In order to grasp an actual dredging capacity of the newly built drag suction dredger Tokushun-maru No.1, a field test was carried out at Kashima Port for a week, Which revealed that a maximum concentration of the mixture could be obtained at the dredging speed of app.3 knots and that an increase in the contact weight of head with the bottom would produce a greater concentration of the mixture for soil conditions at time of this test.
　Comparison of the quantity of solids loaded in the hopper per unit of time enabled us to conclude that pressure water for the preparation of soil to be dredged would have a considerably large effect upon the production.
　The rolling of the ship which affects its suction capacity showed a maximum value two days after a typhoon had passed far off the port. A maximum rolling angle was app.9degress with the period of 8 to 11 seconds, which nearly coincided with the period of waves.