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454 QUEENSLAND AGRICULTURAL JOURNAL. [L Noy., 1901. 
for mixing with sand to make the mortar. But the lime, as it lies there, would. 
not be of the slightest help to the mortar unless something were done to it. 
It is “dormant,” and must be waked up. So the bricklayer throws buckets of 
cold water on it, and it immediately begins to get hot and to splutter and hiss. 
and crumble to powder. Now the lime is ready to do its share in 
making the mortar. Now, just as the water acts upon the lime, so do 
certain gases act upon the dormant elements in the soil. They start them into. 
life, and so alter them that they can easily be taken in by the little mouths of 
the plant roots. 
Questions on Lesson 2. 
1. How do plants take up solid food ? 
2. By what experiment can it be shown that invisible solids may be 
contained in water ? 
. What is the difference between a “ melted” and a “ dissolved” substance ? 
Of what is the smoke of a fire composed ? 
What becomes of it ? 
What invisible body is produced by the burning of a substance P 
What becomes of this body ? 
How do plants absorb it ? 
. What does the word “ vegetable” mean ? 
How do trees render a place healthy ? 
. How is soil produced ? 
. Do rocks contain plant food ? 
. What are “ dormant” ingredients ? 
. How do they become active ? 
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BWNH ODS ONDA & 
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Ps 
3rd Lesson. 
SECOND STAGE. 
I shall not say anything about the manner in which plants originally 
came upon the earth, first, because it would not be understood by you, and, 
secondly, because neither I, nor anybody else, know how the first seeds got 
into the soil or on to the rocks. But the plants came there, and we have been 
making them better every year, by learning how to improve the soil, and b 
cultivation. Now that we have arrived thus far in the consideration of the 
soil, I shall have to give you a few hard words to recollect. Yet they are not 
very hard nor difficult to pronounce. The first word is oxyGEN. Oxygen is a 
gas contained in the air, and it is very important to us as well as to soils 
and plants, for without it we could not live. But although you know that 
mince pies are nice, too much mince pie is very bad for you. So, too much 
oxygen would be bad for us; consequently it is mixed with another gas called 
niTroGEN. This nitrogen serves the oxygen in the same way that hot water 
serves strong tea—it makes it weaker, and as these two gases are mixed in. a 
certain proportion, we receive just as much oxygen as is required to sustain 
life, and no more. You will perhaps think, ‘ What has this to do with the 
soil?” Wait a little, and you will see that I could not explain the formation 
of the soil to you until you had first learned the composition of the air. Now, 
I have one more hard word for you, and that is CARBONIC ACID GAS. Whence 
does this get into the air? ‘Take a piece of wood and burn it slowly, keeping 
it as much out of the air as possible. The wood burns, and after a certain 
time appears in the form of a lump of charcoal. Now this charcoal may be 
called a piece of carbon. (You learned this word in Lesson 2.) It is made in 
great quantities by men called charcoal-burners. They make great piles of 
wood and cover them first with grass, then with sods, and set them on fire. 
They watch these piles night and day, and whenever the fire breaks out, they 
put fresh sods on to exclude the air. Ina few days, the fire has burnt itself 
out, and there remains a pile of black, brittle charcoal or carbon. Now, sup- 
pose the fire had been allowed to burn furiously in the air, all this charcoal or 
