Experiments of one-point cold fusion have been performed by electrical discharging in ordinary and heavy water mixed with 0.6 mol/ℓ potassium carbonate. A platinum pin anode was located perpendicular to a copperplate cathode. After discharge, the surfaces of the copperplates were examined by an optical microscope. Many ring spots caused by gravity decay of single and di-neutrons were separately distributed on the plates. Furthermore, several kinds of traces that might be produced by itonic hydrogen clusters and by tiny black and white holes were observed. The mechanisms of cold fusion by electrical discharge are also discussed in terms of the Nattoh model.