368 WISCONSIN STATE AGRICULTURAL SOCIETY . 
. the one taken from the mountain summit, the other from the 
ocean level. 
The enormous quantity of nitrogen serves but to dilute the oxy¬ 
gen, adapting it to the delicate tissues of the lungs of animals and 
to the purposes of combustion. Were the atmosphere pure oxy¬ 
gen, no fire once lighted could be extinguished, and iron would 
burn freelv as wood now does in common air. 
Besides these, there are substances accidently present in the atmos¬ 
phere, especially near the ground, which in the form of gaseous 
miasmatic contagion, exercise a noxious influence on animal or¬ 
ganization. Infusoria and minute particles of mineral and veget¬ 
able substances are also held in suspension in the atmosphere. 
This vast aerial ocean is never at rest. It has its gulf streams, its 
aerial currents, real air rivers, and is ever rolling its restless tides 
from the sea to the land, and from the land back over the waters. 
The upper and lower strata usually move in opposite directions. 
Aerial storms usually move in vast circles with a diameter of 
from two to five hundred miles, one arc upon the land and anoth¬ 
er on the sea, rushing always from right to left. The reason that 
carbonic acid gas accumulates, not to a dangerous amount during 
the winter sleep of vegetation, is thus accounted for. Currents of 
warm air, rich in oxygen, roll in from the tropics for the supply 
of the breathing animals of the higher zones, whilst opposite cur¬ 
rents of cold air, dense with an accumulation of carbonic acid run 
steadily from all wintry climes, bearing an exhaustless supply of 
carbonaceous food for the luxurious and ever growing vegetable 
organism of equatorial lands. 
This atmospheric envelope, like a huge sponge, rarified by heat, 
absorbs water in enormous quantities from oceans and lakes, then 
bearing these watery treasures over continents and mountains, un¬ 
der the condensing power of cold, pours them out in rain, snow 
and hail, dew and vapor, on the plains and mountain sides. The 
heated atmosphere of summer holds a much larger quantity of 
watery vapor than the condensed air of winter, yet it is in the cold 
months of the year that the moisture of the atmosphere is the 
greatest. 
The air is far from being colorless, for we are really looking 
into its azure depths, when we are admiring the blue canopy we 
