The author measured various angles on the surface of penetration obtained by rapid hammer blow exerted upon the mother plate in the course of welding in flat position for various welding conditions with five kinds of covered mild steel arc welding electrodes, and discussed on the relation between the contact angle of mother drop covered with various slags and weld bead configurations. Results obtained were as follows.(1) The angle of solidification θs' angle between the extension of bead surface and the solidifying surface of weld bead, is almost a constant value along the total length of the solidifying line except at both ends.(2) Angle of solidification at the mid-point between the end and the center of the solidifying line is almost the same under various currents. 9s, mean value of 0s, seems to be nearly the same as the contact angle θo characteristic to the kind of welding electrode.(3) The order of wetting property of mother drops from various electrodes, which is presumed from the angle of solidification against the solidifying surface in manual welding or in submerged arc welding using slags of the same coated electrode, roughly coincides with what presumed from the shapes of alcoholic water drops of various concentrations placed within the actual surface of penetration coated by paraffin. And the order is the same as the one of JIS code number.(4) The ratio of height to width of bead in various welding electrodes increases according to the JIS code number, except D 4320.(5) The effect of up-and down-hill welding or of welding speed on the shape of penetration and weld bead can explanined by means of the changes of direct and indirect digging action of welding arc.