Dan, If may be worthwhile to wait for rainwater to fall, make CS, then add to tapwater. Current limitation could be achieved with a rheostat. A rheostat resistance equal to the (initial) resistance between the silver electrodes would provide appropriate current limitation. An ohmmeter and resistor is not necessary. Just replicate the inter-electrode resistance with another cell like the first, except that it uses non-silver electrodes - copper coins might do.
Matthew
