8 
POPULAR SCIENCE REVIEW. 
remaining in an unchanged condition in the air; but the 
oxygen is ever being consumed and renewed. By its union 
with carbon, and other elements of the animal body, it main- 
tains life. Just as it unites with the coals of the fire or the 
carbon of the gas and gives out heat, so it unites with the 
carbon of animal bodies and heats them, and they live. The 
result of their life is carbonic acid, which would poison the 
animal and the air in which it lives, were it not for the agency 
of the vegetable kingdom. That which is death to animals is 
life to plants. The carbonic acid enters the plant as a com- 
pound of carbon and oxygen ; but each cell of the plant is a 
chemical laboratory, where invisible forces are busily at work, 
separating and depositing the carbon as future store of 
food for man and beast, and the oxygen is set free. The 
oxygen is thus restored to its home in the air once more, 
again to be conquered by carbon, and once more to be set 
free from its prison in the plant-cell, when touched by a ray 
of light from the sun. But not as it enters the lungs of man 
or animal does oxygen come forth from the plant. It has 
acquired new powers, and, like a giant refreshed, is more 
capable of action than before its repose. It has now become 
ozone. It is still oxygen, but oxygen capable of oxidizing 
more powerfully, of acting more vigorously than it does as it 
ordinarily exists in the atmosphere. Ozone is soon lost in the 
great ocean of air into which it is thrown, by its own activity. 
It is found on mountain heights, it is found by the sea-shore, 
and on the sea ; but it is consumed by cities, by cultivated 
land, by forests, and by all agencies which call its vigorous 
action into existence. But wherever it is found, it acts 
favourably on the human body. The instincts of the denizens 
of cities and valleys have drawn them to mountain heights 
and sea-shores ; and the annual migrations of families to our 
hills and sea-sides have excited the ridicule or the reflection of 
those who have never attempted to solve its real cause. The 
air of mountains and sea-sides is doubly fresh air : it is not 
only pure, but ozonized, which accounts for its curative and 
exhilarating action on the human body. It is interesting to 
know that this universal instinct of benefit to be derived from 
residence in these positions has been confirmed hy elaborate 
physiological experiments on the human body. It is now known 
as a fact, that those actions of the body which are essential to 
healthy life are carried on more vigorously in an atmosphere 
containing ozone. The great practical lesson taught by this 
knowledge is, the importance of securing as often as possible 
change from an unozonized to an ozonized atmosphere; and it 
I- < ^penally important to those whose opportunities are limited, 
that when they are at the sea-side, they should exclude, no 
