1846 
THE CULTIVATOR. 
267 
but good farmers so manage it that the heat shall 
not exceed from 80 to 90 degrees. The farmer also 
wants his dung to decompose mildly and quietly. But 
what would take place, if, instead of keeping the dung 
pressed down, he was to separate it, and let the air 
come in? Practical men will tell you that the heat 
would be largely increased; instances, indeed have been 
known of such heaps taking fire. In fact, if these dung- 
heaps are not properly attended to, they will readily 
take fire. You see, from this, that oxygen has a deal to 
do with manure; for it is by this substance that the 
farmer gets his heaps diminished in bulk. He gets the 
most worthless portion taken away; that which is left 
is more easily carted and more valuable. You see, 
therefore, what an active agent oxygen is. It acts, too, 
upon all metals exposed to the air. If you take a knife 
or a spade, and expose it to the action of the air all 
night, you will^find it next morning of a red color. 
And what is’this red substance? It is a compound of 
oxygen and iron, called the oxide of iron. 
There are many other combinations which spontane¬ 
ously take lire and give out heat from the absorption of 
oxygen. Iron pyrites, a compound of sulphur and iron, 
is found in large quantities throughout the globe. It is 
veiy bright and metallic, looking something like gold 
When exposed to air and moisture, oxygen is absorbed, 
which, uniting with the sulphur, forms sulphuric acid, 
and with the iron, oxide of iron. These two again 
unite, and form the sulphate of iron, or common green 
vitriol. As oxygen is absorbed by the pyrites, you are 
also sure that heat is produced. In the manufacturing 
districts, where sulphate of iron is largely made from 
pyrites, care is taken not to allow it to get over-heated: 
and if it should get too hot, water is thrown upon it. 
Bishop Watson, the celebrated chemist, tells a curious 
thing in his chemical essays. A man at Ellantl, in 
Yorkshire, collected a quantity of the pyrites, under the > 
idea that it was gold, and put it into his barn in a heap. 
The barn, as was common enough in those days, was 
made of wood, and moreover the roof was a little 
leaky, and by this means rain was introduced. This 
generated a heat, and in the course of a few weeks, the 
heap took fire, and burned down the barn. You see, 
therefore, how important it is that such things should 
be borne in mind. 
There is another thing very closely related to what I 
have mentioned. Any of you who have been in the 
north of England, must have seen all round the great 
coal-pits of, Newcastle, Durham, and other places, large 
heaps of small coals, covering many acres. These coals 
have been deposited there owing to their small value; 
and you will find that they are always on fire. Per¬ 
haps you will imagine that the coals were set on fire? 
No such thing; they took fire by themselves. When I 
state to you that the coal contains sulphuret of iron 
(iron pyrites,) you will be at no loss to ascertain the 
cause. The action of oxgen on the sulphuret of iron is 
such as to produce heat, and the continued action of 
this heat causes the coal to take fire. Many singular 
phenomena of which-we occasionally hear, as, for in¬ 
stance, smoking and burning cliffs, near the sea, are 
due to the action of oxygen on recently exposed iron 
pyrites. 
But more still. This oxygen, this universally-acting 
busybody, has something to do with volcanoes and 
earthquakes. We find that these volcanoes burst out 
with tremendous force in some places, emitting large 
bodies of fire. Whence does this arise? This fire is 
doubtless the product of combustion. And what an 
enormous power must be generated to produce such 
awful results as the overthrowing of Herculaneum and 
Pompeii, the awful visitation of Calabria, or the de¬ 
struction of the city of Lisbon. 
In connection with Volcanoes it should be borne in 
mind that they are always near the sea. You know 
that when you look for their positions on the map, you 
keep your eye to the coast. Etna, Hecla, Vesuvius, 
Stromboli, the burning mountains of the Andes, and 
the volcanoes in the East Indies, are all to be found 
near the coast. There can be no doubt that water has 
something to do with them; and water, recollect, con¬ 
tains a great deal of oxygen. 
It has been supposed that the matter of the interior 
of the globe consists chiefly of the metallic bases of the 
earths; and these, it is well known, have the power to 
decompose water, uniting with its oxygen and libera¬ 
ting the hydrogen. 
Now, if by any means the ocean water penetrates to 
these metallic bodies, most intense action will be the 
result; heat will be liberated, and effects produced quite 
sufficient to account for the phenomena of volcanoes and 
earthquakes. 
There are a few other points which I wish to bring 
before you. This oxygen is the agent appointed for the 
destruction of all vegetable and animal substances. 
Every one of us is undergoing its action. We breathe 
it, but we return less of it to the air than we took from 
it. What we inhale produces heat, and this is the rea¬ 
son why your bodies are warmer than the stone walls 
around you. Without *any very great stretch of the 
imagination, or any very forced comparison, your 
bodies may be likened to little steam-engines, or black¬ 
smith’s fires. Your lungs operate as a pair of bellows, 
your mouth is the chimney, and the food is the coal. 
Your bellows are always going; if you are prevented 
from breathing for two minutes you will die. Yet, if 
it were not for the action of the oxygen on your body, 
j you could not live; for from its continual consumption 
of the muscles of the body, you derive your physical 
energy and power. If you did not eat what would be 
the consequence? Would the bellows cease to work? 
No; they would go on working till every particle of 
available fuel, (flesh, fat, &c.,) was consumed. This 
shows that if you take no food to supply the waste of 
the muscles, you must, like a fire, ultimately go out. If 
j food be withheld the parts of your body, such as the fat, 
the muscles of the cheeks, of the breast, and all other 
available parts, would be consumed by the action of the 
inspired air, before the bellows would cease to work; 
and, lastly, the brain would be attacked, and you would 
die. Now, this always takes place when, by any means, 
food is not taken, or not properly digested. On the 
other hand, if the blacksmith overloads his fire, and 
does not blow his bellows enough, the flame goes out; 
and you, if you are always eating and never blowing 
your bellows enough, you are still liable to go out. 
You are putting on too many coals, and that is the 
reason why I recommend you to.enjoy yourselves at 
play, without which you can never expect to grow 
strong. Our life, and the life of all animals, therefore, 
depend on the action of oxygen and the supply of food. 
When these two are in a state of equilibrium or balance, 
we are in a state of health. When either one or 
the other are in excess, our normal state of health 
ceases, and various maladies ensue, which continue 
until the cause is removed. Eventually, however, the 
oxygen obtains the mastery, and these bodies of ours, 
like those of our ancestors, will be overcome by this 
powerful agent, and their elements will be returned 
into the great laboratory of nature, to furnish the prin¬ 
ciples of life and existence to succeeding generations of 
animated beings. 
All vegetable matters undergo a similar change, and 
they also are eventually decomposed, to furnish again 
the elements of vegetable life. 
All animal and vegetable substances, therefore, unless 
preserved in some peculiar manner, are resolved into 
their original elements. But if protected from the ac¬ 
tion of oxygen, they may be preserved for an indefinite 
period of time. Wood is painted to preserve it from 
contact with the oxygen of the air, and it thus lasts 
much longer. Again, coal is the remains of immense 
forests of primeval periods, and it has not yet been de¬ 
composed into its elements. These immense deposits 
of vegetable matter were, when deposited, covered with 
soft mud, so that the oxygen was prevented from 
coming in contact with them, and by the constantly in¬ 
creasing pressure from superincumbent deposits, the 
mud became a rock, and the action of the oxygen be¬ 
came less and less for each succeeding year. The con 
