(plur. OASES), a fertile spot in the midst of a sandy desert. In the Sahara, or Great Desert of Africa, there are many Oases of extreme fertility.

OBLATE, flattened or shortened; as an oblate spheroid, having its axis shorter than its middle diameter; being formed by the rotation of an ellipse about the shorter axis.

OBLIQUE ASCENSION, is that point of the equinoctial which rises with the centre of the sun, or star, or any other point of the heavens, in an oblique sphere.