“…The apparatus for this search, shown schematically in Fig. 1, consisted of the Lee et al [23] apparatus we used previously, augmented (a) by a device, called a neutralizer, [24,25] that brings the average drop charge to zero and (b) by increased automatic computer control of the drop trajectories. The piezoelectrically driven, drop-on-demand drop generator [26] produced 0.833 drops per second with an average drop diameter of 26:5 m and a short term (one hour) diameter spread of 0:016 m (0.06%).…”