the same soil year after year: why is this?
Because it would gradually consume all the food there, and then it
would starve, and look miserable.
Then my beautiful flower-bed will by-and-by cease to bring forth such a
fine show as it has done this season.
Of course it will, unless you provide your plants with fresh food.
Fresh food, father; I do not understand you.