Electrochemical Scanning TUnneling Microscopy (ECSTM) has been extended to characterizc polycrystalline silver electrode surfaces in iodide solution. Potential-dependcnt ordered and disordered structures of the silver electrode as well as the iodine adsorption layer have been obscrved to coexist on polycrystalline silver electrode surfaces, for the first time. A very special column arrangement of the iodine adsorption layer, similar to the so called "ndssing row" type of structure has been obseryed. Some columns of the iodine adsorption layer roll over from one place to another along with the time and changing potential. A proposed model has been given to better describe the structure. The highly corrugated and loose surface structure of the polycrystalline surface are responsible for this special phenomenon.
