ABSTRACT
Usually the straight line through the early portion of the laboratory curve intersects the zero time line at a point (R
o ) differing somewhat from the initial point (R). This intersection point is
called the corrected zero point. If one-ninth of the vertical distance between the corrected zero point and the 90 per cent point is set off below the 90 percent point, the point obtained is called the "100 percent primary compression point" (R IOO ). The compression between zero and 100 per cent point is called "primary compression".
