Lateral Uniformity of Energy Response in the August 1997 ECAL Test Beam Matrix

The lateral uniformity of the energy response is studied using data taken in August 1997. After correcting for a calibration related error, present only in data taken in August and September 1997, the lateral uniformity is found to be excellent. The response as a function of position across the three crystals studied is entirely regular and in agreement with the expected fluctuation in energy containment predicted by shower Monte Carlo. The linearity of response between 50 and 120 GeV is excellent.