TIME cannot be measured as any other physical magnitude is measured. Measurement is the determination of the number of ‘units’ contained pin the assigned quantity, and the unit is defined either (as with mass and space) as an arbitrarily; chosen, permanently preserved piece of the magnitude in question, or (as with temperature, electric tcharge, etc.) as that which produces a specified amount of an arbitrarily chosen effect ultimately measurable in terms of mass or space. But it is impossible to preserve a standard second, and time produces no effects—events occur in it but not because of it. Consequently measurement of time must be a special process.