Experiments were made with optical glass K-8 (characteristics not given) at temperatures ranging from room temperature to that of the critical region. Change in stresses was determined from double refraction in the glass. At all temperatures the o changed and tended to reach a definite value for the given temperature.The laws of relaxation of stresses at high and low temperatures differ; it is impossible to indicate a temperature above which some apply and below which others apply; the change from one to another is gradual. The Adams-Williamson equation 1/o - 1/00 = At did not hold strictly at any of the annealing temperatures. For 550o to 530o the drop in o follows approximately this law until o reached 10 to 15 mu/cm. Then the decrease of o occurs much more rapidly than follows from this equation. At high temperatures, o tends to reach zero, and at lower temperatures it tends to reach a definate value depending upon the temperature and the initial o. The rate of change of o was much greater for freshly annealed samples that for those subjected to prolonged annealing.
