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"Suppose a b c to represent a portion of the earth's surface a being towards the north pole, c towards the south pole...The currents of air are supposed to pass in the direction of the arrows. the wind, therefore, for a to b would blow on the surface of the earth, from north to south, while from e to a, the upper current would pass from south to north, untl it came to a, when it would change is direction towards the south." -Comstock 1850

Opposite Currents of Air

"Suppose a b c to represent a portion of the earth's surface a being towards the north pole, c towards…

"Perfiolate leaf, caused by the union of two opposite leaves."—Darby, 1855

Perfiolate Leaf

"Perfiolate leaf, caused by the union of two opposite leaves."—Darby, 1855

"...represents two wave systems of equal periods and amplitudes but of opposite phases." -Avery 1895

Waves with Equal Periods and Opposite Amplitudes

"...represents two wave systems of equal periods and amplitudes but of opposite phases." -Avery 1895

"...represents two such wave systems meeting in opposite phases." -Avery 1895

Waves with Opposite Phases

"...represents two such wave systems meeting in opposite phases." -Avery 1895