78 LIFE OF A TREE. 
luxuriance over the fertile hills and plains of 
South America—-were these all obtained from the 
thin air? Were the particles which unite to 
form our battle-ships, Old England’s walls of 
wood, ever borne the world about, not only on 
wings of air, but actually as air themselves? 
Was the firm table on which I write, the chair 
on which I rest, the solid floor on which I tread, 
and much of the house in which I dwell, once 
in a form which I could not as much as lay 
my finger in, or grasp in my hand? Wonderful 
truth! All this was air. 
In a note at the foot of a former page, we men- 
tioned the composition of the air in general terms. 
We may here re-state it a little more precisely 
thus. After a careful analysis by some of the 
most eminent chemists of the nineteenth century, 
the true composition of the air we breathe is the 
following, — supposing that one hundred cubic 
feet were taken :— 
Oxygen gas ° . ° . 203 
Nitrogen gas : : - ° - 792 
Carbonic Acid gas : : : Pe se 
Carburetted Hydrogen gas i * 
Watery Vapour—vuriable. 
Vapour of Ammonia—traces. 
