Sentence:  If a is the major axis of an ellipsoid and b and c are the other two axes , the radius of curvature in the ab plane at the end of the axis is * * f , and the difference in <WSD>pressure</WSD> along the a and b axes is * * f . 
Meaning of the word marked with <WSD> tags:  the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)